# £ P. 2 j , m. —' , —«

k 

# -x - 

# izt EP A 600/ 8 7 7 01

7 Decembe r197

7 Specia l Serie s



# Ai rQuality 

# Criteriafo

r WDEJ I

Offic e o f Researc h an d Developmen t " U.S . Environmenta l Protectio n Agenc y ; 

### -egg ?

Washington , D.C . 2046 0 'T^ TP. 3



## RESEARC H REPORTIN GSERIE S Researc hreport s o f

th e Offic e o f

Researc han dDevelopment , U.S . Environmenta l Protectio n Agenc y hav e bee n groupe dint o series . Thes e broa dcategorie s wer e establishe dt o facilitat e furthe r developmen t

an dapplicatio n o f

environmenta l technology . Eliminatio n o f traditiona l groupin g wa s consciousl y planne dt o foste r technolog y transfe r

an damaximu minterfac e i n relate dfields . Thes e serie s are :

1 . Environmenta l Healt hEffect s Researc h 2 . Environmenta l Protectio n Technolog y 3 . Ecologica l Researc h 4 . Environmenta l Monitorin g 5 . Socioeconomi c Environmenta l Studie s 6 . Scientifi c an dTechnica l Assessmen t Report s (STAR ) 7 . Interagenc y Energy-Environmenta l Researc han dDevelopmen t 8 . "Special " Report s 9 . Miscellaneou s Report s Thi s repor t

ha s bee n assigne dt o th e SPECIA Lseries . Ai r qualit y criteri adocument s ar e issued , a s mandate db y th e Clea n Ai r Act , t o provid e th e basi s fo r decision s b y th e Administrator , EPA , regardin g th e nee dfo r nationa l ambien t

ai r qualit y standards . 

## EP A REVIE WNOTIC E Thi s repor t

ha s bee n reviewe db y th e Offic e o f Researc han dDevelopment , EPA , an dapprove dfo r publication . Mentio n o f trad e name s o r

commercia l product s doe s no t constitut e endorsemen t o r recommendatio n fo r

use . 

## AVAILABILIT Y NOTIC E Thi s documen t

i s availabl e throug hth e Librar y Service s Office , MD-35 , Researc hTriangl e Park , N.C . 27711 . Th e printe dversio n wil l als o b e availabl e fro mth e Superintenden t o f Documents , U.S . Governmen t

Printin g Office , Washington , D.C . 20402 .



## Publicatio n No . EPA-600/8-77-01 7P. 4



### EPA-600/8-77-01 7 December197 7



# AI RQUALIT Y CRITERI A

FO R LEA D

U.S . ENVIRONMENTA L PROTECTIO N AGENC Y OFFICE OF RESEARC H AN D DEVELOPMEN T

WASHINGTON , D.C . 2046 0 Fo rsal e b y th e Superintenden to f Documents' , U.S . Governmen t Printin g Office , Washington , D.C . 2040 2P. 5



# PREFACE Thi s documen t

ha s bee n prepare dpursuan t t o Sectio n 108(a)(2 ) o f th e Clea n Ai r Act , a s amended , an dth e Administrator' s actio n o n Marc h31,1976 , o f listin g lea d a s acriteri apollutant . Unde r th e Act , th e issuanc e o f ai r qualit y criteri ai s avita l ste p in aprogra mo f

responsibl e technological , social , an dpolitica l actio n t o pro tec t th e publi c fro mth e advers e effect s o f ai r pollution . Thes e healt han dwelfar e criteri afulfil l th e regulator y purpos e o f servin g a s th e basi s upo n whic hth e Administrato r mus t promulgat e nationa l primar y an dsecond

ar y ambien t

ai r qualit y standard s fo r

lea dunde r

Sectio n 10 9 o f

th e Clea n Ai r

Act . Th e propose dstandard s ar e bein g publishe dconcurrentl y wit hth e publicatio n o f thi s criteri adocument . Althoug hth e preparatio n o f acriteri adocumen t

require s acomprehensiv e revie w an devaluatio n o f th e curren t

scientifi c knowledg e regardin g th e ai r pollu

tan t in question , th e documen t doe s no t

constitut e acomplete , in-dept hscientifi c review . Th e reference s cite dd o no t constitut e acomplet e bibliography . Th e objec

tiv e i s t o evaluat e th e scientifi c dat abas e an dt o formulat e criteri awhic hma y serv e a s th e basi s fo r

decision s regardin g th e promulgatio n o f anationa l ambien t

ai r qualit y standar dfo r

lead . I n th e cas e o f

lead , a s wel l a s othe r

ai r pollutants , advers e healt heffect s ar e a consequenc e o f

th e tota l bod y burde n resultin g fro mexposur e vi aal l route s o f in

take . I t i s necessary , therefore , t o evaluat e th e relativ e contributio n mad e b y in

halatio n an dingestio n o f atmospheri c lea dt o th e tota l bod y burden . Th e Agenc y i s please dt o acknowledg e th e effort s an dcontribution s o f al l per sons ' an dgroup s wh o hav e participate da s author s o r reviewer s t o thi s document . I n th e ias t analysis , however , th e Environmenta l Protectio n Agenc y i s responsibl e fo r it s content .

DOUGLA S M . COSTL E Administrato r U.S . Environmenta l Protectio n Agenc y

i nP. 6



## ABSTRAC T Thi s documen t

summarize s curren t

knowledg e abou t

th e relationship s o

f air

born e leadt o ma

n an dhi s environment . Th e effects that hav e bee n observe dt o oc cur whe n airborn e leadha s reache dor exceede dspecifi c level s fo r specifi c time period s constitut e th e centra l criteri ao n whichEP

A will bas e anational ambient air quality standar dfo

r lead . Althoug hthi s document

deal s mainl y wit

hairborn e lead , i

t als o outline s othe r environmental route s o

f exposure . Primary exposure t o airborn e lea doccur s directl y vi ainhalation , andit s source s ar e relativel y eas y t o identify . Secondar y ex posure ma y occur throug hingestio n o

f food s fro mcrop s contaminate db

y airborn e leador , especiall y i

n children , throug hmouthin g o f nonfoo ditem s an dmaterial s s o contaminated . Exposure s t o nonairborn e leadma y als o b e direc t

andindirect , and route s includ e ingestio n o

f food s containin g leadattributabl e t o natura l uptake and t o processing . In man , leadprimaril y affects re dbloo dcells , th e centra l andperiphera l nervou s systems , sof

t tissue s suc

ha s liver andkidney , andbone ; th e latte r ultimatel y se quester s 9 5 percent

o f th e body' s leadburden . Significan t biological indice s o

f ex posure t o leadinclud e microgra mquantitie s o

f leadando

f erythrocyt e pro toporphyri n (EP ) per

decilite r o f bloo d(/xg/dl) . Advers e effects rang e fro mele

vate dE Pandmil danemi aa t 20 t o 4 0 fig Pb/dl—throug hgastrointestinal , renal , an dhepati c pathologies—to severe neurobehaviora l impairment a t >8 0 t o 120 fig Pb/dl , sometime s culminatin g a t thos e level s i

n convulsion s andabrup t death . Preschoo l childre n anddevelopin g fetuse s ar e th e population s a t greates t risk .

I V

## SCIENC E ADVISOR Y BOAR D SUBCOMMITTE E O N SCIENTIFI C CRITERI A FO RENVIRONMENTA L LEA D P. 7 

# 1

Th e substanc e o f

thi s documen t

wa s revie w b y aSubcommitte e o n Scientifi c Cri

teri afo r Environmenta l Lead , Scienc e Advisor y Board , i n publi c session . CHAIRMAN : Dr . Roge r

O . McClellan , Directo r o f Inhalatio n Toxicolog y Researc hInstitute , Lovelac e Foundation , P.O . Bo x 5890 , Albuquerque , Ne w Mexic o 8711 5 CONSULTANTS : Dr . J . Julia n Chisolm , Jr. , Senio r Staf f Pediatrician , Baltimor e Cit y Hospital , 494 0 Easter n Avenue , Baltimore , Marylan d21224 ; an dAssociat e Professo r o f Pediatrics , John s Hopkin s Universit y Schoo l o f Medicin e Dr . Pau l B . Hammond , Professo r o f Environmenta l Health , Departmen t o f En

vironmenta l Health , Universit y o f Cincinnat i Medica l Center , 322 3 Ede n Avenue , Cincinnati , Ohi o 4526 7 Dr . Jame s G . Horsfall , Directo r Emeritus , Departmen t o f Plan t Patholog y an d Botany , Connecticu t

Agricultur e Experimen t Station , Ne w Haven , Connecti

cu t 0650 4 MEMBERS : Dr . Samue l S . Epstein , Professo r o f Occupationa l an dEnvironmenta l Medicine , Schoo l o f

Publi c Health , Universit y o f Illinois , P.O . Bo x 6998 , Chicago , Il

linoi s 6068 0 Dr . Edwar dF . Ferrand , Assistan t Commissione r

fo r Science s an dTechnology , Ne w Yor k

Cit y Dept . fo r

Ai r Resources , 5 1 Asto r

Place , Ne w York , Ne w Yor k 1000 3 Dr . Sheldo n K . Friedlander , Professo r o f Chemica l Engineerin g an dEnviron

menta l Healt hEngineering , W . M . Kec k Laboratory , Californi aInstitut e o f Technology , Pasadena , Californi a9110 9 Dr . Jennife r

L . Kelsey , Associat e Professo r o f Epidemiology , Yal e Universit y Schoo l o f Medicine , Departmen t

o f Epidemiolog y an dPubli c Health , 6 0 Col

leg e Street , Ne w Haven , Connecticu t 0650 4 Dr . Rut hLevine , Chairman , Graduat e Divisio n o f Medicin e an dDentistry , Bosto n Universit y Colleg e o f Medicine , Boston , Massachusett s 0211 8 Mailin g address : 21 2 Craft s Road , Chestnu t Hill , Brookline , Massachusett s 0216 7 Dr . Bailu s Walker , Jr. , Director , Environmenta l Healt hAdministration , Depart

men t o f Environmenta l Services , Governmen t o f th e Distric t

o f Columbia , 80 1 Nort hCapitol , NE , Washington , D.C . 2000 2 STAF F OFFICER : Mr . Erns t

Linde , Scientis t

Administrator , Scienc e Advisor y Board , U.S . Environ

menta l Protectio n Agency , Crysta l Mal l Buildin g 2 , 192 1 Jefferso n Davi s Highway , Arlington , Virgini a2046 0P. 8



## CONTRIBUTOR S AN D REVIEWER S Mr . Geral dG . Akland , Environmenta l Monitorin g an dSuppor t Laboratory , En

vironmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . C . Ale x Alexander , Adjunc t Professo r

o f Medicin e an dChie f

o f Hospita l Medica l Staff

, Schoo l o f

Medicine , Wrigh t

Stat e University , Dayton , Ohi o 4543 1 Dr . A . P . Altshuller , Director , Environmenta l Science s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . Ann aBaetjer , Professo r Emeritu s o f

Environmenta l Medicine , Departmen t o f Environmenta l Medicine , Schoo l o f Hygien e an dPubli c Health , Th e John s Hopkin s University , 61 5 Nort hWolf e Street , Baltimore , Marylan d2120 5 Dr . Donal dBarltrop , Pediatric s Unit , St . Mary' s Hospita l Medica l School , Lon

do n W 2 1PG , Englan d Ms . Gayl aBenignus , Technica l Consultant , Researc hTriangl e Park , Nort h Carolin a2770 9 Dr . Irwi n H . Billick , Progra mManager , Lead-Base dPain t Poisonin g Preventio n Research , Divisio n o f

Housin g Research , Offic e o f th e Assistan t

Secretar y fo r Polic y Developmen t

an dResearch , Departmen t o f Housin g an dUrba n Development , Washington , D.C . 2041 0 Dr . Rober t

P . Botts , Environmenta l Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , 20 0 S W35t h Street , Corvallis , Orego n 9733 0 Dr . Rober t

Bornschein , Departmen t o f Environmenta l Health , Colleg e o f Medicine , Universit y o f Cincinnati , Cincinnati , Ohi o 4526 7 Dr . Ronal dL . Bradow , Environmenta l Science s Researc hLaboratory , Environ

menta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , Nort hCarolin a2771 1 Dr . Kennet hBridbord , Director , Offic e o f Extramura l Coordinatio n an dSpecia l Projects , Nationa l Institut e fo r Occupationa l Safety an dHealth , 560 0 Fisher s Lane , Rockville , Marylan d2085 2 Dr . Marijo n Bufalini , Environmenta l Science s Researc hLaboratory , Environ

menta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , Nort hCarolin a2771 1 Dr . Rober t

Burger , Senio r

Scientist , Researc hTriangl e Institute , P.O . Bo x 12194 , Researc hTriangl e Park , Nort hCarolin a2770 9 Dr . Joh n B . Clements , Environmenta l Monitorin g an dSuppor t Laboratory , En

vironmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Mr . Stanto n Coerr , Strategie s an dAi r Standard s Division , Offic e o f Ai r Qualit y Plannin g an dStandards , U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , Nort hCarolin a2771 1Ms . Josephin e S . Cooper , Strategie s an dAi r Standard s Division , Offic e o f Ai r Qualit y Plannin g an dStandards , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Mr . Gunthe r

F . Craun , Healt hEffect s Researc hLaboratory , U.S . Environmenta l Protectio n Agency , Cincinnati , Ohi o 4526 8 Dr . Annemari e Crocetti , Professo r o f Epidemiology , Ne w Yor k Medica l College , Ne w York , Ne w Yor k

1002 9 Dr . Terr i Damstra , Offic e o f Healt hHazar dAssessment , Nationa l Institut e o f Environmenta l Healt hServices , Researc hTriangl e Park , Nort hCarolin a 2770 9 Dr . Clif f Davidson , Graduat e Researc hAssistant , Californi aInstitut e o f Tech

nology , Mai l Sto p 138-78 , Pasadena , Californi a9110 9 Dr . Iva n Diamond , Departmen t o f Neurology , Schoo l o f

Medicine , Universit y o f California , San Francisco , Californi a9414 3 Dr . Michae l Dowe , Jaycor , Incorporated , Researc hTriangl e Park , Nort h Carolin a2770 9 Dr . Be n B . Ewing , Professo r an dDirector , Institut e fo r Environmenta l Studies , Universit y o f

Illinois , 40 8 S . Goodwi n Avenue , Urbana , Illinoi s 6180 1 Dr . Harol dFurst , Professo r o f Epidemiology , Ne w Yor k Medica l Colleg e an d Ne w Yor k

Cit y Healt hDepartment , Ne w York , Ne w Yor k 1002 9 Mr . Warre n Galke , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . J.H.B . Garner , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . Joh n T . Gatzy , Associat e Professo r o f Pharmacology , Schoo l o f Medicine , Universit y o f

Nort hCarolina , Chape l Hill , Nort hCarolin a2751 4 Dr . Rober t

Goyer , Departmen t

o f Pathology , Universit y o f Wester n Ontario , Londo n 72 , Ontario , Canad a Dr . Leste r

D . Grant , Associat e Professo r o f Psychiatry , Schoo l o f Medicine , Universit y o f

Nort hCarolina , Chape l Hill , Nort hCarolin a2751 4 Mr . Danie l Greathouse , Healt hEffect s Researc hLaboratory , U.S . Environmen

ta l Protectio n Agency , Cincinnati , Ohi o 4526 8 Dr . Vi c Hasselblad , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . Dere k

Hodgson , Professor , Departmen t o f Chemistry , C44 8 Kenan , Univer

sity o f Nort hCarolina , Chape l Hill , Nort hCarolin a2751 4 Dr . Joh n Horn , Environmenta l Consultant , 75 8 Oxfor dStreet , West , London , Ontario , Canad aN6M1V 2 Dr . Rober t

J . M . Horton , Senio r Researc hAdvisor , Healt hEffect s Researc h Laboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Mr . Alle n G . Hoyt , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . F . Gordo n Hueter , Associat e Director , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . Emmet t

S . Jacobs , Divisio n Head , Additive s an dEnvironmenta l Studies , E . I . d u Pon t

d e Nemour s an dCompany , Inc. , Petroleu mLaboratory , Wilmington , Delawar e 1989 8

v n^ p i n

Mr . Gar y L . Johnson , Industria l Environmenta l Researc hLaboratory , Environ

menta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , Nort hCarolin a2771 1 Mr . Rober t

Kellam , Strategie s an dAi r Standard s Division , Offic e o f Ai r Qualit y Plannin g an dStandards , U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , Nort hCarolin a2771 1 Dr . Carol e A . Kimmel , Nationa l Cente r fo r Toxicologica l Research , Jefferson . Arkansa s 7207 9 Dr . Rober t

R . Kinnison , Environmenta l Monitorin g an dSuppor t Laboratory , U.S . Environmenta l Protectio n Agency , P.O . Bo x 15027 , La s Vegas , Nevad a 8911 4 Dr . Joh n H . Knelson , Director , Healt hEffect s Researc hLaboratory , Environ

menta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , Nort hCarolin a2771 1 Dr . Marti n R . Krigman , Professo r o f Pathology , Schoo l o f

Medicine , Universit y o f Nort hCarolina . Chape l Hill , Nort hCarolin a2751 4 Dr . Rober t

E . Lee , Deput y Director , Healt hEffect s Researc hLaboratory , En

vironmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . G . J . Love , Epidemiolog y Consultant , Researc hTriangl e Park , Nort h Carolin a2770 9 Dr . Jame s MacNeill , Pediatrician , Hillsid e Medica l Center , E l Paso , Texa s 7990 3 Dr . Kathry n R . Mahaffey . Divisio n o f Nutrition . Foo dan dDru g Administration , Departmen t

o f Health , Educa t

ion . an dWelfare , 109 0 Tusculu mAvenue , Cincinnati . Ohi o 4522 6 Dr . Ale c E . Martin , Visitin g Scientist , Offic e o f Healt hHazar dAssessment , Na

tiona l Institut e o f

Environmenta l Healt hSciences , P.O . Bo x 12233 , Researc h Triangl e Park , Nort hCarolin a2770 9 Dr . Edwar dB . McCabe . 322 5 Knollwoo dWay . Madison , Wisconsi n 5371 3 Mr . Gar y D . McCutchen , Emissio n Standard s an dEngineerin g Division , Offic e o f Ai r Qualit y Plannin g an dStandards , U.S . Environmenta l Protectio n Agen

cy , Researc hTriangl e Park , Nort hCarolin a2771 1 Mr . Thoma s B . McMullen , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Mr . Josep hMerenda . Offic e o f Mobil e Sourc e Ai r

Pollutio n Control , Offic e o f Ai r an dWast e Management , U.S . Environmenta l Protectio n Agency , Wash

ington , D.C . 2046 0 Ms . Margarit aM . Morrison , Technica l Informatio n Specialist , Progra mOpera

tion s Office , Healt hEffect s Researc hLaboratory , Environmenta l Researc h Center , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . Pau l Mushak , Associat e Professo r o f Pathology , Schoo l o f

Medicine , Univer

sity o f Nort hCarolina , Chape l Hill , Nort hCarolin a2751 4 Dr . D . F . Nataush , Professo r o f Chemistry , Colorad o Stat e University , For t Col

lins , Colorad o 8052 3 Dr . Joh n C . Nduaguba , Assistan t Professo r

o f Medicine , Schoo l o f

Medicine , Wrigh t Stat e University , Dayton , Ohi o 4543 1 Dr . Herber t

L . Needleman , Th e Children' s Hospita l Medica l Center , 30 0 Long

woo dAvenue , Boston , Massachusett s 0211 5 Dr . Stat aNorton , Departmen t o f Pharmacology , Universit y o f Kansa s Medica l Center , Kansa s City , Kansa s 6611 0 vii iP.1 1

Mr . Joh n O'Connor , Strategie s an dAi r Standard s Division , Offic e o f Ai r Qualit y Plannin g an dStandards , U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , Nort hCarolin a2771 1 Dr . Sergi o Piomelli , Professo r o f Pediatric s an dDirecto r o f Pediatri c Hematology , Schoo l o f

Medicine , Ne w Yor k

Universit y Medica l Center , 55 0 Firs t Avenue , Ne w York , Ne w Yor k 1001 6 Dr . Herber t

Posner , Offic e o f

Healt hHazar dAssessment , Nationa l Institut e o f Environmenta l Healt hSciences , Researc hTriangl e Park , Nort hCarolin a 2770 9 Dr . Jerr y Ptasnik , Directo r o f Specia l Education , E l Pas o Cit y Schools , E l Paso , Texa s 7990 3 Dr . Michae l J . Quigley , Healt hEffect s Consultant , Researc hTriangl e Park , Nort hCarolin a2770 9 Dr . Ketura hReinbold , Associat e Researc hBiologist , Institut e fo r Environmenta l Studies , Universit y o f

Illinois , 40 5 S . Goodwi n Avenue , Urbana , Illinoi s 6180 1 Dr . Lawrenc e Reiter , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . Joh n F . Rogers , Assistan t Professo r

o f Medicine , Schoo l o f Medicine , Universit y o f

Nort hCarolina , Chape l Hill , Nort hCarolin a2751 4 Dr . Gar y L . Rolfe , Associat e Professo r o f Forestry , Institut e fo r

Environmenta l Studies , Universit y o f

Illinois , 40 8 S . Goodwi n Avenue , Urbana , Illinoi s 6180 1 Dr . Donal dRouth , Professo r o f Clinica l Psychology , Schoo l o f Medicine , Universit y o f

Nort hCarolina , Chape l Hill , Nort hCarolin a2751 4 Mr . Rober t

C . Ryans , Writer-Editor , Environmenta l Researc hLaboratory , U.S . Environmenta l Protectio n Agency , Colleg e Statio n Road , Athens , Georgi a 3060 5 Mr . Edwar dA . Schuck , Environmenta l Monitorin g an dSuppor t Laboratory , U.S . Environmenta l Protectio n Agency , P.O . Bo x 15027 , La s Vegas , Nevad a 8911 4 Dr . R . K . Skogerboe , Professo r o f Chemistry , Colorad o Stat e University , For t Collins , Colorad o 8052 3 Dr . Ceci l Slome , Professo r o f Epidemiology , Schoo l o f Publi c Health , Universit y o f Nort hCarolina , Chape l Hill , Nort hCarolin a2751 4 Mr . Jame s R . Smith , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . R . D . Snee , Biostatistician , E . I . d u Pon t d e Nemour s an dCompany , Inc. , Petroleu mLaboratory , Wilmington , Delawar e 1989 8 Mr . Andre w G . Stead , Statistician , Healt hEffect s Researc hLaboratory , Environ

menta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , Nort hCarolin a2771 1 Mr . Ori n W . Stopinski , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Dr . Richar dJ . Thompson , Environmenta l Monitorin g an dSuppor t Laboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 Ms . Beverl y E . Tilton , Healt hEffect s Researc hLaboratory , Environmenta l Researc hCenter , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolin a2771 1 I XP.1 2 *********



### Mr . Ia n von Lindern , Environmental Engineer , Departmen t o f Healthan d Welfare , Divisio n o

f th e Environment , State o f Idaho , 32

4 2n dStreet , East , Twin Falls , Idah o 8330 1 Ms . P . A . Warrick , Technical Consultant , Schoo l o f Publi c Health , Universit

y o f Nort hCarolina , Chape l Hill , Nort hCarolin a2754 1 Mr . Tony Yankel , Divisio n o f th e Environment , Departmen t o f Healthan d Welfare , Statehouse , Boise , Idah o 8372 0 Dr . R . L . Zielhuis , Universitei t von Amsterdam , Corone l Laboratorium , Eerst e Constantij n Huygersstcaa

t 20 , Amsterdam , Netherland s Dr . R . L . Zimdahl , Professor o f Botany an dPlant

Pathology , Colorad o State University , Fort

Collins , Colorad o 8052 3

# CONTENT S

Paiie PREFAC Eii i ABSTRAC T iv SCIENTIFI C ADVISOR Y BOAR D SUBCOMMITTE EO N SCIENTIFI C CRITERI A FO RENVIRONMENTA LLEA D v CONTRIBUTOR S AN D REVIEWER S v i FIGURE S xv i TABLE S xi x ABBREVIATION S AN D SYMBOL S xxii i 1 . SUMMAR Y AN D CONCLUSION S 1- 1 1. 1 Introductio n 1- 1 1.1. 1 Potentia l Exposur e t o Environmenta l Lea d1- 1 1.1. 2 Source s o f

Environmenta l Lea d1-2 1.1. 3 Monitorin g o f

Environmenta l Lea d1- 3 1. 2 Effect s o f

Lea do n Ma n an dHi s Environmen t 1- 4 1.2. 1 Effec t

o f Lea do n Ma n 1- 4 1.2. 2 Effect s o f

Lea do n th e Ecosyste m1- 9 1. 3 Effect s o f

Lea do n Population s 1-1 0 1. 4 Assessmen t

o f Ris k fro mHuma n Exposur e t o Lea d1-1 1 1.4. 1 Us e o f

Blood-Lea dLevel s in Ris k Assessmen t

1-1 1 1.4. 2 Us e o f

Biologica l an dAdvers e Healt hEffect s o f Lea di n Ris k Assessmen t

1-1 2 1.4. 3 Population s at

Ris k 1-1 4 2 . INTRODUCTIO N 2- 1 3 . CHEMICA LAN D PHYSICA LPROPERTIE S 3- 1 3. 1 Elementa l Lea d3- 1 3. 2 Genera l Chemistr y o f Lea d3- 1 3. 3 Organometalli c Chemistr y o f Lea d3- 2 3. 4 Comple x Formatio n an dChelatio n 3- 2 3. 5 Reference s fo r

Chapte r 3 3- 4 4 . SAMPLIN GAN D ANALYTICA LMETHOD S FO RLEA D 4- 1 4. 1 Introductio n 4- 1 4. 2 Samplin g 4- 2 4.2. 1 Sample r

Sit e Selectio n 4- 2 4.2. 2 Samplin g Error s 4- 2 4.2. 3 Samplin g fo r

Airborn e Particulat e Lea d4- 3 4.2. 4 Samplin g fo r

Vapor-Phas e Organi c Lea dCompounds . . 4- 4 4.2. 5 Samplin g fo r

Lea din Othe r

Medi a4- 4 4.2. 6 Sourc e Samplin g 4- 6 4.2. 7 Filte r

Selectio n an dSampl e Preparatio n 4- 7

X IP.1 4

4. 3 Analysi s 4- 8 4.3. 1 Colorimetri c Analysi s 4- 8 4.3. 2 Atomi c Absorptio n Analysi s 4- 8 4.3. 3 Anodi c Strippin g Voltammetr y 4- 9 4.3. 4 Emissio n Spectroscop y 4- 9 4.3. 5 Electro n Microprob e 4-1 0 4.3. 6 X-Ra y Fluorescenc e 4-1 0 4.3. 7 Method s f©

r Compoun dAnalysi s 4-1 1 4. 4 Conclusion s 4-1 1 4. 5 Reference s fo r

Chapte r 4 4-1 1 5 . SOURCE S AN D EMISSION S 5- 1 5. 1 Natura l Source s 5- 1 5. 2 Man-Mad e Source s 5- 1 5.2. 1 Productio n 5- 1 5.2. 2 Utilizatio n 5- 1 5.2. 3 Emission s 5- 2 5. 3 Reference s fo r

Chapte r 5 5- 5 6 . TRANSFORMATIO N AN D TRANSPOR T 6- 1 6. 1 Introductio n 6- 1 6. 2 Physica l an dChefiica l Transformation s i n th e Atmospher e .. . 6- 1 6.2. 1 Physica l Transformation s 6- 1 6.2. 2 Chemica l Transformation s 6- 4 6. 3 Transpor t

in Ai r 6- 8 6.3. 1 Distributio n Mechanism s 6- 8 6.3. 2 Remova l Mechanism s 6-1 2 6.3. 3 Model s 6-1 9 6. 4 Transformatio n an dTranspor t in Othe r

Environmenta l Medi a6-2 0 6.4. 1 Soil s 6-2 0 6.4. 2 Wate r

6-2 1 6.4. 3 Plant s 6-2 3 6. 5 Reference s fo r

Chapte r 6 6-2 5 7 . ENVIRONMENTA LCONCENTRATION S AN D POTENTIA L EXPOSURE S 7- 1 7. 1 Ambien t

Ai r Exposure s 7- 1 7.1. 1 Nationa l Ai r

Surveillanc e Networ k

(NASN ) Dat a7- 1 7.1. 2 Airborn e Particl e Siz e Distributio n 7- 4 7.1. 3 Vertica l Gradient s o f Lea din th e Atmospher e 7- 4 7. 2 Mobil e Sourc e Exposure s 7- 6 7. 3 Poin t

Sourc e Exposure s 7- 7 7. 4 Dietar y Exposure s 7- 9 7.4. 1 Foo d7- 9 7.4. 2 Wate r

7-1 1 7. 5 Occupationa l Exposure s 7-1 2 7.5. 1 Exposure s i n Lea dMining , Smelting , an dRefinin g ... . 7-1 2 7.5. 2 Exposure s in Weldin g an dShipbreakin g 7-1 3 7.5. 3 Exposure s in th e Electri c Storag e Batter y Industr y ... . 7-1 3 7.5. 4 Exposure s in th e Printin g Industr y 7-1 3 7.5. 5 Exposure s in Alky l Lea dManufactur e 7-1 3 7.5. 6 Exposure s in Othe r Occupation s 7-1 3 7.5. 7 Exposure s Resultin g fro mManmad e Material s 7-1 4 7.5. 8 Historica l Change s 7-1 4 7. 6 Reference s fo r

Chapte r 7 7-1 4 xi iP.1 5

Page 8 . EFFECT S O FLEA D O N ECOSYSTEM S 8- 1 8. 1 Effect s o n Domesti c Animals , Wildlife , an dAquati c Organism s 8- 1 8.1. 1 Domesti c Animal s 8- 1 8.1. 2 Wildlif

e 8- 3 8.1. 3 Aquati c Organism s 8- 5 8. 2 Effect s o n Plant s 8- 8 8.2. 1 Route s o f

Plan t Exposur e 8- 8 8.2. 2 Effect s o n Vascula r Plant s 8-1 0 8.2. 3 Effect s o n Nonvascula r Plant s 8-1 1 8. 3 Effect s o n Relationship s Betwee n Arthropod s an dLitte r Decom

positio n 8-1 3 8. 4 Reference s fo r

Chapte r 8 8-1 3 9 . QUANTITATIV EEVALUATIO N O FLEA D AN D BIOCHEMI

CA LINDICE S O FLEA D EXPOSUR EI N PHYSIOLOGICA L MEDI A 9- 1 9. 1 Genera l Samplin g Procedure s fo r Lea din Biologica l Media . . . 9- 1 9. 2 Bloo dLea d9- 2 9. 3 Urin e Lea d9- 3 9. 4 Soft-Tissu e Lea d9- 3 9. 5 Hai r Lea d9- 3 9. 6 Lea din Teet han dBon e 9- 3 9. 7 Comparativ e Studie s o f Method s fo r

Measuremen t

o f Lea din Biologica l Medi a9- 4 9. 8 Measurement s o f

Urinar y 8-Aminolevulini c Aci d(ALA-U ) .. . 9- 4 9. 9 Measurement s o f

8-Aminolevulini c Aci dDehydratas e (ALAD ) 9- 5 9.1 0 Measurement s o f

Fre e Erythrocyt e Protoporphyri n (FEP)... . 9. 6 9.1 1 Reference s fo r

Chapte r 9 • 9- 6 10 . METABOLIS M O FLEA D 10- 1 10. 1 Introductio n 10- 1 10. 2 Absorptio n 10- 1 10.2. 1 Respirator y Absorptio n 10- 1 10.2. 2 Gastrointestina l Absorptio n 10- 2 10.2. 3 Cutaneou s Absorptio n 10- 5 10. 3 Distributio n 10- 5 10.3. 1 Huma n Studie s 10- 5 10.3. 2 Anima l Studie s 10- 6 10. 4 Eliminatio n 10- 7 10.4. 1 Huma n Studie s 10- 7 10.4. 2 Anima l Studie s 10- 7 10. 5 Alky l Lea dMetabolis m10- 8 10. 6 Metaboli c Consideration s i n th e Identificatio n o f Susceptibl e Subgroup s in th e Populatio n 10- 8 10. 7 Reference s fo r

Chapte r 1 0 10- 9 11 . BIOLOGICA LEFFECT S O FLEA D EXPOSUR E11- 1 11. 1 Introductio n 11- 1 11. 2 Cellula r

an dSubcellula r

Effect s o f

Lea d11- 1 11.2. 1 Effect s o n Enzyme s , 11- 1 11.2. 2 Organella r

an dCellula r

Effect s 11- 1 11.2. 3 Effect s o f

Lea do n Chromosome s 11- 4 11.2. 4 Carcinogenesi s 11- 5 11. 3 Clinica l Lea dPoisonin g 11- 6 11. 4 Hematologica l Effect s o f Lea d11- 7 xii i1P P I (• • P.1 6

Page 11.4. 1 Anemi a11- 7 11.4. 2 Effect s o f

Lea do n Erythrocyt e Morpholog y an dSurviva l 11- 7 11.4. 3 Effect s o f

Lea do n Hem e Synthesi s 11-8 11.4. 4 Othe r

Hematologica l Effect s 11-1 3 11.4. 5 Summar y o f

Effect s o f

Lea do n th e Hematopoieti c Syste m11-1 3 11. 5 Effect s o f

Lea do n Neurophysiolog y an dBehavio r 11-1 4 11.5. 1 Huma n Studie s 11-1 5 11.5. 2 Anima l Studie s 1 1 -2 6 11. 6 Effect s o f

Lea do n th e Rena l Syste m1 1 -4 4 11.6. 1 Acut e Effect s 1 1 -4 4 11.6. 2 Chroni c Effect s 1 1 -4 4 11. 7 Reproductio n an dDevelopmen t 1 1 -4 5 11.7. 1 Huma n Studie s 1 1 ^4 6 11.7. 2 Anima l Studie s 1 1 -4 8 11. 8 Th e Endocrin e Syste m11-5 1 11. 9 Th e Hepati c Syste m11-5 2 11. 1 OTh e Cardiovascula r Syste m11-5 2 11.1 1 Th e Immunologi c Syste m11-5 3 11.1 2 Th e Gastrointestina l Syste m1 1 -5 4 11.1 3 Reference s fo r

Chapte r 1 1 11-5 4 12 . ASSESSMEN T O FLEA D EXPOSURE S AN D ABSORPTIO N I N HUMA N POPULATION S 12- 1 12. 1 Introductio n 12- 1 12. 2 Lea din Huma n Population s 12- 1 12.2. 1 Statistica l Description s an dImplication s 12- 1 12.2. 2 Geographi c Variabilit y in Huma n Bloo dLea dLevel s . 12- 4 12.2. 3 Demographi c Variable s an dHuma n Bloo dLea dLevel s 12- 6 12. 3 Relationship s Betwee n Externa l Exposure s an dBloo dLea d Level s 12-1 0 12.3. 1 Ai r

Exposure s 12-1 0 12.3. 2 Soi l an dDas t

Exposure s 12-2 9 12.3. 3 Foo dan dWate r Exposure s 12-3 2 12.3. 4 Effect s o f

Lea din th e Housin g Environment : Lea din Pain t 12-3 3 12.3. 5 Secondar y Exposur e o f Childre n Fro mParents ' Occupa

tiona l Exposur e 12-3 6 12.3. 6 Miscellaneou s Source s o f Lea d12-3 8 12. 4 Summar y 12-3 8 12. 5 Reference s fo r

Chapte r 1 2 12-3 9 13 . EVALUATIO N O FHUMA N HEALT H RISK S FRO M EXPOSUR E T O LEA D AN D IT S COMPOUND S 13- 1 13. 1 Introductio n 13- 1 13. 2 Sources , Routes , ari dMechanism s o f Entr y 13- 1 13.2. 1 Source s 13- 1 13.2. 2 Route s an dMechanism s o f Entr y 13- 2 13. 3 Evidenc e o f

Increase dBloo dLea dLevel s i n Human s Expose dt o Environmenta l Lea d13- 2 13.3. 1 Relationship s Betwee n Bloo dLea dLevel s an dSingle

Sourc e Exposure s 13- 2 13.3. 2 Multiple-S®urc e Exposure s 13- 3 xi vP.1 7

Page 13.3. 3 Effec t

o f Hos t Factor s o n Bloo dLea dLevel s 13- 3 13.3. 4 Summar y o f

th e Quantitativ e Relationshi p 13- 3 13. 4 Averaging-Tim e Consideration s 13- 4 13. 5 Biologica l an dAdvers e Healt hEffect s o f Lea din Ma n 13- 4 13.5. 1 Assessmen t

o f Hematologica l Effect s o f Lea d13- 4 13.5. 2 Assessmen t

o f Neurobehaviora l Effect s o f Lea d13- 6 13.5. 3 Effect s o f

Lea do n Reproductio n an dDevelopment... . 13- 7 13.5. 4 Othe r

Healt hEffect s 13- 8 13.5. 5 Dos e Effect/Respons e Relationship s 13- 8 13. 6 Population s a t

Ris k 13-1 1 13.6. 1 Childre n a s aPopulatio n a t Ris k 13-1 1 13.6. 2 Pregnan t

Wome n an dth e Conceptu s a s aPopulatio n a t Ris k , 13-1 2 13. 7 Descriptio n o f

Unite dState s Populatio n in Relatio n t o Probabl e Lea dExposure s 13-1 3 13. 8 Reference s fo r

Chapte r 1 3 13-1 4 APPENDICE S A . GLOSSAR Y A- l B . PHYSICAL/CHEMICA LDAT A FO RLEA D COMPOUND S B- l C . ADDITIONA LSTUDIE S O FENVIRONMENTA LCONCENTRA

TION S O FLEA D C- l D . UNIT S AN D METRI C CONVERSIO N FACTOR S D- l E . A REVIE WO FTHRE ESTUDIE S O N TH EEFFECT S O FLEA D SMELTE REMISSION S I N E LPASO , TEXA S E- l

xvT"* -



## FIGURE S

Page 4- 1 Sequenc e o f

operation s involve din monitorin g fo r lea din th e en vironmen t

4- 2 5- 1 Approximat e flo w o f lea dthroug hU.S . industr y i n 197 5 5- 1 5- 2 Locatio n o f

majo r lea doperation s in th e Unite dStates , 197 6 5- 3 6- 1 Simplifie decologi c flo w char t fo r lea dshowin g principa l cyclin g pathway s an dcompartment s 6- 1 6- 2 Effec t

o f variou s drivin g condition s o n th e amoun t o f lea dexhauste d6- 2 6- 3 Effec t

o f spee do n siz e distributio n o f exhaus t particle s at

differen t roa dloa dcruis e condition s an dusin g Indolen e H O O fue l 6- 2 6- 4 Cumulativ e mas s distribution s fo r lea daeroso l i n aut o exhaus t an da t Pasadena , arecepto r

samplin g sit e 6- 3 6- 5 Differentia l mas s distribution s fo r lea d1 mfro mafreewa y an dat Pasaden asamplin g site s 6- 3 6- 6 Cumulativ e mas s distributio n o f lea dparticle s b y siz e 6- 4 6- 7 Air-lea dvalue s a s afunctio n o f traffi c volum e an ddistanc e fro mth e highwa y 6- 9 6- 8 Relationshi p o f

th e diamete r

o f th e particle s (mass ) t o distanc e fro m th e highwa y 6- 9 6- 9 Lea dconcentratio n profile s i n th e ocean s 6- 9 6-1 0 Midpoin t

collectio n locatio n fo r

atmospheri c sample s collecte dfro m R . V . Trident

nort ho f 30°N , 197 0 throug h197 2 6-1 0 6-1 1 Th e EF crus t

value s fo r

atmospheri c trac e metal s collecte din th e Nort hAtlanti c westerlie s an dat th e Sout hPol e 6-1 0 6-1 2 Lea dconcentratio n profil e i n sno w strat ao f norther n Greenlan d. . 6-1 1 6-1 3 Worl dlea dsmelte r an dalky l lea dproductio n sinc e 175 0 A.D . . . . 6-1 1 6-1 4 210 P b i n Storbree n glacie r ice , 1954-196 6 6-1 1 6-1 5 Predicte ddepositio n velocit y at indicate dheigh t

fo r fi» = 2 0 cm/se c an dz 0 = 3. 0 c m6-1 4 6-1 6 Predicte ddepositio n velocitie s a t 1- mheigh t fo r z 0 = 3. 0 c m... . 6-1 4 6-1 7 Predicte ddepositio n velocitie s a t 1 mfo r / x « = 20 0 cm/se c 6-1 4 6-1 8 Regressio n o f

percentag e lea dparticulate s remove db y dr y deposi

tio n wit hdistanc e fro mroadwa y 6-1 5 6-1 9 Compariso n o f

siz e distributio n o f

lea dparticulate s collecte da t 2 0 an d64 0 f

t fro ma n expresswa y nort ho f Cincinnati , Ohi o 6-1 5 6-2 0 Atmospheri c concentration s o f lea dan dcarbo n monoxid e a s afunc

tio n o f lo g o f distanc e fro medg e o f

highwa y 6-1 5 6-2 1 Atmospheri c lea dconcentratio n a t freewa y sit e i n Pal o Alto , Califor

nia , o n Augus t

15 , 196 6 6-1 6 6-2 2 Averag e lea di n dr y fallou t a s afunctio n o f

distanc e fro mth e freewa y 6-1 6 6-2 3 Fat e o f

lea dcontribute dfro mautomotiv e traffi c i n Lo s Angele s Basi n 6-1 7

xv iP.1 9

NumberPage 6-2 4 Contaminatio n o f dus t b y lea demission s fro mtw o secondar y smelter s 6-1 7 6-2 5 Tota l depositio n o f lea do n Teflo n plate s a t variou s height s abov e th e roo f o f Kec k Laboratories , Californi aInstitut e o f Technology , Pasaden a6-1 9 6-2 6 Lea ddistributio n betwee n filtrat e an dsuspende dsolid s in strea m

wate r fro murba n an drura l compartment s 6-2 2 7- 1 Seasona l pattern s an dtrend s in quarterl y averag e urba n lea dcon centration s 7- 3 7- 2 Nationwid e trend s in regular , premium , an dunleade dgasolin e sales ,

1960-197 6 7- 4 7- 3 Nationwid e trend s in lea dconten t o f regula r an dpremiu mgasoline , 1960-197 6 7- 4 7- 4 Annua l ambien t ai r lea dconcentratio n nea r asmelter , b y area , befor e th e Augus t

197 4 an dAugus t

197 5 survey s 7- 8 8- 1 Simplifie decologi c flo w char t fo r lea dshowin g principa l cyclin g pathway s an dcompartment s 8- 1 8- 2 Concentratio n o f lea din thre e specie s o f smal l mammal s trappe d besid e majo r

an dmino r

road s an dat

arabl e an dwoodlan dsite s 8- 5 8- 3 Mea n lea dconten t in groupe dinsec t

sample s take n fro mlo w an d hig hlea demissio n area s fo r sucking , chewing , an dpredator y feed

in g type s 8- 7 8- 4 Mea n lea dlevel s i n representativ e organism s an dsediment s o f th e compartment s o f

th e drainag e basi n o f

th e Salin e Branc ho f

th e Vermilio n River , Illinoi s 8- 7 8- 5 Tre e rin g analysi s o f lea dconcentration s in urba n an drura l tree s . 8- 9 11- 1 Lea deffect s o n hem e biosynthesi s 11- 8 11- 2 McCarth y genera l cognitiv e inde x score s a s afunctio n o f degre e o f lea dexposur e 11-2 1 11- 3 Score s o n McCarth y subscale s a s afunctio n o f degre e o f

lea dex posur e 11-2 1 11- 4 Peronea l nerv e conductio n velocit y versu s bloo dlea dlevel , Idaho ,

197 4 11-2 5 12- 1 Estimate dcumulativ e distributio n o f bloo dlea dlevel s for

popula

tion s i n whic hth e geometri c mea n leve l i s 15 , 25 , o r 4 0 /xg/dl. . 12- 2 12- 2 Estimate dcumulativ e distributio n o f bloo dlea dlevel s fo r

popula

tion s havin g ageometri c mea n bloo dlea dleve l o f 2 5 /xg/dl , bu t geometri c standar ddeviation s o f 1.2 , 1.3 , o r

1. 5 12- 2 12- 3 Geometri c mean s fo r bloo dlea dvalue s b y rac e an dage , Ne w Yor k City , 197 1 12- 9 12- 4 Arithmeti c mea n o f ai r lea dlevel s b y traffi c count , Dallas , 1976. . 12-1 2 12- 5 Bloo dlead.concentratio n an dtraffi c densit y b y se x an dage , Dallas ,

197 6 12-1 2 12- 6 Monthl y ambien t ai r lea dconcentration s in Kellog , Idaho , 197 1 throug h197 5 12-1 6 12- 7 Annua l ambien t

ai r lea dconcentration , b y area , befor e th e Augus t 197 4 an dAugus t

197 5 survey s 12-1 6 12-8 Bloo dlea dversu s ai r lea dfo r urba n mal e worker s 12-2 5 12- 9 Cumulativ e distributio n o f lea dlevel s in dwellin g unit s 12-3 4 12-1 0 Cumulativ e distributio n o f lea dlevel s b y locatio n in dwelling , al l age s 12-3 5 12-1 1 Cumulativ e distributio n o f lea dlevel s i n dwellin g unit s withunsoun d pain t condition s 12-3 5 xvi iP.2 0



### 12-1 2 Cumulativ e frequenc y distributio n of bloo dleadlevel s foundi n Pittsburg hhousin g survey 12-3 6 12-1 3 Correlatio n o

f children' s bloo dleadlevel s wit hfraction s o

f surface s withi n adwellin g havin g leadconcentration s > 2 m g Pb/cm 2 

### 12-3 6 13- 1 Dose-respons e curv e fo r percen t ALA D inhibitio n fo

r adult s an d childre n a s afunctio n of

bloo dleadleve l 13- 9 13- 2 Dose-respons e curv e fo r ALA i n urin e (ALA-U ) a s afunctio n o f bloo dlea dlevel 13- 9 13- 3 Dose-respons e curv e fo r FE Pa s afunctio n o

f bloo dleadlevel... . 13- 9 13-4 Dose-respons e curv e fo r FE Pa s afunctio n o

f bloo dlea

dlevel... . 13- 9 13- 5 Dose-respons e curv e for FE Pa s afunctio n of

bloo dleadlevel... . 13-1 0 13- 6 EPA calculate ddose-respons e curv e for ALA- U (fromAza

r e t al. ) 13-1 0 C- l Location s o

f fixedsamplin g station s i n Kanawh aRiver

Valley... . C- 3 C- 2 Air samplin g site s fo

r Souther n Solano , California , study C- 3 C- 3 Omaha , Nebraska , study : mea n monthl y composite atmospheri c lead at industrial , commercial , mixed , an dtw o residential site s C- 4 C- 4 Settleabl e particulat e lea dradia l distributio n fro

mHelen aValle y environmenta l pollutio n study C- 5 C- 5 Annual averag e o

f settleabl e particulat e leada t site s nea r Missour i leadmin e an dsmelter

C- 6 C- 6 Schemati c pla

n o f lea dmin e andsmelter

fromMez aValley , Yugoslavia , stud

y C- 7 C- 7 Soil transect s b

y tw o streets : Curv e A = low traffi c volum e (40 0 veh/day) ; Curv e B = hig

htraffi c volum e (14,00 0 veh/day ) C- 8 C- 8 Surfac e soi l level s o f lea di n E l Paso , Texas , an dDon aAn aCounty , Ne w Mexico , 197 2 C- 8

xvi nP.2 1



# TABLE S

Page 1- 1 Bloo dlea dlevel s versu s lowest-observed-effect s level s 1-1 3 1- 2 Estimate dpercentag e o f subject s wit hALA- U exceedin g 5 mg/ 1 fo r variou s bloo dlea dlevel s 1-1 4 1- 3 Estimate dpercentag e o f childre n wit hE Pexceedin g specifie dcutof f point s fo r

variou s bloo dlea dlevel s 1-1 4 3- 1 Propertie s o f

elementa l lea d3- 1 3- 2 Isotope s o f

lea d3- 1 3- 3 Propertie s o f

majo r organolea dcompound s 3- 2 4- 1 Dail y foo dintak e 4- 6 5- 1 U.S . consumptio n o f lea db y produc t

categor y 5- 2 5- 2 Estimate datmospheri c lea demission s fo r th e Unite dStates , 197 5 . 5- 3 6- 1 Compariso n o f

siz e distribution s o f

lead-containin g particle s in ma jo r samplin g are a6- 4 6- 2 Result s o f

atmospheri c samplin g fo r organi c an dparticulat e lead . . 6- 5 6- 3 Percentag e o f

particulat e versu s vapor-phas e lea di n urba n ai r sam ple s 6- 5 6- 4 Analyse s o f

fiv e replicat e sample s take n in a n undergroun dparkin g garag e 6- 5 6- 5 Averag e compositio n o f particulat e lea dcompound s emitte di n aut o exhaus t 7 6- 6 6- 6 Effect s o f

agin g o n lea dcompound s i n sample s o f aut o exhaus t

a s determine db y electro n microprob e 6- 6 6- 7 Concentratio n rang e an dmea n EF crus t value s fo r

atmospheri c trac e metal s collecte dove r

th e Atlanti c nort ho f

30 ° N 6-1 0 6- 8 Lea daeroso l productio n in th e norther n hemispher e compare dwit h

lea dconcentration s i n Cam p Century , Greenland , sno w a t differen t time s 6-1 1 6- 9 Termina l velocitie s o f spherica l particle s o f

uni t densit y a t

groun d leve l 6-1 2 6-1 0 Summar y o f

fiel ddat afro mPal o Alto , Californi a6-1 7 6-1 1 Depositio n o f

lea da t th e Walke r

Branc hWatershed , 197 4 ...... . 6-1 7 6-1 2 Lea dcompound s identifie din roadsid e soil s b y X-ra y powde r

diffractio n technique s 6-2 1 7- 1 Numbe r

o f NAS N urba n station s whos e dat afal l withi n selecte dan nua l averag e lea dconcentratio n intervals , 1966-197 4 7- 2 7- 2 Numbe r

o f NAS N nonurba n station s whos e dat afal l withi n selecte d annua l averag e lea dconcentratio n intervals , 1966-197 4 7- 2 7- 3 Cumulativ e frequenc y distribution s o f quarterl y lea dmeasurement s a t urba n station s b y year , 197 0 throug h197 4 7- 2 7- 4 Cumulativ e frequenc y distribution s o f quarterl y lea dmeasurement s at nonurba n station s b y year , 197 0 throug h197 4 7- 2 7- 5 NAS N station s withannua l averag e lea dconcentration s > 3. 0 /xg/m 3 7- 3 xi xP.2 2

NumberPage 7- 6 Quarterl y an dannua l siz e distribution s o f lead-bearin g particle s fo r si x cities , 197 0 7- 5 7- 7 Lea din ai r

o n Mai n Street , Brattleboro , Vermont , Septembe r 1 2 an d 13 , 197 2 7- 5 7- 8 Airborn e lea dconcentration s a t 5

- an d20-f

t elevation s abov e stree t leve l 7- 6 7- 9 Monthl y averag e lea dconcentration s fo r 197 5 Lo s Angele s catalys t stud y 7- 6 7-1 0 Lea ddus t

o n an dnea r

heavil y travele droadway s 7- 7 7-1 1 Lea dconten t

i n o r o n roadsid e soi l an dgras s a s afunctio n o f distanc e fro mtraffi c an dgras s dept hin profil e 7- 7 7-1 2 Lea ddus t

i n residentia l area s 7- 8 8- 1 Accumulatio n o f certai n heav y metal s fro mseawate r b y fis h(Ammodytes an dClupea) an dapuffi n 8- 3 8- 2 Summar y o f

lea dconcentration s i n bir dorgan s an dtissue s fro marea s o f high-lea dan dlow-lea denvironment s 8- 4 8- 3 Mea n lea dconcentration s in organ s an dtissue s o f smal l mammal s fro mindicate darea s o f environmenta l lea dexposure s 8- 6 8- 4 Lea dconcentration s o f insect s a t

tw o distance s fro mahigh-traffic

volum e roa d(interstat e highway ) 8- 6 8- 5 Lea dconcentration s o f predominan t

organism s fro mth e rural , ur ban , an dcombine dcompartment s o f th e drainag e basi n o f th e Salin e Branc ho f

th e Vermilio n River , 11 1 8- 8 8- 6 Summar y o f

goldfis htoxicit y dat a8- 8 8- 7 Concentration s o f selecte dheav y metal s in fres hwate r an di n fresh

wate r alga l bloom s 8-1 2 10- 1 Lea dconten t

o f fresh , processed , an dcanne dfoodstuffs 10- 3 10- 2 Effec t

o f differen t diet s o n lea dabsorptio n expresse da s th e rati o o f mea n retentio n fo r

experimenta l an dcontro l subject s 10- 4 10- 3 Percen t

absorptio n o f

differen t lea dcompound s relativ e t o lea dace tat e 10- 4 11- 1 Enzyme s affecte db y lea di n anima l studie s 11- 2 1 1 - 2 Enzyme s affecte db y lea di n huma n studie s 11- 2 1 1 - 3 Compariso n o f

tes t result s in lea dan dcontro l group s 1 1 -2 2 11- 4 Summar y o f

result s o f

huma n studie s o n neurobehaviora l effect s a t "moderate " bloo dlea dlevel s 1 1 -2 7 1 1 - 5 Effect s o f

lea dexposur e o n locomoto r activit y i n laborator y animal s 1 1 -3 0 11- 6 Lea dexposur e an dresultin g bloo dlea dlevel s i n experiment s measurin g locomoto r

activit y in rat s 1 1 -3 2 1 1 - 7 Protocol s use dfo r th e stud y o f

anima l learnin g 1 1 -3 5 1 1 - 8 Stag e o f

learnin g 1.1-3 7 11- 9 In vivo effect s o f

lea dexposur e o n neurochemistr y 1 1 -3 9 11-1 0 Statistic s o n th e effec t o f lea do n pregnanc y 11-4 6 11-1 1 Reproductiv e performanc e o f F , lead-toxi c rat s 1 1 -4 9 12- 1 Analysi s o f

varianc e fo r

th e logarithm s o f

bloo dlea dvalue s fo r selecte dstudie s 12- 3 12- 2 Bloo dlea dlevel s o f remot e population s 12- 4 12- 3 Ag e an dsmoking-adjuste dgeometri c mea n bloo dlead s in urba n ver su s suburba n area s o f

thre e citie s : 12- 5 12- 4 Bloo dlea dconcentration s i n si x urba n an don e rura l population. . 12- 5 12- 5 Mea n bloo dlea dvalue s fo r childre n i n 1 4 intermediate-size dcitie s i n Illinois , 197 1 12- 6 x xNumberft*' 12- 6 Bloo dlea dlevel s (whol e blood ) i n childre n in U.S . smelte r an dcom pariso n towns , 197 5 12- 7 12- 7 Geometri c mea n an dgeometri c standar ddeviation s (i n parentheses ) o f bloo dlea dlevel s b y ag e an dstud y secto r 12- 7 12- 8 Proportio n o f

childre n withbloo dlea dvalue s betwee n 5 0 an d9 9 Mg/dl , b y age , Chicago , 1971-197 5 12- 7 12- 9 Mea n bloo dlea db y age , sex , an dG6P D statu s i n 155 9 urba n blac k childre n 12- 8 12-1 0 Geometri c mea n blood-lea dlevel s in Ne w Yor k Cit y lea dscreenin g progra m12- 8 12-1 1 Numbe r

o f children' s initia l screen s in Ne w Yor k Cit y program s b y race/ethnicit y an dyear , 1970-197 7 12- 9 12-1 2 Bloo dlea dlevel s in militar y recruits , b y rac e an dplac e 12- 9 12-1 3 Geometri c mea n bloo dlea dlevel s i n Ne w Yor k lea dscreenin g pro gram , 1970-1976 , fo r

childre n u p t o 7 2 month s o f age , b y rac e an d yea r 12-1 0 12-1 4 Mea n bloo dlea dlevel s fo r stud y an dcontro l groups , Houston... . 12-1 1 12-1 5 Arithmeti c an dgeometri c mea n bloo dlea dlevel s fo r Lo s Angele s an dLancaster , California , b y se x an dag e 12-1 1 12-1 6 Mea n ai r

lea dlevel s indoor s an doutdoor s at tw o traffi c densities , Dallas , Texas , 197 6 12-1 2 12-1 7 Soi l lea dlevel s b y traffi c densit y 12-1 2 12-1 8 Bloo dlea dconcentration s in relatio n t o soi l lea dconcentration s an d traffi c densit y 12-1 3 12-1 9 Bloo dlea dlevel s in childre n age d1 t o 5 in Newark , Ne w Jersey , in relatio n t o distanc e o f

residenc e fro mamajo r roadway , 197 1 . . 12-1 3 12-2 0 Geometri c mea n bloo dlea dlevel s b y are acompare dwit hestimate d ai r lea dlevel s fo r

1

- t o 9-year-ol dchildre n livin g nea r Idah o smelte r 12-1 5 12-2 1 Mea n bloo dlea dlevel s i n childre n livin g in vicinit y o f aprimar y lea dsmelter , 197 4 an d197 5 12-1 7 12-2 2 Mea n bloo dlea dlevel s in selecte dYugoslavia n populations , b y esti

mate dweekly , time-weighted , ai r lea dexposur e 12-1 8 12-2 3 Lea dconcentration s in air , dustfall , an dblood , Omaha , Nebraska , study , 1970-197 7 12-1 9 12-2 4 Geometri c mea n ai r an dbloo dlea dlevel s fo r fiv e city-occupatio n group s 12-2 1 12-2 5 Geometri c mea n ai r an dbloo dlea dvalue s fo r 1 1 stud y population s 12-2 2 12-2 6 Mea n ai r

an dbloo dlea dvalue s fo r fiv e zone s in Toky o stud y ... . 12-2 2 12-2 7 Lengt ho f

tim e neede dfo r

mea n bloo dlea dvalue s t o reac hspecifie d level s a t tw o exposur e level s 12-2 3 12-2 8 Estimate dbloo dlea dt o ai r lea dratio s fo r

fou r ai r lea dconcentra tion s 12-2 5 12-2 9 Yearl y mea n ai r

an dbloo dlea dlevel s o f blac k female s in relatio n t o distanc e o f

residenc e fro mabus y highwa y :.. . . 12-2 6 12-3 0 Bloo dan dai r

lea dlevel s b y se x in Finnis hpopulatio n stud y 12-2 7 12-3 1 Bloo dan dai r

lea ddat afro mclinica l stud y 12-2 8 12-3 2 Estimate dpercentag e o f populatio n exceedin g aspecifi c bloo dlea d leve l i n relatio n t o ambien t ai r lea dexposur e 12-2 8 12-3 3 Compariso n o f

bloo dlea dlevel s in childre n wit hai r lea dlevel s fo r 197 4 an d197 5 12-2 9 12-3 4 Mea n bloo dan dsoi l lea dconcentration s in Englis hstud y 12-3 0 12-3 5 Summar y o f

soi l lead/bloo dlea drelationship s 12-3 2

xx iP.2 4

NumberPage 

### 12-3 6 Bloo dleadlevel s o f 77 1 person s i

n relatio n t o leadconten t

o f drink

in g water , Boston , Massachusett s 12-3 3 12-3 7 Result s o

f screenin g andhousin g inspectio n i n childhoo dlead poisonin g contro l projec t

b y fisca l yea r 12-3 6 12-3 8 Geometri c mea

n bloo dlea

dlevel s o f childre n b

y parenta l employ

ment 12-3 7 12-3 9 Geometri c mea

n bloo dlea

dlevel s fo r childre n base don reporte doc cupatio n o

f father , histor

y o f pica , an ddistanc e o

f residenc e fro

m smelter 12-3 7 13- 1 Source s o

f leadfo r huma n exposure s 13- 2 13- 2 Summar

y o f lowes t observe deffec

t level s 13- 8 13- 3 Percentag e o

f subject s wit

hALA- U exceedin g 5 mg/ 1 fo r variou s bloo dleadlevel s 13-1 0 13-4 Estimate dpercentage s o f childre n wit

hEPexceedin g cut-of

f point s fo r variou s bloo dlea

dlevel s 13-1 1 13- 5 Populatio n andpercent distribution , urban an drural , b y race, 197 0 censu s 13-1 3 13- 6 Number

o f birth s b y rac e an dsiz e o

f populatio n 13-1 4 B- l Physica

l propertie s o

f inorgani c leadcompound s B- l B- 2 Temperatur e variatio n o f th e vapo r

pressure s o

f commo n leadcom pound s B- 2 C- 1 Summar

y o f monthl y averag e lea

dconcentration s foundi

n seven-cit

y study C- 2 C- 2 Seasona

l lea dconcentration s i

n Birmingham , Alabama , area , 1964-196 5 C- 2 C- 3 Leaddat afro

mKanawh aValle y Stud

y C- 3 C- 4 Dat aon lea

ddepositio n i

n 7 7 midwester

n citie s C- 3 C- 5 Leadconcentration s i n air determine db

y analysi s o

f suspende dpar ticulate , Souther

n Solan o County , California , March-May 1970 . C- 4 C- 6 Tota l leadan dlea dfallou t determine db

y analysi s o

f dustfal l sam ples , Souther

n Solan o County , California , June-September 197 0 C- 4 C- 7 Leadconcentration s i n suspende dparticulat e ai r sample s fro

mEl Paso , Texas , 197 1 C- 5 C- 8 Particulat e dat asummar y fro mHelen aValley , Montana, environ

mental pollutio n study C- 5 C- 9 Pea

k depositio n rate s o

f leadmeasure di

n Southeas t

Missour i C- 6 C-1 0 Atmospheri c leadconcentration s (24-hr ) i n th e Mez aValley , Yugoslavia , November

197 1 t o Augus t

197 2 C- 7 C-1 1 Compariso n of

leadlevel s i

n th e surrounding s o

f tw o leadindustry facilitie s an da

n urba n contro l are aC- 7 C-1 2 Leadconten t

o f soil nea r 3-year-ol dRussia

n smelter , E . Kazakhstan C- 8 C-1 3 Leadconten t

o f soi l i n vicinit y o f Russia n leadplan t

i n Kazakhsta

n C- 9

xx n

## ABBREVIATION S AN D SYMBOL S

A AA S AL A ALA D ALA S ALA- U 8-AL A APH A AST M AS V b.p . B.W . °C C a C d CD C (Ch 3 ) 4 P b (CH 3 ) 6 Pb 2 (C 2 H 5 ) 4 P b (C 6 H 5 ) 4 P b (C 2 H 5 ) 6 Pb 2 c m CN S 

### co 3 

### = C P CP G CP- U C u D A d l DN A EDT A E P EP A

° F Angstro m(10 1 0 meter )

Atomi c absorptio n spectroscop y Delta-aminolevulini c aci d Delta-aminolevulini c aci d dehydratas e Delta-aminolevulini c aci d synthetas e Delta-aminolevulini c aci di n urin e Delta-aminolevulini c aci d America n Publi c Healt h Associatio n America n Societ y fo r

Testin g an d Material s Anodi c strippin g voltammetr y Boilin g poin t Bod y weigh t Degree s Celsiu s (centigrade ) Calciu m Cadmiu m Cente r fo r Diseas e Contro l (Atlanta , Ga. ) Tetramethy l lea d(als o TM Lo r Me 4 Pb ) Hexamethy l lea d Tetraethy l lea d(als o TE Lo r Et 4 Pb ) Tetrapheny l lea d Hexaethy l lea d Centimete r Centra l nervou s syste m Carbonat e io n Coproporphyri n Coproporphyrinoge n Coproporphyri n in urin e Coppe r Dopamin e Decilite r Deoxyribonuclei c aci d Ethylenediaminetetraacetat e Erythrocyt e protoporphyrin ; als o erythrocyt e porphyri n U.S . Environmenta l Protectio n Agenc y Degree s Fahrenhei t FD A 59 F e Fe 2 0 3 FE P f t g GS H G-6-PD H h a 5-HIA A h r IAR C ICR P in i.p . K kca l RC R kg k m 1 LC , LC 5 0 m M ma x Me 3 PbA c (Me 3 Pb) 2 S Me V MEPP s m g M g mi n MME D ml m o m.p . Foo dan dDru g Administratio n

Radioisotop e o f

iro n Ferri c oxid e Fre e erthythrocyt e protoporphyrin ; als o fre e erythrocyt e porphyri n Foo t Gra m Glutathion e (reduced ) Glucose-6-phosphat e dehydrogenas e Hectar e 5-Hydroxyindol e aceti c aci d Hou r Internationa l Agenc y fo r Researc h o n Cance r Internationa l Radiologica l Protectio n Commissio n Inc h Intraperitonea l Potassiu m Kilocalori e Respirator y contro l rat e Kilogra m Kilomete r Lite r Concentratio n letha l t o 1 percen t o f recipient s Concentratio n letha l t o 5 0 percen t o f recipient s Mete r Mola r Maximu m Trimethy l lea dacetat e Trimethy l lea dsulfid e Meg aelectronvolt s (10 6 electronvolts ) Miniatur e end-plat e potential s Milligra m Magnesiu m Minut e Mas s media n equivalen t diamete r Millilite r Mont h Meltin g poin t XXll lP.2 6

M T N a NAD H NA S NAS N N E n g N i n m NO" 3 NS F NV S P P b 204p b Pb + + Pb- A Pb- B PbBr 2 PbBrC l Metri c to n

Sodiu m Reduced(hydrogenated ) nicotinamid e adenin e dinucleotid e Nationa l Academ y o f

Science s Nationa l Ai r

Surveillanc e Network s Norepinephrin e Nanogra m Nicke l Nanomete r Nitrat e io n Nationa l Scienc e Foundatio n Nonvolatil e solid s Phosphoru s Lea d Isotop e o f

Lea d( 2l0 Pb , etc. ) Diavalen t

lea dio n Concentratio n o f

lea din ai r Concentratio n o f

lea din bloo d Lea dbromid e Lea d(II ) bromochlorid e PbBrCl-NH 4 C I Lea dbromochloride-ammoniu m [Pb(C 2 H 3 0 2 ) 2 - 2Pb(OH) 2 ] PbCl 2 PbC0 3 

### PbCr6 4 PbF 2 Pb(N0 3 ) 2 Pb O PbO x (PbO) 2 Pb 3 0 4 Pb(OCOCH 3 ) 2 Pb(OH) 2 Pb(OH)B r Pb(OH)C l Pb(OH) 2 C0 3 PbO.PbS0 4 Pb 4 0(P0 4 ) 2 chlorid e

Basi c lea d(II ) acetat e Lea dchlorid e Lea dcarbonat e Lea dchromat e Lea dfluorid e Lea dnitrat e Lea doxid e Lea doxide s Lea doxid e dime r Lea d(IV ) oxid e Lea d(II ) acetat e Lea dhydroxid e Lea d(II ) hydroxybromid e Lea dhydroxychlorid e Basi c lea dcarbonat e Basi c lea dsulfat e Lea doxyphosphat e Pb(P0 3 ) 2 Pb 3 (P0 4 ) 2 Pb s (P0 4 ) 3 O H Pb S PbS0 4 PB G pC i PIX E P H PO ? P P pp b pp m PV C RB C RN A s.c . sc m se c SGO T SGP T S H S0 2 SO ? 85 S r STE L TE L TM L TV L USPH S Z n Zn S ZP P M g fi\ ju m > <

xxi v Lea dmetaphosphat e Lea dorthophosphat e Lea dhydroxqpmxqpqwz n Lea dsulfid e Lea dsulfat e Porphobilinoge n Picocuri e (IO" 12 curie ) Proton-induce dX-ra y emission s Lo g o f th e reciproca l o f

th e hydroge n io n concentratio n Phosphat e io n Protoporphyri n Par t pe r billio n Par t pe r millio n Polyviny l chlorid e Re dbloo dcell ; erythrocyt e Ribonuclei c aci d Subcutaneou s Standar dcubi c mete r Secon d Seru mglutami c oxaloaceti c transaminas e Seru mglutami c pyruvi c transaminas e Sulfhydry l Sulfu r dioxid e Sulfat e io n Radioisotop e o f

strontiu m Short-ter mexposur e limi t Tetraethy l lea d Tetramethy l lea d Threshol dvalu e limi t U.S . Publi c Healt hServic e Zin c Zin c sulfid e Erythrocyt e zin c protoporphyri n Microgra m Microlite r Micromete r Greate r tha n Les s tha n Approximatel y

## 1 . SUMMAR Y AN D CONCLUSION S

1. 1 INTRODUCTIO N Th e firs t portio n o f

thi s documen t

i s devote dt o lea din th e environment : it s physica l an dchemica l properties ; it s monitorin g an dmeasuremen t in variou s environmenta l media ; it s environmenta l sources , emissions , an dconcentrations ; an dit s trans por t an dtransformatio n withi n th e environmen t (Chapter s 3 throug h7) . Chapter s 8 throug h1 3 ar e concerne dwit hth e effect s o f lea do n ecosystem s and , mos t important , o n huma n health . Amon g th e question s tha t hav e bee n specificall y addresse di n thi s documen t

are : 1 . Wha t ar e th e source s o f

lea di n th e environ

ment ? 2 . Wha t ar e th e route s an dmechanism s b y whic hlea dfro mthes e source s enter s th e body ? 3 . Onc e lea denter s th e body , wher e i s i t deposited ? 4 . Onc e lea di s in th e body , wha t ar e it s healt h effects ? 5 . Ar e ther e group s withi n th e populatio n tha t ar e particularl y vulnerabl e t o lead ? 6 . Wha t i s th e magnitud e o f

th e ris k i n term s o f th e numbe r

o f person s expose din variou s subgroup s o f

th e population ? Thi s documen t

ha s bee n prepare dt o reflec t th e curren t stat e o f

knowledg e abou t

lea d— specifically , thos e issue s tha t ar e mos t

relevan t

t o establishin g th e objectiv e scientifi c dat abas e tha t will b e use dt o recommen da n ai r qualit y standar d fo r lea dtha t

wil l adequatel y safeguar dth e publi c health . 1.1. 1 Potentia l Exposur e t o Environmenta l Lea d Lea di s uniqu e amon g th e toxi c heav y metal s in tha t i t i s relativel y abundan t i n th e earth' s crust . Becaus e o f

it s eas y isolatio n an dlo w meltin g point , lea dwa s amon g th e firs t metal s t o b e use db y ma n thousand s o f

year s ago . Th e environmenta l signifi

canc e o f lea di s aresul t

bot ho f it s utilit y an do f

it s abundance . Worl dproductio n exceed s 3. 5 millio n tons/year , afa r large r quantit y tha n th e productio n o f an y othe r

toxi c heav y metal . Lea di s presen t

in food , water , air , soil , dustfall , paint , an dothe r

material s withwhic hth e genera l populatio n come s in contact . Eac ho f thes e repre sent s apotentia l pathwa y fo r huma n lea dexposur e vi ainhalatio n o r

ingestion . Th e actua l lea dconten t in eac hsourc e ma y var y b y severa l order s o f mag nitude . Potentia l exposur e pattern s ar e furthe r con founde db y huma n activit y pattern s an db y difference s betwee n indoo r an doutdoo r

environ

ments . Th e numbe r

an dexten t

o f variable s involve d mak e i t ver y difficul t

t o determin e th e actua l lea d intak e o f individual s in thei r

norma l environment . A s aresul t

o f centurie s o f

th e mining , smelting , an dus e o f

lea di n huma n activities , natura l back

groun dconcentration s ar e difficul t t o determine . Geochemica l dat aindicat e tha t th e concentration s o f lea di n mos t surfac e material s in th e Unite dState s rang e fro m1 0 t o 3 0 pp m(figlg). Trac e amount s o f lea doccu r

naturall y in ai r

an dwate r

a s aresul t

o f win dan drai n erosion , an din ai r a s aresul t

o f volcani c dusts , fores t

fires , se asalt , an dth e deca y o f radon . Natura l backgroun dconcentration s o f air

born e lea dhav e bee n estimate dt o approximat e 0.000 6 fig Pb/m 3 o f

ai r (o r 5 x 10 7 /xg Pb/ g air) . Natura l concentration s in fres hwate r hav e bee n esti

mate dt o b e abou t

0. 5 /xg/lite r

o f wate r (abou t 5 x IO 4 fig Pb/ g water ) an din ocea n wate r abou t 0.0 5 fig Pb/lite r

o f wate r (abou t 4. 9 x 10" 5 fig Pb/ g water) . A s aconsequenc e o f th e extensiv e an d divers e use s o f

lead , presen t

concentration s o f

lea d in air , soil , an dwate r

ar e substantiall y highe r tha n thes e estimate dbackgroun dlevels . Nonurba n lea d concentration s averag e 0. 1 fig Pb/m 3 o f ai r (abou t 8 x 10 5 fig Pb/ g air) . Concentration s o f airborn e lea d in U.S . cities , a t

site s no t

conspicuousl y influence d b y majo r sources , averag e 1 fig Pb/m 3 o f ai r ( 8 x IO 4 fig Pb/ g air) . Expresse do n aweigh t basi s with respec t t o th e tota l suspende dparticulat e (TSP ) in th e air , thi s amoun t

i s approximatel y equivalen t t o 10 " fig Pb/ g TSP . Th e shap e o f

building s i n urba n area s ma y caus e larg e horizonta l an dvertica l variation s in lea dcon 1- 1P.2 8

centrations . I n th e absenc e o f suc hstructures , th e vertica l gradien t

woul dusuall y b e relativel y small . Durin g period s o f

maximu mtraffi c densit y o n free

ways , airborn e concentration s o f lea dimmediatel y adjacen t t o th e freeway s may reac h2 0 /xg/m 3 fo r a few hours . I n th e immediat e vicinit y o f larg e station

ar y source s havin g n o ai r pollutio n controls , con centration s o f

airborn e lea dma y reac h30 0 /xg/m 3 unde r unfavorabl e meteorologica l conditions . Consequently , exposur e vi ainhalatio n o f airborn e inorgani c lea dparticulate s ma y var y b y afacto r o f at leas t 100 , dependin g o n locatio n an dactivit y pat terns . Th e smal l numbe r o f indoo r ai r lea dstudie s conducte dhav e show n indoo r concentration s t o b e one-thir do r

les s th e leve l measure doutdoors . In

doo r level s var y widel y dependin g o n typ e o f struc ture , ai r conditioning , wind , etc . Dus t i s ageneri c ter man dconsequentl y imprecis e whe n use dt o describ e potentia l huma n exposure . Dus t in th e popula r

sens e usuall y refer s t o soli dpar ticle s tha t

hav e settle do n asurfac e an dtha t ca n b e readil y redisperse din th e atmosphere . I n a n aero metri c sense , dus t

i s soli dparticle s suspende din th e atmosphere ; consequently , i t i s an integra l par t

o f tota l suspende dparticulates . I n an occupationa l sense , dus t

may encompas s eve n large r particle s dis

charge dint o th e wor k

environmen t

b y mechanica l means . Dustfal l i s ameasur e o f th e settle dparticu

late , o r tha t deposite din o r

o n th e collectio n devices ; thu s dustfal l i s mor e closel y relate dt o th e popula r definitio n o f

dust . I n thi s document , dustfal l i s treate da s aseparat e pathwa y for potentia l ex posur e t o lea dvi aingestio n o f thes e settle dparticles , bu t onl y in aqualitativ e manner . Lea dconcentration s in dustfal l var y widel y with th e typ e an ddistributio n o f sources . Th e highes t value s occu r

in th e immediat e vicinit y o f source s an d diminis hrapidl y withdistance . Potentia l exposur e t o lea di n dustfal l depend s o n th e tota l accumulatio n o f dus t i n accessibl e areas . Th e accumulatio n de

pend s o n th e depositio n rat e an dth e frequenc y an d efficienc y wit hwhic haccessibl e surface s ar e cleaned . Lea daccumulatio n resultin g fro mdeposi

tio n fro mth e ai r

may b e augmente din th e home s o f lea dworker s b y transportatio n o f lead-containin g dust s fro mth e workplace . Th e leve l o f accumulate d lea dpotentiall y availabl e bot hindoor s an dout door s clearl y ma y var y b y on e t o tw o order s o f mag nitude . Concentration s o f

lea din solutio n in mos t urba n wate r supplie s ar e belo w 1 0 /xg Pb/lite r o f wate r (0.0 1 fig Pb/ g water) , bu t som e value s >5 0 /xg/lite r (th e U.S . Publi c Healt hServic e standar dfo r lea din drinkin g water ) hav e bee n reported . Suspende d

solid s contai n th e majo r fractio n o f

lea din rive r waters . Concentration s o f lea di n ta p wate r

ma y b e considerabl y highe r

tha n thos e i

n municipa l sup plies . Lea dvalue s a s hig ha s abou t 200 0 /xg/lite r hav e bee n reporte dfo r home s withlea dpipe s an d lead-line dstorag e tanks . Se aspray , rainwate r

leaching , an dflakin g pain t fro molde r

building s ca n contribut e significantl y t o lea dlevel s i

n adjacen t

soil . Direc t

ingestio n o f

th e soi l o r o f re-entraine ddust , a s wel l a s ingestio n o f th e pain t chip s themselves , constitut e a n importan t sourc e o f lea din area s wher e thes e condition s exist . Th e contributio n o f

foo dt o huma n exposur e t o lea di s highl y variabl e an dno t wel l quantified . Esti

mate s o f dail y intak e var y fro mabou t 10 0 t o 35 0 fig Pb/day . Recen t

studie s i n th e Unit dState s estimat e th e adult s inges t

abou t 20 0 fig Pb/da y i n food . Beverage s an dfood s tha t ar e store din lead-soldere d can s o r store do r

serve din lead-glaze dpotter y hav e bee n identifie da s havin g hig hlea dcontent . Pro

cesse dmil k

ha s bee n reporte dt o contai n mor e lea d tha n fres hcow' s mil k

—abou t 2 0 t o 4 0 /xg/lite r compare dt o abou t

5 t o 1 0 /xg/liter , respectively . If thes e value s ar e correct , processe dmil k coul db e a significan t

sourc e o f

lea dexposur e fo r

infants . Fo r adults , illicitl y distille dwhiske y an dol dauto mobil e batterie s use da s hom e heatin g fuel represen t tw o nonindustria l source s o f over t lea dpoisoning . O f muc hgreate r

significanc e a s ahealt hproblem , however , ar e variou s source s o f occupationa l ex posure . Worker s involve din uncontrolle d(withou t pollu

tio n controls ) mining , smelting , an dmanufacturin g processe s wher e lea di s used , hav e th e highes t leve l o f potentia l exposure . Althoug hoccupationa l condi

tion s hav e generall y bee n substantiall y improved , i n som e case s lea dconcentration s i n th e ai r i n wor k place s hav e bee n measure da t 100 0 /xg/m 3 o r greater . Th e majo r

occupationa l exposur e problem s occu r wher e adequat e hygien e program s hav e no t bee n implemente do r

wher e individual s fai l t o tak e th e recommende dprecautions . Th e majo r rout e o f occupationa l exposur e i s th e inhalatio n o f dus t an d fumes ; in addition , dus t transporte do n clothin g fro mth e wor k

plac e t o th e hom e o r

automobil e ma y b e asignifican t

pathwa y o f

exposur e fo r

worker s an d thei r families . 1.1. 2 Source s o f

Environmenta l Lea d Th e mining , smelting , an dus e o f lea din huma n activitie s ha s significantl y altere dth e natura l distri

butio n o f

lea di n th e environment . Contaminatio n 1- 2ha s occurre dprimaril y i n th e vicinit y o f

source s an d i n densel y populate dareas . Th e lea duse di

n gasolin e antiknoc k

additive s represent s amajo r

fractio n o f

th e tota l U.S . lea d consumption , an dmoto r vehicl e emission s con stitut e th e majo r

sourc e o f

lea demission s t o th e at mosphere . I n 1975 , som e 189,00 0 M T o f lea d(1 6 percen t o f tota l production ) use din antiknoc k com pound s wer e converte dt o 142,00 0 M T o f at mospheri c emission s (8 8 percen t o f tota l lea demis

sions) . A s aresul t

o f legislatio n settin g amaximu m limi t o n th e lea dconten t

o f gasoline , th e productio n an dus e o f

alky l lea dadditive s ha s decrease din re cen t year s an dwil l probabl y continu e t o d o so . Base do n 197 5 estimates , combustio n o f wast e oi l an dincineratio n o f

soli dwast e ar e th e majo r contri

butor s o f

lea demission s fro mstationar y source s (12,06 0 MT/year) . Thi s figur e represent s onl y tha t portio n o f

wast e oi l tha t

i s reprocesse dan dburne d in oil-fire do r

coal-fire dboiler s an dmunicipa l in

cinerators . Othe r

stationar y source s o f

lea demis

sion s includ e iro n an dstee l productio n in plant s withpoo r pollutio n controls , primar y an dsecondar y smelting , batter y manufacturing , an dlea dalky l manufacturing . Lea dtha t may b e emitte dt o th e environmen t

fro mthes e operation s include s tha t in stac k emission s an dfugitiv e dusts . Contaminatio n fro mth e majo r

stationar y emitter s may determin e environmenta l concentration s fo r aradiu s o f

severa l kilometer s aroun dth e sources . Fugitiv e dust s ma y resul t i n ahig hleve l o f

contaminatio n in th e im

mediat e vicinit y o f

small , uncontrolle dbatter y re cyclin g operations . I n term s o f

mas s balance , lea dfro mmobil e an d industria l source s i s transporte dan ddistribute d mainl y vi ath e atmosphere . Certai n wast e disposa l operation s tha t

discharg e larg e amount s o f lea dint o soi l an dwate r

resul t onl y in highl y localize dcon tamination . Lea di s emitte dt o th e atmospher e pri

maril y i n th e for mo f inorgani c particulates ; however , smal l amount s o f organi c vapor s hav e bee n reporte di n th e vicinit y o f gasolin e servic e stations , garages , an dheav y traffi c areas . Thes e organi c vapor s underg o photochemica l decompositio n in th e atmosphere , bu t

the y ma y als o b e adsorbe do n dus t particl e surfaces . Base do n th e limite ddat aavailable , it i s estimate d tha t 7 5 percen t

o f th e particulat e lea demitte dfro m automobile s i s remove dfro mth e atmospher e i n th e immediat e vicinit y o f

traffi c sources . Particle s smalle r

tha n thos e fro mmobil e sources , an demission s fro mtal l stack s will remai n airborn e longe r an db e transporte dove r greate r distances . Submicro n particle s ma y resid e in th e atmospher e a

wee k o r mor e befor e the y ar e remove db y dr y depositio n (diffusio n an dinertia l mechanisms ) an d b y precipitation . Th e tendenc y towar dunifor mver tica l an dhorizonta l distributio n (mixin g wit hcon comitan t distribution ) increase s wit han increas e in residenc e time . Th e chemistr y o f

lea daerosol s discharge dint o th e environmen t

ha s no t bee n studie da s extensivel y a s th e chemistr y o f

som e o f th e othe r

majo r ai r pollu

tants . Muc ho f

th e wor k

o n lea dparticulat e chemis

tr y befor e 197 3 wa s limite dt o elementa l analyse s an ddi dno t

includ e analyse s o f

associate dions . In

formatio n fro melementa l analyse s i s no t sufficien t t o permi t

athoroug hexaminatio n an dunder

standin g o f

(1 ) transformatio n an dtranspor t pro cesse s tha t

occu r amon g th e environmenta l media , (2 ) mobilit y o f

lea din soils , (3 ) uptak e an ddistri

butio n o f lea din plants , an d(4 ) th e overal l impac t o f lea dpollutio n o n huma n healt han decosystems . Informatio n i s neede do n th e chemica l form s an d interaction s o f

lea dan dit s tendenc y t o formcom pound s o f

lo w solubilit y withth e majo r anions . Onl y afew studie s hav e bee n conducte do n th e chemica l form s o f lea din soi l an dplants . The y sho w tha t th e principa l lea dformfoun din soil s i s sulfate , an dth e principa l formfoun din plant s i s phosphate . Lea ddissolve dfro mprimar y lea dsulfid e or e tend s t o combin e wit hcarbonat e o r sulfat e ion s t o formrelativel y insolubl e lea dcarbonat e o r lea dsul

fate , o r t o b e absorbe db y ferri c hydroxide . Th e amoun t o f lea dtha t

ca n remai n in solutio n in wate r i s afunctio n o f

th e concentratio n o f

othe r ions , especiall y hydroge n ions . 1.1. 3 Monitorin g o f

Environmenta l Lea d Lea dha s bee n monitore din air , water , soil , food , an dbiologica l sample s suc ha s bloo dan durin e fo r man y years , bu t

th e accurac y o f

th e earl y samplin g an danalytica l technique s wa s quit e low . Conse

quently , thes e earlie r

dat aca n b e use donl y in a qualitativ e o r

semiquantitativ e manner . Externa l contaminatio n ha s bee n th e majo r proble mi n al l samplin g procedures , particularl y in samplin g fo r bloo dlea danalyses . Samplin g an danalytica l techni

que s fo r environmenta l lea dhav e enjoye dcon siderabl e improvemen t

an drefinemen t

i n th e pas t few years . Som e o f

th e bes t methods , however , ar e tediou s an dexpensiv e an dar e availabl e onl y in relativel y specialize dlaboratories . Thos e analytica l technique s tha t

ar e les s sophisticate dproduc e result s o f limite dvalue . Th e capabilit y no w exist s fo r achievin g hig hprecisio n in lea dmonitoring ; bu t i n 1- 3P.3 0

genera l practice , precis e an daccurat e result s ar e difficul t t o obtain , particularl y for biologica l sam ples . Atomi c absorptio n spectroscop y i s th e mos t successfu l analytica l metho duse di n recen t years . Th e primar y proble mface di n environmenta l monitorin g —

tha t is , samplin g an danalysi s —i s t o determin e th e typ e o f

monitorin g procedure s t o b e use dt o accomplis hspecifi c objectives , an dt o estab

lis han dmaintai n adequat e qualit y control . Ambien t ai r monitorin g procedure s designe d specificall y fo r

assessin g populatio n exposur e pat tern s presen t

particularl y difficul t

problems . Tota l mas s concentration , particl e siz e distribution , an d chemica l compositio n o f lea daerosol s al l var y con siderabl y wit hspac e an dtime . I n usin g atmospheri c measurement s t o determin e populatio n exposures , huma n activit y pattern s ar e afurthe r complication . Thu s th e relationshi p betwee n measurement s o f at mospheri c concentratio n o f lead , duratio n o f

ex posure , an dincrementa l change s in bloo dlea dlevel s i s no t constant . Althoug hmeasurement s o f at mospheri c lea dlevel s ar e an essentia l ingredien t i n populatio n exposur e assessment , othe r indice s o f

ex posur e suc ha s bloo dlea dan dfre e erythrocyt e porphyri n (FEP ) level s ar e als o essentia l fo r th e characterizatio n o f

huma n populatio n exoosures . Bloo dlea dma y b e measure db y severa l genera l technique s tha t

presentl y appea r

t o b e satisfactor y in th e hand s o f

qualifie danalyst s wh o hav e asophisti

cate dtechnica l appreciatio n o f th e man y problem s associate dwit hmeasurin g a n elemen t tha t i s bot h presen t a t trac e level s an dubiquitousl y distribute d a s acontaminant . Extensiv e interlaborator y com parison s hav e demonstrate dth e nee dfo r standardiz

in g methodology , usin g referenc e standards , an dob

tainin g bloo dlea ddetermination s fro mthos e laboratorie s havin g highl y skille dpersonne l ac custome dt o handlin g alarg e numbe r o f samples . Th e presen t

existenc e o f

anumbe r

o f regiona l an d nationa l analytica l proficienc y testin g program s will hel p improv e th e qualit y o f analysi s an dth e reliabilit y o f

consequen t

clinica l an depidemiologi

ca l data . Measurement s ofbiologica l indicator s suc h a s erythrocyt e porphyrin , 8-ALA , an d8-ALA D ar e als o aproblem . A standardize dmetho dexist s fo r urinar y ALA , an daprogra mi s underwa y in th e Unite dState s t o evaluat e standardization s o f methodolog y fo r

determinin g erythrocyt e porphyrin . 1. 2 EFFECT S O F LEA D O N MA N AN D HI S ENVIRONMEN T I n th e summar y materia l presente di n th e preced

in g section , attentio n wa s directe dt o al l th e ex posur e aspect s o f

lead . Th e biologica l aspect s o f th e lea dpollutio n proble mar e discusse din thi s section . Thes e aspect s includ e no t onl y th e effect s o f

lea do n man , bu t als o it s effect s o n amyria do f ecosystem s tha t suppor t ma n an dcontribut e t o hi s genera l welfare . 1.2. 1 Effect s o f

Lea d o n Ma n Th e effect s o f

lea do n ma n ar e summarize din se quentia l statement s o f

presen t knowledg e concern ing : 1 . Man' s metabolis mo f lead . 2 . Biologica l an dadvers e healt heffect s i n man . 3 . Effect s o f

lea do n populations . 4 . Risk s ma n incur s fro mexposur e t o lead . 1.2.1. 1 METABOLIS M Metabolism , a s discusse dhere , encompasse s th e physiologica l processe s in ma n tha t relat e t o absorp

tion , distribution , excretion , an dne t retention . I t ca n b e discusse di n term s o f route s o f

lea dexposur e an dth e physiologica l distinction s existin g withi n certai n segment s o f

th e populatio n tha t

modif y thes e processes . Specia l attentio n i s focuse do n th e factor s tha t may plac e th e developin g fetu s an dth e chil di n acategor y o f

highe r ris k tha n th e adult . Nearl y al l lea dexposure s resul t fro minhalatio n an dingestion . Th e quantitie s o f lea dabsorbe dvi a thes e route s ar e determine db y man y factor s suc ha s th e physica l an dchemica l formo f th e lead , an dth e nutritiona l status , metaboli c activity , an dpreviou s exposur e histor y o f

thos e exposed . Clinica l studie s o n th e despositio n o f airborn e lea dparticulat e matte r in th e huma n respirator y trac t sugges t tha t 3 0 ± 1 0 percen t

o f th e ambien t

ai r lea dparticulate s inhale dwil l b e deposited . O f th e lea dthu s deposite din th e respirator y tract , it ha s bee n estimate dtha t

a s muc ha s 5 0 percen t

o r mor e i s absorbe dan denter s th e bloo dstream . Thi s deposi

tio n ma y var y considerably , dependin g o n particl e siz e an dpatter n o f

respiration . Par t

o f th e fractio n deposite din th e respirator y tract , tha t portio n remove dvi ath e mucociliar y escalator , i s swallowe d an denter s th e gastrointestina l tract . Anima l studie s sugges t tha t th e relativ e efficienc y o f lun g clearanc e mechanism s ma y b e impaire da t hig hlevel s o f

air

born e lead . I n children , approximatel y 4 0 percen t o f th e lea d take n int o th e gastrointestina l trac t i s absorbed , wherea s th e correspondin g valu e fo r adult s i s abou t 1 0 percent . I n on e stud y assessin g ne t gastro intestina l absorption , a n invers e relationshi p be

1- 4P.3 1

twee n calciu mintak e an dlea dabsorptio n wa s shown . Thi s relationshi p ha s als o bee n demonstrate d in experimenta l animals . I n discussin g th e route s b y whic hma n ma y b e ex pose dt o environmenta l lead , it i s importan t

t o dis

tinguis hbetwee n primar y an dsecondar y exposur e t o atmospheri c lead . Primar y exposur e i s direct , an d secondar y i s indirect . Primar y exposur e t o airborn e lea dconsist s o f

it s direc t

inhalation , wherea s sec ondar y exposur e t o airborn e lea dconsist s o f inges

tio n o f lea dtha t

i s o f atmospheri c origi n (tha t is , lea dtha t i s transporte db y th e airborn e rout e t o th e ingeste dmaterial) . Lea dma y contaminat e foodstuffs b y atmospheri c fallout , wit hsubsequen t adsorptio n ont o plan t sur face s o r absorptio n int o plants . Thi s contaminatio n ma y involv e primar y foo d(plant s consume db y man ) o r anima l foo dcrops . Soi l lea dtake n int o plant s ma y com e fro matmospheri c fallou t o r fro m leachin g fro mnatura l a s wel l a s industria l sources . Th e absorptio n o f

soi l lea db y plants , however , i s though t t o b e relativel y poor , althoug hdat ao n lea d accumulatio n in tre e ring s sugges t tha t absorptid n fro msoi l may occu r

in a t leas t som e plants . I n an y case , th e contributio n o f ai r lea dt o foo dlea dlevel s i s probabl y smal l o n th e basi s o f anationwid e foo d distributio n system ; bu t adequat e quantificatio n doe s no t yet exis t t o allo w precis e statement s o n thi s poin t t o b e made . I t

i s clear , however , tha t

commer cia l processin g raise s th e lea dconten t o f foo dsignifi

cantly . Anothe r importan t

depo t o f lea din th e environ

men t i s soi l o r

dust . Th e ultimat e sourc e o f thi s lea d varie s fro mplac e t o place ; i t ca n b e dustfal l fro mth e atmospher e (comin g fro meithe r stationar y o r mobil e sources) , o r

it ca n b e soi l o r

dus t int o whic h leade dpain t

ha s eroded . Thi s exposur e rout e i s though t t o b e mor e importan t

fo r childre n tha n fo r adults . Studie s hav e consistentl y show n association s betwee n soi l o r

dus t lea dlevel s an dbloo dlea d level s i n childre n whe n suc hexposure s excee d100 0 ppm . I t i s though t

tha t lea dreache s th e childre n throug hthei r

norma l mouthin g behavior . Lea di s picke du p o n children' s hand s throug hthei r pla y an d i s the n transferre dt o thei r mouth s b y thei r

custom ar y habi t

o f puttin g thei r

hands , objects , an d material s i n thei r

mouths . Ther e i s evidenc e demon

stratin g arelationshi p betwee n dus t lea dan dlea do n fingers , bu t

a s ye t ther e i s n o direc t

evidenc e linkin g lea do n fingers wit hlea di n th e blood . I n childre n withpica , however , th e importanc e o f thi s sourc e coul db e greatl y magnified . I t ha s bee n show n repeatedl y tha t level s o f lea din bloo dincreas e whe n ora l intak e increases , bu t

studie s d o no t

sho w aprecise , quantitativ e expres sio n o f thi s relationship . Rather , anumbe r o f studie s sho w that , withsustaine ddail y ingestio n o f 100 /xg o f lead , th e maximu mincreas e in steady-stat e level s o f bloo dlea drange s fro m6 t o 1 8 /xg/dl . Thes e variation s probabl y relat e t o nutritiona l factors , biologica l variability , unreporte dsource s o f ex posure , difference s in analytica l techniques , o r pre viou s exposur e histor y —o r t o acombinatio n o f thes e factors . Sinc e children , particularl y infants , absor b alarge r

percentag e o f

lea dtha n adult s do , th e relativ e contributio n o f ora l intak e i s undoubt

edl y greate r

fo r them . Becaus e o f

highe r metaboli c activity , childre n als o inhal e relativel y mor e air

born e lea dtha n d o adults . Therefore , th e contribu

tio n o f airborn e lea dt o tota l lea dintak e ma y b e greate r in childre n tha n i n adults , bu t on e mus t

kee p in min dtha t

childre n als o ea t

correspondingl y mor e o n abod y weigh t

basis . A numbe r

o f experimenta l anima l studie s hav e assesse dth e effect s o f

nutritio n an dothe r

factor s o n gastrointestina l absorptio n a s reflecte db y bloo d lea dlevels . I t

i s clea r fro mthes e studie s tha t th e statu s o f essentia l nutrient s suc ha s calcium , iron , phosphorus , fat , an dprotei n i s ver y important . Th e absorption , distribution , an daccumulatio n o f lea din ma n i s convenientl y describe db y athree

compartmen t

model . Th e first

compartment , cir

culatin g re dbloo dcells , distribute s lea dt o th e othe r two , sof t tissue s (primaril y live r an dkidney ) an d bone , wher e it

accumulates . Thi s accumulatio n begin s in feta l lif

e a s aresul t

o f transplacenta l trans fer . I n nonoccupational ^ expose dadults , suc h storag e approache s 9 5 percen t o f th e tota l bod y burden . Th e skeleto n i s arepositor y o f lea dtha t

re flect s th e long-ter mcumulativ e exposur e o f th e in

dividua l ; bod y fluid s an dsof t tissue s reflec t

mor e re cen t exposure . Sinc e th e nonaccumulatin g bod y burde n i n sof t tissue s ha s agreate r

toxicologica l significanc e tha n tha t fractio n sequestere din bone , th e mobilizabl e lea dburde n i s amor e importan t concep t tha n tota l bod y burden . I n thi s connection , chelatabl e urinar y lea dha s bee n show n t o provid e a n inde x o f th e mobil e portio n o f

th e tota l bod y burden , a s ha s th e lea dleve l in blood , whic hi s th e mor e generall y use d indicato r o f interna l dose . Ther e i s atim e fram e i n whic hchange s in ex posur e registe r

a s aperturbatio n in th e bloo dlea d level . Clinica l studie s sho w tha t (1 ) acontrolle d dail y intak e result s in aconstan t concentratio n o f bloo dlea dafte r

11 0 days , dependin g o n th e ex 1-5P.3 2

posur e setting , an d(2 ) asingle , acute , controlle dex posur e yielde dabloo dlea dhalf-lif e o f abou t 2 day s compare dt o approximatel y 1 7 day s in th e cas e o f repeate dexposures . Followin g cessatio n o f exposur e afte r lon g exposur e period s (e.g. , years) , however , th e half-lif

e o f bloo dlea dca n b e expecte dt o b e sub

stantiall y longe r

tha n 1 7 days . Feca l excretio n represent s th e majo r rout e b y whic hingeste dlea di s eliminate dfro mth e body . Thoug hexcretio n b y thi s rout e i s usuall y muc h greate r tha n b y urinar y elimination , th e tota l fecal lea dconten t

include s unabsorbe dlea da s it s majo r component . 1.2.1. 2 BIOLOGICA LAN D ADVERS E HEALT H EFFECT S O FLEA D I N MA N Ther e ar e variou s physiologica l level s an dex posur e range s a t

whic hth e effect s o f

lea di n ma n oc cur . Furthermore , lea daffect s ma n at th e sub

cellular , cellular , an dorga n syste mlevels . Amon g subcellula r

components , bot hnucle i an d mitrochondri agenerall y sho w th e mos t pronounce d response s t o cellula r invasio n b y lead . Th e mitochondria , however , ar e mos t vulnerabl e an d sustai n th e greates t

functiona l impairment . Mitochondria l injury , bot hi n term s o f cellula r energetic s an dmorphologica l aberration , ha s bee n show n in anumbe r

o f experimenta l animals . I n man , th e evidenc e fo r

mitochondria l impairmen t ha s bee n morphologica l rathe r

tha n functional . Thos e sub

cellula r change s observe dar e primaril y th e develop

men t o f nuclea r inclusio n bodie s in kidne y cell s a s wel l a s mitochondria l change s in rena l tubula r cell s in person s expose doccupationally . An y discussio n o f

th e subcellula r

effect s o f

lea d mus t conside r th e questio n o f

chromosoma l aberra

tion s an dcarcinogenesis . A t th e presen t

time , n o conclusiv e statement s ca n b e mad e abou t th e induc

tio n o f chromosoma l damag e b y lead . Th e literatur e o n thi s issu e eithe r

yield s conflictin g informatio n o r describe s studie s tha t

ar e difficul t

t o compar e with eac hother . Som e experimenta l anima l studie s relat e th e developmen t

o f cance r t o relativel y hig hdose s o f lead , bu t a s i s tru e i n th e cas e o f

othe r suspecte dcar cinogens , ther e ar e n o dat acorroboratin g thes e find

ings i n man . Amon g th e systemi c an dorgani c effect s o f lead , importan t

area s ar e it s hematologic , neurobe

havioral , an drena l effects . Attentio n mus t als o b e given , however , t o th e effect s o f lea do n reproduc

tio n an ddevelopmen t

a s wel l a s it s hepatic , en docrine , cardiovascular , immunologic , an dgastro intestina l effects . A numbe r o f significan t

effect s o f

lea do n th e hematopoieti c syste mi n human s hav e bee n observe d in lea dpoisoning . Thes e effect s ar e prominen t i n clinica l lea dpoisonin g bu t ar e stil l presen t

t o a lesse r degre e in person s wit halowe r leve l o f lea d exposure . Anemi ai s aclinica l featur e o f lea dintoxication , resultin g fro mbot hincrease derythrocyt e destruc

tio n an ddecrease dhemoglobi n synthesis . I n children , athreshol dbloo dlea dleve l fo r produc

tio n o f thes e symptom s o f

anemi ai s approximatel y 4 0 fig Pb/dl , an dth e correspondin g valu e fo r adult s appear s t o b e 5 0 /xg Pb/dl . Hemoglobi n synthesi s i s impaire db y lea dvi ain

hibitio n o f

synthesi s o f

th e globi n moiet y an dinhibi

tio n a t severa l step s in th e synthesi s o f heme . Th e ste p mos t

sensitiv e t o lea din th e hem e syntheti c pathwa y i s tha t

mediate db y th e enzym e 8-aminolevulini c aci ddehydratas e (8-ALAD) , whic hconnect s tw o unit s o f 8-aminolevulini c aci d (8-ALA ) t o formporphobilinogen . Th e resul t i s an increas e in plasm aleve l an denhance durinar y ex cretio n o f

8-ALA . Als o inhibite db y lea di s th e in

corporatio n o f

iro n int o protoporphyri n t o for m heme , th e prostheti c grou p o f hemoglobin . Thi s result s in th e accumulatio n o f coproporphyrin , whic hi s excrete din th e urine , an do f protopor phyrin , whic hi s retaine din th e erythrocytes . Th e overal l effec t

o f lea di s ane t

decreas e in hem e syn thesis . (Thi s als o derepresse s 8-AL A synthetase , th e enzym e involve din th e firs t ste p o f hem e synthesis. ) Inhibitio n o f

8-ALA D occur s at

extremel y lo w bloo dlea dlevel s an dha s bee n show n t o star t at a bloo dlea dleve l a s lo w a s 1 0 /xg/dl . Thoug hth e health-effec t

significanc e o f

inhibitio n a t

abloo d leve l o f 1 0 /xg/d l i s ope n t o debate , th e increase d urinar y 8-AL A excretio n tha t occur s withincreasin g inhibitio n at

4 0 /xg/d l i s accepte da s ameasur e o f probabl e physiologica l impairmen t in vivo. Thi s threshol dleve l fo r

urinar y 8-AL A excretio n (4 0 /xg/dl ) appear s t o b e tru e fo r bot hadult s an d children . A n increas e i n fre e erythrocyt e protoporphyri n (FEP ) occur s a t

bloo dlea dlevel s o f

1 6 /xg/d l in children . I n adul t

females , thi s threshol di s probabl y similar . I n adul t

males , th e valu e i s 2 0 t o 2 5 /xg/dl . Th e precis e threshol dfo r coproporphyrin , whil e no t wel l established , i s probabl y simila r t o tha t fo r 8-ALA . Elevatio n o t

fre e erythrocyt e protopor phyri n ha s th e sam e implication s o f physiologica l impairmen t

in vivo a s urinar y 8-ALA . T o th e exten t tha t th e protoprophyri n elevatio n i s alikel y indica

to r o f th e impairmen t

o f mitochondria l functio n i n 1- 6erythroi dtissue , it ma y b e eve n mor e important . Fo r thes e reasons , physician s wh o participate din th e developmen t

o f th e 197 5 statemen t

b y th e Cente r

fo r Diseas e Contro l an dth e America n Academ y o f Pediatric s reache daconsensu s tha t elevate dFE P shoul db e use da s a n indicato r o f increase dexposur e t o lead . Th e effect s o f

lea do n th e nervou s syste mrang e fro macut e intoxicatio n an dfata l encephalopath y t o subtl e behaviora l an delectrophysiologi c change s as sociate dwit hlowe r

leve l exposures . Change s throughou t

th e rang e o f

effect s ar e relate dt o bloo d lea dlevels . I t woul dappea r

tha t surprisingl y lo w level s o f bloo dlea dma y sometime s b e associate dwithth e mos t extrem e effect s o f

lea dpoisonin g —servere , ir

reversibl e brai n damag e a s indexe db y th e occur renc e o f acut e o r chroni c encephalopath y symptom s and/o r death . Thoug hfor

mos t adult s suc hdamag e doe s no t occu r unti l bloo dlea dlevel s substantiall y excee d120 /xg/dl , som e evidenc e suggest s tha t acut e encephalopath y an ddeat hma y occu r in som e adult s at bloo dlea dlevel s slightl y belo w 10 0 /xg/dl . Fo r children , th e effectiv e bloo dlevel s fo r producin g en cephalopath y o r

deat har e lowe r

tha n fo r

adults , withsuc heffect s bein g see n somewha t mor e often , startin g a t

approximatel y 10 0 /xg/dl . Again , however , evidenc e exist s fo r th e occurrenc e o f encephalopath y in aver y fe w case s at

lowe r levels , dow n t o abou t

8 0 /xg/dl . I t shoul db e note dtha t

onc e encephalopath y oc curs , deat hca n b e afrequen t outcome , regardles s o f th e leve l o f

medica l interventio n a t th e tim e o f

th e acut e crisis . I t

i s als o crucia l t o cit e th e rapidit y with whic hacut e encephalopath y o r deat hca n develo p i n apparentl y asymptomati c individual s o r in thos e ap parentl y onl y mildl y affecte db y elevate dbod y bur

den s o f lead . I t i s no t unusua l fo r

rapi ddeterioratio n t o occur , wit hconvulsion s o r com asuddenl y appear in g an dprogressin g t o deat hwithi n 4 8 hr . Thi s suggest s tha t

a t hig hbloo dlea dlevels , eve n whe n individual s ar e asymptomatic , rathe r sever e neura l damag e ca n exis t withou t over t manifesta

tions . Studie s sho w tha t apparentl y asymptomati c childre n wit hhig hbloo dlea dlevel s o f ove r 8 0 t o 10 0 /Ag/d l ar e permanentl y impaire dcognitively , a s ar e individual s wh o surviv e acut e episode s o f lea d encephalopathy . Thes e studie s ten dt o suppor t th e hypothesi s tha t

significan t

if albei t subtl e change s i n neura l functio n occu r

a t wha t wer e onc e considere d tolerabl e bloo dlea dlevels . Othe r evidenc e tend s t o confir mrathe r wel l tha t som e typ e o f

neura l damag e doe s exis t i n asympto mati c children , an dno t necessaril y onl y a t

ver y hig h level s o f bloo dlead . Th e bod y o f studie s o n low

- o r moderate-leve l lea deffect s o n neurobehaviora l function s presen t

overal l a n impressiv e arra y o f dat a pointin g t o tha t

conclusion . Severa l well-controlle d studie s fin deffect s tha t ar e clearl y statisticall y sig

nificant , an dman y other s repor t nonsignifican t

bu t borderlin e effects . Sinc e som e o f th e effect s a t

lo w level s o f lea dexposur e discusse din thi s documen t ar e o f asubtl e nature , th e finding s ar e no t alway s strikin g in individua l cases . Nevertheless , whe n th e result s o f

al l o f th e studie s o n neurologi c an dbe

haviora l effect s at

subclinica l exposure s ar e con sidere di n a n overal l perspective , arathe r consisten t patter n o f

impaire dneura l an dcognitiv e function s appear s t o b e associate dwithbloo dlea dlevel s belo w thos e producin g th e over t symptomatolog y o f lea dencephalopathy . Th e bloo dlea dlevel s a t whic h neurobehaviora l deficit s occu r i n otherwis e asymptomati c childre n appea r t o star t a t arang e o f 5 0 t o 6 0 /xg/dl , althoug hsom e evidenc e tentativel y suggest s tha t

suc heffect s may occu r

at slightl y lowe r level s fo r som e children . Dat aobtaine dfor

th e effect s o f

lea do n th e ner vou s syste min laborator y animal s ar e als o quit e ex tensive . Encephalopath y i s produce db y high-leve l perinata l exposur e t o lead ; in differen t species , thi s occur s t o varyin g degree s a s characterize db y th e relativ e exten t

o f neurona l degeneratio n an d vasculopathy . I t

seem s clea r

tha t th e anima l dat a suppor t th e contentio n tha t

th e developin g organis m represent s th e populatio n a t greates t ris k fo r centra l nervou s syste mtoxicity . Ther e i s als o goo devidenc e tha t perinata l ex posur e o f

laborator y animal s t o lea da t moderat e level s will produc e delay s in bot hneurologica l an d sexua l development . Sinc e thes e effect s hav e bee n demonstrate dt o occu r in th e absenc e o f

eithe r undernutritio n o r

growt hretardation , it ha s bee n suggeste dtha t

the y ma y represen t

mor e o r les s direc t effect s o f lea din th e respectiv e systems . I n anima l studies , locomoto r activit y ha s bee n th e mos t commonl y use dbehaviora l inde x o f lea dtox icity . Dat aindicat e tha t increase dlocomoto r

ac tivit y in youn g animal s occur s onl y a t moderatel y hig hexposur e levels . I t

ma y be , in vie w o f

th e levels , tha t th e change s in activit y currentl y reporte din laborator y animal s ar e mor e diagnosti c o f apost encephalopathi c hyperactivit y tha n o f subclinica l effects . Interestingly , th e reactivit y change s see n in olde r animal s ar e associate dwithmuc hlowe r bloo d lea dlevels . Finally , report s o n th e effect s o f lea dexposure s o n 1-7P.3 4

th e acquisitio n and/o r performanc e o f

operan t response s indicat e tha t

perinata l exposur e t o moder

at e o r lo w level s o f

lea dmay disrup t

thi s typ e o f behavior . Thu s a t

bloo dlea dlevel s rangin g fro m3 0 t o 8 0 /xg/dl , cognitiv e functio n appear s t o b e dis

rupte di n animals . Excessiv e lea dexposur e ca n resul t i n acut e a s wel l a s chroni c rena l injur y in man . Th e acut e rena l effect s o f lea dar e see n in person s dyin g o f acut e lea d poisonin g wher e lead-induce danemi aand/o r encephalopath y ma y als o b e seen . Thes e effect s ar e manifeste db y nonspecifi c degenerativ e change s in rena l tubula r

linin g cells , cloud y swelling , an dsom e degre e o f

cellula r necrosis . I n addition , nuclea r in

clusio n bodie s for mi n tubul e cells , an dther e ar e functiona l an dultrastructura l change s in tubula r mitochondria . Aminoaciduria , glycosuria , an d hyperphosphaturi aar e noted , wit haminoaciduri a bein g arathe r

consisten t

featur e o f

tubula r damag e i n children . Thes e effect s ar e usuall y reversible . I t i s no t possibl e a t

th e presen t

tim e t o stat e wha t

leve l o f lea di n bloo di s associate dwithaminoaciduri ao r an y o f th e othe r

specifi c indice s o f

acut e rena l injury . Prolonge dlea dexposur e i n human s ca n resul t in chroni c lea dnephropathy . Th e patholog y o f thes e chroni c change s i s differen t fro mtha t

see n in acut e rena l injury . I t

i s characterize db y th e gradua l onse t o f pronounce darterioscleroti c changes , fibrosis , glomerula r

atrophy , hyalin e degeneration , an d reductio n in kidne y size . Thi s ca n b e aprogressive , irreversibl e conditio n resultin g in deat hfro mrena l failure . A threshol do f lea dexposur e fo r

thes e chroni c change s canno t ye t b e stated , however , a s a resul t o f th e typica l inaccessibilit y o f dat aneede dfo r th e accurat e assessmen t of th e precedin g long-ter m exposur e history . Considerabl e evidenc e fo r th e advers e effect s o f lea do n reproductio n an ddevelopmen t in ma n ha s bee n accumulatin g fo r man y years . Man y o f th e earl y dat ao n th e inductio n o f abortions , stillbirths , an dneonata l death s wer e fo r occupationall y ex pose dpregnan t

women , wher e suc heffect s wer e demonstrate dat

hig hbloo dlea dlevels . O f mor e pressin g presen t

interes t ar e certai n recen t

studie s i n thi s are afocusin g o n tw o aspect s o f th e effect s o f

lo w t o moderat e lea dexposur e o n reproduction : gameto toxicit y an dpost-conceptio n events . I n regar dt o potentia l lea deffect s o n huma n ovaria n function , on e stud y ha s show n tha t short

ter mexposur e a t

ambien t ai r level s o f

les s tha n 7 /ig/m 3 ma y caus e an increas e in th e anovula r cycl e an ddisturbance s i n th e lutei n phase . Thi s study , however , require s confirmatio n befor e conclusiv e statement s ca n b e made . Anothe r recen t repor t in

volvin g occupationa l exposur e similarl y suggest s tha t moderatel y increase dlea dabsorptio n (bloo d lea dmea n = 52. 8 /ig/dl ) ma y resul t in direc t testicula r impairment ; however , th e desig n o f thi s stud y i s suc htha t

thi s observatio n als o require s verification . Thus , i t i s clea r tha t gametotoxic , embryotoxic , an dteratogeni c effect s at agros s leve l ca n b e in

duce din laborator y animal s withlead , bu t it shoul d b e emphasize dtha t

th e productio n o f

suc heffect s probabl y require s acute , hig hexposures . Unfor

tunately , apaucit y o f informatio n exist s o n th e teratogenicit y an ddevelopmenta l toxicit y o f chroni c lo w o r moderat e lea dexposures . Availabl e dat ao n th e subjec t

d o suggest , however , tha t chroni c low

leve l lea dexposur e may induc e postnata l develop

menta l delay s in rats . Ou r presen t knowledg e abou t

th e effect s o f

lea din ma n o n th e hepatic , cardiovascular , immunologic , an dendocrin e system s i s fragmentary , renderin g it difficul t t o mak e an y conclusiv e statement s abou t quantitativ e relationships . Fo r example , effect s o f lea do n th e endocrin e syste mar e no t wel l define da t present . Thyroi dfunctio n in man , however , ha s bee n show n t o b e decrease din occupationa l plumbism . Also , effect s o f

lea do n pituitar y an dadrena l func

tio n i n ma n hav e bee n observed , wit hdecrease d secretio n o f

pituitar y gonadotrophi c hormone s bein g note dbu t

adrena l functio n effect s bein g ales s con sisten t finding . Th e respons e o f

th e hepati c syste mt o lea dha s no t bee n wel l characterize din man ; instead , muc ho f th e literatur e deal s withhepati c effect s in experimenta l animals . Lead-poisone danimal s sho w significantl y impaire ddrug-metabolizin g activities , thu s suggest in g a n effec t

o n th e hepati c mixed-functio n oxidas e system . Sinc e detoxificatio n i n animal s depend s o n th e microsoma l hem e protein , cytochrom e P450 , an dsinc e hem e biosynthesi s i s impaire din lea dex posure , suc ha n effec t

i s alogica l consequenc e o f lea dpoisoning . O f mor e direc t

interes t in term s o f

reproductiv e efficienc y ar e th e effect s o f lea dexposur e o n preg nan t wome n —no t

onl y o n feta l healt han ddevelop

ment , bu t als o o n materna l complications . Placenta l transfe r o f lea dha s bee n demonstrate dbot hb y feta l tissu e analysi s an dcompariso n o f newbor n umbilica l cor dbloo dlea dwithmaterna l bloo dlead . On e mus t no t onl y conside r

th e resultin g absorptio n o f lea db y th e fetus , bu t

als o th e specifi c point s in embryoni c developmen t

a t whic hexposur e occurs . Feta l tissu e uptak e o f

lea doccur s b y th e en do f th e firs t tri

1

-mester , whic hma y b e asensitiv e perio di n

embryoni c developmen t o f th e nervou s system . Studie s comparin g umbilica l cor dbloo dlea d level s in newborn s withsimultaneousl y sample d materna l bloo dsho w tha t th e newbor n an dmaterna l level s ar e closel y correlated . Th e studie s hav e als o show n tha t

th e newborn s o f

mother s in a n urba n set tin g ar e bor n wit hgenerall y highe r bloo dlevel s tha n thos e o f correspondin g newborn s fro mrura l areas . Tha t th e prenata l exposur e o f th e fetu s t o lead , eve n in th e absenc e o f

teratogeni c effects , i s o f conse quenc e fo r

advers e healt heffect s i s show n b y studie s relatin g feta l level s t o change s in feta l hem e syn thesi s an dt o th e incidenc e o f prematur e births . Som e suggestion s in th e literatur e tha t hem e biosynthesi s in anewbor n ma y b e affecte drequir e confirmation . I n evaluatin g materna l complication s relate dt o lea dexposure , on e mus t conside r tha t pregnanc y i s a physiologica l stres s tha t may plac e th e pregnan t woma n a t

highe r ris k t o lea dexposur e effects . Bot h iro n an dcalciu mdeficienc y increas e th e suscep tibilit y o f

an individua l t o lea dtoxicity . Wome n hav e a n increase dris k o f bot hdeficiencie s durin g pregnanc y an dpostpartum . Som e availabl e bu t

unconfirme dinformatio n in

dicate s tha t

th e ris k o f prematur e ruptur e o f

th e am nioti c membran e ma y b e highe r in case s o f

elevate d exposur e tha n in age-matche dcontrol s withou t suc h exposure . Th e literatur e leave s littl e doub t abou t th e deleteriou s healt heffect s o f lea do n reproduction , bu t mos t report s d o no t

provid e specifi c description s o f exposur e level s at

whic hspecifi c reproductiv e effect s ar e noted . Materna l bloo dlea dlevel s o f approximatel y 3 0 /xg/d l ma y b e associate dwit ha highe r incidenc e of

prematur e deliver y an dpre matur e membran e rupture , bu t thes e observation s requir e confirmation . I n adul t males , level s o f

5 0 t o 8 0 /xg/d l ma y b e sufficien t t o induc e significan t spermatotoxi c effects , bu t thi s effec t

ha s no t bee n conclusivel y demonstrated . Lea dha s no t

bee n show n t o b e teratogeni c in man , bu t anima l experiment s hav e demonstrate dtha t hig h level s o f lea dtha t

ar e stil l compatibl e wit hlif e in sexuall y matur e animal s interfer e wit hnorma l reproduction ; thes e studie s includ e assessmen t o f lea deffect s in bot hparents . Reductio n in offsprin g number , weight , an dsurviva l an da n increas e in feta l resorptio n i s aconsisten t findin g in rats , mice , an d othe r specie s ove r

arang e o f

high-leve l lea dex posures . Effect s o n offsprin g hav e bee n show n t o in

volv e th e gametotoxi c effec t o f lea do n male s a s wel l a s female s i n anumbe r o f anima l species . A t lea dlevel s presentl y encountere din occupa tiona l exposure , n o significan t cardiovascula r

effect s ar e discernible . Clinica l dat afor childre n sufferin g fro mchroni c lea dpoisonin g resultin g in deat hindi

cat e tha t extensiv e myocardia l damag e occurs . I t i s no t clea r tha t th e associate dmorphologica l change s ar e aspecifi c respons e t o lea dintoxication . How

ever , in man y instance s wher e encephalopath y i s present , th e electrocardiographi c abnormalitie s dis

appea r withchelatio n therapy . Ther e ar e insufficien t

dat apertainin g t o th e effect s o f elevate dbloo dlea dlevel s an dth e incidenc e o f in

fectiou s disease s in ma n t o allo w th e derivatio n o f a dose-respons e relationship . Neithe r ca n adose

respons e relationshi p b e define dfo r th e effect s o f elevate dbloo dlea dlevel s o n th e gastrointestina l tract , eve n thoug hcoli c i s usall y aconsisten t earl y sympto mo f

lea dpoisonin g in adult s expose d occupationall y an din infant s an dyoun g children . 1.2. 2 Effect s o f

Lea d o n th e Ecosyste m A s anatura l constituent , lea ddoe s no t usuall y pos e athrea t

t o ecosystems . Th e redistributio n o f naturall y occurrin g lea di n th e environment , how

ever , ha s no w cause dsom e concer n tha t lea dma y represen t apotentia l threa t

t o th e ecosystem . Fo r

ex ample , studie s hav e show n afivefol dincreas e in lea d in tre e ring s durin g th e las t 5 0 years ; thi s accumula

tio n may serv e a s ausefu l inde x o f pattern s o f

en vironmenta l lea daccumulation . Ther e ar e als o documente deffect s o f lea do n domesti c animals , wildlife , an daquati c life . Lea d poisonin g in domesti c animal s produce s varyin g degree s o f

derangemen t

o f th e centra l nervou s system , gastrointestina l tract , muscula r system , an d hematopoieti c system . A s i s tru e in man , younge r animal s appea r

t o b e mor e sensitiv e tha n olde r ones . Wildlif e ar e expose dt o awid e rang e o f lea d levels . Toxi c effect s fro mingestio n o f lea dsho t

hav e lon g bee n recognize da s amajo r healt hproble min waterfowl . Severa l specie s o f smal l mammal s trap pe dalon g roadway s wer e teste dfo r lea dconcentra tions . Al l bu t

on e o f th e specie s livin g i n habitat s ad

jacen t t o high-volum e traffi c showe dhig hcon centration s o f

lead . Thi s wa s especiall y tru e i n urba n areas . Lea dtoxicit y in aquati c organism s ha s bee n ob

serve dan dstudie dexperimentally . Symptom s o f chroni c lea dpoisonin g i n fis hinclud e anemia , possi

bl e damag e t o th e respirator y system , growt hinhibi

tion , an dretardatio n o f sexua l maturity . Ther e i s evidenc e tha t

lea dha s bot hharmfu l an d beneficia l effect s o n plants . Plant s ar e expose dt o lea dthroug hth e leaves , stems , bark , o r roots , an d 1-9P.3 6

th e exten t

o f th e effect s depend s o n th e form , amount , an davailabilit y o f tha t lead . Th e morpholog y o f

th e plan t

surfac e play s th e majo r rol e in determinin g th e typ e an dquantit y o f materia l re taine db y plants . Meteorologica l factor s ar e als o im

portan t i n determinin g th e fat e o f lea dtha t

come s int o contac t

wit hplants . Larg e deposit s o f iner t in

solubl e meta l compound s o n th e leave s ar e probabl y o f littl e consequenc e t o plants , a s th e mos t importan t facto r i s th e solubilit y o f

th e metal . Thus , becaus e in

organi c lea dcompound s ar e generall y o f lo w solubility , ther e i s littl e incorporatio n an daccumu latio n withi n th e leave s o f plants . Th e majorit y o f

studie s reportin g lea dtoxicit y in plant s hav e bee n conducte dwithplant s grow n in artificia l nutrien t

culture . Thes e studie s hav e pro mote dth e concep t

tha t th e effect s o f

lea dar e depen

den t o n avariet y o f

environmenta l factors , includin g anion s an dcation s withi n th e plan t an din th e growt h media , an dth e physica l an dchemica l characteristic s o f th e soi l itself . A s lea dinteract s wit hman y environmenta l factors , specifi c correlation s betwee n lea deffect s an dlea dconcentration s ar e extemel y difficul t t o predict . 1. 3 EFFECT S O F LEA D O N POPULATION S Th e frequenc y distributio n o f bloo dlea dlevel s in homogeneou s huma n population s ha s almos t invari

abl y bee n foun dt o b e lognormal . Mos t dat aset s o f homogeneou s population s displa y ageometri c stan dar ddeviatio n (GSD ) o f 1. 3 t o 1.5 . Thi s woul d roughl y correspond , fo r example , t o a n arithmeti c standar ddeviatio n o f

5. 3 t o 8. 5 /xg/d l a t

amea n bloo dlea do f

2 0 /xg/dl . Fro mth e lognorma l distribution , give n amea n bloo dlea dleve l an destimate dGSD , it i s possibl e t o predic t th e percentag e o f

apopulatio n whos e bloo d lea dlevel s excee do r

fal l belo w aspecifie dvalue . I t i s als o possibl e t o estimat e th e probabl e increas e i n mea n bloo dlea dlevel s fo r apopulatio n expose dt o a specifi c increase s i n environmenta l lead . Thes e tw o procedures , use dtogether , provid e ametho db y whic hai r qualit y standard s ma y b e chose n t o protec t th e healt ho f

th e population . Bloo dlea dlevel s var y wit hgeographi c location . The y ar e lowes t

i n som e remot e populations , highe r i n mos t rura l settings , highe r

stil l i n suburba n areas , an dhighes t

i n inner-cit y areas . Thi s gradien t follow s th e presume dlea dexposur e gradient . Bloo dlea d value s als o var y b y age , sex , an drace , althoug hi n a somewha t

mor e comple x fashion . Generally , youn g childre n hav e th e highes t levels , wit hlittl e differenc e note dbetwee n sexe s a t thi s age . I n olde r segment s o f th e population , afte r

eliminatio n o f

oc cupationa l exposur e i n lea dworkers , male s stil l hav e ahighe r

bloo dlea dtha n females . Onl y limite d publishe ddat aar e availabl e comparin g th e bloo d level s o f th e variou s racia l an dethni c group s o f th e population . Thes e dat asugges t tha t urba n black s hav e highe r

lea dlevel s tha n whites , wit hlevel s in Puert o Rican s frequentl y bein g intermediate . Result s o f

th e numerou s studie s o f environmenta l lea dexposure s o f

ma n hav e indicate dstrongl y tha t ma n doe s indee dhav e cumulativ e uptak e fro meac h sourc e t o whic hh e i s exposed . Equall y important , thes e studie s hav e show n tha t th e bloo dlea dleve l represent s asummatio n of th e absorptio n fro meac h o f thes e sources . Dat afo r th e tw o mos t

widesprea denvironmenta l source s o f

lea dothe r

tha n foo dpermi t

summar y statement s concernin g thei r quantitativ e relation

shi p withbloo dlea dlevels : ai r an dsoil/dust . Bloo d lea dlevel s wer e foun dt o increas e withrisin g ai r lea dconcentrations . Th e relationship s wer e foun dt o b e eithe r log-linea r

o r log-log . Evaluatio n o f th e equation s a t

variou s commonl y observe dai r lea d level s reveale dtha t

th e rati o betwee n change s i n bloo dan dchange s in ai r lea dvarie dgenerall y be

twee n 1 an d2 an dtha t it wa s no t constan t ove r th e rang e o f ai r exposures . Thi s implie s tha t a n increas e o f 1 /xg/m 3 o f

ai r lea dresult s in a n averag e increas e o f 1 t o 2 /xg/d l in bloo dlea dlevels . Suggestiv e evi

denc e indicate s tha t

childre n ma y hav e highe r ratio s tha n adult s an dtha t

male s ma y hav e highe r ratio s tha n females . On e o f th e mos t extensiv e dat aset s o n bloo dlea d in childre n come s fro mastud y b y th e U.S . Depart

men t o f Housin g an dUrba n Developmen t o n th e bloo dlea dvalue s o f approximatel y 180,00 0 childre n i n Ne w Yor k

City . Thes e dat acovere dth e perio dMarc h197 0 throug hDecembe r 1976 . A pre liminar y analysi s o f

thes e importan t

researc hfind

ings wa s presente dt o th e Subcommitte e o n Lea do f EPA' s Scienc e Advisor y Boar din Octobe r 1977 . Th e followin g pattern s appea r t o b e indicate db y thes e data : 1 . Ther e i s adefinit e differenc e in bloo dlea d value s fo r

racia l an dethni c groups , black s havin g highe r

mea n lea dlevels , an dHis

panic s an dwhite s havin g lowe r levels . 2 . Analysi s show s tha t th e mea n bloo dlea d leve l i s relate dt o rac e an dethnicity , age , an dyea r o f sampling . Thi s ag e dependenc e i s simila r fo r al l years : Th e 1 - t o 12-month-ol d grou p ha s th e lowes t

levels , an dgenerall y th e maximu mi s foun din 2

- t o 4-year-olds . 1-1 03 . Ther e wa s aconsisten t decreas e o f

mea n bloo dlea dlevel s ove r th e cours e o f

th e study . Thi s decreas e wa s coinciden t wit ha reductio n in lea dlevel s in gasolin e in th e Ne w Yor k

Cit y area . 4 . Ther e appear s t o b e alikel y correspondin g decreas e in th e ai r

lead . However , it

shoul d b e pointe dou t

tha t ai r lea ddat afo r

Ne w Yor k Cit y ar e spars e an dtha t it woul db e un wis e t o assum e tha t

th e ai r lea dleve l a s measure dat

asingl e locatio n woul db e th e sam e fo r al l locations . Becaus e o f th e heigh t o f th e sampler , i

t i s als o questionabl e whethe r th e ai r lea dleve l woul drepresen t th e leve l t o whic hth e populatio n i s exposed . Consisten t

relationship s betwee n bloo dlea dlevel s an dexposur e t o lead-containin g soi l hav e bee n shown . Also , childre n expose dt o highe r con centration s o f

soi l an dhous e dus t

lea dhav e bee n show n t o hav e elevate dconcentration s o f lea do n thei r hands . Th e intermediat e link , fro melevate d han dlevel s o f

lea dt o elevate dbloo dlevels , ha s no t ye t bee n established . Quantitatively , bloo dlea d level s hav e bee n show n t o increas e 3 t o 6 percen t give n adoublin g o f

th e soi l o r

dus t lea dcontent . Significan t

wate r lea dexposure s in thi s countr y hav e onl y occurre di

n place s havin g asof

t wate r sup pl y an dusin g leade dpipes . Suc hexposure s hav e bee n show n t o b e associate dwithsignifican t eleva

tion s o f bloo dlead . The y hav e als o bee n linke dt o case s o f menta l retardation . Exposur e t o leade dpain t stil l constitute s aver y seriou s proble mfo r

America n childre n in urba n set tings . Althoug hne w regulation s o f th e lea dconten t o f pain t shoul dalleviat e th e proble min ne w hous

ing , th e poorl y enforce dregulatio n an dlac k o f regulatio n o f

th e pas t hav e lef

t aheav y burde n o f lea dexposures . Mos t

o f th e studie s o n lea dpoison

in g i n childre n hav e assume dan associatio n with leade dpaint . I t

i s ver y difficul t

in thes e studie s t o measur e th e actua l amoun t o f exposure . Ther e i s nevertheles s incontrovertibl e evidenc e tha t th e con tributio n fro mthi s sourc e i s ver y significan t fo r cer tai n segment s o f

th e population . Foo dlea dexposure s ar e though t t o b e asourc e o f asignifican t

portio n o f

bloo dlead . Precis e quantita

tiv e estimate s o f

th e relationshi p betwee n foo dan d bloo dlea dar e no t

available , however . Similarly , precis e quantitativ e estimate s ar e no t availabl e for th e relativ e contribution s o f differen t source s t o th e tota l amoun t

o f lea di n th e diet . I t

i s clear , however , tha t probabl y th e larges t

proportio n o f

dietar y lea d i s derive dfro mfoo dprocessin g (e.g. , fro msolde r in th e seam s o f

cans) , an dsom e i s als o derive dfro m lea din th e ai r

an dth e soil . 1.4 ASSESSMEN T O F RIS KFRO M HUMA N EXPOSUR E T O LEA D O f th e estimate d160,00 0 metri c ton s o f lea demit

te dint o th e atmospher e in 1975 , th e combustio n o f gasolin e additive s an dwast e oi l accounte dfo r 9 5 percen t o f th e total . Onc e lea di s introduce dint o th e air , it i s subjec t

t o avariet y o f

processes , includin g dr y deposition , precipitation , an dresuspension . Othe r use s of lea dresul t

in othe r avenue s o f

ex posure : (1 ) Lea din pain t make s lea davailabl e b y in

gestion ; (2 ) lea din plumbin g fo r potabl e wate r wher e th e wate r

i s sof t (lo w pH ) permit s leachin g an dmake s lea davailabl e b y ingestion ; (3 ) lea din th e diet , introduce db y processing , packaging , an d ra w foo dstock , als o make s lea davailabl e b y in

gestion . I t

i s therefor e importan t t o realiz e tha t huma n exposur e t o lea di s th e summatio n o f al l thes e comple x an dindividua l sources . Th e factor s tha t

gover n th e quantitativ e aspect s o f inhalatio n an dingestio n o f lea dhav e bee n pointe d out , an dattentio n ha s bee n give n t o th e fac t tha t in

gestio n include s bot hfoo dan dnonfoo dmaterials . In th e cas e o f

children , th e nonfoo dmateria l ha s especiall y importan t

implications . Thu s th e tota l in

terna l dos e i s afunctio n o f al l externa l source s with whic hth e bod y come s int o contact . Th e relativ e sig

nificanc e o f

an y give n exposur e sourc e depend s o n th e specifi c exposur e circumstance s an dcertai n at tribute s o f

th e populatio n a t

risk . 1.4. 1 Us e o f

Bloo d Lea d Level s i n Ris kAssess men t Th e evidenc e fo r

increase dbloo dlea dlevels , th e usua l accepte dindicato r o f lea dexposure , ha s evolve dfro mstudie s o f bot hsingle-sourc e an d multiple-sourc e exposures . Studie s o f singl e source s o f ai r lea dhav e include dbot hepidemiologica l an d clinica l investigations . Clinica l dat auniforml y demonstrat e an dquantif y th e actua l transfe r

o f lea d in ai r t o blood . Th e epidemiologica l dat aar e no t a s definitive , bu t

the y ar e mor e relevan t t o th e rea l worl dan dclearl y suppor t suc harelationship . Studie s concerne dwit hdus t an dsoi l lea dex posure s ma y b e considere djointly , sinc e mos t studie s hav e no t

attempte dt o isolat e thei r relativ e contributions . Stron g evidenc e exist s t o sho w tha t thes e source s ca n b e significan t determinant s o f bloo dlea dlevels . Furthermore , investigation s in

volvin g childre n expose dt o lead-contaminate ddus t hav e demonstrate dlea do n th e children' s hands . 1-1 1P.3 8

providin g stron g inferentia l evidenc e fo r a n ora l rout e o f entry . Lead-base dpain t

i s associate dwithover t clinica l intoxicatio n an dwidesprea dexces s absorptio n in children . Screenin g program s in al l majo r urba n area s hav e sough t

t o abat e thi s sever e publi c healt h problem , bu t

onl y withlimite dsuccess . Thes e childre n represen t

aparticularl y hig hris k grou p withrespec t

t o th e incrementa l lea dexposur e attri

butabl e t o direc t

inhalatio n o f

atmospheri c lea da s wel l a s wit hrespec t

t o th e ingestio n o f

dus t con taminate db y lea dfro mth e atmosphere . Studie s centere daroun dprimar y lea dsmelter s an dsecondar y industria l source s in urba n setting s hav e consistentl y an dindependentl y demonstrate da relationshi p betwee n bloo dlea dlevel s an dthes e mixe dsources . Mos t

characteristic s tha t

mediat e th e relationshi p betwee n bloo dlea dleve l an dlea dex posur e hav e bee n examine din severa l studies . Ag e i s certainl y asignifican t

facto r in determinin g bloo d lea dlevels , particularl y in childre n unde r 6 year s o f age . Wit hregar dt o se x differences , ther e appea r t o b e non e amon g children , wherea s i n adults , male s generall y exhibi t

highe r level s tha n females . Thoug h on e stud y ha s reporte dtha t blac k childre n hav e highe r lea dlevel s tha n whit e children , th e overal l dat aar e to o spars e t o establis haconclusiv e relation

ship . Socioeconomi c variable s suc ha s incom e an d education , a s wel l a s genera l healt hstatus , hav e no t bee n examine din thes e studies . A numbe r

o f summar y statement s may b e mad e abou t th e quantitativ e relationship s pertainin g t o bloo dlead . Th e weigh t o f evidenc e indicate s tha t bloo dlea dlevel s follo w alog-norma l distributio n withageometri c standar ddeviatio n o f abou t 1. 3 t o 1.5 . Th e log-norma l distributio n possesse s prop ertie s tha t

mak e it o f valu e i n arrivin g at

acceptabl e maxima l exposures , sinc e i t make s it possibl e t o esti

mat e aproportio n o f

apopulatio n whos e bloo dlea d level s excee dan y specifie dlevel . Th e increas e i n bloo dlea dleve l resultin g fro man increas e i n ai r

lea dconcentratio n i s no t constan t in magnitud e ove r

th e rang e o f

ai r lea dlevel s com monl y foun di n th e environment . Th e relationshi p i s dependen t

o n man y factors , includin g rat e o f curren t exposur e an dth e histor y o f pas t exposure . Th e ob

serve dratio s var y fro mai r lea dleve l t o ai r

lea d level ; the y ar e generall y betwee n 1 an d2 . Evidenc e suggest s tha t

th e ratio s fo r

childre n may b e highe r tha n thos e o f

adults ; als o it

suggest s tha t

ratio s fo r male s ma y b e highe r

tha n thos e fo r

females . Ther e i s genera l agreemen t tha t bloo dlea dlevel s begi n t o increas e whe n soi l level s ar e 50 0 t o 100 0 ppm . Mea n percen t increase s i n bloo dlea dlevels , give n atwofol dincreas e in soi l lea dlevels , range d fro m3 t o 6 ; thi s i s remarkabl y consisten t give n th e divergenc e o f

th e population s studied . On e o f th e mos t

importan t

aspect s o f

ris k assess men t i s th e evaluatio n o f

effect s o f

long-term , low

level , o r intermitten t

exposures . I n suc hcircum

stances , bloo dlea dlevel s d o no t alway s correlat e wel l withth e exposur e history . I n on e clinica l stud y o f lea dexposur e b y inhalation , a n averag e ai r leve l o f 3. 2 /xg/m 3 ove r

aperio do f

abou t 7 week s wa s re late dt o asignifican t

ris e in bloo dlea dafte r abou t 7 weeks . Whe n expose dt o clea n air , th e bloo dlea d level s o f thes e sam e subject s returne dt o pre-ex posur e levels . 1.4. 2 Us e o f

Biologica l an d Advers e Healt h Effect s o f

Lea d i n Ris kAssessmen t Lea di s no t

conclusivel y know n t o hav e an y biologica l effec t

o n ma n tha t

ca n b e considere d beneficial . Therefore , an y o f th e biologica l an dad

vers e healt heffect s o n ma n at thi s tim e mus t

b e con sidere dfro mamedica l poin t o f vie w tha t acknowledge s th e absenc e o f an y healt h benefit/healt hcos t

ratio . Earlie r discussio n considere dth e biologica l an d advers e healt heffect s o f lea dacros s th e entir e rang e o f lea dexposures . I n ris k assessment , th e primar y focu s i s o n thos e biologica l an dadvers e physiologi

ca l effect s tha t

relat e t o th e genera l population . Thoug hth e literatur e dealin g withth e healt h effect s o f lea dembrace s virtuall y al l o f th e majo r orga n system s in man , hematologica l an dneurologi

ca l effect s ar e o f

prim e concern . Thes e effect s ar e summarize din Tabl e 1-1 . I t shoul db e pointe dou t tha t Tabl e 1- 1 i s alowest-observed-effect s leve l tabulation ; i.e. , it

list s th e lowes t

bloo dlea dlevel s at whic hparticula r

effect s hav e bee n credibl y reporte d fo r give n subpopulations . Fou r hematologica l effect s ar e considered : anemia , inhibitio n o f th e enzym e 8-ALAD , urinar y 8-AL A excretion , an delevatio n o f fre e erythrocyt e porphyri n (FEP) . Anemi ai s foun din childre n wit han dwithou t con comitan t iro n deficiency . Increase dlea dintak e prompt s amor e sever e anemia . Thi s i s o f specia l im

portanc e in childre n 1 t o 6 year s ol do f lowe r socio

economi c status , sinc e thi s grou p als o ha s ahig hinci

denc e o f iro n deficiency . Th e literatur e relatin g bloo dlea dlevel s t o a statisticall y significan t

reductio n in hemoglobi n point s t o athreshol dleve l o f 4 0 /xg/d l fo r

childre n an dacorrespondin g valu e o f 5 0 /Ag/d

l fo r adults . Th e questio n o f

alow-threshol do r

no-threshol d 1-1 2TABL E 1-1 . BLOO D LEA D LEVEL S VERSU S LOWEST OBSERVED-EFFECT S LEVEL S Lowes t level lo robserve d effects , tig Pb/d l whol e bloo d 1 0 1 5 t o 2 0 2 0 t o 2 5 4 0 4 0 4 0 5 0 5 0 t o 6 0 5 0 t o 6 0 8 0 t o 10 0 10 0 t o 12 0 Observe d effec t ALA D inhibitio n Fre e erythrocyt e porphyri n elevatio n Fre e erythrocyt e porphyri n elevatio n Increase d urinar y AL Aexcretio n Anemi a Coproporphyri n elevatio n Anemi a Cognitiv e (CNS ) deficit s Periphera l neuropathie s Encephalopath y symptom s Encephalopath y symptom s Populatio n grou p Childre n an d adult s Adul t female s an d childre n Adul t male s Childre n an d adult s Childre n Adult s an d childre n Adult s Childre n Adult s an d childre n Childre n Adult s leve l fo r th e inhibitor y effec t

o f lea do n th e enzym e 8-ALA D i s overshadowe db y th e large r issu e o f th e healt hsignificanc e o f

thi s observation . I n an y event , avalu e o f

1 0 /xg/d l bloo dlea dappear s t o represen t a threshol dlevel . Elevatio n o f urinar y 8-AL A levels , however , appear s t o b e considere da n inde x o f physiologica l impairment , an dth e threshol dleve l o f thi s effec t

i s approximatel y tha t fo r anemi ai

n childre n (i.e. , 4 0 /xg/dl) . Thi s valu e seem s t o appl y fo r bot hchildre n an dadults . Elevatio n o f

erythrocyt e porphyri n i s bette r ac cepte das.a n indicato r

o f physiologica l impairment . O n th e basi s o f

anumbe r

o f studies , threshol dvalue s o f bloo dlea da t

whic herythrocyt e protoporphyri n i s elevate dappea r

t o b e 1 5 t o 2 0 /xg/d l fo r childre n an dadul t

female s an d2 0 t o 2 5 /xg/d l fo r adul t males . Th e hematologica l effect s describe dabov e ar e th e earlies t physiologica l impairment s encountere da s a functio n o f

increasin g lea dexposure s a s indexe db y bloo dlea delevations ; a s such , thos e effect s ma y b e considere dt o represen t critica l effect s o f

lea dex posure . Althoug hi t

ma y b e argue dtha t

certai n o f

th e initia l hematologica l effect s (suc ha s ALA D inhibi

tion ) constitut e relativel y mild , nondebilitatin g symptom s a t

lo w bloo dlea dlevels , the y nevertheles s signa l th e onse t

o f steadil y intensifyin g advers e effect s a s bloo dlea delevation s increase . Eventually , th e hematologica l effect s reac hsuc hmagnitud e tha t the y ar e o f

clear-cu t

medica l significanc e a s indica

tor s o f undu e lea dexposure . O f eve n greate r

concer n tha n earl y symptom s o f lea dexposure s (i.e. , hematologica l impairments ) ar e th e neurologi c effect s o f lea dtha t

begi n t o b e en countere da s th e hematologica l deficit s reac hclini

ca l magnitudes . Childre n ar e mos t clearl y th e populatio n a t

ris k fo r neurologi c effects . Th e neurologi c effects , includin g bot hperiphera l neuro pathie s an dsign s o f

CN S damage , ar e firs t encoun tere dfo r som e childre n a s bloo dlea dlevel s reac h5 0 t o 6 0 /xg/dl ; an dthe y ver y rapidl y intensif y i n severit y a s afunctio n o f increasin g bloo dlea deleva

tions . O f grea t medica l concer n i s th e ver y stee p up war dris e i n th e ris k fo r permanent , sever e neurologica l damag e o r deat ha s bloo dlea deleva

tion s approac han dexcee d8 0 t o 10 0 /xg/d l in children . Inne r

cit y childre n ar e o f

particula r

con cer n withrespec t

t o th e manifestatio n o f lead-in

duce dneurologi c deficits , a s documente db y th e evi

denc e discusse din Sectio n 11.5 . Som e evidenc e ha s recentl y bee n advance dtha t suggest s tha t

long-ter mneurobehaviora l deficit s may als o b e induce db y in utero exposure s o f huma n fetuses t o lead , a s indicate db y th e apparen t highe r incidenc e o f

postnata l menta l retardatio n amon g childre n bor n o f

mother s experiencin g elevate dlea d exposur e befor e o r

durin g pregnancy . Thu s wome n o f childbearin g ag e ma y b e anothe r grou p a t

specia l ris k b y virtu e o f

th e potentia l in utero exposure s o f fetuses . However , th e paucit y o f informatio n o n ex ac t exposure s experience db y thes e mother s an dth e lac k o f othe r confirmator y studie s d o no t allo w firm statement s t o b e mad e abou t probabl e threshol d lea dexposur e level s fo r pregnan t

wome n tha t

ma y induc e late r

neurobehaviora l deficit s i n thei r children . I t i s eve n mor e difficul t

t o spea k

o f risk-to-healt h assessmen t

i n term s o f

threshol dlevel s fo r

effect s o f lea do n reproduction , sinc e th e relevan t dat aar e sparse . However , in n o othe r aspec t o f healt heffect s i s th e potentia l fo r

deleteriou s healt heffect s o f lea d a s inherentl y grea t

a s in th e are ao f

reproductio n an d development . I n particular , lea dcrosse s th e placen

ta l barrier , placin g th e huma n fetu s a t direc t risk . An dsuc hexposur e begin s at astag e o f

gestatio n whe n neura l embryoni c developmen t i s beginning . Placenta l transfer , couple dwithth e fac t tha t a n effectiv e blood-brai n barrie r i s no t presen t in huma n fetus , mean s tha t

ther e i s effectivel y adirec t pat h fro mmaterna l lea dexposur e t o th e feta l nervou s system . Availabl e informatio n suggest s tha t ther e ar e severa l possibl e consequence s t o th e newbor n arisin g fro mlea dexposure . Prematur e birt hi s suggeste da s 1-1 3P.4 0

bein g associate dwithelevate dbloo dlea dlevel s in women , an dsom e impairmen t in th e hem e biosyn

theti c pathwa y ma y exis t in th e newbor n childre n o f mother s havin g elevate dbloo dlea dlevels . Muc ho f th e discussio n abov e ha s deal t wit h relationship s betwee n bloo dlea dlevel s an dvariou s biologica l effect s o f

lead . Thi s discussio n wa s pri

maril y concerne dwit hthreshol dlevel s a t whic h healt heffect s o f

lea dar e firs t

observe din differen t populatio n groups . O f

additiona l interes t

i s th e pro portio n o f

apopulatio n exhibitin g ahealt heffec t at a give n bloo dlea dleve l (i.e. , th e dose-respons e curve) . Thre e differen t

assessment s o f

dose-respons e relationship s fo r

hematologica l effect s hav e bee n carrie dou t

an dpublished . Thes e effect s ar e th e in

hibitio n o f

ALAD , elevatio n o f

ALA-U , an deleva

tio n o f E Plevel s i n th e blood . A s note delsewher e i n thi s summary , som e questio n exist s concernin g th e relevanc e o f

ALA D inhibitio n t o huma n health . Th e othe r tw o hematologica l effect s ar e relevant . Tabl e 1-2 show s ALA- U dat afro mtw o studies , on e pub

lishe dan don e don e b y EP A (se e Chapte r 13) . TABL E 1-2 . ESTIMATE D PERCENTAG E O F SUBJECT S WIT H ALA- U EXCEEDIN G 5 mg/lrt« r FO R VARIOU S BLOO D LEA D LEVEL S Bloo d lea d level , pg/d l 1 0 2 0 3 0 4 0 5 0 6 0 70 Zielhui s estimate . % 0 0 6 2 4 4 8 7 6 9 6 Aza r e t al . estimate . % 2 6 1 6 3 1 5 0 6 9 8 4 Publishe dstudie s (se e Chapte r 13 ) o f dose-respons e relationship s als o exis t fo r erythrocyt e proto porphyri n an dar e presente di n Tabl e 1-3 . TABL E 1-3 . ESTIMATE D PERCENTAG E O F CHILDRE N WIT H E P EXCEEDIN G SPECIFIE D CUTOF F POINT S FO R VARIOU S

BLOO D LEA D LEVEL S Bloo d lea d level . /ig/d l 1 0 2 0 3 0 4 0 5 0 6 0 70 8 0 Zielhui s

estimate. 8 % 0 6 2 2 37 49 ~

-

- Roel s et al .

estimate, 1 5 % 3 2 7 7 3 100

- —

-

- Piomell i

estimate, 0 % 9 1 1 4 8 8 0

-

-

-

- E P >E P o

f childre n wit h bloo d lea d level s <2 0 pg/dl . b E P >82(ifl/<l l cells . C E P >33MS/<1I 1.4. 3 Population s a tRis k Th e concep t

o f "specia l risk " i s define da s a populatio n segmen t

exhibitin g characteristic s asso ciate dsignificantl y highe r probabilit y o f

developin g acondition , illness , o r othe r abnorma l statu s a s a resul t o f exposur e t o agive n toxi c agent . Wit h respec t t o lead , tw o suc hsegment s o f huma n popula

tion s ar e currentl y definable : preschoo l childre n an d unbor n fetuses , wit hpregnan t wome n a s th e recip

ien t populatio n o f

concern . 1.4.3. 1 PRESCHOO LCHILDRE N Ther e i s a n impressiv e bod y o f dat atha t

indicate s tha t childre n ar e inherentl y mor e susceptibl e t o lea d b y virtu e o f

physiolog y an dtha t

the y hav e adifferen t relationshi p t o exposur e sources . Thes e physiologi

ca l factor s include : (1 ) greate r lea dintak e o n aper unit-body-weigh t

basis ; (2 ) greate r

net respirator y intak e a s wel l a s greate r net absorptio n an dretentio n o f lea denterin g th e gastrointestina l tract ; (3 ) rapi d growth , whic hreduce s th e margi n o f safety agains t

a variet y o f

stresses , includin g nutritiona l deficiency ; (4 ) certai n incompletel y develope ddefens e mechan

ism s i n ver y youn g children , suc ha s th e blood-brai n barrie r i n newborns ; an d(5 ) differen t partitionin g o f lea din th e bone s o f

childre n compare dt o tha t o f adults , wit honl y 6 0 t o 6 5 percen t o f th e lea dbod y burde n occurrin g i

n bone , an dtha t

fractio n proba

bl y bein g mor e labil e tha n i n adults . A n importan t

aspec t o f th e dietar y habit s o f

ver y youn g childre n in connectio n wit hlea dexposur e i s thei r norma l mouthin g activity , suc ha s thumb-suck

in g o r tastin g o f

nonfoo dobjects . Suc hbehavio r pose s aris k

o f increase dcontac t

wit hdus t

an dsoi l contaminate dwit hlead . Clinica l evidenc e als o ex ist s t o indicat e childre n ar e a t specia l ris k

fo r lea d effects . Threshold s fo r anemi aan derythrocyt e protoporphyri n elevatio n ar e lowe r fo r children , an danumbe r

o f neurologica l effect s appea r a t lowe r level s o f lea din childre n tha n in adults . 1.4.3. 2 PREGNAN T WOME N Considerabl e evidenc e indicate s tha t pregnan t wome n ar e apopulatio n segmen t a t ris k wit hrespec t t o lea dmainl y becaus e o f increase dris k

t o th e fetu s an dmaterna l complications . Lea dcrosse s th e pla

centa l barrie r

an ddoe s s o at

a n earl y stag e in embryoni c development . Althoug hquantitativ e ex pression s o f

thi s ris k canno t b e stated , certainl y th e potentia l fo r

damag e exists . Pregnanc y place s aphysiologica l stres s o n a woma n in term s o f

nutritiona l state s tha t

lea dt o iro n an dcalciu mdeficiency , in consequenc e o f whic h 1-1 4P.4 1



### bon e lea dma y b e mobilize dandth e hematopoieti c syste mma y be place da

t higher ris k t o lea dex posure . I n addition , dat asugges t

that elevate dbloo d lea dlevel s i

n pregnan t

wome n ma y resul t i n in

crease dincidenc e o

f prematur e membran e rupture , placin g th e mother

a s well as her

newbor n i n a specia l ris k category . 1.4.3. 3 UNITE D STATE S POPULATIO N I N RELATIO N T O PROBABL ELEA D EX

POSURE S Wit hth e exceptio n o

f thos e livin g i

n area s wit

h primary leadsmelters , mos t population s expose dt o lea dliv e i n urban areas . Resident s o f th e centra l cit

y ar e a t th e highes t

ris k i n thes e urban areas . There

fore , fo r othe r than point

stationary source s o

f lead , i t i s th e urban populatio n that i s a t risk , an di

n par ticular , centra l cit

y residents . Black s an dHispanic s are probabl y subject

t o greate r

exposure t o airborn e lea dbecaus e higher

proportion s o

f thes e segment s o

f th e populatio n liv e i n urban areas . I

n th e Unite d State s i n 1970 , 149 millio n person s wer e reporte dt o liv e i n urban areas , and64 millio n i n th e centra l cities . Thes e figure s includ e abou t 1 2 millio n childre n unde r

5 year s o f age , wit happroximatel y 5 millio n o f thes e childre n livin g i

n central-city areas . Ther e ar e a

n estimate d600,00 0 childre n i n th e Unite dState s wit

hbloo dleadvalue s greate r than 4 0 /xg/dl . Thes e value s d o not resul t fro mexposure t o airborn e lea

dalone ; they als o includ e exposure t o leade dpain t

an dleadi

n food . In vie

w o f th e narro w margi n o f safet y fro mcurrentl y observe durban bloo dleadlevels , childre n expose dt o a n additiona l increment o f leadfro mth e ai r woul db e at

great ris k fo r advers e healt

heffects . O f th e roughl y 3 millio n U.S . pregnancie s pe r year , inner-city wome

n ar e estimate dt o account fo r 500,000 . I n vie w o f availabl e data , thes e wome n and thei r unbor n childre n ar e als o a

t highrisk .

1-1 5

## 2 . INTRODUCTIO N

Accordin g t o Sectio n 10 8 o f th e Clea n Ai r

Ac t o f 1970 , a s amende din Jun e 1974 , acriteri adocumen t fo r aspecifi c pollutan t

o r clas s o f pollutant s shal l

. . . accuratel y reflec t

th e lates t

scientifi c knowledg e usefu l in indicatin g th e kin d an dexten t

o f al l identifiabl e effect s o n publi c healt ho r

welfar e whic hma y b e ex pecte dfro mth e presenc e o f suc hpollu

tan t i n th e ambien t

air , in varyin g quan tities . Ai r qualit y criteri aar e o f

necessit y base do n pre sentl y availabl e scientifi c data , whic hin tur n reflec t th e sophisticatio n o f

th e technolog y use di

n obtain

in g thos e dat aa s wel l a s th e magnitud e o f th e experi

menta l effort s expended . Thu s ai r qualit y criteri afo r atmospheri c pollutant s ar e ascientifi c expressio n o f curren t knowledg e an duncertainties . Specifically , ai r qualit y criteri aar e expression s o f th e scientifi c knowledg e o f

th e relationship s betwee n variou s con centrations

—average dove r asuitabl e tim e perio d—

o f pollutant s i

n th e sam e atmospher e an d thei r advers e effect s upo n publi c healt han dth e en vironment . Criteri aar e issue dt o hel p mak e deci

sion s abou t

th e nee dfo r

contro l o f

apollutan t

an d abou t th e developmen t

o f ai r qualit y standard s governin g th e pollutant . Ai r qualit y criteria ar e descriptive; tha t

is , the y describ e th e effect s tha t hav e bee n observe dt o occu r a s aresul t

of externa l ex posur e a t specifi c level s o f

apollutant . I n contrast , ai r qualit y standards ar e prescriptive; tha t is , the y prescrib e wha t

apolitica l jurisdictio n ha s deter

mine dt o b e th e maximu mpermissibl e exposur e fo r a give n tim e in aspecifie dgeographi c area . I n th e cas e o f

criteri afo r

pollutant s tha t

appea r in th e atmospher e onl y in th e ga s phas e (an dthu s re mai n airborne) , th e sources , levels , an deffect s o f ex posur e mus t

b e considere donl y a s the y affec t th e huma n populatio n throug hinhalatio n o f o r externa l contac t withtha t

pollutant . Lead , however , i s foun din th e atmospher e pri

maril y a s inorgani c particulate , wit honl y asmal l fractio n normall y occurrin g a s vapor-phas e organi c lead . Consequently , inhalatio n an dcontac t ar e bu t tw o o f th e route s b y whic hhuma n population s ma y b e expose dt o lead . Som e particulat e lea dma y re mai n suspende di n th e ai r an dente r

th e huma n bod y onl y b y inhalation , bu t othe r lead-containin g parti

cle s wil l b e deposite do n vegetation , surfac e waters , dust , soil , pavements , interio r an dexterio r

surface s o f housin g —in fact , o n an y surfac e in contac t with th e air . Thu s criteri afo r lea dmus t

b e develope dtha t will tak e int o accoun t

al l principa l route s o f ex posur e o f

th e huma n population . Thi s criteri adocumen t set s fort hwha t

i s know n abou t th e effect s o f

lea dcontaminatio n in th e en vironmen t

o n huma n healt han dwelfare . Thi s re quire s tha t

th e relationshi p betwee n level s o f ex posur e t o lead , vi aal l route s an daverage dove r a suitabl e tim e period , an dth e biologica l response s t o thos e level s b e carefull y assessed . Assessmen t o f ex posur e mus t

tak e int o consideratio n th e tempora l an dspatia l distributio n o f lea dan dit s variou s form s in th e environment . Thi s documen t

focuse s primaril y o n lea da s foun d i n it s variou s form s in th e ambien t atmosphere ; in orde r t o asses s it s effect s o n huma n health , however , th e distributio n an dbiologica l availabilit y o f lea din othe r environmenta l medi ahav e bee n considered . Th e rational e fo r

structurin g th e documen t wa s base dprimaril y o n th e tw o majo r question s o f

ex posur e an dresponse . Th e firs t portio n o f

th e docu

men t i s devote dt o lea din th e environmen t —physi

ca l an dchemica l properties ; th e monitorin g o f lea d i n variou s media ; sources , emissions , an dconcentra tion s o f lead ; an dth e transpor t an dtransformatio n o f lea dwithi n environmenta l media . Th e latte r sec tio n i s devote dt o biologica l response s an deffect s o n huma n healt han decosystems . A n effort ha s bee n mad e t o limi t

th e documen t

t o ahighl y objectiv e analysi s o f

th e scientifi c dat abase . Th e scientifi c literatur e ha s bee n reviewe dthroug hMarc h1977 . Th e reference s cite dd o no t constitut e acomplet e bibliograph y bu t

the y ar e hope dt o b e sufficien t t o reflec t th e curren t

stat e o f knowledg e o n thos e issue s mos t relevan t t o th e establishmen t

o f a n ai r qualit y standar dfo r

lead . Th e statu s o f

contro l technolog y fo r lea dha s no t bee n treated . Fo r

informatio n o n th e subject , th e reade r i s referre dt o appropriat e contro l technolog y documentatio n publishe db y th e Offic e o f Ai r Qualit y Plannin g an dStandard s (OAQPS) , EPA . Th e subjec t

o f adequat e margi n o f

safety stipulate d in Sectio n 10 8 o f

th e Clea n Ai r

Ac t als o i s no t treate dhere ; thi s topi c will b e considere din dept h b y EPA' s Offic e o f

Ai r Qualit y Plannin g an dStan

dard s in documentatio n prepare da s apar t o f th e proces s o f

establishin g a n ai r

qualit y standard . 2- 1

## 3 . CHEMICA L AN D PHYSICA L PROPERTIE S

3 1 ELEMENTA L LEA D Lea di s agray-whit e meta l o f brigh t luste r that , becaus e o f

it s eas y isolatio n an dlo w meltin g poin t (327.4°C) , wa s amon g th e firs t o f th e metal s t o b e place di n th e servic e o f

man . Lea dwa s use da s earl y a s 200 0 B.C . by th e Phoenicians , wh o travele da s fa r a s Spai n an dEnglan dt o min e it . It s mos t abundan t or e i s galena , in whic hlea di s presen t a s th e sulfid e (PbS) , an dfro mwhic hmetalli c lea di s readil y ob

taine db y roasting . Th e meta l i s soft , malleable , an d ductile ; i

t i s apoo r

electrica l conductor , an di t i s highl y imperviou s t o corrosion . Thi s uniqu e com binatio n o f

physica l propertie s ha s le dt o it s us e i n pipin g an droofing , an di n container s fo r

corrosiv e liquids . B y th e tim e o f

th e Roma n Empire , i

t wa s al

read y i n wid e us e i

n aqueduct s an dpubli c wate r systems , a s wel l a s in cookin g an dstorag e utensils . Lea di s uniqu e amon g th e toxi c heav y metal s i n tha t i t i s relativel y abundan t

i n th e earth' s crust ; it s abundanc e i s estimated 1 t o b e mor e tha n 100 time s tha t o f cadmiu man dmercury , tw o othe r systemi c metalli c poisons . Th e grea t environmenta l signifi

canc e o f lea di s th e resul t

bot ho f it s utilit y an do f

it s abundance ; lea di s produce din fa r large r quantitie s tha n an y othe r

toxi c heav y metal , withworl dpro ductio n exceedin g 3. 5 millio n ton s pe r year. 2 Th e propertie s o f

elementa l lea d(Pb ) ar e summarize din Tabl e 3-1 . TABL E 3-1 . PROPERTIE S O F ELEMENTA L LEA D Propert y Descriptio n Atomi cweigh t Atomi cnumbe r Oxidatio n state s Densit y Meltin g poin t Boilin g poin t Covalen t radiu s (tetrahedral ) Ioni cradi i Resistivit y 207.1 9 8 2 +2 , + 4 11.35g/cm 3 at20° C 327.4° C 1744° o C 1.4 4 A 1.2 1 A(+2) , 0.7 8 A(+4 ) 21. 9 xlO" 6 ohm/c m Ther e ar e eigh t

isotope s o f

lead : Fou r

ar e stabl e an dfou r ar e radioactive . Th e averag e abundance s o f th e stabl e isotope s an dth e deca y characteristic s o f th e radioactiv e isotope s ar e liste din Tabl e 3-2 . Th e stabl e isotopi c composition s o f naturall y occurrin g lea dore s ar e no t

identical , bu t

rathe r sho w varia

tion s reflectin g geologica l evolution. 3 Ther e i s n o radioactiv e progenito r

for 2<)4 Pb . However , 206 Pb , 207 Pb , an d2tm P b ar e produce db y th e radioactiv e deca y o f

238 U , 23S U , an d232 Th , respectively . Thu s th e observe disotopi c ratio s depen do n th e U/P b an d Th/P b ratio s o f

th e sourc e fro mwhic hth e or e i s derive dan dth e ag e o f th e or e deposit . Th e 2(| oPb/ 204 P b isotopi c ratio , fo r example , varie s fro m approximatel y 16. 5 t o 21 , dependin g o n th e source. 4

TABL E 3-2 . ISOTOPE S O F LEA D Isotop e 204 R b 206p b 207 R b 208 p b 210 p b 210 p b 211 p b 211p b 212 p b 212 p b 214p b 214 R b Averag e

abundance . % 1.4 26. 3 20. 8 51. 5 — — — — — — — — Deca ymod e

Stabl e Stabl e Stabl e Stabl e Ii a Ii a Ii a ii a Energy . Me V

— — — 0.01 7 0.04 7 1.4 0.8 2 0.3 6 0.2 4 0.72 0.35 Half-lif e

Stabl e Stabl e Stabl e Stabl e 2 2 y r 2 2 y r 36. 1 mi n 36. 1 mi n 10. 6 h r 10. 6 h r. 26. 8 mi n 26. 8 mi n 

### 3. 2 GENERA L CHEMISTR Y O F LEA D Lea di s th e heavies t

elemen t i n Grou p IV B o f

th e periodi c table ; thi s i s th e grou p tha t als o contain s carbon , silicon , germanium , an dtin . Unlik e th e chemistr y o f

carbon , however , th e inorgani c chemis

tr y o f lea di s dominate db y th e divalen t ( + 2 ) oxida

tio n stat e rathe r

tha n th e tetravalen t

( +4 ) oxidatio n state . Thi s importan t

chemica l featur e i s adirec t resul t o f th e fac t tha t th e strength s o f

singl e bond s betwee n th e Grou p I V atom s an dothe r atom s generall y decreas e a s th e atomi c numbe r o f th e Grou p I V ato mincreases. 5 Thus , th e averag e energ y o f aC- H bon di s 10 0 kcal/mole , an di t i s thi s facto r tha t stabilize s CH 4 relativ e toCH r Fo r lead , th e Pb

H energ y i s onl y approximatel y 6 5 kcal/mole , an d thi s i s to o smal l t o compensat e fo r th e Pb(II ) —

* Pb(IV ) promotiona l energy . I t i s thi s sam e feature , o f course , tha t

explain s th e marke ddifferenc e in th eP.4 4

tendencie s t o catenatio n show n b y thes e elements . Thoug hC- C bond s ar e presen t in literall y million s o f compounds , lea di s no t know n t o forman y cate nate dinorgani c compounds . A listin g o f

th e solubilitie s an dphysica l propertie s o f th e mor e commo n compound s o f lea di s give n in Appendi x B . A s ca n b e discerne dfro mthos e data , mos t inorgani c lea dsalt s ar e sparingl y solubl e (e.g. , PbF 2 , PbCl 2 ) o r

virtuall y insolubl e (PbS0 4 , PbCr0 4 ) i

n water ; th e notabl e exception s ar e lea d nitrate , Pb(N0 3 ) 2 , an dlea dacetate , Pb(OCOCH 3 ) 2 . Inorgani c lea d(II ) salt s ar e generall y relativel y high-melting-poin t

solid s withcorrespondingl y lo w vapo r pressure s at

roo mtemperatures . Th e vapo r pressure s o f

th e mos t

commonl y encountere dlea d salt s ar e als o tabulate din Appendi x B . Th e deca y o f lea dsalt s in th e atmospher e i s discusse din Sectio n 6.2.2 . 3. 3 ORGANOMETALLI C CHEMISTR Y O F LEA D Th e propertie s o f

organolea dcompound s (i.e. , compound s containin g bond s betwee n lea dan dcar bon ) ar e entirel y differen t fro mthos e o f

th e in

organi c compound s o f

lead . Th e Pb- C bon denerg y i s approximatel y 130 kcal/mole, 6 o r twic e th e Pb- H valu e cite dabove . Consequently , th e organi c chemistr y o f

lea di s dominate db y th e tetravalen t ( + 4 ) oxidatio n state . An importan t propert y o f

mos t organolea dcompound s i s tha t the y underg o photo

lysi s whe n expose dt o light . Th e physica l propertie s o f som e o f

th e mor e importan t

organolea dcom pound s ar e summarize din Tabl e 3-3 . TABL E 3-3 . PROPERTIE S O F MAJO R ORGANOLEA D COMPOUND S Compoun d Tetramethy l lea d Tetraethy l lea d Tetrapheny l lea d Hexamethy l lea d Hexaethy l lea d Formul a (CH 3 ) 4 P b (C 2 H 5 ) 4 P b (C 6 H 5 ) 4 P b (CH 3 ) 6 Pb 2 (C 2 H 5 ) 6 Pb 2 Appearanc e Colorles s liqui d Colorles s liqui d Whit e soli d Pal e oi l Yello woi l m.p. . C -27. 5 -13 0 22 3 3 8 3 6 b.p. . C

11 0 82 a Decompose s Decompose s 100 b A t 1 3 m m pressure . A t 2 m m pressure . Becaus e o f

thei r us e a s antiknoc k

agent s in gasolin e an dothe r

fuels , th e mos t

importan t organolea dcompound s ar e th e tetraalky l com pound s tetraethy l lea d(TEL ) an dtetramethy l lea d (TML) . A s woul db e expecte dfo r suc hnonpola r compounds , TE Lan dTM Lar e insolubl e in wate r bu t solubl e in hydrocarbo n solvent s (e.g. , gasoline) . Thes e tw o compound s ar e manufacture din ex tremel y larg e quantitie s (Chapte r 5) b y th e reactio n o f th e alky l chlorid e withlead-sodiu malloy: 7 4NaP b + 4C 2 H,C 1 —(C 2 H 5 ) 4 P b + 3P b + 4NaC I Th e methy l compound , TML , i s als o manufacture d b y aGrignar dproces s involvin g th e electrolysi s o f lea dpellet s i n methylmagnesiu mchloride: 7 2CHJvlgC I + 2CH 3 C 1 (CH 3 ) 4 P b + + P b 2MgCl 2 Thes e lea dcompound s ar e remove dfro maut o o r othe r interna l combustio n engine s b y aproces s calle dlea dscavenging , in whic hthe y reac t in th e combustio n chambe r

withhalogenate dhydrocarbo n additive s (notabl y ethylen e dibromid e an dethylen e dichloride ) t o formlea dhalides , usuall y bro

mochlorolead . Suc hinorgani c compound s ap parentl y originat e a s vapor s in th e combustio n chambe r o f a n automobil e engine . Durin g thei r passag e throug hth e exhaus t system , however , the y condens e t o formsmal l spherica l particle s with diameter s o n th e orde r o f afew tenth s o f

a micrometer ; the y als o condens e o r absor b ont o th e surface s o f

co-entraine dparticle s derive dfro mth e intak e ai r

o r fro mcorrosio n o f

th e exhaus t

system . Consequently , lea dhalide s emitte dfro mautomobil e exhaus t ar e presen t

a s vapors , a s pur e soli dparticles , an da s acoatin g o n th e surfac e o f particulat e sub

strates . Mobil e sourc e emission s ar e discusse di n detai l in Chapte r

6 (Sectio n 6.2.2.1) . Severa l hundre dothe r organolea dcompound s hav e bee n synthesized , an dth e propertie s o f man y o f the mar e reporte db y Shapir o an dFrey. 7 Som e o f thes e ar e use din th e commercia l preparatio n o f organomercur y compound s use da s fungicides , an d thei r us e a s catalyst s an dstabilizer s in industria l processe s ha s bee n investigate dextensively . 3 4 COMPLE X FORMATIO N AN D CHELA TIO N Th e bondin g in organometalli c derivative s o f lea d i s principall y covalen t

rathe r tha n ioni c becaus e o f th e smal l differenc e in th e electronegativitie s o f lea d (1.8 ) an dcarbo n (2.6) . A s i s th e cas e in virtuall y al l meta l complexes , however , th e bondin g i s o f th e donor-accepto r

type , in whic hbot helectron s in th e bondin g orbita l originat e fro mth e carbo n atom . Th e dono r

atom s in ameta l comple x could , o f 3- 2course , b e almos t an y basi c ato mo r

molecule ; th e onl y requiremen t

i s tha t adonor , usuall y calle da ligand , mus t

hav e apai r

o f electron s availabl e fo r bon dformation . I n general , th e meta l ato moccupie s acentra l positio n in th e complex , a s exemplifie db y th e lea dato min tetramethy l lea d(a) , whic hi s

H 3 C # CH ,

H, C CH ,

(a ) tetrahedrall y surrounde db y fou r methy l groups . I n thes e simpl e organolea dcompounds , th e lea di s usuall y presen t

a s Pb(IV) , an dth e complexe s ar e relativel y inert . Thes e simpl e ligands , whic hbin dt o meta l at onl y asingl e site , ar e calle dmonodentat e ligands . Som e ligands , however , ca n bin dt o th e meta l ato mb y mor e tha n on e dono r atom , s o a s t o formaheterocycli c rin g structure . Ring s o f thi s genera l typ e ar e calle dchelat e rings , an dth e dono r molecule s whic hfor

mthe mar e calle dpolydentat e (a s oppose dt o monodendate ) ligand s o r chelatin g agents . I n th e chemistr y o f lead , chelatio n normall y involve s Pb(ll) , leadin g t o kineticall y quit e labil e (althoug hhighl y stable ) complexe s tha t ar e usuall y six-coordinate . A Wid

e variet y o f

biologicall y sig

nifican t chelate s withligands , suc ha s amin o acids , peptides , nucleotides , an dsimila r macromolecules , ar e known . Th e simples t structur e o f

thi s typ e i s with th e amin o acid , glycine , a s represente din (b ) fo r a 1: 2 (metal : ligand ) complex . H 2 0 O O . CH . / P b NH „ .NH . \ \ CH ,



### I • C O H 2 0 Th e importanc e o f chelatin g agent s in th e presen t contex t i s thei r widesprea dus e in th e treatmen t o f lea dan dothe r

meta l poisoning . Sinc e Pb(II ) i s arelativel y sof t (o r clas s b ) meta l ion, 8 it form s stron g bond s t o sof t dono r atom s lik e th e sulfu r

atom s in th e cystein e residue s o f protein s an denzymes ; i

t als o coordinate s strongl y wit hth e imidazol e group s o f

histidin e residue s an dwit hth e carboxy l group s o f

glutami c an dasparti c aci d residues . I n livin g systems , therefore , lea datom s bin dt o thes e peptid e residue s i n proteins , thereb y preventin g th e protein s fro mcarryin g ou t thei r func

tion s b y changin g th e tertiar y structur e o f th e protei n o r b y blockin g th e approac hb y asubstrat e t o th e ac tiv e sit e o f

th e protein . Th e rol e o f th e chelatin g agent s i s t o compet e withth e peptide s fo r th e meta l b y formin g stabl e chelat e complexe s tha t ca n the n b e transporte dfro mth e protei n an deventuall y ex crete db y th e body . Fo r simpl e thermodynami c reason s (se e Appendi x B) , chelat e complexe s ar e muc hmor e stabl e tha n monodentat e meta l complex

es , an dit

i s thi s enhance dstabilit y tha t i s th e basi s for thei r abilit y t o compet e favorabl y withprotein s an dothe r

ligand s fo r

th e meta l ions . Th e chelatin g agent s mos t

commonl y use dfo r

th e treatmen t

o f

<s > O I O-C-CH . O I<x> CH 2 -C O N-CH 2 -CH 2 - N / 

### /

J 

### \ O-C-CH . O CH 2 -C O . O EDT A (c ) CH . H S —C C H c ; CH 3 NH 2 PENICILLAMIN E O O H

(b ) (d ) 3- 3P.4 6

lea dpoisonin g ar e ethylenediaminetetraacetat e ion s (EDTA ) (c) , D-penicillamin e (d) , an dthei r deriva

tives . EDT A i s know n t o ac t a s ahexadentat e ligan d towar dmetals. 9 Recen t X-ra y diffractio n studie s hav e demonstrate dtha t D-penicillamin e i s atriden

tat e ligan d(bindin g throug hS , N , an dO ) towar d cobalt, 1 0 chromium, " an dlead, 1 2 bu t monodentat e towar dmercury. 131 5 I t shoul db e note dtha t

bot hth e stoichiometr y an d structure s o f

meta l chelat e depen do n pH , an dtha t differen t structure s may occu r

in crystal s fro mthos e manifes t in solution . I t

will suffic e t o state , however , tha t severa l ligand s ca n b e foun dtha t ar e capabl e o f sufficientl y stron g chelatio n withlea dpresen t in th e bod y unde r

physiologica l condition s t o enabl e thei r us e in th e effectiv e treatmen t o f lea dpoisoning . 3. 5 REFERENCE S FO RCHAPTE R3 1 . Moeller , T . Inorgani c Chemistry . Joh n Wile y an dSons , Inc. , Ne w York . 1953 . 96 6 p . 2 . Dyrssen , D . Th e changin g chemistr y o f th e oceans . Ambio . /(l):21-25 , 1972 . 3 . Russell , R . an dR . Farquhar . Lea dIsotope s i n Geology , lnterscience . Ne w York . I960 . 4 . Doe , B . Lea dIsotopes . Springer-Verlag , Ne w York . 1970 . p . 3-80 . 5 . Cotton , F . A . an dG . Wilkinson . Advance dInorgani c Chemistry . Joh n Wile y an dSons , Inc. , Ne w York . 1972 . 6 . Shaw , C . F. . Ill , an dA . L . Allred . Nonbonde dinteraction s i n organometalli c compound s o f Grou p I V B . Organometalli c Chem . Rev . A 30:95 , 1970 . 7 . Shapiro , H . an dF . W . Frey . Th e Organi c Compound s o f Lead , lnterscienc e Publishers , Joh n Wile y an dSons , Inc. , Ne w York , 1968,48 6 p . 8 . Basolo , F . an dR . G . Pearson . Mechanism s o f Inorgani c Reactions . J . Wile y an dSons , Inc. , Ne w York . 1967 . p . 23-25 , 113-119 . 9 . Richards , S. , B . Pedersen , J . Silverton , an dJ . L . Hoard . Stereochemistr y o f

ethylenediaminetetraacetat e complex

es . Inorg . Chem . 5:27-33 , Jan . 1964 . 10 . d e Meester . P . an dD . J . Hodgson . Mode l fo r th e bindin g o f D-penicillamin e t o meta l ion s i n livin g systems : Syn

thesi s an dstructur e o f L-histidinyl-D-penicil

laminatocobal t

(III ) monohydrate . [CO(L-his ) (D

pen)]H 2 0 . J . Am . Chem . Soc . 99( 1 ):10l-104 . 1977 . 11 . d e Meester , P . an dD . J . Hodgson . Synthesi s an dX-ra y structur e o f

L-histidinyl-D-penicillaminatocobal t (III ) an dL-histidinyl-D-penicillaminatochromiu m(111) . J . Chem . Soc . Chem . Commun . 280 , 1976 . 12 . Freeman , H . C , G . N . Stevens , an d1 . F . Taylor , Jr . Meta l bindin g i

n chelatio n therapy : Th e crysta l structur e o f D

penicillaminatolea d(II) . J . Chem . Soc . Chem . Commun . / 0:366-367 , 1974 . I 3 . Wong . Y . S. . P . C . Chieh , an dA . J . Carty . Th e interactio n o f organomercur y pollutant s withbiologicall y importan t sites . Can . J . Chem . 5/:2597 , 1973 . 14 . Wong , Y . S. , P . C . Chieh , an dA . J . Carty . Bindin g o f methylmercur y b y amino-acids : X-ra y structur e o f D , L

penicillaminatomethylmercur y (II) . J . Chem . Soc . Chem . Commun . 741 , 1973 . 15 . Carty , A . J . an dN.J . Taylor . Bindin g o f inorgani c mercur y at biologica l sites . J . Chem . Soc . Chem . Commun . 214 . 1976 .

3-4

## 4 . SAMPLIN G AN D ANALYTICA L METHOD S FO RLEA D

4 1 INTRODUCTIO N Monitorin g fo r

lea di n th e environment , whic hin

clude s samplin g an dmeasurement , i s ademandin g tas k tha t require s carefu l attention . Lea di s receivin g carefu l scrutin y a s apollutant , an dth e accurat e assessmen t

o f it s impac t

o n th e environmen t

i s con tingen t o n th e acquisitio n o f

vali dmonitorin g data . Furthermore , th e movemen t an daccumulatio n o f lea din ecosystem s occu r vi acomple x pathway s an d compartments . I n addition , man y difficultie s ar e in

heren t in th e identificatio n an dtracin g o f lea din it s variou s form s in th e environment . Airborn e lea d originate s fro mmanmad e sources , primaril y th e automobile , an di s extracte dfro mth e atmospher e b y animals , vegetation , soil , an dwater . Knowledg e o f th e concentration s o f

lea di n thes e variou s medi a an dth e movemen t

o f lea dbetwee n an damon g the m i s critica l fo r

controllin g lea dpollutio n an dfo r mitigatin g th e advers e effect s o f lea di n th e environ

men t o n people . Samplin g an danalytica l method s for monitorin g lea dhav e bee n devise dfo r almos t ever y purpose . Som e method s ar e to o tediou s o r expensiv e fo r genera l use ; other s ar e relativel y easil y applie dbu t produc e result s o f

limite dutilit y o r

questionabl e validity ; an dother s ar e appropriat e fo r us e i n monitorin g lea din certai n system s bu t no t i n others . Th e monitorin g o f

environmenta l lea dca n b e car rie dou t withalmos t

an y precisio n deeme dnecess ary , bu t actuall y obtainin g precis e an daccurat e result s i s no t

atrivia l tas k

in man y instances . (Se e Chapte r 9 fo r adiscussio n o f

th e difficultie s in reproducin g bloo dlea danalyses. ) Th e primar y proble mi s tha t

o f determinin g wha t

type s o f monitorin g procedure s ar e necessar y t o realiz e societa l objective s fo r

protectin g huma n healt ho n a practica l basis . Th e objectiv e o f thi s chapte r

i s t o revie w th e statu s o f

th e monitorin g procedure s avail

able . Anothe r

seriou s proble mi s th e presen t lac k o f instrumentatio n fo r

th e continuou s analysi s o f aero sol . Monitorin g fo r

lea dinvolve s a n operationa l se quence , base do n th e scientifi c method , a s show n schematicall y in Figur e 4-1 . Th e typ e o f dat at o b e collecte dmus t

b e define dclearl y o n th e basi s o f th e question(s ) t o b e answered . Th e require daccurac y o f th e dat amus t

b e determine dan dassure db y mean s o f aqualit y assuranc e strateg y fo r al l aspect s o f

th e monitorin g operation . Similarly , th e samplin g strateg y mus t

b e base do n th e typ e o f dat aneede d an dye t tak e int o accoun t

requirement s impose db y th e analytica l method s t o b e used . Th e selectio n an d applicatio n o f

th e analytica l method s ar e in tur n in

fluencedb y th e kin do f dat aneeded , th e type s o f sample s collected , th e analytica l capabilitie s availa

ble , an dothe r

factors . Ultimately , analysi s o f th e dat aobtaine ddetermine s whethe r th e sequenc e ha s reache dasatisfactor y conclusio n o r if modification s o f an y particula r

segment s o f

th e sequenc e ar e re quired . Althoug hther e ar e numerou s technica l source s o f

informatio n concernin g samplin g strategy , samplin g methods , sampl e preparation , an danalyses , onl y afe

w o f th e mos t noteworth y ar e cite dhere . Thes e includ e th e Nationa l Academ y o f Science s repor t

o n lead, 1 Stern' s three-volum e com pendiu mo n ai r

pollution, 2 th e Geologica l Surve y revie w o f lea din th e environment, 3 an dth e Nationa l Scienc e Foundatio n publication , "Monitorin g fo r Lea di n th e Environment." 4 I n succeedin g sections , th e specifi c operation s in

volve di n monitorin g ar e discussed . Sit e selectio n i s treate dsuccinctl y becaus e o f th e deart ho f

criteri ain th e literatur e an dth e necessit y fo r establishin g specifi c sit e criteri afo r

eac hsamplin g requirement . Muc hremain s t o b e don e towar destablishin g cri

teri afo r locatio n o f

samplers . Th e variou s sampler s use dt o collec t

lea ddat aar e described . Method s fo r collectin g dustfall , water , soil , an dvegetatio n sam ple s ar e reviewe dalon g withcurren t samplin g method s specifi c fo r

mobil e an dstationar y sources . Th e processin g o f

sample s fo r

analysi s i s critica l an d influence s th e selectio n o f filte r material s an d characteristics . Thi s i s an are ao f monitorin g tha t

i s receivin g muc hattentio n becaus e o f th e inter

ference s tha t

hav e bee n encountered . Th e analytica l sectio n i s length y becaus e o f th e 4- 1P.4 8

FORMULAT E HYPOTHESI S O R DELINEAT E QUESTION S T O B E ANSWERE D

DEFIN E TYP E O F DAT A NEEDE D AN D QUALIT YASSURANC E REQUIRE D

PLA N SAMPLIN G STRATEG Y

SELEC T SIT E CHOOS E

COLLECTIO N METHOD S DETERMIN E SAMPL E STORAG E AN D TRANSPOR T REQUIREMENT S

OBTAI N SAMPLE S

ANALYZ E SAMPLE S PREPAR E SAMPL E ! « » MEASURE I LEA D j MAK E QUALIT Y ASSURANC E CHECK S

ANALYZE/INTERPRE TDAT A HYPOTHESI S CONFIRMED ? QUESTION S ANSWERED ? N O YE S (END ) Figur e 4-1 . Sequenc e o f operation s involve d i n monitorin g fo r lea d i n th e environment . larg e variet y o f

method s applie dt o lea danalysis . Analysi s i s th e mos t

advance dare ao f

monitorin g operations , an di

f use dproperly , analytica l method s ar e alread y availabl e tha t ar e capabl e o f

providin g al l th e require ddata . 4. 2 SAMPLIN G Th e purpos e o f

samplin g i s t o obtai n lead-contain

in g particles , adsorbe dgases , liquids , an dsoli dsam ple s tha t will provid e ameasur e o f th e natur e an d concentratio n o f

lea da t

variou s point s in th e environment . Samplin g encompasse s no t onl y th e metho do f

sampl e collection , bu t als o th e selectio n o f samplin g site s an dprocedure s applicabl e t o th e processin g o f

samples . 4.2. 1 Sample rSit e Selectio n Th e locatio n o f

sampl e collectio n device s ha s im

portan t an dpervasiv e effect s o n th e dat aobtained . I n monitorin g ambien t

ai r fo r lead , th e proximit y t o th e sample r

o f mobil e an dstationar y source s i s o f prim e importance . Als o o f importanc e ar e th e heigh t o f th e sample r

intak e abov e th e groun dan dth e loca l topography , climate , an dlea dleve l in th e soil . Ott 5 ha s enumerate dth e problem s an ddifficultie s en countere din comparin g dat aobtaine dfro mai r monitorin g station s in differen t cities . Genera l guideline s fo r locatin g ambien t

ai r sampler s includ e th e following : 1 . Sampler s shoul db e aunifor mheigh t abov e th e ground , althoug ht o asses s th e ris k t o children , som e sampler s shoul dals o b e lo

cate dat achild' s heigh t

( 2 t o 3 ft) . 2 . Sample r

inlet s shoul db e at

leas t 3 mfro m an y obstruction . 3 . Sampler s shoul db e locate di n area s fre e o f loca l sourc e influenc e an dconvectio n o r edd y currents . Mos t existin g sample r

site s d o no t

mee t thes e cri

teria , an dinformatio n o n sample r locatio n i s no t usuall y provide dwit hdata. 5 Th e numbe r o f monitorin g site s in an ai r monitorin g networ k

shoul d b e relate dt o geography , population , an dsources. 6 Sinc e ther e i s n o suitable , continuou s metho dfo r measurin g lea di

n air , th e samplin g perio dan dfre

quenc y ar e als o importan t in th e overal l samplin g strategy . I t

shoul db e noted , however , tha t i t i s no t possibl e t o discus s samplin g plan s outsid e th e con tex t o f aparticula r

objectiv e (e.g. , characterizatio n o f rura l o r urba n backgroun dlevels , assessmen t o f healt hhazard s t o people , determinatio n o f sourc e effects , o r

delineatio n o f

transpor t

mechanisms). 4 Th e treatmen t

o f samplin g in detai l i s outsid e th e scop e o f thi s discussion , bu t

referenc e shoul db e mad e t o th e availabl e sources. 6 ' 7 4.2. 2 Samplin g Error s Th e fidelit y withwhic hasampl e reflect s th e quan tit y an dnatur e o f

lea din an y mediu mbein g sample d i s basi c t o th e obtainin g o f vali ddat aan dtherefor e t o a n understandin g o f th e phenomen abein g in

vestigated . I n Sectio n 4.2.1 , th e importanc e o f sit e selectio n fo r

collectin g sample s o f

airborn e lea dwa s noted . I n Sectio n 4.2.6.2 , th e problem s o f dilutio n o f sample s fro mmobil e source s ar e noted . A genera l samplin g erro r

associate dwit hsamplin g o f airborn e particulate s i s discusse dhere . Mos t ambien t

sampl e collection s ar e obtaine d nonisokinetically ; tha t

is , a s th e ai r

i s draw n int o th e sample r inlet , th e spee dan ddirectio n o f th e ai r ar e changed . Th e inertia l characteristi c o f suspende d particulate s brin g abou t losse s o f

large r particle s bot hby drif

t fro mth e sample dai r

strea man db y im

pactio n o n th e surfac e o f th e sample r

inlet . I t ha s bee n show n tha t

appreciabl e error s may resul t fro m nonisokineti c sampling , primaril y becaus e o f th e los s o f larg e particle s (thos e with diameter s exceedin g 1 0 4- 2fim). 8Generally , it i s no t possibl e t o estimat e th e er ro r unde ran y specifie dconditions . Butsuc herror s ma y b e minimize db y avoidin g edd y formation , tur bulence , divergenc e o r

convergence , an dchange s i n directio n o f

th e sample dai r

stream . 4.2. 3 Samplin g fo rAirborn e Particulat e Lea d Airborn e lea di s primaril y carrie db y particulate s o r aerosols , bu t

in smalle r

concentrations , i

t may oc cu r i n th e formo f

organi c gases . Sampler s rang e fro mth e widel y use dhigh-volum e filte r sample r t o a variet y o f

othe r collector s tha t

emplo y filters , im

pactors , an dimpingers . 4.2.3. 1 HIGH-VOLUM ESAMPLE R Th e mos t

widel y use dmetho dfor samplin g air

born e particulate s in th e 0.1

- t o ]0-fim rang e i s th e high-volum e ai r

sampler, 91 0 whic hi s routinel y use d in th e Nationa l Ai r

Surveillanc e Networks . Th e metho drequire s avacuu mcleane r typ e o f ai r blowe r tha t draw s ai r

throug hafilte r

at rate s a s hig ha s 2 m 3 /min . Sinc e th e norma l samplin g perio di s 2 4 hr , particulate s fro masampl e volum e o f abou t 200 0 m 3 ar e collected . Becaus e th e ai r flo w varie s withfilte r typ e an dth e degre e o f

filte r loading , i

t i s necessar y at leas t t o measur e initia l an dfinal ai r flows . Gros s particulat e loadin g i s determine db y carefull y weighin g th e filte r

befor e an dafte r

sampl e collec

tion . Th e lea dconten t

i s the n determine db y on e o f th e analytica l method s describe din th e following . Commercia l high-volum e sampler s i n whic hth e filte r i s hel di

n ahorizonta l plan e an dprotecte d fro mdustfal l by ahousin g ar e available. 9 An 8

- by 10-in . glas s fibe r

filte r i s usuall y recommended . Problem s withfilte r

selectio n ar e discusse din asub

sequen t section . High-volum e sampler s ar e inexpensive , eas y t o operate , an din widesprea duse . A measur e o f thei r precisio n an deas e o f

operatio n can b e deduce dfro m th e observatio n tha t

an interlaborator y relativ e stan dar ddeviatio n fo r

tota l particulat e collectio n ha s bee n reporte do f

3. 7 percen t

ove r th e rang e 8 0 t o 12 5 /ug/m- \Th e disadvantage s o f th e high-volum e sample r includ e th e lac k

o f separatio n o f

particu

late s b y size , th e interference s by impuritie s in th e filter s withsom e analytica l procedures , an dth e par ticl e fracturin g tha t

occur s o n impact , whic h preclude s subsequen t

determinatio n o f

siz e distri

bution. 9 I n addition , high-volum e sampler s ar e usuall y operate dnonisokinetically ; thi s result s i n a n underestimatio n o f

th e airborn e concentratio n o f larg e particles . "I f

ther e i s appreciabl e mas s in par ticle s withaerodynami c diameter s greate r tha n abou t

1 0 fim, thi s effec t ma y b e important . Isokineti c impacto r

measurement s ru n in Lo s Angele s hav e indicate dtha t th e mas s media n equivalen t

diameter s ar e apparentl y large r tha n thos e measure dunde r

nonisokineti c conditions. 1 2 Thi s topi c i s als o discusse di n Sectio n 6.3.2.1 . A n interlaborator y compariso n progra mbein g conducte din Europ e ha s compare dtota l particulat e result s fro mhigh

- an dlow-volum e samplers. 1 3 Base do n th e low-volum e sample r data , th e preci

sio n o f tota l particulat e collectio n o f th e high

volum e sample r

i s estimate dat

± 0. 5 /ug/m 3

. O f course , suc hcomparison s appl y onl y t o th e particu

lar condition s an dmethodolog y o f samplin g an d analysi s use din tha t

study . 4.2.3. 2 DICHOTOMOU S SAMPLE R Th e siz e distributio n o f airborn e particulate s ca n b e determine dby usin g multistag e impactor s an d impinger s o r

b y analyzin g unfractionate dsamples . Suc hinformatio n i s desirabl e for monitorin g source s o f apollutan t

a s wel l a s fo r

assessin g potentia l effect s o f th e pollutan t

o n huma n health . Th e abov e technique s ar e expensiv e t o us e o n alarg e scal e an d generall y requir e extende dsamplin g periods . Measurements' 4 hav e indicate dtha t airborn e partic

ulate s usuall y hav e abimoda l siz e distributio n an d als o tha t ther e i s adistinc t

differenc e in th e effect s o f smal l an dlarg e particle s o n humans. 1 5 A dichotomou s sample r fo r particulate s ha s bee n designe dt o collec t

an dfractionat e sample s int o tw o siz e ranges. 1 6 Th e dichotomou s sample r use s virtua l impactio n t o avoi dth e particl e bounc e error s fre

quentl y encountere dwithcascad e impactors. 1 7 Vir

tua l impactio n involve s th e separatio n o f particle s int o separat e ai r

stream s by inertia l means. 1 6 I n th e apparatus , th e larges t

portio n o f

th e ai r strea mi s pulle dthroug ha n annula r pat hs o tha t

i t change s direction , whil e asmal l ai r flow i s maintaine din a straigh t path . Th e inerti ao f

th e large r

particulate s tend s t o kee p the min th e straigh t pat hwhil e th e smalle r particle s ar e diverte dwithth e mai n stream . Tw o stage s o f

virtua l impactio n hav e bee n use dt o obtai n bette r

fractionation . Membran e filter s in th e tw o ai r path s collec t

th e respectiv e samples . Th e particl e diamete r

demarcatio n o f

th e tw o fraction s i s normall y betwee n 2. 0 an d3. 5 fim i n variou s designs . Commercia l dichotomou s sampler s ar e available , bu t

the y ar e considerabl y mor e expensiv e tha n high-volum e samplers . Test s o f aprototyp e dichotomou s sample ri n St . Loui s indicated 1 6 that8 0 percen to f th e particulat e lea dwa s containe di n particle s les s than 2 fim i n 4- 3P.5 0

diameter , wherea s onl y 2 0 percen t wa s foun dt o b e in large r particles . Othe r

test s t o evaluat e th e perfor

manc e o f dichotomou s sampler s ar e unde r way. 1 8 4.2.3. 3 TAP ESAMPLE R Thoug hdustfal l an dhigh-volum e collector s usuall y requir e 2 4 h r

samplin g period s t o obtai n a sufficien t analytica l sample , ther e ma y b e anee din sourc e an dtranspor t

studie s t o monito r

airborn e particulate s fo r

shorte r tim e intervals . Th e tap e sample r draw s ai r

throug haspo t

o n afilter

tap e tha t advance s automaticall y a t prese t interval s (e.g. , ev er y 2 hr). 9 A t

asamplin g rat e o f

abou t 0.5 6 m 3 /h r (2 0 ft 3 /hr ) fo r

a2-h r interva l an dwit ha2.54-c m ( 1 -in. ) spo t

diameter , i

t i s possibl e t o analyz e th e collecte dsampl e fo r

lea dusin g anodi c strippin g voltammetr y analysis. 1 9 Atmospheri c con centration s o f

lea drangin g fro m0. 1 t o 2. 0 /xg/m 3 wer e measure dat

monitorin g station s in Chicag o an dWashingto n usin g tap e samplers. 1 9 Diurna l cy cle s i n airborn e lea dconcentration s wer e obtaine d tha t correlat e wit hmanmad e source s o f lead . 4.2.3. 4 IMPACTOR S AN D IMPINGER S Impactor s ar e multistag e particulat e collectio n device s designe dt o provid e anumbe r o f siz e frac

tions . Th e modifie dAnderse n cascad e impacto r use din th e Nationa l Ai r Surveillanc e Network s (NASN ) i s describe dhere. 2 0 Other s ar e describe din standar dtexts. 2

- 2 1 Th e cascad e impacto r

fractionate s particle s i n a serie s o f fiv e o r si x collectio n stages. 2 0 Particle s pas s throug haserie s o f

jets , 40 0 pe r

stage , tha t

ar e progressivel y smaller . Unde r eac hserie s o f

jet s i s a collectio n plate . Th e siz e fractio n o f particle s col

lecte da t eac hstag e depend s o n th e ai r velocity , geometry , an dpreviou s stages . Th e las t stag e con sist s o f afilter . Ai r

i s pumpe dthroug hth e impacto r at 0.1 4 t o 0.1 7 m 3 /mi n b y mean s o f a n ai r pum p o n th e downstrea mside . Aluminu mfoi l i s use da s th e collector , an dth e siz e fractio n i s determine db y weighin g befor e an dafte r a24-h r

sampl e i s col

lected . Fiv e fraction s ar e usuall y obtained : < 1.1, 1. 1 t o 2.0 , 2. 0 t o 3.3 , 3. 3 t o 7 , an d> 7 ^m . Result s obtaine db y th e NASN 2 2 indicat e tha t lea d particulate s typicall y hav e mas s media n diameter s in th e rang e o f

0.2 5 t o 1.4 3 fim. Analysi s b y optica l emissio n spectrograph y indicate dtha t fo r particle s les s tha n 0. 5 fim in diameter , th e lea dconten t wa s 2 t o 4 percent . A cascad e impacto r ha s als o bee n ap plie dt o multielemen t

siz e characterizatio n o f urba n aerosols. 2 3 A size-selectiv e particl e sample r usin g cyclone s ha s als o bee n described, 2 4 an daten-fraction-siz e

sampl e ca n b e obtaine dwit hth e Lundgre n impac

tor. 2 5 Impinger s collec t

atmospheri c aerosol s b y im

pingemen t

ont o asurfac e submerge di n aliquid. 2 9 Impactor s ar e sometime s calle ddr y impingers . A s in impactors , impingemen t relie s o n th e inertia ! characteristic s o f

th e particl e fo r

collectio n o n asur face . Hig hcollectio n efficiencie s fo r particle s a s smal l a s 0. 1 fim may b e obtaine din we t impingers. 2 4.2. 4 Samplin g fo rVapor-Phas e Organi cLea d Compound s I n determinin g th e tota l quantit y o f lea din th e at mosphere , ai r

i s draw n throug hamembran e o r glas s filter fo r collectin g particulat e lea dan dthe n throug hasuitabl e reagen t o r absorbe r

fo r collectio n o f gaseou s compound s tha t pas s throug hth e filter. 2 6 Sinc e th e norma l filte r

use dha s anomina l 0.45-/u m por e size , analysi s b y thi s metho dwil l includ e an y materia l tha t

passe s throug hthes e pores , althoug hit i s considere dt o b e primaril y organi c lead . Organi c lea dma y b e collecte do n iodin e crystals , adsorbe d o n activate dcharcoal , o r absorbe di n a n iodin e monochlorid e solution. 4 Review s o f th e procedure s ar e available. 272 8 Th e procedure s usin g iodin e monochlorid e hav e bee n describe dan dar e claime dt o b e effective. 2 6 I n on e experiment , tw o bubbler s containin g th e solu

tio n wer e place din serie s i n th e samplin g train . Hea dlevel s correspondin g t o abou t 2. 0 /xg/m 3 o f organi c lea dwer e obtaine din th e firs t bubbler , wherea s th e secon dgav e ablan k response , indicatin g tha t th e collectio n efficienc y o f th e firs t bubble r wa s essentiall y 10 0 percen t

an dtha t th e metho di s quan titative . Analyse s wer e accomplishe dwithatomi c absorptio n spectrometr y afte r chelatio n o f

th e lea d an dextractio n int o a n organi c solvent . I t shoul db e noted , however , tha t

th e detectio n sensitivit y wa s lo w an dtha t

th e us e o f

bubbler s limit s th e sampl e volume . 4.2. 5 Samplin g fo rLea d i n Othe rMedi a I n som e respects , samplin g fo r lea din water , soil , dustfall , o r

vegetatio n ca n b e easie r tha n samplin g fo r airborn e lead . However , th e samplin g condition s ma y b e equall y a s comple x an dhav e afirst-orde r impac t o n th e measurements . 4.2.5. 1 WATE R Heav y metal s may b e distribute di n wate r a s ions , a s chemica l complexes , o r a s specie s adsorbe do n suspende dmatter. 4 Method s fo r samplin g an d 4- 4P.5 1

analysi s o f

lea di n wate r

hav e bee n extensivel y de

scribed. 293 0 Sampl e container s ma y b e eithe r glas s o r plastic . Thedynamicso f th e wate r

bod y shoul db e considered , an ddefine dprocedure s an dprecaution s shoul db e followed. 4 A variet y o f procedures , eac h associate dwithparticula r objectives , exist s (e.g. , separatio n o f

dissolve dan dsuspende dlea dan d preservatio n o f

wate r sample s t o retai n thei r

origina l state) . Analysi s o f

lea din wate r

i s typicall y accomplishe d withatomi c absorptio n an demissio n spectroscopy , althoug hanalytica l method s fo r othe r medi aar e als o applicable . Th e natura l lea dconten t o f lake s an driver s lie s i n th e rang e o f 1 t o 1 0 /ttg/liter , with a n averag e valu e o f

6. 6 /ug/lite r

fo r Nort hAmerica n rivers. 1 Thus , i t

i s commonl y foun dnecessar y t o concentrat e th e sampl e b y chelatin g an dextractin g th e lea do r

b y evaporatin g th e water. 3 Technique s fo r wate r analysi s hav e bee n reviewe drecentl y b y Fisherma n an dErdman. 3 1 4.2.5. 2 SOI L Lea di n soi l sample s collecte dfro mnearl y 100 0 location s aroun dth e Unite dState s range s fro mles s tha n 1 0 t o abou t

70 0 ppm , withamea n concentra tio n o f 1 6 ppm. 3 Depositio n o f lea do n soi l fro mth e atmospher e result s i n extrem e vertica l concentratio n gradients , sinc e lea di s relativel y immobil e i n soil. 4 I t ha s bee n estimate dtha t a n averag e o f

1 /xg Pb/cm 2 ' yea r

fro mrainou t

o r washou t o r both , an d 0. 2 fig Pb/cm 2 ' yea r

fro mdus t

accumulate s at

o r nea r th e soi l surface. 3 2 Horizonta l gradient s o f lea d concentration s in soi l occu r a s th e resul t

o f natura l an dmanmad e sources . Th e lea dconten t o f soi l decrease s rapidl y wit hdistanc e fro memissio n sources ; fo r

example , reduction s o f 7 5 percen t

ar e observe din movin g fro m8 t o 3 2 mfro mahigh

way. 3 3 Thi s poin t

i s discusse din detai l in Chapte r 6 . Soi l samplin g i s no t

complex. 4 Vegetatio n an d larg e object s shoul db e avoided , an darepre sentativ e sit e shoul db e selected . Th e vertica l in

tegrit y o f th e sampl e shoul db e preserve dan dnoted . Th e sampl e shoul db e air-drie dan dstore din seale d containers . Th e samplin g shoul db e planne dt o ob

tai n result s representativ e o f th e condition s bein g in

vestigated . Mos t

o f th e analytica l procedure s use d fo r airborn e particulate s ar e applicabl e t o soils , bu t th e result s ma y no t

b e comparable . Man y tech

niques , includin g optica l emissio n spectrography , X

ra y spectrography , atomi c absorption , an dth e electro n microprob e hav e bee n use dfo r soi l lea d analysis. 3 X-ra y diffractio n ha s bee n use dt o analyz e soi l sample s fo r

lea demitte db y automobiles. 3 4 4.2.5. 3 DUSTFAL L Al l particle s suspende din ai r ar e affecte db y grav itationa l settling . Th e settlin g velocitie s o f large r particle s (^ 5 t o 1 0 fim) ar e suc htha t the y wil l b e transporte dshorte r

distance s tha n th e smalle r parti

cle s ( < 1 fim), whic hhav e nearl y negligibl e settlin g velocities . Thu s dustfal l collection s ca n b e use dt o monito r th e dispersio n o f

particulat e lea dfro ma specifi c source . Th e collection s ar e mad e b y placin g ope n container s a t

appropriat e site s fre e o f overhea d obstructions. 91 0 Usin g bucket s t o measur e dustfal l ca n lea dt o inaccurat e data ; win deddie s create db y th e wall s o f

th e bucke t

ma y greatl y affec t

deposition . Th e dustfal l surfac e shoul db e smoot han dflat , pre sentin g a s littl e disturbanc e t o th e win da s possible . Thes e point s ar e discusse db y Patterson. 3 5 Dustfal l i s generall y reporte din unit s o f gram s pe r squar e mete r

pe r mont h(g/m 2 -mo ) an dma y b e analyze db y th e method s describe dfo r particulate s collecte do n filters. 9 Th e "AST M Standar dMetho d fo r Collectio n an dAnalysi s o f Dustfall " provide s detaile dprocedures. 3 6 On e compariso n o f lea d quantitie s collecte db y dustfal l an db y filtratio n in

dicate dconsistentl y tha t th e lea dconten t

o f particu

late s collecte db y filtratio n i n th e high-volum e sample r wa s highe r

tha n in dustfall. 3 7 Thi s i s aresul t primaril y o f

th e lo w settlin g velocitie s o f th e smalle r particles , whic hmak e u p asignifican t fractio n o f

th e tota l particulate . 4.2.5. 4 VEGETATIO N Lea danalysi s o f

plan t tissue s ha s bee n les s exten siv e tha n studie s in othe r media . Lea ddeposite do n lea f surface s b y fallou t

ca n b e remove dan d analyzed. 3 8 Lea din plant s i s usuall y observe dt o b e les s tha n 1 figlg dr y weight , althoug hlevel s a s hig h a s 3 1 figlg hav e bee n cited. 1 Plant s ca n absor b solu

bl e lea dfro msoils , bu t

mos t soi l lea di s in form s no t availabl e t o plants. 1 Leaf y portion s o f

plant s ofte n exhibi t highe r concentration s o f

lead , bu t

in general , a t leas t 5 0 percen t

o f thi s lea dca n b e remove db y washing. ' Sinc e th e presenc e o f lea dinsid e th e plant s may manifes t

differen t effect s tha n tha t

o n th e plan t surface , attempt s shoul db e mad e t o differentiat e be

twee n thes e tw o conditions . Littl e mentio n appear s i n th e literatur e o f method s fo r

th e fieldsamplin g o f plan t lif e fo r environmenta l studies . Th e standar dmethod s an d procedure s usuall y ar e focuse do n statistica l sam plin g fo r determinatio n o f

nutrien t element s i n foo d crops . Plan t tissu e collectio n an dtreatmen t hav e bee n reviewe db y Skogerbo e e t al. 4 Samplin g o f

plan t 4- 5P.5 2

material s i s generall y carrie dou t b y rando mselec

tio n o f th e indigenou s specie s representativ e o f a give n are ao f

interest . Wher e th e entir e plan t i s no t collected , emphasi s i s usuall y place do n th e portio n o f th e plan t consume db y herbivore s o r harveste dfo r market . I n developin g samplin g plans , ther e shoul d b e clos e coordinatio n betwee n plan t an danima l samplin g groups , especiall y wher e foodchain s ar e in

volved . Befor e analysis , adecisio n mus t b e mad e a s t o whethe r o r no t th e plan t

materia l shoul db e washe d t o remov e surfac e contaminatio n fro mfallou t an d soi l particles . If

th e plant s ar e sample din astud y of tota l lea dcontamination , o r if the y serv e a s anima l foo dsources , washin g shoul db e avoided . If th e effec t o f lea do n plan t

processe s i s bein g studied , o r i f th e plan t i s asourc e o f

huma n food , th e plan t

sam ple s shoul db e washed . I n eithe r case , th e decisio n mus t b e mad e a t

th e tim e o f

sampling , a s washin g canno t b e effectivel y use dafte r th e plan t

material s hav e dried . Neithe r

ca n fres hplan t

sample s b e store dfo r

an y lengt ho f

tim e i n atightl y close dcon taine r befor e washing , becaus e mold s an denzymati c actio n ma y affec t

th e distributio n o f

lea do n an din th e plan t tissues . Freshl y picke dleave s store din seale dpolyethylen e bag s at roo mtemperatur e generall y mol di n afe w days . Storag e tim e ma y b e increase dt o approximatel y 2 week s b y refrigeration . Method s reporte din th e literatur e fo r removin g surfac e contaminatio n var y considerably , rangin g fro mmechanica l wipin g wit hacamel-hai r brus ht o leachin g i n minera l acid s o r EDTA . Remova l o f

sur fac e contaminatio n wit hminimu mleachin g o f con stituent s fro mlea f

tissu e ca n generall y b e ac complishe db y usin g dilut e solution s o f selecte dsyn theti c detergent s followe db y rinsin g i n deionize d water . Afte r collection , plan t

sample s shoul db e drie da s rapidl y a s possibl e t o minimiz e chemica l an d biologica l changes . Sample s tha t ar e t o b e store dfo r extende dperiod s o f

tim e o r t o b e groun dshoul db e oven-drie dfo r

a t leas t 4 h r a t 70° C t o arres t enzymati c reaction s an drende r th e plan t

tissu e amenabl e t o th e grindin g process . Storag e in seale d container s i s alway s advisable . 4.2.5. 5 FOODSTUFF S I n 1972 , lea dwa s include di n th e Foo dan dDru g Administratio n Marke t Baske t Survey , whic hin

volve s nationwid e samplin g o f food s representin g th e averag e die t

o f a n 18-year-ol dmal e (i.e. , th e in

dividua l wh o o n astatistica l basi s eat s th e greates t quantit y o f

food). 3 9 Variou s foo ditem s fro mth e differen t foo dclasse s ar e purchase din loca l market s an dmad e u p int o meal s in th e proportio n tha t eac h foo dite mi s ingested ; the y ar e the n cooke do r other

wis e prepare da s the y woul db e consumed . Food s ar e groupe dint o 1 2 foo dclasses , the n composite dan d analyze dchemically . Th e quantitie s represente di n th e Tota l Die t

Surve y an dth e percentage s o f thes e food s groupe di n th e die t ar e presente din Tabl e 4-1 . TABL E 4-1 . DAILYFOO D INTAKE 3 9

I I I II I I V V V I VI I VII I I X X X I XI I Foo d grou p Dairyproduct s Meat , fish , an d poultr y Grai n an d cerea l product s Potatoe s Leafyvegetable s Legum e vegetable s Roo t vegetable s Garde n fruit s Fruit s Oils , fats , an d shortenin g Suga ran d adjunct s Beverage s (includin g water ) Tota l Foo d consumptio n Avg . g/da y consume d 75 6 29 0 36 9 204 5 9 7 4 34 8 8 21 7 5 2 8 2 69 7 292 2 % o l

tota l die t 26. 1 9. 9 12. 6 7. 0 2. 0 2. 5 1. 2 3. 0 7. 4 1. 8 2. 8 24. 9 4.2. 6 Sourc e Samplin g Source s o f

lea dhav e bee n wel l identifie dan din

clud e automobiles , smelter s (lea dan dothe r non ferrou s metals) , coal-burnin g facilities , batter y manufacturin g plants , chemica l processin g plants , an dfacilitie s fo r

scra p processin g an dweldin g an d solderin g operations . A n importan t secondar y sourc e i s fugitiv e dus t

fro mminin g operation s an d fro msoil s contaminate dwit hautomotiv e emis

sions. 3 4 A complet e discussio n o f source s o f

lea d emission s i s give n in Chapte r 5 . Th e followin g sec tion s discus s th e samplin g o f stationar y an dmobil e sources , whic hrequir e differen t samplin g methods . 4.2.6. 1 STATIONAR Y SOURCE S Samplin g o f

stationar y source s fo r

lea drequire s th e us e o f

asamplin g trai n a t

th e sourc e t o sampl e th e effluen t

stream . Bot hparticulate s an dvapor s mus t b e collecte db y th e samplin g train , an dofte n a prob e i s inserte ddirectl y int o th e stac k o r exhaus t stream . I n th e tentativ e AST M metho dfo r samplin g fo r atmospheri c lead , ai r i s pulle dthroug ha 0.45-/x mmembran e filte r an da n activate dcarbo n adsorptio n tube. 4 0 I n astud y o f manua l method s fo r 4- 6measurin g emissio n concentration s o f lea dan dothe r toxi c materials, 4 1 us e o f afilter , asyste mo f

im

pingers , ameterin g system , an dapum p wa s recom mended . Th e recommende dsolutio n in th e im

pinger s wa s nitri c acid . Mor e recently , impinge r solution s containin g iodin e monochlorid e hav e bee n show n t o b e effective. 2 6 Sinc e lea di n stac k

emission s ma y b e presen t in a variet y o f

physica l an dchemica l forms , sourc e sam plin g train s mus t

b e designe dt o tra p an dretai n bot h gaseou s an dparticulat e lead . 4.2.6. 2 MOBIL ESOURCE S A variet y o f

procedure s ha s bee n use dt o obtai n sample s o f

aut o exhaus t

aerosol s fo r

subsequen t analysi s fo r

lea dcompounds . I n on e suc hprocedure , alarg e horizonta l ai r dilu

tio n tub e wa s designe dt o segregat e fine combustion

derive daerosol s fro mlarge r lea dparticle s ablate d fro mcombustio n chambe r an dexhaus t

deposit. 4 2 I n thi s procedure , ho t

exhaus t wa s ducte dint o a56-cm

diameter , 12-m-long , ai r dilutio n tunne l an dmixe d withfiltere dambien t

ai r in a20-m-diamete r

mixin g baffl e i n aconcurren t

flo w arrangement . Tota l ex haus t an ddilutio n ai r

flow rat e wa s 2 8 t o 3 6 m 3 /min , whic hproduce daresidenc e tim e o f abou t 5 se c in th e tunnel . A t

th e downstrea men do f th e tunnel , sample s o f

th e aeroso l wer e obtaine db y mean s o f isokineti c probe s facin g upstream , usin g filter s o r cascad e impactors . Properl y designe dai r dilutio n tube s o f thi s typ e hav e ver y few aeroso l losse s fo r particle s smalle r

tha n abou t

2 fim, th e siz e tha t

ca n b e respire dint o huma n lungs. 4 3 Air-dilute daerosol s fro mcycli c aut o emission s test s hav e bee n accumulate din alarg e plasti c bag . Filtratio n o r

impactio n o f

aerosol s fro mth e ba g sample s produce s sample s suitabl e fo r lea d analysis. 4 4 Becaus e o f

th e rathe r

length y residenc e time , th e ba g techniqu e ma y resul t in th e measure men t o f anomalousl y larg e aeroso l size s becaus e o f condensatio n o f

low-vapor-pressur e organi c sub

stance s ont o th e lea dparticles . Thi s effec t ma y b e offset , however , b y fallou t processe s tha t

appl y pri

maril y t o large r

particle s (se e above) . A low-residence-tim e samplin g syste mha s bee n use dtha t i s base do n proportiona l samplin g o f ra w exhaust , followe db y ai r dilutio n an dfiltratio n o r impaction. 45 ^ 4 6 A relativel y larg e sampl e o f aeroso l constituent s ca n b e obtaine dbecaus e o f th e hig h samplin g rate s o f

th e ra w exhaust . Sinc e aconstan t proportio n o f

th e sampl e flo w t o th e tota l exhaus t flow mus t

b e maintained , thi s techniqu e ma y b e limite db y th e respons e tim e o f th e equipmen t

t o operatin g cycl e phase s tha t caus e relativel y smal l transient s i n th e exhaus t flo w rate . Mos t researc ho n aeroso l emission s i n recen t year s ha s use dvariou s configuration s o f th e horizonta l ai r dilutio n tunnel. 4 2 Severa l polyviny l chlorid e dilu

tio n tunnel s hav e bee n use dwit hgoo dsuccess. 43474 8 Thes e 46-cm-diamete r

tunnel s o f

varyin g length s hav e bee n limite db y exhaus t temperature s t o tota l flows abov e approximatel y 1 1 m 3 /min . Buildu p o f electrostati c charg e o n th e wall s o f thes e plasti c system s ca n caus e abnormall y hig hwal l losses , bu t thes e ca n b e avoide db y wrappin g th e tunne l wit ha grounde dconductiv e cabl e a t abou t 30-c minter

vals. 4 7 Simila r

tunnel s hav e bee n use di n whic ha centrifuga l fan locate dupstrea mi s use drathe r tha n apositiv e displacemen t pum p locate d downstream. 4 3 Thi s geometr y produce s asligh t posi

tiv e pressur e in th e tunne l an dexpedite s transfe r o f th e aeroso l t o holdin g chamber s fo r studie s o f

aero so l growth . Sinc e th e tota l exhaus t plu s dilutio n ai r flo w i s no t

hel dconstan t

in thi s system , ther e ma y b e sligh t sampl e disproportionation . However , thes e error s ca n b e minimize db y maintainin g aver y hig h dilutio n air/exhaus t

flo w ratio. 4 3 Ther e hav e als o bee n anumbe r o f studie s per forme dusin g tota l filtratio n o f th e exhaus t

strea mt o arriv e a t materia l balance s fo r

lea dusin g rathe r

lo w back-pressur e meta l filters. 4549

- 5 1 Th e cylindrica l filtratio n uni t

use din thes e studie s i s bette r tha n 9 9 percen t effectiv e i n retainin g lea dparticles. 5 1 Sup

portin g dat afo r

lea dbalance s generall y confir mthi s conclusion. 5 2 Thu s awid e variet y o f

samplin g an dtota l exhaus t filtration procedure s hav e bee n use dt o measur e th e mas s emission s o f

lea dcompound s fro mauto mobiles . Eac hha s it s appropriat e are ao f appli

cation , dependin g o n th e objective s o f th e variou s researc hprogra mcarrie dout . Th e ai r dilutio n tun ne l techniqu e i s mos t

convenient , i s compatibl e with th e usua l ga s emissio n measurements , an dha s therefor e bee n mos t

commonl y used . 4.2. 7 Filte rSelectio n an d Sampl e Preparatio n I n samplin g fo r

lea dparticulates , ai r i s draw n throug hfilte r

material s suc ha s fiber glass , asbestos , cellulosi c paper , o r

porou s plastics. 2 4 Thes e material s includ e trac e element s tha t ca n interfer e in th e subsequen t

analysis. 535 5 I f

th e sampl e i s large , the n th e effect s o f

thes e trac e element s ar e negligi

ble , bu t thi s i s no t

alway s th e case. 5 6 Whe n sample s ar e prepare dfo r

analysis , reductio n o f th e mas s o f filte r materia l i s ofte n accomplishe db y ashing , eithe r chemicall y o r

in a n oven. 4 Th e natur e o f th e 4- 7P.5 4

filter determine s th e ashin g technique . I n othe r method s o f

analysi s —X-ra y fluorescence , fo r ex ampl e — analysi s ca n b e performe ddirectl y o n th e filte r i f th e filte r

materia l i s suitable. 1 6 Becaus e th e natur e an dperformanc e o f filter material s ar e stil l unde r investigation , genera l criteri afo r thei r selec

tio n canno t

b e given. 4 A genera l revie w o f filte r material s i s available. 5 7 Th e mai n advantage s o f glass-fibe r

filter s ar e thei r lo w pressur e dro p an dhig hparticl e collectio n effi

cienc y a t hig hflo w rates . Th e mai n disadvantag e i s th e variabl e lea dcontent . I n on e investigatio n o f Nuclepor e filters , example s wer e give n i n whic hth e analysi s o f

sample s an dblank s showe dresult s tha t di dno t diffe r sufficientl y t o allo w us e o f th e data. 4 Other s hav e show n tha t th e variabilit y o f

residua l impuritie s i n som e glas s filter s make s thei r us e inad

visabl e i n mos t

cases, 545 5 an dthe y plac e ahig h priorit y o n th e standardizatio n o f asuitabl e filte r

fo r high-volum e samples. 5 6 Othe r investigation s hav e indicated , however , tha t glass-fibe r

filter s ar e avail

abl e no w tha t

d o no t presen t alea dinterferenc e problem. 5 8 Th e collectio n efficiencie s o f filters , an d als o o f impactors , hav e bee n show n t o b e dominan t factor s i n th e qualit y o f

th e derive ddata. 5 9 Th e rela

tiv e effectivenes s o f

dr y ashin g (eithe r

a t lo w tem perature s i n a n oxyge n plasm ao r a t hig htem peratures ) an do f

we t ashin g b y aci ddissolutio n i s a subjec t o f curren t concern . Eithe r

techniqu e wil l giv e goo dresult s if

employe dproperly. 45 5 4. 3 ANALYSI S A variet y o f

usefu l analytica l procedure s i s avail

abl e fo r determinatio n o f

lea din th e environmenta l samples . Th e choic e o f th e bes t metho di n agive n situatio n depend s o n th e natur e o f th e dat arequired , th e typ e o f

sampl e bein g analyzed , th e skil l o f th e analysts , an dth e equipmen t available . Fo r

genera l determinatio n o f

elementa l lead , atomi c absorptio n spectroscop y i s comin g int o wide r use . However , if multielemen t

analysi s i s required , an dif th e equip

men t i s available , X-ra y fluorescence ha s bee n show n t o b e capabl e o f rapid , inexpensiv e analyses. 1 6 Othe r

analytica l method s hav e specifi c advantage s tha t

cal l fo r

thei r continue dus e i n specia l studies . Onl y thos e analytica l technique s receivin g curren t

us e i n lea danalysi s ar e describe d i n th e following . Mor e complet e review s ar e availa

bl e i n th e literature. 342 9 4.3. 1 Colorimetri cAnalysi s Colorimetri c o r

spectrophotometri c analysi s fo r lea dusin g dithizon e (diphenylthiocarbazone ) a s th e reagen t ha s bee n use dfo r

man y years. 60 " 6 2 Thi s metho di s th e primar y on e recommende di n aNa

tiona l Academ y o f

Science s repor t

o n lead, 1 an di t

i s th e basi s o f

th e tentativ e metho do f testin g fo r

lea di n th e atmospher e b y th e America n Societ y fo r Testin g an dMaterials. 4 0 Becaus e o f it s history , i t

ha s serve d a s areferenc e b y whic hothe r method s hav e bee n tested . Dithizon e i s a n organi c compoun dtha t react s wit h lea dsalt s t o forma n intensel y colore dchelate dcom plex . Thi s comple x ha s a n absorptio n maximum , withaknow n extinctio n coefficient , a t awavelengt h o f 51 0 nm , whic hi s th e basi s o f th e measurement . Standard s ca n b e prepare dfo r calibratio n purpose s b y addin g know n quantitie s o f lea dt o reagents . Th e procedure s fo r

th e colorimetri c dithizon e analysi s requir e askille danalys t i f reliabl e result s ar e t o b e obtained . Th e metho dha s bee n analyzed, 4 an dth e procedure s ar e give n in th e literature. 44 0 Th e America n Societ y fo r Testin g an dMaterial s conducte dacollaborativ e tes t o f th e dithizon e method 6 3 an dconclude dtha t th e AST M dithizon e procedur e gav e satisfactor y precisio n i n th e deter

minatio n o f

particulat e lea di n th e atmosphere . Th e colorimetri c dithizon e metho dha s th e advan

tag e o f acceptabilit y b y professiona l organizations . I n addition , th e require dapparatu s i s simpl e an d relativel y inexpensive , th e absorptio n i s linearl y re late dt o th e lea dconcentration , th e metho drequire s onl y afew microgram s o f lea din th e sample , larg e sample s ca n b e used , an dinterference s ca n b e removed. 4 Realizatio n o f thes e advantage s depend s o n meticulou s attentio n t o th e procedure s an d reagents . Thi s require s arelativel y length y pro cedur e an dthu s ahig hcos t pe r sample . 4.3. 2 Atomi cAbsorptio n Analysi s Atomi c absorptio n (AA ) spectroscop y i s th e mor e generall y accepte dmetho dfo r th e measuremen t

o f lea din environmenta l sampling. 4 A variet y o f lea d studie s usin g A A analysi s hav e bee n re ported. 26

. 55

. 58

. 64

- 6 5 I n AA , th e lea ddeterminatio n i s mad e b y measur in g th e resonanc e absorptio n o f lea datoms . Th e at tenuatio n o f

th e ligh t bea mpassin g throug hth e sam pl e i s logarithmicall y relate dt o th e concentratio n o f th e atom s bein g measured . Th e lea datom s in th e sampl e mus t

b e vaporize deithe r

i n aprecisel y con trolle dflame o r

in anonflam e medium . Th e sampl e solutio n enter s th e flame throug hanebulizer . Th e lea dabsorptio n wavelength s ar e precisel y a t 217. 0 n man d283. 3 nm . Thes e wavelength s ar e produce d in ahollo w cathod e lam p containin g lead . Th e ligh t 4- 8beam , afte r passin g throug hth e flame , i s separate d i n amonochromato r

an ddetecte dwit haphoto

multiplier . A A require s frequen t us e o f calibratio n standard s t o obtai n precisio n an daccuracy . Typica l precisio n i s 1 t o 5 percent . Severa l hundre dsample s ca n b e analyze di n a n 8-h r da y if sampl e preparatio n procedure s ar e simple . I n a n analysi s usin g A A an dhigh-volum e samplers , atmospheri c concentration s o f lea dwer e foun dt o b e 0.6 3 ± 0.3 0 ng/sc ma t th e Sout hPole. 6 4 Lea danalyse s o f

99 5 particulat e sample s fro mth e NAS N wer e accomplishe db y A A t o a n indicate d precisio n o f

1 1 percent , wit ha0.1 5 /ug/m 3 detectio n limit. 5 8 Atomi c absorptio n require s a s muc hcar e a s othe r technique s t o obtai n highl y precis e data . Back

groun dabsorption , chemica l interferences , back

groun dligh t

losses , an dothe r

factor s ca n caus e er rors . A majo r

proble mwit hA A i s tha t i t ha s becom e s o popula r

tha t untraine doperator s ar e usin g i t in man y laboratories . Bu t fo r genera l purposes , A A i s th e mos t readil y applicabl e o f

an y o f th e analytica l methods . Technique s fo r

A A ar e stil l evolving , an dim

prove dperformanc e involvin g nonflam e atomiza

tio n systems , electrode-les s discharg e lamps , an d othe r equipmen t

refinement s an dtechniqu e development s ar e t o b e expected. 4 4.3. 3 Anodi cStrippin g Voltammetr y Electroanalytica l method s o f microanalysi s base d o n electrochemica l phenomen aar e foun din a variet y o f

forms. 666 7 The y ar e characterize db y a hig hdegre e o f

sensitivity , selectivity , an daccurac y derive dfro mth e relationship s betwee n current , charge , potential , an dtim e fo r electrode s in solu

tions . Th e electrochemistr y o f lea di s base dpri

maril y o n th e plumbou s ion , whic hbehave s reversi

bl y i n ioni c solution s an dha s areductio n potentia l nea r -0. 4 vol t

versu s astandar dcalome l electrode. 4 Voltammetry , th e electrometri c metho dwit h greates t sensitivit y fo r

lead , i s discusse dhere . Othe r method s ar e describe di n th e reference s cite dabove . Anodi c strippin g voltammetr y (ASV ) describe s th e proces s b y whic hth e componen t o f interest , lead , i s selectivel y deposite do n a n electrod e b y reductio n i n orde r t o concentrat e th e component. 6 6 Th e work

in g electrod e ma y b e amercur y filmo n awax impregnate dgraphit e electrode . Afte r al l o f th e lea d i n solutio n i s reduce dont o th e electrode , th e analysi s involve s astrippin g process . I n this , th e lea d i s oxidize db y mean s o f alinearl y variabl e voltag e tha t i s applie dt o th e electrode . Th e voltammogram , aplo t o f curren t versu s voltage , show s apea k corres pondin g t o th e oxidatio n o f th e lead . Th e are ao f

th e pea k correspond s t o th e quantit y o f lea dion s avail

abl e at th e strippin g voltage . AS V wa s applie dt o th e analysi s o f lea di n 2-h r sample s obtaine dwit haspo t tap e sampler. 1 9 Be

twee n 8 0 n g an d2. 4 /xg o f lea dwa s presen t

in th e samples . Th e averag e standar ddeviatio n obtaine di n th e lea dmeasurement s wa s 5. 9 percent . A detaile d procedur e fo r

sampl e preparatio n an danalysi s ha s bee n published. 1 9 Voltammetr y wa s als o use din analysi s o f particu

lat e lea dcollecte db y a n impacto r fro mth e ambien t atmosphere. 6 8 Lea dconcentration s foun dwer e i n th e 600

- t o 3000-ng/m 3 range . Curren t practic e withcommerciall y availabl e AS V equipmen t

allow s lea ddeterminatio n a t th e 1 pp b leve l wit hroutin e 5

- t o 10-percen t relativ e pre cision. 4 Extensio n t o 0.1-pp b level s i s attainabl e withmodifie dtechniques . Differentia l ASV 6 9 an ddifferential-pulse dASV 7 0 ar e reporte dt o giv e improve dsensitivit y an dt o facilitat e mor e rapi danalysis , thu s lowerin g th e cost . 4.3. 4 Emissio n Spectroscop y Optica l emissio n spectroscop y ha s bee n use dt o determin e th e lea dconten t o f soils , rocks , an d mineral s a t

th e 5

- t o 10-pp mleve l wit harelativ e standar ddeviatio n o f

5 t o 1 0 percent; 6 2 thi s metho d ha s als o bee n applie dt o th e analysi s o f alarg e num be r o f ai r samples. 58

- 7 1 Th e primar y advantag e o f thi s metho di s tha t

it allow s simultaneou s analysi s fo r alarg e numbe r

o f element s in asmal l sampl e o f th e material . Emissio n spectroscop y essentiall y consist s o f ob

servin g th e optica l emissio n spectr ao f materia l ex cite di n aspark , arc , o r flame . Th e wavelengt han d intensit y o f

th e characteristi c emissio n wavelength s o f th e element s provid e bot hqualitativ e an dquan titativ e dat ao n composition . Befor e 1960 , th e emis

sio n spectromete r

wa s th e mos t

commo n instrumen t in trace-detectio n laboratories. 7 2 Whe n use dfo r

asingl e elemen t

suc ha s lead , emis

sio n spectroscop y i s at

adisadvantag e becaus e o f th e expens e o f

th e equipment , th e require dspecia l operato r training , an dth e us e o f photographi c fil m in th e detectio n process. 4 I n astud y o f environmen

ta l contaminatio n b y automotiv e lead , samplin g time s wer e muc hreduce db y usin g asamplin g tech

niqu e in whic hlead-fre e porou s graphit e wa s use d bot ha s th e filte r

mediu man dth e electrod e i n th e spectrometer. 707 3 Lea dconcentration s o f 1 t o 1 0 4- 9P.5 6

/xg/m 3 coul db e detecte dafte r ahal f hou r flo w at 80 0 t o 120 0 ml/mi n throug hth e filter . Scot t e t al . analyze dcomposite dparticulat e sam ple s obtaine dwithhigh-volum e sampler s fo r abou t 2 4 elements , includin g lead , usin g adirect-readin g emissio n spectrometer. 7 4 Ove r 100 0 sample s col

lecte db y th e NAS N in 197 0 wer e analyzed . Carefu l consideratio n o f

accurac y an dprecisio n le dt o th e conclusio n tha t

optica l emissio n spectrometr y i s a rapi dan dpractica l techniqu e fo r analysi s o f

particu

lates . 4.3. 5 Electro n Microprob e Whe n a n intens e electro n bea mi s inciden t o n a material , it

produces , amon g othe r form s o f

radia

tion , X ray s whos e wavelength s depen do n th e ele

ment s presen t

i n th e materia l an dwhos e intensit y de

pend s o n th e relativ e quantitie s o f thes e elements . Thi s X-radiatio n i s th e basi s o f th e electro n micro

prob e metho do f

analysis . A n electro n bea mtha t give s aspo t

siz e a s smal l a s 0. 2 fim i s possible . Th e microprob e i s ofte n incorporate din ascannin g electro n microscop e tha t allow s precis e locatio n o f th e beam . Unde r

idea l conditions , th e analysi s i s quantitative , withan accurac y o f 1 t o 3 percent . Th e mas s o f th e analyze delemen t

may b e i n th e IO 1 4 t o IO" 1 6 grange. 7 5 Te r Haa r an dBayard 7 6 applie dth e electro n microprob e metho dt o th e analysi s o f th e composi

tio n o f airborn e lead-containin g particles . Particle s collecte do n membran e filter s wer e mounte do n specia l substrate s an danalyze dfo r lea dcom pounds. 7 6 Th e analysi s wa s base do n th e ratio s o f elementa l X-ra y intensities . Fro ma n environmenta l monitorin g viewpoint , th e abilit y t o determin e th e compositio n o f

comple x lea dparticulate s wit hhig h precisio n wa s demonstrated . Th e percentag e com positio n o f

lea dcompound s in th e sampl e range d fro malo w o f

0. 1 percen t

t o ahig ho f

ove r 3 7 per cent . Electro n microprob e analysi s i s no t awidel y ap plicabl e monitorin g method . I t require s expensiv e equipment , comple x sampl e preparation , an dahigh

l y traine doperator . Th e metho di s unique , however , in providin g compositio n informatio n o n individua l lea dparticles , thu s permittin g th e stud y o f dynami c chemica l change s an dperhap s allowin g improve d sourc e identification . 4.3. 6 X-Ra y Fluorescenc e X-ra y fluorescen t

emission s tha t

characteriz e th e elementa l conten t

o f asampl e occu r

whe n atom s ar e irradiate da t

sufficien t

energ y t o remov e a n inner

shel l electron. 4 Thi s fluorescenc e allow s simultaneou s identificatio n o f arang e o f

elements , includin g lead . Fo r

example , 2 2 element s wer e iden

tifie dan dquantitativel y analyze din particulat e sample s fro mdichotomou s sampler s withou t inter

mediat e sampl e preparation. 1 6 Thi s analytica l metho di s identica l t o tha t describe dfo r

th e electro n microprob e in th e precedin g sectio n bu t utilize s differen t excitatio n sources . X-ra y fluorescence require s ahigh-energ y irradia

tio n source . X-ra y tubes, 16 ' 2 3 electro n beams, 7 5 an d radioactiv e isotop e sources 7 7 hav e bee n use dexten sively. 78 ' 7 9 T o reduc e background , secondar y fluorescers hav e bee n employed. 1 6 Th e fluorescent X-ra y emissio n fro mth e sampl e ma y b e analyze d withacrysta l monochromato r an ddetecte dwith scintillation , wit hproportiona l counters, 4 o r wit h low-temperatur e semiconducto r detector s tha t discriminat e th e energ y o f th e fluorescence . Th e lat

te r techniqu e require s aver y lo w leve l o f excita

tion. 1 6 X-ra y emissio n induce db y charged-particl e ex citatio n (proton-induce dX-ra y emission , o r PIXE ) offer s a n attractiv e alternativ e t o th e mor e commo n techniques. 80 " 8 2 Recognitio n o f th e potentia l o f heavy-particl e bombardmen t fo r excitatio n occur re din 1970 , an da n interference-fre e sensitivit y dow n t o th e picogra mrang e wa s demonstrated. 8 0 Th e excellen t

capabilit y o f

accelerato r

beam s fo r

X

ra y emissio n analysi s i s partiall y du e t o th e relativel y lo w backgroun dradiatio n associate dwit h th e excitation . Th e mai n contributio n i s Bremsstrahlun g fro msecondar y electro n emission . Th e hig hparticl e fluxes obtainabl e fro maccelera

tor s als o contribut e t o th e sensitivit y o f th e PIX E method . Literatur e reviews 83 " 8 6 o n approache s t o X

ra y elementa l analysi s agre e tha t proton s o f

afew Me V energ y provid e apreferre dcombinatio n fo r hig hsensitivit y analyse s unde r condition s les s sub

jec t t o matri x interferenc e effects . A s aresul t o f thi s premise , asyste mdesigne dfo r routin e analysi s ha s bee n described, 8 1 an dpaper s involvin g th e us e o f PIX Efo r

aeroso l analysi s hav e recentl y ap peared. 81 ' 8 2 Advantage s o f

X-ra y fluorescence method s in

clud e th e abilit y t o detec t avariet y o f

elements , th e abilit y t o analyz e wit hlittl e o r n o sampl e prepara tion , an dth e availabilit y o f automate danalytica l equipment . Disadvantage s includ e th e nee dfo r lo w blan k filters , expensiv e equipment , liqui dnitroge n (e.g. , fo r

energy-dispersiv e models , an dhighl y traine danalysts . Th e detectabilit y leve l fo r lea di s abou t 2 0 ng/cm 2 of

filter area , whic hi s wel l belo w 4-1 0th e quantit y obtaine din norma l samplin g period s

wit hth e dichotomou s sampler. 1 6 4.3. 7 Method s fo rCompoun d Analysi s Colorimetry , atomi c absorption , an danodi c strip

pin g voltammetr y ar e restricte dt o measuremen t o f tota l lea dan dthu s canno t identif y th e variou s com pound s o f

lead . Th e electro n microprob e an dothe r X-ra y fluorescenc e method s provid e approximat e dat ao n compound s o n th e basi s o f th e ratio s o f

ele

ment s present. 7 6 Ga s chromatograph y usin g th e electro n captur e detecto r ha s bee n demonstrate dt o b e usefu l fo r

organi c lea dcompounds. 2 8 Powde r X

ra y diffractio n technique s hav e bee n applie dt o th e identificatio n o f

lea dcompound s i n soil. 3 4 4. 4 CONCLUSION S T o monito r

lea daeroso l in air , samplin g wit hth e high-volum e sample r

an danalysi s b y atomi c absorp

tio n spectrometr y hav e emerge da s th e mos t widel y use dmethod . Samplin g in thi s way doe s no t provid e for fractionatio n o f

th e particle s accordin g t o size , no r doe s i t allo w determinatio n o f th e gaseou s (organic ) concentrations ; thes e capabilitie s ma y prov e importan t

fo r specia l studies . Th e siz e distri

butio n o f

lea daeroso l i s importan t in considerin g question s regardin g exposur e b y inhalation ; sam plin g wit hcascad e impactor s o r dichotomou s sampler s i s necessar y t o suc hevaluations . T o deter

min e gaseou s lead , i t

i s necessar y t o bac k

th e filte r wit hchemica l scrubber s o r acrystallin e iodin e trap . X-ra y fluorescenc e an doptica l emissio n spectroscop y ar e applicabl e t o multielemen t analysi s an dar e convenien t

t o appl y t o th e measuremen t o f lea din suc hstudies . Becaus e o f th e man y environ

menta l variable s implici t in sit e monitoring , th e developmen t

o f usefu l biologica l monitorin g techni

que s ma y b e o f

mor e direc t

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sitin g ai r

monitor

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vironmenta l Protectio n Agency , Offic e o f Ai r Programs , Researc hTriangl e Park , N.C . Publicatio n No . AP-98 . Ma y 1971 . 1 6 p . 7 . Samplin g Locatio n Guidelines . U.S . Environmenta l Pro

tectio n Agency , Divisio n o f Atmospheri c Surveillance . Novembe r

1972 . 8 . Watson , H . H . Error s du e t o anisokineti c samplin g o f aerosols . Am . Ind . Hyg . Assoc . Q . /5(l):21-25 . 1954 . 9 . Warner , P . O . Analysi s o f Ai r Pollutants . Joh n Wile y & Sons , Ne w York . 1976 . 32 9 p . 10 . Ai r Qualit y Criteri afo r

Particulat e Matter . U.S . Dept . o f Health , Education , an dWelfare , Nationa l Ai r Pollutio n Contro l Administration , Washington , D.C . Publicatio n No . AP-49 . 1969 . 11 . Wedding , J . B. , A . R . McFarland , an dJ . E . Cermak . Larg e particl e collectio n characteristic s o f ambien t

aeroso l samplers . Envir . Sci . Tech . //:387 , 1977 . 12 . Davidson , C . I . Ph.D . Dissertation . Calif . Inst . Tech

nology , Pasadena , Calif . 1977 . 1 3 . Berlin , A. , P . De l Castilho , an dJ . Smeets . Europea n inter

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surveillanc e cascad e impacto r net work . II . Siz e distributio n measurement s o f trac e meta l components . Environ . Sci . Technol . 6( 1 2):1025-1030 , 1972 . 23 . Paciga , J . J . an dR . E . Jervis . Multielemen t siz e charac

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Internationa l Symposiu m Proceedings : Re cen t Advance s i n th e Assessmen t o f th e Healt h Effect s o f Environmenta l Pollution , Vol . 111 . Commissio n o f th e Europea n Communities . Luxembourg . 1975 . p . 1783-1788 . 28 . Shapiro , H . an d F . W . Frey . Th e Organi cCompound s o f Lead , lnterscienc e Publishers . Joh n Wile yan d Sons , Inc. . Ne wYork . 1968.486p . 29 . Standar d Method s fo rth e Examinatio n o f Wate ran d Wastewater . 13t h Ed . Amer . Publi cHealt h Assoc , Wash ington , D.C . 1971 . 30 . Kopp , J . F . an d R . C . Kroner . Trac e Metal s i n Water s o f th e Unite d States . U.S . Dept . o f th e Interior , Federa l Wate rPollutio n Contro l Administration , Cincinnati , Ohio . 1967 . 21 8 p . 3 1 . Fishman , M . J . an d D . E . Erdmann . Wate ranalysis . Anal . Chem.45(5):361R-403R . 1973 . 32 . Te rHaar , G . L. , R . B . Holtzman , an d H . F . Lucas . Lea d an d lead-21 0 i n rainwater . Nature . 2/6(51131:353-355 , 1967 . 33 . Lagerwerff , J . V . an d A . W . Specht . Contaminatio n o f roadsid e soi l an d vegetatio n wit h cadmium , nickel , lead , an d zinc . Environ . Sci . Technol . 4(7):583-586 , 1970 . 34 . Olson , K . W . an d R . K . Skogerboe . Identificatio n o f soi l lea d compound s fro m automotiv e sources . Environ . Sci . Technol . 9(3):227-230 , 1975 . 35 . Patterson , C . C . Repor t o f th e Exper t Meetin g o n Dr y Deposition . Worl d Meteorologica l Organization . Gothen burg , Sweden . 36 . America n Societ yfo rTestin g an d Materials . Standar d metho d fo rcollectio n an d analysi s o f dustfal l (settleabl e particulates) . D 1 739-70 . Annu . Boo k AST M Stand . Pt . 26 : 517-521 , 1975 . 37 . Hinners , T „ J . Kent , W . Terrill , T . Heiderscheit , R . Bur ton , an d A . V . Colucci . Metal s i n Atmospheri cParticu late s Collecte d b yH i Vo l Sample ran d b yDustfal l Bucket . U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park.N.C . 1972 . 5 3 p . 38 . Smith , W . H . Meta l contaminatio n o f urba n wood yplants . Environ . Sci . Technol . 7(7):631-636 , 1973 . 39 . Kolbye , A . C , Jr. , K . R . Mahaffey , J . A . Fiorino , P . C . Corneliussen , an d C . F . Jelinek . Foo d exposure s t o lead . Environmenta l Healt h Perspectives . Experimenta l Issu e No . 7 , Ma y1974 . 40 . America n Societ yfo rTestin g an d Materials . Tentativ e metho d o f tes t fo rlea d i n th e atmospher e b ycolorimetri c dithizon e procedure . D3112-72T . Annu . Boo k AST M Stand . Pt . 26:633-641 , 1975 . 4 1 . Coulson , D . M. , D . L . Haynes , M . F . Balazs , an d M . P . Dolder . Surve yo f Manua l Method s o f Measuremen t o f Asbestos , Beryllium , Lead , Cadmium , Selenium , an d Mer cur yi n Stationar ySourc e Emissions . U.S . Environmenta l Protectio n Agency , Researc h Triangl e Park , N.C . Pub . No . EPA-650/4-74-015 . 1953 . 42 . Habibi , K . Characterizatio n o f particulat e lea d i n vehicl e exhaust—experimenta l techniques . Environ . Sc . Technol . 4(3):239-248 , 1970 . 43 . Trayser , D . A. , E . R . Blosser , R . A . Creswick , an d W . R . Pierson . Sulfuri caci d an d nitrat e emission s fro m oxida tio n catalysts . SA E Tech . Pap . (750091):!-15 , 1975 . 44 . Te rHaar , G . L. , D . L . Lenane , J . N . Hu , an d M . Brandt . Composition , size , an d contro l o f automotiv e exhaus t par ticulates . J . Ai rPollut . Contro l Assoc . //(l):39-46 , 1972 . 45 . Sampson , R . E . an d G . S . Springer . Effect s o f exhaus t ga s temperatur e an d fue l compositio n o n particulat e emissio n fro m spar k

ignitio n engines . Environ . Sci . Technol . 7(l):55-60 , 1973 . 46 . Ganley . J . T . an d G . S . Springer . Physica l an d chemica l characteristic s o f particulate s i n spar k ignitio n engin e ex haust . Environ . Sci . Technol . S(4):340-347 , 1974 . 47 . Moran , J . B. . M . J . Baldwin , O . J . Manary , an d J . C . Valenta . Effec t o f fue l additive s o n th e chemica l an d physica l characteristic s o f particulat e emission s i n automotiv e exhaust . U.S . Environmenta l Protectio n Agen cy . Researc h Triangl e Park , N . C . Pub . No . EPA-R2-72 - 066 . 1972 . 48 . Gentel . J . E. . O . J . Manary . an d J . C . Valenta . Charac terizatio n o f particulate s an d othe rnon-regulate d emis sion s fro m mobil e source s an d th e effect s o f exhaus t emis sion s contro l device s o n thes e emissions . U.S . Environ menta l Protectio n Agency , An n Arbor , Mich . No . APTD-1567 . 1973 . 49 . Hirschler , D . A. . L . F . Gilbert , F . W . Lamb , an d L . M . Niebylski . Particulat e lea d compound s i n automobil e ex haus t gas . Ind . Eng . Chem . 49(1):\ 131- 1 142 , 1957 . 50 . Hirschler , D . A . an d L . F . Gilbert . Natur e o f Lea d i n ex haus t gas . Arch . Environ . Health . 5:297-313 . 1964 . 5 1 . Habibi , K . Characterizatio n o f particulat e matte ri n vehi cl e exhaust . Environ . Sci . Technol . 7(3):223-224 . 1973 . 52 . Kunz , W . G. , Jr. . E . S . Jacobs , an d A . J . Pahnke . Desig n an d performanc e o f muffle rlea d trap s fo rvehicles . Pre sente d befor e Unio n Indersyndica l d e I'ndustri e d u Petrole . Paris , France . Januar y1975 . 53 . Gandrud , B . W . an d A . L . Lazrus . Desig n o f syste m fo r removin g water-solubl e material s fro m IPC-147 8 filte r paper . Environ . Sci . Technol . 6(5):455-457 , 1972 . 54 . Luke , D . L. , T . Y . Kometani , J . E . Kessler , T . C . Loomis , J . L . Bove , an d B . Nathanson . X-ra yspectrometri c analysi s o f ai rpollutio n dust . Environ . Sci . Technol . 6(13): ! 105- 1 109 , 1972 . 55 . Kometani , T . Y. , J . L . Bove , B . Nathanson , S . Sieben berger , an d M . Magyar . Dr yashin g o f airborn e particulat e matte ro n pape ran d glas s fiberfilter s fo rtrac e meta l analysi s b yatomi cabsorptio n spectrometry . Environ . Sci . Technol . 6(7):617-620 , 1972 . 56 . Witz , S . an d R . D . Macphee . Effec t o f Differen t Type s o f Glas s Filter s o n Tota l Suspende d Particulate s an d Thei r Chemica l Compounds . Souther n Californi a Ai rPollutio n Contro l District , Tech . Service s Report . Jul y1976 . 9 p . 4-1 257 . Skogerboe , R . K . Monitorin g trac e meta l particulates : A n evaluatio n o f th e samplin g an d analysi s problems . Ameri ca n Societ yfo rTestin g an d Materials , Philadelphia , Pa . Specia l Pub . 555:125-136 , 1974 . 58 . Scott , D . R. , W . A . Loseke , L . E . Holboke , an d R . J . Thompson . Atomi cabsorptio n an d optica l emissio n analysi s o f NAS N atmospheri cparticulat e sample s fo r lead . Environ . Sci . an d Technol . /0.877-88O . 1976 . 59 . Skogerboe , R . K. , D . L . Dick , an d P . J . Lamothe . Evalua tio n o f filte rinefficiencie s fo rparticulat e collectio n unde r lo wloadin g conditions . Atmos . Environ . //(3):243-249 , 1977 . 60 . Sandell , E . B . Colorimetri cDeterminatio n o f Trace s o f Metals , lnterscienc e Publishers , Inc. , Ne wYork . 1944 . 6 1 . Horowitz , W. , P . Chichilo , an d H . Reynold s (eds.) . Offi cia l Method s o f Analysi s o f th e Associatio n o f Officia l Analytica l Chemists . I 1t h Ed . Associatio n o f Officia l Analytica l Chemists , Washington , D . C . 1970 . 101 5 p . 62 . Officia l Standardize d an d Recommende d Method s o f Analysis . W . Heffe ran d Sons , Ltd , Cambridge , Mass . 1963 . 63 . Foster , J . F. , G . H . Beatty , an d J . E . Howes , Jr . In terlaborator yCooperativ e Stud yo f th e Precisio n an d Ac curac yo f th e Measuremen t o f Lea d i n th e Atmospher e Usin g th e Colorimetri cDithizon e Procedure . America n Societ yfo rTestin g an d Materials , Philadelphia , Pa . AST M Dat a Serie s Pub . DS55-S5 . 1975 . 7 9 p . Zoller , W . H. , E . S . Gladney , an d R . A . Duce . At mospheri cconcentration s an d source s o f trac e metal s a t th e Sout h Pole . Science . 183:\ 98-200 , 1974 . Huntzicker . J . J. . S . K . Friedlander , an d C . I . Davidson . Materia l balanc e fo rautomobile-emitte d lea d i n Lo s Angele s Basin . Environ . Sci . Technol . 9(5):488-457 , 1975 . 66 . Willard , H . H. , L . L . Merritt . Jr. , an d J . A . Dean . Instru menta l Method s o f Analysis . 5t h ed . D . Va n Nostran d Co . Ne wYork . 1974 . 86 0 p' . Sawyer , D . T . an d J . L . Roberts . Jr . Experimenta l Electrochemistr yfo rChemists . Wile yan d Sons , Ne w York . 1974 . Harrison . P . R. . W . R . Matson . an d J . W . Winchester . Tim e variation s o f lead , copper , an d cadmiu m concentra tion s i n aerosol s i n An n Arbor . Michigan . Atmos . En viron . 5:613-619 . 1971 . Zirino , A . an d M . L . Healy . ph-controlle d differentia l voltammetr yo f certai n trac e transitio n element s i n natura l waters . Environ . Sci . Technol . 6(3)243-249 , 1972 . 70 . Copeland.T . R.J . H . Christie , R . K . Skogerboe , an d R . A . Osteryoung . Effec t o f supportin g electrolyt e concentratio n i n pulse d strippin g voltammetr ya t th e thi n fil m mercur y electrode . Anal . Chem . 45(61:995-996 , 1973 . 71 . Environmenta l Contaminatio n Cause d b yLead . Prepare d unde rNS F Grant s GI-34813X I an d GI-4442 3 b yCol orad o Stat e University , For t Collins , Colo . H . W . Edward s (ed.) . Interi m repor t fo rth e perio d Januar yI t o Decembe r 3 1 , 1974 . 6 4 6 5

6 7 6 8

6 9 72 . Ward , F . N . an d M . J . Fishman . Analytica l method s fo r th e determination s o f lead . In: Lea d i n th e Environmen t (T . G . Lovering , ed.) . U.S . Geologica l Surve yProfessiona l Pape r957:

81-84 , 1976 . 73 . Seeley , J . L . an d R . K . Skogerboe . Combine d sampling analysi s metho d fo rth e determinatio n o f trac e element s i n atmospheri cparticulates . Anal . Chem . 46(3):415-421 . 1974 . 74 . Scott , D . R. . W . A . Loseke . L . E . Holboke , an d R . J . Thompson . Analysi s o f atmospheri cparticulate s fo rtrac e element s b yoptica l emissio n spectrometry . Appl . Spectrosc . J0(4):392-405 , 1976 . 75 . T . D . McKinley , T . D . an d K . F . J . Heinric h (eds.) . Th e Electro n Microprobe . Joh n Wile yan d Sons , Inc . Ne w York . 1966 . 103 5 p . 76 . Te rHaar , G . L . an d M . A . Bayard . Compositio n o f air born e lea d particles . Natur e 232:553-554 , 1971 . 77 . Kneip , T . J . an d G . R . Lauer . Isotop e excite d X-ra y fluorescence . Anal . Chem . 44( I4):57A-58A . 1972 . 78 . Birks , L . S . X-ra yabsorptio n an d emission . Anal . Chem . 44(5):557R-562R . 1972 . 79 . Birks . L . S. . J . V . Gilfrich . an d D . J . Nagel . Large-Scal e Monitorin g o f Automobil e Exhaus t Particulate—Method s an d Costs . NR L Memorandu m Repor t 2350 . Nuclea r Scienc e Division . Nava l Researc h Laboratory . Washing ton . D.C . 1971 . 2 6 p . 80 . Johansson . T . B. . R . Akselsson . an d S . A . E . Johansson . X ra yanalysis : Elementa l trac e analysi s a t th e 10" 1 2 level . Nucl . Instrum . Method s (Eng.) . 84(I):!4 I -143 . 1970 . 8 I . Johansson . T . B. . R . E . Va n Grieken . J . W . Nelson , an d J . W . Winchester . Elementa l trac e analysi s o f smal l sample s b yproton-induce d X-ra yemission . Anal . Chem . 47(61:855-860 . 1975 . 82 . Hardy . K . A . R . Akselsson . J . W . Nelson , an d J . W . Winchester . Elementa l constituent s o f Miam i aeroso l a s a functio n o f particl e size . Environ . Sci . Technol . /0(2):I76-182 . 1976 . 83 . Walter , R . L. . R . D . Willis , W . F . Gutknecht , an d J . M . Joyce . Analysi s ofbiological . clinical , an d environmenta l sample s usin g proton-induce d X-ra yemission . Anal . Chem . 46(71:843-855 . 1974 . 84 . Gilfrich . J . V . P . G . Burkhalter . an d L . S . Birks . X-ra y spectrometr yfo rparticulat e ai rpollution— Aquantitativ e compariso n o f techniques . Anal . Chem . '45(121:2002-2009 . 1973 . 85 .

86 . Folkmann , F. . C . Gaarde , T . Huus , an d K . Kemp . Proton induce d X-ra yemissio n as a too l fo rtrac e elemen t analysis . Nucl . Instrum . Method s (Eng.) . //6(3):487-499 , 1974 . Herman , A . W. . L . A . McNelles , an d J . L . Campbell . Choic e o f physica l parameter s i n charge d particle-induce d X-ra yfluorescenc e analysis . Int . J . Appl . Radiat . lsotop . (Eng.) . 24(121:577-688 , 1973 .



### 4-1 3

## 5 . SOURCE S AN D EMISSION S

5. 1 NATURA L SOURCE S Lea denter s th e biospher e fro mlead-bearin g mineral s i n th e lithospher e throug hbot hnatura l an d human-mediate dprocesses . Measurement s o f sur fac e material s take n a t

8-in . depth s i n th e continen

ta l Unite dStates 1 sho w amedia n lea dconcentratio n o f 1 5 ppm . Ninety-fiv e percen t o f thes e measure ment s sho w 3 0 pp mo f

lea do r less , wit hamaximu m sampl e concentratio n o f 70 0 ppm . I n natura l pro cesses , lea di s firs t

incorporate din soi l i n th e activ e soi l zone , fro mwhic hi t ma y b e absorbe db y plants , leache dint o surfac e waters , o r erode dint o windborn e dusts. 2 5 I n addition , minut e amount s o f radioactiv e 210 P b reac hth e atmospher e throug hth e deca y o f rado n ga s release dfro mth e earth. 6 Becaus e lea dha s bee n use dfo r centuries , i t

i s difficul t t o determin e th e rang e o f natura l back

groun dlevels . Calculation s o f natura l contribution s usin g geochemica l information , however , indicat e tha t natura l source s contribut e arelativel y smal l amoun t o f lea dt o th e environment . Fo r example , i

f th e typica l 2 5 t o 4 0 ju-g/m 3 o r rura l airborn e particu

lat e matte r

wer e derive dfro msurfac e material s con tainin g 15 , an drarel y mor e tha n 30 , pp mlea da s cite dabove , the n th e natura l contributio n t o air

born e lea dwoul drang e fro m0.000 4 t o 0.001 2 Mg/m 3

. I n fact , level s a s lo w a s 0.001 2 t o 0.02 9 /ug/m 3 hav e bee n measure da t asit e i n California' s Whit e Mountains. 7 I n contrast , however , annua l averag e lea dconcentration s in urba n suspende dpar ticulat e matter 8 rang e a s hig ha s 6 /Lig/m 3

. Clearly , therefore , mos t

o f thi s urba n particulat e lea dstem s fro mman-mad e sources . 5. 2 MAN-MAD E SOURCE S 5.2. 1 Productio n Lea doccupie s a n importan t positio n in th e U.S . economy , rankin g fourt hamon g th e nonferrou s metal s i n tonnag e used . Th e pattern s o f it s flo w throug hindustr y ar e identifie di n Figur e 5-1. 9 Ap

proximatel y 8 5 percen t o f th e primar y lea dpro duce di n thi s countr y i s fro mnativ e mines, 1 0 wher e it i s ofte n associate dwit hmino r amount s o f

zinc , cad

mium , copper , bismuth , gold , silver , an dothe r

minerals. 1 0 Missour i or e deposit s accoun t fo r abou t 8 0 percen t

o f th e domesti c production .

EXTERNA L EMISSION S

SCRA P 59 8

DOMESTI C ORE S 48 3 FOREIG N ORE S 9 6 META L IMPORT S 9 0 SECONDAR Y

PLANT S 51 2

PRIMAR Y PLANT S 58 2 TOTA L

SUPPL Y 136 3 META L PRODUCT S 24 5 CERAMIC S AN D PIGMENT S 7 2 ALKYL S 19 0

BATTERIE S 63 4

OTHE R 3 6

EXPOR T 1 9 UNREPORTE D USE S AN D STOC K CHANGE S 18 7 Figur e 5-1 . Approximat

e flo wo f lead throug h U.S . industr y i n 1975 , metri c tons. 9 5.2. 2 Utilizatio n Th e reporte duse s o f

lead , liste db y majo r

produc t categorie s i n Tabl e 5-1, " stoo da t nearl y 1. 2 millio n M T in 1975 , wit ha n estimate dconsumptio n fo r 197 6 o f 1.3 5 millio n MT. 1 2 Certai n products , especiall y batteries , cables , plumbing , weights , an dballast , contai n lea dtha t i s economicall y recoverabl e a s secondar y lead . Thi s reserv e o f

lea di n us e i s estimate da t 3. 8 millio n MT , o f whic habou t

0. 6 millio n M T i s recovere dan nually . Lea di n pigments , gasolin e additives , am munition , foil , solder , an dstee l product s i s widel y disperse dan dtherefor e i s largel y unrecoverable . 5- 1P.6 1

TABL E 5-1 . U.S . CONSUMPTIO N O F LEA D B YPRODUC TCATEGORY 1 1 (MT/yr ) Produc t categor y Storag e batterie s Gasolin e antiknoc k additive s Pigment s an d ceramic s Ammunitio n Solde r Cabl e covering s Caulkin g lea d Pip e an d shee t lea d Typ e meta l Bras s an d bronz e Bearin g metal s Weigh t ballas t Othe r Tota l 197 1 616,58 1 (679,803) a 239,66 6 (264,240 ) 73,70 1 (81,567 ) 79,42 3 (87,567 ) 63,50 2 (70,013 ) 47,99 8 (52,920 ) 27,20 4 (29,993 ) 41,52 3 (45,781 ) 18,87 6 (20,812 ) 18,18 0 (20,044 ) 14,77 1 (16,285 ) 15,83 0 (17,453 ) 41,12 8 (45,345 ) 1,298,38 3 (1,431,514 ) 197 2 661,74 0 (729,592 ) 252,45 4 (278,340 ) 80,91 7 (89,214 ) 76,82 2 (84,699 ) 64,65 9 (71,289 ) 41,65 9 (45,930 ) 20,39 2 (22,483 ) 37,59 2 (41,447 ) 18,08 9 (19,944 ) 17,96 3 (19,805 ) 14,43 5 (15,915 ) 19,32 1 (21,302 ) 43,80 3 (48,294 ) 1,349,846 (1,488,254 ) 1973 697,88 8 (769,447 ) 248,89 0 (274,410 ) 98,65 1 (108,766 ) 73,09 1 (81,479 ) 65,09 5 (71,770 ) 39,00 6 (43,005 ) 18,19 2 (20,057 ) 40,52 9 (44,685 ) 19,88 3 (21,922 ) 20,62 1 (22,735 ) 14,20 1 (15,657 ) 18,90 9 (20,848 ) 42,11 0 (46,428 ) 1,397,87 6 (1,541,209 ) 1974 772,65 6 (851,881 ) 227,84 7 (251,210 ) 105,40 5 (116,213 ) 78,99 1 (87,090 ) 60,11 6 (66,280 ) 39,38 7 (43,426 ) 17,90 3 (19,739 ) 34,23 8 (37,749 ) 18,60 8 (20,516 ) 20,17 2 (22,240 ) 13,25 0 (14,609 ) 19,42 6 (21,418 ) 42,68 0 (47,056 ) 1,450,679 (1,599,427 ) 1975 634,36 8 (699,414 ) 189,36 9 (208,786 ) 71,71 8 (79,072 ) 68,09 8 (75,081 ) 52,01 1 (57,344 ) 20,04 4 (22,099 ) 12,96 6 (14,296 ) 35,45 6 (39,092 ) 14,70 3 (16,211 ) 12,15 7 (13,404 ) 11,05 1 (12,184 ) 18,15 6 (20,018 ) 36.36 8 (40,097 ) 1,176,46 5 (1,297,098 ) a Shor t lons/y rgive n i n parentheses . 

### 5.2. 3 Emission s Leado r it s compound s ma

y ente r th e environmen t a t an y step durin g it s mining , smelting , processing , use , or disposal . Recent

estimate s o

f th e dispersal o

f leademission s into th e environmen t b y principal source s indicat e that

th e atmosphere i s th e major in

itial recipient . Estimate dlea demission s t o th e at mosphere i

n 197 5 ar e shown i

n Tabl e 5-2 . Mobil e an dstationary source s o f lea demissions , althoug hfoundthroughou t th e nation , ten dt o be concentrate di

n area s o f highpopulatio n density , wit hth e exceptio n o

f smelters . Figure 5- 2 show s th e approximat e location s of

major leadmines , primary smelters , alky l leadplants , andmanufacturer s o f leadstorag e batteries. 1 3 

### 5.2.3. 1 MOBIL ESOURCE S Th e larges t

source , b y far , o f leademission s t o th e atmosphere i s th e exhaus t o f moto r vehicle s powere d b y gasolin e tha t

contain s leadadditives. 1 4 

### Thes e mobile-sourc e emission s collectivel y constitut e a n estimate d8 8 percen t

o f tota l lea demission s (Tabl e 5-2). 9 

### Othe r

mobil e sources , includin g aviatio n usag e of leade dgasolin e an ddiese l an dje t fue l com bustion , contribut e insignificant leademission s t o th e atmosphere . Leadparticulate s emitte di n automotiv e exhaus t ma y b e divide dinto tw o siz e classes . Particle s in

itiall y forme db

y condensatio n o

f leadcompound s i

n th e combustio n gase s ar e quit e smal l i n siz e (well under 0. 1 fim i

n diameter) . Particle s i

n thi s siz e categor y that become airborn e ca

n remai n sus pende di n th e atmosphere fo

r long period s an dthu

s ca n trave l substantial distance s fro mth e original sources . Large r

particle s ar e als o forme da s aresult o f agglomeratio n o

f smalle r condensatio n particles . 5- 2TABL E 5-2 . ESTIMATE D ATMOSPHERI C LEA D EMISSION S FO R TH E UNITE D STATES , 1975»•» Sourc e categor y Annua l emissions , MT/y r Emission s a s percentag e o f Subtota l Mobil e subtota l 142,00 0 10 0 Gasolin e combustio n Stationar ysubtota l Wast e oi l combustio n Soli d wast e incineratio n Coa l combustio n Oi l combustio n Gra yiro n productio n Iro n an d stee l productio n Secondar ylea d smeltin g Primarycoppe rsmeltin g Or e crushin g an d grindin g Primarylea d smeltin g Othe rmetallurgica l Lea d alky l manufactur e Typ e meta l Portlan d cemen t productio n Pigment s Miscellaneou s Tota l 142,00 0 19,22 5 10 0

10 0 10,43 0 1,63 0 40 0 10 0 1,07 9 84 4 75 5 61 9 49 3 •40 0 27 2 1,01 4 43 6 31 3 11 2 54. 3

8. 5 2.1 ' 0. 5 5. 6 4. 4 3. 9 3. 2 2. 5 2. 1 1. 4 5. 3 2. 3 1. 6 0. 6 32 8 161,22 5 1. 7 88. 1 6. 5 1. 0 0. 2 0. 1 0. 7 0. 5 0. 4 0. 4 0. 3 0. 2 0. 2 0. 6 0. 3 0. 2 0. 1 0. 2 10 0 a Inventor ydoe s no t includ e emission s fro m exhaustin g workroo m air . burnin g o f lead-painte d surfaces , weldin g o f lead-painte d stee l structures , o rweatherin g o f painte d surfaces .

O LEA D SMELTIN G AN D REFININ G PLANT S (7) ; • TETRAMETHY L AN D TETRAETHY L LEA D PLANT S (5 ) PRIMAR YPRODUCTIO N FO R 197 6 = 652 , 87 7 M T ASTORAG E BATTER YMANUFACTURER S ( > 188 ) Figur e 5-2 . Locatio n o

f majo r lea d operation s i n th e Unite d States , 1976. 1 ' • LEA D MINE S (2 5 LARGEST) ; PRODUCTIO N = > 95 % O F DOMESTI C OUTPU T 5-3P.6 3



### Thes e large r

particles , whic

hma y b e ten s o

f micrometer s or

larger i n diameter , behav e i

n th e at mosphere lik

e th e larger

leadparticulate s emitte d fro mmos t stationary source s andfall t o th e groun d i n th e vicinit

y o f th e traffi c producin g them . Th e dis

tributio n o

f leadexhaus t

particle s between th e smaller an dlarge r

siz e range s appear s t o depen don anumber o f factors , includin g th e particular drivin g pattern i n whichth e vehicl e i s usedan dit s pas t driv

in g histor y (Chapte r

6) . Bu t a s a n overal l average , it ha s bee n estimated 1 5 

### that

durin g th e lifetime o

f th e vehicle , approximatel y 3 5 percen t o f th e leadcon taine di n th e gasolin e burne db

y th e vehicl e wil l b e emitte da s fine particulate , an dapproximatel y 4 0 percen t wil l b e emitte das coars e particulate . Th e re mainde r o f th e lea dconsume di

n gasolin e combus

tio n i s deposite di

n th e engin e andexhaus t

system . Engin e deposit s are , i

n part , graduall y transferre dt o th e lubricatin g oi l andremove dfro mth e vehicl e whe n th e oi l i s changed . Moreover , som e oil s an d lubricant s contai n lea

dnaphthenat e a s adetergent . Th e fat e o f spent oi l an dit s lea

dconten t i s o f con siderabl e importance . A measure o f it s significanc e i s reflecte di

n th e wast e oil combustio n value s i

n Ta

bl e 5-2 . In addition , som e o f th e leaddeposite di

n th e exhaus t

syste mgraduall y flake s off

, i s emitte di

n th e exhaus t

a s extremel y larg e particles , an drapidl y fall s into th e street s an droad s wher e i t i s incorpor

ate dinto th e dus t

an dwashe dint o sewer s o r ont o ad

jacen t soil . Th e us e o f leadadditive s i

n gasoline , whichwas increasin g i

n tota l volum e fo

r man y years , i s no

w decreasin g a s car s designe dt o us e lead-fre e gasolin e constitut e agrowin g portio n o f th e total automotiv e populatio n (see Section 7.1.1) . Regulation s promul

gate db y EPA 1 6 

### that

limi t th e averag e concentratio n o f lea dadditive s i

n gasolin e will contribut e t o a further reductio n i

n future automotiv e leademis

sions . 5.2.3. 2 STATIONAR Y SOURCE S A s show n i n Tabl e 5- 2 (base do

n 197 5 emission estimates 9 

### ) , soli dwast

e incineratio n an dcombustio n o f wast e oi l ar e th e principa l contributor s o f lead emission s fro

mstationary sources , accountin g fo r two-third s o

f stationary sourc e emissions . Th e manufacture o

f consumer

product s sucha s lea

d glass , storag e batteries , an dleadadditive s fo r gasolin e als o contribute s significantly t o stationary sourc e leademissions . Sinc e 1970 , th e quantity o f lea demitte dfro

mth e metallurgica l industry ha s decrease dsomewha

t becaus e o

f th e applicatio n o

f contro l equipment

an dth e closin g o

f several plants , particularl y i n th e zin c andpyrometallurgica l indus

tries . A ne w locu s fo

r leademission s emerge di n th e mid-sixties , however , wit hth e openin g o

f th e "Viburnu mTrend " o r

"New LeadBelt " i

n south

easter n Missouri . Th e presenc e of seve n mine s an d tw o accompanyin g lea

dsmelter s i

n thi s are amake s i

t th e larges t

lead-producin g distric t

i n th e worl dan d ha s move dth e Unite dState s into firs t plac e amon g th e world' s |ead-producin g nations . A n extensiv e study t o asses s th e impac t o f th e expandin g lea

din

dustr y i n Missouri an dt o stimulat e ne w emissio n contro l technolog y ha s been initiated. 1 7 

### Althoug hsom

e contaminatio n o

f soi l an dwater occur s a s aresul t

o f suchmechanism s as leachin g fro mmin e an dsmelter

wastes , quantitativ e estimate s o f th e extent

o f thi s contaminatio n ar e no t available . Spillag e o f or e concentrate s fro

mopen truck s an d railroa dcars , however , i s known t o contribut e sig

nificantly t o contaminatio n alon g transportatio n routes . Fo r

example , alon g tw o route s usedb y ore truck s i n southeastern Missouri , lea dlevel s i n lea f litte r range dfro

m200 0 t o 500 0 figlg a

t th e road

way , declinin g t o afairly constan t 10 0 t o 20 0 figlg beyon dabou t

40 0 f t fro mth e roadway. 1 7 

### Another possibl e sourc e o

f lan dor water con taminatio n i s th e disposal o f particulat e leadcol

lecte db y ai r pollutio n contro l systems . Th e poten tial fo r impac t on soil andwater

system s o

f th e dis

posa l o f dust s collecte db

y thes e contro l system s ha s no t been quantified . Th e lead-containin g particle s emitte dfro msta tionary source s occur

i n variou s sizes . Thos e emitte d fro muncontrolle dstationary source s generall y in

clud e particle s larger

than 1

- t o 2-fim mas s mea n diameter , an dtherefore ten dt o settl e out nea r th e source . Thes e large-particle emission s ad dcon siderabl e leadt o th e dust , soil , water , an dvegetatio n i n th e neighborhoo do

f th e sourc e (se e Sectio n 7.2) . Uncontrolle dsource s als o contribut e substantia l quantitie s o

f smaller-diamete r

particle s t o th e at mosphere , where iong-rang e transport ma y occur . When control s ar e applie dt o stationary sources , th e tota l mas s o

f th e emission s i s reduce dsignificantly . Bu t th e number

o f particle s bein g emitte dma y no t b e affectedgreatl y i

f mos t o f th e particle s emitte d ar e small , becaus e curren t particulat e contro l method s ar e usuall y more effectiv e i n removin g th e larger-diamete r

particles . Th e smaller-diamete r particle s (belo w 2 fim) ma y be fa r greate r i n number than th e larger , more massiv e particles ; an dwit h diminishin g size , a

n increasin g proportio n i s likel y t o escap e collection . Generally , contro l method s ar e 5-4

### applie dt o emission s fro mstacks , vents , an dothe r proces s outlets . Bu

t lead-containin g particle s ma y als o b e emitte da s fugitiv e dust s i n th e larger

siz e rang e (>2-fim diameter ) fro mles s controllabl e source s suchas window s an ddoors , conveyors , an d wast e piles . Availabl e emissio n inventorie s d o no t includ e emission s fro

mth e exhaus t

o f workroo mair , burnin g o

f lead-painte dsurfaces , weatherin g o f lead-painte dsurfaces , etc . Th e magnitud e o f emis

sion s fro mthes e source s i s unknown . 5. 3 REFERENCE S FO RCHAPTE R5 1 . Shacklette , H . T. , J . C . Hamilton , J . G . Boerngen , an dJ . M . Bowles . Elementa l Compositio n o f Surficia l Material s i n th e Conterminou s Unite dStates . U.S . Geologica l Survey . Washington , D.C . Professiona l Pape r 574-D . 1971 . 7 4 p . 2 . Chamberlain , A . C . Interceptio n an dretentio n o f radioac

tiv e aerosol s b y vegetation . Atmos . Environ . 4:57-77 , 1970 . 3 . Chow , T . J . an dC . C . Patterson . Th e occurrenc e an dsig

nificanc e o f

lea disotope s i n pelagi c sediments . Geochim . Cosmochim . Acta . (London) . 26:263-308 , 1962 . 4 . Lead : Airborn e Lea di n Perspective . Nationa l Academ y o f Sciences . Washington , D . C . 1972 . 33 0 p . 5 . Patterson , C . C . Contaminate dan dnatura l lea denviron

ment s o f man . Arch . Environ . Health . 77:334-360 , 1965 . 6 . Burton , W . M . an dN . G . Stewart . Us e o f long-live d natura l radio-activit y a s an atmospheri c tracer . Nature . 756:584-589 , 1960 . 7 . Chow , T . J. , J . L . Earl , an dC . B . Snyder . Lea daeroso l baseline : Concentratio n at Whit e Mountai n an dLagun a Mountain , California . Science . 7 78(4059):401-402 , 1972 . 8 . Akland , G . G . Ai r

Qualit y Dat afo r

Metals , 197 0 throug h 1974 , fro mth e Nationa l Ai r Surveillanc e Network . U.S . 1 0 I I Environmenta l Protectio n Agency , Researc hTriangl e Park , N.C. , Pub . No . EP A 600/4-76-401 . 1976 . Contro l Technique s fo r Lea dAi r

Emissions . (Draf

t final report. ) Offic e o f

Ai r Qualit y Plannin g an dStandards , U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , N.C . EP A Contrac t No . 68-02-1375 . 1976 . 42 4 p . Minera l Fact s an dProblems . U.S . Burea u o f Mine s Bulleti n 667 , U.S . Departmen t o f Interior , Washington , D.C . 1975 . p . 1243 . Lea dIndustr y i

n Ma y 1976 . Minera l Industr y Surveys . U.S . Departmen t

o f Interior , Burea u o f

Mines , Washing

ton , D.C . Augus t

1976 . Cited

in: Contro l Technique s fo r Lea dAi r

Emissions . (Draf

t fina l report. ) Offic e o f Ai r Qualit y Plannin g an dStandards , U . S . Environmenta l Pro

tectio n Agency , Researc hTriangl e Park , N . C . EP A Con

trac t No . 68-02-1375 . 1976 . 42 4 p . Commodit y Dat aSummaries , 1977 . U.S . Departmen t o f Th e Interior , Burea u o f Mines , Washington , D . C . Januar y 1977 . Commodit y Files , 1976 . U.S . Dept . o f Interior , Burea u o f Mines , Washington , D.C . 1976 . 14 . EPA' s Positio n o n th e Healt hImplication s o f Airborn e Lead . U.S . Environmenta l Protectio n Agency , Washing

ton , D.C . 1973 . 11 6 p . Te r Haar , G . L. , D . L . Lenane , J . N . Hu , an dM . Brandt . Composition , size , an dcontro l o f automotiv e exhaus t

par ticulates . J . Ai r

Poll . Contro l Assoc . 22(l):39-46 , 1972 . Federa l Register . Regulatio n o f fuel s an dfue l additives . 5S(234):33 . 734-33 . 741 , Dec . 6 . 1973 . Wixson , B . G . an dJ . C . Jennet t (eds.) . An Interdisciplin

ar y Investigatio n o f

Environmenta l Pollutio n b y Lea dan d Othe r Heav y Metal s fro mIndustria l Developmen t in th e Ne w Lea dBel t

o f Southeaster n Missouri . (Interi mreport. ) Nationa l Scienc e Foundation , Researc hApplie dt o Na

tiona l Need s (RANN) , Roll aan dColumbia , Missouri , Th e Universit y o f

Missouri . 1974 . 48 0 p . 1 2 1 3

1 5 1 6 1 7



### 5- 5

## 6 . TRANSFORMATIO N AN D TRANSPOR T

6 1 INTRODUCTIO N Th e circulatio n o f

lea din th e environmen t (show n conceptuall y i n Figur e 6-1 ) illustrate s tha t lea d release dint o th e atmospher e ca. n b e delivere dt o ma n (animals ) vi asevera l routes . A t present , it

i s possibl e t o obtai n onl y qualitativ e o r semiquantita

tiv e estimate s o f

th e movemen t

o f lea dwithi n an d amon g th e variou s environmenta l media . Thi s i s largel y becaus e th e physica l an dchemica l transfor

mation s occurrin g withi n th e lea dcycl e ar e no t wel l understood . Th e purpos e o f thi s chapte r

i s t o sum mariz e th e availabl e dat atha t reflec t wha t i s know n abou t th e transformatio n an dtranspor t mechanism s controllin g th e distributio n and.fat e o f lea di n th e environmen t

in it s variou s chemica l forms . Primar y emphasi s i s place do n th e atmosphere , since.i t serve s a s th e principa l mediu mfo r transpor t

o f lea dfro m manmad e sources .

FOO D PROCESSIN G . ; WATE R : : : SUPPLIE S : :

> PLANT S •:•> : :•:•:•:•:•:•:•:•:•:•:• :

• EARTH : : ISOIL I : MININ G OPERATION S

JO'lN'D'OStR V > 

# u . r

# , , . » / ^.AUTOMOBILE S j —•- ; , L ± I

; ATMOSPHER E ; . I (LEA D AEROSO L \- : AN D ;'• ; ORGANI C LEAD ) ;'• :£:£;£ : "Ir^x^'oust':::::::!"^ ' Si::::::::::*:::*:::*:::*:* : OTHE R LEA D CONTAININ G PRODUCT S AN D WASTE S

" ' FALLOUT " " ly.'.; :-: : : : AN D RAINOU T'•:•:'•: 

## T 

## ~~ :':'.yy.'': OCEAN S #$ +

- * ^ESTUARIES - :; !

LAKE S AN D RIVER S

'•>:•:•: SEDIMENT S • : Figur e 6-1 . Simplifie d ecologi c flo wchar t fo r lea d showin g principa l cyclin g pathway s an d compartments . 6. 2 PHYSICA L AN D CHEMICA L TRANS FORMATION S I N TH E ATMOSPHER E Althoug hlea di s introduce dint o th e atmospher e primaril y in th e particulat e form , relativel y smal l amount s ar e als o emitte din th e vapo r phase . Onc e lea di s introduce dint o th e atmosphere , importan t physica l an dchemica l change s occu r befor e it s transfe r t o othe r environmenta l media . Th e discus

sio n o f thes e change s will b e divide dint o mobil e an d stationar y sourc e categories . Thi s divisio n i s some wha t arbitrar y in tha t

th e pollutant s fro mbot h sourc e categorie s ar e wel l mixe din th e atmosphere . I n thos e case s in whic hon e typ e o f sourc e predomi

nate s (e.g. , freeway s o r smehers) , th e approac h shoul db e reasonabl y realistic . 6.2. 1 Physica l Transformation s 6.2.l. l SIZ EDISTRIBUTIO N O FPARTICLE S FRO M MOBIL ESOURCE S Automotiv e exhaus t

i s th e primar y sourc e o f par ticulat e lea dintroduce dubiquitousl y int o th e at mospher e in urba n areas . Th e siz e o f th e particle s emitte dmay rang e fro mafew hundredth s o f a micromete r

in diamete r

t o severa l millimeters , de

pendin g o n th e operatin g mode , ag e o f exhaus t system , fuel lea dcontent , spee dan dload , accelera

tion , deceleration , engin e condition , an dothe r fac

tors . Numerou s environmenta l processes , includin g transformation , transport , deposition , an dmechan

ism s o f impact , ar e prominentl y influence db y th e particl e sizes . I t

i s significant , fo r

example , tha t

th e size s o f th e particle s directl y affec t th e probabilit y o f lead' s bein g transporte dvi ath e respirator y system . Becaus e o f

th e importanc e o f

lea dparticl e size s in relatio n t o numerou s environmenta l questions , th e siz e distribution s o f

thos e particle s emitte dfro m automobile s hav e bee n studie db y man y investiga

tors. 1 " 10

. Figur e 6- 2 show s th e result s o f aserie s o f

variabl e spee dtest s mad e b y Hirschle r an dGilbert 4 o n an aut o afte r

abou t 25,00 0 mile s o f

deposi t accumula

6- 1I i u p i I i •»•'»' " ' I P.6 6

tio n in th e exhaus t

system . Th e dat ademonstrat e tha t smalle r lea dparticle s mak e u p th e larges t frac

tio n o f thos e exhausted , an dtha t ther e i s significan t exhaus t syste maccumulatio n o f lea dparticle s in bot hsiz e categorie s unde r city-drivin g conditions . Durin g acceleration , releas e o f thes e accumulation s i s quit e rapidl y induced , bu t th e increase demissio n drop s of f durin g th e perio do f constan t

highwa y speed . Th e effec t

o f spee do n th e particl e siz e distri

butio n show n in Figur e 6-3 , a s foun db y Ganle y an d Springer, 3 als o demonstrate s tha t th e mea n particl e size s emitte ddecreas e wit hincreasin g speed . Th e result s o f

thes e tw o studie s impl y tha t althoug h large r lea dparticle s ar e mos t likel y t o b e deposite d in th e exhaus t

system , th e deposit s ar e release db y ablativ e processe s tha t caus e decrease s i n particl e size . Figur e 6- 4 compare s siz e distribution s a t recep to r site s in Californi awit hthos e typica l o f undilute d aut o exhaust . Th e smalle r size s at th e recepto r

site s reflec t th e decreas e in th e mea n siz e cause db y gra vitationa l settlin g an dothe r scavengin g processe s tha t occu r durin g atmospheri c transport . Figur e 6- 5 compare s differentia l mas s distributi@n s a t th e Californi arecepto r

site s withthos e a t

afreewa y site . Thes e distribution s ar e generall y bimodal , indicat

in g tha t particulat e lea din th e atmospher e may con sis t o f lea demitte db y auto s an dlea dtha t ha s bee n deposite do n surface s (soil ) an dre-entraine dvi aat mospheri c turbulenc e (fugitiv e dust) ; o r fihe bimoda l distributio n ma y reflec t emissio n patterns . Th e result s o f thes e studie s generall y indicau e tha t mor e tha n hal f o f th e lea dparticle s ar e typicall y les s tha n 1 fim in diameter , bu t

thes e estimate s ma y b e biase d b y th e failur e t o us e isokineti c samplin g technique s (se e Sectio n 4.2.3.1) . Le e e t al. 9 measure dth e concentration s an dsiz e distribution s o f

particulat e emission s fro mauto mobil e exhaus t

an dfoun dtha t

9 5 percen t

o f th e tota l particulat e lea dwa s in particle s withmas s me dia n equivalen t

diameter s (MMED ) les s tha n 0. 5 fim. Al l sample s wer e take n a t steady-cruis e condi

tion s an dthu s d o no t

represen t

th e typica l discharg e o f particle s unde r

wide-open-throttl e accelerations , decelerations , an dshort-ter mcruis e an didl e condi

tion s typica l o f

urba n traffic . Th e varyin g mode s resul t in th e discharg e o f

muc hlarge r

particles . Robinso n an dLudwig " reporte dMMIE D o f 0.2 5 fim fo r urba n an drura l areas ; 2 5 percen t o f th e par ticle s wer e smalle r

tha n 0.1 6 fim, an d2 5 percen t wer e large r

tha n 0.4 3 fim (Tabl e 6-1) . Chola k e t al., 1 2 Le e e t

al., 1 3 an dFlesch 1 4 observe dsimila r distributions ; however , thei r dat aals o indicat e tha t thes e distribution s chang e ver y littl e ove r distances . < 5 0 — 100 0 50 0

10 0 5 0

1 0 5 

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k CITY-TYP E DRIVIN G -* | o l l I 1 1 I I TOTA L LEA D EXHAUSTE D FIN E PARTICLES . 0- 5 u m _ AN D UNCLASSIFIE D LEAD : I COARS E PARTICLES , > 5 HI T A l 1 i - 

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f variou s drivin g condition s o n th e amoun t o f lea d exhausted. 4

3 0 4 0 5 0 6 0 7 0 8 0 9 0 PARTICLE S WIT H DIAMETE R <D,wl % Figur e 6-3 . Effec t o

f spee d o n siz e distributio n o f exhaus t par ticle s a t differen t roa d loa d cruis e condition s an d usin g In dolen e H O 0 fuel. 3 Gillett e an dWinchester 1 5 examine dth e effec t o f ag e o n th e siz e distributio n o f lea daerosols . The y foun d tha t lea daeroso l siz e distribution s d o no t var y greatl y fro mon e sourc e are a(essentiall y a n are ao f heav y automobil e traffic ) t o another , an dtha t th e 6- 2crometenUJ a UJOIAM UJPARTICNAMIC

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### / —

- —

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I. . 4 0 6 0 8 0 9 0 9 5 MAS S I N PARTICLE S < D , percen t Figur e 6-4 . Cumulativ e mas s distribution s fo r lea d aeroso l i n aut o exhaus t an d at Pasadena , a recepto r samplin g site . Th e absciss a i s a log-norma l scale , an d D

_i s th e aerodynamic , uni t density particl e diameter.'' '

0. 2 a. a ro < « -

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0. 1 1. 0 1 0 MEA N DIAMETE R I D I , micrometer s Figur e 6-5 . Differentia l mas s distribution s fo r lea d 1 m fro m a freeway , Ma y 1973 , an d a t Pasaden a samplin g sites , Novem be r 1972 an d February 1974 . (Th e absciss a i s th e mea n diameter , an d th e dashe d line s assum e tha t th e smalles t par ticl e siz e i s 0.0 1 /u m an d th e larges t 5 0 /im . Alo g D p = inter va l of lo g o

f aerodynami c particl e diameter ; m T= total mas s loadin g o

f lea d i n airborn e particulates ; A m = mas s o f lea d occurrin g i n a fraction , define d i n term s o f size , o f th e tota l particulates ; im/m T= fractio n o f mas s occurrin g i n a give n particl e siz e range.) 1 " lea daeroso l siz e distribution s d o no t respon d noticeabl y t o change s in weathe r withi n asourc e are adurin g 24-h r

samplin g periods . Th e result s o f thei r stud y sugges t

littl e modificatio n o f

th e charac

teristic s o f

th e lea daeroso l siz e distributio n a s a resul t o f nonprecipitativ e atmospheri c mechanism s fo r equivalen t

particl e radi i large r

tha n 0. 2 fim. Electro n microscop e studie s hav e show n tha t man y o f th e fin e particle s in exhaus t emission s ar e nearl y spherica l in shap e an dar e electron-dense . Th e coarse r

particle s ar e muc hmor e irregular , an d som e ar e filamentou s i n outline . Particle s collecte d at aconstan t

cruis e spee do f

3 0 mp hwer e foun dt o b e compose do f

acarbo n cor e o r

matrix , o n o r

in whic hwer e distribute dspherica l o r crystallin e electron-dens e lea dparticle s <0. l fim i n diameter. 31 6 Electro n micrograph s o f th e exhaus t particle s hav e show n tha t althoug hth e particl e ag gregate s o f

abou t 0. 5 fim wer e stable , sample s o f th e ga s tha t

ha dbee n inhale dshowe dmor e homogeneou s aggregate s I t o 2 micrometer s in diamete r tha n large r

aggregate s in th e exhale dgas . A simila r

effec t wa s obtaine db y drawin g th e ga s throug hahumidifier.' 7 6.2.1. 2 SIZ EDISTRIBUTIO N O FPARTICLE S FRO M STATIONAR Y SOURCE S High-temperatur e combustio n an dsmeltin g pro cesse s generat e submicrometer-size dlea dparticu

late , wherea s lea demission s fro mmateria l handlin g an dmechanica l attritio n operation s associate dwit h smelter s consis t

o f large r ( > 1 fim) dus t

particles . Actua l dat ao n th e siz e distributio n o f lea dparticle s emitte dfro mstationar y source s ar e limited . Fuga s e t al., 1 8 usin g afive-stag e impactor , obtaine dsample s in th e Mez aValle y (influence db y alea dsmelter ) an di n th e urba n are ao f Zagreb . Th e result s ar e show n i n Figur e 6-6 . A considerabl e differenc e wa s foun din th e siz e distributio n o f lea dparticle s i n th e industria l (Mez aValley ) versu s th e urba n (Zagreb ) area . I n th e industria l area , onl y 1 0 percen t o f th e lea dparticle s ha ddiameter s smalle r an d1 fim, wherea s i n th e urba n area , 7 5 percen t wer e smalle r tha n 1 fim. Thi s implie s tha t th e fugitiv e dus t

fro m th e mechanica l rathe r tha n th e direct-smeltin g operatio n i s th e primar y emission . Lea demission s fro mstationar y source s ar e proba

bl y affecte db y topographi c influence s i n amanne r simila r t o othe r

pollutants . Becaus e o f th e moun tainou s locatio n o f

hal f o f th e si x primar y lea d smelter s i n th e Unite dStates , however , an dbecaus e thes e thre e smelter s ar e probabl y th e larges t single

poin t emitter s o f

lead , th e topographi c influenc e o n transpor t an ddispersio n i s important . 6- 3P.6 8

TABL E 6-1 . COMPARISO N O F SIZ E DISTRIBUTION S O F LEAD-CONTAININ G PARTICLE S I N MAJO R SAMPLIN G AREAS 1 1

Sampl e are a Chicag o Cincinnat i Philadelphi a Lo s Angele s (DTN ) Pasaden a Verno n (rural ) Sa n Francisc o Cheroke e (rural ) Mojav e (rural ) No . O l sample s 1 2 7 7 8 7 5 3 1 1 25 %

Avg . 0.19(7) b 0.15(3 ) 0.14(3 ) 0.16(7 ) 0.1 8 0.17(4 ) 0.1 1 0.2 5 — Rang e

0.10-0.2 9 0.09-0.2 4 0.09-0.2 5 0.10-0.2 2 0.05-0.2 5 0.12-0.2 2 0.06-0.1 3 — — Distributi o

Avg . 0.3 0 0.2 3 0.2 4 0.2 6 0.2 4 0.2 4 0.2 5 0.3 1 0.2 7 i b yparticl e size . u, m

MMED a Rang e 0.16-.6 4 0.16-0.2 8 0.19-0.3 1 0.19-0.2 9 0.08-0.3 2 0.18-0.3 2 0.15-0.3 1 — — 75 %

Avg . 0.40(10 ) 0.4 4 0.4 1 0.49(7 ) 0.48(6 ) 0.4 0 0.45(2 ) 0.7 1 0.3 4 Rang e

0.28-0.6 3 0.30-0.6 8 0.28-0.5 6 0.39-0.6 0 0.13-0.6 7 0.28-0.4 7 0.44-0.4 6 — — MME D = mas s media n equivalen t diameter . Number s i n parenthese s indicat e numbe ro l sample s availabl e fo ra specifi cvalu e whe n differen t fro m tota l numbe ro f samples .

I I T MEZ A VALLE Y

ZAGRE B SEP-OC T197 1 JAINJ-FE B 197 2 _ MAY-JU L 197 2 " AUG-SE P 197 2 JAN-FE B 197 3 1 5 1 0 3 0 SO 7 0 9 0 9 5 9 9 MAS S < DIAMETER , percen t Figur e 6-6 . Cumulativ e mas s distributio n o f lea d particle s b

y size. 1 8 

### A t leas t fou r general conclusion s abou t leadfro m mobil e an dstationary source s ca n b e base don th e result s o f th e abov e studies : 1 . Leadi s emitte dint o th e atmosphere prin

cipall y i n th e particulat e form . 2 . Th e mas s median equivalen t diameter s o

f th e lead-bearin g particle s ar e typicall y les s than l fim, andth e siz e distribution s ar e fairl y unifor mfro mare at o area . 3 . Th e particl e size s i

n urban an drura l area s ar e suchtha t

th e leadca

n b e transporte d over relativel y larg e distance s vi atypical at mospheri c convectio n an dturbulenc e pro cesses . 4 . Th e siz e distribution s are suchthat signifi

cant fraction s o

f th e tota l atmospheri c lead concentration s ar e withi n th e respirabl e siz e range . 6.2. 2 Chemica l Transformations 6.2.2. 1 MOBIL ESOURC EEMISSION S Tetraethy l lead(TEL ) an dtetramethy l lead (TML) , a s well a s th e mixed-lea dalkyls , ar e used widely a s additive s i

n gasoline . Althoug hthes e organi c compound s ar e les s volatil e than gasoline , smal l amount s ma

y escap e t o th e atmospher e b y evaporatio n fro

mfue l system s o r

storag e facilities . TE Lan dTM Lar e light-sensitiv e an dunderg o photochemical decompositio n whe n they reac hth e atmosphere. 101 9 

### Th e lifetime o f TM Lappear s t o b e longer than tha t o f TEL . Exposur e o

f dus t t o TEL , bot hi n th e presenc e andabsenc e o f water vapor , result s i n sorptio n o

f organi c leadon dus t

particl e surfaces. 2 0 

### Laveskog 2 1 

### foundthat transien t

pea k leadalky l concentration s up t o 500 0 fig lead/m 3 

### i n exhaus t ga s ma y b e reache di

n acold-started , fully choked , an dpoorl y tune dvehicle . I f avehicl e wit

h suchemission s wer

e t o pas s asamplin g statio n on a stree t where th e lea

dalky l level migh

t typicall y b e 0.0 2 t o 0.04 /ng/m 3 

### o f

air , apea k o f abou t 0. 5 /ug/m3 

### coul db e measure da s th e ca r passe dby . Th e dat are porte db y Lavesko g were obtaine dwit haprocedur e that collecte dver

y smal l (10 0 ml) , short-tim e (1 0 min ) ai r samples . Th e sensitivit

y reporte dwa s much bette r than that reporte db

y othe r investigators , who hav e no t been abl e t o duplicat e hi s results. 2 2 

### Har

riso n e t al. 2 2 

### foundlevel s a s higha s 0.5 9 /xg/m3 

### (9. 7 percen t o f tota l lead ) at

abus y gasolin e servic e sta tion . Purdu e e t al. 2 3 

### measure dparticulat e an dorgani c leadi n atmospheri c samples . Som e result s ar e shown i n Table s 6- 2 throug h6-4 . Thes e dat ademonstrat e tha t i n al l o f th e citie s studied , particulat e leadlevel s ar e muchhigher

(a n averag e o

f approximatel y 2 0 6- 4P.6 9

time s higher ) tha n organi c lea dlevels . Th e result s ar e entirel y consisten t

wit hth e studie s o f

Huntzicke r e t al., 1 0 wh o repor t

a n organi c componen t o f 6 per cen t o f th e tota l airborn e lea di n Pasaden afo r a3

- da y perio di n Jun e 1974 , an do f Skogerboe, 2 4 wh o measure dfraction s in th e rang e o f 4 t o 1 2 percen t

at asit e i n For t

Collins , Colorado . I t

i s noteworthy , however , tha t

i n th e undergroun dgarag e (Tabl e TABL E 6-2 . RESULT S O F ATMOSPHERI C SAMPLING 6-4) , tota l lea dconcentration s ar e approximatel y fiv e time s thos e in th e urba n areas , an dth e per centag e o f

organi c lea dincrease s t o approximatel y 1 7 percent . Consequently , th e concentratio n o f organi c lea di n a n undergroun dgarag e sit e i s te n time s tha t

in th e ope n urba n environmen t (se e Ta

ble s 6- 2 an d6-4) , an dth e potentia l exposur e leve l i s similarl y magnified . FO R ORGANI C AN D PARTICULAT E LEAD 23 ( M g/m 3 ) Sampl e no. a 1 2 3 4 5 6 7 8 9 1 0 Avg . Cincinnat i

Organi cParticulate 0 0. 2 0. 0 0. 0 0. 2 0. 4 0. 2 0. 2 0. 4 0. 2 0. 2 0. 2 1.

5 0. 9 0. 9 1. 9 3. 7 1. 6 1.8 1. 3 1. 5 2. 4 1. 7 De n

Organi c 0. 2 0.5 d 1.4 d 0. 3 0. 2 0. 1 0. 0 0. 2 0. 2 0.5 d 0. 2 ve r

Particulat e 2. 3 1. 8 1. 6 1. 7 1. 0 1. 8 2. 2 1. 8 2. 0 — 1. 8 Washington , D.C . Organi cParticulat e 0. 0 0. 2 0. 1 0. 3 0. 1 0. 1 0. 1 0. 2 0. 4 0. 2 0. 2 1.

4 1. 4 1. 5 1.0 1. 1 0. 8 1. 7 1. 2 0. 8 1. 6 1. 2 St .

Organi c 0. 5 0. 2 0. 4 0. 2 0. 3 0. 2 0. 3 0. 4 0. 4 1.3 d 0. 3 Loui s

Particulat e 2. 0 2. 0 1. 8 2. 5 1. 9 1. 8 2. 2 2. 2 2. 0 1. 2 2. 0 Philadelphi a

Organi cParticulat e 0. 5 1.1 d 0. 2 0. 4 0. 8 0. 4 0. 0 0. 3 0. 1 0. 1 0. 3 1.3

1. 7 2. 9 2. 4 1. 1 1. 1 1. 7 2. 1 1. 8 2. 3 1. 8 Ch i Organi c 0. 2 0. 4 0. 2 1.6 d 0. 2 0. 2 0. 3 0. 1 0. 2 0. 2 0. 2 :ag o

Particulat e 5. 9 5. 6 5. 3 3. 5 4. 6 5. 5 5. 8 4. 8 5. 0 5. 1 5. 1 Sampl e no . represent s orde ri n whic h sample s wer e taken . Citie s wer e no t sample d concurrently . Al l value s ar e averag e o t tw o determinations , determine d b yNAS N metho d (6) . Organi clea d average s d o no t includ e thes e value s becaus e th e replicat e value s to rthes e sample s wer e mor e tha n twic e th e standar d deviatio n fro m th e average . TABL E 6-3 . PERCENTAG E O F PARTICULAT E VERSU S VAPOR-PHAS E LEA D I N URBA N AI R SAMPLES 2 3

Cit y Cincinnat i Denve r Washington , D.C . St . Loui s Philadelphi a Chicag o a AI I value s ar e average s Tota l lead 3 Organic . ug/ m 0. 2 0. 2 0. 2 0. 3 0. 3 0. 2 o f te n determination s particulat e P b x Particulate ,

jig/m 3 1. 7 1. 8 1. 2 2. 0 1. 8 5. 1 to o Particulate .

% o f tota l 8 9 9 0 8 6 87 8 6 9 6

TABL E 6-4 . ANALYSE S O F FIV E REPLICAT E SAMPLE S TAKE N I N A N UNDERGROUN D PARKIN G GARAGE 2 3 Organi c lead , Sampl e no . /J.g/ m 1 1. 9 2 1. 9 3 1. 9 4 1. 8 5 2. 2 Averag e (X)

1. 9 Relativ e standar d deviatio n (Srel) a 7.9 % a 0 . Standar d deviatio n ,„ „ Sre l = x10 0 Organi c lead . % 15. 7 17. 1 17. 6 14. 9 18. 0 16. 7 7.9 % Particulat e

lead , /ig/m 3 10. 3 9. 2 8. 9 10. 3 10. 0 9. 7 6.7 % Tota l

lead . Mg/m 3 12. 2 11. 1 10. 8 12. 1 12. 2 11. 6 5.2 % Averag e A s th e lea dalky l compound s o f gasolin e ar e sub

jecte dt o th e elevate dtemperature s an dpressur e o f combustion , the y ar e converte dt o lea doxides , whic hfunctio n t o inhibi t engin e knock . Th e lea dox ide s reac t

withothe r

additive s in th e fuel an dleav e th e combustio n chamber s in avariet y o f comple x compounds . Th e result s o f compositio n studie s b y Hirschle r an dGilbert, 4 Te r

Haa r e t al., 2 an dTe r Haa r an dBayard 2 5 ar e show n in Table s 6- 5 an d6-6 , respectively . Habib i e t al. 5 determine dth e compositio n o f par ticulat e matte r

emitte dfro mates t

ca r operatin g o n a typica l drivin g cycle . Th e mai n conclusion s draw n fro mth e stud y were : 1 . Compositio n o f

emitte dexhaus t

particle s i s relate dt o particl e size . 2 . Ver y larg e particle s greate r tha n 20 0 fim hav e acompositio n simila r t o lead-contain

in g materia l deposite din th e exhaus t system , confirmin g tha t

the y hav e bee n re-entraine d o r hav e flake dof

f fro mth e exhaus t

system . Thes e particle s contai n approximatel y 6 0 t o 6 5 percen t

lea dsalts , 3 0 t o 3 5 percen t ferri c oxid e (Fe 2 0 3 ) , an d2 t o 3 percen t soo t an d carbonaceou s material . Th e majo r lea dsal t i s lea dbromochlorid e (PbBrCl) , wit hlarg e amount s (1 5 t o 1 7 percent ) o f lea doxid e 6- 5P.7 0

TABL E 6-5 . AVERAG E COMPOSITIO N O F PARTICULAT E LEA D COMPOUND S EMITTE D I N AUT O EXHAUST 8 ' 2 ' 4 Compound , wt . % aNH„CI - /3NH 4 CI - 2NH 4 CI - 3Pb 3 (P0 4 lj " Exhaus t sourc e PbCIB r2PbCIB r2PbCiB rPbCIB r"bCIB r CarB : Cit ytyp e cycle , fue l plu s TE L moto rmi xonl y6 8 2 4 6 2 — Cit ytyp e cycle , adde d sultur c7 0 3 0 ——— Cit ytyp e cycle , adde d phosphorus d 3 5 1 8 1 7 1 0 2 0 Constan t speed , 6 0 mph , roa d loa d 6 0 2 0 2 0 —— Full-throttl e acceleration s 8 5 1 0 5 — - — CarM : Cit ytyp e cycle , fue l plu s TE L moto rmi xonl y3 3 4 0 5 2 2 — Constan t speed , 6 0 mph , roa d loa d 3 0 3 0 3 5 5 — Full-throttl e acceleration s 9 0 1 0 ——— a X-ra ydiffractio n analyse s mad e in situ o n materia l deposite d o n glas s slide s mounte d withi n th e precipitato ro f th e sampler . I n additio n t o th e tabulate d compounds . PbSO . an d PbO-PbCI-Br-hL O occurre d ocasionall yi n concentration s o f 5 percen t o rless . c Sulfu rconten t increase d fro m 0.02 5 t o 0.10 5 weigh t percen t byadditio n o f disulfid e oil . 0. 4 theor yphosphoru s added . TABL E 6-6 . EFFECT S O F AGIN G O N LEA D COMPOUND S I N SAMPLE S O F AUT O EXHAUS TA S DETERMINE D B YELECTRO N MICROPROBE 2 5

Percentag e o f tota l particle s sample d Blac k bag 3 Eight-Mil e Road b Lea d compoun d Zer o tim e 1 8 hou rNea rroa d 40 0 y d Rura l site 0 PbCi ^ 10 4 8 3 iT 2 10 5 5~ 4 PbBr 2 5. 5 0. 5 4. 0 0. 7 0. 1 PbBrC I 32. 0 12. 0 4. 4 0. 6 1. 6 Pb(OH)C I 7. 7 7. 2 4. 6 8. 8 4. 0 Pb(OH)B r2. 2 0. 1 2. 0 1. 1 — (PbO) 2 PbCI 2 5. 2 5. 6 2. 8 5. 6 1.5 (PbO) 2 -PbBr 2 1. 1 0. 1 0. 7 0. 3 — (PbO) 2 PbBrC I 31. 4 1. 6 2. 0 0. 6 1. 0 PbC0 3 1.2 13. 8 15. 6 14. 6 30. 2 Pb 3 (P0 4 ) 2 ——0. 2 0. 3 — PbO x2. 2 21. 2 12. 0 25. 0 20. 5 (PbO) 2 PbC0 3 1. 0 29. 6 37. 9 21. 3 27. 5 PbOPbS0 4 —0. 1 1. 0 4. 6 5. 0 PbS0 4 0. 1 —2. 2 6. 0 3. 2 Sampl e collecte d directl yfro m tailpip e i n blac k ba g t o preven t irradiatio n o f exhaust . Analyze d immediatel yan d agai n 1 8 h rlate rt o determin e effec t o f aging . Stat e highwa yi n Detroi t carryin g abou t 100,00 0 car s a day . °Sample s wer e take n 40 0 y d fro m a lightl ytravele d roadway . 

### (PbO ) occurrin g a s th e 2 PbC^PbBrC l dou

- b y X-ray diffraction . Thi s i s particularl y bl e salt . Leadsulfate an dleadphosphat e ac - tru e fo r particle s i

n th e 2

- t o 0.5-micromete r coun t fo r 5 t o 6 percen t

o f thes e deposits . siz e range . (Thes e composition s resulte dfro mth e com - 6 . Ther e i s considerabl y more soo t andcar bustio n o f low-sulfur

an dlow-phosphoru s bonaceou s materia l associate dwit hsmal l fuel. ) particle s tha n wit hcoars e particle s re 3 . PbBrC I i s th e major

leadsal t i n particle s of

2 entraine dafte r havin g been deposite dafte r t o 1 0 micrometer s equivalen t diameter , wit

hemissio n fro

mth e exhaus t

system . Thi s car 2 PbBrC I -NH4 

### C 1 present a s amino r

constit

- bonaceou s materia l account s fo r 1 5 t o 2 0 uent . percen t o f th e fine r particles . 4 . Submicrometer-size dlea dsalt s ar e pri

- 7 . Particulat e matte r emitte dunder

typical maril y 2PbBrCl-NH 4 

### Cl . drivin g condition s i s ric hi n carbonaceous

5 . Lead-haloge n mola

r ratio s i n particle s o

f typ e material . Ther e i s substantiall y les s such les s than 1 0 micron s MME D indicat e tha t materia l emitte dunde r continuou s ho t muchmor e haloge n i s associate dwit hthes e operation . solid s than th e amount

expecte dfro

mth e 8 . Onl y smal l quantitie s o f 2PbBrCl«NH 4 

### C I presenc e o

f 2PbBrCl»NH 4 

### Cl , a s identifie dwere foundi n sample s collecte da

t th e tail

6- 6P.7 1

pip e fro mth e ho t

exhaus t gas . It s formatio n therefor e take s plac e primaril y durin g cool

in g an dmixin g o f

exhaus t withambien t

air . Hirschle r an dGilbert 4 foun dsimila r result s an d speculate dtha t

highe r ga s temperatur e durin g full

throttl e operation s reduce dth e tendenc y fo r th e am monium-lea dhalid e complexe s t o b e presen t sinc e the y ar e unstabl e at

hig htemperatures . Base do n th e abov e studies , it seem s quit e clea r tha t th e size.distributio n o f lea dparticle s emitte d fro mautomobile s an dth e relativ e concentration s o f th e comple x compound s i n thos e particle s var y sig

nificantl y wit hdrivin g conditions , engin e condition , typ e o f fuel , an dag e o f

exhaus t system . Particle s > 2 fim in th e exhauste dparticulat e ar e primaril y lea d bromochloride . Th e ver y larg e particles , aconse quenc e o f

deposit s in th e exhaus t system , ar e als o primaril y lea dbromochloride . Th e fate s o f

thes e lea dcompounds , onc e the y ar e introduce dint o th e atmospher e fro mautomobiles , ar e no t completel y understood . Ther e i s disagree

men t in th e earl y literatur e concernin g th e los s o f halogen s b y thes e lea dcompounds . Pierrard 2 6 sug geste dtha t

PbBrC I undergoe s photochemica l decompositio n withth e formatio n o f alea doxid e an dth e releas e o f

fre e bromin e an dchlorine , bu t late r suggeste dahydrolyti c conversio n mechanism . Te r Haa r an dBayard 2 5 an dRobbin s an dSnitz 2 7 confir mth e los s o f

haloge n fro mfreshl y emitte dP b salts , bu t the y d o no t

suppor t th e photochemica l mechanism . Te r

Haa r an dBayard 2 5 sugges t tha t lea dhalide s ar e eventuall y converte dt o lea dcar bonate s an dlea doxides . Pierrard 26 obtaine ddat ao n age dlea daeroso l tha t

indicate dtha t

th e lea dparti

cl e surface s ha dalread y bee n converte dt o a relativel y insolubl e formsuc ha s oxide , carbonate , o r basi c halide ; thi s woul db e consisten t wit hacon versio n mechanis mexpecte dt o releas e th e les s reac tiv e hydroge n halid e rathe r tha n th e mor e reactiv e molecula r

halogen . Dzuba y an dStevens 2 8 observe d adiurna l variato n in th e bromine-to-lea dcon centratio n rati o in atmospheri c particulat e indica

tiv e o f th e los s o f

halogen s durin g atmospheri c transport . Te r

Haa r an dBayard 2 5 studie dth e effect s o f agin g o n automobil e exhaus t collecte di n ablac k bag , usin g an electro n probe . Th e results , show n i n Tabl e 6-6 , indicat e tha t 7 5 percen t

o f th e bromin e an d3 0 t o 4 0 percen t

o f th e chlorin e associate dwith th e compound s containe din th e particulate s wer e los t i n 1 8 hr ; dat apresente dsugges t tha t th e pro portion s o f

lea dcarbonate s an alea doxide s in

creased . Sinc e thes e chemica l reaction s occurre di n a blac k bag , photolyti c processe s woul dno t likel y b e responsibl e fo r th e decreas e in halides . A t th e ver y least , therefore , thi s experimen t demonstrate s th e existenc e o f

nonphotolyti c decompositio n pathway s fo r lea dhalide s in th e atmosphere . Consequently , th e chemica l compositio n o f lea din th e atmospher e fro mautomobil e emission s almos t certainl y depend s t o som e exten t

o n th e ag e o f

th e particle s a s wel l a s th e presenc e o f

othe r pollutant s wit hwhic hth e lea d compound s ca n react . Th e result s o f

Le e e t al. 9 sho w tha t

th e percentag e o f water-solubl e particulat e lea dincrease dwhe n dilute dexhaus t

wa s irradiate db y ligh t in th e wave lengt hregio n o f

300 0 t o 600 0 A . Thi s regio n i s i n th e near-ultraviole t

an dvisibl e region s o f

th e spectru m an di s availabl e fro mdirec t sunlight . Th e percentag e o f water-solubl e lea di n th e dilute dexhaus t als o wa s increase db y irradiatio n i n th e presenc e o f 0. 5 pp m S0 2 . Irradiatio n significantl y increase dth e sulfat e concentratio n o f

th e particulate s an dwa s accom panie db y ashif

t t o smalle r

particl e sizes . A shif

t o f nitrate-bearin g particle s t o smalle r sizes , wit han d withou t additio n o f

S0 2 , wa s als o observe dwithir

radiation . Th e amoun t o f nitrat e presen t

wa s decrease din th e presenc e o f S0 2 . Th e lea dnitrate , whic hi s muc hmor e solubl e in wate r tha n th e othe r lea dsalt s present , canno t b e totall y responsibl e fo r th e increase dwate r

solubilit y observe di

f th e N0 3 concentration s decrease . Th e informatio n availabl e regardin g th e chemica l compositio n o f

lea dparticle s emitte dfro mauto mobile s ma y b e summarize da s follows : 1 . Lea dhaloge n compound s ar e th e principa l form s emitted ; lea dchlorobromid e i s th e mos t prominen t

o f these . 2 . Th e particulate s underg o compositiona l change s durin g transpor t awa y fro mth e source . Thes e change s appea r t o consistentl y involve : a . Losse s o f

halogens , th e rat e o f

whic hmigh t b e photochemicall y enhanced , bu t whic h als o occu r

in th e absenc e o f

light . b . Genera l increase s i n th e wate r solubilitie s o f th e particle s wit hconcomitan t shift s towar dsmalle r

mea n particl e sizes . Thes e latte r change s ar e enhance db y th e pres enc e o f SO z , in whic hcas e th e amount s o f nitrat e presen t

decrease . 3 . Althoug hsevera l report s hav e suggeste dtha t th e lea dhaloge n compound s ar e converte d t o oxide s and/o r

carbonates , th e onl y specifi c examinatio n o f

th e compositio n afte r

agin g wa s tha t o f Te r Haa r an dBayard. 2 5 Unfor

tunately , thei r

experimenta l approac hdi d 6- 7P.7 2

no t rel y o n aparticularl y definitiv e metho d o f identification . Indeed , th e electro n micro

prob e approac huse dca n onl y b e regarde da s acrud e qualitativ e too l fo r th e identificatio n o f compounds ; th e simultaneou s occurrence s o f othe r element s in lead-bearin g particle s an dth e genera l morphologica l charac

teristic s o f

th e particle s ca n provid e onl y cir

cumstantia l indication s o f th e compound s tha t ar e present . Thi s i s particularl y tru e fo r lead-bearin g particle s becaus e compound s o f severa l othe r

element s ar e als o typicall y pre sent . Habib i e t

al., 5 fo r example , hav e show n tha t th e particle s ofte n includ e iro n a s wel l a s lea dcompounds . Th e percentag e composi

tio n dat agive n in Tabl e 6- 6 shoul dals o b e evaluated , takin g int o accoun t tha t the y ar e numbe r rathe r tha n mas s percentages . Thus , althoug hlea dcarbonate , fo r example , ma y compris e arelativel y hig hnumbe r percen tag e o f th e total , it s mas s percentag e ma y b e quit e different , dependin g o n th e siz e distri

bution s involve dan dwhethe r th e particl e composition s ar e siz e dependent . Thes e genera l conclusion s an dqualification s ar e consisten t

withan dsupportiv e o f th e result s o f

th e stud y reporte db y Olso n an dSkogerboe. 2 9 The y determine dtha t

th e principa l formo f

lea dfoun din lead-contaminate dsoil s fro mhighwa y median s a s wel l a s i n stree t

dust s wa s lea dsulfate . Althoug hthi s stud y include devaluatio n o f 1 8 soi l and/o r

dus t sample s collecte dfro mdifferen t U.S . locations , sig

nifican t amount s o f

th e lea dhaloge n compound s wer e foun din an y case . Th e conversio n o f lea d halide s t o othe r

compound s appear s t o hav e bee n quit e complet e fo r

thes e age dlea daeroso l deposits . 6.2.2. 2 STATIONAR Y SOURC EEMISSION S Measurement s ar e no t

availabl e t o confir mth e chemica l for mo f

lea demission s fro mstationar y sources . Barltro p an dMeek 3 0 indicat e th e presence , withou t referenc e t o specifi c measurements , o f lea d sulfid e o r

lea dchlorid e i n th e minin g industry , lea d oxid e i n smelters , an dlea dcarbonat e an dlea dchro

mat e in pigment s use di n olde r paints . Lea doxid e i s th e principa l formo f

th e meta l use din batter y manufacturing . Th e associatio n o f

lea dsulfid e wit hminin g i s clearl y rational , sinc e thi s i s th e primar y minera l for m(galena) . Whil e lea doxid e ma y certainl y b e derive dfro mth e smeltin g process , th e amount s pro duce dma y b e relativel y smal l in compariso n t o th e amount s o f

lea dsulfid e release da s fugitiv e dus t t o th e atmospher e aroun dasmelter . Moreover , th e releas e o f

S0 2 usuall y associate dwit hlea dsmeltin g operations , couple dwithth e possibl e interaction s betwee n lea dparticle s an dSO z , impl y tha t th e com pound s release dmay wel l underg o conversio n t o othe r forms . Thus , althoug hth e compound s generall y associate dwit hstationar y source s ar e no t particularl y soluble , th e possibilit y o f conversio n t o mor e solubl e compound s o r accumulatio n o f

th e particle s in th e lung s o f expose dpopulation s shoul d no t b e ignored . 6. 3 TRANSPOR T I N AI R Th e mechanism s o f

atmospheri c transport , removal , an dresuspensio n o f lea dparticulate s in

terac t in acomple x manner . Th e transpor t mechan

ism s ar e function s o f

th e particl e siz e distribution , particl e morphology , meteorology , an dloca l topography . 6.3. 1 Distributio n Mechanism s Th e transpor t

an ddiffusio n o f

gaseou s an dpartic

ulat e material s i n th e atmospher e ar e consequence s o f molecula r

diffusio n an dth e three-dimensiona l motio n field , th e latte r

bein g th e dominan t

factor . A detaile dtreatmen t

o f thes e phenomen awill b e foun d in man y standar dtextbook s o n meteorology . Th e three-dimensiona l motio n fiel dca n b e assume dt o b e compose do f

amea n win d(transport ) vecto r an da turbulen t component . Th e turbulen t componen t

i s analogou s t o molecula r

diffusion , bu t

th e coefficien t o f turbulen t

edd y diffusio n i s usuall y o f muc h greate r magnitude . Th e turbulen t componen t

tend s t o sprea dth e materia l verticall y an dlaterall y abou t th e mea n horizonta l transpor t vector . Therefore , assumin g apollutio n plum e fro maloca l lin e o r poin t source , th e atmospheri c motio n serve s t o dilut e an dtranspor t

th e pollutants . Sinc e lea demitte dt o th e atmospher e i s primaril y in th e inorgani c particulat e form , it s transpor t an d dispersio n will depen dprimaril y o n particl e siz e a s wel l a s chemica l stability , th e heigh t o f injection , an dth e intensit y an dstabilit y o f th e atmospheri c motio n field . Larg e particle s injecte da t lo w eleva

tion s wil l settl e t o th e surfac e i n th e immediat e vicinit y o f

th e source , wherea s th e smalle r particle s wil l b e transporte dove r greate r distances . A stud y b y Daine s e t

al. 3 1 relate datmospheri c lea dt o traffi c volum e an ddistanc e fro mahighway . The y foun dth e effec t

o f traffi c o n lea dconten t

o f th e ai r t o b e striking , bu t

limite dt o arathe r

narro w zon e borderin g primaril y th e le e sid e o f th e highway , a s show n in Figur e 6-7 . Abou t 6 5 percen t

o f th e lea din 6- 8th e ai r

betwee n 3 0 an d175 0 f t fro mth e highwa y consiste do f

particle s unde r

2 fim, an d8 5 percen t wer e unde r

4 fim i n diameter . Figur e 6- 8 show s a typica l relationshi p o f

particl e siz e t o distanc e fro m th e highway . Chola k

etal. 1 2 an dSchuc k

an dLocke 3 2 di dsimila r

studie s wit hsimila r

results . A s show n i n Figure s 6- 4 an d6-5 , Huntzicke r e t al. 1 0 demon

strate dtha t

th e larg e particl e mod e (D p > 7 fim) in th e freewa y distributio n i s severl y attenuate dat th e Pasaden asite . 0 I 1 1 I

-

-

- TRAFFI C VOLUME , vehicles/da y 1 0 - 58,00 0 \ 6 - 47.00 0 ft •- 44,00 0 \ O - 19,80 0 

# "^-o^ZjZlI ^ 1 1 1 1 

### 1

• -

-

-

—o 1 20 0 30 0 40 0 DISTANC E FRO M HIGHWAY , fee t Figur e 6-7 . Air-lea d value s a s a functio n o f traffi c volum e an d distanc e fro m th e highway. 3 1

% HAVIN G MEA N MAS S DIAMETE R LES S THA N Figur e 6-8 . Relationshi p o f th e diamete r o

f th e particle s (mass ) t o distanc e fro m th e highway. 3 1 Knowledg e o f

lea dconcentration s in th e ocean s an dglacier s provide s som e insigh t int o th e degree s o f atmospheri c mixin g an dlong-rang e transport . Tatsumato , Patterson , an dChow 333 5 measure ddis

solve dlea dconcentration s in se awate r of f th e coas t o f California , i n th e Centra l Nort hAtlanti c (nea r Bermuda) , an din th e Mediterranean . Th e profile s obtaine dar e show n in Figur e 6-9 . Surfac e con centration s i n th e Pacifi c wer e foun dt o b e highe r tha n thos e o f

th e Mediterranea n o r

th e Atlantic , an d decrease dabruptl y t o relativel y constan t level s wit h depth . Th e vertica l gradien t wa s foun dt o b e muc h les s i n th e Atlantic . Base do n th e Pacifi c data , Tatsumat o an dPatterson 3 3 estimate da n averag e surfac e lea dconcentratio n o f 0. 2 /ig/k g in th e north

er n hemispheri c oceans . Cho w an dPatterson 3 5 revise dthi s estimat e downwar dt o 0.0 7 figlkg. Ther e appear s t o b e n o differenc e betwee n lea dconcentra tion s in dee p wate r

in th e Atlanti c an dPacific . Thes e investigator s calculate dtha t industria l lea di s cur rentl y bein g adde dt o th e ocean s a t abou t 1 0 time s th e rat e o f

introductio n b y natura l weathering , with significan t

amount s bein g remove dfro mth e at mospher e b y precipitatio n an ddeposite ddirectl y int o th e ocean . Thei r

dat asugges t

considerabl e con taminatio n o f

surfac e water s nea r

shore , diminishin g towar dth e ope n ocean. 3 5 Thes e investigator s con clud e tha t

lea demission s fro mautomobile s ar e th e primar y sourc e o f

pollutio n o f

ocea n surfac e water . 0

100 0

20OO

300 0

400 0 -1 —< r

i f f i I t

6

i o — 1

1 ^ ^ ** <*?

1 

### 1 f

O - ATLANTI C (BERMUDA ) O - MEDITERRANEA N 40°39'N , 05°48' E d- PACIFI C 29°13'N , 117°37' W I -

—

LEA D I N SE A WATER , vg/k g Figur e 6-9 . Lea d concentratio n profile s i n th e oceans . " ^ Duce , Taylor , Zoller , an dthei r co-workers 36 ' 3 8 hav e investigate dtrace-meta l concentration s (in

cludin g lead ) in th e atmospher e in remot e norther n an dsouther n hemispheri c sites . Th e natura l source s fo r suc hatmospheri c trac e metal s includ e th e ocean s an dth e weatherin g o f

th e earth' s crust , wherea s th e manmad e sourc e i s particulat e pollution . Enrich

men t factor s fo r

concentration s relativ e t o standar d value s fo r

th e ocean s an dth e crus t wer e calculate d (Tabl e 6-7) ; th e mea n crusta l enrichmen t factor s fo r th e Nort hAtlanti c an dth e Sout hPol e ar e show n in Figure s 6-1 0 an d6-11 . Th e significanc e o f th e com 6- 9P.7 4

pariso n in Figur e 6-1 1 i s tha t 9 0 percen t

o f th e par ticulat e pollutant s in th e globa l tropospher e ar e in

jecte di n th e norther n hemisphere. 3 9 Sinc e th e resi

denc e time s fo r

particle s in th e troposphere 4 0 ar e muc hles s tha n th e interhemispheri c mixin g time , it i s unlikel y tha t

significan t

amount s o f

particulat e pollutant s ca n migrat e fro mth e Nort hAtlanti c t o Antarctic avi ath e troposphere ; howeve r thi s doe s no t rul e ou t

stratospheri c transfer . I n th e cas e o f lea d(an dal l othe r

metal s studie dexcep t

vanadium) , th e enrichmen t

factor s wer e ver y simila r at th e tw o locations . Thi s suggest s (bu t doe s no t prove ) tha t

th e atmospheri c concentration s o f thes e metal s ma y originat e primaril y fro mnatura l (rathe r tha n man made ) sources . TABL E 6-7 . CONCENTRATIO N RANG E AN D MEA N EF cru8 t VALUE S FO R ATMOSPHERI C TRAC E METAL S COLLECTE D

OVE R TH E ATLANTI C NORT H O F 30 ° N 3 6

Concentralio n range , ng'sc m t r crust . qeom . mean 3 A l S e F e C o M n C r V Z n C u C d P b S b S e 8-37 0 0.0008-0.01 1 3.4-22 0 0.006-0.0 9 0.05-5. 4 0.07-1. 1 0.06-1 4 0.3-2 7 0.12-1 0 0.003-0.6 2 0.10-6 4 0.05-0.6 4 0.09-0.4 0 1. 0 0. 8 1. 4 2. 4 2. 6 1 1 1 7 11 0 12 0 73 0 2,20 0 2,30 0 10,00 0 Calculate d o n th e basi s o f th e mea n crusta l abundance s o f Taylor. "

Figur e 6-10 . Midpoin t collectio n locatio n fo r atmospheri c sample s collecte d fro m R . V . Trfden f nort h o f 30°N , 197 0 throug h 1972. 36 ' 3 8 Murozum i e t

al. 4 1 hav e presente dsupportiv e evi

dence . Thei r

dat asho w tha t

long-rang e transpor t

o f lea daerosol s emitte dfro mautomobile s ha s signifi

cantl y pollute dth e pola r glaciers . The y collecte d •NORT H ATLANTI C WESTERLIE S D SOUT H POL E



### CogivTB " 

# M s« n

|Pb«- U - 

## rffB " J * JB L

Figur e 6-11 . Th e EF crug t value s fo r atmospheri c trac e metal s collecte d i n th e Nort h Atlanti c westerlie s an d a t th e Sout h Pole . Th e horizonta l bar s represen t th e geometri c mea n enrichmen t factors , an d th e vertica l bar s represen t th e geometri c standar d deviatio n o f th e mea n enrichmen t fac tors . Th e EF crus t fo r lea d a t th e Sout h Pol e i s base d o n th e lowes t lea d concentratio n (0. 2 mg/scm). 36 ' 3 8 sample s o f

sno w an dic e fro mGreenlan dan dth e Antarctic . A s show n in Figur e 6-12 , the y foun dtha t th e concentratio n o f

lea dvarie dinversel y withth e geologica l ag e o f

th e sample . Th e author s attribut e th e gradien t

increas e afte r

175 0 t o th e Industria l Revolutio n an dth e enhance dincreas e afte r 194 0 t o th e increase dus e o f

lea dalkyl s i n gasoline . Th e mos t recen t level s froun din th e antarcti c snow s were , however , les s tha n thos e foun din Greenlan d b y afacto r

o f 1 0 o r more . Befor e 1940 , th e con centration s in th e Antarcti c wer e belo w th e detect

abl e leve l ( < 0.00 1 /xg/kg ) an dhav e rise n t o 0. 2 Mg/k g in recen t

snow . A grap ho f

th e worl dlea d smelte r an dlea dalky l productio n presente db y Murozum i e t

al. 4 1 i s show n in Figur e 6-13 ; support in g dat aar e show n i n Tabl e 6-8 . Th e result s an dconclusion s o f Murozum i e t

al . wer e criticize db y Mills, 4 2 wh o suggeste dth e in

creas e in th e sno w lea dafte r 194 0 coul db e du e t o aircraf t operatin g fro mThul e Ai r Forc e Base . Bryce-Smith 4 3 countere dMills ' argumen t b y statin g tha t th e greates t

amoun t

o f lea dfoun dt o b e deposite din th e sno w wa s durin g winte r month s whe n ai r traffi c wa s lightest ; ther e wa s n o horizonta l gradien t betwee n th e ai r

bas e an dth e collectin g site ; th e collectin g sit e wa s predominantl y upwin dfro m th e ai r base ; and , finally , th e majo r increas e in lea d level s bega n abou t

2 0 year s befor e th e neares t operatin g bas e wa s established . Jaworowski 4 4 foun dtha t lea dconcentration s i n tw o glacier s hav e increase db y afacto r o f 1 0 durin g th e las t century . Th e concentration s i n th e mos t re 6-1 00.2 0 0.1 8 0.1 6 0.1 4 0.1 2 0.1 0 0.0 8 O.O E 0.0 4 0.0 2 n ' I T-TV " 1 1 1 1

J.iy , T l 1 1 1 , 1 1 1 1 |

o

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0

J . 1 1 1 1 '

o

1 1 . -rr

o

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## J - 1 - 0 / —

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- O - LEA D SMELTE D I N NORTHER N HEMISPHER E D - LEA D SMELTE D I N SOUTHER N HEMISPHER E & - LEA D BURNE D A S ALKYL S I N NORTHER N HEMISPHER E

80 0 h«-B,C , »| « 180 0 185 0 A . D . AG E O F SAMPLE S Figur e 6-12 . Lea d concentratio n profil e i n sno wstrat a o

f Norther n Greenland. 4 1 Figur e 6-13 . Worl d lea d smelte r an d alky l lea d productio n sinc e 175 0 A.D. 4 1 TABL E 6-8 . LEA D AEROSO L PRODUCTIO N I N TH E NORTHER N HEMISPHER E COMPARE D WIT H LEA D CONCENTRATION S I N CAM P CENTURY , GREENLAND , SNO W A TDIFFEREN TTIMES 4 1

Dat e 1753 181 5 193 3 196 6 Lea d

smelted . 10 3 tons/y r 1 2 1 6 3 1 Fractio n

converte d t o aerosols . % 2 2 1 6 0.0 6 Lea d

aerosol s produce d fro m smelteries. . 10 3 tons'y r 2 4 8 2 Lea d burne d

as alkyls . 10 3 lons/y r — — 0- 1 3 Fractio n

converte d t o aerosols . % — — 4 0 4 0 Lea d

aerosol s produce d fro m alkyls . 10 3 tons/y r

• — — 4 10 0 Tota l lea d

aerosol s produced . 10 3 tons/y r 2 4 12 a 102 a Lea d

concentratio n at Cam p Century . /ig/k g sno w 0.0 1 0.03 0.07 0. 2 a Value s corrected . cen t ic e layer s wer e extremel y hig h(14 8 fig/kg). Jaworowsk i e t

al. 4 5 als o studie dstabl e an dradio

activ e pollutant s fro mic e sample s fro mStorbree n glacier s in Norway . Th e mea n stabl e lea dconcentra tio n in Storbree n glacie r ic e in th e 12t

hcentur y wa s 2.1 3 figlkg. Th e mea n fo r mor e recen t

sample s wa s 9.8 8 /u.g/kg . Aroun d1870 , th e averag e lea dcon centratio n i n Norwegia n glacie r ic e wa s 5.8 6 figlkg, wherea s tha t

fo r glacier s in Polan dwa s 5. 0 figlkg. A centur y later , th e mea n concentratio n in th e Nor

wegia n glacie r

wa s 9.8 8 Mg/kg , wherea s th e mea n concentratio n i n th e Polis hglacie r reache d14 8 Mg/kg . Jaworowsk i e t

al. 4 5 attribute dth e larg e in

creas e o f lea dconcentration s in th e Polis hglacie r t o loca l sources . Jaworowsk i e t

al. 4 5 als o measure d2,0 P b in th e glacie r ice . Th e value s foun din th e Storbree n glacie r ic e ar e show n graphicall y i n Figur e 6-14 . Th e high

es t valu e wa s foun din 1961 . A simila r valu e wa s foun din Polis hglacier s an din th e Alp s th e sam e year. 4 4 Th e value s an dirregularitie s observe din ^ 10 P b concentration s i n th e investigation s sugges t tha t par t o f th e atmospheri c 2l0 P b ma y hav e origi

nate dfro martificia l source s —nuclea r explosion s in th e Arctic , o r

energ y productio n in fossil-fue l powe r stations . Base do n thei r findings , Jaworowsk i e t al. 4 5 conclude dtha t

long-rang e transpor t

o f lea d

YEAR . A S DETERMINE D B YDEPT H 196 6 6 5 6 4 6 3 6 2 6 1 6 0 5 9 5 8 5 7 5 6 5 S 5 4 4 0. 5 z 2 0. 4 H <-210CONCENToo

Q m 0. 1

- i l l I l I l I 1 I I I l I



# r 

# -I T —

-

_ _

. -

- I 1IIII I I I I I 1 2 3 4 , 5 6 7 8 9 1 0 1 1 DEPTH , meter

s Figur e 6-14 . 210 P b I n Storbreen , Norway , glacie r Ice , 1954-1966 , 4 5 6-1 1"*r*~ P.7 6

pollutant s i n th e atmospher e i s areality , bu t th e author s sugges t

tha t th e rat e o f

contaminatio n o f glacie r ic e correlate s bette r

withth e tota l annua l in

pu t o f coa l burnin g t o th e energ y syste mo f th e worl d tha n wit hlea demission s fro mautomobiles . 6.3. 2 Remova l Mechanism s Th e principa l mechanism s fo r remova l o f

in

organi c lea dparticulat e fro mth e atmospher e ar e dr y depositio n an dprecipitation . Detaile ddis

cussion s o f

thes e processe s will b e foun din standar d textbook s b y Sutton, 4 6 Pasquill, 4 7 Fletcher, 4 8 Junge, 4 9 Gree n an dLane, 5 0 an dSlade. 5 1 Th e remova l efficienc y o f

thes e processe s varie s signifi

cantly , dependin g o n physica l characteristic s o f th e suspende dmaterial , atmospheri c conditions , an dth e natur e o f th e receivin g surface . 6.3.2. 1 DR Y DEPOSITIO N Dr y depositio n remova l processe s includ e sedi

mentation , diffusion , an dinertia l mechanism s suc h a s impaction . Sedimentation , o r settlin g o f

particles , occur s whe n th e mas s o f th e particl e i s larg e enoug h t o overcom e th e buoyanc y forc e an dth e liftin g force s o f convectiv e currents . Freel y fallin g particle s o f th e siz e rang e foun di n suspende daerosol s rapidl y attai n thei r

terminal , o r

constant , velocit y whe n th e aerodynami c dra g o n th e particl e i s equa l t o th e weigh t o f th e particle . Th e termina l velocit y depend s o n th e particl e size , it s density , an dgravitationa l ac celeration . Whe n aparticl e i s o f asiz e comparabl e t o th e mea n fre e pat ho f

th e ga s molecules , bombard

men t b y th e molecule s result s i n arando mo r Brownia n motio n tha t

i s superimpose do n it s down

war dmotion . If

aparticl e i s ver y smal l an dit s mo tio n i s observe dfo r

onl y ashor t

perio do f

time , it s fal l ma y b e completel y maske db y th e Brownia n mo tion . Residenc e time s or , conversely , th e rat e o f fallou t o f aerosol s o r

dus t particle s containin g lea d in th e atmospher e ar e the n primaril y afunctio n o f particl e size . Th e shap e o f th e suspende dparticle s als o ha s asignifican t

effec t o n th e settlin g velocity . Usuall y th e settlin g velocit y o f particle s o f

variou s geometrica l form s i s calculate din term s o f th e set tlin g velocit y o f

spherica l particle s o f th e sam e volume . Th e aerodynami c particl e size , conven tionall y use dwhe n discussin g airborn e particulate , i s define da s th e siz e o f aspher e o f

uni t densit y tha t ha s identica l aerodynami c behavio r t o th e particl e in question . Particle s havin g th e sam e aerodynami c siz e may hav e differin g shape s an ddimensions . Airborn e particle s ar e generall y divide dint o thre e siz e ranges : Aitke n nucle i (particl e radiu s < 0. 1 fim), larg e nucle i (particl e radiu s 0. 1 t o 1 fim), an dgian t

nucle i (particl e radiu s > 1 fim). Ex

tremel y smal l particle s (radiu s < 0.00 1 fim) ten dt o coagulat e rapidl y t o formlarge r ( ~ 0.0 5 t o 0. 5 fim), les s mobil e particles. 5 0 Fletcher 4 8 derive da n approximat e equatio n t o predic t th e rat e at

whic h th e concentratio n number , n , o f particle s o f

radius , r , wil l decreas e in arelativel y unifor maerosol . Fo r r = 0.00 5 /A

man dn = 10 5 /cm 3 (typica l in urba n air) , th e tim e require dfo r particl e concentratio n t o decreas e b y one-hal f

wa s calculate dt o b e 3 0 min . Fo r r = 0.\fimandn= 10 3 /cm 3 , 5 0 percen t reduc

tio n wa s calculate dt o requir e 50 0 hr . Th e siz e dis

tribution s o f

larg e an dgian t

nucle i ar e no t

signifi

cantl y affecte db y coagulation . Settlin g o r

termina l velocitie s o f

spherical , parti

cles , a s reporte db y Gree n an dLane 5 0 an dIsrae l an d Israe l , 5 2 ar e show n i n Tabl e 6-9 . TABL E 6-9 . TERMINA L VELOCITIE S O F SPHERICA L PARTICLE S O F UNI TDENSITYA TGROUN D LEVE L Particl e radius . /u n 0.0 1 0.05 0. 1 0. 2 0. 5 1.0 2. 0 5. 0 10. 0 20. 0 50. 0 Termina l velocit y

Israe l an d Israe l 1.4 3 x10" 5 — 2.32 X10 - 4 — — 1.3 2 x10" 2 — — 1.23x10 ° — — cm/se c

Gree n on d Lan e 8.7 1 x 10" 5 2.2 7 X10 - 4 6.85 x 10" 4 3.49 x10" 3 1.2 9 x10" 2 5.0 0 x10' 2 3.03 x10" 1 1.20x10 ° 4.7 1 24. 7 Airborn e particle s ar e als o remove dfro mth e at mospher e b y inertia l mechanisms . I n turbulen t iner

tia l deposition , turbulen t win dfluctuation s per pendicula r

t o ahorizonta l surfac e impar t sufficien t inerti at o prope l th e particle s throug hth e boundar y laye r an dont o th e surface . Thi s mechanis mi s im

portan t fo r bot hsmoot han droug hsurfaces . Whe n th e roughnes s element s o n asurfac e protrud e suffi

cientl y fa

r int o th e windstream , inertia l impactio n ma y becom e important . Th e mea n horizonta l flo w o f th e wind , rathe r

tha n turbulen t

fluctuations , con trol s impaction . Thi s mechanis moccur s whe n parti

cle s canno t

follo w th e ai r

streamline s a s the y pas s aroun daroughnes s element . I n thi s case , th e mea n windflo w supplie s th e inerti atha t drive s th e parti

cle s ont o th e surface . Inertia l mechanism s ar e dependen t o n at mospheri c condition s an dth e characteristic s o f th e surface . Th e small-scal e surfac e structur e ma y b e especiall y significant . Fo r example , smal l particle s 6-1 2ar e preferentiall y retaine do n lea f surfaces , wher e the y ma y b e tightl y retaine db y smal l hair s o n th e leaf , b y surfac e pores , an db y tack y substance s ex crete db y th e leaves . Impactio n o f submicrometer

size dparticle s o n lea f

surface s i s possibl e at

norma l win dspeeds. 5 3 Pin e needle s an dsimilarl y shape d surface s appea r

t o b e aerodynamicall y attractiv e fo r impactio n o f

particulat e matter . Therefore , pin e tree s nea r

asurfac e sourc e o f

lea dparticulat e pollu

tio n ma y increas e th e rat e at whic hlea daerosol s ar e remove dfro mth e atmosphere . Heiche l an d Hankin 5 4 reporte dsoi l lea dconcentration s in fron t o f an dwithi n aroadsid e windbrea k o f pin e tree s a s bein g 5 0 percen t

an d10 0 percen t

higher , respec tively , tha n soi l lea dconcentration s a t correspond

in g distance s i n anearb y ope n fiel dtha t bordere d th e sam e sid e o f

th e road . Particl e remova l rate s fro mth e atmospher e ar e usuall y describe din term s o f depositio n velocity . Historically , depositio n velocitie s hav e bee n define d a s th e rati o o f

depositio n flu x t o th e airborn e con centratio n withunit s o f length/tim e usuall y reporte d a s cm/sec. 4 9 Sehme l an dHodgson 5 5 hav e publishe da mode l fo r

th e predictio n o f

dr y depositio n velocitie s base do n thi s concept . K|_ 

### c (6-1 ) wher e K i s th e depositio n velocity , N i s th e deposi

tio n flux , an dC i s th e airborn e concentratio n fo r monodisperse dparticle s measure d1 c mabov e th e depositio n surface . Th e depositio n velocity , K , assume s tha t

particl e depositio n i s describe db y a one-dimensional , steady-stat e continuit y equation . Th e basi c assumption s i n th e mode l ar e tha t th e flu x i s constan t

withheight , tha t

arelationshi p fo r

parti

cl e edd y diffusivit y ca n b e determined , tha t th e effec t o f gravit y ca n b e describe db y th e termina l set tlin g velocity , tha t

agglomeratio n doe s no t occur , an dtha t particle s ar e completel y retaine do n th e surface . Th e mode l wa s designe dt o predic t deposi

tio n velocitie s fo r

simpl e surfaces . Actua l remova l rate s ar e non-steady-stat e processe s dependen t o n th e deliver y capabilit y o f th e uppe r

atmospher e an d th e surfac e resistance . Base do n th e abov e assump tions , Sehme l an dHodgson 5 5 writ e th e equatio n fo r depositio n flu x as :

N = -( e + D ) —-v. C (6-2 )

d z wher e v t i s th e absolut e valu e o f th e termina l settlin g velocity , €

i s th e particl e edd y diffusivity , D i s th e Brownia n diffusivity , C i s th e airborn e concentra tion , an dz i s th e referenc e height . Fo r smal l parti

cles , th e sedimentatio n ter m(-v,C ) i s negligibl e s o

tha t depositio n velocit y i s afunctio n o f th e Brown

ian an dedd y diffusivit y ter monly . Fo r larg e parti

cles , th e diffusivit y ter mi s negligible , an dth e depositio n velocit y i s equa l t o th e termina l velocity . Incorporatin g th e concept s o f frictio n velocity : 

### u. = 

### -^—L —(6-3 ) Klm(z/z 0 ) wher e k i s vo n Karman' s constant , u i s th e windspeed , z i s height , an dz o i s th e roughnes s height . Roughnes s heigh t i s define da s ameasur e o f th e roughnes s o f

asurfac e ove r

whic hflui di s flow

ing : z o=H/3 0 (6 . 4 ) wher e H i s th e averag e heigh t o f surfac e ir

regularities . Sehme l an dHodgson 5 5 develope dpre dictio n depositio n velocit y curve s fo r arang e o f roughnes s height s an dfrictio n velocities . Represen

tativ e curve s ar e show n i n Figure s 6-1 5 throug h 6-17 . Depositio n velocitie s ar e show n t o b e afunc

tio n o f particl e diamete r

an dhav e thei r

smalles t value s in th e 0. 1 t o 1 fim particl e diamete r range . Th e mea n diamete r

o f lead-containin g particle s in th e atmosphere , remot e fro mmajo r sources , fall s ap proximatel y in thi s range . I n th e cas e o f large r parti

cles , bot hincrease deffectiv e edd y diffusio n in sur fac e boundar y laye r

(a s aresul t

o f greate r particl e inertia ) an dincrease dgravitationa l settlin g rate s ten dt o increas e th e predicte ddepositio n velocitie s abov e th e minimum . Th e lowe r limi t o f th e pre dicte ddepositio n velocitie s i s th e sedimentatio n velocity . Fo r

smalle r particles , depositio n velocitie s increas e withdecreasin g particl e diameter s becaus e o f increase dmas s transfe r b y Brownia n motion . Depositio n velocitie s fo r 0.01-M mparticle s ar e relativel y insensitiv e t o change s in particl e diamete r a t elevate dheight s abov e 1 0 cm . Depositio n velocitie s at

1 c mabov e th e groun dar e extremel y large ; consequently , i n th e 0.01-M mparticle

diamete r range , th e depositio n velocitie s ar e con trolle db y atmospheri c diffusio n in th e layer s im

mediatel y abov e th e canopy . A s indicate db y Sehme l an dHodgson, 5 5 th e mode l shoul dpredic t reasona bl y wel l th e depositio n velocitie s fo r simpl e surfaces , assumin g th e win ddirectio n i s persisten t ove r suffi

cien t distance . I t

shoul dnot , however , b e expecte d t o predic t

depositio n velocitie s fo r acit y becaus e o f th e complexit y in th e geometr y o f th e surfac e an d becaus e o f

loca l win dconditions . Value s o f

lea ddepositio n velocitie s foun din th e literatur e generall y rang e fro mabou t 0. 1 t o 0. 5 cm/sec. 5 6 Thes e value s ar e base do n tota l lea dflu x an dtota l airborn e concentrations , withou t regar dt o 6-1 3P.7 8

particl e size . Sinc e larg e particle s ma y contro l lea d depositio n in certai n cases , i t i s necessar y t o examin e th e entir e siz e distributio n o f particle s i n orde r

t o calculat e depositio n rates . Further , accurat e isokineti c measurement s o f larg e airborn e particle s ar e require dt o relat e airborn e concentration s t o deposition . Davidson 5 6 foun dadepositio n velocit y o f 0.2 9 cm/se c i n Pasadena , base do n tota l flu x an d tota l airborn e concentrations . Base do n th e fractio n o f lea dparticle s greate r

tha n 1 0 microns , however , th e depositio n velocit y wa s 1. 3 cm/sec . Huntzicke r e t al. 10 foun dadepositio n velocit y o f 1.8 0 cm/se c o n aTeflo n plat e place do n th e shoulde r o f aLo s Angele s freeway .

£ 1 0 E * >ELOCOSITIONV

E L o • • i yi T

1 cm \ - 1 0 c m 

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TYPICAL : / UPPER BOUND ; UNSTABLE , L - 1 0 meters /

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10' ' 1 1 0 PARTICL E DIAMETER , micrometer s Figur e 6-15 . Predicte d depositio n velocity o f particle s a t indi cate d heigh t fo r u . = 2 0 cm/se c an d Z Q = 3. 0 cm. 5 5

— I 1 I I Mil l I— I I I I I M | I I I I 11I I | I—Illl l .UNSTABLE , L =-1 0 meter s

.. f STABLE . L - 1 0 meter s -"••'*- „ S • -^ ^ **-

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c 

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V - * "• ^ 1 0 , ' I I I I 1 1 u l J i L

1 0 1 1 0 PARTICL E DIAMETER , micrometer s Figur e 6-16 . Predicte d depositio n velocitie s o f particle s a t 1- m heigh t fo r z 0 = 3. 0 cm , 5 5 Johnson 5 7 sample dparticle s wit han instrumente d aircraf t flyin g a t

30 0 maltitud e i n th e vicint y o f St . Louis , Missouri . Particle s wer e collecte db y expos in g asmal l (1.0

- b y 7.5-cm ) glas s slid e covere dwith athi n laye r

o f high-viscosit y silicon e oi l t o th e fre e ai r strea moutsid e th e ski n o f th e aircraft . Particle s wer e counte dan dsize dmanuall y fro mphotographs . Sample s wer e obtaine dupwin dan ddownwin do f St . I I I I Illl l 1— I I I I lll | ^UNSTABLE , L » -1 0 meter s „STABLE,L "

I I I Illl l 1 0 1 1 0 PARTICL E DIAMETER , micrometer s 1 0 Figur e 6-17 . Predicte d depositio n velocitie s o f particle s a t 1 m fo r u . = 20 0 cm/sec. 5 5 Loui s o n eac ho f

1 1 day s durin g th e perio dJul y l throug hJul y 18 , 1975 . Th e result s indicate dtypica l numbe r concentration s o f

airborn e particle s large r tha n 1 0 fim in diamete r o f 7,50 0 particles/m 3 up win dan d11,00 0 particles/m 3 downwind . Particle s large r tha n 3 0 fim in diamete r wer e foun din con centration s o f

20 0 particles/m 3 upwin dan d42 5 par ticles/m 3 downwin do f th e city . Fo r

th e downwin d particl e numbe r

densitie s o f

> 1 0 M man d>3 0 M

m particles , an dwit hth e assume ddensit y o f 2 g/m 3 , th e mas s concentration s woul db e abou t 0.0 1 ng/m 3 an d 0.01 2 ng/m 3 , respectively . Th e result s reporte dindi

cat e tha t particle s >3 0 fim ca n b e transporte dt o altitude s o f

30 0 mb y convectiv e currents ; therefore , al l larg e particle s ar e no t remove db y sedimentatio n in th e immediat e vicinit y o f sources . Assumin g a sedimentatio n velocit y o f 0. 3 cm/se c fo r

a1 0 fimdiamete r particl e an da n initia l heigh t o f 30 0 m , th e particl e coul dremai n airborn e fo r approximatel y 2 7 h r an db e transporte dabou t 20 0 k mwithaunifor m win do f 2 m/sec . Thi s typ e o f

lon g distanc e transpor t ha s bee n observe db y Gillett e an dWinchester 1 5 ove r Lak e Michigan . Th e actua l concentration s observe d ar e ver y small , however , an dwoul dcontribut e littl e t o ambien t

ai r loadin g o r

dustfal l accumulatio n in region s remot e fro mth e source . Lynam 5 8 studie dth e atmospheri c diffusio n o f car bo n monoxid e an dlea dfro ma n expresswa y (1-75 , nort ho f Cincinnati , Ohio) . Th e significan t result s ar e show n i n Figure s 6-1 8 throug h6-20 . Approx

imatel y 5 0 percen t

o f th e lea demitte dfro mth e auto mobil e traffi c wa s remove dfro mth e atmospher e b y 6-1 4dr y depositio n withi n 64 0 f t o f th e edg e o f

th e road

way (Figur e 6-18) . Th e siz e distributio n o f th e lea d particle s wa s no t

significantl y altere dbetwee n 2 0 an d64 0 f

t (~ 6 an d—19 5 meters) . Win dspeed s range dfro mapproximatel y 0. 5 t o 3. 8 m/sec . Assum

in g amea n win dspee do f 2 m/sec , th e 50-percen t reductio n withi n 64 0 f

t woul dcorrespon dt o abou t 1. 5 mi n o f

trave l time . Th e concentratio n o f lea d decrease dfro mabou t

7 Mg/m 3 at

2 0 f t t o abou t 1. 5 Mg/m 3 a t 64 0 ft , adecreas e b y afacto r o f abou t 5 . Th e dat awer e no t

sufficien t

t o determin e th e rela

tiv e efficienc y o f

sedimentatio n versu s impactio n in th e tota l remova l process ; however , Figure s 6-1 9 an d6-2 0 indicat e tha t

th e remova l mechanis mwa s no t strictl y limite dt o sedimentation . Daine s e t al., 3 1 in thei r stud y o f th e relationshi p o f

atmospheri c lea d t o traffi c volum e an ddistanc e fro mahighway , foun da50-percen t

reductio n in lea dbetwee n 1 0 an d 15 0 f t o f th e edg e o f

th e roadway . 1— I Illl l % LEA D REMOVE D =

_R = 0.6 8 

### i

—r i i 1 1

i IIII I 4 0 6 0 8 0 10 0 15 0 20 0 40 0 60 0

TRAVE L DISTANCE , fee t Figur e 6-18 . Regressio n o f percentag e lea d particulate s remove d b

y dry depositio n wit h distanc e fro m roadway. 6 8 (Legend:— = regressio n line;— = 95 % confidenc e limit s fo r regressio n line ; = 95 % confidenc e limit s fo r singl e value ; R = correlatio n coefficient. ) Smith 5 9 investigate dlea dcontaminatio n o f whit e pin e growin g alon g a n east-wes t sectio n o f

Interstat e 9 5 in Connecticut . H e foun dtha t lea dcontamina

tio n decrease dregularl y withincreasin g distanc e fro mth e roa dan dwa s greates t o n th e side s o f

th e tree s neares t

th e highway . Base do n th e muc hhighe r concentratio n o f

lea ddeposite do n th e needle s neares t th e roadway , Smit hconclude dtha t pin e tree s ma y serv e a s rathe r

efficien t ai r filters . 6.3.2. 2 PRECIPITATIO N Precipitation , o r

we t deposition , remova l pro cesse s includ e rainou t

an dwashout . Rainou t

occur s 8 b 4

2

1. 0 0. 8 0. 6 0. 4

0. 2 -

-

-

.

- 1 1 —0 —

--•- -

1 1 1 Illl l

SAMPLIN G STATIO N 2 0 f t FRO M EDG E O F EXPRESSWA Y SAMPLIN G STATIO N 64 0 f t FRO M EDG E O F EXPRESSWA Y

1 Illl l l 1 / A 1 1 ifa 1 a 

### aJ 1

1 1 D O | |

1 .

-

-

-

-

-

. .

-

—

-

-

-

1 1 0 2 0 5 0 7 0 9 0 9 5 9 8 9 9 P b PARTICULATE S <STATE D SIZE , percen t Figur e 6-19 . Compariso n o f siz e distributio n o

f lea d particu late s collecte d at 2 0 an d 64 0 f t fro m a n expresswa y nort h o f Cincinnati . Ohio . Determine d b y seven-stag e Anderse n sampler. 5 8

- | 1—|— i i i i | | 1—i—|— r P b CONC . = 12.114766 7 - 3.899313 5 XLO G DISTANC E

R " -0.7 8

C O CONC . - 6.5198 9 - 1.713846 7 XLO G DISTANC E

R = -0.6 0

_L _ i _ _ i _ _i _ JL 5 0 10 0 20 0 DISTANC E FRO M EDG E O F HIGHWAY , fee t Figur e 6-20 . Atmospheri c concentratio n o f lea d an d carbo n monoxid e a s a functio n o f lo g o f distanc e fro m edg e of high wa y ( R = correlatio n coefficient). 5 8 whe n particulat e matte r i s presen t

in th e super saturate denvironmen t

o f agrowing ' cloud . Th e smal l particle s (0. 1 t o 0. 2 fim) ac t a s nucle i fo r

th e formatio n o f

smal l droplets , whic hgro w int o raindrops. 4 9 Droplet s als o collec t particle s unde r 0. 1 M mb y Brownia n motio n an db y th e water-vapo r gradient . Th e nucleatio n proces s ma y als o occu r o n particulat e matte r

presen t belo w clou dlevel , pro ducin g droplet s larg e enoug ht o b e affecte db y sedi

mentation . Thes e processe s ar e referre dt o a s rainout . A secon dproces s (washout ) occur s whe n fallin g raindrop s collec t particle s b y diffusio n an d impactio n o n th e wa y t o th e ground . Rainou t an d 6-1 5•Il l P I I ••••• • P.8 0

washou t togethe r

ar e know n a s we t

deposition . Althoug hdat ao n th e lea dconten t o f precipitatio n ar e rathe r

limited , thos e tha t

d o exis t indicat e ahig h variability . Lazru s e t

al. 6 0 sample dprecipitatio n at 3 2 U.S . station s an dfoun dacorrelatio n betwee n gasolin e us e an dlea dconcentratio n in * rainfal l i n eac harea . Similarly , ther e i s probabl y acorrelatio n betwee n lea dconcentratio n in rainfal l aji ddistanc e fro mlarg e stationar y poin t source s o f

lea demission s i n th e vicinit y o f

suc hsources . Th e author s pointe d ou t tha t at leas t twic e a s muc hlea di s foun din pre cipitatio n a s in wate r

supplies , inferrin g th e exis

tenc e o f aproces s b y whic hlea di s deplete dafte r precipitatio n reache s th e ground . Russia n studies 6 1 poin t t o th e insolubilit y o f

lea dcompound s in sur fac e water s an dacknowledg e thi s remova l b y natura l sedimentatio n an dfiltration . Th e intensit y o f

rainfal l appear s t o b e negativel y correlate dwithth e amoun t o f lea dwashe dou t

o f th e atmosphere . Te r

Haa r e t al. 6 2 foun dtfoa

t shower s ha dlowe r

concentration s tha n slow , eve n rainfall . Dat apresente db y Jaworowski 4 4 sho w tba t in recen t years , th e lea dconten t

in rainwate r

range dfro m0 t o 185 8 Mg/l'ter . A laborator y stud y in whic hsimulate drainfal l wa s use dt o determin e th e efficienc y withwhic h automotiv e lea dparticulate s coul db e washe dou t indicate dtha t

th e efficienc y wa s les s tha n 1 per cent. 6 3 Concentration s o f 210 P b in rainwate r

hav e als o bee n reporte db y Jaworowski 4 4 a s highl y variabl e (a s muc ha s tw o order s o f magnitud e i

mth e sam e locality ) an dno t

relate dt o seaso n o r

amioun t o f pre cipitation . Value s range dfro m0. 2 t o 30 0 pCi/liter. 4 4 Hig hconcentration s wer e foundin sam ple s collecte dfro mnorther n continenta l localities , an dlo w concentration s wer e foun din sample s fro m oceani c an dAntarcti c locations . Jaworowsk i sug gest s tha t th e difference s migh t

b e attribute din par t t o artificia l contaminatio n b y nuclea r esxplosions . 6.3.2. 3 FIEL D STUDIE S Atkin s an dKruger 6 4 conducte dafiel dsamplin g progra mi n Pal o Alto , California , t o determin e th e effectivenes s o f

sedimentation , impaction , rainout , an dwashou t

in removin g lea dcontaminant s fro m th e atmosphere . Rainfal l in th e are aaverage s approximatel y 3 3 c m(1 3 in)/yea r an doccur s pri

maril y durin g th e lat e fal l an dwinte r months . Air

born e concentration s at afreeway sit e varie dfro m 0. 3 Mg/m 3 t o amaximu mo f 1 9 Mg/m 3 iff

l t*h e fal l an d winte r seasons , an dwer e amaximu mof'9. 3 Mg/m 3 in th e spring . Durin g period s o f ligh t rawfal l in th e spring , th e maximu mconcentratio n observe dwa s

7. 4 Mg/m 3

- A typica l dail y concentratio n profil e ob

serve di s show n in Figur e 6-21 . Mor e tha n 9 0 per cen t o f th e lea dpollutant s reachin g th e surfac e dur

in g th e 1-yea

r samplin g perio dwer e collecte din dr y fallout . Dr y depositio n a s afunctio n o f distanc e fro mth e freewa y i s show n in Figur e 6-22. * Approx

imatel y 1 percen t

o f th e tota l dr y fallou t

collecte d nea r th e expresswa y wa s lead . We t depositio n (ap

proximatel y 3 3 c mo r

1 3 in o f

rai n pe r

year ) ac counte dfo r

5 t o 1 0 percen t

o f th e lea dremova l at th e samplin g sites . A summar y o f th e fiel ddat ai s show n in Tabl e 6-10 .

E • 5 1 5

MID - 2 NIGH T 4 6 8 1 0 NOO N 2 TIM E O F DA Y 4 6 8 1 0 MID NIGH T Figur e 6-21 . Atmospheri c lea d concentratio n at freewa y sit e i n Pal o Alto , California , o n August 15,1966. 6 3 ? 1. 0 N e n E 1 v ]

I I I II I I I

—^ V l=STD . DEV . 1 N . X.9.0x10V B06 L

N . (SE E FOOTNOT E I N TEXT I



### -

-

-

- 1 • 1 1 1 I t I I 1



### -

-

-

-

- ' x - I N 10 0 20 0 50 0 100 0 200 0 500010,00 0 50.00 0 100,00 0 DISTANC E FRO M FREEWA Y{X), foo t Figur e 6-22 . Averag e lea d i n dry fallou t a s a functio n o f dis tanc e fro m th e freeway. 6 3 'Figur e 6-2 2 i s a semi-lo g plo t o f th e thre e averag e lea d value s a s a functio n n f dis tanc e fro m th e freeway . Th e dat a appea rt o fal l alon g a straigh t line , suggestin g tha t th e relationshi p hetwee n lea d i n fal l out . I. , an d distanc e fro m th e freeway . X . ca n h e describe d b yX = ae h l

- wher e a an d b ar e constants . Fro m th e semi-plot , th e ap propriat e value s fo ra an d b ar e a = 9. 0 xI0 4 ; b o -8.06 . i f L i s expresse d i n mgm 2 -wt can d X i s expresse d i n feet . Therefor e X = 9. 0 xIO 4 e**- 0ft k Th e are a unde rthi s curve , fro m X , = 5 0 f t t o X 3 = 26,90 0 ft , shoul d represen t th e tota l amoun t o f lea d deposite d i n th e Pal o Alt o are a fo reac h l-f i sectio n o f freeway . Thi s valu e i s 7.8 5 g/ft . Th e are a unde rth e curv e fro m L = 0.9 5 mg/ft^-w k t o L • 0 shoul d represen t th e tota l amoun t o f lea d tha t wa s remove d h ysedimentation , assumin g tha t th e dat a ca n b e extrapolate d pas t 26,90 0 ft . Thi s valu e i s I I. I g/ft . Thi s indicate d tha t a n averag e o f 7 0 percen t o f th e lea d tha t wa s remove d h ysedi mentatio n wa s remove d withi n 5 mile s o f th e source . 6-1 6P.8 1

TABL E 6-10 . SUMMAR YO F FIEL D DAT A FRO M PAL O ALTO , CALIFORNIA '

6 4 Freeway 3 {Bayshore ) Resi dentia l Foot hill s Lea d i n dr yfallout : Average , mg/fr-w k Amoun t removed , mg/f t -y r Lea d i n rainfall : Average , mg/lite r Amoun t removed , mg/f t -y r Averag e ai rconcentration , Mg/m 3 Pb/tota l solid s i n ai r Pb/nonvolatil e solid s i n dryfallou t 0.9 2 49. 4 0.18 1 3.2 5 7.3 0 0.042 0.2 4

11. 7 0.14 9 3.6 6 2.2 8 0.01 8 0.15 3

8. 3 0.03 5 0.9 2 1.9 0 0.01 6 0.011 2 0.010 2 0.004 9 Andre n e t

al. 6 5 evaluate dth e contributio n o f we t an ddr y depositio n o f

lea di n astud y o f

th e Walke r Branc hWatershed , Oa k Ridge , Tennessee , durin g th e perio dJun e 197 3 t o Jul y 1974 . Th e mea n pre cipitatio n in th e are ai s approximatel y 13 0 cm/yea r (5 1 in/year) . Th e majo r atmospheri c emission s in th e vicinit y o f

Oa k Ridg e ar e derive dprimaril y fro m thre e coal-fire dstea mplants . A foundr y an dferro

allo y plan t

approximatel y 64. 5 k m(4 0 miles ) t o th e wes t wer e assume dt o hav e amino r impac t becaus e o f

orographi c barriers . Result s reporte dfo r th e perio dJanuar y throug hJun e o f 197 4 ar e pre sente di n Tabl e 6-11 . Rainfall , o r we t deposition , contribute dapproximatel y 6 7 percen t o f th e tota l depositio n fo r

th e period . TABL E 6-11 . DEPOSITIO N O F LEA D A TTH E WALKE R BRANC H WATERSHED , 1974 6 5 Lea d depositio n (g/ha ) Dr y Januar y February Marc h Apri l Ma y Jun e Tota l Averag e 34. 1 6. 7 21. 6 15. 4 26. 5 11. 1 115. 4 19. 2 < 16. 7 3. 3 10. 6 7. 5 13. 0 5. 4 56. 5 9. 4

a Tota l depositio n — 17 2 g/ha . We t depositio n —67 percen t o l total . yuntzicke r

e t al. 1 0 estimate dth e flo w o f automo bile-emitte dlea di n th e Lo s Angele s Basi n base do n measurement s o f

particl e size , atmospheri c con centrations , an dsurfac e depositio n o f lea da t variou s site s aroun dth e Basin . A flow diagra mbase do n th e stud y an dmodifie db y Schuc k an dMorgan 6 6 i s show n i n Figur e 6-23 . O f th e lea demitte dfro mau tomobil e exhaus t

i n th e Basi n (estimate dt o b e abou t 1 8 ton s pe r

day) , th e investigator s calculate dtha t abou t 5 6 percen t

wa s deposite dnea r

th e sourc e (nea r deposition) , 1 2 percen t wa s deposite din th e Basi n bu t i n area s remove dfro mth e sourc e (far deposi

tion) , an dabou t

3 2 percen t

wa s transporte dou t

o f th e Basi n b y th e wind . Th e value s presente dfo r depositio n an dwin dremova l wer e fo r dr y weathe r onl y (i.e. , dr y depositio n only) .

INPU T 23. 7 metri c ton s Pb/da y

25 % 

# t REMOVE D B YSTREE T CLEANIN G 6 % SEWAG E 40 % J NEA R DEPOSITIO N STREE T 8 % LAN D

32 % RUNOF F 2 % V

0.6 4 metri c ton s Pb/da y I 10 % FA R DEPOSITIO N LAN D 

# T ^ COASTA L WATER S Figur e 6-23 . Fat e of lea d contribute d fro m automotive traffi c i n Lo s Angele s Basin. 0 3 Robert s e t

al. 6 7 foun dan exponentia l decreas e in dustfal l wit hdistanc e aroun dtw o secondar y smelter s (Figur e 6-24) . Th e author s conclude dtha t th e hig hrat e o f

fallou t aroun dth e smelter s origi

nate dfro mepisoda l large-particulat e emission s fro mlow-leve l fugitiv e source s rathe r tha n fro mth e stack . Thi s bein g th e case , sedimentatio n woul db e th e principa l remova l process . Th e lea din dustfal l value s decrease dwel l ove r 9 0 percen t

withi n adis

tanc e o f 300m .

100 0

50 0 I I 1 SMELTE R A :

\ SMELTE R B : 1 1 1 Y= 6,10 0 -2.56 0 lo g X R = -0.8 1 p < 0.00 1 9 6 SAMPLE S A T 1 6 SITE S — Y= 89 6 - 34 0 lo g X R - -0.6 3 p <0.00 1 3 4 SAMPLE S A T6 SITE S

-

U 20 0 30 0 40 0 50 0 DISTANC E FRO M STACK , meter s Rgur e 6-24 . Contaminatio n o f dus t b y lea d emission s fro m tw o secondary smelters . Soli d an d dashe d line s ar e fitte d curve s correspondin g t o th e regressio n equations ; dotte d line s ar e a n extrapolate d fit ; U indicate s correspondin g value s foun d I n urba n contro l areas. 6 6 6-1 7P.8 2

Studie s suc ha s thos e describe dabov e clearl y indi

cat e tha t lea di s effectivel y remove dfro mth e at mospher e b y dr y an dwe t depositio n processes , an d tha t atmospheri c concentration s ar e significantl y in

fluence db y thes e remova l mechanism s eve n in th e immediat e vicinit y o f th e source . Th e rat e o f remova l i s highl y dependent , however , o n th e siz e distributio n o f

th e particles , th e natur e an dcharac

teristic s o f

th e depositio n surfaces , airborn e con centrations , an datmospheri c condition s includin g stability , winds , an dprecipitation . I n dr y weather , th e lea dwil l b e deposite do n surface s i n th e formo f dustfal l b y sedimentation , diffusion , o r inertia l mechanism , dependin g primaril y o n th e siz e o f th e particles . Mas s depositio n nea r th e source s will b e controlle dprimaril y b y sedimentatio n o f larg e parti

cles , wherea s th e smalle r particle s will remai n air

born e longer , b e transporte dfurthe r b y th e wind , an db e remove dprimaril y b y diffusio n an dinertia l mechanisms . Th e characteristic s o f

th e surface s o n whic hth e lea di s deposite dwil l significantl y influenc e th e depositio n an dretention . Depositio n will b e greate r i n awoode dare atha n o n pave dsurface s o r shor t grass . Building s als o will influenc e th e dr y deposi

tion , althoug hther e ar e few dat aavailabl e t o quan tif y th e effect . I n area s withhighe r annua l rainfall , remova l b y precipitatio n (we t deposition ) become s mor e importan t

an dma y b e th e dominan t process . Al l o f thes e factor s substantiall y influenc e poten tia l huma n lead-exposur e pattern s —bot hinhala

tio n o f airborn e lea dan dpossibl e ingestio n o f dus t containin g lead . Th e dr y depositio n remova l mechanism s deplet e th e airborn e concentration s bu t deposi t th e materia l i n th e formo f dust . Th e factor s controllin g dr y depositio n the n becom e extremel y importan t

fro mth e standpoin t

o f potentia l exposur e pattern s fo r

dust , sinc e the y ma y strongl y influenc e tempora l an dspatia l variations . Becaus e o f sedi

mentatio n o f

larg e particles , dustfal l rate s (mass ) will b e highes t

immediatel y adjacen t

t o roadway s wit hdens e automobil e traffi c an dnea r stationar y source s o f

al l type s wher e lea dma y b e emitted . Thes e rate s wil l diminis ht o arathe r lo w valu e in area s remot e fro msource s an dwher e th e smal l par ticle s ar e remove dprimaril y b y diffusio n an diner

tia l mechanisms . Th e accumulatio n o n th e depositio n surface s wil l depen do n th e rat e o f depositio n an dth e rat e a t whic hth e materia l i s cleane dfro mth e surface s b y precipitatio n o r

b y mechanica l mean s suc ha s stree t sweepin g o r

vacuuming . Dus t

enterin g building s o r home s b y ai r

transpor t

wil l usuall y b e deposite do n fla t surface s suc ha s floor s o r furniture . Th e sam e physica l processe s wil l contro l th e rat e o f deposi

tion . Th e potentia l exposur e level , particularl y fo r youn g children , will depen do n th e accumulation , whic hagai n will b e influence db y th e depositio n rat e an dth e frequenc y an dmethod s o f cleaning . I n oc cupationa l environment s wher e fugitiv e dus t emis

sion s ar e high , accumulatio n wil l b e rapi dif surface s ar e no t frequentl y cleaned . Significan t amount s o f thi s dus t ma y b e carrie do n clothin g int o th e home s o f worker s an dcontribut e furthe r t o th e tota l lead

dus t loadin g in th e hom e environment . Emissio n rate s fro mautomobil e traffi c an dfro m stationar y source s ar e highl y variabl e in time , eve n o n a n hourl y basis . Sinc e th e residenc e tim e o f larg e particle s in th e atmospher e i s o n th e sam e orde r o r less , th e dustfal l rate s in th e immediat e vicinit y o f source s shoul dals o b e highl y variable . Thi s i s reflecte di n airborn e concentration s measure dver y nea r th e source . A s aconsequenc e o f

th e numbe r

o f variable s in

volve dan do f

th e tempora l an dspatia l variation s occurring , it

i s no t possibl e t o quantif

y huma n ex posur e in uncontrolle dcase s withou t th e us e o f

per sona l monitors . Estimate s o f suc hexposur e ma y var y b y an orde r

o f magnitud e o r

greater . Fo r

agive n emissio n pattern , on e ca n generall y conclud e tha t potentia l exposur e fro mlea din dus t shoul db e greates t (1 ) i n dr y seasons , (2 ) i n area s wit hspars e vegetation , (3 ) withi n afe w hundre dmeter s o f

th e sources , (4 ) unde r

condition s o f

stabl e atmospheres , (5 ) durin g th e mornin g an dafternoo n traffi c rus h hour s in th e vicinit y o f

freeways , an d(6 ) durin g pea k productio n period s o f

stationar y source s (usuall y durin g th e day) . 6.3.2. 4 RESUSPENSIO N Th e threshol dstress , whic hmus t b e exceede d befor e aparticl e i s resuspende dfro masurface , i s a functio n o f

th e particl e properties , particl e size , an d th e surfac e properties . A particl e o f agive n siz e an d densit y will resuspen dmor e easil y fro masmoot h surfac e tha n fro man irregula r surfac e suc ha s an asphal t road . Particle s o n adir t roa do r othe r soi l surface s ma y becom e attache dt o soi l particle s an d behav e quit e differentl y fro ma n iner t fre e particle . Thi s proces s o f

weatherin g tend s t o reduc e resuspen sion . Moisture , influence db y atmospheri c variable s suc ha s wind , precipitation , humidity , an dsola r radiation , ma y inhibi t

resuspension . Dat ain th e literatur e o n resuspensio n sho w tha t thi s proces s i s no t

wel l understood , an dhenc e resus pensio n rate s canno t

yet b e predicte dt o an y degre e 6-1 8o f

accuracy . Fo r

example , Mishima 6 8 indicate s tha t reporte dresuspensio n factors * var y ove r 1 0 order s o f magnitud e fro m10" 2 t o 10"" . (Th e resuspensio n factor , in m 1 , equal s th e airborn e concentration , in ng/m 3 , divide db y th e groun dsourc e concentration , i n ng/m 2

. ) I t

i s useful , however , t o examin e dat a fro mmor e controlle dresuspensio n experiment s in orde r t o obtai n aqualitativ e ide ao f expecte dlea d resuspensio n rates . Sehmel 6 9 ha s examine dth e resuspensio n o f Zn S particle s smalle r

tha n 2 5 micron s fro ma n asphal t roa dsurface . H e foun dtha t whe n aca r

wa s drive n acros s th e recentl y applie dtracer , 0.00 1 percen t t o 1. 0 percen t

o f th e materia l wa s resuspended . However , th e fractio n resuspende ddecrease db y 2 t o 3 order s o f

magnitud e whe n a30-da y perio delapse d betwee n applicatio n o f th e trace r

an dth e ca r passage . Th e fractio n resuspende dpe r vehicl e passag e in

crease da s afunctio n o f vehicl e spee dan dwa s inde

penden t o f win dvelocitie s fo r

th e tes t conditions . Th e fractio n resuspende dpe r vehicl e passag e wa s greate r fo r adriv e throug hth e trace r tes t lan e tha n o n th e adjacen t

lan e an dgreate r

fo r a3/4-to n truc k tha n fo r acar . Thes e result s sugges t tha t resus pensio n o f

lea dfro mroadway s ma y pla y asignifi

can t rol e in th e overal l transpor t o f lea dawa y fro m automotiv e sources . Thi s ma y b e importan t con siderin g th e conclusion s o f Huntzicke r

e t al. 1 0 tha t

a considerabl e fractio n o f th e emitte dlea ddeposit s directl y o n th e roadways . I n anothe r

experiment , Sehme l an dLloyd 7 0 ex amine dth e resuspensio n o f \0-fim monodispers e uranin e particle s fro masmoot hsurfac e in th e laboratory . The y foun dtha t th e fractio n o f

materia l resuspende dpe r

secon dvarie dfro mIO" 6 t o 10" 3 fo r win dspeed s o f

16. 5 t o 18. 3 m/sec . The y als o measure dth e resuspensio n o f CaMo 4 ove r

sand y soil. 7 0 Th e fractio n o f

materia l resuspende dpe r sec on drange dfro m2 x 10 l 0 t o 2. 2 x 10 8 fo r wind s o f 1. 3 t o 2 0 m/sec . A limite damoun t

o f dat ao n lea dresuspensio n i s als o available . Figur e 6-2 5 show s th e depositio n o f lea dfoun da s afunctio n o f heigh t abov e aroo f

sur face. 7 2 Th e lea dwa s deposite do n flat Teflo n plate s mounte da t

variou s heights . Th e greate r deposition s clos e t o th e roo f

ar e believe db y th e investigator s t o b e du e t o resuspende droo f dust . Th e environmenta l consequenc e o f sal t particl e resuspensio n fro mroad s ha s bee n reporte db y Smith. 7 3 Needle s fro mwhit e pin e plante dadjacen t t o a n interstat e highwa y i n Connecticu t showe dex cessiv e sodiu man dcalciu mconten t resultin g fro m airborn e sal t resuspensio n fro mth e highway . Th e depositio n o f

airborn e sal t

appear s t o b e simila r

t o tha t o f lea dfro mautomobil e exhaust. 6 9

35 0

30 0

25 0

20 0

15 0

10 0

5 0 

### 1 1

-

-

-

-



### 1 1 !

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_

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### 1 °^ U 2 0 P b DEPOSITION , ng/cm'-da y Figur e 6-25 . Tota l depositio n o f lea d o n Teflo n plate s a t variou s height s abov e th e roo f of Kec k

Laboratories , Califor ni a Institut e o

f Technology , Pasadena. 7 1 Bau me t al. 7 4 sample dairborn e particulat e fo r a perio do f abou t 2 year s at

severa l location s i n Port

land , Oregon , usin g paraffin-coate dMyla r film s withfour

- an dfive-stag e Lundgre n impactors . Soi l an ddus t samples , bot hsurfac e an dsubsurface , wer e als o take n at

th e air-samplin g sites . Sample s wer e analyze dfo r

lea dan dothe r

elements . Chemica l ele

menta l balanc e method s wer e use dt o calculat e soi l an ddus t burden s in th e air . Th e author s repor t tha t greate r tha n 9 0 percen t

o f th e submicrometer-size d airborn e particle s wer e associate dwit hautomotiv e emissions . Th e large r

particle s wer e reporte dt o b e contribute dabou t

equall y b y resuspende dstree t dus t an ddirec t

emission s fro mautomobiles . Thes e dat asugges t

tha t lea dresuspensio n ma y pla y a n importan t

rol e in th e transpor t

o f lead . A t present , however , i t

i s no t possibl e t o reac hquantita

tiv e conclusion s abou t

thi s mechanism . Siz e distri

butio n measurement s o f ambien t lea dpresente dher e an delsewher e in th e literatur e represen t airborn e dat atha t hav e bee n influence db y th e combine dfac

tor s o f atmospheri c transport , deposition , an d resuspension . 6.3. 3 Model s Ther e i s an extensiv e bod y o f literatur e o n at 6-1 9P.8 4

mospheri c transpor t

an ddiffusio n models. 75 ' 7 9 A detaile ddiscussio n i s beyon dth e scop e o f thi s docu

ment . Th e mathematica l model s ar e usuall y base d o n th e basi c Gaussia n plum e mode l emanatin g fro m th e earl y wor k

o f Sutton 4 6 an dPasquill 4 7 an dwel l describe db y Gifford. 7 6 Stern 7 7 provide da n ex cellen t revie w o f

ai r qualit y modelin g technique s fo r bot hrura l an durba n modelin g situations . Experi

menta l dat adescribin g th e pollutan t concentration s fro mpoin t

source s sho w that , i n spit e o f wid e varia

tions , thes e plume s exhibi t astron g tendenc y towar d aGaussia n o r

norma l distributio n a s astatistica l average . I n simpl e terms , parameter s reflectin g th e turbulen t componen t

defin e th e horizonta l an dver tica l dimension s o f

apollutan t

clou din avertica l plan e perpendicula r

t o th e mea n win dvelocity . Cermac k e t al. 8 0 hav e use dth e win dtunne l t o mode l physicall y th e atmospheri c boundar y laye r ove r urba n area s t o determin e th e pollutan t transpor t characteristics . 6. 4 TRANSFORMATIO N AN D TRANSPOR T I N OTHE RENVIRONMENTA L MEDI A 6.4. 1 Soil s Numerou s studie s hav e show n significan t con taminatio n o f

soil s b y th e emissio n o f lea dfro m mobil e an dstationar y source s an dthroug hth e dis

posa l o f wast e products . Excellen t review s o f

th e earl y literature , a s wel l a s report s o n mor e recen t research , hav e bee n publishe db y member s o f ajoin t researc hstaf

f fro mColorad o Stat e Universit y an d th e Universitie s o f

Missour i an dIllinois. 202 9 Man y o f th e studie s o f

lea dbefor e 197 3 wer e limite dt o analysi s fo r

elementa l lea dan ddi dno t includ e analysi s fo r

associate dions . Suc hinformatio n i s no t sufficien t t o permi t

athoroug hexaminatio n an d understandin g o f

(1 ) transformatio n an dtranspor t processe s tha t

occu r amon g th e environmenta l media , (2 ) mobilit y o f

lea din soils , (3 ) uptak e an d distributio n o f

lea di n plants , an d(4 ) th e overal l im

pac t o f lea do n huma n healt han decosystems . Infor

matio n o n th e chemica l form s o f lea di s needed . Soi l i s acomple x matri x compose do f severa l hundre ddifferen t

compounds , onl y asmal l fractio n o f whic har e lead . Mos t

analytica l technique s ar e no t capabl e o f

providin g positiv e identificatio n o f specifi c compound s unles s separatio n method s ar e use dtha t d o no t alte r th e lea dcompounds . Recently , nondestructiv e separation/preconcentratio n tech

nique s hav e bee n develope dan duse db y th e Col

orad o Stat e Universit y researc hgrou p t o determin e lea dcompound s i n soi l an dplants. 1 0 Lea dcontaminant s ar e deposite do n soi l b y dr y an dwe t depositio n processes . Presen t understandin g o f th e chemica l reaction s involvin g thes e particle s onc e the y ar e deposite dint o o r o n th e soi l i s in

complete. 8 1 Earl y wor k indicate s tha t

lea dprobabl y react s wit hsoi l anions , e.g. , S0 4 = , P0 4 = , o r C0 3 = , o r withsom e organi c o r

cla y complex. 8 2 Thes e reac tion s woul dten dt o mak e th e P b insoluble , thu s in

hibitin g rapi dmobilit y i n th e soi l o r plan t a s wel l a s microbia l uptake . Direc t evidenc e supportin g thes e reaction s i s limited . I n astud y b y Lagerwerf f an d Brower, 8 3 lea dwa s precipitate din N a+ -treated , alkalize dsoils . Th e solubilit y o f th e precipitat e in

crease dwit hdecreasin g p H an dconcentratio n o f NaCl . Furthermore , absorptio n o f soi l lea db y hy

drou s oxide s o f

iro n an dmanganese , an dit s conse quen t immobilization , ha s bee n reporte db y Gadd e an dLaitinen. 8 4 Studie s hav e identifie dcatio n exchang e capacity , organi c matte r

content , pH , soi l type , an dsoi l drain

ag e a s th e importan t

factor s influencin g th e mobilit y o f lea di n soils. 8 5 Santillan-Medran o an dJurinak 8 6 conducte dbatc hequilibriu mstudie s t o obtai n solubilit y dat afo r

lea dan dcadmiu mi n soil . Lea d solubilit y decrease din th e soil s a s p H increased . Th e lowes t value s wer e obtaine din calcareou s soil . I n noncalcareou s soil , th e solubilit y o f lea dappear s t o b e regulate db y Pb(OH) 2 , Pb 3 (P0) 4 ) 2 , Pb 4 0(P0 4 ) 2 , Pb 5 (P0 4 ) 3 0H , an deve n PbC0 3 , dependin g o n th e pH . Th e creatio n o f

organi c chelatin g agent s b y biologi c activit y serve s a s on e o f th e mos t

effectiv e processe s o f

meta l mobilizatio n o r

immobilizatio n in th e soil . Thes e agent s ar e eithe r plan t products , microbia l metabolities , o r humi c compound s (humi c acids) . Th e latte r

ar e capabl e o f

precipitatin g lead . Th e amount s an dtype s o f organi c matte r

pre sen t appea r t o provid e a n importan t contro l mechanis mfo r

th e movemen t

o f heavy-meta l ion s in soi l systems . Th e associatio n o f lea dan dorgani c matter , however , i s no t alway s empiricall y consis

tent. 8 7 Olso n an dSkogerboe 2 9 preconcentrate dlea d compound s in roadsid e soi l sample s an duse dX-ra y powde r diffractio n technique s fo r compoun diden

tification . Th e lea dcompound s in eac hsoi l fractio n examine dar e show n i n Tabl e 6-12 . Th e mos t abun

dan t lea dsal t

foun dwa s th e relativel y insolubl e PbSo 4 . Th e author s not e tha t generall y 7 0 percen t

o r mor e o f th e tota l lea din th e soil s examine dwa s con taine di n th e dens e fraction s an dtha t th e majorit y (>5 0 percent ) o f

thi s lea dwa s presen t

a s sulfate . Th e result s indicat e tha t oxide s presen t

in th e soi l 6-2 0wer e mino r constituent s compare dt o th e sulfat e concentrations . Sinc e lea dbromochlorid e com pound s ar e th e principa l constituent s o f fres hauto mobil e exhaus t

emissions , conversio n t o lea dsulfat e mus t hav e occurre deithe r

in th e atmospher e o r

in th e soil . Th e author s sugges t tha t sulfuri c aci d forme dfro mS0 2 in th e atmospher e o r at th e soi l interfac e ma y reac t

withth e lea dparticulat e t o form lea dsulfate . Reactio n withth e sulfat e io n als o ma y occu r i n th e soi l in contac t

withgroundwater. 2 4 Th e result s o f Le e e t al. 9 (Sectio n 6.2.2.1 ) suppor t thes e genera l contentions . Dat aar e limite dregardin g th e chemica l composi

tio n o f lea din soi l contaminate db y emission s fro m stationar y sources . Lea dsulfid e an dlea dchlorid e ar e though t

t o b e th e majo r

constituent s in soil s in th e vicinit y o f

minin g industries , an dlea doxid e i s th e chie f on e in th e vicinit y o f

smelters . Th e presenc e o f lea dsulfid e a s th e primar y compoun di n soil s alon g amine-acces s roa din Missour i ha s bee n re ported , (Tabl e 6-12) . Analytica l dat aconfirmin g th e othe r compound s mentione dabov e ar e no t availa

ble . 6.4. 2 Wate r 6.4.2. 1 INORGANI C Th e chemistr y o f

lea din an aqueou s solutio n i s highl y comple x becaus e th e elemen t ca n b e foun din amultiplicit y o f

forms . He man dDuru mhav e reivewe dth e chemistr y o f lea di n wate r

in detail, 8 8 an dth e aspect s o f

aqueou s lea dchemistr y tha t ar e german e t o thi s documen t ar e discusse di n Chapte r 3 . Natura l concentration s o f lea di n lead-or e deposit s d o no t

normall y mov e appreciabl y in groun do r

surfac e water . An y lea ddissolve dfro m primar y lea dsulfid e or e tend s t o combin e wit hcar bonat e o r

sulfat e ion s t o (1 ) forminsolubl e lea dcar bonat e o r

lea dsulfate , o r

(2 ) b e absorbe db y ferri c hydroxide. 8 7 A n outstandin g characteristi c o f lea di s it s tendenc y t o formcompound s o f lo w solubilit y wit hth e majo r

anion s o f

natura l water . Th e hydrox

ide , carbonate , sulfide , an dmor e rarel y th e sulfat e ma y ac t a s solubilit y controls . Th e amoun t o f lea d tha t ca n remai n in solutio n i n wate r i s afunctio n o f th e p H o f

th e wate r

an dth e dissolve dsal t content . Equilibriu mcalculation s sho w tha t th e tota l solubilit y o f

lea din har dwate r

(p H >5.4 ) i s abou t 3 0 fig/\iter

an dabou t

50 0 ^tg/lite r

in sof t wate r (p H <5.4). 8 9 Lea dsulfat e (PbS0 4 ) i s presen t in sof t wate r an dlimit s th e lea dconcentratio n in solution . Abov e p H 5.4 , PbC0 3 an dPb 2 (OH) 2 C0 3 limi t th e TABL E 6-12 . LEA D COMPOUND S IDENTIFIE D I N ROADSID E

SOIL S B YX-RAYPOWDE R DIFFRACTIO N TECHNIQUES 2 9 Locatio n an d soi l fractio n Fort Collins : Magneti c Nonmagneti c

Denver : Magneti c Nonmagneti c Chicago : Magneti c Nonmagneti c Chicago : Magneti c Nonmagneti c Missouri : Magneti c Nonmagneti c Compound s foun d PbS0 4 PbS0 4 PbOPbS0 4 Pb0 2 PbO ° PbS0 4 PbS0 4 PbS0 4 Pb O PbS0 4 PbS0 4 PbS0 4 None c Pb S PbS0 4 Estimate d concentrations 8 Majo r Majo r Mino r Trac e Trac e Majo r Majo r Majo r Majo r Mino r Majo r Majo r Majo r Mino r

a Majo rindicate s th e principa l portio n o f lea d presen t i n th e soi l fractio n indicate d and . therefore , th e principa l portio n o f th e soi l sample . Mino rrefer s l o approx imatel y1 t o 1 0 percen t o l th e lea d i n th e respectiv e fractions . Trac e quantitie s ar e les s tha n approximatel y1 percen t o f th e tota l i n eac h fraction . D Assignmen t i s base d o n th e presenc e o f onl yth e mos t intens e d-spacin g an d i s therefor e questionable . c Comple xd-spacin g patter n obtaine d wit h al l intensitie s low ; positiv e assign men t o f an yon e compoun d o rgrou p o f compound s i s questionable . concentration . Th e carbonat e concentratio n i s i n tur n dependen t

o n th e partia l pressur e o f C0 2 a s wel l a s th e pH . Calculation s b y He man dDurum 8 8 sho w tha t

man y rive r

water s i n th e Unite dState s hav e lea dconcentration s nea r th e solubilit y limit s impose db y thei r

p H level s an dcontent s o f dissolve d C 0 2 species . Becaus e th e influenc e o f changin g tem peratur e an dp H ma y b e substantial , observe dlea d concentration s ma y var y significantl y fro m theoreticall y calculate dones . Lazru s e t

al. 6 0 calculate dtha t

a s muc ha s 13 8 g/ha-m o o f

lea dma y b e deposite db y rainfal l in «om e part s o f th e northeaster n Unite dStates . Assumin g a n averag e annua l rainfal l runof f o f 5 0 c m(—2 0 in) , th e averag e concentratio n o f lea din th e runof

f woul dhav e t o b e abou t 33 0 /ug/lite r

t o remov e th e lea da t th e rat e o f

13 8 g/ha-mo . Concentration s a s hig ha s 33 0 /txg/liter

coul db e stabl e in wate r withp H nea r 6. 5 an da n alkalinit y o f abou t 2 5 n g bicar

bonat e ion/lite r

o f water . Wate r

havin g thes e proper tie s i s commo n i n runof f area s o f

Ne w Yor k

Stat e an dNe w England ; hence , th e potentia l fo r hig hlea d concentration s exist s there . I n othe r areas , th e averag e p H an dalkalinit y ar e s o hig htha t les s tha n 1 /ug/lite r o f lea dcoul db e retaine din solution s a t equilibrium. 8 7 6-2 1P.8 6

A significan t

fractio n o f

th e lea dcarrie db y rive r wate r ma y b e in a n undissolve dstate . Thi s nonsolut e lea dca n consis t

o f colloida l particle s i n suspensio n o r large r undissolve dparticle s o f lea dcarbonate , oxide , hydroxide , o r

othe r lea dcompound s incor

porate din othe r

component s o f

particulat e lea d fro mrunoff, eithe r

a s sorbe dion s o r

surfac e coating s o n sedimen t

minera l particle s o r

carrie da s apar t

o f suspende dlivin g o r

nonlivin g organi c matter. 8 7 A laborator y stud y b y Hem 9 0 o f sorptio n o f

lea db y ca tio n exchang e indicate dtha t amajo r par t o f th e lea d in strea mwate r

ma y b e adsorbe do n suspende dsedi

ment . Figur e 6-2 6 illustrate s th e distributio n o f lea d output s betwee n filtrat e an dsolid s in strea mwate r fro mbot hurba n an drura l compartments , a s re porte db y Rolf

e an dJennett. 9 1 Th e majorit y o f lea d outpu t i s associate dwithsuspende dsolid s in bot h urba n an drura l compartment s withver y littl e dis

solve din th e filtrate . Th e rati o o f lea din suspende d solid s t o lea din filtrat e varie s fro m4: 1 i n th e rura l compartmen t

t o 27:1 i n th e urba n compartment .

100

s o

0 _

- SHWl l SUSPENDE D SOLID S ^-^ j FILTRAT E

,,,II, I ,ii ' 

# f ^ -

/V/ ^ ^ Figur e 6-26 . Lea d distributio n betwee n filtrat e an d suspende d solid s I n strea m wate r fro m urba n an d rura l compartments." 0 Th e concentratio n o f

lea dusuall y reporte drepre sent s asomewha t

arbitraril y define dsolut e fraction , separate dfro mth e nonsolut e fractio n b y filtration . Mos t filtratio n technique s canno t b e relie do n t o remov e al l colloidal-size dparticles . Upo n acidifica

tio n o f th e filtere dsample , whic hi s usuall y don e t o preserv e i t

befor e analysis , th e colloida l materia l tha t passe s throug hi s dissolve dan dreporte din tha t form . Usuall y th e solid s remove dfro masurfac e wate r sampl e b y filtratio n ar e no t analyze dfo r

lead . Bu t eve n th e lea di n rainfal l ca n b e mainl y particu

late , an dthu s i t

wil l b e necessar y t o obtai n mor e in

formatio n o n th e amount s o f lea dtransporte di n nonsolut e form 8 7 befor e avali destimat e ca n b e ob

taine do f th e effectivenes s o f

runof f i n transportin g lea dawa y fro marea s wher e it ha s bee n deposite db y atmospheri c fallou t

an drain . 6.4.2. 2 ORGANI C Th e organi c component s o f soil-wate r

syste mar e a n extremel y divers e grou p o f compound s tha t

in

clude s carbohydrates , amin o acids , phenoli c an d quinoni c compounds , organi c acids , nuclei c acids , enzymes , porphyrins , an dhumi c materials. 8 7 I n ad

ditio n t o th e natura l organi c compound s presen t i n soils , stream s an dlake s contai n organi c sediment s an dsuspende dsolid s tha t hav e bee n derive dfro m municipal , agricultural , an dindustria l wastes . Thes e waste s includ e carbohydrates , proteins , nuclei c acids , enzymes , lipids , an dman y othe r organi c com pound s foun di n livin g systems . I n addition , oils , plasticizers , polymers , an dman y othe r organi c com pound s ar e discharge dt o natura l waterway s b y man ufacturin g an dchemica l industries . Th e interactio n o f lea dwit hthes e organi c compound s i s stil l no t wel l understood , bu t

mos t o f thes e organi c material s ca n confidentl y b e expecte dt o for mcomplexe s withlea d (an dothe r

metals) , sinc e the y al l contai n availabl e dono r site s fo r complexation . A discussio n o f meta l complexatio n i s presente din Chapte r 3 an dAppen

di x B . Th e presenc e o f

fulvi c aci d( aconstituen t o f soi l humi c materials ) in wate r ha s bee n show n t o increas e th e rat e o f

solutio n o f

lea dsulfid e 1 0 t o 6 0 time s ove r tha t o f awate r solutio n a t

th e sam e p H tha t

di d no t contai n fulvi c acid. 879 2 A t p H value s nea r

7 , solubl e lead-fulvi c aci dcomplexe s wer e presen t i n solution . A t

initia l p H value s betwee n 7. 4 an dabou t 9 , th e lead-fulvi c complexe s partiall y decomposed , an dlea dhydroxid e an dcarbonat e wer e precipi

tated . A t initia l p H value s o f

abou t 10 , th e lead

fulvi c aci dcomplexe s agai n increased . Thi s increas e wa s attribute dt o dissociatio n o f phenoli c group s at hig hp H values , whic hincrease s th e complexin g capacit y o f

th e fulvi c acid . Bu t

i t ma y als o hav e bee n du e t o th e formatio n o f solubl e lead-hydroxy l com plexes . I n summary , th e complexin g o f lea db y mos t

o f th e commo n sulfur- , phosphorus- , oxygen- , an d nitrogen-containin g ligand s mean s tha t lea dwil l ac cumulat e i n livin g an dnonlivin g organi c compo nent s o f soil-wate r

an dsediment-wate r

systems . Th e livin g an dnonlivin g organi c component s ar e no t in

dependent , o f

eac hother , bu t

the y ar e constantl y interactin g a s th e livin g component s metaboliz e th e nonlivin g component s o f th e syste man dthe n die , contributin g thei r

remain s t o th e poo l o f nonlivin g compound s in th e system . Th e fat e o f heav y metal s in thi s proces s ha s no t

bee n elucidated ; bu t

th e sedi

men t in acontaminate dsurface-wate r bod y wil l serv e a s alarg e reservoi r tha t ca n provid e lea dan d othe r metal s t o th e biot ao f th e syste meve n afte r 6-2 2heavy-meta l pollutant s hav e cease dt o b e in

troduced . Mos t

attentio n ha s bee n give n t o th e heav y metal s dissolve di n th e wate r phas e o f surfac e wate r rathe r tha n t o th e complexe dmetal s in th e sedimen t phase , thoug hsediment s probabl y contai n ahighe r amoun t o f lead. 8 7 Th e biotransformatio n o f lea dt o volatil e tetra methy l lea dconstitute s on e mechanis mb y whic h lea dma y leav e sediment-wate r systems . Th e direct , biologica l methylatio n o f certai n inorgani c lea d compound s b y lak e sedimen t microorganism s ha s bee n reported. 93

- 9 4 Al l th e lak e sediment s teste d wer e abl e t o transfor mtrimethy l lea dt o tetramethy l lead, 9 3 bu t

onl y som e o f

th e sediment s wer e abl e t o transfor mlea dnitrat e an dlea dchlorid e int o tetramethy l lead . N o biotransformatio n occurre d whe n th e lak e sediment s wer e incubate dwithlea d oxide , lea dhydroxide , lea dbromide , lea dcyanide , o r lea dpalmitate. 9 3 Certai n pur e bacteria l isolate s (se e Chapte r

8) fro mthes e lak e sediment s wer e show n t o transfor mtrimethy l lea dt o tetramethy l lea din th e anaerobi c incubatio n syste mused. 9 3 Th e conversio n o f

th e tri

- t o th e tetramethy l lea d sal t wa s subsequentl y postulate dt o b e chemica l rathe r tha n biological , proceedin g vi aformatio n an d the n decompositio n o f a n organi c sulfid e inter

mediate , (Me 3 Pb) 2 S. 9 5 Usin g asyste mcontainin g n o sulfides , however , othe r worker s showe dth e produc

tio n b y microorganism s o f Me 4 P b fro mMe 3 P b + muc hi n exces s o f

yield s expecte dfro mth e stoichiometr y o f

redistributio n reaction s o f lea d alky l compound s in aqueou s solutions. 9 4 Thus , th e alkylatio n appear s t o b e direc t an dbiological . Th e alkylatio n o f

lead , unlik e tha t

o f mercury , wa s no t mediate db y methylcobalamin , a s show n whe n equimola r

amount s o f

Me 3 PbOAc , Me 3 PbCI , Me 2 PbCl 2 , an dPb(N0 3 ) 2 wer e substitute dfo r in

organi c mercur y i n a n aqueou s tes t syste m(~p H 7). 9 5 Taylo r

an dHanna, 9 6 however , hav e recentl y demonstrate dtha t

prolonge dincubatio n o f methylcobalami n withafin e suspensio n o f lea dox id e (Pb 3 0 4 ) in a n aqueou s mediu mresult s in partia l demethylatio n o f

th e corrinoid . Thi s chemica l demethylatio n o f

MeB 1 2 b y Pb 3 0 4 wa s show n t o b e highl y p H dependent , wit hn o demethylatio n occur rin g at p H 7 , an d6 1 percen t occurrin g at

p H 2 . Trace r studie s wit h[ 14 C]-methyl-labele d methylcobalami n indicate dtha t demethylatio n o f MeB 1 2 b y Pb(IV ) wa s accompanie db y apro portiona l volatilizatio n o f th e label . Thes e result s ar e i n agreemen t

wit hth e know n instabilit y o f monoalky l lea dcompound s i n aqueou s medi aa s de

scribe db y Wood. 9 7 Th e alkylatio n o f lead , then , unlik e tha t

o f merc ury , doe s no t

appea r t o resul t

in nonvolatile , toxi c organolea dtha t

coul dunderg o biomagnificatio n i n th e foo dchain . Volatil e TM Lgenerate din situ woul db e expecte dt o escap e fro mabod y o f water . Th e possibl e uptak e o f tetramethy l lea db y aquati c organism s durin g it s passag e t o th e surfac e o f abod y o f wate r i s unknown . 6.4. 3 Plant s Lea di s transferre dfro mth e atmospher e t o th e soi l an dvegetativ e compartment s o f th e environ

men t b y dr y an dwe t

deposition . Considerabl e atten tio n ha s bee n devote dt o determinin g th e amoun t an dlocalizatio n o f

lea din roadsid e an dsmelte r areas , bu t

littl e informatio n i s availabl e regardin g it s chemistr y an deffect s in thos e areas . Mott o e l al. 9 8 suggeste dtha t

plan t uptak e i s probabl y relate dbet

te r t o solubl e rathe r

tha n tota l lea di n soils . Wilso n an dCline 9 9 conclude dtha t onl y 0.00 3 t o 0.00 5 per cen t o f tota l lea di

n soi l i s availabl e fo r

plan t uptake . Th e soi l solutio n i s affecte dby al l th e reaction s tha t occu r a s th e constituent s ar e change dthroug haddi

tio n t o o r

depletio n fro mth e soil . Ultimately , th e compositio n o f

th e soi l solutio n i s controlle db y th e solubilit y o f

th e variou s minera l phase s in th e soil . Th e long-ter meffect s o f lea din soil s ar e uncertain . Onl y recentl y ha s attentio n bee n give n t o th e solubilit y relationship s o f PbS0 4 , Pb 3 (P0 4 ) 2 , an d PbC0 3 a s possibl e controllin g mechanism s fo r th e amoun t o f lea din soils. 4 4 If

PbC0 3 i s involve da s a reactio n product , ther e i s th e possibilit y tha t soil s o f hig hpH , upo n becomin g acidic , coul dreleas e lea d at som e futur e time. 10 0 Th e questio n o f chemica l identit y o f

lea din plant s i s stil l largel y unanswered . Ham p an dZiegler 10 1 hav e suggeste dtha t lea dasso ciate dwithplan t

surface s in natur e ma y b e largel y lea dphosphate . Zimdahl, 10 2 citin g studie s con ducte da t Colorad o Stat e Universit y an dth e Univer

sity o f Illinois , reporte dth e identificatio n o f lea d pyrophosphat e in bea n root s an dlea dorthophos

phat e in soybea n root . Th e result s o f late r solubilit y studie s o f

th e tw o compound s suggeste dtha t lea d pyrophosphat e shoul db e th e dominan t for mi n plants . Th e proces s b y whic hlea di s take n u p b y plants , whic hma y b e passive, 8510 3 i s favore dunde r condi

tion s o f lo w soi l pH. 10 4 MacLea n e t al. 10 5 hav e sug geste dtha t

soi l managemen t

practice s suc ha s th e ad

ditio n o f organi c matter , lime , an dphosphat e ma y b e appropriat e i n contaminate dsoil s t o reduc e th e availabilit y o f

lea dfo r plan t uptake . The y foun dtha t th e concentratio n i n oat s an dalfalf avarie dinversel y 6-2 3P.8 8

withp H an dorgani c matter , an dtha t additio n o f phosphat e reduce dth e uptak e o f lead ; the y sug geste dtha t

th e p H effec t

wa s du e t o repressio n o f lea dsolubilit y a t

th e highe r

p H values . Joh n an d Va n Laerhoven 10 6 foun dlittl e differenc e i n uptak e b y oat s an dlettuc e whe n lea dwa s derive dfro m water-insolubl e lea dcarbonat e a s oppose dt o th e mor e water-solubl e lea dchlorid e o r nitrate . Henc e th e formatio n o f

lea dcarbonat e a s aresul t o f limin g woul dno t

explai n th e p H effect . Wor k a t th e Universit y o f

Illinoi s an dat

Colorad o Stat e University , cite db y Zimdahl, 10 2 ha s show n tha t uptak e b y severa l plan t specie s i s inversel y pro portiona l t o soi l lea dconten t an di s greates t

unde r condition s o f

lo w p H an dlo w phosphorus . Th e bind

in g o r exchang e capacit y o f

soils , relate dt o organi c content , i s extremel y importan t a s adeterminan t

o f lea davailabilit y t o plants . Chelatin g agent s ca n modif y th e uptak e an dpossibl y th e movemen t o f heav y metal s b y plants , bu t th e relativ e importanc e o f natura l chelatin g substance s i s har dt o evaluat e a t thi s time. 10 2 Zimdahl, 10 2 citin g anumbe r o f studie s regardin g chelatio n o f lea dwithEDTA , conclude s tha t th e exten t

o f lea dmovemen t

withi n th e plan t

i s stil l unresolved . H e question s whethe r studie s with syntheti c an dhighl y ionize dchelatin g agent s suc ha s EDT A actuall y reflec t

wha t i s happenin g in nature . I n astud y conducte da t th e Universit y o f

Il

linois 10 7 (cite db y Zimdahl 102 ) , it wa s show n tha t

th e root s o f hydroponicall y grow n cor n acquire dasur fac e lea dprecipitat e an dslowl y accumulate d crystallin e lea di n th e cel l walls . Th e surfac e precipi

tat e forme dquickl y an dindependentl y o f plan t ac tivity . Tw o compound s wer e postulate dbu t no t identified . Th e lea denterin g th e roo t wa s concen trate di n som e bu t

no t al l dictyosom e vesicles . After precipitatio n ha doccurre di n th e dictyosom e vesi

cle , cell-wal l precursor s wer e adde dt o th e vesicl e b y appositio n o f

vesicle s o r

b y interna l secretion . A s th e lead-containin g crystal s grew , mor e cell-wal l materia l wa s added , s o tha t th e entir e vesicl e even tuall y move dt o th e peripher y o f th e cel l t o achiev e fusio n wit hth e cel l wall . Lea ddeposit s wer e thereb y concentrate da t

th e cel l wal l an dno t withi n mitochondri ao r

othe r organelles. 10 2 Althoug hthi s sequenc e o f

event s wa s observe di n th e roo t tips , deposit s wer e observe dthroughou t th e plant , an di t wa s suggeste dtha t

asimila r

proces s occurre di n al l plan t tissues. 10 2 Th e depositio n o f

lea do n th e lea f

surface s o f plant s wher e th e particle s ar e ofte n retaine dfo r lon g tim e period s mus t

als o b e considered. 3210810 9 Sev

era l studie s hav e show n tha t plant s nea r

roadway s exhibi t

considerabl y highe r

level s o f

lea dtha n thos e farthe r away . I n mos t

instances , th e highe r con centration s wer e du e t o lea dparticl e depositio n o n plan t surfaces. 3 2 Studie s hav e show n tha t particle s deposite do n plan t

surface s ar e ofte n ver y difficul t t o remov e completel y b y simpl e washin g technique s considere dcharacteristi c o f th e treatmen t

tha t woul db e use din ahousehol dkitchen.IOS. I 10,11 1 Leave s wit hhair y surface s see mabl e t o retai n (an d attract ) particle s vi aa n electrostati c mechanism . Othe r type s o f

leave s ar e covere dwit hacuticula r wax sufficientl y stick y t o preclud e th e remova l o f particles . Thu s rainfal l doe s no t serv e a s aparticu

larl y effectiv e mean s o f removin g th e deposite dpar ticles. 11 0 Animal s o r

human s consumin g th e leaf y portion s o f

suc hplant s ca n certainl y b e expose dt o highe r tha n norma l level s o f lead . Fortunately , a majo r fractio n o f

lea demitte db y automobile s i s deposite dinsid e atypica l highwa y right-of-way , s o at leas t par t o f thi s proble mi s alleviated . Th e particl e depositio n o n leave s ha s le dsom e in

vestigator s t o stipulat e tha t lea dma y ente r

plant s throug hth e leaves . Thi s woul dtypicall y require , however , tha t

th e lea dparticle s b e dissolve db y con stituent s o f

th e lea f surfac e and/o r

converte dt o th e ioni c formvi acontac t withwater . Th e forme r possibilit y i s no t

considere dlikely , sinc e cuticula r waxe s ar e relativel y iner t chemically . Zimdah l an d Arvik 8 5 hav e show n in arathe r elegan t se t o f experi

ment s tha t

entr y o f ioni c lea dthroug hplan t leave s i s o f minima l importance . B y usin g th e lea f cuticle s o f severa l type s o f

plant s essentiall y a s membranes , the y foun dtha t

eve n hig hconcentration s o f lea dion s woul dno t

pas s throug hth e cuticle s int o distille d wate r o n th e opposit e side . Th e result s o f

th e studie s discusse dabov e generall y indicat e th e following : 1 . Th e uptak e o f

lea db y plant s fro msoi l i s highl y dependen t

o n th e chemica l equilibri a prevalen t

in th e soi l in question . Th e uptak e ca n probabl y b e controlle dthroug htreat men t o f th e soi l wit hmaterial s (e.g. , lime , phosphat e fertilizers , etc. ) tha t affec t thes e chemica l equilibria . 2 . Althoug huptak e rate s ar e enhance da t lowe r soi l p H levels , th e majorit y o f th e lea dtake n u p remain s in th e plan t roots ; onl y smalle r fraction s ar e translocate dt o th e shoots . 3 . Depositio n an dretentio n o f lea dparticle s o n plan t surface s ca n serv e a s arout e o f anima l o r huma n exposur e t o automotiv e lead . Thu s crop s grow n nea r

source s o f

hig htraffi c 6-2 4

### shoul dprobabl y b e considere dsuspec t

unles s appropriat e safet

y precaution s ar e taken . 6. 5 REFERENCE S FO RCHAPTE R6 1 . Habibi , K . Characterizatio n o f particulat e matte r

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menta l Pollution . Vol . 3 . Commissio n o f th e Europea n Communities , Luxembourg . 1975 . p . 1783-1788 . 23 . Purdue , L . J. , R . E . Enrione , R . J . Thompson , an dB . A . Bonfield . Determinatio n o f organi c an dtota l lea di n th e atmospher e b y atomi c absorptio n spectrometry . Anal . Chem . 45(3):527-528 , 1973 . 24 . Skogerboe , R . K . Analytica l chemistry . In: Environmenta l contaminatio n cause db y lead . Nationa l Scienc e Founda

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born e lea dparticles . Nature . 232:553-554/1971 . 26 . Pierrard , J . M . Photochemica l decompositio n o f lea d halide s fro mautomobil e exhaust . Environ . Sci . Technol . i(l):48-5l , 1969 . 27 . Robbins , J . A . an dF . L . Snitz . Bromin e an dchlorin e los s fro mlea dhalid e automobil e exhaus t particles . Environ . Sci . Technol . 6(2):164-169 , 1972 . 28 . Dzubay , T . G . an dR . K . Stevens . Application s o f X-Ra y fluorescenc e t o particulat e measurements . In: Secon d Join t Conferenc e o n Sensin g o f Environmenta l Pollutants , Washington , D . C . Instrumen t Societ y o f

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Pollut . Contro l Assoc . 26(8):753-766 , 197 6 82 . Singer , M . J . an dL . Hanson . Lea daccumulatio n in soil s nea r highway s i n th e Twi n Citie s metropolita n area . Soi l Sci . Soc . Amer . Proc . 33:152 , 1969 . 83 . Lagerwerff , J . V . an dD . L . Brower . Exchang e absorptio n o r precipitatio n o f

lea di n soil s treate dwit hchloride s o f aluminum , calciu man dsodium . Soi l Sci . Soc . Amer . Proc . 37(1):11-13 , 1973 . 84 . Gadde , R . R . an dH . A . Laitinen . Studie s o f heav y meta l absorptio n b y hydrou s iro n an dmanganes e oxides . Anal . Chem . 46(13):2022-2026 , 1974 . 85 . Zimdahl , R . L . an dJ . H . Arvik . Lea din soil s an dplants : a literatur e review . Crit . Rev . Environ . Control . 3:213-224 , 1973 . 86 . Santillan-Medrano , J . an dJ . J . Jurinak . Th e chemistr y o f lea dan dcadmiu mi n soil : soli dphas e formation . Soi l Sci . Soc . Am . Proc . 39:851-856 , 1975 . 87 . Lovering , G . T . Lea di n th e Environment . U.S . Geologica l Surve y Professiona l Pape r 957 . Washington , DC . 1976 . 9 0 p . 88 . Hem , J . D . an dW . H . Durum . Solubilit y an doccurrenc e o f lea di n surfac e water . J . AM . Wate r Work s Assoc . 65(8):562-568 , 1973 . 89 . Davies , P . H . an dW . H . Everhar . Effect s o f Chemica l Variation s i

n Aquati c Environments . Vol . III . Lea dTox

icit y t o Rainbo w Trou t an dTestin g Applicatio n Factor . Concept . U.S . Environmenta l Protectio n Agency , Offic e o f Researc han dMonitoring , Researc hTriangl e Park , N.C . Pub . No . EPA-R3-73-011C . 1973 . 8 0 p . 90 . Hem , J . D . Geochemica l control s o f lea dconcentratio n i

n strea mwate r

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tributio n i n Relatio n t o Automobil e an dMin e an d Smelte r Sources . In: Heav y Metal s i n th e Aquati c En

vironment . P . A . Krenke l (ed.) . Pergamo n Press , Ne w York . 1975 . p . 231-241 . 92 . Bondarenko , G . P . A n experimenta l stud y o f th e solubilit y o f galen ai n th e presenc e o f fulvi c acids . Geochem . Int . 5:525-531 , 1968 . 93 . Wong , P . T . S. , Y . K . Chau , an dP . L . Luxon . Methylatio n o f lea din th e environment . Nature . 253(5489):263-264 , 1975 . 94 . Schmidt , U . an dF . Huber . Methylatio n o f organolea dan d lea d(II ) compound s t o (CH3)4P b b y microorganisms . Nature . 259:157-158,1976 . 95 . Jarvie , A . W . P. , R . N . Markall , an dH . R . Potter . Chemi

ca l alkylatio n o f

lead . Nature . 255(5505):217-218 , 1975 . 96 . Taylor , R . T . an dM . L . Hanna . Methylcobalamin : Methylatio n o f

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6-2 8

## 7 . ENVIRONMENTA L CONCENTRATION S AN D POTENTIA L EXPOSURE S 7. 1 AMBIEN T AI REXPOSURE S Severa l studie s o n concentration s o f lea din th e ambien t ai r hav e bee n undertaken . Thes e studie s wer e generall y intende dt o surve y th e level s an ddis

tribution s o f

lea din th e genera l ai r

environmen t

an d aroun dsources . The y usuall y wer e no t designe din conjunctio n wit hepidemiologica l studie s o f th e con curren t effect s o f

lea do n ma n o r

othe r organisms . Ye t tha t i s th e contex t

in whic hthes e studie s mus t no w b e interprete dt o she dth e mos t ligh t possibl e o n th e concentration s likel y t o b e encountere din variou s environmenta l settings . Measurement s take n withhigh-volum e samplers , dust-fal l buckets , an dparticl e siz e fractionator s ar e include di n thes e studies ; however , withth e excep tio n o f th e NAS N dat afro m197 0 throug h1974 , qualit y contro l an dinterlaborator y comparabilit y ar e unspecified . Th e effectivenes s o f som e filte r medi ai n collectin g ver y smal l lead-containin g parti

cle s ha s bee n questioned ; thi s subjec t i s discusse din Chapte r 4 . Th e studie s sho w that : 1 . Lea dtypicall y occur s i n urba n airborn e sus pende dparticle s 0. 5 fim o r les s in mas s me dia n equivalen t

diamete r

a t annua l averag e concentration s rangin g fro m<0. 1 t o 5 /xg/m 3 , withan overal l averag e o f 1 t o 2 Mg/m 3

. 2 . Urba n concentration s o f lea dhav e decline d somewha t

sinc e 1970 . 3 . Suspende dparticle s in rura l ai r sample s con tai n lea dat

concentration s rangin g fro m <0.0 1 t o 1. 4 /ug/m 3 , withan overal l averag e o f abou t 0. 2 /j.g/m 3

. 4 . Monthl y averag e concentration s o f lea din urba n settleabl e particle s rang e fro m3 t o 1 2 mg/m 2 -mo . 5 . Indoo r

concentration s o f

lea dar e quit e variable , bu t

ar e generall y one - t o two-third s th e concentration s o f adjacen t

outdoo r levels . A discussio n o f

th e NAS N measurement s follows . Summarie s o f additiona l studie s ca n b e foun din Ap

pendi x C . 7. 1 . 1 Nationa l Ai rSurveillanc e Networ k(NASN ) Dat a Sinc e 1957 , sample s o f

suspende dparticulat e mat te r collecte da t

som e 30 0 urba n an d3 0 nonurba n NAS N site s hav e bee n analyze dfo r trac e metals , in

cludin g lead . Onl y dat abeginnin g wit h196 6 ar e summarize dhere , however , becaus e th e procedur e use dbefor e 196 6 wa s foun dt o recove r onl y abou t

5 0 percen t o f th e lea dactuall y present . Th e emissio n spectrograph ^ metho dno w employe di n th e analysi s ha s sufficien t

sensitivit y t o permi t

detectio n o f lea din al l urba n an dmos t nonurba n samples . Summarie s o f

th e dat afo r

urba n an dnonurba n NAS N site s fo r

196 6 throug h197 4 ar e presente di n Table s 7- 1 an d7-2 , whic hcategoriz e th e site s b y fou r successiv e annua l averag e concentratio n ranges. ' 2 Th e majorit y o f th e urba n site s (9 1 percen t o f th e site-years ) reporte dannua l average s belo w 2. 0 Mg/m 3 , an dth e majorit y o f nonurba n site s (8 6 per cen t o f th e site-years ) reporte dannua l average s belo w 0. 2 ,y,g/m 3

. Sample s collecte db y th e NAS N fro m197 0 throug h197 4 wer e combine dfo r analysi s int o quar terl y composites . Table s 7- 3 an d7-4 , respectively , giv e th e cumulativ e frequenc y distribution s o f urba n an dnonurba n quarterl y composit e value s fo r 197 0 throug h1974. ' Urba n NAS N site s fo r

whic hannua l averag e con centration s hav e bee n 3. 0 figlm 3 o r greate r ar e liste d in Tabl e 7-5. 1 2 Highes t concentration s fo r

shorte r interval s (quarterl y an d24-hr ) hav e bee n included , wher e available , in orde r t o indicat e th e variatio n in concentratio n wit haveragin g tim e an dpotentia l pea k exposur e conditions . A larg e numbe r o f Souther n Californi acitie s ar e include din th e lis t becaus e o f

th e heav y automobil e traffi c in thes e areas . Bot hth e annua l averag e an dmaximu mvalue s at Lo s Angele s Count y site s wer e consistentl y high , 7- 1P.9 4

TABL E 7-1 . NUMBE R O F NAS N URBA N STATION S WHOS E DATA FAL L WITHI N SELECTE D ANNUA L AVERAG E LEA D CONCENTRATIO N INTERVALS , 1966-1974 1 • * TABL E 7-2 . NUMBE R O F NAS N NONURBA N STATION S

WHOS E DAT A FAL L WITHI N SELECTE D ANNUA L AVERAG E LEA D CONCENTRATIO N INTERVALS , 1966-19741 2 Yea r 1966 : No . station s Percen t 1967 : No . station s Percen t 1968 : No . station s Percen t 1969 : No . station s Percen t 1970 : No . station s Percen t 1971 : No . station s Percen t 1972 : No . station s Percen t 1973 : No . station s Percen t 1974 : No . station s Percen t 1966-1974 : No . station s Tota l percen t < 0. 5 9 9 4 3 1 4 9 5 2 9 5

— 1 6 9 2 0 1 5 1 9 1 5 9 6 8 Concentratio n interval , ug 0.5-0.9 9 4 0 4 2 3 7 3 2 6 7 4 5 4 6 2 5 5 4 3 3 2 3 2 1 6 7 3 7 7 6 5 5 6 9 5 3 47 9 3 8 1.0-1. 9 4 0 4 2 6 3 5 5 5 4 3 6 10 3 5 7 8 0 5 0 6 4 5 8 8 4 4 7 3 6 2 6 3 8 2 9 56 2 4 5 2.0-3. 9 6 6 9 7 10 6 2 3 1 2 1 5 9 2 1 1 9 1 2 7 4 3 4 3 10 4 8 /m 3 4.0-5. 3

—

— —

0

0 0 6 1 Tota l 9 5 10 0 11 3 10 0 14 6 10 0 17 8 10 0 15 9 10 0 10 9oooO00o 13 7 10 0 13 0 10 0 124 7 10 0 Yea r

1966 : No . station s Percen t 1967 : No . station s Percen t 1968 : No . station s Percen t 1969 : No . station s Percen t 1970-1971 : No . station s Percen t 1972 : No . station s Percen t 1973 : No . station s Percen t 1974 : No . station s Percen t 1966-1974 : No . station s Tota l percen t < 0.0 3

—

1 5 1 5

—

— — 10 2 9 9 3 9 3 1 9 2 4 1 5 Concentratio n interva l 0.03-0.09 9 1 0 5 2 7 3 5 1 5 7 5 1 1 5 2

— — 4 1 2 7 3 1 5 3 1 5 9 3 6 0.10-0.1 9

6 3 2 10 5 0 4 2 0 9 4 3 7 7 0 9 2 6 6 2 6 6 3 8 5 7 3 5 ng'm 3

0.20-0.4 5 3 1 6 2 10

— — 1 5 3 3 0 1 1 3 3 1 4 2 1 2 2 3 1 4 Tota l 1 9 10 0 2 0 10 0 2 0 10 0 2 1 10 0 10 10 0 3 4 10 0 2 3 10 0 1 6 10 0 16 3 10 0 TABL E 7-3 . CUMULATIV E FREQUENC YDISTRIBUTION S O F QUARTERL YLEA D MEASUREMENT S ATURBA N STATION S B YYEAR , 197 0 THROUG H 1974 ' (/u.g/m3 )

Yea r 197 0 197 1 197 2 197 3 197 4 No .

quarterl y composite s 79 7 71 7 70 8 55 9 59 4 Mi n

LD " LD a LD » LD a 0.0 8 1 0

0.4 7 0.4 2 0.4 6 0.3 5 0.3 6 3 0 0.7 5 0.7 1 0.7 2 0.5 8 0.5 7 5 0 1.0 5 1.0 1 0.9 7 0.7 7 0.7 5 Percentil e

7 0 1.3 7 1.4 2 1.2 5 1.0 5 1.0 0 9 0 2.0 1 2.2 1 1.9 3 1.6 2 1.6 1 9 5 2.5 9 2.8 6 2.5 7 2.0 8 1.9 7 9 9 4.1 4 4.3 8 3.6 9 3.0 3 3.1 6 Max .

5.8 3 6.3 1 6.8 8 5.8 3 4.0 9 Arithmeti c

Mea n 1.1 9 1.2 3 1.1 3 0.9 2 0.8 9 Std .

dev . 0.8 0 0.8 7 0.7 8 0.6 4 0.5 7 Geometri c Std . Mea n dev . 0.9 9 1.8 4 1.0 0 1.8 9 0.9 3 1.8 7 0.7 6 1.8 7 0.7 5 1.8 0 a L D = limi t o f detection .

TABL E 7-4 . CUMULATIV E FREQUENC YDISTRIBUTION S O F QUARTERL YLEA D MEASUREMENT S

ATNONURBA N STATION S BYYEAR , 197 0 THROUG H 1974 '

(ng/m 3 )

197 0 197 1 197 2 197 3 197 4 12 4

8 5 13 7 10 0 7 9 0.00 3

0.00 3 0.00 7 0.01 5 0.00 7 0.00 3 0.00 3 0.00 3 0.00 3 0.26 7 0.38 3 0.62 8

0.00 3 0.00 3 0.00 3 0.00 3 0.12 7 0.20 4 0.78 3 0.00 7 0.00 7 0.10 7 0.16 6 0.29 4 0.39 2 0.95 0 0.01 5 0.01 5 0.05 8 0.13 2 0.23 3 0.39 2 0.69 8 0.00 7 0.05 3 0.08 7 0.14 1 0.22 1 0.31 7 0.49 6 1.47 1 1.13 4 1.04 8 0.93 9 0.53 4 0.08 8 0.19 0

0.04 7 0.15 5 0.13 9 0.16 9 0.11 0 0.14 9 0.11 1 0.11 1 Yea r N o

quarterl y composite s Mi n 1 0 3 0 5 0 Percentil e 7 0 9 0 9 5 9 9 Max . Arithmeti c Std . Mea n dev . Geometri c Std . Mea n aev . 0.04 0 3.72 0.00 8 4.8 0 0.09 0 2.5 9 0.06 8 2.77 0.08 3 2.3 0 7- 2TABL E 7-5 . NAS N STATION S WIT H ANNUA L AVERAG E LEA D CONCENTRATION S 23. 0 Mg/m 31 < 2 Yea r an d statio n 1966 : Phoenix , Ariz . Burbank , Calif . Lo s Angeles , Calif . Pasadena , Calif . 1967 : Lo s Angeles , Calif . 1968 : Burbank , Calif . Glendale , Calif . Lon g Beach , Calif . Lo s Angeles , Calif . Pasadena , Calif . 1969 :Fairbanks , Alask a Phoenix , Ariz . Burbank , Calif . Glendale , Calif . Lo s Angeles , Calif . Sa n Juan , Puert o Ric o Dallas , Tex . 1970 : Burbank , Calif . Glendale , Calif . Lo s Angeles , Calif . Sa n Juan , Puert o Ric o Dallas , Tex . 1971 : Anaheim , Calif . Burbank , Calif . Sant a Ana , Calif . Lo s Angeles , Calif . 1972 : Burbank , Calif . Glendale , Calif . Lo s Angeles , Calif . Sa n Juan , Puert o Ric o 1973 : Burbank , Calif . Averag e 3. 2 3. 7 3. 6 3. 6 3. 1 4. 4 3. 0 3. 3 3. 9 3. 5 3. 2 3. 1 3. 5 3. 1 4. 6 3. 8 3. 0 4. 9 3. 5 4. 5 3. 7 3. 2 3. 3 5. 3 3. 5 4. 6 3. 2 3. 5 3. 1 5. 0 4. 0 Maximu m

Quarterl y composite 8. 1 6. 0 11. 0 4. 3 5. 4

— — — — — 4. 8 7. 1 4. 7 4. 5 5. 7 4. 2 5. 2 5. 8 4. 2 5. 6 4. 1 3. 8 4. 0 6. 2 4. 6 6. 3 6. 7 5. 2 4. 8 6. 9 5- 2 24-h r

— ' ' — — —

— 14. 0 7. 5 12. 0 10. 0 8. 3

— — — — — — —

— — — — —

— — — —

— — — —

— apparentl y becaus e o f location , topography , an d meteorologica l condition s tha t favo r retentio n o f pollutant s in th e ai r

ove r th e area . Ambien t particulat e lea ddat afro mNAS N wer e studie dfo r

trend s ove r

th e 10-year

perio dfro m 196 5 throug h1974 . Figur e 7- 1 show s th e 10th , 50th , an d90t hpercentile s fo r dat afro m9 2 NAS N urba n sites. 3 Urba n lea dconcentration s a s describe db y th e 50t hpercentile s increase dfro m196 5 unti l 197 1 an d the n decline dfro mabou t 1. 1 ,ug/m 3 t o 0.8 4 /xg/m 3 —abou t

a24-percen t

decrease , wit hmos t

o f thi s declin e occurrin g betwee n 197 2 an d1973 . Th e othe r percentile s exhibi t

asimila r

pattern . Thi s genera l patter n describe s th e tren dfo r mos t o f th e site s studied . Trend s in th e percentag e o f lea din th e tota l particulat e matte r measure dals o follo w thi s pattern , whic hindicate s tha t th e trend s in lea dar e no t jus t aresul t o f genera l particulat e control s bu t ar e adirec t

resul t o f decrease s in lea demissions .

E • a \ —i—i—i—i—i—r

90T H PERCENTIL E

Figur e 7-1 . Seasona l pattern s an d trend s I n quarterl y averag e urba n lea d concentrations. 3 Th e seasona l patter n in quarterl y composit e value s (soli dline s i n Figur e 7-1 ) show s tha t th e high

es t level s o f

airborn e lea doccurre di n th e winte r quarter s (firs t

an dfourth ) an dth e lowes t level s in th e summe r

quarter s (secon dan dthird) . I n contrast , automotiv e emission s o f lea dwoul db e expecte dt o b e greate r

in th e summe r

fo r tw o reasons : (l ) gasolin e usag e i s highe r in th e summer , an d(2 ) lea d conten t i s raise di

n summe r

gasoline s t o replac e som e o f th e mor e volatil e high-octan e component s tha t canno t b e use din summertim e gasolines . Evi

dentl y summertim e meteorologica l condition s ex pedit e th e movemen t

o f thes e large r

emission s mor e quickl y an dwidel y throug hth e atmospher e o n thei r wa y t o subsequen t

destination s in vegetation , crops , soil , an dwater . Sinc e abou t

th e 197 0 mode l year , automobile s hav e bee n buil t

wit hlower-compressio n engine s tha t ca n us e lower-octan e gasolin e an dthu s gasolin e with lowe r lea dcontent . A s aresul t o f thi s engin e modification , practicall y al l car s buil t sinc e 197 0 ar e abl e t o us e regula r

gasolin e instea do f

th e mor e leade dpremiu mfuels . Figure s 7- 2 an d7- 3 show , respectively , th e percentag e o f th e total , marke t

fo r regula r an dpremiu mgasoline s an dth e tren din lea d conten t o f gasolines. 4 Th e result s o f th e engin e modification s ca n b e clearl y see n in th e lowe r lea d conten t in gasolin e (bot hin regula r an dpremiu m grades ) an din th e subsequen t increas e in regula r gasolin e sale s an ddecreas e in premiu msales . Thes e 7- 3P.9 6

factors , couple dwithth e us e o f amodes t

amoun t o f low-lea dan dno-lea dgasolin e introduce dat abou t thi s sam e time , ar e identifie da s principall y responsi

bl e fo r th e observe ddecreas e in ambien t lea dcon centration s ove r

thi s period . Th e increasin g us e o f unleade dgasolin e resultin g fro mEP A regulations , whic hi s reflecte din Figur e 7-2 , will lea dt o eve n lowe r level s o f

atmospheri c pollutio n in th e future . Th e effec t

o f thes e change s i s enoug ht o overrid e th e genera l increas e in annua l gasolin e consumptio n o f abou t 5 percen t

typica l o f

recen t year s (excep t 1974) . Thi s increas e i n gasolin e consumptio n proba

bly doe s no t

proportionatel y affec t man y urba n monitorin g site s (whic har e chiefl y center-cit y loca

tions ) becaus e thei r

neighborhood s ar e generall y at o r nea r traffi c saturation . Ther e ma y eve n b e in

stance s o f

areductio n in vehicl e mile s travele din downtow n area s becaus e o f ca r pooling , improve d mas s transi t

systems , an dth e los s o f busines s activit y t o suburba n shoppin g centers .

O 3 0 I z U J U F . 2 0 I I I I I I I I I I I I I I I I

REGULA R GA S SALE S 1% ) 

# f

PREMIU M GA S SALE S 1% )

UNLEADE D GA S SALE S (% l _ 6 2 6 4 6 6 6 8 7 0 7 2 7 4 7 6 Figur e 7-2 . Nationwid e trend s I n regular , premium , an d unleade d gasolin e sales , 1960-1976. 4 I n additio n t o th e NAS N study , anumbe r o f othe r studie s involvin g majo r citie s an drura l area s hav e bee n undertaken . Thes e dat asuppor t th e NAS N result s (se e Appendi x C) . 7.1. 2 Airborn e Particl e Siz e Distributio n I n 1970 , acascad e impacto r networ k wa s estab

lishe db y EP A in si x citie s (Cincinnati , Chicago , Denver , Philadelphia , St . Louis , an dWashington , D.C. ) t o collec t

particulate s o f

differen t siz e range s fo r subsequen t

analysi s fo r

lea dan dothe r

metals. 5 Th e samples , collecte donc e ever y 2 week s fo r aful l I l I I I l l 6 0 6 2 6 4 6 6 7 0 7 2 7 4 7 6 Figur e 7-3 . Nationwid e trend s I n lea d conten t o t regula r an d premiu m gasoline , 1960-1976. 4 year , wer e analyze dfo r siz e distribution . Sample s fro meac hcit y wer e als o composite dquarterl y an d analyze dfo r

lea db y optica l emissio n spectroscopy . Th e averag e annua l tota l lea dconcentratio n a s determine din thi s stud y range dfro mahig hquarte r o f 3. 2 jLtg/m

3 in Chicag o t o alo w quarte r o f 1. 3 /ng/m 3 in Washington , D.C . Th e averag e mas s me dia n diamete r

fo r lea dparticle s range dfro m0.6 9 fim in St . Loui s t o 0.4 2 fim in Washington , D.C . Fifty-nin e t o 7 4 percen t o f th e lea dwa s associate d withparticle s smalle r

tha n I fim i n diameter . Quar

terl y an dannua l particl e siz e distributio n dat aar e presente din Tabl e 7-6 . 7.1. 3 Vertica l Gradient s o f Lea d i n th e At mospher e Ver y few studie s hav e bee n conducte dt o deter

min e th e variatio n o f

lea dconcentration s wit hheigh t abov e th e ground . O f

thos e tha t

wer e found , al l con taine dth e premise , eithe r explicitl y o r

implicitly , tha t th e concentration s bein g studie dderive dprin

cipall y fro mautomotiv e emissions . O f th e studie s foun din th e literature , non e wer e adequatel y designe dt o establis hth e lea dconcentratio n versu s heigh t relationship . Suc hastud y woul drequir e simultaneou s measuremen t (preferabl y continuous ) at give n heigh t

interval s ove r

alon g perio do f

tim e ( aminimu mo f

l year) . Eve n then , th e result s woul d b e vali donl y fo r

alocatio n havin g th e sam e charac

teristic s an dexperiencin g th e sam e atmospheri c con ditions . A singl e se t

o f concentratio n value s ob

taine dove r

shor t an dvariabl e tim e interval s i s no t sufficien t t o dra w conclusion s regardin g genera l ex posur e conditions . 7-4TABL E 7-6 . QUARTERL YAN D ANNUA L SIZ E DISTRIBUTION S O F LEAD-BEARIN G PARTICLE S FO R SI X CITIES . 1970

S TABL E 7-7. LEA D I N AI R O N MAI N STREET , BRATTLEBORO , VERMONT , SEPTEMBE R 12an d 13,1972» «

(ng/m3 )

Cit yan d quarte r o f yea r Averag e

concentration . jj.g/m 3 Averag e

mas s media n diameter . utr\ Chicago , III. : 1 2. 9 2 3. 5 3 3. 5 4 2. 9 Tota l yea r3. 2 Cincinnati , O. : 1 1. 0 2 2. 2 3 1. 9 4 2. 1 Tota l yea r1. 8 Denver , Colo. : 1 2. 0 2 1. 1 3 1. 4 4 3. 0 Tota l yea r1. 8 Philadelphia , Penn. : 1 1. 5 2 1. 2 3 1. 8 4 1. 9 Tota l yea r1. 6 St . Louis , Mo. : 1 1. 9 2 1. 6 3 1. 8 4 1. 8 Tota l yea r1. 8 Washington , D.C : 1 1. 3 2 1. 0 3 1. 3 4 1. 8 Tota l yea r1. 3 1.4 3 0.5 1 0.5 6 0.5 4 0.6 8 0.2 5 0.4 1 0.5 4 0.6 5 0.4 8 0.4 3 0.5 8 0.5 2 0.5 6 0.5 0 0.3 6 0.3 8 0.7 0 0.4 5 0.4 7 0.4 6 0.6 3 0.7 8 0.9 5 0.6 9 0.3 6 0.3 9 0.4 1 0.5 4 0.4 2 Percentag e

o f particle s 5//. m 4 1 6 5 6 5 6 4 5 9 7 9 7 4 6 9 6 7 7 2 7 6 6 8 6 9 6 6 7 0 7 4 7 4 6 2 7 0 7 0 6 8 6 3 5 9 5 3 6 2 7 6 7 3 7 4 7 1 7 4 Darro w an dSchroeder 6 measure dlea dconcentra tion s a t eigh t height s abov e stree t

leve l in Brat

tleboro , Vermont . Th e value s foun dar e show n in Tabl e 7-7 . Th e averag e traffi c flo w wa s reporte dt o b e 750 0 car s pe r

day . Th e concentratio n level s show n i n Tabl e 7- 7 ar e considerabl y highe r tha n thos e usuall y reporte din othe r cities . Th e investiga

tor s attribute dth e highe r value s t o greate r

collectio n efficiency an dlowe r

samplin g heights , bu t

thi s wa s no t confirmed . Th e samplin g time s wer e shor t an d variable . Genera l conclusion s regardin g th e rela

tionshi p o f

concentration s versu s heigh t canno t b e draw n fro mthes e data . Samplin g time s Heigh t abov e 8:36a.m . 10:2 0 a.m . 1:20p.m . street , f t 10:1 5 a.m . 12:0 0 noo n 3:0 0 p.m . 3:2 5 p.m . 4:3 5 p.m . 9/1 2 4:2 5 p.m . 1:02 p.m . 9/1 3 1 " 2 3 4 5 C 7 8 3 0 8.9 4

8.2 2 7.1 5 7.8 4

4.4 0 8.1 5 3.8 5

5.3 1 7.5 6 17.3 8

21.1 1 2.4 0 3.0 1

4.2 5

a Averag e ai rlea d valu e fo r54.3 8 m 3 ai r= 8.5 4 ^ g Pb/m 3

. D 1- . 2- , 3- . an d 4-ft heights : Averag e ai rlea d value s lo r13.5 3 m 3 ai r= 8.0 1 M 9 Pb/m 3

. c5- . 7- , 8- , 30-ft heights : Averag e ai rlea d value s fo r40.8 5 m 3 ai r= 3.9 6 n g Pb/m 3

. Edwards 7 ha s reporte dmeasurement s mad e in downtow n For t

Collins , Colo . Measurement s wer e mad e in astree t

canyo n forme db y two - an dthree

stor y building s (averag e height , 9 m) . Wit ha2. 3 m/se c win dfro mth e Northeas t (stree t runnin g north-south) , lea dconcentration s alon g th e eas t sid e o f th e stree t

canyo n range dfro m11. 3 /i,g/m 3 a t stree t leve l t o 4. 0 /u,g/m 3 a t

roo f level . O n th e wes t

sid e o f th e street , concentration s range dfro m0. 9 /ug/m 3 at stree t leve l t o 1. 3 /xg/m 3 at

roo f level . Value s fo r

tw o additiona l samplin g point s abov e th e rooftop s o n eac hsid e o f

th e stree t

wer e 0. 4 ttg/m 3 (eas t

side ) an d 0. 9 /xg/m 3 (wes t

side) . Lea dconcentration s 2 t o 5 block s awa y range dfro m0. 1 t o 0. 3 Mg/m 3

. Thes e dat areflec t

th e wid e variabilit y tha t ca n b e expecte d in urba n traffi c environments . Unde r moderat e cross-win dconditions , concentration s withi n th e canyo n wer e strikingl y anisotropic , an dstreet-leve l concentration s alon g th e upwin dbuildin g face s wer e substantiall y highe r

tha n alon g th e downwin dface . Wit hdifferen t

win dregimes , differen t buildin g con figuration , an ddifferen t stabilit y conditions , th e dis

tributio n o f

concentratio n value s woul dals o b e different . Barltro p an dStrelow 8 conducte da n ai r samplin g progra mat

apropose dnurser y sit e unde r a n ele

vate dmotorway . Th e heigh t o f th e motorwa y wa s 9. 3 m . Ai r

sampler s wer e operate da t fiv e t o seve n site s fro mMonda y t o Friday , 8 a.m . t o 6 p.m . fo r 1 year . Th e maximu mindividua l valu e observe dwa s 1 8 /xg/m 3

. Th e 12-mont hmea n range dfro m1.5 1 Mg/m 3 t o 1.3 5 /xg/m 3 , wit hstandar ddeviation s o f 0.9 1 an d0.66 , respectively . Th e author s reporte d tha t th e airborn e concentration s wer e independen t o f heigh t fro mgroun dleve l u p t o 7 m . PedCo-Environmental 9 measure dlea dconcentra tion s a t height s o f

5 an d2 0 f

t a t site s nea r

street s i n 7- 5P.9 8

Kansa s City , Mo . an dCincinnati , O . Th e samplin g site s i n Kansa s Cit y wer e describe da s unsheltered , unbiase db y localize dpollutio n influences , an dno t immediatel y surrounde db y larg e buildings . Th e Cincinnat i stud y are awa s locate di n aprimaril y resi

dentia l are awit hon e commercia l street . Sampler s wer e operate dfo r

24-h r period s fro m8 a.m . t o 8 a.m. ; bu t afew 12-h r

sample s wer e collecte dfro m8 a.m . t o 8 p.m . Dat awer e obtaine da t Kansa s Cit y o n 3 5 day s an da t

Cincinnat i o n 3 3 days . Th e rang e an d averag e value s reporte dar e show n in Tabl e 7-8 . I n al l case s excep t

two , th e measure dconcentration s wer e highe r

at 5 f t tha n a t 2 0 ft . Not e tha t

th e differenc e betwee n th e eas t sid e an dwes t

sid e o f th e street s wa s approximatel y th e sam e a s th e differenc e betwee n 5 an d2 0 f

t in height . TABL E 7-8 . AIRBORN E LEA D CONCENTRATION S AT5 - AN D 20-F TELEVATION S ABOV E STREE TLEVEL *

( M g/m3 )

Locatio n Rang e Kansa s Cit y0.8-4. 0 Cincinnat i 0.1-4. 6 Eas t sid e o f stree t 2 0 f t 5 ft Did . 1. 7 2. 0 0. 3 0. 9 1. 4 0. 5 Average s Wes t sid e o f stree t 2 0 I t 5 ft Diff . 1. 5 1. 7 0. 2 0. 6 0. 8 0. 2 Thes e dat areflec t

th e stron g influenc e o f th e geometr y o f

th e boundar y layer , wind , an dat mospheri c stabilit y condition s o n th e vertica l gra dien t o f lea dresultin g fro mautomobil e emissions . Th e varabilit y o f

concentratio n withheigh t i s furthe r complicate db y elevate demission s (i.e. , fro m stacks) . Concentration s measure dfro msamplin g station s o n th e roofs o f

building s severa l storie s hig h ma y no t reflec t actua l huma n exposur e conditions , bu t neithe r woul dasingl e samplin g statio n locate d at groun dleve l in abuildin g complex . Th e heigh t variatio n i n concentratio n resultin g fro mvertica l diffusio n o f

automobil e emission s i s likel y t o b e smal l compare dt o tempora l an dspatia l variation s resultin g fro msurfac e geometry , wind , an dat mospheri c conditions . 7. 2 MOBIL E SOURC E EXPOSURE S Severa l majo r

studie s hav e bee n undertake n t o determin e th e lea dlevel s in th e ai r an din settle d dus t nea r bus y highway s tha t

ar e fa r fro man y sta tionar y lea dsource . Amon g th e mos t intensiv e o f thes e studie s wa s th e Lo s Angele s Catalys t Stud y o f 1974-1975 , undertake n b y EP A t o measur e th e im

pac t o f th e catalyti c converte r o n ai r qualit y nea r

a majo r traffi c lea dsource. 1 0 , Tabl e 7- 9 summarize s th e 24-h r ambien t

con centration s o f

lea dobserve dat

tw o site s ( A an dC ) o n opposit e side s o f amajo r

freewa y durin g th e calenda r yea r 1975 . I n additio n t o th e monthl y averag e concentratio n a t eac hsite , th e monthl y averag e cross-freewa y differenc e in concentration s (C-A ) an drati o o f

concentration s (C/A ) ar e show n in th e table . Finally , th e percentag e o f hour s in th e mont hwhe n wind s wer e fro mth e directiona l secto r tha t i s mos t favorabl e t o th e detectio n o f cross-free

wa y difference s i s show n in th e righthan dcolumn . Th e favorabl e win ddirectio n interva l i s approx imatel y 160 ° t o 290 ° an dwa s define do n th e basi s o f concentratio n o f

carbo n monoxide , whic hi s atrace r fo r mobile-sourc e pollutants . TABL E 7-9 . MONTHL YAVERAG E LEA D CONCENTRATION S FO R 197 5 LO S ANGELE S CATALYS TSTUDY' "

Mont h Sit e A . Mg/m 3 SiteC .

jjg/m J Difference .

C- A Ratio .

C/ A % Favorabl e win d direction 8 Januar y February Marc h Apri l Ma y Jun e Jul y Augus t Septembe r Octobe r Novembe r 6. 0

4. 1 3. 2 2. 8 1. 8 1. 4 1. 9 2. 8 3. 7 4. 2 4. 8 6. 2 4. 8 5. 2 6. 0 7. 4 8. 1 8. 0 8. 4 8. 5 7. 3 6. 6 0. 2

0. 5 2. 0 3. 3 5. 6 6. 8 6. 1 5. 7 5. 0 3. 3 1. 7 1.0

3 1.1 8 1.6 3 2.1 4 4.0 6 5.6 8 4.2 7 3.0 0 2.3 0 1.7 4 1.3 7 28. 2 35. 2 43. 3 47. 6 65. 6 71. 2 68. 0 61. 6 59. 5 49. 4 31. 6 8 Fro m At o C ( S + SW + W winds) . A ver y stron g seasona l effec t i s observe din th e data , withconcentration s a t Sit e C exceedin g thos e at Sit e A b y onl y 3 percen t in January , increasin g t o amaximu mdifferenc e o f ove r 40 0 percen t

in June , an dsubsequentl y decreasin g durin g th e fal l month s (n o dat awer e collecte ddurin g th e mont ho f Decem

ber) . A s expected , ther e i s astron g linea r relation

shi p betwee n th e occurrenc e o f favorabl e win d directio n an dth e observe dcross-freewa y differenc e in lea dconcentration . Th e correlatio n coefficien t betwee n th e tw o variable s i s 0.96 , indicatin g tha t almos t al l o f th e variatio n in th e cross-freewa y con centratio n o f

lea dma y b e accounte dfo r b y th e seasona l variatio n in th e occurrenc e o f favorabl e win ddirection . I n astud y conducte din London , England, 1 1 am bien t ai r level s o f organi c lea dwer e measure da t ur ba n sites . Concentration s o f 0.0 4 t o 0.1 1 M

g organi c Pb/m 3 wer e foun do n street s o f varyin g width s an d traffi c flow . Thes e value s wer e 0. 3 t o 2. 6 percen t o f tota l airborn e lead . Th e leve l o f organi c lea dinsid e abus y tunne l wa s 0.0 2 figlm 3 , o r 0. 1 percen t

o f th e tota l airborn e lead . No t surprisingly , organi c lea d concentration s measure dat abus y servic e statio n 7- 6

### range dfro m0.2 1 t o 0.5 9 figlm 3 

### , o r 3. 9 t o 9. 7 per cent o f tota l airborn e leada

t that site . A t ales s busy servic e station , th e concentratio n o f organi c lea

d was 0.0 7 Mg/m3



### . o r



### 4. 2 percent

o f tota l airborn e lead a t that site . Dat aobtaine di

n anumber

o f othe r studie s on lea di n dust s nea

r roadway s ar e summarize di n Ta

ble s 7-1 0 and7-11 . Th e abov e dat ademonstrat e tha t abnormall y highconcentration s o f leadar e foundi

n th e ai r an ddus t nea r majo r roadways , an dtha t

peo pl e who liv e o r

wor k (e.g. , traffi c policemen , servic e statio n an dgarag e attendants ) i n thes e area s ar e ex posedt o hig

hleadconcentrations . Fo r comparison , Tabl e 7-1 2 summarize s lea di n dust s fro mnominall y residential urban areas . Thes e concentration s hav e awider rang e than thos e i

n traffic-oriente ddus t

samples . They are higher i n th e vicinit y o f a n identifie dpoint

sourc e suc

ha s th e E

l Pas o smelter , bu t

th e majorit

y o f th e reading s are lowe r than thos e o

f th e traffic-oriente dsamples . 7 3 POIN T SOURC E EXPOSURE S Severa l studie s hav e bee

n undertake n t o investig

ate lea dlevel s i n th e vicinit

y o f variou s point

source s o f lea demissio n suc

has smelter s or

battery plants . B y fa r th e mos t complete an dinformativ e studie s are TABL E 7-10 . LEA D DUS TO N AN D NEA R HEAVIL Y TRAVELE D ROADWAY S Samplin g sit e Washington , DC : Bus yintersectio n Man ysite s Chicago : Nea rexpresswa y Philadelphia : Nea rexpresswa y Brooklyn : Nea rexpresswa y Ne wYor k

City : Nea rexpresswa y Detroit : Stree t dus t Philadelphia Gutte r(lo wexposure ) Gutte r(lo wexposure ) Gutte r(hig h exposure ) Gutte r(hig h exposure ) Miscellaneou s U.S . Cities : Highway s an d tunnel s Netherlands : Heavil ytravele d road s Concentratio n ji g Pb/ g 1282 0 (4000-8000)1 2 660 0 (3000-8000)1 3 (900-4900)1 " 20001 5 (966-1213)1 6 150 7 (270-2626) " 326 2 (280-8201)1 ' (10000-20000)1 8 50001 9 TABL E 7-11 . LEA D CONTEN TI N O R O N ROADSID E SOI L AN D GRAS S A S A FUNCTIO N O F DISTANC E FRO M TRAFFI C AN D GRAS S DEPT H I N PROFILE * Sit e an d distanc e fro m road , m Lea d content , iig/ g dryweigh t Gras s 0- 5 c m

soi l deat h 5-1 0 c m

soi l deDt h 10-1 5 c m

soi l dent h Wes t o t U.S . 1 , nea rPlan t Industr yStation , Beltsville , Md. : 8 1 6 3 2 Wes t o f southboun d lanes , Washington-Baltimor e Parkway , Bladensburg.Md. : 8 1 6 32 Wes t o f Interstat e 29 , Platt e City , Mo. : 8 1 6 32 Nort h o f Seymou rRoad , Cincinnati , O. : 8 1 6 3 2 68. 2 47. 5 26. 3 52 2

37 8 16 4 46 0

26 0 10 8 41 6

10 4 6 9

51. 3 30. 0 18. 5

21. 3 12. 5 7. 5

31. 3 26. 0 7. 6 54 0

20 2 14 0

24 2 14 0 6 1 15 0 10 1 5 5 30 0

10 5 6 0

11 2 10 4 5 5

2 9 1 4 1 0 9 8

6 0 3 8 9 5 6 6 6 0

1 1 8. 2 6. 1

a Adapte d fro m Lagerwerf f an d Spech t (cite d i n Referenc e 20) . 7-7P.10 0

TABL E 7-12 . LEA D DUS TI N RESIDENTIA L AREA S

Samplin g sit e Concentration , M 9 Pn/ g Philadelphia : Classroo m Playgroun d Windo wframe s Bosto n an d Ne wYork : Hous e dus t Brattleboro , Vt. : I n hom e Birmingham , England : I n hom e Ne wYor k

City : Middl e clas s residentia l E l Paso , Texas , Smeltertow n dus t at : 0- 1 mil e 1- 2 mile s 2- 3 mile s > 4 mile s Philadelphia : Urba n industria l Residentia l Suburba n 200 0 300 0 17501 ? (1000-2000) 2 1 (500-900) 6 50001 " (608-742)1 5

3685 3 (2800-103750)2 2 272 6 (100-84000)2 2 223 4 (100-29386)2 2 215 1 (200-22700)2 2 385 5 (929-15680)2 3 61 4 (293-1030)2 3 83 0 (277-1517)2 3 thos e carrie dou t

b y Yanke l e t

al. 2 4 an dLandriga n e t al. 2 5 in th e neighborhoo do f asmelte r

in Silve r Valley , Idaho . Consequently , th e dat afro mthes e studie s wil l b e describe dher e in som e detail . Othe r studie s carrie dou t

in Solan o County , Calif. ; Omaha , Neb. ; E l Paso , Tex. ; Helen aValley , Mont. ; Missouri ; Helsinki , Finland ; Mez aRive r Valley , Yugoslavia ; an dOntario , Canada , ar e summarize d in Appendi x C . Thei r

finding s ar e in substantiv e agreemen t

wit hthos e o f

th e Idah o study . Yanke l an dvo n Lindern 2 4 define dfiv e stud y area s arrange dconcentricall y aroun dth e smelte r an dtw o contro l areas . Are a1 consiste do f home s withi n 1 mil e o f

th e smelter ; Are a2 , 1 t o 2-1/ 2 mile s fro msmelter ; Are a3 , 2-1/ 2 t o 6 miles ; Are a4 , 6 t o 1 5 miles ; an dAre a5 , 1 5 t o 2 0 miles . Environmenta l samples , includin g surfac e soil , hous e dust , paint , grass , an dgarde n vegetable s wer e collecte da t th e home s i n eac harea , a s wer e bloo dsample s fro mth e residen t childre n age d1 t o 9 years . Th e mea n lea d level s foun din th e ambien t air , soil , an dhous e dus t al l decrease dwithincreasin g distanc e fro mth e smelter . A s mentione din Chapte r 12 , th e bloo dlea d level s o f th e residen t

childre n followe dasimila r pattern . Ambien t ai r lea dlevel s wer e measure db y high

volum e sampler s statione dthroughou t th e Silve r Valley . A highl y significan t relationshi p betwee n distanc e fro mth e smelte r an dambien t

ai r lea dcon centratio n wa s found , an dthi s relationshi p wa s use d t o estimat e th e ambien t ai r lea dleve l fo r

an y loca

tio n i n th e stud y area . Th e mea n annua l ambien t ai r lea dlevel s nea r

asmelte r

fo r tw o differen t

year s (1974 , 1975 ) ar e show n graphicall y in Figur e 7-4 . Simila r result s wer e obtaine dfo r th e lea dconten t

o f soi l an dhous e dust . A s note din Chapte r 12 , th e children' s bloo dlea dlevel s correlat e quit e closel y withambien t

ai r lea dlevels , althoug hthi s resul t shoul dno t

b e interprete da s suggestin g tha t direc t inhalatio n o f

lea di s th e principa l exposur e mechan

is minvolved . On e resul t o f thi s pivota l stud y wa s tha t som e specifi c emergenc y measure s wer e take n in

E " a l~~ l AUG . 197 4 ES 3 AUG . 197 6

1.5 T1. 8 

# JL M 1 2 3 4 5 6 7

B YAREA ISE E TEXT ! Figur e 7-4 . Annua l ambien t ai r lea d concentratio n nea r a smelter , b

y area , befor e th e Augus t 1974 an d Augus t 1975 sur veys. 2 4 Are a 1 I s withi n 1 mil e o f smelter ; Are a 2 I s 1 t o 1-1/ 2 mile s fro m smelter ; Are a 3 , 2-1/ 2 t o 6 miles ; Are a 4 , 6 t o 1 5 miles ; an d Are a 5,1 5 t o 2 0 miles . 7- 8P. 1

197 4 (includin g coverin g contaminate dsoi l with clea n soi l an dreducin g smelte r emissions ) an d brough t abou t adecreas e i n bloo dlea dlevel s tha t wer e measure dayea r

later . Th e detail s ofth e bloo d lea dlevel s an dthei r

significanc e ar e presente din Chapte r 12 . Th e conclusio n t o b e draw n fro mthi s stud y (an dfro mth e simila r studie s referre dt o above ) i s tha t

peopl e wh o liv e in th e vicinit y of ama jo r industria l sourc e o f

lea d(e.g. , asmelter ) ar e ex pose dt o abnormall y hig hlea dconcentrations . 7. 4 DIETAR Y EXPOSURE S 7.4. 1 Foo d Th e rout e b y whic hmos t peopl e receiv e th e larges t portio n o f

thei r dail y lea dintak e i s throug h foods , withestimate s ofth e dail y dietar y lea dintak e fo r adul t male s rangin g fro m10 0 t o 50 0 /Ag/day. 2 6 Onl y afractio n o f

thi s ingeste dlea di s absorbed , a s discusse di n Chapte r

10 . Th e source s o f

th e lea dconten t

of unprocesse d vegetabl e food s hav e bee n note dearlie r (Sectio n 6.4.3) . Studie s o f

th e lea dassociate dwit hcrop s (nea r highways ) hav e show n tha t bot hlea dtake n u p fro msoi l an daeroso l lea ddelivere db y depositio n ar e foun dwithth e edibl e portion s o f commo n vegetabl e crops . However , ther e i s enormou s variabilit y in th e amoun t o f lea dassociate dwith suc hcrop s an din th e relativ e amount s o f lea din an d o n th e plants . Severa l factor s ar e involved , th e mos t prominen t

o f whic hare : th e plan t

species , th e traffi c density , th e meteorologica l conditions , an dth e loca l soi l conditions. 273 3 Th e variabilit y induce db y difference s in th e abov e factors , couple dwit hth e fac t tha t man y studie s hav e neglecte ddifferentiatio n betwee n lea do n plant s versu s lea di n th e plants , make s i t difficul t t o generalize . Dat ao f Schuc k an d Locke 2 9 sugges t

tha t in som e case s (e.g. , tomatoe s an doranges) , muc ho f th e surfac e lea di s readil y remove db y washing . Bu t a s note di n Sectio n 6.4.3 , thi s i s no t

universall y true ; in som e case s muc hmor e vigorou s washin g procedure s ar e required . I n vie w o f

th e wid e variabilit y o f soi l condition s (pH , organi c matter , catio n exchang e capacity , phosphoru s content , etc.) , o f meteorolog y (especiall y win dcondition s an drainfall) , an dofth e effect s o f specie s diversit y o n th e route s o f lea dac cumulation , onl y crud e genera l correlation s betwee n ai r lea dlevel s an dfoo dcro p lea dlevel s ar e possible . Thi s i s influence db y th e fac t tha t th e lea dassociate d withplant s ma y b e derive dfro mnatura l sources , fro mautomotiv e sources , an dfro mothe r source s suc ha s manufacturin g o r combustion . On e stud y in Souther n Californi areporte dtha t 6 0 t o 7 0 percen t ofth e lea dassociate dwit hoa t top s wa s directl y at tributabl e t o automobil e (aerosol ) emissions , bu t it di dno t distinguis hbetwee n lea din th e edibl e por tio n (grain ) an dlea do n th e hull s o r chaff. 2 7 Thi s sam e stud y reporte dtha t lettuc e grow n in th e Salina s Valle y ha d3 t o 2 5 pp mlea d(dr y weight ) associate d withit , wherea s th e soi l lea dconten t wa s onl y 1 0 ppm . Th e lea dconten t

in th e lettuc e wa s reporte dt o b e 0.1 5 t o 1. 5 pp mo n afres hweigh t basis . Th e limite ddat aaccumulate dwer e use dt o deduc e tha t th e exces s lea dwa s delivere dt o th e lettuc e b y aeria l emissio n fro mautos , an dtha t remova l o f

lea dfro m automobil e exhaus t

woul dreduc e th e lea dconten t o f th e lettuc e b y a s muc ha s 8 0 percent. 2 7 I n othe r areas , th e contributio n woul db e smaller . Thoug h thes e figure s ma y b e accurate , the y ar e base do n som e rathe r

tenuou s assumption s tha t ar e no t wel l supporte db y observatio n an dver y limite ddata . Th e estimate s mus t

thu s b e considere dwithcaution . Moreover , on e canno t

extrapolat e fro mlettuc e o r oat s t o al l crops . Th e possibl e connectio n betwee n ai r lea dan d foo dlea dma y b e underscore db y comparison s be

twee n leaf

y vegetable s an dfoo dgrains . Studie s hav e show n tha t

th e edibl e portion s o f

grain s absor b ver y littl e ai r lead, 3 2 wherea s th e leaf y vegetable s retai n appreciabl e quantities. 272 9 An FD A survey 3 4 show s tha t grain s contai n approximatel y 2 0 percen t a s muc hlea da s th e leaf

y vegetables . I t

canno t b e con cluded , however , tha t

8 0 percen t

o f th e lea din al l leaf y vegetable s derive s directl y fro mai r becaus e th e differenc e mus t

als o reflec t

species-dependen t difference s in uptak e fro msoil . A n overal l analysi s ofth e dat aavailabl e support s th e contentio n tha t

plant s grow n nea r

bus y highway s consistentl y hav e mor e lea din an do n the mtha n thos e i n othe r areas . Thi s differenc e i s typicall y ver y har dt o detec t

a t distance s greate r

tha n abou t

10 0 t o 20 0 mfro mth e highway , thereb y reflectin g th e fac t tha t larg e percentage s o f

th e aeroso l lea dfal l ou t nea r roadways . I t

appear s reasonabl e t o poin t ou t tha t th e vas t majorit y o f

edibl e crop s markete di n thi s countr y ar e grow n at distance s o f

mor e tha n 10 0 t o 20 0 mfro mth e highwa y an dtha t muc ho f

th e aeroso l lea dca n b e remove dfro massociatio n with th e plant s b y processing . Clearl y ther e ar e excep tion s tha t

will influenc e bot hside s o f th e question . Fo r th e present , however , th e availabl e dat aar e no t sufficien t t o permi t

th e quantitativ e estimat e o f th e contributio n o f

automotiv e lea dt o foodstuffs o n a nationa l o r

eve n regiona l scale . Th e concentration s o f

lea di n variou s foo ditem s ar e highl y variable , an da s muc hvariatio n i s foun d 7- 9P. 2

withi n specifi c foo ditem s a s betwee n differen t foo d categories . Schroede r

an dBalassa, 3 5 in astud y o f America n foods , hav e foun dtha t th e range s ar e 0 t o 1. 5 mg/k g (ppm ) fo r

condiments , 0. 2 t o 2. 5 mg/k g fo r fis han dothe r

seafood , 0 t o 3. 7 mg/k g fo r meat s an deggs , 0 t o 1.3 9 mg/k g fo r grains , an d0 t o 1. 3 mg/k g fo r

vegetables . Al l o f

thes e value s refe r

t o unprocesse dfoods . A Britis hreport 3 6 o n lea din food s describe s simila r range s fo r

mea t an deggs , grai n product s (flou r

an dbread) , an dvegetables ; bu t concentration s u p t o 1 4 mg/k g wer e foun di n condiments , an du p t o 1 8 mg/k g in certai n shellfish . Th e amoun t

o f lea dtake n in withfoo dvarie s fro m perso n t o person . I t

depend s o n (a ) th e tota l amoun t o f foo deaten , (b ) th e histor y o f th e foo ddurin g growth , (c ) it s opportunit y t o acquir e intrinsi c lea d (absorbe dfro msoi l o r water ) an dextrinsi c lea d (deposite dinsecticide s o r contaminate ddusts) , an d (d ) dietar y habit s (suc ha s usin g fres hrathe r tha n canne dfoods) . O n aper-weigh t basis , th e dietar y in

tak e oflea db y childre n ha s bee n show n t o b e tw o o r thre e time s tha t

o f adults . Thi s additiona l dietar y in

tak e i s especiall y significan t whe n th e lea dadde dt o foo db y processin g an dt o wate r b y plumbin g (vide infra) i s considered . A 197 4 FD A surve y o f heav y metal s i n foods 3 7 foun drelativel y hig hlea dcon centration s in metal-canne dfoods . I n th e adul t foo d category , canne dfood s average d0.37 6 pp mlead , an dnon-canne dfood s average d0.15 6 pp mlead . I n th e bab y foo dcategory , canne dfood s (juices ) average d0.32 9 pp mlead , an dfood s in jar s average d 0.09 0 ppm . Th e repor t

o f th e surve y conclude s tha t fro mth e ag e o f

abou t 1 yea r on , canne dfood s com pris e 1 1 t o 1 2 percen t

o f aperson' s diet , bu t

the y contribut e abou t

3 0 percen t

o f th e averag e dietar y lea dintake . I n acompariso n mad e in th e Unite d Kingdom, 3 8 lea dconcentration s i n canne dfood s wer e foun dt o var y widel y withth e precis e natur e o f th e food , bu t

the y average dabou t

te n time s greate r tha n thos e i n fres hfoods . Th e soldere dsea mo f

ti n can s i s evidentl y th e ma jo r sourc e o f

thi s additiona l lea di n canne dfoods , an dincreasin g lea dconcentration s in sample s o f a can' s content s take n progressivel y neare r th e sea m hav e bee n found. 3 9 Similarly , ther e i s acorrelatio n betwee n increasin g lea dconcentration s i n canne d product s an dth e increasin g rati o o f th e can' s seam lengt ht o volume . O f

25 6 metal-canne dfood s ex amined , 3 7 percen t

containe d20 0 /xg Pb/lite r o r more ; 1 2 percen t

containe d40 0 /xg Pb/lite r o r more . Thes e level s ar e markedl y abov e th e potabl e wate r standar do f

5 0 ti g Pb/lite r

(0.0 5 mg/kg ) establishe d b y th e U.S . Publi c Healt hService . Canne dpe t food s hav e bee n foun dt o contai n 0. 9 t o 7. 0 pp mlea d(approximatel y 90 0 t o 7,00 0 /xg/liter), 4 0 an d1 8 product s average d2. 7 pp m(ap

proximatel y 270 0 /xg/liter) . Apar t fro mth e possibl e toxi c effect s o n pets , th e product s pos e ahazar dt o person s wh o ma y includ e the min thei r ow n diet . Th e lea dconten t

in mil k i s o f specia l interes t becaus e it

i s amajo r

componen t

o f th e diet s o f

in

fant s an dyoun g children . Th e FD A survey 3 7 foun d lea dconcentration s in whol e mil k rangin g fro m1 0 t o 7 0 tig/lite r

an daveragin g abou t

2 0 pig/liter . I n a recen t stud y b y Ziegle r

e t al., 4 1 seve n sample s o f bab y formul aan dthre e sample s o f whol e cow' s mil k wer e analyze din duplicate . Mea n concentration s o f lea dwer e 1 8 /xg/k g (rang e 1 5 t o 20 ) i n formul aan d 1 0 /xg/k g (rang e 7 t o 15 ) in mil k ( 1 /xg/k g i s approx imatel y 1 /xg/liter) . Lea dconcentratio n in infan t frui t juice s range dfro m2 3 t o 32 7 /xg/kg ; in fiv e varietie s o f

straine dfruits , i t

range dfro m1 3 t o 13 1 /xg/kg ; an din seve n varietie s o f straine dvegetables , lea dconcentratio n wa s 1 4 t o 7 3 /xg/kg . Tola n an d Elton 3 8 reporte d3 0 /x g Pb/lite r in fres hmil k

in Grea t Britai n an d5 0 /xg Pb/lite r in canne d(evapor

ated ) milk . Michel l an dAldous 3 9 reporte dacom parabl e averag e fo r

fres hwhol e mil k

purchase din Ne w Yor k

Stat e —4 0 /xg Pb/liter . Bu t thei r result s fo r evaporate dmil k

average d20 2 /xg Pb/lite r an d range da s hig ha s 82 0 /x g Pb/liter . Hanki n e t

al. 4 2 sugges t

a n additiona l food-relate d sourc e o f

potentia l lea dexposure , agai n predomi

nantl y affectin g children . Th e colore dportion s o f wrapper s fro mbaker y confections , candies , gums , an dfroze n confection s hav e lea dconcentration s rangin g fro m8 t o 10,10 0 ppm . Th e highe r con centration s ar e attribute dt o lead-containin g inks . N o relate dillnesse s wer e identified , no r wa s con taminatio n o f

th e foo dimplied ; bu t th e eatin g o f food s fro msuc hwrapper s an dth e lickin g o r chewin g ofth e wrapper s wer e postulate da s on e mor e avenu e fo r a n additiona l incremen t t o tota l lea dexposure . Th e presenc e o f

hig hlea dconcentration s in illici t whiske y (moonshine) , whic hi s stil l popula r in som e part s o f th e Unite dState s despit e th e repea l o f prohibition , cause s lea dpoisonin g i n adults . Th e ap paren t sourc e o f

th e lea di s th e soldere djoint s i n th e distillin g apparatus . Anothe r potentia l sourc e o f

dietar y lea dpoisonin g i s th e us e o f

inadequatel y glaze dearthenwar e vessel s fo r foo dstorag e an dcooking . A n impressiv e exam pl e o f thi s dange r

involve dth e sever e poisonin g o f a physician' s famil y in Idah o an dstemme dfro m drinkin g orang e juic e tha t ha dbee n store din a n earthenwar e pitcher. 4 3 Simila r cases , sometime s in

7-1 0P. 3

eludin g fatalities , hav e involve dothe r relativel y acidi c beverage s suc ha s frui t juice s an dsof

t drink s an dhav e bee n documente db y othe r workers. 444 5 Recen t report s o n lea din Europea n wines 46

- 4 7 sho w concentration s typicall y averagin g fro m13 0 t o 19 0 /xg/lite r

(0.1 3 t o 0.1 9 ppm ) an drangin g a s hig h a s 29 9 /xg/lite r

(0.29 9 ppm) . Measurement s o f lea d in domesti c wine s hav e no t bee n undertaken ; bu t

i f th e Europea n dat aar e indicative , wine s coul dcon tai n lea dconcentration s comparabl e t o processe d food s previousl y discussed . 7.4. 2 Wate r Th e U.S . Publi c Healt hService' s standard s fo r drinkin g wate r

specif y tha t lea dshoul dno t

excee d 5 0 /xg/lite r

(0.0 5 ppm) . Th e averag e adul t drink s abou t 1 lite r o f wate r pe r day . Th e presenc e o f

detec

tabl e amount s o f

lea din untreate dpubli c wate r sup plie s wa s show n b y Durum 4 8 t o b e widespread , bu t onl y afew sample s containe damount s abov e th e 5 0 /xg/lite r standard . Durfo r

an dBecker 4 9 analyze d untreate dan dtreate dwate r fo r th e larges t

U.S . cities , an dalmos t

al l pair s o f

sample s showe dasub

stantia l decreas e in lea dtha t wa s ascribabl e t o treat men t provided . A maximu mlea dconcentratio n o f 6 2 /xg/lite r

wa s detecte din finishe dwate r fro mon e o f severa l well s use din Sal t Lak e Cit y t o supplemen t thei r surfac e wate r

supply . Som e 9 5 percen t o f th e wate r supplie s sampled , however , ha dles s lea dtha n 1 0 /xg/lite r

in th e treate dwate r

befor e enterin g th e distributio n system . Eigh t o f th e wate r

supplie s dis

tribute dwate r

withap H o f

les s tha n 7 , whic hcoul d b e corrosiv e t o th e distributio n piping ; mos t ofthes e wer e in th e Northwest . A chemica l analysi s o f 59 2 interstat e carrie r

wate r supplie s in 197 5 showe donl y 0. 3 percen t

t o excee dth e 5 0 /xg/lite r standard. 5 0 Thes e sample s wer e collecte dafte r treatmen t

bu t befor e distribution , an dthe y represen t bot hsus pende dan ddissolve dlead . Interstat e carrie r wate r supplie s serv e planes , trains , buses , an dvessel s in in

terstat e commerce , an dthe y includ e almos t al l o f th e larges t

U.S . wate r

supplies . Th e presenc e o f

lea din drinkin g wate r

may resul t fro mcontaminatio n ofth e wate r sourc e o r

fro mth e us e o f lea dmaterial s in th e wate r distributio n system . Althoug hlea di s arelativel y mino r constit

uen t o f th e earth' s crust , it

i s widel y distribute din lo w concentration s in sedimentar y roc k an dsoil s (a s discusse din Chapte r

3) , an dnaturall y occurrin g deposit s ma y b e an importan t sourc e o f

contamina

tio n in isolate dinstances . Industria l wast e ma y als o contribut e t o th e lea dconten t o f wate r sources , bu t thi s appear s t o b e aloca l an dno t awidesprea dprob

lem . Th e extensiv e us e o f lea dcompound s a s gasolin e additive s ha s greatl y increase dth e availabilit y o f

lea dfo r solutio n in groun dan dsur fac e waters . Fo r

example , i

n astud y in east-centra l Illinois, 5 1 th e urba n portio n o f a n 86-square-mil e watershed , whic hconstitute d1 4 percen t ofth e area , contribute dabou t

7 5 percen t

o f th e lea din th e drainag e waters . Th e principa l sourc e o f thi s lea di s identifie da s automotiv e emissions . Detaile ddat are porte dfo r

1 mont h(Jun e 1972 ) sho w tha t drainag e water s fro mthi s urba n portio n containe da n averag e tota l lea dconcentratio n o f 69. 5 /xg/liter , includin g 6. 3 /xg/lite r

o f solubl e lead . Th e rura l portio n yielde da n averag e o f lea dconcentratio n o f 7. 4 /xg/lite r o f drainag e water , includin g 2. 1 /xg/lite r o f solubl e lead . Th e majo r

sourc e o f

lea dcontaminatio n o f

drink

in g wate r

i s th e wate r

suppl y syste mitself . Wate r tha t i s corrosiv e can leac hconsiderabl e amount s o f lea dfro mlea dplumbin g an dlea dcompound s use d t o joi n pipe . Severa l widel y adopte dcodes , suc ha s th e ASA-A4 0 Code , Unifor mPlumbin g Code , an d BOC A Code , allo w th e us e o f lea dpip e an dlis t

lea d a s a n acceptabl e solderin g materia l fo r joinin g pipe s tha t conve y water . Lea dpip e i s currentl y in us e in man y part s o f

th e Unite dState s fo r

wate r servic e line s an dinterio r

plumbing , particularl y in olde r ur ba n areas . I n acommunit y wate r suppl y surve y o f 96 9 wate r

system s conducte din nin e geographicall y distribute darea s o f

th e Unite dState s in 196 9 an d 1970 , i t wa s foun dtha t

1.4 percen t

o f al l ta p wate r sample s exceede dth e 5 0 /xg/lite r standard. 5 2 Th e maximu mconcentratio n foun dwa s 64 0 /xg/lite r tota l lead . Th e occurrenc e o f sample s exceedin g th e standar dwa s mor e prevalen t in water s witha relativel y lo w p H an dlo w specifi c conductance . I t wa s estimate dtha t

2 percen t

o f th e surve y popula

tio n o f 18. 2 millio n wa s expose dt o hig hlea dlevel s at th e tap . He man dDurum 5 3 discus s th e solubilit y o f thos e specie s o f

lea dtha t

ma y b e presen t

in drinkin g wate r an dsugges t

tha t th e solutio n o f

lea dfro menviron

menta l source s ma y b e an importan t contributio n i n certai n areas , dependin g o n th e chemica l composi

tio n ofth e runof

f water . Abov e p H 8.0 , th e solubilit y o f lea di s belo w 1 0 /xg/liter , regardles s o f th e alkalinit y o f

th e water . I n water s nea r p H 6. 5 witha lo w alkalinity , however , th e solubilit y o f lea dcoul d approac ho r

excee d10 0 /xg/liter . Lazru s e t al. 5 4 determine dth e lea dconten t o f precipitatio n at

3 2 point s in th e Unite dState s fo r aperio do f

6 month s in 196 6 an d1967 . The y reporte da n averag e lea d concentratio n o f

3 4 /xg/lite r

afte r filterin g th e sam 7-1 1P. 4

pies . Sample s o f

rainfal l at

Menl o Park , Calif. , dur

in g 197 1 showe dawid e rang e o f lea dconcentra tions , fro mafew /xg/lite r t o mor e tha n 10 0 /xg/liter. 5 3 He man dDurum 5 3 hypothesiz e tha t high

e r lea dconcentration s shoul db e anticipate din runof f wate r an dimpounde dra w wate r supplie s in th e Northeast , certai n urba n area s ofth e South , an d alon g th e Pacifi c Coas t becaus e o f

lo w p H an d alkalinit y i n waters . However , in muc hofth e res t o f th e Unite dStates , lea dfallou t rate s an dth e chemica l compositio n o f

th e runof

t (p H >8 ; alkalinit y > 10 0 mg/liter ) woul dminimiz e th e problem . Informatio n t o tes t thei r hypothesi s i s limite dat present . O f

th e few survey s o f

surfac e water s tha t

hav e bee n con ducted , mos t

wer e no t

don e afte r

period s o f

heav y rainfall , an dth e survey s tha t hav e bee n don e hav e measure ddissolve drathe r tha n tota l lead . Durum 4 8 measure dlea da t

70 0 lak e an drive r

site s in th e Unite dStates . Thes e measurement s wer e primaril y singl e sample s take n a t time s o f

relativel y lo w strea mflow s i n Octobe r an dNovembe r

1970 . Detectabl e concentration s o f dissolve dlea d(> 1 /xg/liter ) wer e foun di n 6 3 percen t o f th e samples , bu t onl y thre e sample s containe dmor e tha n 5 0 /xg/liter . A larg e proportio n o f th e sample s fo r

th e northeaster n an dsoutheaster n state s containe dlea d abov e th e detectio n limit , an dquit e afew ofth e sam ple s showe dlevel s abov e 1 0 /xg/liter . Thi s regiona l distributio n o t

lea din strea mwate r

i s i n accor dwith th e ide atha t

wate r compositio n in th e easter n state s i s mor e commonl y favorabl e fo r solutio n o f

lead . A substantia l numbe r

o f sample s fro msouther n Californi awer e hig hi n lead , an dthese , influence d th e dat afro mth e southwester n states . Kop p an d Kroner 5 5 presente ddat ao n dissolve dlea di n river s an dlake s o f

th e Unite dStates . Th e dat awer e gathere dove r

a5-yea r

perio d(196 2 t o 1967 ) an d represen t mor e tha n 150 0 samples . A detectabl e concentratio n o f

dissolve dlea dwa s foun di n 305 , o r 19. 3 percen t

o f th e samples ; th e observe dvalue s range dfro m2 t o 140 /xg/liter . Th e highes t con centratio n wa s detecte do n th e Ohi o Rive r a t Evansville , Indiana . Twenty-seve n o f thei r sample s exceede d5 0 /xg/liter . Observe dmea n observation s o f >3 0 /xg/lite r

dissolve dlea dwer e foun din th e followin g rive r

basins : Ohio , Lak e Erie , Uppe r Mississippi , Missouri , Lowe r Mississippi , an dCol

orado . 7. 5 OCCUPATIONA L EXPOSURE S Th e highes t

an dmos t

prolonge dexposure s t o lea d ar e foun damon g worker s i n th e lea dsmelting , refin

ing , an dmanufacturin g industries. 5 6 I n th e wor k areas , th e majo r rout e o f lea dexposur e i s b y inhala

tio n an dingestio n o f

bot hlead-bearin g dust s an d fumes . Airborn e dust s settl e ou t fro mth e ai r

ont o food , water , th e workers ' clothing , an dothe r object s an dar e the n transferre dt o th e mout hin on e fashio n o r another . Therefore , goo dhousekeepin g and , abov e all , goo dventilatio n hav e astron g impac t o n exposure . Exposur e level s hav e bee n foun dt o b e quit e hig hin on e factor y an dquit e lo w in anothe r solel y becaus e o f

difference s in ventilatio n engineer

in g o r housekeepin g practice s an dworke r education . 7.5. 1 Exposure s i n Lea d Mining , Smelting , an d Refinin g Th e greates t

potentia l fo r

high-leve l exposur e ex ist s in th e proces s o f

lea dsmeltin g an drefining. 5 6 Th e mos t

hazardou s operation s ar e thos e in whic h molte n lea dan dlea dalloy s ar e brough t t o hig htem peratures , resultin g in th e vaporizatio n o f lead . Thi s i s becaus e condense dlea dvapo r o r fum e has , t o a substantia l degree , asmal l (respirable ) particl e siz e range . Thu s althoug hth e tota l ai r lea dconcentra tio n ma y b e greate r

in th e vicinit y o f

ore-proportion

in g bin s tha n i t

i s in th e vicinit y o f

ablas t furnac e i n a primar y smelter , th e amoun t o f particl e mas s in th e respirabl e siz e rang e may b e muc hgreate r nea r th e furnace . A measur e o f

th e potentia l lea dexposur e in pri

mar y smelter s wa s obtaine din astud y o f thre e typi

ca l installation s in Utah. 5 6 Ai r lea dconcentration s nea r al l majo r

operations , a s determine dusin g per sona l monitor s wor n b y th e workers , wer e foun dt o var y fro mabou t

10 0 t o mor e tha n 400 0 /xg/m 3

. Ob

viously , th e hazar dt o thes e worker s woul db e ex tremel y seriou s wer e i t

no t fo r th e fac t tha t th e us e o f respirator s i s mandator y in thes e particula r smelters . Althoug hther e ar e n o comparabl e dat ato r ex posure s in secondar y smelters , whic har e foun di n o r nea r mos t larg e cities , th e natur e ofthei r operatio n i s simila r t o tha t o f primar y smelter s excep t tha t n o ore-processin g i s involved , sinc e secondar y smelter s depen do n th e loca l suppl y o f lea dscra p i n th e for m o f discarde delectri c storag e batteries , cabl e casings , pipes , an dothe r

material s fo r

thei r suppl y o f

lead . Consequently , th e exposur e hazar dt o worker s i n secondar y smelter s i s probabl y simila r t o tha t foun d in th e primar y smelte r study . Hundreds , perhap s thousands , o f

th e smal l scra p dealer s tha t suppl y thes e secondar y smelter s hav e thei r ow n neighbor

hoo do r eve n backyar dmeltin g operation s fo r ex tractin g an dreclaimin g lead . Thes e operation s ca n contribut e substantiall y t o loca l airborn e lea d levels . 7-1 2P. 5

Hig hlevel s o f

atmospheri c lea dar e als o foun din foundrie s in whic hmolte n lea di s alloye dwithothe r metals . Ber g an dZenz 5 7 foun din on e suc hoperatio n tha t averag e concentration s o f lea din variou s wor k area s wer e 28 0 t o 60 0 /xg/m 3

. Thes e level s wer e sub

sequentl y reduce dt o 3 0 t o 4 0 /xg/m 3 wit hth e in

stallatio n o f

force dventilatio n system s t o exhaus t th e wor k are aatmosphere s t o th e outside . Exposure s fo r

worker s involve di n lea dminin g depen dt o som e exten t

o n th e solubilit y ofth e lea d fro mth e ores . Th e lea dsulfid e (PbS ) in galen ai s in

soluble , an dabsorptio n throug hth e lun g ma y b e slight . I t i s no t reall y know n ho w readil y absorptio n take s place . I n th e stomach , however , som e lea d sulfid e ma y b e converte dt o slightl y solubl e lea d chloride , whic hmay the n b e absorbe din moderat e amounts . 7.5. 2 Exposure s i n Weldin g an d Shipbreakin g Whe n metal s tha t

contai n lea do r

ar e protecte d wit halead-containin g coatin g (pain t o r plating ) ar e heate din th e proces s o f weldin g o r

cutting , copiou s quantitie s o f

lea dparticle s in th e respirabl e siz e rang e ar e emitte dint o th e air . Unde r condition s o f poo r ventilation , electri c ar c weldin g o f zin c sili

cate-coate dstee l (determine dt o contai n som e 2 9 mg Pb/in 2 o f

coating ) produce dbreathing-zon e con centration s oflea dreachin g 15,00 0 /xg/m 3 , far i n ex ces s o f 45 0 /xg/m 3 , th e curren t occupationa l short

ter mexposur e limi t

(STEL ) in th e Unite dStates. 5 8 Unde r goo dventilatio n conditions , aconcentratio n o f 140/xg/m 3 wa s measured. 5 9 I n astud y o f

salvag e worker s usin g oxy-acetylen e cuttin g torche s o n lead-painte dstructura l stee l unde r condition s o f

goo dventilation , breathing

zon e concentration s o f lea daverage d120 0 /xg/m 3 an drange da s hig ha s 240 0 /xg/m 3

. 6 0 7.5. 3 Exposure s i n th e Electri cStorag e Batter y In dustr y A t al l stage s in batter y manufactur e excep t fo r fina l assembl y an dfinishing , worker s ar e expose dt o hig hai r lea dconcentrations , particularl y lea doxid e dust . Ai r lea dconcentration s a s hig ha s 540 0 /xg/m 3 hav e bee n recorde din som e studies. 5 6 Th e hazar din plat e casting , whic hi s amolten-meta l operation , i s fro mth e spillag e o f

dross , resultin g in dust y floors . Durin g oxid e mixing , whic hi s probabl y th e mos t hazardou s occupation , ventilatio n i s neede dwhe n th e mi x i s loade dwithlea doxid e powder , an dfre

quen t cleanu p i s necessar y t o preven t th e accumula

tio n o f dust . I n th e pastin g ofth e plates , whethe r b y han do r machine , th e dange r

agai n i s fro mdus t whic haccumulate s a s th e past e dries . Als o th e form

in g an dstackin g processe s ar e dusty , an dventilatio n i s neede dther e also . Th e dat acite dar e sufficientl y alarmin g t o sugges t

tha t respirator s mus t

b e wor n in mos t o f thes e operations . 7.5. 4 Exposure s i n th e Printin g Industr y I n aprintin g establishment , th e exposur e t o lea di s probabl y in direc t

proportio n t o th e dispersio n o f lea doxid e dust , secondar y t o th e remel t operation . Brand t an dReichenbach 6 1 hav e reporte do n a194 3 stud y in whic hmeltin g pot s wer e locate di n avariet y o f place s wher e use dtyp e wa s discarded . Th e pot s wer e maintaine da t

temperature s rangin g fro m268 ° t o 446°C . Th e highes t ai r lea dconcentratio n recorde dwa s 57 0 /xg/m 3

. Sinc e thi s repor t wa s published , workin g method s an dindustria l hygien e condition s hav e change dconsiderably ; bu t a margina l degre e o f

hazar dstil l prevails . I n 1960 , Tsuchiy aan dHarashima 6 2 foun din severa l printin g shop s in Japa n lea dlevel s o f 3 0 t o 36 0 /xg/m 3 at breathin g level . 7.5. 5 Exposure s i n Alky l Lea d Manufactur e Worker s involve di n th e manufactur e o f bot h tetraethy l lea dan dtetramethy l lead , tw o alky l lea d compounds , ar e expose dt o bot hinorgani c an dalky l lead . Som e exposur e als o occur s a t th e petroleu m refinerie s wher e th e tw o compound s ar e blende d int o gasoline , bu t

n o exposur e dat aar e availabl e o n thes e blenders . Th e majo r

potentia l hazar din th e manufacturin g o f tetraethy l lea dan dtetramethy l lea di s fro mski n absorption , bu t

thi s i s guarde dagains t b y th e us e o f protectiv e clothing . Linc he t al. 6 3 foun dacorrela

tio n betwee n a n inde x o f organi c plu s inorgani c ai r lea dconcentration s in aplan t an dth e rat e o f

lea d excretio n i n th e urin e o f th e workers . Th e averag e concentratio n o f

organi c lea di n th e urin e wa s 0.17 9 mg/m 3 fo r

worker s in th e tetramethy l lea doperatio n an d0.12 0 mg/m 3 fo r

worker s in th e tetraethy l lea d operation . Th e tetramethy l lea dreadin g wa s proba

bly highe r

becaus e th e reactio n betwee n th e organi c reagen t an dlea dallo y take s plac e at asomewha t highe r temperatur e an dpressur e tha n tha t employe d in tetraethy l lea dproduction . 7.5. 6 Exposure s i n Othe rOccupation s I n bot hth e rubbe r

product s industr y an dth e plastic s industr y ther e ar e potentiall y hig hexposur e level s t o lead . Th e potentia l hazar dofth e us e o f lea d stearat e a s astabilize r

in th e manufactur e o f poly

viny l chlorid e wa s note di n th e 197 1 Annua l Re

7-1 3P. 6

por t o f th e Britis hChie f

Inspecto r

o f Factories. 6 4 Th e Inspecto r

state dtha t

th e numbe r

o f reporte d case s o f lea dpoisonin g in th e plastic s industr y wa s secon donl y t o tha t

in th e lea dsmeltin g industry . Scarlat o e t

al. 6 5 an dMaljkovic 6 6 hav e reporte do n othe r individua l case s o f

exposure . Th e sourc e ofth e proble mi s th e dus t

tha t i s generate dwhe n th e lea d stearat e i s mille dan dmixe dwithth e polyviny l chlorid e an dth e plasticizer . Sakura i e t

al. 6 7 in astud y o f

bioindicator s o f

lea d exposure , foun dambien t ai r concentration s averag in g 5 8 /xg/m 3 in th e lea dcoverin g departmen t o f a rubbe r hos e manufacturin g plant . Unfortunately , n o ambien t ai r measurement s wer e take n fo r th e othe r department s o r

th e contro l group . 7.5. 7 Exposure s Resultin g fro m Manmad e Material s A t leas t tw o manmad e material s i n widesprea dus e ar e know n t o contai n lead : pain t an dplastics . I n 1974 , th e Consume r Produc t Safety Commis

sio n collecte dselecte dhousehol dpain t sample s an d analyze dthe mfo r

lea dcontent. 68 Analysi s o f 48 9 sample s showe dtha t

8 percen t

of oil-base dpaint s an d1 percen t

o f water-base dpaint s containe d greate r tha n 0. 5 percen t

lea d(500 0 /xg Pb/ g paint , base do n drie dsolids) , whic hwa s th e statutor y limi t at th e tim e o f

th e study . Th e curren t statutor y limi t for Federa l constructio n i s 0.0 6 percent . Thi s limi t i s equivalen t

t o 60 0 /xg Pb/ g paint. 6 8 Ol dpain t tha t i s stil l o n building s will continu e t o pos e apotentia l hazar dfo r

som e time . I t

ca n becom e accessibl e throug hflaking , eve n thoug hpainte dove r withnon toxi c paints . Lea di n pain t

constitute s apotentia l healt hprob

lemprimaril y fo r

childre n withpic awh o ma y habituall y inges t

1 t o 3 g (o r

more ) o f

pain t pe r week. 6 8 Plastic s contai n anumbe r o f heav y metal s tha t

ar e constituent s o f

organometalli c stabilizer s adde d durin g manufacture . Th e mos t commonl y use dlead

containin g stabilize r

i s dibasi c lea dstearate , i n amount s rangin g fro m0. 5 t o 2. 0 part s pe r 100 part s o f resin. 6 9 Thi s stabilize r i s normall y use din rigi d PV C products . Diffusion , o r leachin g b y solvents , i s estimate dt o b e quit e slo w —o n th e orde r o f 10-' ° t o 10 -1 2 cm 2 /se c at

roo mtemperatur e —bu t n o defini

tiv e informatio n i s available . Incineratio n o f

lead-containin g plastic s ma y becom e a n increasingl y significan t sourc e o f localize dlea dpollution . I t ha s bee n estimate dtha t in th e yea r

2000 , fo r

example , ther e coul db e ap proximatel y 2.5 4 time s IO 9 kg o f PV C plasti c wast e t o b e dispose do f annually , o f

whic habou t

0.5 9 time s IO 9 kg woul dprobabl y b e incinerated. 7 0 Assumin g tha t

lea dwill b e emitte dfro mth e un controlle dincineratio n o f PVC' s at

th e rat e o f

0. 2 g Pb/k g o f waste 7 1 ( afigur e applyin g t o al l soli d waste) , abou t

1. 2 time s 10 5 kg o f

lea dcoul db e release dpe r

year . Thi s woul db e a n increas e o f mor e tha n fourteenfol dove r

th e estimat e fo r

1975 . Sinc e th e greate r

par t o f th e lea din thes e incinerate d plasti c waste s wil l remai n in th e ash , electrostati c precipitator s ca n substantiall y decreas e th e emitte d fractio n (t o a n estimate d0.0 3 g/kg) . Bu t thi s proces s onl y aggravate s th e difficultie s o f residua l soli d wast e disposa l wit hit s attendan t problem s o f

fugi

tiv e dus t an dth e potentia l contaminatio n o f soil , surfac e waters , an dgroundwater s throug hleachin g fro mlandfil l operations . Lea di s presen t

i n othe r product s tha t

ma y con stitut e source s o f

lea dexposur e whe n use do r dis

pose dof . Lea dmay b e foun din colo r newsprint , craf t an dhobb y materials , toothpast e tubes , cos meti c products , candl e wicks , pewte r an dsilve r hollowware , painte dutensils , an ddecal s o n glassware . Fo r

example , lea din th e pain t o n handle s o f kitche n utensil s ha s bee n foun db y Hanki n e t al. 7 2 t o rang e fro m0 t o 9. 7 percen t ( 0 t o 97,00 0 ppm) . Mor e tha n hal f

th e pain t

sample s (1 3 o f

21 ) ex ceede dth e allowabl e limi t fo r painte dtoys , whic hi s 0.0 6 percent . 7.5. 8 Historica l Change s Perhap s th e mos t

impressiv e dat ao n th e mag nitud e o f environmenta l contaminatio n b y lea dan d it s increas e ove r

tim e ar e t o b e foun di n asmal l grou p o f recen t historica l studie s tha t examine d level s ofth e meta l in pola r sno w an dic e (Chapte r

6) . O f particula r

interes t wa s th e 200-fol dincreas e in lea dlevel s ove r

severa l centurie s foun db y Murozum i e t

al. 7 3 in th e interio r

o f norther n Green

land , an dth e 10-fol dincreas e throug hth e las t cen tur y o f ic e layer s reporte db y Jaworowski 7 4 in a stud y o f tw o Polis hglaciers . Thes e finding s paralle l th e result s o f

astud y b y Ruhlin g an dTyler, 7 5 whic h indicate da n approximat e fourfol dincreas e in lea d conten t in Swedis hmos s sample s take n fro mth e perio d189 0 t o th e present . Thes e historica l record s reflec t th e increasin g distributio n o f lea dcause db y man . 7. 6 REFERENCE S FO RCHAPTE R7 1 . Akiand . G . G . Ai rQuality Dat afo rMetals . 197 0 throug h 1974 . from th e Nationa l Ai rSurveillanc e Networks . U.S . Environmenta l Protectio n Agency . Offic e o f Researc h and Development , Researc h Triangl e Park , N.C . Pub . No . EP A 600/4-76-041 . 1976 . 15 4 p . 7-1 4P. 7

2 . Shearer , S . D. , G . G . Akiand , D . H . Fair , T . B . McMullen . an dE . C . Tabor . Concentration s o f particulat e lea di n th e ambien t ai r ofth e Unite dStates . Pape r presente dat

Publi c Hearin g o n Gasolin e Lea dAdditive s Regulations . Lo s Angeles . Ma y 2-4 , 1972 . 3 . Faoro , R . B. . an dT . B . McMullen . Nationa l Trend s in Trac e Metal s i n Ambien t Air , 1965-1974 . U.S . Environ

menta l Protectio n Agency , Offic e o f Ai r Qualit y Plannin g an dStandards , Researc hTriangl e Park , N.C . Pub . No . EPA-450/1-77-003 . 1977.4 1 p . 4 . Moto r

Gasolines . U.S . Energ y Researc han dDevelopmen t Administration , Bartlesvill e Energ y Researc hCenter . Bartlesville , Oklahoma . 5 . Lee . R . E. . S . S . Goranson , R . E . Enrione , an dG . B . Morgan . Th e NAS N cascad e impacto r network . Par t

11 . Siz e distributio n measurement s o f trace-meta l compo nents . Environ . Sci . Tech . 6( 1 2):1025-1030 , 1972 . 6 . Darrow , D . K . an dH . A . Schroeder . Childhoo dexposur e t o environmenta l lead . Presente dat America n Chemica l Societ y Nationa l Meeting , Chicago , III. . Augus t 29 . 1973 . 7 . Edwards , H . W . Environmenta l contaminatio n b y automotiv e lead . In: Inter . Symp . Proc . o n Recen t Ad

vance s i n th e Assessmen t ofth e Healt hEffect s o f Environ

menta l Pollution , Vol . III . Paris . Jun e 1974 . Luxembourg . Commissio n o f

th e Europea n Communities . 1975 . p . 1277-1286 . 8 . Barltrop , D. . an dC . D . Strelow . Westwa y Nurser y Testin g Project . Repor t

t o th e Greate r

Londo n Council . Augus t 1976 . 9 . PedCo-Environmental , Inc . Lea dAnalysi s fo r Kansa s Cit y an dCincinnati . Repor t t o U.S . Environmenta l Protectio n Agency . Researc hTri-Park . N.C . PN3264-E . Marc h1977 . 10 . Secon dAnnua l Catalys t Researc hProgra mReport : Sup

plemen t II . U.S . Environmenta l Protectio n Agency , Offic e o f Researc han dDevelopment . Researc hTriangl e Park . N.C . 1977 . p . 359-466 . I 1 . Harrison , R . M. . R . Perry , an dD . H . Slater . Th e contribu

tio n o f organi c lea dcompound s t o tota l lea dlevel s i n ur ba n atmospheres . In: Proc . Inter . Symp . o n Recen t Ad

vance s i n th e Assessmen t ofth e Healt hEffect s o f Environ

menta l Pollution , Vol . III . Paris , Jun e 24-28 . 1974 . Lux

embourg , Commissio n o f th e Europea n Communities . 1975 . p . 1783-1788 . 12 . Fritsch , A . an dM . Prival . Respons e t o th e Unite dState s Environmenta l Protectio n Agency' s notic e fo r additiona l healt heffect s informatio n concernin g th e us e o f leade d gasoline . Cente r

fo r Scienc e i n th e Publi c Interest . Wash

ington , D.C . 1972 . 1 1 p . 1 3 . Kennedy , G . L. , Jr . Bloo dan dTissu e Lea dConten t Stud y Followin g Exposur e o f Mal e Albin o Rat s t o Lead-Con

tainin g Expresswa y Dirt , Neighborhoo dStree t Dirt , Lea d Acetate , o r

Lea dOxide . Industria l Bio-Tes t Laboratories . Northbrook , Illinois . Researc hRepor t IB T No . E1733C . 1973 . 1 6 p . 14 . Lombardo , L . V . Th e Publi c Interes t Campaign , Washing

ton , D.C . Persona l Communicatio n t o Mr . Wm . D . Ruckelshaus , Administrator , Unite dState s Environmenta l Protectio n Agency . Marc h9 , 1973 . 15 . Pinkerton.C.J . P . Creason . D . I . Hammer , an dA . V . Col

ucci . Multimedi aIndice s o f Environmenta l Trac e Meta l Exposur e i n Humans . In: Proc . 2n dInter . Symp . o n Trace

Elemen t Metabolis mi n Animals , Vol . 2 . Madison , Wis . 1973 . p . 465-469 . 16 . Te r Haar , G. . an dR . Aronow . Ne w informatio n an dlea d i n dir t an ddus t

a s relate dt o th e childhoo dlea dproblem . Environ . Hlth . Persp . 7:83-90 , 1974 . 17 . Shapiro . I . M. . H.'L . Needleman , B . Dobkin , an dO . C . Tuncay . Lea dlevel s i n dentur e an dcircumpulpa l dentin e o f deciduou s teet ho f

norma l an dlea dexpose dchildren . Clin . Chem . Acta . 46(2):\ 19-123 . 1973 . • 18 . Positio n o n th e Healt hImplication s o f Airborn e Lead . U.S . Environmenta l Protectio n Agency , Offic e o f Healt h an dEcologica l Effects , Washington , D.C . Nationa l Tech

nica l Informatio n Service , Springfield , Va . Pub . No . NTI S P B 22 8 594/8 . 1973 . 19 . Rameau , J . T . Lea da s an environmenta l pollutant . In: Proc . Inter . Symp . o n Environmenta l Healt hAspect s o f Lead . Amsterdam , Octobe r 1972 . Luxembourg , Commis

sio n ofth e Europea n Communities . 1973 . p . 189-200 . 20 . Lead : Airborn e Lea di n Perspective . Nationa l Academ y o f Sciences , Washington , D.C . 1972 . p . 29 . 21 . Needleman , H . L . an dJ . Scanlon . Gettin g th e lea dout . Ne w Eng . J . Med . 288(9):466-467 , 1973 . 22 . Landrigan , P . J. , S . H . Gehlbach , B . F . Rosenblum , J . M . Shoults , R . M . Candelaria , W . F . Barthel , J . A . Liddle . A . L . Smrek . N . W . Staehling , an dJ . D . F . Sanders . Epidemi c lea dabsorptio n nea r

a n or e smelter : Th e rol e o f particu

lat e lead . Ne w Eng . J . Med . 292(3): 1 23-129 , 1975 . 23 . Needleman . H . L. . I . Davidson , E . M . Sewell . an dI . M . Shapiro . Subclinica l lea dexposur e i n Philadelphi aschoo l children : Identificatio n b y dentin e lea danalysis . Ne w Eng . J . Med . 290(5):245-248 , 1974 . 24 . Yankel , A . J. . I . H . vo n Lindern . an dS . P . Walter . Th e Silve r Valle y lea dstudy : Th e relationshi p betwee n child

hoo dbloo dlea dlevel s an denvironmenta l exposure . J . Ai r Poll . Contr . Assoc . 27(8):763-767 . 1977 . 25 . Landrigan , P . J. . E . L . Baker , R . G . Feldman , D . H . Cox , K . V.Eden , W . A . Orenstein , J . A . Mather , A . J . Yankel , an dI . H . vo n Lindern . Increase dlea dabsorptio n wit h anemi aan dslowe dnerv e conductio n i n childre n nea r a lea dsmelter . J . Pediatrics . 89(6):904-9l0 . Dec . 1976 . 26 . Schroeder , H . A . an dI . H . Tipton . Th e huma n bod y burde n oflead . Arch . Environ . Healt h7 7:965-978 , 1968 . 27 . Rabinowitz . M . B . Lea dContaminatio n ofth e Biospher e b y Huma n Activity . Ph.D . Dissertation , Universit y o f Californi aat

Lo s Angeles . 1974 . 28 . Motto , H . L „ R . H . Daines , D . H . Chilko , an dC . K . Mot

to . Lea di n soil s an dplants : It s relationshi p t o traffi c volum e an dproximit y t o highways . Environ . Sci . Technol . 4(3):231-238 , 1970 . 29 . Schuck , E . A . an dJ . K . Locke . Relationshi p o f automotiv e lea dparticulate s t o certai n consume r crops . Environ . Sci . Technol . 4(4):324-330 , 1970 . 30 . Welch , W . R . an dD . L . Dick . Lea dconcentration s i n tissue s o f

roadsid e mice . Environ . Pollut . 8:15-21 , 1975 . 31 . Dedolph , R..G . Te r Haar , R . Holtzman , an dH . Lucas , Jr . Source s o f

lea di n perennia l ryegras s an dradishes . En

viron . Sci . Technol . 4(3):217-223 , 1970 . 32 . Te r Haar , G . Ai r

a s asourc e o f

lea di n edibl e crops . En

viron . Sci . Technol . 4(3):226-229 , 1970 . 33 . Arvik , J . H . Factor s Affectin g Uptak e o f Lea db y Plants . Ph.D . Dissertation , Colorad o Stat e Univ. , For t Collins , Colo . 1973 . 34 . Kolbye , A . C . K . R . Mahaffey , J . A . Fiorino , P . C . Cor

neliussen , an dC . F . Jelinek . Foo dexposur e t o lead . En

viron . Healt hPersp . 7:65-74 , 1974 . 

### 7-1 5P. 8

35 . Schroeder , H . A . an dJ . J . Balassa . Abnorma l trac e metal s i n man : Lead . J . Chron . Dis . /4(4):408-425 , 1961 . 36 . Surve y o f

Lea di n Food . (Secon dReport) . Appendi x IV . Ministr y o f

Agriculture , Fisherie s an dFood . He r Ma

jesty' s Stationer y Office , London . 1972 . 37 . Complianc e Progra mEvaluation , FY-1974 , Heav y Metal s i n Food s Survey . U.S . Foo dan dDru g Administration , Burea u o f

Foods . Washington . D.C . 1975 . 9 9 p . 38 . Tolan , A. , an dG . A . H . Elton . Lea dintak e fro mfood . In: Proc . Inter . Symp . o n Environmenta l Healt hAspect s o f Lead . Amsterdam , Octobe r 1972 . Commissio n o f th e Europea n Communities , Luxembourg . 1973 . p . 77-84 . 39 . Michell , D . G . an dK . M . Aldous . Lea dconten t o f foodstuffs . Env . Hlth . Pers . 7:59-64 , Ma y 1974 . 40 . Hankin , L. . G . H . Heichel , an dR . A . Botsford . Lea dcon ten t o f pe t foods . Bull . Environ . Contamin . an dToxicol . /5(5):630-632 . 1975 . 41 . Ziegler . E . E. , B . B . Edwards , R . L . Jensen . K . R . Mahaffey , an dS . D . Fomon . Absorptio n an dretentio n o f lea db y infants . (I n press. ) Pediatri c Research . 42 . Hankin . L. . G . H . Heichel , an dR . A . Botsford . Lea do n wrapper s o f

specialt y food s a s apotentia l hazar dfo r children . Clinica l Pediatrics . /5(12):1064-I065 . 1974 . 43 . Block , J . L . Th e acciden t tha t save dfiv e lives . Goo d Housekeeping , Novembe r 1969 . 44 . Klein . M. , R . Namer , E . Harpur . an dR . Corbin . Earthen

war e container s a s asourc e o f fata l lea dpoisoning . Ne w Englan dJ . Med . 283( 13):669-672 . 1970 . 45 . Harris . R . W . an dW . R . Elsen . Cerami c glaz e a s asourc e o f lea dpoisoning . J . Am . Med . Assoc . 202(6):208-210 . 1967 . 46 . Zurlo , N . an dA . M . Griffini . Lea dcontent s i n foo dan d beverage s consume di n Milan . In: Proc . Inter . Symp . o n Environmenta l Healt hAspect s o f Lead , Amsterdam , Oct . 1972 . Luxembourg , Commissio n o f th e Europea n Com

munities . 1973 . p . 93-98 . 47 . Boudene , C . F . Arsac , an dJ . Meininger . Stud y ofai r an d populatio n lea dlevel s i n France . Arch . Hig . Rada . Tekisol . 26(Suppl.):179-189 , 1975 . 48 . Durum , W . H . Reconnaissanc e o f Selecte dMino r

Ele

ment s i n Surfac e Water s o f th e U.S . U.S . Dept . o f

Interior . Geologi c Survey , Washington , D.C . USG S Circula r No . 643 . 1971 . 49 . Durfor.C . N. , an dE . Becker . Publi c Wate r Supplie s o f

th e 10 0 Larges t

Citie s i n th e Unite dStates , 1962 . U.S . Dept . o f Interior , Geologi c Survey , Washington , D.C . USG S Wate r Suppl y Pape r

No . 1812 . 1964 . 36 4 p . 50 . Chemica l Analysi s o f Interstat e Carrie r

Wate r Suppl y Systems . U.S . Environmenta l Protectio n Agency . Researc h Triangl e Park , N.C . Pub . No . EP A 430/9-75-005 . 1975 . 8 8 P51 . Rolfe , G . L . an dA . Haney . A n Ecosyste mAnalysi s o f En

vironmenta l Contaminatio n b y Lead . Inst , fo r Env . Studies , U . o f

Illinois , a t

Urbana-Champaign , III . Res . Rept . No . 1 . 1975 . p . 22-34 . 52 . McCabe , L . J . e t

al . Surve y o f

communit y wate r

suppl y systems . J . Amer . Wate r Work s Assn . 62(11):670 , 1'970 . 53 . Hem , J . D . an dW . H . Durum . Solubilit y an doccurrenc e o f lea din surfac e water . J . Amer . Wate r Work s Assn . 65(8):562-568 , 1973 . 54 . Lazrus , A . L. , E . Lorange , an dJ . P . Lodge , Jr . Lea dan d othe r meta l ion s i n U.S . precipitation . Environ . Sci . Tech . 4(l):55-58 , 1970 . 55 . Kopp , J . F . an dR . C . Kroner . Trac e Metal s in Water s o f th e Unite dStates ; A Five-Yea r Summar y o f

Trac e Metal s i n River s an dLake s ofth e Untie dState s (Oct . 1 , 196 2 - Sept . 30 , 1967) . U.S . Dept . o f Interior , Federa l Wate r Pollutio n Contro l Administration , Cincinnati , Ohio . 1967 . 21 8 p . 56 . Environmenta l Healt hCriteria . Vol . 3. , Lead . Unite dNa

tion s Environmen t

Program/Worl dHealt hOrganization , Geneva . Switzerland . 1977 . p . 59-65 . 57 . Berg , B . A. , an dC . Zenz . Environmenta l an dclinica l con tro l o f lea dexposur e i

n anonferrou s foundry . J . Amer . Ind . Hyg . Assoc . 28(2) : 175-178 , 1967 . 58 . Pegues . W . L . Lea dfum e fro mweldin g o n galvanize dan d zinc-silicat e coate dsteels . J . Amer . Ind . Hyg . Assoc . 2/(3):252-255,1960 . 59 . Tabershaw , I . R. . B . P . W . Ruotolo , an dR . P . Gleason . Plumbis mresultin g fro moxyacetylen e cuttin g o f painte d structura l steel . J . Ind . Hyg . Toxicol . 25(5) : 189-191 . 1943 . 60 . Rieke , F . E . Lea dintoxicatio n in shipbuildin g an d shipscrapping , 1941-1968 . Arch . Env . Health . 79:521-539 , 1969 . 61 . Brandt . A . D . an dG . S . Reichenbach . Lea dexposure s at th e governmen t

printin g office . J . Ind . Hyg . Toxicol . 25 ( 10):445-450 . 1943 . 62 . Tsuchiya , K . an dS . Harashima . Lea dexposur e an dth e derivatio n o f

maximu mallowabl e concentration s an d threshol dlimi t

values . Brit . J . Ind . Med . 22(3):181-186 , 1965 . 63 . Linch , A . L. , E . G . Wiest , an dM . D . Carter . Evaluatio n o f tetraalky l lea dexposur e b y persona l monito r surveys . J . Amer . Ind . Hyg . Assoc . 3/(2):l70-179 , 1970 . 64 . H . M . Chie f

Insp . o f Factories . H . M . Grea t Britai n Dept . o f Employment . Annua l Report , 1971 . London , He r Ma

jesty' s Stationer y Office . 1972 . p . 60 , 95 . 65 . Scarlato . G. . S . Smirne . an dA . E . Poloni . L'encefalopati a satumin aacut adel l adulto . Act aNeurol . 24:578-580 . 1969 . 66 . Maljkovic , J . A cas e o f occupationa l poisonin g wit hlea d carbonat e an dstearate . Sigurnos t u Pogonu . 75:123-124 , 1971 . 67 . Sakurai . H. . M . Sugita , an dK . Tsuchiya . Biologica l respons e an dsubjectiv e symptom s i n lo w leve l lea dex posure . Arch . Env . Hlth . 29:157-163 , 1974 . 68 . Committe e o n Toxicology , Nationa l Researc hCouncil . Recommendation s fo r

th e Preventio n o f

Lea dPoisonin g i n Children . Consume r Produc t

Safety Commission , Washington . D.C . 1976 . p . 45 , 51 . 69 . Piver.W.T . Offic e o f Healt hHazar dAssessment , NIEHS , Persona l communicatio n t o H . L . Falk , Assoc . Dir . fo r Healt hHazar dAssessment , NIEHS . Researc hTriangl e Park , N.C . Januar y 10 , 1977 . 70 . Vaughn . D . A. . C . Ifeadi , R . A . Markle , an dH . H . Krause . Environmenta l Assessmen t o f Futur e Disposa l Method s fo r Plastic s i n Municipa l Soli dWaste . U.S . Environmenta l Protectio n Agency , Nationa l Environmenta l Researc h Center , Cincinnati , Ohio . Pub . No . EPA-670/2-75-058 . 1975 . 8 6 p . 71 . Contro l Technique s fo r Lea dAi r

Emissions . (Draf

t fina l report. ) U.S . Environmenta l Protectio n Agency , EP A Con

trac t No . 68-02-1375 , Cincinnati , Ohio . Octobe r 1976 . 42 4 p . 7-1 6P. 9

72 . Hankin , L. , G . H . Heichel , an d R . A . Botsford . Lea d o n painte d handle s o f kitche n utensils . Clin . Pediat . /5(7):635-636 , 1976 . 73 . Murozumi , M. , T . J . Chow , an d C . C . Patterson . Chemica l concentration s o f pollutan t lea d aerosols , terrestria l dusts , an d se a salt s i n Greenlan d an d Antarcti csnowstrata . Geochim . Cosmochim . Acta . (London) . 55:1247-1294 , 1969 . 74 . Jaworowski , Z . Stabl e lea d i n fossi l ic e an d bones . Nature . 2/7:152-153 . Januar

y13 , 1968 . 75 . Ruhling . A . an d G . Tyler . A n ecologica l approac h t o th e lea d problem . Bot . Notis . (Stockholme ) /2/:32l-342 , 1968 .

7-1 7P.1 0



## 8 . EFFECT S O F LEA D O N ECOSYSTEM S

It ha s bee n substantiate dtha t lea di s anatura l constituen t

o f th e environment , bu t natural , back

groun dlevel s o f

lea din th e environmen t ar e no t know n wit han y degre e o f certainty . A s anatura l constituent , lea ddoe s no t usuall y pos e athrea t

t o th e organism s o f

natura l an dagroecosystems . However , th e widesprea dus e o f

lea di n avariet y o f

chemica l form s b y ma n ha s redistribute dth e natura l lea din th e environmen t

an dha s consequentl y increase dth e exposur e o f

th e bioti c component s o f ecosystem s t o unprecedente dlevel s o f lead . Concer n no w exist s abou t th e possibl e threa t

t o thes e bioti c component s becaus e ofthei r

inheren t

valu e t o ecosyste mstabilit y an dbecaus e ofth e ultimat e impac t tha t effect s o f

th e ecosyste mwoul dhav e o n man . Figur e 8- 1 depict s th e environmenta l flo w o f lea dan dth e possibl e ex posur e route s fo r

plant s an danimal s i n th e ecosystem. 1

FOO D PROCESSIN G

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OPERATION S

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# 3zm 

# :t £ WATE R SUPPLIES 

## h r >':*AN'IMALS" :

: ATMOSPHER E > I (LEA D AEROSOL: ; : AN D : ; : ORGANI C LEAD) >

OTHE R LEA D CONTAININ G PRODUCT

S AN D WASTE

S F4LLOU T

AN D RAINOU T OCEAN S 

## Z3Z I I - LAKE S AN D RIVERS; .

- » :;ESTUARIES ; Figur e 8-1 . Simplifie d ecologi c flo wchar t fo r lea d showin g principa l cyclin g pathway s an d compartments. 1 8 1 EFFECT S O N DOMESTI C ANIMALS , WILDLIFE , AN D AQUATI C ORGANISM S 8.1. 1 Domesti cAnimal s Lea dpoisoning , afrequen t caus e o f

accidenta l deat hin domesti c animal s for man y years, 2 usuall y result s fro mth e ingestio n o f lea do r lead-containin g material . Substance s tha t caus e lea dpoisonin g in

clud e lead-base dpaints , use dmoto r oil , discarde d oi l filters , storag e batteries , greases , putty , linoleum , an dol dpain t

pails . Animal s suc ha s cattle , dogs , an d cat s tha t hav e natura l lickin g an dchewin g habit s ar e particularl y susceptible . Horse s ar e no t usuall y poisone di n thi s manne r becaus e the y normall y d o no t lic k discarde dmaterials . Animal s grazin g in th e vicinit y o f

smelters , mines , an dindustria l plant s fro mwhic hlea dfume s and/o r dust s ar e bein g emit

te do r tha t ar e fe dvegetatio n harveste dfro msuc h area s may als o b e poisoned . Th e possibilit y o f animal s bein g poisone dfro mingestio n o f roadsid e pastur e contaminate db y mobil e source s i s o f con cern , bu t n o cas e o f

thi s typ e ha s bee n reporte din th e literature. 3 Breathin g o f

lea ddust s ca n b e anothe r wa y whereb y animal s ar e expose dt o lead , bu t poisonin g o f domesti c an dwil danimal s a s aresul t o f lea din

halatio n ha s no t

bee n substantiated . Incident s o f

lea dpoisonin g in cattl e an dhorse s cause db y emission s fro mstationar y source s hav e bee n reporte dfro mBenecia , Calif.; 3 Trail , B.C.; 2 Belleville , Penn.; 4 St . Paul , Minn.; 5 an dsouth

easter n Missouri. 6 Death s fro mlea dpoisonin g o f lamb s an dshee p i

n Britain 7 an do f

horses , sheep , an dgoat s in continenta l Europ e hav e bee n re ported. 8

- " Hammon dan dAronson 5 hav e estimate dtha t th e minima l cumulativ e letha l dos e o f lea dfo r aco w i s 6 t o 7 mg/k g o f

bod y weigh t

pe r day . The y stat e tha t thi s intak e represent s aconcentratio n o f abou t 30 0 pp min th e tota l diet . I n cattl e tha t consume dlead

contaminate dha y an dcor n silag e grow n in afiel d adjacen t t o asmelter , fata l lea dpoisonin g occurre d afte r approximatel y 2 months . I n anothe r study, 1 2 8- 1P.1 1

cattl e wer e fe dlea da t

th e rat e o f

5 t o 6 mg/k g pe r da y fo r aperio do f

2 year s withou t

th e appearanc e o f visibl e clinica l symptoms . A stee r fe dth e sam e die t fo r 3 3 months , however , showe dclinica l symptom s oflea dpoisonin g culminatin g in death. 1 3 Th e lengt h o f tim e require dfo r

th e appearanc e o f

over t clinica l symptom s o f

lea dpoisonin g i s in mos t instance s directl y relate dt o th e amoun t consume dpe r

uni t o f time . Horse s ar e mor e susceptibl e tha n cattl e t o poison

in g fro mth e chroni c intak e o f lead . I n th e Trail , B.C. , study, 2 horse s grazin g nea r alea dsmelte r develope dover t

symptom s o f

lea dpoisoning , bu t cow s i n th e sam e pastur e wer e no t clinicall y affected . Th e minima l toxi c dosag e fo r ahors e ha s bee n esti

mate dt o b e betwee n 1. 7 an d2. 4 mg/k g bod y weigh t daily, 1 whic hi s approximatel y 8 0 pp mdr y weigh t in forage . Th e reason s fo r

th e greate r

susceptibilit y o f

horse s ar e complex . A n earl y sympto moflea dpoisonin g in th e hors e i s paralysi s o f th e nerve s o f

th e pharyn x an dlarynx . Thi s interfere s withbreathing , especiall y o n e A ercise , an dcause s th e anima l t o breath e ster torously , o r

t o roar . Whe n severe , thi s paralysi s ca n produc e suffocatio n an ddeath . I n addition , th e fault y actio n o f

th e epiglotti s v whic hclose s of f th e lun g durin g inhalation ) permit s inhalatio n o f food , whic hca n resul t

in suffocatio n an ddeat ho r in sever e pneumonia , whic hca n als o b e fatal . Colt s pasture dnea r

th e Trail , B.C. , smelter 2 showe dlos s o f

weight , generalize dmuscula r weak

ness , stiffnes s o f

joints , an dharsh , dr y coats . Distor

tio n ofth e limb s occurred , th e joint s becam e greatl y enlarge dan dth e hock s touched . Th e laryngea l paralysi s usuall y associate dwithlea dpoisonin g di d no t occur . Hupka 9 note dth e sam e symptom s in colt s tha t ha dgraze do n pastur e contaminate dwithflu e dus t fro mameta l works . Autops y showe dtha t th e auricula r cartilage s wer e detache dan dloos e i n th e joint . Als o note dwa s a n acut e catarrha l pneumoni a o f bot hlobe s o f

th e lungs , wit hfoo dparticle s i n th e bronchi . Roarin g typica l o f chroni c lea dpoisonin g di dno t occu r unti l quit e late . Th e clinica l pictur e describe dabov e ha s com e unde r clos e scrutin y i n variou s laborator y studies. 14

- 1 5 becaus e o f

th e lac k o f consensu s a s t o whethe r i t wa s th e resul t

o f lea dpoisoning . Lea dan d zin c coexis t

in man y ores , an dbot hwer e presen t in th e tw o situation s referre dt o above . Unde r thes e condition s animal s bein g reare din th e are awoul db e expose dt o bot helement s simultaneously . Studie s b y Willoughb y e t

al. 1 4 indicate dtha t

lameness , blind

ness , swellin g a t

th e epiphysea l end s o f lon g bones , o r

a n increas e in th e amoun t o f join t flui din foal s resulte dfro mth e intak e o f zin c b y itsel f

an dzin c an d lea dtogether , bu t

no t fro mlea dalone . Gunther, 1 5 i n studie s base do n experimenta l exposur e o f colts , reache dsimila r

conclusions . Horse s sometimes , thoug hinfrequently , pul l u p plant s an dea t

root s an dsoi l alon g wit hleaves . Thi s practic e ma y b e afacto r in increasin g thei r

lea din

take 1 6 relativ e t o tha t

o f cattl e grazin g th e sam e pasture . Lea dpoisonin g in al l domesti c animal s produce s variou s degree s o f

derangemen t

o f th e centra l ner vou s system , gastrointestina l tract , muscula r system , an dhematopoieti c system . Younge r animal s appea r t o b e mor e sensitiv e tha n olde r ones. 1 3 Calve s ma y suddenl y begi n t o bello w an dstagge r abou t rollin g thei r eyes , frothin g a t

th e mouth , an dcrashin g blindl y int o objects . Thi s phas e ma y las t u p t o 2 hr , afte r whic hasudde n collaps e occurs . I n les s sever e cases , depression , anorexia , an dcoli c ma y b e ob

served . Th e animal s may becom e blin dan dma y grin dthei r

teeth , mov e in acircle , pus hagains t ob

jects , an dlos e thei r

muscl e coordination . Matur e cattl e displa y fewe r

over t symptoms , althoug hth e syndrom e o f

maniaca l excitemen t

i s no t uncom mon . Clinica l symptom s in shee p consis t mainl y o f depression , anorexia , abdomina l pain , an ddiarrhea . Anemi ai s als o commonl y associate dwit hlea d poisonin g i n sheep. 1 Pavlicevic 1 1 note s tha t clinica l symptom s in lamb s consis t o f paralysi s o f

th e ex tremities , pharynx , tongue , an dlarynx ; arigidl y hel dneck ; an da n anemi c mucou s membrane . Lamb s ma y b e poisone dthroug hth e mother' s mil k whe n th e ew e i s o n contaminate dpasture . Sterilit y an dabor

tio n in ewe s hav e bee n observe da s aresul t o f lea d ingestion. 1 Toxi c dosage s o f

lea dfo r domesti c animal s othe r tha n horse s an dcattl e hav e no t bee n calculate dfro m statisticall y reliabl e studies . Th e effect s o f

lea do n biologica l processe s in animal s generall y includ e effect s o n th e nervou s an d hematopoieti c system s an dth e kidne y tissue . Thes e effect s hav e bee n studie dwit hvariou s type s o f tes t animal s (primaril y th e rat ) at th e enzymatic , sub

cellular , cellular , an dtissu e morpholog y levels ; an d systemicall y a t

th e physiologica l an dbiochemica l levels . Th e mos t sensitiv e indicato r

i n rat s i s th e decreas e o f th e enzym e 8-aminolevulini c aci ddehydras e (ALAD ) tha t

regulate s hem e synthesis. 1 7 Lea d clearl y affect s tes t

animal s a t

th e subcellula r

an d enzymati c level s o f

biologica l function .P.1 2

8.1. 2 Wildlif

e Lea dha s s o permeate dth e environmen t tha t i t i s no w know n t o b e aregularl y occurrin g constituen t o f al l anima l life . Bird s an dothe r wil danimal s ar e ex pose dt o awid e rang e o f lea dlevels . Measurabl e amount s o f

lea dma y b e foun di n th e tissue s o f thes e animals , an dlea dpoisoning s hav e occurred . Toxi c effect s fro mth e ingestio n o f spen t lea dsho t wer e firs t observe di n duck s in 191 9 an dhav e sinc e bee n recognize da s amajo r healt hproble min bot h aquati c an duplan dspecie s o f waterfowl . I t

ha s bee n estimate dtha t

thousand s o f

ducks , geese , an dswan s di e o f lea dpoisonin g eac hyear. 1 8 Lea dpoisonin g fro mspen t

sho t ha s als o bee n reporte din gam e bird s suc ha s wil dpheasants , mournin g doves , an dquail. 1 9 Th e scop e o f

th e proble mbecome s readil y apparen t whe n it i s note dtha t

th e majorit y o f

th e bird s di e afte r th e huntin g seaso n i s over ; thu s i t i s th e breed

in g stoc k tha t i s lost . Spen t

shotgu n pellet s hav e bee n remove dfro mth e gizzard s o f bird s withlea d poisoning. 2 0 Piece s o f lea dmeta l whe n swallowe dar e normall y no t harmfu l t o human s o r othe r mammal s becaus e the y pas s throug hth e digestiv e trac t to o rapidl y t o los e mor e tha n amino r portio n ofthei r

surface s t o digestiv e enzyme s an dothe r substances . Bu t

i t shoul db e note dtha t

person s wh o consistentl y ea t gam e ofte n hav e somewha t elevate dbloo dlea d level s an dhig hfecal lea dlevel s fro mswallowin g lea dpellets . Th e gizzar do f abird , however , i s a comminutin g orga n fo r

foo dtha t

operate s b y grind

in g u p th e foo din amuscula r sac k containin g smal l stone s tha t

th e bir dha s swallowed . Spen t shotgu n pellet s lyin g in th e sedimen t o n th e bottom s o f

lake s ar e picke du p b y th e bottom-feedin g duck s in th e sam e manne r

a s pebbles . Becaus e th e sho t ar e soft , the y ar e groun dfin e an dmad e quit e susceptibl e t o digestiv e actio n rathe r

tha n jus t

comin g int o super ficia l contac t

withth e digestiv e tract , a s in mos t othe r animals. 2 1 Lea drelease dfro mth e gizzar di s absorbe db y th e lowe r

digestiv e tract . On e number- 6 lea dsho t ca n furnis henoug hlea dt o induc e fata l lea dpoisonin g i n aduck ; but , th e lengt ho f tim e a pelle t

i s retaine din th e gizzar ddepend s partl y o n it s siz e an dpartl y o n th e fibe r conten t o f th e diet . A hig hfibe r

die t i s especiall y conduciv e t o lea d poisoning . Th e numbe r

o f sho t require dt o poiso n a bir dals o depend s o n th e siz e o f th e bir ditself . Si x number- 6 sho t

ar e alway s fata l fo r

mallards , an d fou r o r fiv e number- 4 sho t

ar e generall y fata l fo r Canadia n geese. 2 2 Th e symptom s generall y associate dwit hlea d poisonin g in waterfow l ar e lethargy , anorexia , weak

ness , flacci dparalysis , emaciation , anemia , greenis h diarrhea , impactio n o f

th e proventriculus , an ddis

tentio n ofth e gal l bladder. 2 2 Waterfow l appea r t o b e at leas t twic e a s sensitiv e t o th e biochemica l effect s o f lea da s ar e ma n an dothe r mammals. 2 3 Deat hap pear s t o b e associate dwit hth e inhibitio n o f 8-aminolevulini c aci ddehydras e (ALAD ) b y lead. 23

- 2 4 I n instance s wher e insufficien t lea di s in

geste dt o caus e death , sterilit y ma y result. 1 I n a n attemp t

t o preven t

th e death s o f

waterfow l throug hth e ingestio n oflea dshot , th e U.S . Fis han d Wildlif e Servic e ordere dth e us e o f stee l sho t

durin g th e 197 6 huntin g seaso n in certai n area s o f th e state s i n th e Atlanti c Flyway . Despit e stron g oppositio n fro mth e Nationa l Rifl e Associatio n an dhunters , th e pla n i s t o exten dthi s limitatio n t o th e Mississipp i Flywa y durin g 1977. 2 5 Waterfow l mortalit y cause db y th e toxi c effect s o f lea dmin e waste s couple dwithenvironmenta l stres s wa s reporte db y Chup p an dDalke 2 6 fo r th e Coeu r d'Alen e Rive r

Valle y o f

Idaho . Becaus e o f

thei r feedin g habits , feedin g waterfow l consume dlea d fro mth e sediment s in th e shallo w area s o f th e rive r alon g withmetalli c material s adherin g t o root s an d tuber s o f aquati c plants . Ingestio n o f plant s contain

in g lea dca n als o contribut e t o lea dpoisonin g in waterfowl . Th e puffi n (Fratercula arctica), ase abird , i s in seriou s decline . I n studie s t o determin e th e cause , Parslo w e t

al. 2 7 not e th e fac t

tha t puffin s ten dt o con centrat e lea dthroug hth e foo dchai n (Tabl e 8-1) . Th e author s wer e no t

able , however , t o associat e ob

serve dlea dconcentration s withth e declin e o f th e species . TABL E 8-1 . ACCUMULATIO N O F CERTAI N HEAVYMETAL S FRO M SEAWATE R

B YFIS H (Ammodytes

AN D Clupea)

AN D APUFFIN " Meta l levels , ppm . we t weigh t Approximat e accumulatio n tactor s Meta l Mercur y Lea d Cadmiu m Coppe r Zin c Seawate r 0.0000 3 0.0000 3 0.0001 1 0.00 3 0.0 1 Fis h

0.03 7 < 0.00 2 0.30 9 1.7 4 5 3 Puffi n

0.7 9 0.3 6 1.6 7 4.4 9 9 5 Fish / seawate r 1,230 <6 7 2,80 0 58 0 5,30 0 Puffin / fis h 2 1 >18 0 5. 4 2. 6 1. 8 Puffin /

seawate r 26,30 0 12,00 0 15,00 0 1,500 9,50 0 8- 3P.1 3

Measurement s o f

lea dlevel s i n pigeons 28

- 2 9 an din son g birds 3 0 indicat e tha t urba n bird s hav e highe r lea dlevel s tha n rura l bird s (Tabl e 8-2) . Bagle y an d Locke 1 9 analyze d2 8 specie s o f bird s an dnote dth e concentratio n o f

lea di n th e liver s an dbon e tissue . Lea din th e liver s wa s a n indicatio n o f acut e ex posure , an din th e bone , o f chroni c exposure . Live r level s range dfro m0. 3 t o 5. 0 ppm , an dbon e level s range dfro m0. 2 t o 26. 0 ppm . A s migh t b e expected , th e highes t

level s wer e foun din aquati c waterfowl ; however , tl.. " ospre y (Pandion haliaetus), apredator , als o showe dh'° hbon e levels . Th e bon e lea dlevel s ar e a n indicatio n o f

continue dexposur e t o lea dan d serv e a s an indicatio n o f norma l level s rathe r

tha n advers e exposure. 1 9

TABL E 8-2 . SUMMAR YO F LEA D CONCENTRATION S I N BIR D ORGAN S AN D (ISSUE S FRO M AREA S O F HIGH-LEA D AN D LOW-LEA D ENVIRONMENT S (ppm , dr y weight ) Specie s an d lea d level 8 Red-winge d blackbird : Low(10 ) High(4 ) Hous e sparrow : Low(16 ) High(11 ) Starling : Low(11 ) High(13 ) Grackle : Low(10 ) High(11 ) Robin : Low(10 ) High(10 ) Feather s

26. 5 66. 8 27. 0 158. 3 6. 4 225. 1 36. 0 81. 4 25. 3 .79. 7 Gu t

2.1 " 2.6 d 2. 3 26. 2 1. 3 6. 0 1. 4 10. 2 3. 2 24. 5 Live r

5. 8 1. 2 0. 6 12. 0 4. 0 16. 1 2. 5 12. 1 2. 4 10. 5 Lun g

0. 4 4. 1 0. 9 6. 9 2.8 " 5.2* 1 2.3 " 2.7 « 2. 2 10. 3 Kidne y

2.1 d 4.1 « 3. 5 33. 9 3. 6 98. 5 3. 5 13. 5 7. 3 25. 0 Bone b

6. 9 9. 1 16. 9 130. 4 12. 8 213. 0 21. 5 62. 8 41. 3 133. 7 Muscle c

0.8 d 0.6 « 0. 9 2. 1 0.8* 1 2.4 " 0. 8 1. 4 1.0 d 1.2 d

a High-lea d an d low-lea d environment s ar e urba n an d rura l area s respectively : high-lea d are a fo rred-winge d blackbird s i s 1 0 m fro m a n interstat e highway . Sampl e siz e i n parentheses . b Femur . cPectoral . d Difference s betwee n low - an d high-lea d environment s no t significan t at th e 0.0 5 level : al l other s significan t at leas t at th e 0.0 5 level . Studie s o f

lea dexposur e an deffect s in wil d animal s othe r

tha n bird s ar e infrequent . Braham 3 1 studie dth e distributio n an dconcentratio n in th e Californi ase alio n (Zalophus californianus). H e note dtha t

accumulatio n wa s occurrin g in th e specie s bu t coul ddetec t

n o advers e effect s at

th e tim e ofth e study . Th e exposur e o f

smal l mammal s an dselecte d invertebrate s nea r

roadway s ha s als o bee n studied. 32 * 3 8 I n general , gradient s in bod y lea dcon centration s decline dwithincreasin g distanc e fro m th e road . Th e bod y lea dgradient s usuall y wer e simi

la r i n patter n to , thoug hlowe r than , th e soi l leve l gradients ; bu t

interestin g exception s wer e observe d i n som e cases . N o evidenc e o f toxicit y wa s observe d i n an y ofthes e animal s individuall y o r in relatio n t o populatio n distributions . An analysi s o f

lea dconcentration s in 3 specie s o f smal l mammal s fro m1 1 site s in Huntingdonshire , Grea t Britian, 3 2 showe dtha t

th e lea dconcentration s in th e animal s wer e mor e closel y associate dwit hth e typ e o f foo dconsume dtha n withnearnes s t o th e highwa y wher e th e ai r lea dconcentration s wer e highest . On e hundre dan don e mammal s —5 1 long-taile d fiel dmic e (Apodemus sylvalicus), 2 7 ban k vole s (Clethrionomys glariolus), an d2 3 fiel dmole s (Microtus agrestis) —wer e trappe dalon g road

sides. 3 2 Th e concentratio n o f lea dwa s significantl y highe r i n Microtus tha n i n Clethrionomys o r Apodemus (Figur e 8-2) . Th e marke ddifference s amon g th e lea dconcentration s o f th e thre e specie s ca n b e accounte dfo r

b y specie s behavio r

an dfoo d consumed . Microtus eat s gras s a s it s stapl e food , wherea s Apodemus feed s o n grain , seedlings , buds , fruit , haze l nuts , an danimal s suc ha s snail s an din

sects . Th e rang e o f

foo dfo r Clethrionomys encom passe s tha t

o f bot hth e othe r

species , bu t

th e habita t i s restricte dt o hedge s rathe r tha n th e ope n fiel d (Apodemus) o r

th e roadsid e (Microtus). Difference s in foo dan dfoo dcontaminatio n ma y therefor e ac 8- 4P.1 4

coun t fo r th e difference s in lea dconcentration s in th e thre e species .

FIEL D MOLE S (Microtus ) BAN KVOLE S (Clethrionomys ) FIEL D MIC E (Apodemus ) D-MEA N O F SPECIE S

306. 7 pp m dr y wt . MEA N P b O N VEGETATIO N 42. 5 pp m dr y wt . 33. 4 pp m dr y wt .

TYP E O F SIT E Figur e 8-2 . Concentratio n o f lea d I n thre e specie s o f smal l mammal s trappe d besid e majo r an d mino r road s an d a t ara bl e an d woodlan d sites. 3 3 I n astud y i

n centra l Illinois , sample s o f smal l mammal s wer e obtaine dfro marang e o f environ

ment s includin g thos e withi n 1 0 mof ahigh-traffic

volum e roa d( > 12,00 0 vehicles/24hr) , thos e withi n 5 mo f medium-us e road s (200 0 t o 600 0 vehicles/2 4 hr) , thos e withi n 5 mo f low-us e road s (<200 0 vehi

cles/2 4 hr) , an dthos e i

n urba n area s (approximatel y 100,00 0 inhabitants). 3 8 Al l specie s excep t

th e white-foote dmous e (Peromyscus leucopus), showe dhighe r concentra tion s o f lea din habitat s adjacen t t o high-traffic

volum e situations , especiall y in urba n areas . Sinc e th e hom e rang e o f

thi s specie s average s mor e tha n 5 0 mi n diameter , eve n thos e individual s caugh t neares t th e highwa y wer e undoubtedl y spendin g considera

bl e tim e muc hfurthe r remove dfro mth e traffi c source , possibl y accountin g fo r th e lo w lea dlevel s in thes e animals . Ther e wa s als o acorrelatio n betwee n habita t re quirement s an dlea dconcentration s in smal l mam mal s capture dnea r

high-traffi c roadways . Specie s requirin g dens e vegetation—th e prairi e vol e (Microtus ochrogaster), th e short-taile dshre w (Blarina brevicauda), th e leas t shre w (Cryptotis parva), an dth e whit e harves t mous e (Reithrodontomys megalotis) —ha dhighe r tota l bod y lea dburden s an d highe r level s in selecte dtissue s tha n di dthos e specie s suc ha s th e white-foote dmous e (Peromyscus maniculatus) an dth e hous e mous e (Mus musculus) tha t exten dthei r

hom e range s int o cultivate dfields. Ther e wa s als o acorrelatio n betwee n feedin g habit s an dlea dconcentration s in bod y tissues . Insectivore s (th e shrews ) ha dth e highes t lea dconcentrations ; herbivore s (voles ) ha dintermediat e concentrations ; an dgranivore s (dee r

mice , white-foote dmice , an d hous e mice ) ha dth e lowes t concentrations , reflect

in g th e fac t

tha t lea dconcentration s in see dtissu e ar e usuall y extremel y lo w ( < 1 ppm) . I t i s highl y doubtfu l tha t th e ver y lo w concentra tion s o f lea din thes e mammal s (Tabl e 8-3) coul db e havin g asignifican t

impac t o n thei r

populatio n dynamics . Studie s o f

lea dconcentration s in insect s i n centra l Illinoi s ecosystem s hav e show n positiv e correlation s withlea demissio n levels , decreasin g fro marea s ad

jacen t t o heavil y travele droad s t o area s remot e fro mroad s (Tabl e 8-4). 3 9 Ther e wa s als o astron g tren do f increasin g lea dconten t fro msuckin g t o chewin g t o predator y insect s collecte dnea r high

traffi c roadway s (Figur e 8-3) . Chewin g insect s pro babl y ingeste dmor e lea dfro mdeposit s o n leave s tha n di dinsect s tha t

suc k liquid s fro mth e interna l vascula r tissue s o f

plants . Dat ao n predator y insect s tha t fee do n lead-containin g herbivore s sugges t tha t lea di s selectivel y retaine di n th e body , leadin g t o biologica l concentratio n in thi s two-trophi c (feed

ing-level ) system. 3 9 Definitiv e studie s correlatin g toxicit y withen vironmenta l lea dconcentratio n hav e no t bee n done . 8.1. 3 Aquati cOrganism s Acut e lea dtoxicit y i

n aquati c organism s ha s bee n observe dan dstudie dexperimentally . Lea dtoxicit y in fis hi s partiall y relate dt o drainag e fro mmetalli c waste s int o streams . Earl y experiment s wer e carrie d ou t in Englan dwher e contaminatio n o f natura l water s b y lea dminin g cause dth e disappearanc e o f fis hfro mstreams. 1 Althoug hth e effec t o f lea do n lowe r form s o f

lif e i s no t wel l documented , it

ap pear s t o b e les s toxi c tha n in highe r forms. ' • 4 0 Apparently , lea dan dothe r metal s ar e irritatin g t o th e ski n o f

man y freshwate r

fishan dcaus e an unusua l reaction . Th e presenc e o f meta l in th e wate r aroun dthe mcause s acopiou s secretio n o f mucu s ove r th e whol e bod y surface , particularl y in th e gil l 8- 5P.1 5

TABL E 8-3 . MEA N LEA D CONCENTRATION S I N ORGAN S AN D TISSUE S O F SMAL L MAMMAL S FRO M

INDICATE D AREA S O F ENVIRONMENTA L LEA D EXPOSURE 3 ' (ppm , dry weight ) Specie s an d exposur e are a Blarina brevicauda: Hig h Mediu m Lo w Microtus ochrogaster: Hig h Mediu m Lo w Peromyscus

maniculatus: Hig h Mediu m Lo w Control 0 Mus musculus: Hig h Mediu m Lo w Control 0 Reithrodontomys

megalotis: Hig h Mediu m Lo w Tota l bod y 18. 4 6. 7 5. 7 5. 1 5. 9 1. 9 6. 3 4. 3 3. 3 3. 1 6. 8 6. 0 6. 7 2. 0 12. 3 3. 0 2.7 ± Gu t

24. 0 7. 0 3. 1 11. 0 18. 4 2. 8 19. 2 6. 0 4. 5 4. 3 18. 6 8. 8 4. 8 2. 7 17. 8 6. 2 3. 5 Splee n

4. 5 3. 6 2. 3 5. 3 2. 2 2. 4 19. 4 3. 0 6. 5 3. 7 12. 1 3. 1 5. 1 2. 1 145 9. 2 5. 6 Live r

4. 6 2. 0 1. 0 1. 6 1.2 1. 0 3. 5 1. 7 1. 8 1. 1 2. 9 1. 6 1. 6 1. 9 4. 7 1. 1 2. 3 Lun g

16. 9 5. 6 7. 8 2. 8 1. 8 1. 3 6. 4 2. 4 6. 1 1. 5 2. 8 3. 4 1. 7 3. 4 20. 9 4. 2 4. 7 Kidne y

12. 4 5. 8 3. 9 8. 1 7. 6 2. 8 7. 9 9. 0 3. 0 1. 8 8. 1 6. 6 3. 1 3. 4

— 2. 1 4. 8 Bone 8

67. 1 19. 9 12. 2 16. 6 23. 2 4. 6 24. 6 8. 0 6. 4 5. 7 19. 2 21. 0 23. 5 9. 3 109. 5 — 18. 4 Muscle 6

9. 7 5. 7 5. 4 8. 2 3. 0 2. 0 6. 8 7. 4 1. 8 2. 1 5. 9 3. 9 3. 4 3. 8 27. 5 4. 4 — a Femur . "Thigh . cContro l area s ar e field s mor e tha n 5 0 m fro m a road . TABL E 8-4 . LEA D CONCENTRATION S O F INSECT S A TTW O DISTANCE S FRO M A HIGH-TRAFFIC-VOLUM E ROA D

(INTERSTAT E HIGHWAY) 3 "

(ppm )

Feedin g typ e Suckin g Chewin g Predator y Mea n 0 t o 7 m fro m pavemen t 15. 7 27. 3 31. 0 24. 7 1 3 t o 2 0 m fro m pavemen t 9. 8 10. 4 20. 0 13. 4 area . Analysi s o f

thi s mucu s ha s reveale dth e pre senc e o f "considerabl e quantitities " o f lead. 4 1 Th e mucu s doe s not , however , preven t absorptio n o f

lea d int o th e fish. If

th e meta l leve l i s low , th e proces s i s harmles s becaus e th e excrete dfilmi s readil y shed ; bu t if highe r level s ar e present , th e mucu s blanke t generate dma y suffocat e th e anima l befor e it ca n b e shed . Th e phenomeno n ha s bee n observe donl y in freshwate r

fishan di s subjec t

t o modificatio n b y wate r hardness , temperature , an dothe r factors . I t shoul db e emphasize dtha t th e proces s describe d abov e i s entirel y externa l an dunrelate dt o lea d level s in th e bod y o f

th e fish. I n som e case s o f lea d poisonin g in freshwate r fish, mucu s formatio n ha s no t bee n observed . Symptom s o f chroni c lea dpoisonin g in fishin

clud e anemia , functiona l damag e t o th e inne r organs , possibl e damag e t o th e respirator y system , growt hinhibition , an dretardatio n o f sexua l maturity. 1

- 4 2 A stud y in centra l Illinois 4 3 o f bot hurba n an d rura l tributarie s o f

th e Salin e Branc ho f

th e Ver

milio n Rive r

showe dtha t

lea dappear s t o b e take n u p b y aquati c organism s b y mean s o f externa l con tac t rathe r tha n b y ingestion . Lea dconcentration s in aquati c organism s wer e foun dt o b e relate dt o th e amoun t o f contac t withsubstrates , suc ha s sediment s (Figur e 8-4) , tha t

contai n th e highes t

lea dcon centration s in th e streams . Thu s specie s difference s in Concentration s ar e determine din par t b y habita t preferenc e an dfeedin g habits . Filtere dwate r

fro mth e tw o stream s ha dcon centration s o f

lea dvaryin g fro m0 t o 1 5 mg/lite r o f wate r (ppm) , an dsuspende dsolid s in th e wate r con taine d1 5 t o 20 0 pp mlead . Th e highes t level s occur re di n th e urba n stream . Th e uppe r 1 0 c mo f

sedi

ment s in th e urba n strea mcontaine da n averag e lea d concentratio n o f

387. 5 ppm , mor e tha n 1 0 time s greate r tha n tha t

in th e rura l stream . Fis hi n th e rura l strea mcontaine dan averag e o f 1. 4 t o 4. 1 pp m 8- 6P.1 6

I STD . ERRO R D LO W P b EMISSION S ARE A C D HIG H P b EMISSION S ARE A



# i i

CHEWIN G PREDATOR Y INSEC TFEEDIN G TYPE S Figur e 8-3 . Mea n lea d conten t I n groupe d Insec t sample s take n fro m low- an d hlgh-lead-emlsslo n area s fo r sucking , chewing , an d predatory feedin g types. 3 9

o f lea di n dr y tissu e (Tabl e 8-5). 4 3 N o fishwer e foun din th e urba n stream . Lea dlevel s in th e inver

tebrate s range dfro mabou t 5 t o 2 0 pp min th e rura l strea mt o mor e tha n 35 0 pp mi n th e urba n stream . Thes e dat aappea r

t o b e in agreemen t

withrelativ e lea dlevel s foun din tubifici dworms , clams , an dfish in th e Illinoi s River. 4 0 Hardist y e t

al. 4 4 studie dlea dlevel s in estuarin e fish, bu t wer e unabl e t o determin e an y biologica l effect s o f lead . Merlin i an dPozzi 4 5 studie dlea dac cumulatio n b y freshwate r fish. Ioni c lea d(a s P b + + ) wa s concentrate dthreefol dwhe n th e p H ofth e lak e wate r wa s lowered . Lea dtoxicit y in fishwa s no t re ported . Toxicit y varie s withpH , temperature , hardness , an dothe r

wate r properties. 4 0 Th e concentration s o f lea dinjuriou s t o fichan dothe r aquati c an dmarin e lif e ma y b e foun di n Water Quality Criteria, 1972. 4(l Th e 96-h r

LC 5 0 valu e in sof

t wate r fo r rainbo w trou t (Salmo gairdneri) ha s bee n reporte dt o b e 1 mg/liter . Pickerin g an dHenderson 4 7 lis t th e sof t wate r LC 5 0 value s fo r

fathea dminnow s (Pimephales promelas) an dbluegill s (Lepomis macrochlrus) a s bein g 5 t o 7 , an d23. 8 mg/liter , respectively . I n har dwater , th e LC 5 0 value s fo r

th e las t tw o specie s ar e reporte da s """"" ) URBA N COMPARTMEN T *"*"" * COMBINE D COMPARTMEN T I I MARGINA L COMPARTMEN T

" •RURA L MAI N CHANNE L I"""* " RURA L TRIBUTARIE S

SEDIMENT S CLADOPHORACEA E

TUBIFICIDA E CHIRONOMIDA E SEDIMENT S AN O ORGANISM S Figur e 8-4 . Mea n lea d level s i n representativ e organism s an d sediment s of th e compartment s o f th e drainag e basi n of th e Salin e Branc h o

f th e Vermilio n River , III. 4 3 bein g 48 2 an d44 2 mg/liter , respectively; 4 7 wherea s fo r rainbo w trout , Davie s an dEverhard 4 2 repor t 47 1 mg/liter . Detrimenta l effect s o n fis hspecie s oc cu r at concentration s a s lo w a s 0. 1 mg/liter . I n studie s o f

rainbo w trout , mortalitie s attribute dt o lea doccurre dat

th e hig htes t

concentrations , whic h in sof t wate r wer e 95. 2 /xg Pb/lite r an di n har d water , 3.2 4 mg/lite r

tota l lea do r

0.06 4 mg/lite r

fre e lead. 4 2 Physica l abnormalitie s occurre dbetwee n 11. 9 an d6. 0 fig Pb/lite r in sof t wate r an dbetwee n 0.1 2 an d0.3 6 mg/lite r

tota l lea d(0.01 8 an d0.03 2 mg/lite r fre e lead ) i n har dwater . I n Daphnia magna, a n effec t o n reproductio n ha s bee n observe da t 0.0 3 m g Pb/liter. 4 8 A stud y o f

long-ter meffect s o f

lea dexposur e o n thre e generation s o f

broo k trou t (Salvelinus fontinalis) indicate dtha t

al l secon dgeneratio n trou t ex pose dt o 23 5 an d47 4 fig Pb/lite r develope dsever e spina l deformitie s (scoliosis) , an d3 4 percen t o f thos e expose dt o 11 9 fig Pb/lite r develope d scoliosis . O f

th e newl y hatche dthir dgeneratio n alevin s expose dt o 11 9 fig Pb/liter , 2 1 percen t develope dscoliosis . Analysi s o f residue s in eggs , alevins , an djuvenile s indicate dtha t accumulatio n o f lea doccurre ddurin g thes e lit e stages. 4 9 Wei r an dHine 5 0 utilize daconditione davoidanc eP.1 7

TABL E 8-5 . LEA D CONCENTRATION S O F PREDOMINAN T ORGANISM S FRO M TH E RURAL , URBAN , AN D COMBINE D COMPARTMENT S O F TH E DRAINAG E BASI N O F TH E SALIN E BRANC H O F TH E VERMILIO N RIVER , ILL. "

(ppm , dry weight )

Arithmeti cNumbe ro f Standar d Compartmen t an d organis m mea n sample s deviatio n TABL E 8-6 . SUMMAR YO F GOLDFIS H TOXICIT YDATA" )

Rural : Plants : Cladophora Potarrrgeto n

. InvertebrtiT f s : Hirudine a Oligochaet a Tubificida e Sphaeriida e Lirceus fontinalis Hexagenia

limbata Anisopter a Chironomida e Decapod a Fish : Catostomus

commersoni (whit e sucker ) Etheostoma

nigrum (Johnn ydarter ) Ericymba

buccata (Silverja wminnow ) Notropis umbratilus (Redfi n shiner ) Pimephales

notatus (Bluntnos e minnow ) Semotilus

atromaculatus (Cree k chub ) Urban : Plants : Claoophoi

. Invertebrates . Tub ' cida e Chironomida e Decapod a Combined : Plants : Elodea Cladophora Invertebrates : Tubificida e Chironomida e Physa Ps v, chodida e 20. 1 30. 0 12. 6 13. 2 16. 0 5. 5 7. 6 10. 4 6. 6 20. 1 4. 7 2. 4 4. 1 1. 8 1. 9 2. 7 1. 4 34 7 1 1

1 5 1 2 7 1 3 1 1 5 1 5 6 1 2 2 3

1 9 9 2 9 2 9 8 3 3 5 5. 1

5. 4 14. 8 7. 6 11. 8 3. 1 3. 4 9. 7 2. 4 18. 2 5. 2 1. 6 2. 4 0. 9 0. 6 2. 7 0. 6

13 9 36 7 15 3 1 1 89. 9 34. 9 48. 6 42. 7 41. 7 32. 3 2 9

5 4

2 2 7 7 1 1 2 1 0 4 37 3 106

93. 3 7. 5 33. 9 16. 4 25. 5 25. 5 techniqu e t o asses s th e deleteriou s effect s o f fou r meta l ions , includin g lead , o n goldfish . Behaviora l impairmen t

wa s note dfollowin g subletha l con centration s o f

lea dnitrat e (Tabl e 8-6) . Th e lowes t concentratio n tha t

gav e significan t

impairmen t

wa s 0.0 7 ppm . Shellfis hhav e bee n reporte dt o concentrat e lead. 1 Io n Arseni c Lea d Lea d (withou t calciu m carbonate ) Mercur y Seleniu m LC 50 . ppm a b 32. 0 (41. 6 t o 24.6 ) 110.0(121. 0 t o 100.0 ) 6. 6 (9. 2 t o 4.7 ) 0.8 2 (0.9 0 t o 0.75 ) 12. 0 (17. 0 t o 7.9 ) LCi.ppm h 1. 5 60. 0 1. 5 0.3 6 1. 0 Slop e 1.4 1.2 1. 6 1. 2 2. 5

a Base d o n a 7-daysurviva l time . ^Lowes t concentration s o f ion s tha t significantl yimpaire d conditione d avoidanc e response s an d thei rfraction s o f th e 50 - an d 1-percen t letha l concentrations . Tw o specie s o f

marin e gastropod s wer e show n t o concentrat e lea din thei r shells. 5 1 However , Valiel a e t al. 5 ' 2 reporte dtha t

thre e specie s o f

estuarin e bivalve s showe dn o increas e i n lea dwhe n sludg e fer

tilize r containin g lea dwa s adde dt o experimenta l plot s in asal t

marsh . Furthermore , th e lea dap parentl y wa s trappe db y th e mars hsurfac e sedi

ments , sinc e n o increase s wer e recorde ddownstrea m in th e detritu s o n cree k bottom s o r

in filter-feeding bivalves . Lea duptak e b y th e cordgras s Spartina alterniflora reduce s b y asmal l amoun t th e quantit y o f lea din th e sediments. 5 3 Aquati c lea dconcentration s o f 0. 5 mg/lite r

hav e bee n show n t o b e toxi c t o flagellate s an dinfusoria , th e microscopi c animal s tha t frequentl y develo p in decayin g organi c matter . Bacteria l decompositio n o f organi c matte r

i s inhibite db y lea dconcentration s o f 0. 1 t o 0. 5 mg/liter. 5 4 8. 2 EFFECT S O N PLANT S 8.2. 1 Route s o f

Plan tExposure s Plant s ma y b e expose dt o lea dthroug hth e leaves , stems , bark , o r

roots . Th e exten t

o f exposur e de

pend s o n th e amoun t

o f lea din th e immediat e en vironmen t

an dth e forman davailabilit y o f tha t lead . 8.2.1. 1 LEAVES , STEMS , AN D BAR K Particulat e substance s in th e air , includin g lead , ar e deposite do n plan t surface s b y fallout , impac

tion , an dprecipitation. 5 5 Precipitatio n may , i n addi

tio n t o depositin g material , was hof f o r leac hou t materia l fro mth e plan t surfac e o r

tissue . Win dan d sloughin g o f

th e cuticl e wa x ma y als o remov e deposite dmaterial . Thus , meteorologica l factor s ar e importan t

in determinin g th e fat e o f compound s tha t com e int o contac t

wit hplan t

surfaces . Th e morpholog y ofth e plan t surface , however , play s th e majo r rol e in determinin g th e typ e an dquantit y o f mateiia l tha t

will b e retaine db y tha t plan t sur face. 565 7 Epiderma l cellso f th e aeria l part s o f

plant s ar e usuall y coate dwithawaxy substance , cutin , an d ofte n for municellula r

o r multicellula r

hairs , spines , o r glands . I n addition , secretion s fro mglandula rhair s ma y mak e lea f surface s sticky ; thus , particulat e materia l ca n accumulat e o n th e plan t surface , partic

ularl y th e leaves . However , particulat e matte r mus t ente r th e interna l plan t

tissue s t o affec t

th e plant. 5 6 Franke 5 8 suggest s tha t

th e cuti n i s penetrabl e vi ain

termolecula r

space s an dtha t

cuticl e ha s bee n show n t o b e permeabl e t o bot horgani c an dinorgani c ion s an dt o undissociate dmolecules . Th e capabilit y o f an io n t o penetrat e i s determine db y it s charge , adsorb

ability , an dradius . Vascula r plant s hav e smal l surfac e openings , calle dstomat aan dlenticels , tha t functio n in ga s ex change . Stomat aar e als o site s o f exchang e o f aqueou s substance s unde r certai n conditions. 5 8 Stomat aoccu r

in th e epidermi s o f

leave s an dyoun g stems . Lenticel s ar e foun do n olde r stem s o f wood y species . Surroundin g th e stomata l pore s ar e guar d cell s tha t ope n an dclos e th e pore s throug hchange s in thei r turgidity . Ga s exchange , whic htake s plac e throug hth e stomat aa s th e resul t o f aconcentratio n gradient , i s apassiv e phenomeno n unlik e th e activ e breathin g o f

animals . Larg e deposit s o f

inert , insolubl e meta l com pound s o n th e leave s ar e probabl y o f littl e conse quenc e t o aplant . Th e mos t importan t

facto r in determinin g folia r

penetratio n i s th e solubilit y ofth e individua l metal. 565 8 Th e insolubilit y oflea di s un doubtedl y amajo r

reaso n tha t

littl e incorporatio n an daccumulatio n occu r throug hth e lea f

surface. 5 6 Carlso n e t

al. 5 7 experimentall y fumigate dsoybea n (Glycine max

L. ) withPbC l 2 aeroso l particulate ; n o intraplan t

movemen t

wa s noted . Simulate drainfal l remove du p t o 9 5 percen t o f th e topicall y applie d lead . Studie s b y Arvi k an dZimdahl 59

- 6 0 indicate d tha t onl y extremel y smal l amount s o f lea dcoul d penetrat e plan t

cuticles , eve n afte r

extende dex posure . Increase dpenetratio n o f som e cuticle s oc curre dafte r

th e remova l o f

waxes , bu t

penetratio n seeme dmor e relate dt o plan t specie s tha n t o cuticl e thickness . Oat s (Avena sativa L. ) an dlettuc e {Lactuca sativa var . Black-Seede dSimpson ) ar e tw o species , accordin g t o Rabinowitz , whos e leave s atmospheri c lea di s capabl e o f

penetrating. 6 1 Th e onl y conclusio n possibl e fro mcurren t

dat ai s tha t

airborn e lea dca n b e take n u p b y th e foliag e o f som e plants , bu t

onl y in extremel y smal l amounts . A recen t report 6 2 suggest s tha t

grasse s an dsmal l herbaceou s plant s in th e field , a s wel l a s pe aplant s (Pisum sativum L. ) an dpin e tre e seedling s (Pinus sylvestris L. ) in th e laboratory , whe n grow n in nutrien t solution , releas e lea dan dzin c int o th e air . I t i s questionabl e whethe r th e lea dexude dfro m plan t leave s add s appreciabl y t o th e atmospheri c burden . Th e complexitie s o f lea dmovemen t

fro m soi l int o plant s mak e i t

unlikel y tha t

plant s ar e capa bl e o f exudin g larg e amount s int o th e air . Particle s containin g lead , in additio n t o chlorin e an dbromine , hav e bee n foun dembedde di n th e bar k o f bot hpin e an del mtree s growin g nea r highways . Th e lea dconten t

o f th e particle s o n th e tree s decrease dove r

a3-year period , an dth e particle s o n th e bar k o f el mtree s showe dles s lea dtha n thos e o n pin e trees. 6 3 N o evidenc e exist s t o sho w tha t lea den tere dth e tree s throug hth e bark . Tree s hav e bee n use da s indicator s o f increasin g environmenta l lea dconcentration s wit htime. 6 4 Studie s in centra l Illinoi s hav e show n afivefoldin

creas e in lea din tre e ring s durin g th e las t 5 0 year s (Figur e 8-5) . Thi s graphicall y illustrate s th e increas e in environmenta l lea duptak e tha t ha s occurre din tha t time . However , dat areporte db y Holtzma n o n fou r hardwoo dtree s in arura l suburba n are aan do n on e tre e in asuburba n are anea r Chicag o (tre e age s wer e 100 t o 120 years ) showe dn o consisten t in

creas e o r decreas e i n lea din th e tre e rings. 6 5 10-yea r AVERAGE , 1963 - 197 3

Figur e 8-5 . Tre e rin g analysi s o f lea d concentration s i n urba n an d rura l trees. 6 3 8.2.1. 2 ROOT S Th e roo t syste mi s th e majo r

pathwa y o f

plan t ex posur e t o lead , a s lea din th e soi l ma y b e absorbe db y th e root s an dmove dint o th e plant. 6066 " 7 7 Bu t th e tota l lea dconten t

ofth e soi l i s onl y on e o f severa l in

8- 9P.1 9

teractin g factor s determinin g plan t uptake . Thes e factor s ar e no t

wel l understood , bu t

uptak e i s know n t o b e influence db y plan t specie s an db y th e availa

bl e lea dpoo l in soils. 66

- 717 4 Th e poo l o f availabl e lea di s determine db y soi l pH , soi l organi c an dcla y fractions , an dth e catio n exchang e capacit y a s wel l a s othe r soi l sorptio n characteristics. 66

- 70 * 8 ' Absorptio n o f lea db y plan t

root s i s inversel y relate dt o catio n exchang e capacity. 74

- 79

- 8 0 Th e tota l lea din th e soi l i n relatio n t o catio n exchang e capacit y determine s lea d availability. 8 0 Root s tak e u p mineral s tha t ar e in th e soi l solution; 60

- 8 2 thu s lea dmovemen t int o root s i s in th e formo f

ion s fro mth e soi l solutio n o r fro mweak sorptio n sites. 60

- 66

- 7 4 Baumhard t

an dWelch 7 0 hav e show n tha t th e per centag e o f

solubl e lea di n soi l decrease s withtim e a s sorptio n occurs . Soi l phosphate 60

- 75

- 77

- 7 8 an dlim

ing, 60

- 75

- 83

- 8 4 a s wel l a s cadmium 8 5 in soil , reduc e th e uptak e o f

lea db y plan t

roots . Olso n an dSkoger

boe 8 6 hav e identifie dth e primar y lea dspecie s in thei r soi l test s a s lea dsulfat e (Chapte r 6) . A t pres ent , th e capabilit y o f

plant s t o tak e u p thi s relativel y insolubl e formi s no t

understood. 7 4 Jone s e t al. 8 7 hav e reporte dtha t

lea duptak e i s enhance db y adefi

cienc y o f sulfat e in th e soil . I n thi s study , th e lea di n ry e gras s top s wa s highe r tha n tha t

in th e root s whe n th e soi l wa s deficien t

in sulfur . Onc e lea denter s th e plan t fro mth e soi l solution , mos t o f it remain s in th e roots. 60

- 66

- 72

- 7 7 Distributio n t o othe r portion s o f

th e plan t

doe s occur , bu t

it i s uneve n an dvariabl e amon g species. 71

- 72

- 7 7 Plan t ag e an dseaso n o f

th e yea r als o affec t

interna l distribu

tion. 66

- 7 2 I n al l cases , th e level s ar e quit e lo w becaus e o f th e smal l amount s o f

availabl e lea din th e soi l solution . 8.2. 2 Effect s o n Vascula rPlant s Lea di s anorma l soi l constituent , bu t it ha s no t bee n show n t o b e essentia l fo r plan t growth. 66

- 6 9 Th e respons e o f

plant s t o lea di s therefor e dependen t o n th e exten t

t o whic hnorma l metaboli c processe s ar e disturbed . Metaboli c disturbance s manifes t them

selve s a s growt habnormalitie s (th e visibl e symptom s o f whic hma y b e growt hstimulation , stunting , yellowin g o r

purplin g o f

leaves ) or , in th e even t o f acut e toxicity , senescenc e an ddeath. 8 2 Metaboli c disturbance s ar e mos t

likel y t o occu r

in respons e t o hig havailabl e lea dlevel s an dt o highl y solubl e form s o f lea denterin g th e plant. 66

- 6 9 Antonovics , Bradshaw , an dTurner 8 8 stat e tha t lea duptak e i s constan t

wit hincreasin g level s o f soi l lea dunti l acertai n poin t i s reache dat

whic hlea d uptak e become s unrestricte dan drise s abruptly . Lit

tl e i s known , however , abou t th e mechanis mo f

lea d uptake . Undoubtedly , lea din solutio n move s int o th e plan t throug hth e roo t

hair s alon g withminera l nutrient s an di s translocate dt o othe r area s o f

th e plant . Th e vascula r

tissu e i s th e pathwa y o f wate r in th e root , throug hth e stem , int o th e petioles , an dint o th e lea f veins. 8 9 After

enterin g th e roo t

hairs , wate r containin g lea dan dnutrient s mus t pas s throug hth e roo t corte x t o reac hth e centra l cor e o f vascula r tissue . Becaus e th e movemen t o f wate r throug hth e corte x i s fro mcel l t o cel l wit hn o specifi c pathwa y suc ha s vascula r

tissue , lea dpossibl y ma y no t pas s easil y throug hcel l membranes . Thi s ma y explai n why plan t

root s sho w highe r

lea dcontent s tha n othe r plan t organs . Malon e e t

al. 9 0 hav e show n tha t

som e ofth e lea dtha t

enter s th e roo t

i s concentrate din dic

tyosom e vesicle s an dsubsequentl y move s vi ath e vesicle s t o th e cel l wall , wher e fusio n withth e cel l wal l occurs . Lea dha s bee n reporte dt o hav e bot habeneficia l an da n inhibitor y effec t o n plan t

growth. 66

- 6 9 Brewer 6 9 cite s studie s in whic hlea dnitrat e resulte d in increase dnitrificatio n an dincrease dplan t growt h whe n adde dt o th e soil . However , whe n lea dnitrat e wa s adde dt o solutio n cultures , retardatio n o f roo t growt hoccurred . I n neithe r cas e wa s th e metaboli c actio n o f lea dnitrat e observe din th e plants . Th e chemica l identit y o f

lea di n plant s i s a s yet no t known. 6 0 Mos t studies 60

- 66

- 6 9 tha t

describ e growt hinhibitio n an dplan t

toxicit y cause db y lea dcompound s ar e base do n visibl e growt hresponse s resultin g fro m lea dadde dt o soil s o r

t o solutio n culture s an dd o no t dea l wit hspecifi c metaboli c processes . Th e effect s o f

lea dcompound s o n suc hplan t pro cesse s a s photosynthesis, 60

- 91-9 3 mitosis,'- 60

- 6 6 an d wate r uptake 9 2 hav e bee n reported . Mile s e t al., 9 1 usin g isolate dchloroplast s fro mspinac hleaves , foun dtha t

lea dsalt s inhibi t

photosyntheti c electro n transport . Won g an dGovindjee 9 4 hav e show n in isolate dmaiz e chloroplast s tha t lea dsalt s affec t photosyste mI , inhibitin g P70 0 photooxidatio n an d alterin g th e kinetic s o f re-reductio n o f

P700 . I n laborator y studies , lea dha s bee n foun dt o hav e a damagin g effec t

o n cel l walls , nuclei , an d mitochondria . Lea dretarde dcel l proliferatio n bu t permitte da n increas e in size. 1 Spindl e disturbance s an dchromati dformatio n in roo t tip s o f Allium cepa induce db y lea dnitrat e hav e bee n foun dt o b e in

distinguishabl e fro mthos e induce db y colchicine. ' Mille r an dKoeppe 9 5 an dBittel l e t al. 9 6 studie d th e effect s o f

lea do n mitochondria l respiration . Lea deffect s ar e relate dt o th e phosphat e statu s o f 8-1 0th e respirator y syste ma s wel l a s t o th e oxidatio n o f

nicotinamid e adenin e diphosphonucleotid e monohydroge n (NADH) . Th e lea dlevel s use din thi s stud y approximate dth e level s foun dnea r heavil y travele dhighways . Th e formo f lea dused , Pb C 1 2 , an dth e isolate dmitochondri awer e no t typi

ca l o f fiel dconditions , bu t

lea din plant s doe s associ

at e wit hmitochondri aan dchloroplas t membranes. 60

- 66

- 7 5 Th e presenc e o f

lea din plant s ha s als o bee n show n t o hav e indirec t

effect s o n plan t

growth . Fo r

exam ple , absorptio n o f

phosphoru s an dmanganese , tw o essentia l element s fo r

growth , i s inhibite dwhe n lea d i s presen t in th e plant. 9 7 Lea dmay als o contribut e t o coppe r deficienc y in plants. 9 8 Th e majorit y ofth e studie s reportin g lea dtoxicit y hav e bee n conducte dwit hplant s grow n i n artificia l nutrien t culture . A s aresul t

o f th e studies , th e con cep t ha s emerge dtha t

th e effect s o f

lead , whethe r stimulator y o r

inhibitory , depen do n avariet y o f en vironmenta l factors , includin g associate danion s an d cation s withi n th e plan t an di n th e growt hmedia , an dth e physica l an dchemica l characteristic s ofth e soi l itself . Becaus e lea dinteract s wit hs o man y en vironmenta l factors , specifi c correlation s betwee n lea deffect s an dlea dconcentration s ar e extremel y difficul t t o predict. 6 0 Lea dtoxicit y ha s no t

bee n observe din plant s growin g unde r

fiel dconditions . Thi s observatio n ma y b e explaine db y th e fac t tha t ambien t lea dcon centration s in th e environmen t hav e no t

bee n hig h enough , excep t

unde r unusua l condition s (nea r mine s an dsmelters ) t o caus e atoxi c effec t o r a decreas e i n cro p yield. 6 0 I n summary , th e effect s o f lea do n vascula r

plant s appea r a t thi s tim e t o b e minimal . Th e mos t impor

tan t effect s ma y b e thos e resultin g fro mingestio n o f topica l an dinterna l plan t lea db y grazin g animal s (th e nex t trophi c level) . Fro mth e standpoin t o f eco nomi c consequences , evidenc e develope do n th e effect s o f lea din agroecosystem s indicate s tha t topi

ca l lea dcontaminatio n o f plant s i s mor e likel y t o hav e economi c consequence s tha n interna l lea d(se e Sectio n 6.4.3) . 8.2. 3 Effect s o n Nonvascula rPlant s 8.2.3. 1 MOSSE S AN D LICHEN S Mosse s hav e bee n show n t o hav e uniqu e capacit y fo r sorbin g heav y meta l ion s t o thei r surfaces . Trace s o f coppe r an dlea dar e sorbe dreadil y eve n in th e presenc e o f

othe r meta l ion s (calcium , magnesium , potassium , sodium). 9 9 Thes e ion s ar e sorbe dthroug h th e leave s o f

th e mos s becaus e mosse s hav e n o roo t syste mfo r uptak e o f

nutrient s fro msoi l o r othe r substrates . Mosse s als o hav e neithe r epiderma l cell s no r acuticl e (wax y layer) , s o th e interna l parenchyma l cell s ar e readil y expose dt o substance s fro mth e air. 9910 0 Accumulatio n o f heav y meta l ion s in mosse s i s generall y fro mprecipitation , whic hi s a ver y dilut e solutio n o f metal s an dwater . Th e ac cumulatio n occur s becaus e ofth e chemica l complex

e s forme dbetwee n thes e heav y meta l ion s in pre cipitatio n an dnegativel y charge dorgani c growth. 10 1 Lichens , lik e mosses , hav e n o roots ; therefor e al l mineral s ar e absorbe dthroug hth e cel l membranes . Mechanism s simila r

t o thos e foun di

n mosse s may als o b e responsibl e fo r

th e uptak e o f

meta l ion s b y lichens . Bu t

liche n accumulatio n o f lea di s no t

a s ex tensiv e a s tha t

in mosses. I0 1 8.2.3. 2 ALGA E Trollop e an dEvans, 10 2 in astud y o f alga l bloom s in th e Lowe r

Swanse aValley , Wales , note dth e sen sitivit y o f alga e t o th e heav y meta l conten t o f water . A marke ddifferenc e wa s observe din th e natur e o f alga l bloom s foun din thre e differen t group s o f water s a t 1 2 differen t

station s (Tabl e 8-7) . Th e alga e mos t toleran t t o hig hlea dconcentration s were : Coccomyxa, Mougeotia, Tribonema, an dZygnema. Les s toleran t wer e Microspora, Oscillatoria an dUlothrix, an dth e leas t

toleran t wer e Cladophora, Oedogonium, an dSpirogyra. Al l ofthes e alga e wer e subjec t t o con taminatio n fro mrun-of f wate r an ddus t

fro mth e zin c smelter . Th e concentration s o f lea din th e plant s varie damon g gener aan dwithi n agenus . Th e uptak e o f individua l metal s b y alga l bloom s appear s t o b e regulated . Mea n meta l concentration s in th e thre e group s o f

alga e ar e ordere dF e >Z n >P b >C u >Ni , wherea s th e mea n meta l concentration s i n th e aquati c bodie s wer e ordere ddifferently : Adjacen t t o th e source , Z n >P b >F e >N i >Cu ; near , Z n >N i >P b >F e >Cu ; distan t ( 6 t o 10km),F e >Z n >Ni , P b >Cu . Concentration s o f metal s in th e alga e wer e directl y relate dt o th e concentration s in th e water , wit hth e alga e in th e mos t pollute dwater s havin g th e highes t concentrations . N o experiment s wer e con ducte dt o determin e whethe r th e alga e foun din th e leas t pollute dwater s woul dgro w in mor e pollute d ponds . Observation s in th e Ne w Lea dBel t o f south

easter n Missouri 10 3 hav e show n tha t relativel y hig h concentration s o f

lea din strea mbotto msediment s d o no t hav e muc heffec t

o n alga l growt hin thes e re lativel y har dnatura l waters . Unde r thes e conditions , th e dissolve dlea dsalt s ar e in ver y lo w concentra tion s an dwel l belo w th e limit s o f toleranc e o f

mos t 8-1 1P.2 1

TABL E 8-7 . CONCENTRATION S O F SELECTE D HEAVYMETAL S I N FRES H WATE R AN D I N FRESHWATE R ALGA L BLOOMS" " Concentration s i n fres h waters . \i g 'm l Concentration s i n freshwate ralga l blooms , M 9'm g Are a o f wate r Fe N i P b Alga l bloo m C u Fe N i P b Z n Wate radjacen t t o zin csmeltin g waste : 1 0-0 3 0-2 4 0-1 5 0-3 1 34- 1 2 3 4 Mea n 0-02 0-1 1 0- 1 1-2 4 19-6 1 0-0 1 0-2 5 0-1 2 0- 1 11-44 0-02 0-2 8 0-1 5 0- 1 1-9 6 0-02 0-22 0-1 3 0-4 4 16-7 8 Mougeoti a

Tribonema a Tribonem a b Tribonema c Tribonem a d Coccomyx a Zygnem a Mea n Wate rnea rzin c smeltin g 5 6 7 Mea n waste :

Wate rdistan t fro m zincsm e 8 9 1 0 1 1 1 2 Mea n Itin g waste : 0-0 2

0-0 5 0-0 6 0-0 4

0-0 3 0-0 2 0-0 1 0-0 2 0-0 2 0-0 2 0-2 7 0-5 6 0-5 6 0-4 6

0-3 9 0- 1 0-3 9 0-3 9 0-1 1 0-2 8 0-1 2 2- 2 2-9 4 1-7 5 0-0 7 0-0 6 0-1 2 0-1 2 0-1 2 0- 1 0- 1 0-3 1 2-9 1 1-1 1

0- 1 0- 1 0- 1 0- 1 0- 1 0- 1 1-96 4- 9 4- 9 3-9 2 0-2 1 0-0 8 0-0 8 0-1 6 0-0 5 0-1 2 Oscillatori a

Ulothri x Microspor a Mea n Cladophor a a Spirogyr a a Spirogyra b Oedogoniu m Cladophor a b Spirogyr a c Spirogyr a d Mea n 0-3 8 0- 4 0- 7 0-6 7 1-3 3 0-6 5 0-4 6 17-6 1 9-9 7 33-9 2 23-3 7 30- 6 49-5 1 39-8 5 0-2 4 0-1 6 0-2 6 0-2 9 0-2 4 0-1 5 0- 7 6-1 9 5-4 5 4-9 4 3-6 8 14-1 9 3-2 3 2- 6 44-9 4 19-9 3 17-6 1 21-1 1 17-4 4 19-0 5 45-8 9 0-6 6 29-2 6 0-29 5-7 5 26-5 7

0-3 4 0-4 8 1-0 2 0-6 1 0-0 6 0-2 2 0-2 9 0-1 1 0-0 5 0-2 3 0-0 5 0-1 4 2- 8 7-7 8 42-3 1 17-6 3 3-9 4 3-0 3 7-6 6 0- 7 2-9 1 0-4 6 8-9 3 3-9 5 1-0

7 0- 3 0-1 1 0-4 9

0-0 3 0-1 3 0-1 2 0-0 7 0- 1 0-0 9 0-0 3 0-0 8 0-5 8 2-3 8 2-1 6 1-7 0 0-2 3 0- 4 0-1 1 0-0 6 0-0 9 0-1 3 0-0 4 0-1 5 1-88 3-5 6 9-2 6 4-8 9 0-8 9 1-59 1-9 2 0-1 2 0-9 7 1-09 0-3 2 0-9 8 algae , includin g th e sensitiv e Cladophora. Extensiv e bloom s o f

Cladophora wer e observe din on e strea m wher e boun dlea dassociate dwithth e filament s ex ceede d500 0 ppm . Thes e result s indicat e tha t lea d chelate do r

boun dt o th e cel l envelope s apparentl y ha dn o majo r

physiologica l effec t

o n alga e unde r

th e existin g natura l conditions . 8.2.3. 3 BACTERI A Th e respons e o f

certai n bacteri at o lea dha s bee n studie db y Tornaben e an dEdwards. 10410 5 Micrococcus luteus an dAzotobacter sp. , whe n grow n in lead

containin g medi aunde r experimenta l conditions , wer e abl e t o tak e u p substantia l quantitie s o f lea d withn o apparen t

effect s o n cel l viability . Mos t ofth e lea dbecam e associate dwithth e cel l membrane . Sev

era l studies 10610 7 indicat e tha t bacteri ain lak e sedi

ment s unde r

anaerobi c condition s reac t differently . Methylatio n o f

mercur y an darseni c b y microorgan

ism s i s awell-know n phenomenon, 10810 9 bu t th e methylatio n o f

lea di s not . Th e first

evidenc e fo r

th e methylatio n o f

lea dwa s demonstrate dexperimen

tall y b y Won g e t

al. 11 0 Microorganism s i n lak e sedi

ment s wer e abl e t o transfor mcertai n inorgani c an d organi c lea dcompound s int o avolatil e tetramethy l lea d(Me 4 Pb ) whe n th e sedimen t wa s enriche dwith nutrien t brot han dglucos e t o stimulat e growt han d growt hoccurre dunde r anaerobi c conditions . Th e Me 4 P b lea dproductio n wa s greatl y increase dwhe n inorgani c lea dnitrat e o r organi c trimethy l lea dace tat e (Me 3 PbOAc ) wa s adde dat 5 mg pe r

lite r o f sample . Th e biologica l methylatio n fro mtrimethy l lea d(Me 3 Pb ) t o Me 4 P b appeare dt o procee dquit e readily . Thi s conversio n wa s demonstrate dusin g pur e specie s o f

bacteria l isolate s fro mlak e sediment s withou t th e sediment s bein g present . The y wer e abl e t o sho w tha t

Pseudomonas, Alcaligenes, Acinetobacter, Flavobacterium, an dAeromonas sp . growin g in achemicall y define dmediu mcoul d transfor mlea dnitrate , lea dchloride , an dtrimethy l lea dacetat e (Me 3 PbAc ) int o volatil e tetramethy l lea d(Me 4 Pb) . Non e ofth e bacteri awer e abl e t o con ver t insolubl e lea dt o Me 4 Pb . Schmid t an d Huber, 10 7 however , hav e observe dtha t Pb 2 + ca n b e biologicall y alkylate dan dtransforme dt o Me 4 P b (se e Sectio n 6.4.2.2) . Generally , mos t

naturall y occurrin g bacteri aca n tolerat e lea dwithou t

toxicity.' 0 4 " 0 However , ther e i s wid e variatio n in effects . Fo r example , lea dha s bee n show n t o stimulat e growt hof abacteriu miden

8-1 2tifie da s Micrococcusflava Strevisan," ' producin g an

insolubl e lea dmetabolite ; bu t lea dha s als o bee n show n t o b e widel y inhibitor y t o aerobi c activate d sludg e bacteria," 2 aerobi c rive r wate r bacteria," 3 an dmarin e sulfate-reducin g bacteria." 4 Thes e re port s see mt o indicat e tha t lea dha s arelativel y casua l relationshi p withbacteria l cells , withn o specifi c inhibitor y role ; bu t thi s shoul db e viewe d withcaution . Previously , th e presenc e o f lea din estuarin e sedi

ment s wa s mentioned . Th e methylatio n o f lea din thi s environmen t

an dit s effect s o n th e biot aexistin g ther e hav e no t

bee n studied . Effect s o f

th e additio n o f

100 0 pp mo f

copper , nickel , lead , an dzin c o n carbo n dioxid e releas e dur

in g aerobi c incubatio n o f soi l alon e an dafte r

treat men t withstra w wer e studied. 11 5 Carbo n dioxid e re leas e durin g incubatio n fro msoil s withou t adde d stra w wa s decrease db y al l metalli c elements . Car

bo n djoxid e releas e fro msoi l plu s stra w wa s decrease db y lead . Th e toxi c effect s ofth e hig hcon centratio n o f

element s o n th e activit y o f th e microorganism s attackin g organi c matte r wer e believe dt o b e cause db y th e abilit y o f th e element s t o compet e wit hessentia l element s (manganese , iron , an dzinc ) fo r

th e activ e site s (SH , NH 2 , = NH ) o f enzymes . Nicke l an dlea dwere slightl y mor e in

hibitor y tha n coppe r

an dzinc. 11 5 Cole' 1 6 foun dtha t

additio n o f

lea dt o soi l resulte d i n 75

- an d50-percen t

decrease s in net

synthesi s o f amylas e an da-glucosidase , respectively . Th e decreas e in amylas e synthesi s wa s accompanie db y a decreas e i n th e numbe r o f lead-sensitive , amylase

producin g bacteria , wherea s recover y o f synthesi s (usuall y in 2 4 t o 4 8 hr ) wa s associate dwithan in

creas e i n th e numbe r

o f amylase-producin g bacteria , presumabl y lead-resistan t forms . Th e result s indi

cate dtha t

lea di s apoten t

bu t somewha t

selectiv e in

hibito r o f enzym e synthesi s in soi l an dtha t highl y in

solubl e lea dcompound s suc ha s Pb S ma y b e poten t modifier s o f

soi l biologica l activity . 8. 3 EFFECT S O N RELATIONSHIP S BE TWEE N ARTHROPOD S AN D LITTE R DECOMPOSITIO N A study" 7 o f

th e impac t

o f alea dsmeltin g com ple x i n southeaster n Missour i focuse do n forest

floo r litte r arthropo dfauna . Litter-arthropo dfoo d chain s an dth e possibl e transfe r o f lea dthroug h plant-herbivore-carnivor e foo dchain s wer e studie d a s amean s o f

detectin g perturbation s in thi s ecosystem . Bot hpoin t an dfugitiv e source s con tribute dt o heav y meta l level s i n th e stud y area . Lead , cadmium , zinc , an dcoppe r wer e th e primar y element s studied . Litte r mass , heav y meta l an d macronutrien t

conten t (Ca , P , K , an dMg) , catio n exchang e capacity , an dp H wer e studie dt o charac

teriz e th e arthropo dfoo dbase . Arthropod s wer e remove dfro mlitte r

b y Vo n Tullgre n funne l extrac tion . Th e arthropod s wer e taxonomicall y classifie d accordin g t o thei r

feedin g habit s o r

levels : detritivore , fungivore , littergrazer , omnivore , an d predator . Leve l refer s t o th e sequentia l locatio n of a particula r

organis min th e foo dchai n o r web . Thei r populatio n densit y a t

eac htrophi c level , biomass , an dheav y meta l an dmacronutrien t conten t wa s determined . Change s i n litte r

decompositio n an dnutrien t cy clin g wer e reflecte di n th e populatio n dynamic s o f litte r arthropod s an dmacronutrien t pools . Reduce d arthropo ddensity , biomass , an drichnes s (a n esti

mat e o f maximu mdiversity ) wer e observed . Th e macronutrient s Ca , K , an dM g in th e 0 1 an d0 2 litte r laye r a t asit e 0. 4 k

mfro mth e smelte r

wer e signifi

cantl y reduced . Tw o litte r layer s o r

horizon s ar e recognize db y th e Soi l Scienc e Societ y o f America . Th e 01 , o r

surfac e layer , i s tha t

in whic hdea dplan t materia l stil l retain s it s origina l conformation . Th e 0 2 laye r i s tha t laye r in whic hth e materia l i s frag

mente dan dn o longe r

recognizabl e a s t o specie s o r origin . Mea n heavy-meta l concentration s wer e greate r in th e undecompose d0 2 litte r laye r collecte da t

0.4 5 an d0. 8 k

mfro mth e smelter . Th e P b concentratio n wa s 103,00 0 ppm ; Z n wa s 491 0 ppm ; C u wa s 608 0 ppm ; an dC dwa s 17 9 ppm . A t thes e sites , heavy

meta l concentration s correlate dwith0 2 litte r laye r accumulations . A chang e fro mth e norma l wa s als o note din th e catio n exchang e capacit y an dp H o f th e soil . I n summary , th e result s o f thi s study 11 7 indicat e tha t th e dynamic s o f

forest-nutrien t

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a s asourc e o f

lea di n edibl e crops . En

viron . Sci . Tech . 4(3):226-229 , 1970 . 69 . Brewer , R . F . Lead . In: Diagnosti c Criteri afo r Plant s an d Soils . Chapman , H . D . (ed.) . Universit y o f Californi a Press , Riverside , Calif . 1966 . 70 . Baumhardt , G . R . an dL . F . Welch . Lea duptak e an dcor n growt hwit hsoil-applie dlead . J . Environ . Qual . 7(0:92-94,1972 . 71 . Warren , H . V . an dR . E . Delavault . Variation s i n th e cop per , zinc , lead , an dmolybdenu mcontent s o f som e vegeta ble s an dthei r

supportin g soils . Mem . Geol . Soc . (123):97-108 , 1971 . 72 . Cannon , H . L . Lea di n vegetation . In: Lea di n th e En

vironment . (T . G . Lovering , ed. ) U.S . Dept . o f Interior , U.S . Geol . Survey . Profess . Pape r No . 957 . 1976 . p . 53-72 . 73 . John , M . K . Lea davailabilit y relate dt o soi l propertie s an dextractabl e lead . J . Environ . Qual . /(3):295-298 , 1972 . 74 . Zimdahl , R . L . Lea di n soil s an dplants . In: Environmen

ta l Contaminatio n Cause db y Lead . Interi mRepor t Jan . 1 , 1974 , t o Dec . 31 , 1974 . (H . W . Edwards , ed.) , Nationa l Scienc e Foundation . NS FGrant s GI-348I3X 1 an d GI-44423 . 1975 . p . 332-342 . 75 . MacLean , A . J. , R . L . Halstead , an dB . J . Finn . Extrac

tabilit y o f

adde dlea di

n soil s an dit s concentratio n i n plants . Can . J . Soi l Sci . 49(3):327-334 , 1969 . 76. . Arvik , J . H . an dR . L . Zimdahl . Th e influenc e o f tem perature , pH , an dmetaboli c inhibitor s o n uptak e o f lea d b y plan t roots . J . Environ . Qual . 5(4):374-376 , 1974 . 77 . Rolfe , G . L . Lea duptak e b y selecte dtre e seedlings . J . En

viron . Qual . 2(0:153-157 , 1973 . 78 . Hassett , J . J . Capacit y o f selecte dIllinoi s soil s t o remov e lea dfro maqueou s solution . Comm . Soi l Sci . Plan t Anal . 5(6):499-505 , 1974 . 79 . Miller , J . E. , J . J . Hassett , an dD . E . Koeppe . Th e effec t o f soi l propertie s an dextractabl e lea dlevel s o n lea duptak e b y soybeans . Comm . Soi l Sci . Plan t Anal . 6(4):339-347 , 1975 . 80 . Miller , J . E. , J . J . Hassett , an dD . E . Koeppe . Th e effec t o f soi l lea dsorptio n capacit y o n th e uptak e o f lea db y corn . Comm . Soi l Sci . Plan t

Anal . 6(4):349-358 , 1975 . 81 . Hassett , J.J . Determinatio n o f lea dsorptio n capacitie s o f selecte dIllinoi s soil s usin g titratio n curves . Comm . Soi l Sci . Plan t

Anal . 7(2) : 189-195 , 1976 . 82 . Epstein , E . Minera l Nutritio n o f Plants : Principle s an d Perspectives . Joh n Wile y an dSons , Inc. , Ne w York . 1972 . p . 160-168 . 83 . Cox , W.J . an d D.W . Rains . Effecto f lim e o n lea d uptak e b y fiv e plan t

species . J . Environ . Qual . 7(2):167-I69 , 1972 . 84 . John , M . K . an dC . Va n Laerhoven . Lea duptak e b y let

tuc e an doat s a s affecte db y lime , nitrogen , an dsource s o f lead . J . Environ . Qual . 7(2):169- l 71 , 1972 . 85 . Miller , J . E. , J . J . Hassett , an dD . E . Koeppe . Interaction s oflea dan dcadmiu mo n meta l uptak e an dgrowt ho f cor n plants . J . Environ . Qual . 6(1):18-20 , 1977 . 86 . Olson , K . W . an dR . K . Skogerboe . Identificatio n o f soi l lea dcompound s fro mautomotiv e sources . Environ . Sci . Tech . 9(3):227-230 , 1975 . 87 . Jones , L . H . P. , S . C . Jarvis , an dD . W . Cowling . Lea dup tak e fro msoil s b y perennia l ryegras s an dit s relatio n t o th e suppl y o f

an essentia l elemen t (sulphur) . PI . Soil . 55:605-619 , 1973 . 8-1 588 . Antonovics , J. , A . D . Bradshaw , an dR . G . Turner . Heav y

meta l toleranc e i n plants . Adv . Ecol . Res . (London ) 7:1-85 , 1971 . 89 . Lepp , N . W . Th e potentia l o f tree-rin g analysi s for monitorin g heav y meta l pollutio n patterns . Environ . Poll . 9:49-61 , 1975 . 90 . Malone , C , D . E . Koeppe , an dR . J . Miller . Localizatio n o f lea daccumulate db y cor n plants . Plan t Phys . 54:388-394 , 1974 . 91 . Miles , C . D. , J . R . Brandle , D . J . Daniel , O . Chu-Der , P . D . Schnare , an dD . J . Uhlik . Inhibitio n o f photosyste mI I i n isolate dchloroplast s b y lead . Plan t Physiol . 49:820-825 , 1972 . 92 . Bazzaz , F . A. , G . L . Rolfe , an dP . Windle . Differin g sen sitivit y o f

cor n an dsoybea n photosynthesi s an dtranspira

tio n t o lea dcontamination . J . Environ . Qual . 5(2):156-158 , 1974 . 93 . Bazzaz , F . A. , R . W . Carlson , an dG . L . Rolfe . Th e effec t o f heav y metal s o n plants : Par t I . Inhibitio n o f

ga s ex chang e i n sunflowe r

b y Pb , Cd , Ni an dTi . Environ . Poll . 7:241-246 , 1974 . 94 . Wong , D. , an dGovindjee . Effect s o f lea dion s o n photo

syste mI i n isolate dchloroplasts : Studie s o n th e ractio n cente r P700 . Photosynthetica . 70(3):241-254 , 1976 . 95 . Miller , R . J . an dD . E . Koeppe . Accumulatio n an d physiologica l effect s o f lea di n corn . In: Trac e Substance s i n Environmenta l Health . Vol . IV . (D . D . Hemphill , ed. ) Universit y o f

Missour i Press , Columbia , Mo . 1970 . p . 186-193 . 96 . Bittell , J . E. , D . E . Koeppe , an dR . J . Miller . Sorptio n o f heav y meta l cation s b y cor n mitochondri aan dth e effect s o n electro n an denerg y transfe r reactions . Physiol . Plant . 50:226-230 , 1974 . 97 . Garber , K . Heav y metal s a s ai r pollutio n - Lea d- Zin c - Cadmiu m- Influenc e o n vegetation . VD I Ber . 205:50-57 , 1975 . 98 . Ganje , T . J . an dA . L . Page . Lea dconcentration s o f plants , soil , an dai r

nea r highways . Calif . Agr . 26(4):7-9 , 1972 . 99 . Ruhling , A . an dG . Tyler . Sorptio n an dretentio n o f heav y metal s i n th e woodlan dmoss , Hylocomiwn Splendens (Hedw. ) Br . e t

Sch . Oikos . 27(0:92-97 , 1970 . 100 . Tyler , G . Mos s analysis— ametho dfo r surveyin g heav y meta l deposition . In: Proc . 2n dInt'l . Clea n Ai r Congress , Washington , D.C . Academi c Press , Ne w York . Pape r SU-30F . 1971 . p . 129-132 . 101 . Tyler , G . Heav y metal s pollut e nature , ma y reduc e pro ductivity . Ambio . 7(2):52-59 , 1972 . 102 . Trollope , D . R . an dB . Evans . Concentration s o f copper , iron , lead , nickel , an dzin c i n freshwate r alga l blooms . En

viron . Poll . 77:109-116 , 1976 . 103 . Gale , N . L. , P . Marcellus , an dG . Underwood . Th e impac t oflea dminin g an dmillin g activitie s o n aquati c organisms . In: Trac e Contaminant s i n th e Environment , Proc . 2n d Ann . NSF-RAN N Trac e Contaminant s Conference . Asilomar , Pacifi c Grove , Calif . 1974 . p . 295-307 . 104 . Tornabene , T . G . an dH . W . Edwards . Microbia l uptak e oflead . Sci . /

76:1334-1335 , 1972 . 105 . Tornabene , T . G . an dH . W . Edwards . Effect s o f lea do n bacteria l membranes . In: Trac e Substance s i n Environ

menta l Health . Vol . VII . Proc . o f U . Missouri' s 7t hAnn . Conf . o n Trac e Substance s i n Environmenta l Health . Universit y o f

Missouri , Columbia , Mo . 1974 . p . 263-266 . 106 . Jarvie , A . W . P. , R . N . Markall , an dH . R . Potter . Chemi

ca l alkylatio n oflead . Nature . 255(5505):2I7-218 , 1975 . 107 . Schmidt , U . an dF . Huber . Methylatio n o f organolea dan d lea d(II ) compound s t o (CH3)4P b b y microorganisms . Nature . 259(5539):!57-158 , 1976 . 108 . Wood , J . M . Biologica l cycle s fo r toxi c element s i n th e en vironment . Sci . 755:1049-1052 , 1974 . 109 . Wood , J . M . Metaboli c Cycle s fo r Toxi c Element s i n th e Environmen t

- A Stud y o f

Kinetic s an dMechanism . In: Proc . Inter . Conf . o n Heav y Metal s i n th c Aquati c En

vironment . (P . A . Krenkel , ed. ) Pergamo n Press , Ne w York . 1975 . p . 105-112 . 110 . Wong , P . T . S. , Y . K . Chau , an dP . L . Luxon . Methylatio n o f lea di n th e environment . Nature . 255(5489):263-264 , 1975 . 111 . Devigne , J . P . Precipitatio n o f lea dsulfid e b y asoi l micrococcus . C . R . Hebd . Seance s Acad . Sci . Ser . D . 267(10):935-937 , 1968 . 112 . Hass , W . R . an dS . Miller . Effect s o f Variou s Metal s o n Aerobi c Organisms . II T Researc hInstitute , Chicago , Il

linois . Rep . No . IITR1-C82I3-2 . 1971 . 113 . Deason , W . D . Effect s o f Heav y Meta l Ion s o n Bacteri a Isolate dfro maMin e Pollute dRiver . Ph.D . Dissertation . Colorad o Stat e Univ. , Ft . Collins . 1970 . 114 . Hata , T . I n Norinsh o Sulsa n Koshusk o Kenky o Hokoku . (I n Japanese. ) 9:363 , 1960 . 115 . Bhuiya , M . R . H . an dA . H . Cornfield . Effect s o f additio n o f 100 0 pp mCU , NI , Pb , an dZ n o n carbo n dioxid e releas e durin g incubatio n o f soi l alon e an dafte r

treatmen t wit hstraw . Environ . Poll . 5:173-177 , 1972 . 116 . Cole , M . A . Lea dinhibitio n o f enzym e synthesi s i n soil . Appl . Environ . Microbiol . 55(2):262-268 , 1977 . 117 . Watson , A . P. , R . I . Va n Hook , D . R . Jackson , an dD . E . Reichle . Impac t

o f aLea dMining-Smeltin g Comple x o n th e Forest-Floo r

Litte r Arthropo dFaun ai n th e Ne w Lead-Bel t

Regio n o f

Southeas t

Missouri . Environmenta l Science s Division , Oa k Ridg e Nationa l Laboratory , Oa k Ridge , Tenn . ES D Pub . No . 881 , ORNL/NSF/EATC-30 . Jul y 1976 .

8-1 6

# 9 . QUANTITATIV E EVALUATIO N O F LEA D AN D BIOCHEMICAL INDICE S O

F LEA D EXPOSUR

E I N PHYSIOLOGICAL MEDI A I n thi s chapter , th e stat e o f th e ar t regardin g measuremen t

o f lea dan dbiochemica l marker s o f lea dexposur e i s summarized , an dth e accurac y an d precisio n o f

variou s method s o f

intra

- an dinter

laborator y compariso n ar e examined . Th e relativ e diagnosti c merit s o f

on e typ e o f

measuremen t

with respec t t o anothe r

—bloo dlea dversu s urinar y lead , fo r exampl e —ar e discusse delsewher e in th e docu

ment . 9. 1 GENERA L SAMPLIN G PROCEDURE S FO RLEA D I N BIOLOGICA L MEDI A Th e occurrenc e o f

lea din physiologica l medi ao f interes t in thi s discussio n i s at th e trac e level , eve n unde r condition s o f

marke dexposure . Therefore , a numbe r o f sampl e collectio n an dhandlin g precau tion s ar e calle dfor , bot ht o minimiz e los s o f lea d fro msample s an dt o avoi dth e contaminatio n o f sample s b y thi s ubiquitousl y distribute delement . Sample-gatherin g problem s ar e o f specia l concer n in bloo dlea dscreenin g program s i n whic hgrea t number s o f

sample s mus t

b e gathered , transported , an dprocesse din th e shortes t possibl e time. 1 Sampl e collectio n detail s fo r

bloo dlea dan dothe r

biologi

ca l indicator s o f

exposur e hav e bee n reviewe din th e clinica l literature. 2 I n bloo dstudie s it

i s ofte n desirabl e t o us e capil

lar y bloo db y finge r pric k instea do f

venou s puncture , especiall y whe n youn g childre n ar e in

volved . A numbe r

o f studie s hav e show n tha t capill

ar y an dvenou s bloo dar e essentiall y identica l in lea dcontent : Mitchel l e t al. 3 obtaine dacorrelatio n facto r o f 0.92 . However , it

shoul db e emphasize d tha t suc hresult s ca n b e achieve donl y whe n extrem e car e i s use di n cleanin g th e skin , an dwhe n con taminatio n o f

capillar y tube s an dsyring e i s avoided . A numbe r

o f worker s hav e use dfilte r pape r disc s fo r bloo dsampl e collectio n a s a n alternativ e t o han

dlin g discret e bloo dvolumes . Th e pape r fo r thi s purpos e mus t

b e selecte dfo r

uniformit y o f

manufac

ture , lo w lea dcontent , an dunifor mbloo ddispersal . I n th e method s o f

Cerni k an dSayer s involvin g lea dworkers, 4

- 5 fo r example , whol e bloo dobtaine d b y finger

pric k i s spotte dont o Whatma n No . 4 qualitativ e paper . Eithe r 9.0-m mo r

4.0-m mdisc s ar e the n punche dou t

an danalyze db y th e Delve s cu p microtechniqu e o r th e carbon-cu p flameless atomi c absorptio n procedure . Thes e method s corre lat e wel l withbloo dobtaine db y venou s puncture . Joselo w an dBogden 6 hav e employe damicro

metho dfo r

routin e mas s screenin g o f childre n usin g apape r disc-in-Delves-cu p technique . Capillar y bloo di s allowe dt o dro p ont o a n 8.2-c mdis c o f Schleiche r

an dSchwel l No . 90 3 filter pape r s o a s t o formaspo t

somewha t

large r tha n 1/

4 in . in diameter , an ddisc s o f

1/4-in . diamete r

ar e punche d ou t directl y int o previousl y conditione dDelve s cups . A correlatio n coefficien t o f 0. 9 wa s obtaine d whe n result s o f

thi s metho dwer e compare dwit ha macroprocedur e usin g venou s bloo dan dth e pro cedur e o f

Hessel. 7 Coo k e t al., 8 in thei r

investigatio n o f

capillar y bloo dcollecte do n pape r an do f bloo dvolum e gathere db y venou s puncture , obtaine dacorrelatio n approachin g 0.8 . Puncture-sit e preparatio n i s als o importan t in sampling . Marcu s e t

al. ' repor t

tha t apreliminar y cleanin g wit hethanoli c citri c aci dsolutio n followe d b y a70-percen t

ethano l rins e i s satisfactory , wherea s Cook e e t al. 8 chos e t o emplo y avigorou s scrubbin g wit hlow-lea dsoa p solutio n an ddeionize dwate r rinsing . A secon dprecautio n wit hfinger-prick samplin g i s th e wa y in whic hth e bloo dflow i s expedite dfo r sampling . Gravit y flo w o r direc t uptak e (filte r paper ) i s preferabl e t o squeezin g th e finge r tip , a s har dsqueezin g migh t

dilut e th e bloo ddro p wit h tissu e fluid . Furthe r precaution s includ e th e us e o f polypropylen e syringes 9 wit hneedle s o f stainles s stee l an dpolypropylen e hub s fo r punctur e sampling . Urine-sampl e collectio n require s acid-washe d plasti c container s (an dcaps ) an dshoul dinclud e a low-lea dbacteriocid e if sample s ar e stored . 9- 1P.2 7



### Hard

- an dsoft-tissu e gatherin g fro mlaboratory animal s o r

huma n source s entai l surfac e debride

ment o f ambient leadencountere di

n th e proces s o

f sampling . Hai r

cleanin g befor

e analysi s ma

y b e car rie dou t vi ath e metho do

f Hamme r e t al.; 1 0 

### bon e an dteet hma y b e given aquic k

rins e i n EDT A solu

tion . Wit hsof t tissue , th e oute r

laye r ma y b e remove do r

asegmen t of underlyin g matte r

excised . Fo r organ s o

f heterogeneou s morpholog y sucha s kidney , i t ma y b e more desirabl e t o subject th e sampl e t o aquic k

rins e i n a n ioni c chelant , sucha s EDTA , that

doe s no t penetrat e beyondth e oute r membrane . Regardles s o

f specifi c methodolog y employed , al l reagent s usedi

n leaddetermination s i

n biological medi ashoul db e certifie dfo r low-leadcontent ; and sample s shoul db e store di n amanner

that minimize s leadcontaminatio n fro

mai r o r surfaces . Standar d leadsolution s shoul db e prepare dfrequently , eithe r fro mstock solution s fro

manalyticall y certifie d source s o r fro mth e pur e metal . Solutio n preparatio n i n glas s shoul db e minimized , particularly whe n analysi s i s a

t th e sub-part-per-millio n level . 9. 2 BLOO D LEA D Th e first generall y accepte dpractic e fo r measur ing leadi

n bloo dan dother

biological medi ain

volve daspectrophotometri c techniqu e base don th e bindin g o f leadwit hachromogeni c agent

t o yiel da chromophori c product . I n thi s connection , th e classi c ligatin g agent

ha s been dithizone-1 , 5

- diphenylthiocarbazone . Th e lea ddithizonat e i s measure dspectrophotometricall y a t 51 0 nm . Tw o reliabl e variation s ofth e spectrophotometri c techniqu e whe

n dealin g wit

hleadconten t

o f 1 t o 1 0 pp mar e th e USPH S andAPH A procedures . Th e USPH S assay 9 

### i s adouble-extraction , mixed

colo r procedure havin g bismut ha s th e chief

inter

ferent . Bloo d(an durine ) sample s ar e wet-ashe d using concentrate dnitri c aci dcertifie da s t o low

leadcontent . Afte

r diges t treatmen t

wit hhydrox

ylamin e an dsodiumcitrate , th e p H i s adjuste dt o 9 t o 10 , an dcyanid e io

n i s added . Formatio n an dex tractio n of

lea ddithizonat e i s carrie dou t usin g a chlorofor msolutio n o

f dithizone . Leadi s the n re-ex tracte dint o dilut e nitri c aci d(1:9 9 water) , andth e aqueou s layer

i s treate dwit

hammonia-cyanid e solu

tio n an dre-extracte dwit hdithizone-containin g chloroform . Th e organi c extract s ar e readi n a spectrophotomete r

a t 51 0 nm . Althoug hbismut hin

terferes , thi s element

i s encountere dinfrequentl y i n biological media . Th e APH A procedure " varie s fro mthat de

scribe dabov e mainly i n permittin g removal o f bismut ha t pH 3. 4 as th e dithizonate . A t present , th e colorimetri c metho dha s been largel y supplante db

y tw o othe r

techniques : atomi c absorptio n (AA ) spectrometry i n al l it s variation s an danodi c strippin g voltammetry (ASV) . Ofthes e tw o analytical approaches , th e mor e tech

nicall y popular , b

y far , i s A A spectrometry , whichi s usedfo r bot hmacro - an dmicro-scal e analyses . Th e theoretica l basi s fo

r A A an dit s instrumental desig n ar e beyon dth e scop e of thi s presentation ; basi c review s ar e provide db

y Christian an dFeldman 1 2 

### andb y L'Vov,' 3 

### however . Macro-scal e A

A analysi s involve s direc t aspira

tio n o f suitabl y treate dlead-containin g sample s int o aflame fo

r lead-ato mgeneratio n an dexcitation . Micro-AA , whichi s being usedmore widely a s ac cessorie s an dinstrumen t

refinement s become com merciall y available , i s o

f tw o types : flame an dflame

less , wit hth e latte r

employin g thermoelectri c system s i n lieu o f aflame. O f th e flame microtechnique s for A A analysi s o

f bloo dsamples , th e mos t widely usedi s Delve s cu p procedure 1 4 

### i

n whichsmal l volume s of blood , 1 0 t o 100 fi\, ar e place di n lead-fre e nickel cruci

bles . Afte r th e organi c matri x i s destroyed , th e cup s ar e inserte dinto aflame. Th e Overall configuratio n o f th e syste mpermit s th e optica l pat ht o b e max imall y occupie db

y th e lea dato mpopulatio n origi

nall y present

i n th e sample . Destructio n o f th e organi c matri x in bloo dma y b e eithe r

partial , using hydroge n peroxide , or

total , wit hpre-ignitio n ofth e organi c matte r

cause db y placin g th e cup s nea

r th e flame. 15 

### Increasin g us e i s being mad e o f flameles s A A , par ticularl y th e heate dgraphit e furnac e accessory , whereb y volume s o

f bloo dar e reduce dt o — - 1 /nl , an dals o whereb y in-situ destructio n o f organi c mat te r ma y b e achieved . Th e electrochemical techniqu e known a s ASV 1 6 

### i s also * comin g int o commo n us e i n anumber

o f laboratories , particularl y fo r bloo dandurin e lead analysis . A s develope db y Matso n an dRoe, 1 6 

### th e techniqu e involve s concentratin g a n ion sucha s divalen t leadon anegativ e electrod e durin g apre determine dplatin g tim e ( 5 t o 6 0 min ) followe db y polarity reversal andincreas e fo r short period s t o yiel dadiscret e curren t

pea k tha t i s proportiona l t o ion concentration . Als o i n curren t

us e ar e X-ray fluorescence spectrometry an dneutron-activatio n analysis , tw o sophisticate dinstrumenta l method s fo r trac e analysis . Th e considerabl e expens e o f th e equipment 9- 2an dth e amoun t o f operato r

expertis e involve d rathe r limi t thei r us e t o tha t

o f regiona l servic e facilitie s o r

centra l laboratories . Th e tw o method s hav e adistinc t

advantage , however , i n tha t the y per mi t multiple-elemen t

analysis , afeatur e tha t will b e o f increasin g importanc e a s mor e i s unveile dabou t th e comple x interaction s oflea dwit hothe r metal s in ma n an dothe r

organisms . 9. 3 URIN E LEA D Precaution s t o b e take n fo r urin e sampl e collec

tio n wer e note dearlier . Becaus e ofth e considerabl e amoun t o f ioni c matte r

in urine , it

i s usuall y necess ar y t o manipulat e urin e sample s i n variou s way s befor e analysis . Al l o f th e method s employe dfo r bloo dlea d analysi s a s describe dabov e ma y als o b e applie dt o assessmen t

o f urin e lea dlevels . Care , however , shoul db e exercise din th e analysi s o f urin e sample s fro mpatient s undergoin g chelatio n therapy , wit h specia l attentio n t o ho w aspecifi c procedur e will ac commodat e o r

b e interfere dwithb y lea dexcrete da s acomplex , e.g. , lead-EDTA . Prio r ashin g o f

urin e sample s wil l minimiz e complication s i n thi s regard , bu t partia l degradatio n o r n o prio r treatmen t

migh t necessitat e co-analysi s o f lea din th e comple x form fo r standards . 9. 4 SOFT-TISSU E LEA D Becaus e ofth e natur e o f thi s medium , i t

i s usuall y necessar y eithe r

t o as ho r

t o solubiliz e tissu e sam ples . Wet-ashin g i s rapi dan davoid s lea dlos s vi a volatilization , bu t

i t require s us e o f

corrosiv e acid s an dprocedura l car e t o avoi dcontaminatio n o f reagent s an dothe r

problems . Dr y ashing , o n th e othe r hand , i s simpl e an duse s n o contaminatin g reagents . Th e drawback s ar e mainl y thos e o f lea d volatilizatio n an dretentio n ofth e elemen t in refrac

tor y residues . Newe r

technique s o f

ashin g includ e (1 ) low-temperatur e ashing , in whic hdr y sample s ar e mineralize di n an evacuate dchambe r tha t i s bathe di n a n energy-ric hplasm avi ar- f discharg e i n a n oxyge n stream , an d(2 ) us e o f th e combustio n bomb , i n whic hsample s ar e heate din aci da n at ele

vate dtemperatur e i n aseale diner t vessel . A newe r metho do f

tissu e handling , solubilization , entail s th e treatmen t

o f sample s wit hquaternar y am moniu mcompound s an danalysi s o f aliquots , chiefl y b y A A spectrometry. 1 7 Th e bul k o f th e curren t

literatur e center s o n th e us e o f atomi c absorptio n spectrometr y a s th e metho d o f choic e fo r

assessin g lea dlevel s in sof t tissue . 9. 5 HAI RLEA D

A n attractiv e featur e o f th e clinica l us e o f

hair

lea dlevel s i s it s noninvasiv e natur e an dth e feasibilit y o f

assemblin g aroug htim e fram e fo r lea d exposur e b y isolatin g discret e segment s o f th e tota l hai r length . A seriou s drawbac k

in hai r analysis , however , i s th e leve l o f

contaminatio n b y ambien t ai r lead , lea d in hai r preparations , etc. , a s discusse db y Hamme r e t al.'°Hai r measurement s withou t prio r treatmen t

o f th e sampl e includ e bot hexogenou s an dendogenou s sources . Example s ofth e forme r ar e dyes , shampoos , sweat , an ddust . Pre-analysi s hai r washin g wit h detergen t an dEDT A remove s mos t ofth e externall y foun dlead ; bu t

ther e i s stil l n o definitiv e wa y t o determin e whethe r

an y cleanin g techniqu e remove s th e contaminatio n portio n o f lea dan dleave s th e in

terna l lea dconten t

undisturbed . Hai r i s usuall y wet-ashe dbefor e analysis , an dth e diges t i s dilute dan danalyze db y A A spectrometry . Becaus e relativel y hig hlevel s o f lea dar e encoun tere din hair , smal l sampl e size s ca n b e use dwhe n a sensitiv e procedur e suc ha s A A spectrometr y i s employed . 9. 6 LEA D I N TEET H AN D BON E Th e biochemica l significanc e o f lea dlevel s i n teet han dbon e i s discusse delsewhere . Fro ma n analytica l standpoint , bon e sample s ar e usuall y ob

taine dfro mexperimenta l anima l studies . Bon e sam ple s mus t firs t b e debride do f

muscl e an dconnectiv e tissu e an dchemicall y ri do f surfac e lea dcontamina

tio n b y rinsin g wit hEDT A o r othe r chelan t solution . Bon e an dteet har e usuall y wet - o r dry-ashe d befor e analysis , an dth e relativ e merit s o f thes e mineralizin g procedure s ar e a s note dabov e wit hsof t tissu e assays . Becaus e ofth e hig hminera l conten t o f bon e an dteeth , car e mus t b e take n t o avoi d spectrochemica l interferenc e b y calcium , phosphate , etc . Th e relativel y hig hlevel s o f lea din thes e tw o har dtissues , however , permi t dilutio n ofth e sample s fo r testing . Becaus e th e effec t o f th e hig hminera l conten t o n analytica l signal s i s probabl y sufficien t t o preclud e th e us e o f

simpl e aqueou s lea dstandards , i t i s advisabl e t o emplo y worku p solution s o f bon e sample s tha t

hav e first

bee n analyze dfo r

lea dcon ten t an dt o whic hknow n amount s o f lea dfro ma stoc k solutio n ar e the n added . Matri x standard s pre pare din thi s fashio n ar e assume dt o reflec t th e in

fluenc e o f

minera l conten t

o n al l o f

th e samples . 9- 3P.2 9

9. 7 COMPARATIV E STUDIE S O F METHOD S FO RMEASUREMEN T O F LEA D I N BIOLOGI CA L MEDI A I n a n interlaborator y stud y o f th e USPH S col

orimetri c metho dfo r

lea din bloo dan durine , Keena n e t

al. 1 8 reporte dth e result s fro m1 0 partici

patin g laboratories . Fo r blood , amea n lea dvalu e o f 2 6 ± 0.8 2 /ig/d l wa s obtained ; spike dsample s gav e virtuall y identica l correspondenc e amon g th e groups . Urin e sample s withlea dadde dgav e value s fro mth e reportin g group s withamea n o f 67 9 ± 5. 5 /xg/liter . Microscal e A A technique s fo r whole-bloo dlea d hav e bee n foun dt o sho w goo dcorrespondenc e with result s obtaine dusin g conventiona l flame pro cedures. 19

- 2 0 Matson 2 1 ha s reporte dgoo dcorrelation s fo r lea d level s in bloo dan durin e whe n comparin g AS V with acolorimetri c an da n A A procedure . Similarly , Horiuch i e t

al.2 2 saw littl e differenc e in lea dlevel s fo r bloo dan durin e whe n contrastin g ASV , A A , an d polarography . Interlaborator y studie s o f variou s method s fo r lea danalysi s o f

biologica l medi ahav e yielde dsome wha t disappointin g results. 23 * 2 5 I n arecen t stud y in

volvin g 6 6 laboratorie s throughou t Europe , bloo d an durin e determinatio n varianc e wa s observe dt o b e unacceptabl y high. 2 5 Presently , th e Cente r

fo r Diseas e Contro l (CDC ) i s carryin g o n amonthl y proficienc y testin g progra m fo r bloo dlea dinvolvin g approximatel y 20 0 laboratories . Result s ar e mad e availabl e throug h monthl y report s fo r

analysi s o f

bovin e bloo dsam ples. 2 6 Th e criterio n use db y CD C fo r assessin g un satisfactor y performanc e is : greate r tha n 1 5 percen t relativ e deviatio n at

level s o f 4 0 figld\ o r

abov e an d greate r tha n 6 Mg/dl at

lowe r levels . I n arecen t

CD C repor t

(Surve y 1977I) 2 7 coverin g 13 0 laboratorie s fo r

testin g an d2 6 referenc e laboratorie s usin g thre e bovin e bloo dsample s (cow s fe dlea dacetate) , 7 2 percen t o f th e teste dlaborato

rie s wer e withi n th e acceptabl e rang e fo r asampl e havin g amea n o f

16.6/u.g/dl . Th e acceptabl e percen tag e wa s lower , interestingly , at highe r sampl e mean s o f 48. 2 an d54. 6 /ug/d l (6 4 an d6 7 percent , respectively) . Whe n result s wer e tabulate da s afunc

tio n o f method , th e Delve s cu p A A spectrometri c an dAS V method s furnishe dth e smalles t coefficient s o f variation . A numbe r

o f othe r proficienc y program s ar e pre sentl y operatin g in th e Unite dStates , an dth e result s o f thes e hav e bee n included , alon g withth e Euro

pea n program , in arecentl y publishe dmonograp h b y Pierc e e t al. 2 Thes e sam e author s describ e th e stat e ofth e ar t

criticall y an doffe r

som e recommen dation s fo r

improvin g th e qualit y o f bloo dlea d analyses : 1 . Ever y laborator y shoul dhav e establishe d quality-contro l procedures . 2 . Contro l procedure s shoul dinclud e replicat e analyses , recover y o f

know n addition s o r spikes , participatio n in interlaborator y tests , an danalyse s o f

know n materials . 3 . Testin g sample s tha t th e analyst s analyz e blin dshoul db e use dt o minimiz e bias . I t ha s bee n suggested 2 8 tha t th e acceptabl e agree ment s in bloo dlea dlevel s foun dwhe n asingl e laborator y employ s differen t technique s compare d wit hth e wid e varianc e foun dwhe n differen t laboratorie s emplo y differen t method s o n portion s o f commo n bloo dsample s relat e primaril y t o pre paratio n an dstat e o f

th e bloo dsample s befor e an d durin g distributio n an dsubsequen t analysis . Th e result s o f

Grime s an dcoworkers 2 9 bea r thi s ou t becaus e alarg e numbe r o f carefull y controlle d bloo dsample s analyze db y thei r laboratories , usin g th e pape r dis c technique , provide dresult s tha t com pare dwel l withthos e o f othe r laboratorie s usin g othe r instrumentatio n withth e dis c technique . 9. 8 MEASUREMEN T O F URINAR Y 8-AMINOLEVULINI C ACI D (ALA-U ) Som e comment s regardin g sampl e collectio n for ALA- U ar e necessary . AL A i s stabl e in acidifie d urin e (p H 1 t o 5) , s o tha t aceti c o r hydrochlori c aci d additio n i s satisfactor y at th e tim e o f

sampl e collec

tion . If sample s ar e store din th e dar k at 4°C , th e AL A conten t

remain s relativel y constan t fo r severa l months. 3 0 ALA- U measuremen t

usuall y entail s th e classi c metho do f

Mauzeral l an dGranick. 3 1 I n thi s ap proach , ALA- U i s condense dwit ha/3-dicarbony l compoun dsuc ha s acetylaceton e o r ethy l acetoace tat e t o yiel dasubstitute dpyrrol e derivative ; thi s in

termediat e i s the n cause dt o reac t withEhrlic h reagen t (p-dimethylaminobenzaldehyde ) t o yiel dan intens e ioni c chromophore . Thi s procedur e i s no t specifi c fo r

ALA-U , however , sinc e aminoaceton e interferes . Thoug hth e significanc e o f suc hinter

ferenc e i s margina l whe n ALA- U level s ar e markedl y elevated , it

become s ver y importan t whe n onl y sligh t

elevation s o f

ALA- U ar e bein g measured . First , urin e sample s ar e chromatographe do n ion

exchang e resi n column s (Dowex-2) , th e ALA- U bein g co-elute dwithure ausin g wate r a s eluent . Eluat e transfe r

t o aDowex-5 0 colum n i s followe d 9- 4P.3 0

b y sequentia l elutio n withwate r t o remov e th e ure a an dthe n wit hacetat e solutio n t o permi t remova l o f th e ALA-U . Treatmen t

withacetylaceton e an dheat

in g t o effec t

complet e condensatio n i s followe db y treatmen t

o f sampl e aliquot s withmodifie dEhrlic h reagen t (p-dimethylaminobenzaldehyd e in per chloric/aceti c acid) . Th e resultin g chromophori c sal t i s allowe dt o achiev e maximu mintensit y (ca. 1 5 min ) afte r

whic hth e sampl e i s rea din aspectro photomete r

a t 55 3 nm . Th e detectio n limi t i s 3 ^moles/lite r

urine , an dchromophor e stabilit y i s limite dt o abou t

1 5 min . A numbe r

o f modification s t o th e abov e basi c ap proac hhav e bee n reported . Severa l report s attemp t t o tak e int o accoun t

th e interferenc e pose db y aminoacetone . Th e quantitativ e correction s t o b e use dar e describe db y th e author s o f thes e re ports. 32

- 3 3 Th e initia l isolatio n o f

porphobilinoge n i s omitte d (i n case s wher e porphyri ai s no t suspected ) in th e modificatio n o f

William s an dFew, 3 4 in whic hacor relatio n o f

0.9 9 wa s observe dwit hth e referenc e techniqu e usin g sample s fro m3 9 lea dworkers . Dos s an dSchmidt 3 5 repor t

tha t us e o f commerciall y avail

abl e dua l ion-exchang e column s offer s result s tha t compar e favorabl y wit hth e Mauzeral l an dGranic k method. 3 1 Th e assa y ha s bee n automate dwithgoo dcorres pondenc e o f

result s t o th e manua l metho din th e laboratorie s o f

Grisle r e t al. 3 6 an dLauwery s e t

al. 3 7 I n anothe r

variatio n ofth e ALA- U procedure , th e metho do f

Schlenke r

e t al. 3 8 remove s aminoaceton e whic hinterfere s wit hth e assay . I n th e procedur e o f MacGe e e t

al., 3 9 urinar y an dbloo dAL A i s deter

mine db y gas-liqui dchromatography , ahighl y specifi c technique . 9 9 MEASUREMEN T O F 8-AMINO - LEVULINI C ACI D DEHYDRATAS E (ALA-D ) Locate din erythrocytes , 8-aminolevulini c aci d dehydratas e (ALA-D ) catalyze s th e conversio n o f AL A t o porphobilinoge n i n th e hem e biosyntheti c pathway . It s inhibitio n b y heav y metal s suc ha s lea d indicate s tha t

i t i s asulfhydry l enzym e an dals o form s th e biochemica l basi s fo r assessin g it s activit y in lead-expose dorganisms . Bloo dcollectio n require s th e us e o f low-lea d tube s containin g anticoagulant , wherea s fo r micromeasurement , bloo di s collecte di n a heparinize dmicrohematocri t tube. 4 0 Obviously , us e o f stron g chelants , suc ha s EDTA , a s anticoagulant s i s no t advisabl e becaus e competitio n fo r lea dma y reactivat e th e lead-inhibite denzyme . Minima l tim e laps e shoul doccu r betwee n collec

tio n an denzym e assay—n o mor e tha n 2 4 h r if sam ple s o f heparinize dbloo dar e hel dat 4°C . Th e chemica l basi s fo r

measurin g enzym e activit y involve s spectra l measuremen t o f th e amoun t

o f porphobilinoge n generate dfro mALA , th e porpho

bilinoge n bein g condense dwit hp-dimethyl

aminobenzaldehyd e t o yiel dachromophor e tha t i s measure dat

55 3 nm . Mercur y (II ) i s employe dt o minimiz e th e interferenc e effec t o f sulfhydry l en titie s presen t

in th e medium . Th e micrometho do f

Granic k

an dco-workers 4 0 require s onl y 5 fi1 o f

whol e bloo dan dappear s t o b e o f valu e in ascreenin g program . Enzym e incubatio n i s don e at 37° C fo r abou t 6 0 min ; AL A ofth e highes t possibl e purit y i s necessar y a s asubstrate . Terminatio n o f

th e reactio n (enzym e activity ) i s don e vi atrichloroaceti c acid . Th e activit y o f

th e enzym e ma y b e calculate din tw o ways: 40

- 4 1 Activit y = AOD 553 (sample-tissu e control )

138,00 0 nMo l HC I

= AOD 5 „(t 6 0 '-t 0 ') x

PBG/m l RBC/h r 0 0 HC L x 131.4 8 nMo l PBG/m l RBC/mi n I n th e Europea n standardize dmetho dfo r AL A determination 4 2 aime dspecificiall y at enzym e level s in bloo dcorrespondin g t o lo w level s o f exposur e t o environmenta l lead , incubatio n o f th e enzym e in thre e aliquot s o f

bloo d(0. 2 ml coole dt o 4°C ) i s car rie dou t in th e presenc e o f

exces s 8-aminolevulini c acid . A n aliquo t

blan k i s als o carrie dthroug hth e procedure . Hemolysi s o f th e cell s an dincubatio n withsubstrat e i s followe db y quenchin g wit hmer curi c chloride-trichloroaceti c aci dsolution . Centrifugatio n an dtreatmen t wit hmodifie d Ehrlich' s reagen t

i s followe da t

5 mi n b y absorbanc e measurement . Bloo dsample s ar e preferabl y ru n withi n 3 h r

an din n o cas e afte r

2 4 h r whe n hel dat 4°C . I n astud y b y Granic k

e t al. 4 3 th e activit y o f

ALA

D befor e an dafte r

treatmen t

wit hdithiothreoto l (DTT ) i s determined . Th e DT T (adde din vitro, 2 0 mM ) provide s -S H group s an dreactivate s th e enzym e completel y at

al l concentration s o f

bloo d lead . Becaus e DTT-reactivate dALA- D yield s tota l enzym e activity , variatio n in level s o f th e unacti

vate denzym e ma y b e normalize db y determinatio n ofth e rate s o f

bot hactivities . Henc e aperso n havin g 9- 5P.3 1

ahig hALA- D fo r

geneti c reason s a t

agive n bloo d leve l o f lea dwil l hav e relativel y hig hactivit y fo r bot hactivate dan dnonactivate denzyme , an dth e ac tivit y rati o wil l depen dles s o n geneti c factor s tha n o n lea dinhibition . Consequently , correlatio n i s markedl y improved . Thi s stud y als o show s tha t in

hibitio n b y lea di s o f

th e noncompetitiv e type . 9.1 0 MEASUREMEN T O F FRE E ERYTHRO CYT E PROTOPORPHYRI N (FEP ) Anothe r reactio n tha t

lea dinhibit s i n th e huma n hem e biosyntheti c pathwa y i s hem e formation . A s a resul t o f blockin g thi s reaction , porphyrins , particu

larl y protoporphyri n I X (actuall y zinc-pro

toporphyrin) , accumulat e i n th e erythrocytes . Measuremen t

o f protoporphyri n I X specifically , o r al l erythrocyt e prophyrin s together , i s generall y referre dt o a s th e fre e erythrocyt e protoporphyri n (FEP ) test . Th e spectrochemica l propertie s o f FE Ptha t

form th e basi s fo r

it s measuremen t

includ e it s labilit y t o ligh t an dstron g acids , it s meta l coordinatin g ability , it s possessio n o f

a n absorptio n spectru min th e Sore t ban dregion , an dit s marke dintensit y o ffluorescence . Spectra l method s used , however , mus t tak e int o accoun t

th e fac t tha t copro - an duroporphyri n provid e considerabl e interferenc e in FE Pmeasure ment . Althoug hbot habsorptio n spectrophotometri c an dfluorometric method s ma y b e employe dfo r FE P assessment, 444 6 fluorometric technique s carrie dou t o n amicroscal e ar e mor e frequentl y use dbecaus e o f th e relativel y cumbersom e natur e o f absorptio n spectrometr y i n term s o f tim e an dmaterials . Thes e microfluorometri c techniques , in particular , provid e arapid , relativel y accurat e mean s o f screenin g pediatri c populations . I n th e microtechniqu e o f Granic k e t al. 47 , severa l microliter s o f

whol e bloo dar e place din 1-m l tes t tube s tha t

als o serv e a s fluorometri c cuvettes . Addi

tio n o f ethy l acetate/glacia l aceti c aci d(2:1 ) i s the n rapidl y followe db y treatmen t wit h0.5 N HC I an d vigorou s shaking . Th e acidi c phas e (botto mlayer ) contain s th e bul k

ofth e porphyrins . Th e cuvette s ar e scanne dove r

th e rang e 56 0 t o 68 0 nm , usin g excita

tio n a t 40 0 nm . Th e rati o ofth e two-ban dmaxim aat 60 5 an d65 5 nmi s measure dfo r eac hsampl e wit ha rati o o f 2: 1 indicatin g onl y FEP . An y lesse r valu e in

dicate s copro - and/o r

uroporphyrins . I n th e latte r case , a n extractio n wit h0.05 N HC I o n analysi s of a secon dsampl e remove s copro - an duroporphyrin . Th e techniqu e o f

Piomelli, 4 8 usin g 2 0 fi\ o f bloo d adde dt o a5-percen t

Celit e suspensio n i n saline , use s essentiall y th e sam e initia l extractio n procedure s a s thos e note dabove , bu t it i s varie dt o emplo y 1.5 N HC I t o generat e th e fluorescin g aci dlayer . Measuremen t

i s a t 61 0 nman dexcitatio n a t 40 5 nm withcoproporphyri n employe da s th e standard . Observin g tha t

FE Pi s actuall y th e zin c comple x (ZPP) , Lamol aan dcoworkers 4 9 hav e devise da rathe r rapi dan dsensitiv e fluorometri c procedur e in whic h2 0 fi\ o f

whol e bloo di s worke du p in a detergent-phosphat e buffe r solutio n (dimethyl

dodecylamin e oxide ) an dfluorescenc e measure dat 59 4 nmwithexcitatio n at 42 4 nm . I n th e procedur e o f

Chisol man dBrown, 5 0 whic h ha s bee n evaluate da s aselecte dmetho db y Schwart z an dPiomelli , 2Q-fi\ bloo dvolume s ar e treate dwit h ethy l acetate/aceti c aci dsolutio n (3:1 ) an dagitate d fo r 3 0 sec . Afte r

centrifugation , th e layer s ar e ex tracte dwit h3 N HCI , an dth e aci dlaye r i s dilute d withmor e 3 N HCI . Th e aci dextract s ar e analyze d spectrofluorometricall y withcoproporphyri n em ploye da s th e quantitatin g standard . A portabl e hematofluoromete r tha t utilize s front

fac e optics , interna l standards , an dbuilt-i n com putationa l capabilitie s permit s th e assessmen t o f erythrocyt e zin c protoporphyri n (ZPP) . A s develope db y Bel l laboratories 5 1 an dsubsequentl y mad e availabl e commercially, 5 2 th e apparatu s per mit s th e analysi s o f

adro p o f

bloo dapplie dt o a cove r sli p directl y fro mfinge r pricking . Th e ZP P leve l {fig ZPP/d l blood ) i s automaticall y calculate d an ddisplaye do n adigita l readout . A numbe r

o f micromethod s fo r

FE Panalysi s hav e bee n criticall y evaluate db y Hann ae t al . 53 : Doubl e extractio n withethy l acetate/aceti c acid-HCl, 4 8 singl e extractio n withethanol , singl e extractio n wit h acetone, 5 4 an ddirec t

solubilizatio n wit hdetergen t buffer. 4 9 O f

these , th e ethy l acetat e an dethano l pro cedure s wer e satisfactory ; th e complet e extractio n o f FE Pmake s th e forme r

th e techniqu e o f

choic e whe n a n absolut e valu e rathe r tha n technica l simplicit y i s o f primar y concern . 9.1 1 REFERENCE S FO RCHAPTE R9 1 . Marcus , M. , M . Hollander , R . E . Lucas , andN . C . Pfeiffer . Micro-scal e bloo dlea

ddetermination s i

n screening : Evaluatio n o

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tional Lea

dZin c Researc hOrganization , Inc. , Ne w York . 1976 . 3 . Mitchell , D . C , K

. M . Aldous , andF . J . Ryan . Mas s screenin g fo

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sorptio n technique . Application s t o th e supervisio n o f lea d workers . Brit . J . Ind . Med . 28:392-398 , 1971 . 5 . Cernik , A . A . Determinatio n o f bloo dlea dusin g a4. 0 m m pape r punche ddis c carbo n cu p samplin g technique . Brit . J . Ind . Med . J/:239-244 , 1974 . 6 . Joselow , M . M . an dJ . D . Bogden . A simplifie dmicr o metho dfo r

collectio n an ddeterminatio n oflea di n bloo d usin g apape r

disk-in-Delve s cu p technique . At . Absorp . Newsletter . 77:99-101 , 1972 . 7 . Hessel , D . W . A simpl e an drapi dquantitativ e determina

tio n oflea di n blood . At . Absorp . Newsletter . 7:55 , 1968 . 8 . Cooke , R . E. , K . L . Glynn , W . W . Ullmann , N . Lurie , an d M . Lepow . Comparativ e stud y o f amicro-scal e tes t

fo r lea din blood , fo r

us e i n mas s screenin g programs . Clin . Chem . 20(51:582-585 , 1974 . 9 . Lead : Airborn e Lea di n Perspective . Nationa l Academ y o f Sciences , Washington , DC . 1972 . 10 . Hammer , D . I. . J . F . Finklea , R . H . Hendricks . C . M . Shy . an dR . J . M . Horton . Trace-meta l concentration s i n huma n hair . In: Helen aValley , Montana . Are aEnviron

menta l Pollutio n Study . U.S . Environmenta l Protectio n Agency . Researc hTriangl e Park , N.C . Pub . No . AP-91 . 1972 . p . 125-134 . 11 . Method s fo r

Determinin g Lea di n Ai r an dBiologica l Materials . America n Publi c Healt hAssociation , Ne w York . 1955 . 6 9 p . ' 12 . Christian , G . D . an dF . J . Feldman . Atomi c Absorptio n Spectroscopy : Application s i n Agriculture , Biolog y an d Medicine . Wiley-Interscience , Ne w York . 1970 . 13 . L'Vov , B . V . Atomi c Absorption : Spectrochemica l Analysis . J . H . Dixo n (tr) . America n Elsevie r Publishin g Co. , Ne w York . 1971 . 14 . Delves , H . T . A micro-samplin g metho dfo r th e rapi d determinatio n o f

lea di n bloo db y atomic-absorptio n spectrophotometry . Analyst . (London ) 95:431-438 , Ma y 1970 . 15 . Ediger , R . D . an dR . L . Coleman . A modifie dDelve s cu p atomi c absorptio n procedur e fo r th e determinatio n o f

lea d i n blood . At . Abs . Newsletter . 7/(2):33-36 , 1972 . 16 . Matson , W . R . an dD . K . Roe . Trac e meta l analyse s o f natura l medi ab y anodi c strippin g voltammetry . Anal . In

strum . 4:l'9-22 , 1966 . 1 7 . Murthy , L. , E . E . Menden , P . M . Eller , an dH . G . Petering . Atomi c absorptio n determinatio n o f zinc , copper , cad

miu man dlea di n tissue s solubilize db y aqueou s tetramethylammoniu mhydroxide . Anal . Biochem . 55(2):365-372 , 1973 . 18 . Keenan.R.G. , D.H . Byers , B . E . Saltzman , an dF . L . Hy

slop . Th e "USPHS " metho dfo r determinin g lea di

n ai r an di n biologica l materials . J . Am . Ind . Hyg . Assoc . 24( 5 ):481-491 , 1963 . 19 . Kubasik , N . P. , M . T . Volosin , an dM.H . Murray . Carbo n ro datomize r

applie dt o measuremen t o f lea di n whol e bloo db y atomi c absorptio n spectrophotometry . Clin . Chem . 7S(5):4I0^I2 , 1972 . 20 . Hicks , J . M. , A . N . Gutierrez , an dB . E . Worthy . Evalua

tio n o f th e Delve s micr o syste mfo r bloo dlea danalysis . Clin . Chem . 79(3):322-325 , 1973 . 21 . Matson , W . R . Rapi dsub-nanogra msimultaneou s analyses . Trac e Substance s i n Environ . Health . IV:396-406 , 1970 . 22 . Horiuchi , K. , S . Horiguchi , F . Takoda , an dK . Teramoto . A polarographi c metho dfo r th e determinatio n o f

asmal l amoun t o f lea di n biologica l materials . Osak aMed . J . /4:II3-I18 , 1968 . 23 . Keppler , J . F. . M . E . Maxfield . W . D . Moss , G . Tietjen . an dA . L . Linch . Interlaborator y evaluatio n o f th e reliabilit y o f

bloo dlea danalyses . J . Am . Ind . Hyg . Assoc . 57:412-429 , 1970 . 24 . Donovan , D . T. , V . M . Vought , an dA . B . Rakow . Laboratorie s whic hconduc t lea danalysi s o n biologi c specimens . Arch . Environ . Health . 2J(2): 1 11-113 , 1971 . 25 . Berlin , A. . P . De l Castilho , an dJ . Smeets . Europea n inte r compariso n programmes . In: Environmenta l Healt h Aspect s o f

Lead . Commissio n o f th e Europea n Com

munities , Centr e fo r

Informatio n an dDocumentation , Luxembourg . Ma y 1973 . p . 1033-1049 . 26 . Bloo dLea dProficienc y Testing . U.S . Departmen t o f Health , Education , an dWelfare , Cente r fo r Diseas e Con

trol , Atlanta . Ga . 1975 . 27 . Bloo dLea dProficienc y Testin g Program . U.S . Depart

men t o f Health , Education , an dWelfare , Cente r fo r Dis

eas e Control , Atlanta , Ga . Monthl y Repor t fo r March , 1977 . 28 . Lead : Environmenta l Healt hCriteri a3 . Worl dHealt h Organizatio n an dth e Unite dNation s Environmen t Pro

gramme , Geneva . 1977 . p . 59-65 . 29 . Grimes , H. . M . P . H . Sayers , A . A . Cernik , A . Berlin , P . Recht , an dJ . Smeets . Not e o n th e Lea dExposur e o f Children : Determination s Carrie dOu t o n Behal f

o f th e Commissio n i

n Wester n Ireland . Commissio n ofth e Euro

pea n Communities , Luxembourg . Repor t No . VF-I49I . 1975 . p . 7 . 30 . Haeger-Aronsen , B . Studie s o n urinar y excretio n o f 8

- aminolevulini c aci dan dothe r hae mprecursor s in lea d worker s an dlead-intoxicate drabbits . Scand . J . Clin . Lab . Invest . /2(Suppl . 47>—1-128 . 1960 . 31 . Mauzerall . D . an dS . Granick . Th e occurrenc e an ddeter

minatio n o f

8-aminolevulini c aci dan dporphobilinoge n i n urine . J . BioTchem . 2/9(0:435-446 , 1956 . 32 . Marver . H . S. . D . P . Tschudy . M . G . Perlroth . A . Colline , an dG . Hunter . Jr . Th e determinatio n o f aminoketone s i n biologica l fluids . Anal . Biochem . /4.-53-60 . 1966 . 33 . Urata . G . an dS . Granick . Biosynthesi s o f 8-aminoketone s an dth e metabolis mo f aminoacetone . J . Biol . Chem . 258(2):8ll-820 . 1963 . 34 . Williams , M . K . an dJ . D . Few . A simplifie dprocedur e fo r th e determinatio n o f urinar y 8-aminolevulni c acid . Brit . J . Ind . Med . 24:294-296 , Oct . 1967 . 35 . Doss . M . an dA . Schmidt . Quantitativ e determinatio n o f 8-aminolevulini c aci dan dporphobilinoge n i n urin e wit h ready-mad e ion-exchang e chromatographi c columns . Z . Klin . Chem . Klin . Biochem . 9:99-102 , 1971 . 36 . Grisler , R. . M . Genchi , an dM . Perini . Determinatio n o f urinar y 8-aminolevulini c aci db y continuou s flu x an dse quentia l automati c analyzers . Med . Lav . 60:678-686 , Nov . 1969 . 37 . Lauwerys . R. . R . Delbroeck , an dM . D . Vens . Automate d analysi s o f

8-aminolevulini c aci din urine . Clin . Chim . Acta . 40:443-447 . 1972 . 38 . Schlenker , F . S. , N . A . Taylor , an dB . P . Kiehn . Th e chromatographi c separation , determination , an ddail y ex cretio n o f

urinar y porphobilinogen , aminoacetone , an d delta-aminolevulini c acid . Am . J . Clin . Pathol . 42:349-354 . 1964 . 9- 7Hr*** "

39 . MacGee , J. , S . M . Roda . S . V . Elias , A . Lington , M . W . Tabor , an dP . B . Hammond . Determinatio n o f delta

aminolevulini c aci di n bloo dplasm aan durin e b y gas liqui dchromatography . Biochem . Med . 77:31-44 , 1977 . 40 . Granick , J . L. , S . Sassa . S . Granick , R . D . Levere , an dA . Kappas . Studie s o f

lea dpoisoning . I . Microanalysi s o f erythrocyt e protoporphyri n level s b y spectrofluorometr y i n th e detectio n o f

chroni c lea dintoxicatio n i n th e subclinica l range . Biochem . Med . 8:135-148 , 1973 . 41 . Weissberg , J . B. , F . Lipschutz , an dF . A . Oski . 8

- aminolevulini c aci ddehydratas e activit y i n circulator y bloo dcells : A sensitiv e laborator y tes t fo r th e detectio n o f childhoo dle dpoisoning . Ne w Eng . J . Med . 284(ll):565-569 . 1971 . 42 . Berlin . A . an dK . H . Schaller . Europea n standardize d metho dfo r

th e determinatio n o f 8-aminolevulini c aci d dehydrates e activit y i n blood . Z . Klin . Chem . Klin . Biochem . 72:389-390 , 1974 . 43 . Granick , J . L. . S . Sassa . S . Granick . R . D . Levere . an dA . Kappas . Studie s i n lea dpoisoning . II . Correlatio n betwee n th e rati o o f

activate dan dinactivate d8-aminolevulini c aci ddehydratas e o f

whol e bloo dan dth e bloo dlea dlevel . Biochem . Med . 8:149-159 . 1973 . 44 . Wranne , L . Fre e erythrocyte s copro - an dprotoporphyrin : A methodologica l an dclinica l study . Act aPediatrica . 49(Suppl . 124):l-78 . I960 . 45 . Heilmeyer . L . Ube r di e erythropoetische n porphyrien . Wie n Med . Wochschr . / 76:12-17 . 1966 . 46 . Langer , E . E. . R . G . Haining . R . F . Labbe . P . Jacoby . E . F . Crosby , an dC . A . Finch . Erythrocyt e protoporphyrin . Blood . 40:112-128 . 1972 . 47 . Granick , S. . S . Sassa . J . L . Granick . R . D . Levere . an dA . Kappas . Assay s fo r

porphyrins . 8-aminolevulinic-aci d dehydratase , an dporphyrinoge n synthetas e i n microlite r sample s o f whol e blood : Application s t o metaboli c defect s involvin g th e hem e pathway . Proc . Natl . Acad . Sci. , U.S.A . 69:2381-2385 , 1972 . 48 . Piomelli , S . A micro-metho dfo r fre e erythrocyt e porphyrins : Th e FE Ptest . J . Lab . Clin . Med . 87:932-940 , 1973 . 49 . Lamola , A . A. , M . Joselow , an dT . Yamane . Zin c pro toporphyri n (ZPP) : A simple , sensitive , fluorometri c screenin g tes t

fo r lea dpoisoning . Clin . Chem . 27(l):93-97 , 1975 . 50 . Chisolm , J . J. , Jr. , an dD . H . Brown . Micro-scal e photo

fluorometri c determinatio n o f "fre e erythrocyt e porphyrin " (protoporphyri n IX) . Clin . Chem . 27(11):1669-I682 , 1975 . 51 . Blumberg , W . E. , J . Eisinger . A . A . Lamola , an dD . M . Zuckerman . Th e hematofluorometer . Clin . Chem . 2J(2):270-274 , 1974 . 52 . Matson , W . R. , R . M . Griffin , T . J . Sapienza , J . M . Shiavone , an dA . J . Reed . A Critica l Evaluatio n o f th e Technica l an dOperationa l Utilit y o f Zin c Protoporphyri n (ZnP) , Erythrocyt e Protoporphyri n (EP ) an dBloo dLea d (BL ) i n Pediatri c Screening s fo r Lea dInsult . Pape r

pre sente da t

Regio n I V DHE WCD C Conferenc e o n Pediatri c Lea dPoisonin g Contro l Projects , Atlanta , Ga . Februar y 1976 . 53 . Hanna . T . L. . D . W . Dietzler . C . H . Smith . S . Gupta , an d H . S . Zarkowsky . Erythrocyt e porphyri n analysi s i n th e detectio n oflea dpoisonin g i n children : Evaluatio n o f fou r micr o methods . Clin . Chem . 22: 161-168 . 1976 . 54 . Chisholm , J . J. , C . W . Hastings , an dD . K . K . Chering . Micro-phot o fluorometri c assa y fo r protoporphyri n in acidifie daceton e extract s o f whol e blood . Biochem . Med . 9:113 , 1974 .



### 9- 8

# 10 . METABOLISM O F LEA D 10. 1 INTRODUCTIO N Th e metabolis mo f

lea din ma n may b e define da s th e physiologica l processe s relatin g t o absorption , distribution , translocation , an dne t retention . Th e metabolis mo f

lea din ma n i s discusse din thi s chapte r i n term s o f

route s o f

exposur e an do f

th e physiologica l distinctions , existin g withi n popula

tio n classes , tha t

modif y metaboli c processes , especiall y withreferenc e t o childre n versu s adults . Mos t o f th e materia l discusse din th e followin g page s addresse s th e dietar y habit s o f adult s in th e Unite dStates . Fo r

children , however , ther e ar e die

tar y habit s tha t

ar e distinc t

fro mthos e o f

adult s an d tha t hav e implication s fo r difference s in exposur e betwee n adult s an dchildren . Fo r example , i n assessin g th e indirec t contributio n o f airborn e lea dt o diet , on e mus t conside r th e hand

to-mout hactivit y o f

youn g children , i.e. , suckin g o f dirt y finger s in contac t

withenvironmenta l dus t an d dirt ; retrievin g foodstuffs , suc ha s lollipops , tha t fal l int o dirt ; an dahos t

o f othe r childhoo dactivitie s b y whic hairborn e lea dma y contribut e t o th e intak e o f lea db y childre n bu t

no t b y adults . I n thi s chapter , th e physiologica l processe s tha t contro l th e uptak e o f

lea db y ma n (absorption ) wil l b e discusse dfirst . The n th e movemen t o f lea d throug hth e bod y int o it s depo t tissue s (distribution ) an dit s eventua l eliminatio n (excretion ) wil l b e treated . 10. 2 ABSORPTIO N Th e quantitie s o f

lea dabsorbe dfro menvironmen

ta l source s ar e determine dno t onl y b y th e amoun t ingeste do r

inhale dbu t

als o b y th e particl e siz e an d chemica l specie s involved . Absorptio n depend s als o o n specifi c hos t factor s such , a s age , nutrition , an dphysiologica l status . I n addition , th e tota l quantit y ingeste din foo dan d wate r varie s greatl y fro mindividua l t o individual , an dth e tota l quantit y inhale ddepend s o n th e siz e an dweigh t

o f th e individua l an do n th e energ y ex pende di n day-to-da y activity . 10.2. 1 Respirator y Absorptio n Th e Internationa l Radiologica l Protectio n Com

missio n (IRPC ) Tas k

Grou p o n Lun g Dynamics ' develope damode l designe dt o predic t th e percen tag e o f inhale daerosol s tha t

woul db e deposite dan d retaine din th e lungs . Thi s mode l predicte dtha t ap proximatel y 3 5 percen t o f th e lea dinhale din genera l ambien t

ai r woul db e deposite din th e air

ways . Sinc e th e aerodynami c diamete r o f lea dparti

cle s i s generall y in th e rang e o f 0. 1 t o 1. 0 fim, depositio n woul doccu r predominantl y i n th e deepe r region s o f

th e lung . Emission s fro mstationar y source s frequentl y includ e asignifican t proportio n o f large r particle s that , whe n inhaled , woul db e deposite dprimaril y in th e nasopharynx . Becaus e thes e particle s usuall y fal l ou t o f th e ai r rathe r quickly , exposur e t o thes e large r particle s i s limite d primaril y t o th e nea r

vicinit y ofth e emissio n source . Th e depositio n withi n th e respirator y trac t o f ver y smal l particle s (<0. 1 fim) apparentl y occur s chiefl y b y diffusion, 2 an drate s o r site s canno t

b e predicted . Th e IRP C mode l predict s atota l airwa y depositio n o f 4 0 t o 5 0 percen t

fo r 0. 5 /xmparticles , bu t

astud y in huma n volunteer s indicate donl y 6 t o 1 6 percen t desposition , dependin g o n th e rat e an ddept ho f respiration. 3 Chemica l compositio n als o affect s up tak e a s doe s th e agin g o f th e aeroso l (Chapte r

6) . Thi s illustrate s th e difficult y i n choosin g th e ap propriat e chemica l composition 4 fo r studie s o n deposition . Airwa y clearanc e o f

lea daerosol s a s predicte db y th e IRP C lun g model ' i s eve n mor e tenuou s tha n ar e prediction s regardin g deposition . Th e mode l indi

cate s tha t

th e absorptio n o r

clearanc e o f

lea d deposite di n th e airway s woul dvar y greatl y depend

in g o n th e solubilit y an do n th e inheren t toxicit y o f th e particle s t o th e clearanc e mechanis m(lun g macrophage s an dcilia) . 10.2.1. 1 HUMA N STUDIE S Actua l studie s o n th e fractiona l depositio n o f par ticle s in th e respirator y trac t o f ma n hav e no t

bee n extensive , especiall y i n th e cas e o f lead . Usin g a n ai r 10- 1P.3 5

lea dleve l o f

15 0 /xg/m 3 , Kehoe 5 7 studie dth e depositio n o f

combuste dtetraethy l lea di n huma n volunteers . Th e sourc e o f lea dwa s combuste d tetraethy l lead , whic hproduce dlea d(III ) oxid e (Pb 2 0 3 ) in th e air . Subject s breathe dai r containin g 150 /j.g/m 3 lead ; th e smalle r particle s average d0.0 5 /u mi n diamete r

an dth e large r

one s average d0. 9 fim i n diameter , a s viewe dunde r th e electro n microscope . Thi s represent s amas s media n equivalen t

diamete r

o f approximatel y 0.2 6 an d2. 9 fim, respectively. 8 Thirty-si x percen t ofth e smalle r particle s an d4 6 percen t o f th e large r

particle s wer e deposited . Nozaki 9 reporte dtha t

whe n lea dfume s generate d in ahigh-frequenc y inductio n furnac e wer e inhale d at aconcentratio n o f

10,00 0 figlm 3 depositio n wa s relate dt o respiratio n rat e an dparticl e size . A t 1 0 respiration s pe r

minute , th e depositio n decrease d fro m6 3 t o 4 2 percen t a s th e particl e siz e wa s reduce dfro m1. 0 t o 0.0 5 fim. A t 3 0 respiration s pe r minute , depositio n rate s wer e abou t halved . Th e results , whic har e simila r t o thos e o f

Kehoe, 5 7 ar e fairl y consisten t

wit hth e IRP C lun g depositio n model. 1 Thes e dat asugges t

tha t a3 0 ± 10-percen t

deposi

tio n rat e ca n b e expecte di n individual s breathin g ambien t ai r an dtha t depositio n ma y var y considera

bly , dependin g o n th e particl e siz e an dth e frequenc y o f respiration . Th e rat e o f

lun g clearanc e ha s bee n studie db y mean s o f gamma-ra y lun g scan s followin g inhalatio n o f 212 Pb , bu t

th e relevanc e o f

th e result s t o th e rat e o f clearanc e ofth e chemica l an dphysica l form s o f lea d usuall y inhale db y ma n i s highl y questionable. 1 0 Thes e studie s involve dth e absorptio n o f 212 P b atom s o n carrie r

aeroso l particles ; however , desorptio n unde r thes e artificia l circumstance s ma y b e totall y unlik e th e clearanc e rat e fo r ambien t ai r lea dparti

cles . Kehoe 5 7 reporte dasubstantia l increas e in fecal excretio n whe n large-particl e lea doxid e aerosol s wer e inhale dfo r

man y week s a t

10 5 /xg/m 3 ; th e in

creas e probabl y resulte dfro mth e swallowin g o f par ticle s trappe di n th e nasopharynx . Whe n ai r wit ha simila r lea dconcentratio n i n smal l particle s wa s in

haled , onl y asmal l ris e i n feca l lea dexcretio n wa s observed . I n arecen t

study , Chamberlai n e t

al. " foun da35

- percen t rat e o f deposition , a t

arespiratio n rat e o f

1 5 pe r minute , whe n subject s inhale dautomobil e ex haus t fume s containin g radioactivel y labele d tetraethy l lea d( 203 Pb) . Thi s compare s favorabl y wit hNozaki' s previou s findings. 9 Thes e authors " calculate dtha t unde r condition s o f

chroni c airborn e lea dexposur e roughl y 5 0 percen t o f th e deposite d lea di s absorbed . Althoug halveola r macrophage s inges t particle s deposite din th e lungs , thes e cell s ma y b e damage db y inorgani c lea dcompounds. 1 2 Suc hdamag e ha s bee n demonstrate di n rat s an d guine apigs . I t

i s possible , then , tha t lun g defens e mechanism s ma y b e impaire dwhe n ai r contain s hig h lea dconcentrations . 10.2.1. 2 ANIMA LSTUDIE S Anima l studie s b y Bingha me t al. 1 3 hav e demon

strate dapronounce dreductio n in th e numbe r o f lun g macrophage s resultin g fro minhalatio n o f lea d oxid e at bot h1 0 an d15 0 figlm*. Simila r result s hav e bee n reporte db y others . 12

- 14 > 1 5 Thi s suggest s tha t th e lun g clearanc e mechanis mma y functio n les s effectivel y whe n ai r

lea dconcentration s ar e high . Thus , Pot t

an dBrockhaus 1 6 reporte dtha t larg e dose s o f lea dbromid e solutio n o r lea doxid e suspen sio n administere dintratracheall y t o rat s (1. 5 m g o f lea doxid e pe r

dos e o n 8 successiv e days ) wer e re taine db y th e bod y a s completel y a s wer e intra

venou s doses . A t

one-thir dth e dose , however , reten tio n vi ath e intratrachea l rout e wa s significantl y less . Randal l an dhi s coworkers 1 7 expose d4 baboon s t o aerosolize dlea d(Pb 3 0 4 ) o f varyin g particl e siz e (mas s media n diameter s o f 5.9 , 3.2 , an d2. 0 fim, respectively) . Th e ai r

lea dconcentration s varie d fro mapproximatel y 1 t o 4 /xg/m 3

. Th e exposur e perio dlaste d4 weeks , an dbloo dsamplin g con tinue dfo r

6 weeks . Th e rat e o f

absorptio n o f

lea d int o bloo dwa s faste r

an dreache dahighe r

leve l fo r coars e (mea n diamete r

= 1. 6 fim) particle s tha n fo r fin e (mea n diamete r

= 0. 8 fim). 10.2. 2 Gastrointestina l Absorptio n 10.2.2. 1 HUMA N STUDIE S I t mus t b e note da t

th e outse t

tha t th e absorptio n o f lea dfro mfoo dvarie s wit hth e physica l for mo f dietar y intake . Fo r

example , th e literatur e indicate s tha t th e percen t

absorptio n o f

lea dfro mbeverage s i s abou t fiv e t o eigh t

time s greate r

tha n tha t

fro msoli d food. 182 0 Kehoe 5 7 conclude dfro mlong-ter mbal

anc e studie s tha t

approximatel y 1 0 percen t ofth e in

tak e o f lea dfro mfoo dan dbeverage s wa s absorbe d fro mth e gastrointestina l trac t sinc e thi s wa s th e amoun t excrete din th e urine . Thi s estimate , how

ever , disregarde dth e urinar y lea dtha t migh t hav e com e fro minhalation , a s wel l a s th e lea dexcrete din fece s afte r

absorptio n fro mth e gastrointestina l tract . Rabinowit z e t

al., 2 1 however , obtaine dsimila r 10- 2result s usin g orall y administere d204 P b incorporate d

int o th e diet . Alexande r

e t al. 2 2 studie dth e absorptio n o f lea d fro mth e gastrointestina l trac t in 8 infant s an dyoun g childre n age d3 month s t o 8. 5 year s an dconclude d tha t 5 3 percen t

o f ingeste dlea dwa s absorbed . Ab

sorptio n an dretentio n wer e consisten t withi n th e ag e rang e studied . Thi s study , however , ha s bee n criti

cize dbecaus e th e value s varie dgreatly . I n arecen t

study , Ziegle r

e t al. 2 3 showe dtha t

a greate r percentag e o f

intak e lea dwa s absorbe dan d retaine db y infant s tha n b y olde r subjects . I n thi s re port , 2 separat e serie s o f investigation s wer e con ducted . I n th e first , 3 t o 8 balanc e studie s wer e per forme dwit h9 infant s each . I n th e second , eac ho f 6 infant s consume drandoml y allocate ddiet s provid

in g low , intermediate , an dmoderat e amount s o f lead . Whe n intake s o f

lea dexceede d5 /ug/kg/day , whic hi s areasonabl e leve l give n typica l dietar y pat terns , ne t absorptio n average d4 2 percen t an dreten tio n average d3 2 percen t o f intake . I t

shoul dals o b e note dtha t

ther e wa s a n invers e relationshi p betwee n calciu mintak e an dbloo dlea dlevel . Thes e result s ar e in genera l agreemen t with anima l studie s an dt o som e exten t corroborat e th e finding s o f

Alexande r

e t al. 22 Th e stud y o f

Ziegle r e t al. 2 3 appear s t o b e muc hbette r designe dtha n tha t

o f Alexande r

e t al. 2 2 Ingeste do r

dietar y lea di s ofte n though t o f a s reachin g asubjec t vi aadistinctl y differen t rout e o f exposur e tha n inhale dlead . Inhalatio n o f lea dma y b e regarde da s direc t

exposur e t o airborn e lead . Som e portio n o f

dietar y lea dma y als o b e attribute d t o exposur e t o airborn e lead , bu t indirec t rathe r tha n direct , wit hlea dreachin g foo deithe r b y depositio n ont o aeria l edible s o r

b y fallou t

ont o soi l an dsubse

quen t absorptio n b y roo t

crops . (Interna l trans locatio n o f

lea dbetwee n root s an daeria l part s i s ap parentl y small. ) I n addition , variabl e fraction s o f in

hale dlea dar e ingeste dafte r depositio n i n th e air

ways ; the y ar e cleare db y retrograd e movemen t t o th e pharynx , wher e th e particle s ar e the n swallowed . Sectio n 7.4. 1 cite s lea dconcentration s typicall y foun di n variou s foods , bu t n o researc hha s bee n brough t t o ligh t tha t clearl y partition s th e origin s o f foo dlead . Ther e woul dsee mt o b e thre e principa l candidates : (1 ) depositio n o f airborn e lea d(o n pri

mar y foo dcrop s an do n anima l fee dcrops) ; (2 ) ab

sorptio n o f

soi l lea d(muc ho f

thi s lea di s ofte n th e historica l accumulatio n o f airborn e fallout) ; an d(3 ) lea dacquire din th e processin g an dcannin g o f foods . Base do n th e contrast s betwee n fres han dpro cesse dfood s (excludin g froze n foods) , it woul dap pea r tha t processin g an dcannin g o f certai n food s regularl y double s o r

triple s thei r

averag e lea dcon centration s (Tabl e 10-1) . TABL E 10-1 . LEA D CONTEN TO F FRESH , PROCESSED , AN D CANNE D FOODSTUFFS 2 4

Foo d Lea d concentratio n (ppm ) Foo d Lea d concentratio n (ppm ) Fres h produc e Carrot s Lettuc e Potatoe s Avg . Processe d food s Whit e flou r Cornmea l Ric e Cerea l Suga r Avg . Processe d meat s Ho t dog s Hamburge r Avg . Fres h meat s Bee f Chicke n Live r Avg . 0.20 5 0.13 0 0.05 0 Canne d vegetable s Beet s Bean s Pea s 0.12 8 0.05 2 0.14 3 0.10 4 0.10 7 0.03 1 0.08 7 0.44 6 0.57 8 0.51 2 0.12 0 0.19 1 0.15 0 Tomatoe s Avg . Canne d juice s Tomat o Vegetabl e Orang e Frui t Avg . Canne d fruit s Peache s Pineappl e Applesauc e Avg . 0.38 1 0.31 8 0.42 5 0.71 0 0.45 8 0.33 8 0.21 5 0.13 5 0.25 1 0.23 5 0.41 7 0.40 2 0.32 0 0.38 0

0.15 4 10- 3P.3 7

Th e dat ao n lea di n food s ar e no t comprehensiv e enoug ht o permi t

constructio n o f

aspectru mo f level s rangin g fro mfres ht o canne dan dcharac

terizatio n o f

th e resultin g lea dexposure . I t mus t suffic e t o stat e a t

thi s poin t

tha t som e fractio n o f

die

tar y lea dprobabl y i s indirectl y o f airborn e origin . 10.2.2. 2 TH ERELATIONSHI PO FORA LIN

TAK ET O BLOO D LEA D LEVEL S I t ha s bee n demonstrate drepeatedl y tha t bloo d lea dlevel s increas e whe n th e ora l intak e o f lea din

creases , bu t

aquantitativ e expressio n o f thi s relationshi p ha s no t

bee n determined . Studie s fro m variou s part s o f

th e world , a s note dbelow , hav e show n tha t

th e increas e in th e bloo dlea dfo r eac h 10 0 fig o f lea dingeste ddail y range s fro mles s tha n 6 t o mor e tha n 1 8 /ug/dl . I t i s importan t

t o poin t ou t tha t th e hig hen do f

thi s rang e wa s gathere dusin g subjec t group s whos e die

tar y intak e ma y b e o f

questionabl e relevanc e t o th e genera l population . Teppe r an dLevin 2 5 employe d adul t female s i n thei r

stud y whil e Coulsto n e t al. 2 6 use da n adul t

priso n population . Thes e finding s ar e no t onl y i n contras t

t o thos e fro mearlie r

U.S . studie s bu t als o t o th e result s o f anumbe r

o f Europea n studie s base do n th e genera l population. 2 7 Th e Euro

pea n dat aar e mor e consisten t withacontributio n o f abou t 6 figld\ t o th e bloo dlea dleve l pe r 10 0 fig dail y ora l intak e o f

lead ; asimila r

leve l i s reporte d b y Kehoe. 5 7 Children , particularl y infants , absor b alarge r percentag e o f

lea dtha n d o adults . Consequently , th e contributio n o f

dietar y lea dt o bloo dlea dlevel s probabl y i s les s fo r

adults , bu t

definitiv e dat aar e no t available . 10.2.2. 3 ANIMA LSTUDIE S Th e absorptio n o f

lea dfro mfoo dan dchange s in absorptio n withag e hav e bee n investigate di n man y anima l studies ; th e usua l value s foun drange dbe

twee n 5 an d1 0 percent . However , Kostia l e t al. 2 8 demonstrate dtha t

5

- t o 7-day-ol drat s absor b at leas t 5 5 percen t

o f singl e ora l trace r

dose s o f

203 Pb , an dForbe s an dReina 2 9 reporte dtha t i n rat s th e gastrointestina l absorptio n o f trace r dose s o f

2l2 Pb , 85 Sr , an d59 F e wa s hig hprio r t o weanin g bu t decrease drapidl y thereafter . Th e absorptio n rat e fo r lea dwa s 8 3 percen t

a t 1 6 days ; it

the n decrease d graduall y t o 7 4 percen t o n th e da y o f

weanin g (2 2 days ) an drapidl y thereafte r t o abou t

1 6 percen t

at 8 9 days . Althoug hther e ma y b e som e questio n abou t th e applicabilit y o f

thes e data , the y ar e consisten t withresult s reporte dfro mstudie s o f youn g children . Kell o an dKostial 3 0 hav e show n tha t mil k in

crease s lea dabsorptio n in 6-week-ol drats . Fastin g enhance s lea dabsorptio n in mice. 2 0 Lo w dietar y level s o f calcium , iron , zinc , copper , selenium , an d vitami n D hav e bee n reporte dt o enhanc e lea d absorption. 31

- 3 2 I t

ha s als o bee n demonstrate dtha t rat s o n a n iron-deficien t die t accumulat e mor e lea d in thei r bodie s tha n d o rat s o n a n iron-sufficien t diet. 3 3 Tabl e 10- 2 present s th e dat ao f Barltrop 3 4 relatin g t o th e effect s o f variou s nutritiona l factor s o n lea dabsorptio n a s reflecte din bloo dlea dlevels . I t shoul db e note dtha t

thes e studie s ar e shor t ter m studie s obtaine dove r

aperio do f

4 8 hr . TABL E 10-2 . EFFEC TO F DIFFEREN TDIET S O N LEA D ABSORPTIO N EXPRESSE D A S TH E RATI O O F MEA N RETENTIO N FO R EXPERIMENTA L AN D CONTRO L

SUBJECTS 3 4

Die t Lo wprotei n Hig h protei n Lo wfa t Hig h fa t Lo wmineral s Hig h mineral s Lo wfibe r Hig h fibe r Lo wvitamin s Hig h vitamin s Bloo d

. 5. 1 1 1 9. 6 17. 7 0. 2 1 1 1 1 Rati o o l mea n retentio n o f lea d

(experimenta l Kidney s 2. 5 3. 7 1 7. 6 11. 9 0. 2 1 1 1 1 control )

Femu r 2. 8 2. 6 1 4. 8 13. 7 0. 1 1 1 1 1 Live r

2. 2 1 1 4. 2 8. 8 0. 1 1 1 1 1 Th e absorptio n o f

lea din pain t

chip s ha s receive d attentio n becaus e ofth e ris k fo r youn g childre n wh o ten dt o inges t

thi s material . Recen t

dat afro mra t studie s indicat e tha t

lea dchromat e an dlea d naphthenat e incorporate dint o drie dpain t film s ar e substantiall y availabl e fo r absorption , althoug hth e absorptio n rat e i s 3 0 t o 5 0 percen t wha t it i s fo r lea d naphthenat e in oi l o r

for lea dnitrat e i n aqueou s solution. 35

- 3 6 Th e absorptio n o f lea da s afunctio n o f chemica l for mi s show n in Tabl e 10-3. 3 7 TABL E 10-3 . PERCENTAG E ABSORPTIO N O F DIFFEREN T LEA D COMPOUND S RELATIV E T O LEA D ACETATE 3 7 Lea d compoun d Absorption . % Contro l (n o lead ) Metalli clea d (18 0 t o 250/xm ) Lea d chromat e Lea d octoat e Lea d naphthenat e Lea d sulfid e Lea d thallat e Lea d carbonat e (basic ) 4 1 4 4 4 6 2 6 4 6 7 12 1 16 4 10- 410.2. 3 Cutaneou s Absorptio n

Absorptio n throug hth e ski n i s o f importanc e onl y in th e cas e o f

organi c compound s o f lead , particu

larl y th e lea dalkyl s an dlea dnaphthenates. 38

- 3 9 Soo n afte r

tetraethy l lea dwa s introduce dint o com mercia l use , Eldridge 3 9 reporte dtha t i t wa s ab

sorbe dthroug hth e ski n wit hgrea t facilit y i n bot h dog s an dguine apigs . Th e presenc e o f gasolin e ha s bee n sai dt o dela y th e penetratio n o f tetraethy l lea d throug hth e skin, 4 0 althoug hit ha s n o effec t

o n it s uptak e b y th e lungs. 4 1 I n rats , fiv e cutaneou s o r sub

cutaneou s application s o n alternat e day s o f lea dace tat e o r lea dnaphthenat e produced , compare dwith unexpose danimals , adecreas e in ALA D in liver , a decreas e in live r

an dbod y weight , an ddistributio n o f lea din assaye dbod y tissues . Lea dconten t wa s highes t in kidney . Lea dnaphthenat e wa s considere d b y th e investigator s t o b e mor e toxi c tha n lea dace tat e becaus e o f

mor e pronounce dski n reactions , highe r lea daccumulatio n in brain , an dth e occur renc e o f aparalyti c syndrom e befor e deat hin tw o animals. 4 2 Th e rat e o f

absorptio n o f

tetraethy l lea dan din

organi c compound s throug hth e ski n wa s studie db y Lan g an dKunze. 4 3 The y applie dsolution s o f lea d acetate , lea dorthoarsenate , lea doleate , an d tetraethy l lea dt o th e bar e ski n o f anumbe r

o f rat s an dmeasure dth e amoun t oflea din th e kidne y a s an inde x o f absorption . I n al l cases , th e amoun t o f lea d in th e kidne y wa s greate r tha n in controls ; tetraethy l lea dproduce dth e greates t difference . Ifth e ski n wa s traumatize dbefor e th e lea dsolution s wer e applied , ther e wa s athreefol do r fourfol dincreas e in rena l lea dconcentration . I t i s likel y tha t

absorptio n throug hunabrade dski n b y variou s lea dcompound s i s primaril y dependen t o n thei r

relativ e lipi d solubilities . Becaus e o f

th e difficulty , particularl y in tetra ethyl-lead-contaminate datmospheres , i n attemptin g t o separat e cutaneou s exposur e fro mrespirator y ex posure , th e rol e o f

cutaneou s lea dabsorptio n in rela

tio n t o bloo dlea dlevel s i s stil l unclear . 10. 3 DISTRIBUTIO N Whe n asingl e dos e o f

lea denter s th e body , it i s distribute dinitiall y i n accordanc e withth e rat e o f deliver y o f

bloo dt o th e variou s organ s an dsystems . Th e materia l i s the n redistribute dt o organ s an d system s in proportio n t o thei r respectiv e affinitie s fo r lead . Whe n dail y ingestio n i s consisten t fo r a n extende dperiod , anearl y stead y stat e i s achieve d withrespec t

t o intercompartmenta l distribution . Th e steady-stat e conditio n will b e disturbed , how

ever , wheneve r short-ter mhig hlevel s oflea dintak e ar e superimpose do n suc halong-ter mingestio n pat tern . 10.3. 1 Huma n Studie s Autops y dat ahav e show n tha t lea dbecome s localize dan daccumulate s in bone . Thi s accumula

tio n begin s in feta l life, 44

- 4 5 sinc e lea di s readil y transferre dacros s th e placenta . Th e concentratio n o f lea din th e bloo do f

newbor n childre n i s simila r t o tha t o f thei r mothers, 46

- 4 7 an dth e distributio n o f lea din feta l tissu e i s simila r t o tha t o f adults. 4 5 Th e tota l conten t

o f lea din th e bod y ma y excee d 20 0 mg in me n age d6 0 t o 7 0 years , bu t in wome n it i s somewha t

lower . Calculation s b y severa l in

vestigators 4 8 sho w tha t i n nonoccupational ^ ex pose dadult s 9 4 t o 9 5 percen t o f th e tota l bod y burde n i s in th e bones. 44

- 49

- 5 0 Thes e report s no t onl y reaffirmth e affinity o f

bon e fo r

lead , bu t

als o pro vid e evidenc e tha t

th e concentration s o f lea din bone s increas e a t

leas t unti l middl e ag e (5 0 t o 6 0 year s old). 48

- 5 1 O n th e contrary , neithe r sof t tissue s no r bloo dsho w age-relate dchange s in lea dcon centratio n afte r

ag e 20. 52

- 5 3 Thus , it

seem s tha t

th e skeleto n i s arepositor y tha t reflect s th e long-ter m accumulativ e exposur e t o lead , wherea s bod y fluid s an dsof t tissue s equilibrat e rathe r rapidl y an dreflec t onl y recen t

exposures . Th e concentratio n o f

lea din th e bloo di s utilize d a s a n inde x o f

exposur e t o asses s condition s con sidere dt o represen t

aris k t o health. 5 4 Plasm alea d concentration s hav e bee n show n t o b e constan t a t 2 t o 3 /ug/d l ove r

arang e o f

1 0 t o 15 0 /ug/d l whol e blood. 5 5 Recen t

studie s hav e indicate dtha t lea di s boun dprimaril y t o erythrocyt e protein , chiefl y hemoglobin , rathe r

tha n t o stroma. 5 6 Rabinowit z use dastabl e lea disotop e trace r ( 204 Pb ) t o determin e th e rat e o f equilibratio n o f bloo dlea dwit hinput. 2 1 H e foun dtha t in huma n subject s wit haconstan t dail y ora l intak e o f 204 Pb , a virtuall y constan t

concentratio n wa s measure di n bloo dafte r

abou t 11 0 days . Whe n lea dwa s remove d fro mth e diet , th e concentratio n in th e bloo ddisap

peare dwithahal f

tim e o f approximatel y 1 9 days . Tol ae t al. 5 7 reporte dtha t

th e concentratio n o f

lea d in th e bloo drise s fairl y rapidl y t o ane w steady-stat e leve l in abou t

6 0 day s whe n me n ar e introduce dint o an occupationa l lead-exposur e situation , asituatio n simila r t o tha t cite dfo r

exposur e chamber s in clini

ca l studies. 5 8 Althoug hth e bod y burde n o f lea dincrease s throughou t

life, 48

- 50

- 5 2 measurement s o f specifi c organ s an dsystem s sho w tha t th e tota l burde n i s 10- 5P.3 9

divide dbetwee n tw o genera l pool s withi n th e body . Th e majo r

portio n o f

th e lea di s containe din bone . Thi s poo l i s clearl y highl y accumulativ e and , a s a consequence , lea daccumulate s her e rathe r con sistentl y an dcontinuously . Th e secon dpoo l com prise s othe r

organ s an dsystem s an daccumulate s muc hless . Th e level s of lea din thi s poo l ten dt o stabiliz e earl y in adul t lif e an dthereafte r

demon

strat e aturnove r

rat e sufficien t

t o preven t

accumula

tion . Sinc e th e organ s an dsystem s tha t contai n th e relativel y mobil e lea dpoo l ar e o f greate r toxicologi

ca l significance , it

i s clea r tha t amobilizabl e o r exchangeabl e lea dburde n i s amor e importan t con cep t tha n i s tota l bod y burden . I n thi s connection , chelatabl e urinar y lea dha s bee n show n t o provid e a n inde x o f

th e mobil e portio n o f th e tota l lea d burden. 59

- 6 0 Amon g adult s in th e genera l populatio n ther e ar e n o age-relate ddifference s i n con centration s o f

lea din whol e bloo do r in bloo d serum . Thus , i n agenera l way , th e bloo dlea dleve l i s an indicato r

o f th e concentratio n o f

lea din sof

t tissues , an dth e change s in bloo dlea dlevel s ob

serve dwhe n ther e ar e change s i n exposur e level s probabl y reflec t

simila r change s i

n som e organ s an d sof t tissues . Lea dexposur e cause s th e developmen t o f nuclea r inclusio n bodie s containin g lea din bot hman 61 " 6 3 an danimals . Althoug hthe y see mt o occu r mos t fre

quentl y in th e kidney , the y hav e bee n foun din othe r organ s a s well . Th e concentration s o f

lea din deciduou s teet har e o f interes t becaus e toot hanalysi s represent s anonin

vasiv e techniqu e an dbecaus e teet hprovid e arecor d o f long-ter mlea dexposure . Th e dentin e i s par ticularl y usefu l i n thi s respec t becaus e i t

i s lai ddow n fro mth e tim e o f

eruptio n t o th e tim e th e toot hi s shed . Concentration s o f lea din dentin e ar e reporte d t o b e considerabl y lowe r i n suburba n schoo l childre n tha n in childre n residin g i n area s o f hig h lea dexposure. 6 4 Primaril y becaus e o f

th e relativ e eas e withwhic h hai r ca n b e collected , ther e hav e bee n som e studie s o f th e possibl e us e o f

hai r lea da s an inde x o f

ex posure . Thes e studie s hav e no t bee n sufficient , however , t o provid e significan t informatio n o n th e relationshi p betwee n hai r lea dconcentration s an d th e amoun t

o f exposure . Rabinowit z e t al. 6 5 fe d labele dlea d( 204 Pb ) t o 3 subject s dail y fo r approxi

matel y 100 days . Level s o f isotop e in th e bloo dwer e immediatel y elevate dbu t i n facia l hai r

ther e wa s a muc hmor e gradua l response , withadela y o f

approximatel y 3 5 days . 10.3. 2 Anima l Studie s Administratio n o f

asingl e dos e o f

lea dt o rat s pro duce s hig hinitia l concentration s o f lea din sof

t tissue s whic hthe n fal l rapidl y a s th e resul t o f excre tio n an dtransfe r

t o bone. 6 6 Th e distributio n charac

teristic s o f

lea dwithi n th e animals ' bodie s wer e foun dt o b e independen t o f th e dos e ove r

awid e range . Castellin o an dAloj 6 7 describe dth e rat e con stant s fo r

th e eliminatio n o f

lea dfro mvariou s tissue s in rat s followin g asingl e dose . Lea dwa s eliminate dfro mbon e muc hmor e slowl y tha n fro m othe r tissues . Bolanowsk ae t al. 6 8 reporte dtha t

th e rat e o f eliminatio n o f

asingl e dos e o f

lea dfro mrat s becam e slowe r

withtime , reflectin g progressivel y decreasin g mobilit y ofth e residua l bod y burden . Goldstei n e t

al. 6 9 sacrifice d21-day-ol drat s 2 4 h r afte r intravenou s injectio n o f variou s singl e dose s (1 . 50 , 20 0 fig) o f labele dlea d( 210 Pb ) an d foun dtha t

th e concentratio n o f

radioactivit y in th e brai n wa s directl y proportiona l t o th e bloo dradio

activity . Studie s o f

OTuam ae t

al. 7 0 indicate , however , tha t

thi s proces s ma y no t

b e on e o f

simpl e passiv e diffusio n o f

lea dint o neura l tissue . Thes e latte r investigator s sacrifice dguine apig s a t 5 , 60 , an d24 0 min . afte r

th e intravenou s injectio n o f trace r dose s o f lea d( 2l0 Pb ) in bot hsubacutel y intoxicate d (15 5 mg PbCOj/da y for

5 days ) an dcontro l animals . Radioactivit y in barrie r tissue s (suc ha s choroi d plexu s an dmeninges ) ros e rapidly , withconcentra tion s rangin g t o mor e tha n te n time s th e simultaneou s brai n radioactivity . Subsequently , ther e wa s afal l in th e barrie r tissu e levels , bu t

brai n level s remaine dfairl y constan t an dlo w throughou t th e perio do f

th e study . Th e apparen t discrepancie s may b e explaine din larg e par t b y th e difference s in th e age s o f

th e animal s a s wel l a s othe r factors , in

cludin g specie s differences , tim e o f sacrifice , o r

a mor e comple x mechanis mo f distribution . Rathe r strikin g age-relate ddifference s in th e dis

tributio n an dretentio n o f lea di n rat s hav e bee n ob

served. 7 1 Eliminatio n o f asingl e trace r

dos e o f

203 P b fro mth e whol e body , blood , an dkidne y occurre d mor e rapidl y in adul t

tha n in sucklin g rats . I n suck

ling s ther e wa s asligh t increas e withtim e i n th e 203 P b conten t

o f th e brai n followin g administratio n o f th e dose , wherea s th e conten t in othe r sof t tissue s decrease dwithtime . Th e intracellula r

distributio n o f

lea dha s bee n studie di n ra t

tissue , mainl y b y cell-fractiona

10- 6tio n techniques. 7 2

- 7 3 Membranes , especiall y

mitochondria , hav e show n an affinity fo r lead . Littl e lea di s foun din lysosomes, 7 3 however , in contras t withth e intracellula r

distributio n o f

man y othe r metals , e.g. , mercury , copper , an diron . Ther e ar e few studie s o f targe t organ s in whic h lea dconcentration s at

th e sit e ofth e effec t

hav e bee n specificall y determined . I n particular , direc t assess men t o f lea dleve l in bon e marro w i s difficul t t o car ry out , althoug hth e sensitivit y o f th e hematopoieti c syste mt o lea dha s bee n extensivel y investigated . Formatio n o f

nuclea r inclusio n bodie s i s observe din rat s withrena l lea dconcentration s o f abou t 1 0 mg/k g (we t

weight ) o f

kidney. 7 4 Othe r

effect s o f

lea d wer e foun dt o occu r

onl y a t highe r level s o f

orga n concentration . Deat hin cattl e i s associate dwithlea d level s o f abou t 5 0 mg/k g (we t

weight ) o f

kidne y cor tex. 7 5 Th e concep t

o f estimatin g th e lowes t leve l o f meta l accumulatio n tha t result s in advers e effect s in atarge t orga n ha s no t

bee n wel l explore din th e cas e o f lead . Thi s i s in contras t withcadmium , fo r

whic h estimate s hav e bee n mad e o f th e minimu mcon centration s i

n th e kidne y corte x at

whic hevidenc e o f rena l damag e appears. 7 6 10. 4 ELIMINATIO N Th e majo r

portio n o f

excrete dlea dappear s i n urin e an dfeces , bu t

lesse r quantitie s ar e remove dvi a sweat , hair , nails , an dexfoliate dskin . 10.4. 1 Huma n Studie s Feca l excretio n represent s th e majo r rout e o f organi c an dinorgani c lea delimination . Th e rat e o f feca l lea dexcretio n ha s bee n reporte dt o b e 10 0 time s th e rat e o f

eliminatio n in urine; 77

- 7 8 however , mos t o f th e lea di

n fece s represent s meta l tha t ha s no t bee n absorbed . Rabinowit z e t

al. 7 9 studie dth e excretio n o f trace r lea dfro mth e bloo dof anonoccupational ^ expose d huma n subject . Urinar y an dfecal excretio n o f 204 P b fro mth e bloo damounte dt o 3 8 an d8 fig/day, ac countin g fo r

7 6 an d1 6 percent , respectively , ofth e measure drecovery . Th e crud e estimatio n o f lea di n hair , nails , an dswea t

yielde davalu e o f

4 fig ( 8 per cent) . Th e urinar y excretio n wa s simila r t o th e averag e dail y lea dexcretio n o f 3 1 /ug/da y reporte d b y Teisinge r

an dSrbova. 8 0 Booke r e t al. 8 1 ad

ministere dlead( 212 Pb ) intravenousl y t o 2 huma n subject s an dthe n recovere d4. 4 percen t o f th e dos e i n urin e durin g th e firs t 2 4 hr . Lea dwa s no t detecte din feces . Durin g th e secon d2 4 hr , abou t 1. 5 percen t

wa s measure din bot hurin e an dfeces . Thus , gastrointestina l transi t appear s t o pla y a n im

portan t rol e in th e rat e o f

excretio n in fece s o f systemicall y administere dlead . Th e clearanc e o f

lea dfro mth e bloo do f ma n int o urin e wa s foun db y Vostal 8 2 t o b e proportiona l t o th e rat e o f

creatinin e excretion , wit hurinar y lea d extrapolatin g t o zer o a t zer o creatinine . Th e characteristic s o f

urinar y lea dexcretio n ma y b e affecte db y th e chemica l formo f lead . Wherea s al l o f th e lea din urin e o f

subject s withnorma l ex posur e ca n b e precipitate db y th e additio n o f agent s suc ha s oxalate , phosphate , o r carbonate , onl y one thir dt o two-third s o f

th e lea din th e urin e o f lea d worker s i s availabl e fo r precipitation. 8 3 Thes e result s sugges t

th e presenc e of astabl e lea dcomple x in th e urin e o f

expose dworkers . Lea di s excrete di n swea t a s wel l a s urine . Schiels 8 4 reporte dtha t

ingestio n o f

lea dacetat e in

crease dth e lea dconcentratio n o f swea t twofol dt o fourfold . Schroede r

an dNason 8 5 foun dth e con centratio n o f

lea di n th e swea t

o f lead-intoxicate d subject s t o b e simila r

t o tha t in urine . Sinc e studie s o f

net lea dretentio n sugges t

that , a t lo w leve l exposures , highe r intake s ar e followe db y highe r rate s o f excretions 5 " 7

- 17

- 5 9 an dtha t lea dexcre tio n appear s t o b e disproportionatel y lo w in case s o f high-leve l exposure , ther e i s no t ye t apredictabl e relationshi p betwee n increase s in lea dexposur e an d i n lea dexcretion . 10.4. 2 Anima l Studie s Th e relativ e importanc e o f lea dexcretio n fro m bloo dint o urin e an dfece s varie s withth e specie s tested . Withi n 1 2 hr , 7. 4 percen t o f an intravenou s dos e appeare di n th e fece s o f rat s compare dwitha recover y o f

2. 3 percen t

tro murine. 8 6 I n sheep , also , fecal eliminatio n i s mor e rapi dtha n urinar y excre tio n o f lead. 8 7 I n contrast , urinar y excretio n wa s re porte dt o b e tw o time s greate r tha n feca l excretio n in baboons. 8 9 Ther e ar e indication s tha t mos t ofth e translocate d lea d(fro mbloo dt o intestine ) i s derive dfro mbile . O f th e 7. 5 percen t

o f a n intravenou s dos e o f lea d acetat e excrete db y shee p i n th e fece s withi n 6 days , 8 1 percen t

originate din bile. 8 7 Simila r result s wer e obtaine dfro mrats. 86

- 8 9 Althoug hspecie s difference s in gastrointestina l transi t tim e an dth e presenc e of a gallbladde r

ca n explai n difference s i n th e rat e o f ap pearanc e of asingl e injecte ddos e o f lea din th e feces , thes e factor s d o no t

accoun t fo r difference s i n th e relativ e amount s o f

steady-stat e lea deliminatio n in urin e an dfeces . Measurement s o f

lea dclearanc e int o th e urin e o f 10- 7P.4 1

animals , lik e thos e in man , requir e an accurat e measuremen t

o f th e fre e lea dconcentratio n in blood . Sinc e mos t

o f th e lea di

n bloo di s boun dt o re dcell s an dt o plasm aproteins , thi s measuremen t i s virtuall y impossible . Whethe r th e rena l tubul e take s a n activ e par t in lea dexcretio n i s ope n t o question . Mor e recently , it ha s bee n foun dtha t

th e rena l tubul e cel l transport s lea dint o th e urine, 9 0 perhap s becaus e o f th e pre senc e o f lead-bindin g ligand s in th e tubula r cell . Thes e observation s demonstrat e tha t th e rena l ex cretio n o f

lea dinvolve s mor e tha n filtratio n o f th e meta l at th e glomerulus . I t

i s likel y tha t

th e response s o f

secretor y an dreabsorptiv e processe s t o increase dcirculatin g lea dlevel s contribut e t o th e relativ e constanc y o f

urinar y excretio n in humans 5 " 7 an di n laborator y animals 7 4 tha t wer e expose dt o hig hdose s o f

lead . 1 0 5 ALKY L LEA D METABOLIS M Th e toxi c effect s cause db y tetraethy l lea dan d tetramethy l lea dar e no t produce db y th e tetraalky l compound s themselves , bu t rathe r b y th e trialky l derivative s forme db y dealkylatio n in th e liver. 86

- 9 1 Tetraethy l lea di s converte dprimaril y t o triethy l lea dan dpartl y t o inorgani c lead. 9 2 Triethy l lea d concentrate s i

n organ s an ddisappear s ver y slowly . Eve n afte r

severa l days , ther e i s n o significan t reduc

tion . Tetramethy l lea di s muc hles s toxi c tha n tetraethy l lead , probabl y becaus e it i s dealkylate dt o th e trialky l toxi c formmuc hmor e slowl y tha n i s tetraethy l lead. 9 3 Sinc e bot hthes e compound s hav e toxi c an d biochemica l effect s unlik e thos e o f inorgani c lead , th e biochemica l indice s use din assessin g inorgani c lea dexposur e woul dno t b e expecte dt o hav e th e sam e significanc e in assessin g exposur e t o organi c lead . Indeed , i n case s o f severe , acut e tetraethy l lea d poisoning , urinar y coproporphyrin s an dAL A excre tio n ar e no t

usuall y elevated , an dfre e erythrocyt e porphyrin s ar e onl y moderatel y an dinconsistentl y elevated. 94

- 9 5 Thes e biochemica l test s ar e therefor e o f littl e us e i n short-ter mexposur e situations . I n long-ter mexposur e situations , however , it i s possi

bl e tha t som e o f the mmay b e useful . Indeed , Robin

son 9 6 ha s show n tha t

in industria l worker s expose d t o tetraethy l lead , urinar y excretio n o f AL A i s in

creased , bu t

no t t o th e sam e degre e a s i n worker s ex pose dt o inorgani c lea dwh o hav e simila r level s o f tota l urinar y lea dexcretio n (organi c plu s inorganic) . Bolanowsk ae t

al. 9 7 demonstrate dtha t in thre e fatal case s o f tetraethy l lea dpoisonin g th e rati o o f in

organi c lea dt o triethy l lea drange dfro m67: 1 t o

18: 1 in th e urine . Thi s rati o di dno t reflec t th e rati o o f inorgani c t o triethy l lea din tissues , includin g th e brai n wher e th e rati o wa s approximatel y 1:1 . 1 0 6 METABOLI C CONSIDERATION S I N TH E IDENTIFICATIO N O F SUSCEPTIBL E SUBGROUP S I N TH E POPULATIO N Th e discussio n o n th e metabolis mo f lea dha s u p t o no w onl y tangentiall y specifie ddifference s in metabolis mbetwee n childre n an dadult s (Sectio n 10.2.2) . Ther e are , however , physiologica l dynamic s o f chil dgrowt han ddevelopmen t tha t hav e signifi

can t implication s for

th e increase dris k

o f childre n expose dt o lead . Ther e are , a s well , difference s be

twee n childre n an dadult s i n th e intake , desposition , etc. , o f lead . Metabolic , physical , an dothe r difference s be

twee n childre n an dadult s tha t mus t b e considere d include : (1 ) childre n hav e considerabl y les s surfac e are atha n adults , e.g. , a2-year-ol dchil dha s one thir dth e surfac e are ao f an adult ; thi s paramete r i s no t know n t o b e directl y relate dt o th e risk s associ

ate dwithlea dexposure; 9 8 (2 ) ther e i s greate r lea d intak e b y infant s o n aper-unit-body-weigh t basis , whic hi s probabl y relate dt o greate r calori c an d wate r requirements ; (3 ) ther e i s greate r intak e in childre n a s wel l a s ne t

absorptio n (Sectio n 10.2.2) . resultin g fro mgreate r

ne t respirator y intak e alon g withgreate r

ne t absorptio n an dretentio n fro mth e gastrointestina l tract : (4 ) th e rapi dgrowt hrat e o f childre n ma y reduc e th e margi n o f safety agains t

a variet y o f

stresses , includin g iro n deficiency , etc. ; (5 ) dietar y habit s o f

childre n i

n som e respects 9910 1 ar e quit e differen t

fro mthos e o f

adults ; norma l hand-to

mout hactivit y suc ha s thum b suckin g occur s a s wel l a s th e habi t

o f retrievin g dirt-contaminate d foodstuffs : (6 ) in childre n th e likelihoo do f protein , calcium , an diro n deficienc y i s s o grea t relativ e t o intak e tha t

anegativ e balanc e i n thes e factor s ma y exist ; (7 ) i

n ver y youn g childre n metaboli c path

ways 99 ' 0 1 ar e know n t o b e incompletel y developed , e.g. , th e blood-brai n barrie r in newborns ; an d(8 ) partitionin g o f

lea di n th e bone s o f

childre n i s differen t fro mtha t

o f adults. I00 ' 0 1 Onl y 6 0 t o 6 5 percen t o f th e lea dbod y burde n i s i n th e bone s o f children . Mor e importan t i s th e possibl e labilit y o f th e bon e fractio n o f

lea din children , particularl y i n th e cas e o f

coexistin g calciu mdeficiency . Rose n an d Wexler' 02 fin da

n increasin g resorptio n oflea di n ra t bon e orga n cultur e whe n calciu mi n th e mediu mi s reduced . 10-8

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### 10- 9P.4 3

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radioactiv e lea dfollowin g inhalatio n an dinjection . Brit . J . Radiol . 42:457-466 , 1969 . Vostal , J . Stud y o f

th e rena l excretor y mechanism s o f heav y metals . 15thInternationa l Congres s o f Occupa

tiona l Health , Vienna , 19-2 4 September , V . 3 . 1966 . p . 61-64 . Dinischiotu , G . T. , B . Nestorescu , J . C . Radielescu , C . Jonescu , N . Preda , an dG . Hutza . Studie s o n th e chemica l form s o f urinar y lead . Brit . J . Ind . Med . / 7:141-145 . I960 . Schiels , D . O . Eliminatio n o f lea di n sweat . Aust . Ann . Med . 3:225 , 1954 . 85 . Schroeder , H . A . an dA . P . Nason . Trac e elemen t analysi s i n clinica l chemistry . Clin . Chem . 7 7:46 1 -473 , 1971 . 86 . Costellino , N. , P . Lamanna , an dB . Grieco . Biliar y excre tio n o f lea di n th e rat . Brit . J . Ind . Med . 23:237-239 , 1966 . 87 . Blaxter , K . L . an dA . T . Cowic . Excretio n o f lea di n th e bile . Nature . 757:588 , 1946 . 88 . Cohen , N. , M . Eisenbud , an dM . E . Wrenn . Th e Retentio n an dDistributio n o f

Lead-21 0 i

n th e Adul t

Baboon . An

nua l Rept . t o th e U.S . Atomi c Energ y Commissio n (Oct . I , 196 2 - Sept . 30 , 1967) . U.S . Dept . o f Interior . Cincinnati , Ohi o 1967 . 21 8 p . 89 . Cikrt , N . Biliar y excretio n o f 2 o*Hg , MCu , 52Mn , 2 iop b i n th e rat . Brit . J . Ind . Med . 29:74-80 , 1972 . 90 . Vostal , J . Mechanism s o f rena l lea dexcretion . Biochem . Pharmacol . Conf . Issue . 2:207 , 1963 . 91 ' . Cremer , J . E . an dS . Callaway . Furthe r studie s o n th e tox icit y o f som e tetra - an dtrialky l lea dcompounds . Brit . J . Ind . Med . /8:277-282 , 1961 . 92 . Bolonowska , W . Distributio n an dexcretio n o f triethy l lea din rats . Brit . J . Ind . Med . 25:203-208 , 1968 . 93 . Cremer , J . E . Toxicolog y an dbiochemistr y o f alky l lea d compounds . Occup . Healt hRev . 77:14-19 , 1965 . 94 . Gutniak , O. , H . Koziolowa , an dE . Kowaiski . Fre e pro toporphyri n conten t

o f erythrocyte s i n chroni c tetraethy l lea dpoisoning . Lancet . 7: 1 I 37- 1 I 38 , 1964 . 95 . Beattie , A . D. , M . R . Moore , an dA . Goldberg . Tetraethyl

lea dpoisoning . Lancet . 2:12-15 , 1972 . 96 . Robinson , T . R . Delta-amin o levulini c aci dan dlea din urin e o f lea dantiknoc k

workers . Arch . Environ . Hlth . 28:133-139 , 1974 . 97 . Bolanowska , W. , J . Piotrowski , an dH . Carczynski . Triethyllea di

n th e biologica l materia l in case s o f acut e tetraethyllea dpoisoning . Arch . Toxicol . 22:278-282 , 1967 . 98 . Ziegler , E . E. , B . B . Edwards , R . L . Jensen , K . P . Mahaffey-Six , an dJ , J . Fomon . Absorptio n an dretentio n oflea db y infants . Ped . Res . 12. In Press . 1978 . 99 . Nationa l Researc hCouncil . Recommendation s fo r th e preventio n o f

lea dpoisonin g i n children . Nationa l Academ y o f

Sciences . Washington , D.C . Jul y 1976 . 100 . Lin-Fu , J . S . Vulnerabilit y o f childre n t o lea dexposur e an dtoxicity . N . Engl . J . Med . I . 289(23) : 1229-1233 , 1973 . 101 . Lin-Fu . J . S . Vulnerabilit y o f childre n t o lea dexposur e an dtoxicity . N . Engl . J . Med . II . 289(24):1289-1293 , 1973 . 102 . Rosen , J . F . an dE . E . Wexler . Studie s o f lea dtranspor t

in bon e orga n culture . Biochem . Pharmacol . 26:650-652 , 1977 .

10-1 1

## 11 . BIOLOGICA L EFFECT S O F LEA D EXPOSUR E P.4 5

11. 1 INTRODUCTIO N A s note din Chapte r

2 , air-qualit y criteri adocu

ment s presen t

th e scientifi c knowledg e o f th e rela

tionshi p betwee n pollutan t concentration s an dthei r advers e effect s o n publi c healt han dth e environ

ment . Thi s chapte r

addresse s th e importan t huma n healt han dbiologica l effect s o f lea dexposure . Sectio n 11. 2 treat s th e biochemica l an dpathologi

ca l basi s ofth e variou s healt heffect s o f lead , center in g o n enzymolog y an dth e subcellula r an dcellula r aspect s o f

lea deffect s o n th e variou s orga n systems . Sectio n 11. 3 present s abrie f overvie w o f

clinica l lea dpoisonin g —

tha t is , lea dexposur e leadin g t o a constellatio n o f

advers e healt heffect s tha t requir e medica l intervention . I t i s no t th e purpos e o f

tha t subsectio n t o sugges t

tha t airborn e lea dinvariabl y induce s clinica l lea dpoisonin g a s define di n thi s document ; rather , it

seek s t o stat e th e consequence s t o health , bot himmediat e an dlon g term , ofth e up pe r rang e o f exposur e t o thi s pollutan t regardles s o f it s sourc e an dt o stat e thi s i n adiscret e portio n ofth e document . Th e respectiv e section s o n orga n system s hav e bee n ordere daccordin g t o th e degre e o f know n vulnerabilit y t o lea do f

eac hsystem . Th e emphasi s i s no t onl y o n th e thre e system s classicall y considere d mos t sensitiv e —hematopoietic , nervous , an d rena l —bu t

als o o n reproductio n an ddevelopmen t in vie w o f

lead' s effect s o n th e fetus , and , therefore , o n pregnan t

women . Som e effect s ca n b e considere d t o involv e anumbe r

o f orga n systems , an dth e availabl e dat ao n multisystemi c effect s ar e presente d in th e final subsection . Subdividin g th e chapte r o n th e healt heffect s o f lea dint o orga n system s wa s don e fo r th e purpos e o f easie r discussion . I t

mus t b e kep t in min dthat , i n reality , al l system s functio n i n delicat e concer t t o preserv e th e physiologica l integrit y o f th e whol e organism . Furthermore , al l system s ar e interdepen

den t i n th e organism , s o tha t no t onl y ar e effect s in a critica l orga n transmitte dt o othe r system s bu t

als o low-leve l effects , whic hma y b e construe da s les s im

portan t i n asingl e specifi c system , contribut e t o th e cumulativ e o r additiv e advers e effect s o f minima l biologica l respons e in anumbe r o f systems . 11. 2 CELLULA RAN D SUBCELLULA R EFFECT S O F LEA D 11.2. 1 Effect s o n Enzyme s I n general , th e effect s o f lea do n enzyme s ma y b e manifeste din severa l ways . Lead , in commo n wit ha numbe r o f othe r metals , ha s a n affinity fo r anumbe r o f complexin g group s residen t in th e structur e o f man y biomolecula r

entities , suc ha s imidazol e nitrogen , th e cystein e sulfhydry l group , an dth e e amin o grou p o f

lysine . A n effec t

ma y b e imparted , therefore , b y binding-sit e competitio n wit hth e na tiv e ion , b y perturbatio n o f th e structura l integrit y o f enzymes , o r

b y th e impedimen t

o f substrate-enzym e binding . Cellula r damag e cause db y lea dma y als o permi t th e movemen t

o f enzyme s int o th e circulator y system , wit haresultin g elevatio n o f enzym e activit y in , fo r instance , plasma . Th e effect s o f

lea do n enzyme s an denzym e system s hav e bee n studie di n bot hanimal s an dex pose dhuma n subject s an din vitro an din vivo. Clearly , man y ofthes e studie s i n th e literatur e ar e o f margina l relevanc e t o thi s particula r documen t

an d ar e briefl y summarize dfo r referenc e readin g with

ou t evaluation . O n th e othe r

hand , anumbe r

o f othe r enzym e system s ar e o f

suc hdistinc t

relevanc e tha t

the y ar e bette r elaborate di n th e specifi c section s o n orga n effects . Fo r

example , th e enzymolog y relatin g t o th e hem e biosyntheti c pathwa y i s discusse din Sectio n 11.4 . Enzyme s tha t

hav e bee n show n t o b e affecte db y lea di n anima l studie s ar e presente din Tabl e 11-1 , an dresult s o f

studie s o n enzyme s i n human s ar e pre sente din Tabl e 11-2 . 11.2. 2 Organella ran d Cellula rEffect s I t i s o f interes t t o duscus s briefl y th e subcellula r distributio n o f

lea dbefor e furthe r

commen t

i s mad e o n cellula r

effects . 11- 1P.4 6

TABL E 11-1 . ENZYME S AFFECTE D BYLEA D I N ANIMA L STUDIE S Enzym e Lipoamid e dehydrogenas e DNAas e Seru m glutami coxaloaceti c transaminas e (SGOT ) Seru m glutami cpyruvi c transaminas e (SGPT) Seru m alkalin e phosphatas e (AP ) i Erythrocyt e an d live rA P Aci d phosphatas e Catalas e Chollnesteras e a-Mannosidas e /3-Acety l glucosaminadas e Succinat e oxidas e Cytochrom e creductas e Glutamat e dehydrogenas e Cytochrom e oxidas e Rat brai n adeny l cyclas e /3-Glucuronidas e /3-Galactosidas e Effec t o n activit y Inhibite d Enhance d Enhance d an d transitor y Enhance d an d transitor y Lowere d Variabl e Quenche d o r markedl yinhibite d Variabl e Markedl yinhibite d Increase d Increase d Decrease d Decrease d Decrease d Decrease d Decrease d Elevate d Elevate d Referenc e 1 2. 3 4- 7 4- 7 7 7. 8 7,9,1 0 11-1 3 5.6.1 4 1 5 1 5 1 6 1 6 1 6 1 6 1 7 1 8 1 8 TABL E 11-2 . ENZYME S AFFECTE D B YLEA D I N HUMA N STUDIE S Enzym e SGO Tan d SGP T SGO Tan d SGP T Seru m alkalin e phosphatas e Aci d phosphatas e Aldolas e Cholinesteras e Glutathion e reductas e Glucose-6-phosphat e dehydrogenas e Effec t o n activit y Enhance d N o effec t Reduce d N o effec t Enhance d Inhibite d Enhance d Inhibite d Referenc e 19-2 1 22 2 3 24.2 5 2 6 27-2 9 3 0 3 0 Castellin o an dAloj, 3 1 usin g 210 Pb , foun da decreas e i n radioactivit y ove r a24

- t o 72-h r

tim e in

terva l i n th e nuclea r

fractio n an da n increas e o f 210 P b i n th e mitochondri afractio n usin g liver . Ove r th e sam e tim e interval , a n increas e i n radioactivit y occurre di n th e kidne y i n bot hnuclea r an d mitochondria l fractions , an dther e wa s adecreas e in microsomes . Mitochondria l bindin g wa s particu

larl y strong . Similarly , Barltro p e t al. 3 2 measure d203 P b i n heart , liver , kidney , an dsplee n followin g in

traperitonea l (i.p. ) administration . Thei r result s in

dicate dtha t

mos t o f th e lea daccumulate di n th e mitochondria . A detaile dstud y ofth e ra t kidne y b y Goye r

e t al. 3 3 showe dtha t

ove r aprotracte dperio dth e cel l nucleu s accumulate dth e highes t proportio n o f

lead . Unde r lea dchallenge , acellula r reactio n typica l o f avariet y o f

anima l specie s i s th e formatio n o f in

tranuclea r

inclusio n bodies , th e earl y experimenta l histor y o f

whic hha s bee n reviewe db y Goye r an d Moore. 3 4 Th e presenc e o f considerabl e lea din thes e bodie s ha s bee n verifie db y X-ra y microanalyses; 3 5 ultrastructura l studie s sho w tha t thi s entit y consist s o f arathe r dens e cor e encapsulate db y afibrillar y envelope . Th e wor k

o f Goyer, 3 3 3 6 indicate s tha t thes e inclu

sio n bodie s ar e acomple x o f lea dan dprotein , th e protei n moiet y havin g characteristic s o f th e residua l acidi c fraction s o f

protein s i n norma l nuclei . Th e morphologica l integrit y o f thes e inclusio n bodie s collapse s o n treatmen t

in vitro wit hmeta l chelant s suc ha s EDTA . A rol e fo r th e inclusio n bod y a s a cellula r protectiv e mechanis mdurin g transcellula r lea dtranspor t

ha s bee n postulated. 3 6 Ho w th e localizatio n o f lea di n nuclea r

inclusion s relate s t o nuclea r

functio n ha s no t

bee n established ; howeve r Choi e an dRichter 3 7 hav e show n tha t i.p.

- administere dlea denhance s DN A synthesi s an d proliferatio n o f

rena l tubula r

cells . Th e effect s o f lea do n cel l divisio n ar e detaile di n Sectio n 11.2.4 . Disaggregatio n occur s i n th e ribosom e in th e pre senc e oflead.' 3 8 Anima l experiment s an dhuma n studies , mainl y centere do n cellula r

energetic s an dmorphologica l aberrations , hav e show n mitochondri at o b e highl y sensitiv e t o lead . Tera s an dKakhn 3 9 showe dde

crease drespirator y rate s in mitochondri ao f rabbi t tissu e unde r

chroni c lea dchalleng e usin g a ketoglutarate , succinate , an dpyruvat e a s substrates . Phosphorylatio n wa s als o retarded . A marke dsensitivit y ofth e pyruvate-NA D reduc

tas e syste mi n kidne y mitochondri ao f lead-intoxi

cate drat s i s suggeste db y th e wor k o f Goye r an d Krall, 4 0 wh o not e impairmen t o f pyruvate-depen

den t respiratio n usin g ADP/ O ratio s an drespirator y contro l rate s (RCR's ) a s indices . Succinate-medi

ate drespiratio n i n lead-intoxicate drats , however , wa s no t differen t fro mtha t

o f contro l animals . Rhyn e an dGoyer 4 1 stat e tha t thei r observation s o f decrease doxyge n uptak e rate s fo r bot hStat e II I an d I V i n succinate-dependen t respiratio n i n 11- 2P.4 7

mitochondri ao f

th e kidne y fro mlead-intoxicate d animal s ma y b e evidenc e o f decrease dsuccino-ox

idas e enzyme , whic hwoul dals o b e consisten t with decrease dmitochondria l protein . Walton 4 2 reporte da n accumulatio n o f lea din gran ule s produce di n isolate drat-live r mitochondri a followin g incubatio n in medi acontainin g lead , with th e lowe r

en do f th e rang e o f

th e fre e lea dleve l employe dapproachin g tha t foun di n lead-poisonin g victims . I t

wa s note dtha t

lead-ric hgranules , unlik e thos e obtaine dwit hcalcium , wer e no t disperse d afte r treatmen t

withdinitrophenol . Thi s findin g woul dindicat e tha t

lea dremova l afte r

depositio n i s difficult . Th e abov e observation s an dothe r studie s promp t th e suggestio n tha t

lea deffect s ar e twofold : (1 ) energ y diversio n t o th e activ e accumulatio n o f lea dwoul dpreven t

AT Psynthesi s an dth e preserva tio n o f ioni c gradient s in th e membrane ; an d(2 ) th e chemica l actio n o f

lea dwoul dpromot e AT Phy

drolysis , an dlea dwoul dcomple x wit hessentia l S H group s o f

mitochondria l enzyme s an dinterac t wit h anions . Th e net

resul t i s th e inabilit y o f

cell s t o maintai n themselve s structurall y an dmetabolically . Recen t studie s b y Kimme l e t

al. 4 3 o n th e chroni c long-ter mexposur e o f

rat s t o lea dshowe dtha t sub

cellula r effect s o f

lea do n th e rena l syste mwer e ap paren t whe n comparativel y lo w level s o f lea d(5 , 50 , an d25 0 pp min drinkin g water ) wer e administere d prenatall y an du p t o 9 month s o f ag e postnatally . Ligh t microscop y showe dkaryomegal y an d cytomegal y a t

al l dos e levels . Electro n microscopi c examinatio n indicate dswolle n mitochondria , numerou s dens e lysosomes , an dintranuclea r inclu

sio n bodie s a t

5 0 an d25 0 ppm . Furthermore , con siderabl e alteratio n i n th e activit y o f hem e bio

syntheti c pathwa y enzyme s (8-AL A synthetas e an d ferrochelatase ) wa s observe dat 5 0 an d25 0 ppm . Th e bloo dlea dvalue s fo r th e differen t

dos e regi

men s range dfro m5 figldl fo r contro l animal s an d 1 0 figldl fo r th e 5 pp mgrou p t o 2 5 /ig/d l fo r th e 5 0 pp mgrou p an d7 0 figldl fo r th e 25 0 pp manimals . Crame r e t al. 4 4 studie drena l biops y tissu e o f fiv e worker s havin g varyin g period s o f exposur e t o lead . Althoug hth e typica l lead-induce dnuclea r inclusio n bodie s wer e foun donl y i n thos e wit hshor t exposure , al l subject s showe dmitochondria l changes . Mitochondri ai n th e tubula r linin g cell s showe d swellin g an ddistortio n o f cristae , wit hsom e o f

th e mitochondri atransecte db y cristae . A n importan t

commen t

her e relate s t o th e indica

tion s o f impaire dmitochondria l functio n o f erythroi dtissu e in human s tha t ca n b e assesse db y change s i n level s o f

fre e erythrocyt e (actuall y zin c erythrocyte ) protoporphyri n (FEP ) an durinar y coproporphyrin . Th e discussio n o f th e hematopoieti c syste mi n Sectio n 11. 4 include s treat men t o f thi s relationship . I n addition , th e intramitochondria l stage s o f hem e synthesi s hav e bee n suggeste dt o hav e a n intermedi

ar y rol e in introcellula r metabolis man dar e proba

bl y require dfo r

th e continue dtransfe r

o f iro n fro m extracellula r

site s t o normoblast s o f reticulocytes. 454 6 Th e in vivo effect s o f lea do n erythrocyte s i n human s include : accumulatio n o f lead , increase d osmoti c resistance , increase dmechanica l fragility , increase dglucos e consumption , increase dpotassiu m los s i n incubation , decrease dsodium

- an d potassium-dependen t

ATPas e activit y in membran e fragments , an delevatio n in th e numbe r o f immatur e re dcells. 474 9 A mor e detaile ddiscussio n o f erythrocyte-lea drelationship s i s give n i n th e hematopoieti c section . Jand l an dcoworkers 5 0 demonstrate dtha t th e up tak e o f

59 F e b y huma n reticulocyte s wa s almos t com pletel y inhibite db y 5 x IO 4 M lea dan dtha t it s in

corporatio n int o hemoglobi n wa s almos t entirel y prevented . Thi s resulte din a n elevate dleve l o f iro n in th e erythrocyt e membrane . Th e majo r

cellula r patholog y o f

concer n i n th e kidne y wit hreferenc e t o lea di s tha t ofth e proxima l convolute dtubula r

cells . Initia l atroph y o f th e epithelia l cell s i n thi s regio n i s followe db y cel l regeneratio n alon g wit ha n increas e in intertubula r connectiv e tissue , basemen t membran e thickening , an droun dcel l proliferation . Tubula r cel l mitochondri aswel l an ddegenerate , a s note dbefore , an dglomerul i sho w increase dcellularity. 5 1 Tubul e cell s als o sho w th e presenc e o f nuclea r inclusio n bodies , adescriptio n o f whic hha s bee n mad e (vide supra). I n th e suckling-ra t

mode l fo r

lea dencephalopath y employe db y Pentsche w an dGarro 525 3 i n whic hlea d exposur e o f

th e pup s i s vi amil k

fro mmother s fe d lea dcarbonate , epithelia l cel l dysfunctio n in brai n capillarie s i s evidence db y abnorma l permeabilit y t o Trypa n Blu e an dThorotras t (colloida l thoriu m dioxide) . Th e lesio n possibl y center s o n interferenc e witha n energy-regulatin g mechanis mpeculia r t o it s barrie r function . Schlaepfer 5 4 ha s suggeste dtha t th e neuropath y o f lea dpoisonin g ma y b e cause db y initia l damag e t o th e supportin g cell s o f th e nervou s system . Dorsa l roo t ganglio n capsula r

cell s sho w aproliferatio n an d accumulatio n o f

dens e bodie s i n thei r

cytoplas mtha t microscopicall y posses s th e feature s o f aheav y 11- 3P.4 8

metal . I t i s possibl e tha t

th e metabolis mofth e cap sula r cell s i s impaired , whic hthe n cause s th e degeneratio n o f

associate dneuron s an daxon s an d ha s adeleteriou s effec t

o n th e ganglio n cells . A com mo n sit e fo r

intoxicatio n i n bot hth e capsula r cell s an dth e Schwan n cell s o f th e periphera l nervou s syste mha s bee n suggeste dt o accoun t fo r bot hax ona l degeneratio n an dsegmenta l demyelination 5 5 becaus e thes e tw o cell s hav e acommo n embryologi

ca l origin. 5 6 Moor e e t al., 5 7 in astud y ofth e cardia c effect s o f lea di n th e drinkin g wate r o f rats , foun dtha t

whe n rat s wer e expose dt o lea di n drinkin g wate r a t aleve l simila r t o level s previousl y foun din Glasgow , Scot

land , ther e wa s asignifican t inhibitio n o f

cardia c ferrochelatas e an d8-aminolevulini c aci ddehy

dratas e tha t

wa s maxima l afte r

6 months . Moreover , electro n microscop y reveale dmarke dchange s in myocardiu man dmyocardia l mitochondria . 1 1 .2. 3 Effect s o f

Lea d o n Chromosome s Th e examinatio n o f

chromosome s fo r

damag e i s technicall y difficult . Th e evaluatio n ofth e relevanc e o f man y studie s ca n therefor e b e equall y difficult . Becaus e th e appropriat e separatio n o f chromosome s int o tw o chromatid s an dequa l redistributio n o f chromatid s durin g cel l divisio n ar e necessar y fo r th e reproductio n o f

stabl e ne w cell s fo r

th e maintenanc e o f health y tissue , th e implication s o f injur y t o chromosoma l materia l ar e profound , an dinterrup

tio n o f th e processe s involve dca n b e serious . Incor

rec t divisio n o f

cell s b y th e breakag e o f th e chromatid , th e migratio n o f a n inappropriat e se t

o f chromatid s int o eithe r

portio n o f

adividin g cell , th e abnorma l reproductio n o f th e complementar y ne w chromati dt o complet e aviabl e chromosom e i n th e ne w cell , an dothe r

deviation s fro mth e norma l pro ces s ca n produc e abnorma l cells . Suc hchromosoma l aberration s can , therefore , b e responsibl e fo r th e productio n o f

suc hseriou s consequence s a s geneti c defect s i n offsprin g ofth e affecte dorganism . I n th e las t

few years , anumbe r

o f report s hav e bee n publishe do n th e chromosoma l effect s o f ex cessiv e exposur e t o lea di n animals 3 an d humans. 566 8 Althoug hsom e o f thes e report s hav e bee n essentiall y negative, 636 5 other s hav e conclude d tha t ther e i s adefinit e increas e i n th e numbe r o f chromati dan dchromosom e change s i n subject s wh o ar e occupationall y expose dt o lead. 566 2 Thus , th e literatur e i s controversia l i n regar dt o chromosoma l abnormalitie s induce db y exposur e t o lead . O'Riorda n an dEvans 6 3 di dno t fin dan y signifi

can t increas e i n chromosoma l damag e i n mal e worker s expose dt o lea doxid e fume s in ashopbreak

in g yard . Thes e shipbreaker s ha dbloo dlea dvalue s rangin g fro m4 0 t o ove r 12 0 figldl. Schmi de t

al. 6 4 foun dn o evidenc e o f

increase dchromosoma l aber

ration s i n periphera l lymphocytes , studie dbot hin vivo an din vitro, i n lea dmanufacturin g workers . Furthermore , Bauchinge r e t al. 6 5 foun dn o abnor

malitie s i n th e chromosome s o f policeme n wit hele

vate dbloo dlea dlevel s (2 0 t o 3 0 percen t abov e th e mea n fo r th e contro l group) . A n increas e in chromosoma l aberration s i n peopl e occupationall y expose dt o lea dwhos e mea n bloo d lea dvalue s wer e 3 8 t o 7 5 figldl ha s bee n reported , however , b y Forn i an dSecchi 5 8 an db y Schwanit z e t al. 5 6 Moreover , Deknud t e t al. 6 0 reporte d chromosoma l damag e in agrou p o f 1 4 mal e worker s wit hsign s o f

lea dpoisoning . Althoug hth e worker s wer e expose dt o zin c an dcadmiu ma s wel l a s lead , th e author s conclude dtha t lea dshoul db e con sidere dresponsibl e fo r

th e aberrations . Th e stud y b y Forn i an dSecchi 5 8 showe dtha t th e rate s o f chromati dchange s wer e highe r i n 6 5 worker s wit h preclinica l an dclinica l sign s o f lea dpoisonin g bu t wer e no t significantl y raise dfo r worker s wit hpas t poisoning . Forn i e t

al. 6 2 als o examine d1 1 subject s befor e an ddurin g initia l occupationa l exposur e t o lead . Th e increas e i n th e rat e o f abnorma l chromati d metaphase s (th e separatio n ofth e pai r o f chromatid s durin g norma l cel l division ) wa s double dafte r 1 mont ho f

exposure , wa s furthe r increase dafte r

2 months , remaine din thi s stag e u p t o 7 months , an d the n decreased . Th e fac t tha t mos t alteration s wer e o f th e chromati dtype , tha t is , occurrin g in cel l cultur e afte r

DN A synthesis , indicate s tha t thes e coul db e culture-produce daberration s an dma y no t reflec t arealisti c in vivo situation . Also , anumbe r o f participant s droppe dou t in th e late r

stage s o f

thi s study . Thus , th e actua l biologica l significanc e o f thes e result s i s unknown . I n arecen t

report , Bauchinge r

e t al. 6 6 foun dtha t chromosoma l aberration s wer e significantl y in

crease di n agrou p o f

2 4 mal e worker s occupie din zin c electrolysi s an dexpose dt o zinc , lead , an dcad

mium . Th e worker s ha dclearl y elevate dbloo dlea d an dbloo dcadmiu mlevel s i n compariso n wit hacon tro l group . Th e author s emphasize dth e possibilit y o f asynergisti c effec t

o f severa l metal s o n th e chromosomes . The y als o pointe dou t th e similarit y betwee n thi s grou p an dth e grou p studie db y Dek

nud t e t al. 6 0 i n regar dt o exposur e t o acombinatio n o f lead , zinc , an dcadmium . Referrin g t o studie s in

dicatin g th e mutagenicit y o f cadmium , Bauchinge r 11- 4P.4 9

an dhi s colleagues 6 6 wer e incline dt o conside r cad

miu ma s bein g mainl y responsibl e fo r aberrations ; bu t Deknud t

e t al. 6 0 conclude dtha t

th e abnor

malitie s foun dwer e cause dmainl y b y lea drathe r tha n b y combination s o f th e thre e metals . Th e questio n o f

whethe r

chromosoma l abnor

malitie s occu r

in human s a s aresul t o f lea dex posure , eithe r

alon e o r

i n combinatio n wit hothe r pollutants , remain s unanswered. 6 7 Furthermore , th e huma n healt hsignificanc e o f chromosoma l abnor

malitie s see n in lymphocyt e cultures , ametho duse d in som e o f

th e studie s reported , i s no t ye t known. 6 8 An assessmen t

o f th e possibl e mutageni c effect s o f lea di s furthe r

hampere db y th e technica l difficultie s tha t ar e inheren t

in th e stud y o f

chromosomes . 11.2. 4 Carcinogenesi s Lea dsalt s hav e bee n show n t o b e at leas t co-car cinogeni c i n rat s an dmice. 6 9 Th e ultrastructur e o f experimentall y lead-induce drena l tumor s i n animals 7 0 i s characterize db y cellula r an dnuclea r hypertrophy , th e presenc e o f numerou s lysosome s an dmicrobodies , an dth e absenc e ofth e infoldin g o f basa l plasm amembrane s tha t i s normall y see n in rena l tubula r

linin g cells . Thes e tumo r cell s d o no t contai n intranuclea r

inclusio n bodies , an dth e lea d conten t o f th e tumor s i s les s tha n tha t in adjacen t rena l cortex . Rena l adenoma s an dcarcinoma s wer e first observe din rat s b y Zollinger 7 1 in 195 3 follow

in g long-ter minjection s o f lea dphosphate . Late r Kilha me t

al. 7 2 reporte dsimila r

tumor s i n wil drat s believe dt o hav e bee n expose dt o lea dfume s fro m burnin g refus e in acit y dump . Lead-induce drena l epithelia l tumor s hav e sinc e bee n confirme db y a numbe r o f investigators. 70727 3 Swis s mic e fe ddiet s containin g 0. 1 percen t basi c lea dacetat e i"Pb(C 2 H 3 0 2 ) 2 -2Pb(OH) 2 ] develope d bot hbenig n an dmalignan t rena l tumors. 7 3 Th e sam e compoun dfe dt o rat s a t th e 0. 1 o r

1 percen t

leve l similarl y induce dbot hbenig n an dmalignan t kidne y tumors, 707 4 an dth e incidenc e an dsiz e wer e relate d t o th e duratio n o f

lea dfeeding. 7 4 I n mal e Sprague

Dawle y rat s fe dadie t containin g 1 percen t

basi c lea dacetate , Oyas u e t al. 7 5 observe d2 cerebra l glioma s an d1 3 kidne y tumor s i n 1 7 animals . Va n Esc han dKroes 7 3 reporte drena l change s bu t n o neoplasm s in 2 group s o f 2 2 an d2 4 mal e hamster s fed , fo r u p t o 2 years , astandar dlaborator y die t containin g 0. 1 o r

0. 5 percen t

basi c lea dacetate . Rena l tumor s wer e observe di n rat s fe ddiet s containin g 1 percen t lea dacetat e [Pb(C 2 H 3 0 2 ) 2 -3H 2 0], 7 6 an dGoye r an dRhyne 7 7 re porte dtha t

6 0 t o 8 0 percen t

o f rat s o n adie t

contain

in g 1 percen t lea dacetat e fo r

mor e tha n 1 yea r develope drena l adenoma s o r carcinoma s wit ha n in

creas e in bot hsiz e an dincidenc e o f carcinoma s re late dt o duratio n o f

exposure . Subcutaneou s o r

intraperitonea l injection s o f lea d phosphat e repeate dove r aperio do f

severa l month s als o induce drena l tumors . Th e tota l dose s ad

ministere dvarie dbetwee n 12 0 an d68 0 m g lea di n th e animal s developin g th e tumors. 717 8 I n additio n t o rena l neoplasms , tumor s o f th e testes , th e adrenal , thyroid , pituitary , an dprostat e glands , an dth e brai n hav e bee n reporte di n Wista r rat s fe dlea dacetate. 7 9 Th e morphologi c an dco-carcinogeni c effect s o f lea do n th e respirator y syste mwer e studie db y Kobayash i an dOkamoto. 8 0 Mal e an dfemal e golde n hamster s wer e give n acombinatio n o f 1 mg lea dox id e an d1 m g benzo[a]pyren e intratracheall y onc e weekl y fo r

1 0 weeks ; lun g adenoma s occurre di n 1 1 o f th e 2 6 animal s withi n 6 0 weeks . On e adenocar

cinom ao f

th e lun g wa s als o observed . An y difference s in frequenc y o f occurrenc e betwee n male s an dfemale s wer e no t mentioned . Suc htumor s di dno t occu r in animal s give n th e sam e dos e o f lea d oxid e o r benzo[a]pyren e alone . I t shoul db e noted , however , tha t

becaus e lea dcompound s ar e onl y a smal l fractio n o f

tota l particulate s in air , ther e ma y b e enoug hparticulate s eve n withou t lea dfo r benzo[a]pyren e t o b e adsorbe ds o a s t o caus e in

crease dcarcinogenicity . Tetraethy l lea d(TEL ) [Pb(C 2 H 5 ) 4 ] i s a n impor

tant , widel y used , antiknoc k additiv e fo r

moto r fuels . Epstei n an dMantel 8 1 reporte dtha t sub

cutaneou s injectio n o f

0. 6 m g o f

TE Lgive n a s fou r equall y divide ddose s t o Swis s mic e betwee n birt h an d2 1 day s o f

ag e produce dmalignan t lymphoma s in 1 o f 2 6 male s an d5 o f

4 1 females , compare dwit h 1 o f 3 9 male s an dnon e o f

4 8 femal e contro l animals . Th e tumor s wer e observe d3 6 t o 5 1 week s afte r th e first injectio n in treate dfemales . N o definit e relationshi p betwee n carcinogenicit y an doccupationa l exposur e t o lea dha s bee n estab

lishe dfro mhuma n studies . I n 1963 , Dingwall

Fordyc e an dLane 8 2 foun donl y margina l evidenc e fo r an y significan t

incidenc e o f

malignan t

disease s in thei r stud y o f 42 5 person s wh o ha dbee n expose dt o lea dwhil e workin g in abatter y factory . A stud y o f

th e cause s o f

mortalit y amon g lea d smelte r an dlea dbatter y worker s in 197 5 conclude d tha t th e incidenc e o f

malignan t

neoplasms , althoug h somewha t

greate r

tha n expected , wa s no t statisticall y differen t

fro mth e incidenc e in th e non expose dpopulation. 8 3 Thi s seem s t o suppor t th e 11- 5P.5 0

conclusio n of aWorkin g Grou p ofth e Internationa l Agenc y fo r

Researc ho n Cance r

(IARC ) tha t

ther e i s n o evidenc e suggestin g tha t exposur e t o lea dsalt s cause s cance r

i n humans. 6 9 Th e IAR C vie w i s sup porte db y th e fac t

tha t th e comparabl e leve l o f lea d exposur e tha t

ha s bee n associate dwit hmalignan t tumor s i n experiment s o n rodent s i s considerabl y highe r tha n th e toxi c dos e in humans. 6 9 11. 3 CLINICA L LEA D POISONIN G Lea dpoisonin g give s ris e t o recognize dbu t non specifi c syndrome s includin g acut e encephalopathy , chroni c encephalopathy , periphera l neuropathy , chroni c nephropathy , an danemia . Encephalopath y i s th e mos t sever e acut e clinica l effec t o f lea dpoisonin g an dma y emerg e rathe r rapidl y wit hth e onse t o f intractabl e seizure s followe db y com aan dcardiorespirator y arrest . Whe n th e outcom e i s fatal , deat hofte n occur s withi n 4 8 hour s o f

th e onse t

o f encephalopathy . I n it s fulminan t

form , developmen t

o f en cephalopath y occur s in les s tha n aweek . Period s o f vomitin g an dapath y progressin g t o stupo r ar e in

tersperse dwit hperiod s o f hyperirritability , poo r memory , inabilit y t o concentrate , menta l depres

sion , persisten t

headache , an dtremor . Severa l re ports 858 6 indicat e tha t childre n wit hacut e en cephalopath y ma y als o incu r acut e rena l injur y (Fancon i syndrome) , showin g hyperaminoaciduria , glycosuria , an dhyperphosphaturia . Pediatri c patient s wit hlea dpoisonin g frequentl y exhibi t antisocia l behavio r

an dothe r

behaviora l dis

orders , includin g los s o f moto r skill s an dspeech . The y ma y als o exhibi t convulsiv e disorders ; however , ther e ar e n o clinica l feature s tha t dis

tinguis hlead-induce dconvulsion s fro mothe r seizur e disorders . Thes e finding s ar e usuall y associ

ate dwithbloo dlea dlevel s i n exces s o f 6 0 /ug/d l an d wit hincrease ddensit y (i n X-rays ) a t th e en do f

lon g bone s (lea dlines) . Becaus e th e latte r indicate s prolonge dabsorptio n o f lead , thi s clinica l pictur e i s terme dchroni c encephalopathy . Th e abov e i s ver y simila r t o th e patter n see n wit hrecurren t episode s o f acut e lea dpoisonin g wit ho r withou t acut e en cephalopathy , an dth e latte r ha s bee n describe db y Byer s an dLord 8 7 a s wel l a s Perlstei n an dAttala. 8 8 However , ther e ma y hav e bee n unrecognize d episode s o f

acut e encephalopath y a t apreviou s time . Th e periphera l neuropath y o f lea dpoisonin g cen ter s o n moto r

involvement s wit hlittl e effec t o n th e sensor y systems . Thi s involvemen t ma y assum e thre e clinica l forms : (1 ) sever e pai n an dtendernes s i n trun k an dextremit y muscle s givin g way t o weaknes s an dslo w recovery ; (2 ) th e mor e commo n painles s periphera l extenso r

weakness ; an d(3 ) neuropathi c an dmyopathi c feature s tha t ar e indistinguishable . Thi s patter n i s generall y see n in workme n afte r 5 o r mor e year s o f

chroni c exposure . Patient s wit hahistor y o f on e o r mor e episode s o f acut e lea dintoxicatio n develo p anephropath y characterize db y progressiv e an drathe r irreversibl e rena l insufficiency . Progressiv e azotemi aan dsome time s hyperuricemi aar e noted . Lat e lea dnephropa

th y generall y i s recognize da t a n irreversibl e stage . Th e questio n o f

rena l sequela e a s aresul t o f acut e lea dpoisonin g in childre n ha s bee n addresse din severa l reports . Henderson 8 9 note dtha t survivor s o f childhoo dlea dpoisonin g in Australi ademonstrat e a ver y hig hfrequenc y o f

chroni c nephritis . Tepper, 9 0 however , di dno t

confir mthi s in hi s Bosto n studies . Apparently , th e lengt ho f exposur e i s o f

significance , a s Tepper' s subject s ha dincurre dacut e lea dpoison

in g durin g preschoo l year s wherea s th e Australia n group s ma y hav e ha dexposur e t o lea dfo r longe r period s o f

time . Th e anemi ao f

lea dpoisonin g i s hypochromi c an d sometime s microcytic . I t i s als o associate dwit h shortene dre dcel l lif

e span , reticulocytosis , an dth e presenc e o f

basophilic-stipple dcells . Furthe r discus

sio n ofth e hematopoieti c effect s i s containe di n Sec

tio n 11.4 . Klin e studie dfive patient s havin g chroni c lea d poisoning. 9 1 A t

autopsy , evidenc e wa s foun dfo r lea d encephalopath y in all , a s wel l a s evidenc e fo r chroni c myocarditis . Th e latte r wa s characterize db y interstitia l fibrosi s withaserou s exudat e an d relativel y few inflammator y cells . Fro mthes e obser

vations , routin e electrocardiographi c studie s an d clos e scrutin y fo r

evidenc e o f

myocardia l damag e wa s recommende db y th e author. 9 1 Approximatel y 2 5 percen t o f youn g childre n wh o surviv e a n attac k

o f acut e encephalopath y sustai n sever e permanen t

neurologica l sequelae. 929 4 Tw o studies 929 3 hav e indicate dtha t apediatri c victi mo f acut e encephalopath y ha s a n almos t 100 percen t chanc e o f

sever e permanen t

brai n damag e whe n returne dt o th e sam e environment . I n it s mos t

sever e form , acut e lea dencephalopa

th y ma y b e followe db y cortica l atrophy , hy

drocephalu s ex

vacuo, sever e convulsiv e disorder , menta l incompetence , an dblindness . Thes e result s ar e becomin g rare , however , an dsubtl e neurologica l deficit s an dmenta l impairmen t ar e th e mor e com mo n outcomes . Man y childre n withdocumente dprio r attack s o f symptomati c lea dpoisonin g develo p aggressive , 11- 6P.5 1

hostile , an ddestructiv e behavio r patterns . Althoug h seizur e disorde r

an dbehavio r

abnormalitie s ma y diminis hdurin g adolescence , menta l incompetenc e i s permanent. 2

- 8 7 11. 4 HEMATOLOGICA L EFFECT S O F LEA D 11.4. 1 Anemi a Anemi ao f

varyin g degre e i s amanifestatio n (ofte n th e earlies t

one ) o f

clinica l lea dintoxication . Classically , th e anemi ai s mildl y hypochromi c an d sometime s microcytic . Th e anemi ai s associate dwit h reticulocytosi s (becaus e o f th e shortene dre dcel l survival ) an dth e presenc e o f basophili c stippling . Childhoo dlea dpoisonin g i s mos t frequentl y ob

serve di n childre n 1 t o 6 year s ol dan do f lowe r socioeconomi c status ; in bot hthes e group s th e pre valenc e o f

iro n deficienc y i s quit e high . A combina

tio n o f iro n deficienc y an dincrease dlea dintak e result s in mor e sever e anemia . Anemia , however , i s als o observe din childre n withincrease dlea dintak e wh o ar e no t

iro n deficient . Si x an dGoyer 9 5 demon

strate dtha t

dietar y iro n deficienc y in rat s produce d increase dlea dretentio n in liver , kidney , an dbon e wit hincrease durinar y 8-AL A excretion . Kapla n e t al. 9 6 showe dtha t

th e uptak e o f

lea db y erythrocyte s i n th e presenc e o f

iro n wa s decreased . Thes e finding s raise dth e possibilit y tha t iron-deficien t

childre n ar e mor e susceptibl e t o th e toxi c effect s o f lead . Althoug hit

i s wel l know n tha t

anemi aoccur s in sever e lea dintoxication , th e threshol dbloo dlea d leve l at whic hanemi aoccur s i s no t clearl y estab

lished . I n lea dworkers , Sakurai 9 7 coul dno t demon

strat e an y differenc e i n hemoglobi n leve l u p t o a bloo dlea dleve l o f

5 0 figldl. Tol ae t

al. 9 8 reporte d a n effec t o f bloo dlea dleve l o n hemoglobi n in a stud y o f 3 3 worker s a t

th e beginnin g o f

thei r ex posur e t o lea di n a n occupationa l settin g an dfoun d tha t afte r 100 day s o f

exposure , a t

th e tim e whe n th e averag e bloo dlea dleve l ha dreache d5 0 figldl, th e averag e hemoglobi n leve l ha ddecrease dt o 13. 4 g/d l fro mth e initia l valu e o f 14. 4 g/d l (p = < 0.001) . Pueschel 9 9 observe danegativ e correlatio n betwee n hemoglobi n leve l an dbloo dlea dleve l i n 4 0 childre n wit hbloo dlea dlevel s rangin g betwee n 3 0 an d120figldl. I n thi s study , however , th e age s ofth e individua l childre n ar e no t stated . A numbe r

o f othe r studie s als o bea r

ou t th e abov e observa

tion. 10010 2 I t

i s know n tha t

in childre n age d1 t o 6 year s ther e i s aprogressiv e physiologica l increas e i n hemoglobi n leve l an dtha t bot hiro n deficienc y an d lea dintoxicatio n ar e mos t frequen t ir f th e younges t children . Th e mechanis mo f

anemi ai n lea dpoisonin g ap pear s t o b e acombinatio n o f decrease derythrocyt e productio n a s aresul t

ofth e interferenc e oflea dwit h hemoglobi n synthesi s an dincrease ddestructio n a s a resul t o f direc t damag e b y lea dt o th e re dcel l itself . Th e specifi c effect s o f lea da t variou s step s in erythropoiesi s ar e discusse dbelow . Approximatel y 9 0 percen t o f bloo dlea dtravel s withth e erythrocytes 10310 4 a s th e lea di s rapidl y transferre dfro mplasm at o erythrocytes . Rose n e t al. 10 0 hav e show n tha t

plasm alea dlevel s ar e acon stan t 2 t o 3 figldl

ove r arang e o f

1 0 t o 150 figldl whol e blood . McRoberts, 10 5 however , ha s show n tha t th e plasm alevel s ca n fluctuat e considerabl y an dar e associate dwithth e appearanc e o f symptom s in case s o f

occupationa l exposure . Kochen 10 4 ha s show n tha t

erythrocyte s primaril y serv e a s acarrie r fo r bloo dlead , wit habindin g capacit y wel l abov e thos e lea dlevel s associate dwit heve n ver y heav y ex posure . I t

woul dappear , then , tha t th e whol e bloo d conten t o f lea di s relativel y independen t o f hematocrit . 11.4. 2 Effect s o f

Lea d o n Erythrocyt e Morpholog y an d Surviva l I n lea dpoisoning , eve n in absenc e o f iro n defi

ciency , th e erythrocyte s ar e microcyti c an dhy

pochromic . Basophili c stipplin g i s afrequen t bu t in

constan t featur e o f

lea dpoisonin g an dha s bee n employe da s ametho do f monitorin g worker s in th e lea dindustry . Thi s tes t

ha s th e disadvantag e o f bein g nonspecific , a s basophili c stipplin g ma y b e observe d in th e erythrocyte s o f

individual s wit hthalassemi a trai t an din severa l type s o f hemolyti c anemia . Moreover , agoo dcorrelatio n betwee n th e amoun t o f stipple derythrocyte s an dbloo dlea dleve l ha s no t bee n observed. 10 6 Recentl y Pagli aan dValentine 10 7 hav e indicate dtha t

th e basophili c stipplin g i n lea d poisonin g result s fro mth e inhibitio n o f th e enzym e pyrimidine-5'-nucleotidase , whic hunde r norma l condition s play s aprominen t rol e i n th e cleavag e o f residua l nucleotid e chain s tha t persis t i n th e erythrocyte s afte r

extrusio n o f

th e nucleus . Detrease dactivit y o f

thi s enzym e in person s wit h elevate dbloo dlea dlevel s i s observe deve n whe n basophili c stipplin g i s no t morphologicall y evident , an di t probabl y contribute s t o th e shortenin g o f th e erythrocyt e survival . I t i s known , i n fact , tha t a sever e chroni c hemolysi s i s presen t in peopl e wh o ar e geneticall y defectiv e i n pyrimidine-5'

- nucleotidase. 10 8 Osmoti c fragilit y i s decrease din lea dpoisoning . Thi s i s acommo n featur e o f man y microcyti c anemias , a s i t

expresse s th e increase dsurface-to

11- 7P.5 2

volum e rati o tha t

result s fro mth e reduce d hemoglobi n conten t

o f individua l erythrocytes . I n lea dpoisoning , however , an increase dosmoti c resis

tanc e als o result s fro madirec t effec t o f lea do n th e erythrocyt e membran e becaus e increase dosmoti c resistanc e ma y b e produce db y lea din vitro.- 09In

crease dosmoti c resistanc e ha s bee n propose da s a screenin g tes t

fo r lea dpoisonin g i n children. 11 0 Othe r evidenc e o f

direc t damag e t o th e re dcel l membran e i n lea dpoisonin g i s th e markedl y lowere dactivit y o f

th e sodium

- an dpotassium-de

penden t membran e ATPase , whic hi s indispensabl y couple dt o activ e catio n transport. 11 1 Shortenin g o f erythrocyt e surviva l ha s bee n show n b y Hernber g e t al." 2 usin g tritium-labele ddifluorophosphonat e an db y Ber k

e t al." 3 usin g detaile disotopi c studie s of apatien t

withsever e acut e lea dpoisoning . Leiki n an dEng 11 4 observe dshortene dsurviva l tim e i n thre e ou t o f seve n childre n withlea dpoisonin g an d anemia . Thes e studie s indicate dtha t hemolysi s i s no t th e exclusiv e mechanis mo f anemi aan dtha t diminishe derythrocyt e productio n play s a n impor

tan t role . A n additiona l facto r

i s alarg e componen t

o f in

effectiv e erythropoiesis . Thi s wa s demonstrate db y th e detaile dstud y ofth e patien t o f Berk e t al." 3 in who mamarke dincreas e o f labele dstercobili n wa s observe dafte r

administratio n o f

labele d14 C

glycine , ahem e precursor . Th e presenc e o f increase d amount s o f

thi s hem e catabolit e in th e urin e demon

strate s altere dhemoglobi n synthesi s a s aresul t o f metaboli c blockag e o r prematur e intramedullar y destructio n o f

re dcel l precursors , o r both . 11.4. 3 Effec to f

Lea d o n Hem e Synthesi s Th e effect s o f

lea do n hem e synthesi s ar e quit e wel l know n bot hbecaus e o f thei r prominenc e an d becaus e o f

th e larg e numbe r

o f studie s i n human s an dexperimenta l animals . Th e proces s o f hem e syn thesi s result s i n th e formatio n o f protoporphyri n IX , acomple x molecul e fro msmal l buildin g blocks , glycin e an dsuccinat e (a s succiny l coenzym e A) ; i t culminate s wit hth e insertio n o f iro n at th e cente r

o f th e porphyri n ring . Th e initia l an dfina l step s o f hem e synthesi s tak e plac e i n th e mitochondria , wherea s mos t

intermediat e step s tak e plac e in th e cytoplas m(Figur e 11-1) . Hem e i s forme din th e mitochondria , an di t

i s als o a n essentia l constituen t o f th e cytochrom e syste mlocate di n th e inne r cres t o f th e mitochondri athemselve s an di s essentia l t o cel l respiration . Beside s bein g aconstituen t o f th e cytochrom e syste man do f severa l othe r

hem e pro tein s i n th e body , hem e i s th e prostheti c grou p o f MITOCHONDRIA L MEMBRAN E MITOCHONDRIO N

FERRO CHELATAS E SUCCINYLCo A 

# if \

" 6-AL A F o + PROTOPORPHYRI N S-AL A SYNTHETAS E (INCREASE I P b (DIRECTL YO R B Y DEREPRESSION ! 

# t

6-AL A DEHYDRAS E (DECREASE I COPROPORPHYRI N (INCREASE ! I

PORPHOBILINOGE N (PBG ! Figur e 11-1 . Lea d effect s o n hem e biosynthesis . hemoglobin , th e protei n tha t transport s oxyge n fro m th e respirator y syste mt o ever y cel l o f th e body . Hemoglobi n represent s 3 3 percen t o f th e weigh t

o f re dcells ; s o anorma l 70-k g mal e withare dcel l mas s o f 300 0 m l ha s l kg o f

hemoglobin , approx imatel y 3 5 g o f

whic har e heme . Therefore , wit ha re dcel l lif

e spa n o f 12 0 days , th e dail y productio n o f hem e fo r hematopoieti c us e i s onl y aroun d30 0 mg . Lea dinterfere s withhem e synthesi s a t severa l points . Th e tw o mos t

importan t

step s affecte dar e th e condensatio n o f

tw o molecule s o f

8-aminolevulini c aci d(8-ALA ) t o formth e porphobilinoge n rin g (a t th e ste p catalyze db y th e enzyme , 8-aminolevulini c aci ddehydratase ) an dth e insertio n o f iro n int o pro toporphyri n I X (catalyze db y th e enzyme , ferroche

latase) . Othe r

step s in th e hem e synthesi s ar e affecte d b y lead , suc ha s 8-ALA-synthetas e an dcoprogenase ; these , however , ma y b e affecte dindirectl y throug h feedbac k derepression . 11.4.3. 1 EFFECT S O FLEA D O N 8-AMINO

LEVULINI C ACI D DEHYDRATAS E(8-ALAD ) AN D 8-AL A EXCRETIO N Thi s enzym e i s highl y sensitiv e t o th e effec t o f lea d an di s directl y inhibite db y chelatio n o f essentia l S H groups . Th e inhibitio n ma y b e completel y reverse d b y reactivatio n ofth e S H grou p in vitro b y reducin g compound s suc ha s mercaptoetheno l an d dithiothreitol . Th e observatio n tha t 8-ALA D i s in

hibite db y lea dwa s first reporte db y Naka o e t

al." 5 an dDeBruin" 6 in 1968 . Hernber g e t al." 7 demon

strate dtha t

th e logarith mofth e activit y o f 8-ALA D wa s negativel y correlate dwit hbloo dlea dleve l ove r 11-8arang e fro m5 figldl (th e lowes t

valu e observed ) t o 9 5 figldl. I n adetaile dstud y o f 2 5 health y in

dividual s wit hbloo dlea dlevel s belo w 1 6 figldl, th e sam e investigator s foun dasimila r correlatio n eve n in this.lowes t

range." 8 Thes e dat asuggeste dth e direc t inhibitio n b y lea do f 8-ALA D withn o threshol deffec t

becaus e th e enzym e wa s 5 0 percen t inactivate dat

abloo dlea dleve l o f

1 6 figldl an d9 0 percen t inactivate dat

abloo dlea dleve l o f

5 5 figldl. Thes e observation s hav e bee n confirme db y severa l othe r laboratories 11912 3 fo r

th e genera l population , fo r industria l workers , an dfo r children . I n astud y o f 12 3 subjects , includin g 4 4 lea dworker s an d7 9 nonexpose dperson s (bloo dlea drang e o f 4. 5 t o 9. 3 figldl), Wad ae t

al. 12 4 notice dasimila r exponentia l negativ e correlatio n betwee n bloo dlea dan d8

- ALAD . I n asubsequen t investigation, 12 5 th e sam e autho r studie d8-ALA D i

n thre e groups : (1 ) 1 0 familie s (eac hincludin g parent s an don e child ) fro m avillag e fa

r nort ho f Toky o withaverag e bloo dlea d o f 8. 3 figldl

(rang e 5 t o 10) , (2 ) 1 0 familie s fro m centra l Toky o withaverag e bloo dlea do f 12. 8 figldl (rang e 9 t o 17) , an d(3 ) 1 0 mal e worker s with averag e bloo dlea do f

26. 5 figldl

(rang e 1 4 t o 36) . I n thi s s"tudy , asignifican t

negativ e correlatio n betwee n lo g ALA D an dbloo dlea dwa s foun db y combinin g group s 1 , 2 , an d3 o r

group s 1 an d2 . I n th e first group , however , n o suc hcorrelatio n coul db e dem

onstrated . Becaus e thi s latte r grou p comprise donl y 1 0 familie s fro masmal l village , it i s possibl e tha t failur e t o observ e an y relationshi p coul db e cause d b y th e ver y narro w rang e o f bloo dlea d( 5 t o 1 0 figldl) and/o r

b y geneti c factors . Mor e recentl y Granic k e t al. 12 6 studie dth e rati o o f 8-ALA D activit y befor e an dafte r reactivatio n wit hdithiothreito l in 6 5 childre n wit hbloo dlea d level s betwee n 2 0 an d9 0 figldl. B y regressio n analysis , the y estimate di n thi s serie s tha t arati o o f reactivated/nonreactivate d8-ALA D o f 1 (corres

pondin g t o n o inhibition ) woul doccu r a t abloo d lea dleve l o f

1 5 figldl. Becaus e ofth e wid e rang e o f variatio n an dth e smal l numbe r o f observations , however , th e confidenc e limit s o f thei r estimat e ar e quit e large . O n th e othe r hand , Hernber g e t

al." 8 hav e show n anegativ e correlatio n i n individual s withbloo dlea dlevel s belo w 1 6 figldl, wherea s th e lowes t bloo dlea dleve l studie db y Granic k e t al. 12 6 wa s 2 0 figldl. Fo r

thes e reasons , th e observation s o f Granic k e t al. 12 6 d o no t

contradic t

th e evidenc e b y Hernber g e t

al. 118 tha t

8-ALA D i s alread y inhibite d a t th e lowes t

level s o f

bloo dlea dobserve di n human s i n industrialize dcountries . Becaus e th e in

hibitio n o f

thi s enzym e i s adirec t

effec t oflea di n th e blood , it s correlatio n withbloo dlea di s no t surpris

ing , an d8-ALA D activit y ma y b e use dt o estimat e bloo dlea dwithagoo ddegre e o f accuracy . Th e in

hibitio n o f

8-ALA D in erythrocyte s reflect s asimi

la r effec t o f lea din bod y tissues , a s show n b y th e studie s o f

Secch i e t

al. 12 0 whic hdemonstrate dthat , in 2 6 person s withou t

industria l exposur e t o lea d an dwithbloo dlea dlevel s betwee n 1 2 an d5 6 figldl, ther e wa s aclea r

correlatio n betwee n erythrocyt e an dlive r 8-ALA D an dan expecte dnegativ e cor relatio n betwee n bloo dlea dan d8-ALA D i n erythrocytes . Milla r

e t al." 9 showe dtha t

whe n suck

lin g rat s wer e fe ddiet s containin g lea dther e wa s a significan t

an dcommensurat e reductio n o f 8

- ALA D activit y no t

onl y in erythrocyte s bu t als o in live r an dbrai n tissues . I n arecen t stud y b y Roel s e t al., 12 7 however , change s in tissu e ALA D an dfre e tissu e protoporphyri n (FTP ) wer e no t foun dfollow

in g postnata l lea dadministratio n i n th e rat . Lea d wa s administere din th e drinkin g wate r (0 , 1 , 10 , 100 ppm ) fro mparturitio n unti l da y 21 . I n th e offspring , a n increas e i n Pb- B an dareductio n in ALA D ac tivit y wer e foun din th e 1 0 an d10 0 pp mgroup s bu t n o difference s in hematocrit , hemoglobin , o r FE P wer e observed . Lea dstorag e i n th e kidne y ofth e 10 0 pp mgrou p wa s associate dwit hamarke dris e i n kidne y FT Pbu t

n o difference s wer e foun di n eithe r ALA D o r

FT Pin eithe r

liver , heart , o r

brain . Th e inhibitio n o f

8-ALA D i s reflecte din in

crease dlevel s o f

it s substrate , 8-ALA , in urine . Plasm a8-AL A ha s bee n shown 12 8 t o b e elevate di n childre n wit hsever e lea dpoisoning ; however , becaus e o f

th e technica l cumbersomenes s o f th e technique s fo r

measurin g 8-ALA , few dat aar e availabl e o n 8-AL A plasm alevel s at lowe r bloo d lea dlevels . O n th e othe r hand , urinar y 8-AL A ha s bee n use dextensivel y a s a n indicato r o f excessiv e ex posur e t o lead , an di t

ha s eve n bee n suggeste da s a screenin g too l fo r

lea dpoisoning. 12 9 It s us e fo r thi s purpos e has , however , bee n rejecte dbecaus e o f th e wid e rang e o f

individua l variabilit y i n dail y excre tio n observe din som e studies 13013 1 Industria l us e o f thi s techniqu e ha s bee n satisfactory , however . Severa l studie s hav e indicate dtha t a n excellen t correlatio n exist s betwee n bloo dlea dleve l an dth e logarith mo f

th e leve l o f

urinar y 8-ALA . Selande r an dCramer 13 2 first

describe dthi s relationshi p i n 15 0 lea dworker s wit hbloo dlea drangin g betwee n 7 an d9 2 figldl. Thei r

observation s hav e bee n con firmedb y othe r

studies 12312413 3 in whic hasimila r correlatio n wa s observed , i n on e case , eve n i n th e lowe r bloo dlea dleve l range . Selande r an d Cramer 13 2 notice dtha t

if lea dworker s wer e divide d 11- 9P.5 4

int o tw o groups , thos e wit hbloo dlea dlevel s belo w an dabov e 4 0 figldl, tw o differen t linea r correlatio n slope s coul db e derived , althoug hwit halesse r degre e o f correlatio n tha n th e exponentia l relation

shi p derive dfro mth e entir e group . A s cite din th e NA S publication, 2 studie s fro mChisholm' s laborator y showe dasimila r exponentia l correlatio n betwee n bloo dlea dleve l an durinar y 8-AL A i s 5 1 childre n age d1 t o 5 havin g bloo dlea dlevel s rang in g betwee n 2 5 an d7 5 figldl. I n 5 5 adolescent s with bloo dlea dlevel s rangin g fro m8 t o 4 0 figldl, however , n o clea r

correlatio n coul db e observed . I t appear s tha t

apar t fro mthi s las t

observatio n (whic h i s restricte dt o adolescents , th e grea t majorit y o f who mha dbloo dlea dlevel s i n aver y narro w range : 1 4 t o 2 4 figldl), al l othe r studie s reporte dsho w a clea r exponentia l increas e in 8-AL A urinar y excre tio n withincreas e in bloo dlead . Thes e observation s paralle l th e reporte dexponentia l inhibitio n o f th e enzym e 8-ALA D an dindicat e tha t thi s i s on e ofth e earlies t effect s o f

lea do n hem e synthesis . Th e urinar y excretio n o f 8-AL A doe s no t

excee d th e norma l rang e (0. 6 figldl) unti l th e bloo dlea d leve l reache s 4 0 figldl. Th e norma l range , however , i s derive dfro mvalue s obtaine dfro mindividual s wit hbloo dlea dlevel s u p t o 4 0 figldl. I t i s apparen t tha t i f 8-ALA D wer e inhibite db y lea dwithou t an y threshol do f

concentratio n an di f 8-AL A wer e similarl y affected , th e definitio n o f anorma l rang e o f 8-AL A excretio n fo r

individual s withabloo d lea dleve l les s tha n 4 0 figldl woul db e ambiguou s at best . Som e o f

th e discrepancie s reporte din th e literatur e coul din par t

reflec t th e large r

variabilit y o f 8-AL A urinar y excretio n in compariso n with erythrocyt e 8-ALAD . I n adetaile dstud y b y Alessi o e t al. 12 3 o f 16 9 male s withbloo dlea dlevel s rangin g fro m5 t o 150 figldl, th e correlatio n betwee n bloo d lea dan d8-ALA D wa s muc hgreate r tha n withurin

ar y 8-ALA . Fo r

thes e reason s an dbecaus e ofth e un certaint y o f

definin g anorma l range , it i s generall y accepte dtha t

urinar y 8-AL A become s clearl y ab

norma l a t

bloo dlea dlevel s greate r tha n 4 0 figldl. I t ha s bee n postulate dtha t ther e ma y b e an exces s o f 8

- ALA D activity , s o tha t norma l 8-AL A metabolis m i s stil l sustaine db y eve n 50-percent-inhibite d enzym e at

bloo dlea dlevel s nea r 4 0 figldl. Abov e thi s value , however , th e inhibitio n result s in func

tiona l impairmen t

an dclea r

accumulatio n o f

8

- ALA , an dincrease durinar y excretio n ma y b e ob

served . A recen t

stud y suggest s tha t

AL A may , in fact , b e toxi c systemically . Th e relativ e contribu

tion s fro mdecrease dutilizatio n o f ALA , a s aresul t o f ALA D inhibitio n an dth e derepressio n o f ALA

synthetase , t o urinar y level s o f AL A at bloo dlevel s at whic hexcretio n i s significan t canno t b e deter

mine dat thi s time . 11.4.3. 2 EFFECT S O N IRO N INSERTIO N I N PROTOPORPHYRI N Th e accumulatio n o f protoporphyri n i n th e erythrocyte s o f

human s withlea dintoxicatio n ha s bee n know n sinc e th e 1930's. 13 5 It s us e a s a n indica

to r o f lea dbod y burden , however , ha s bee n limite d b y th e technica l difficultie s associate dwit hth e measuremen t

o f protoporphyri n b y solven t partitio n an dspectrophotometry . I n 1972 , th e developmen t o f asimple r

an dmor e accurat e technique , combin

in g simplifie dextractio n an dfluorometry , mad e th e measuremen t

o f protoporphyri n awidel y use dan d accessibl e test. 13 6 A s discusse di n Chapte r 9 , severa l modification s o f

thi s techniqu e hav e bee n developed , includin g an instrumen t tha t measure s protoporphyri n b y direc t fluorescenc e in capillar y bloo dsample s withou t

an y extractio n o r

manipula

tio n o f th e bloo dsample . Accumulatio n o f

protoporphyri n i n th e erythrocyte s i s th e resul t o f decrease defficienc y o f iro n insertio n int o protoporphyrin , th e fina l ste p i n hem e synthesis , whic htake s plac e insid e th e mitochondria . Whe n thi s ste p i s blocke db y th e effec t o f lead , larg e amount s o f protoporphyri n withou t iro n accumulat e in th e erythrocyte , occupyin g th e availabl e hem e pocket s in hemoglobin . Hence , pro toporphyrin , rathe r

tha n heme , i s incorporate din th e hemoglobi n molecul e wher e i t remain s throughou t

th e erythrocyt e lif

e spa n (12 0 days) . Th e accumulatio n o f

protoporphyri n i n lea d poisonin g i s differen t fro mtha t

observe di n erythropoieti c protoporphyria , acongenita l dis

orde r i n whic hexces s protoporphyri n i s produce d afte r hem e synthesi s i s complete . I n tha t case , th e ex ces s o f protoporphyri n forme d(a s aresul t o f acon genita l defec t

in ferrochelatase ) i s attache dt o th e surfac e o f

hemoglobi n a t

asit e tha t

bridge s th e a an df3 -chains o f

hemoglobin. 13713 8 Becaus e thi s typ e o f bon dt o hemoglobi n i s ver y loos e i n erythropoieti c protoporphyria , protoporphyri n diffuse s throug hth e plasm aint o th e ski n wher e it in

duce s photosensitivity . I n lea dintoxication , o n th e othe r hand , th e protoporphyri n in hemoglobi n i s boun dmor e firml y t o th e hem e pocket ; hence , n o diffusio n int o th e plasm aoccur s an dn o photosen

sitivit y i s observed , despit e extremel y elevate d erythrocyt e protoporphyri n levels . A n additiona l importan t differenc e betwee n th e increase dprotoporphyri n leve l in th e erythrocyte s 11-1 0o f

person s wit hlea dintoxicatio n an derythropoieti c protoporphyri ai s th e fac t tha t onl y in th e forme r

i s th e cente r

ofth e protoporphyri n molecul e occupie d b y zinc.' 3 9 Thi s differenc e i s probabl y cause db y th e differen t affinity fo r

zin c o f protoporphyri n in th e hem e pocket . I n lea dintoxication , then , th e largel y prevalen t specie s i s zin c protoporphyrin , wherea s i n erythropoieti c protoporphyri ait i s a n unchelate d protoporphyri n base . Thes e tw o compound s diffe r in fluorometri c spectr aan dth e tw o condition s ma y b e easil y distinguishe db y spectrofluorometry. 14 0 Zin c protoporphyrin , attache di n th e hem e pocke t o f hemoglobin , i s als o th e prevalen t specie s observe din iro n deficiency , anothe r conditio n in whic ha n in

crease dleve l o f

protoporphyri n i s observe di n th e erythrocytes . Accumulatio n o f

protoporphyri n i n th e erythrocyte s i n lea dpoisonin g indicate s afailur e o f th e las t ste p o f hem e synthesis . Thi s coul dresul t eithe r fro madirec t

effec t o f lea do n ferrochelatas e itsel f o r fro ma n effec t

o f lea do n mitochondria l membrane s o f

erythroi dtissu e i n bon e marrow , wit h consequen t

failur e o f

iro n transport . Th e latte r mechanis mwoul dmak e iron , on e o f th e tw o sub

strate s o f ferrochelatase , les s availabl e t o enzym e ac tion , withsubsequen t

accumulatio n ofth e unutilize d substrate , protoporphyri n IX . Interferenc e b y lea dwithth e mitochondria l transpor t o f iro n i n th e normoblas t

appear s t o b e th e mos t likel y mechanis munderlyin g th e increase d leve l protoporphyri n in th e erythrocytes . Fou r fact s suppor t thi s statement : (1 ) iro n accumulatio n withi n th e erythrocyt e i s diminishe db y th e presenc e o f lead , wherea s iro n incorporatio n int o hem e i s com pletel y inhibited ; (2 ) lea di s deposite do n th e mitochondria l membrane , wher e it produce s pro foun dultrastructura l changes ; (3 ) iro n transpor t throug hth e mitochondria l membran e i s ac complishe db y bot henergy-dependen t an denergy independen t

mechanism s tha t

ar e impaire db y lead; 14 1 an d(4 ) i n iro n deficienc y (whe n fer

rochelatas e activit y i s norma l bu t iro n i s scarce ) zin c protoporphyri n boun di n th e hem e pocke t i s ac cumulated , wherea s i n erythropoieti c pro toporphyri a(whe n iro n i s norma l bu t ferro

chelatas e activit y i s decreased 142143 ) fre e pro toporphyri n bas e loosel y attache dt o th e hemoglobi n surfac e i s formed . Experimenta l evidenc e fro manima l studie s an d epidemiologi c huma n studies , usin g intac t mitochondria , hav e demonstrate dth e failur e o f iro n incorporatio n int o protoporphyri n i n th e presenc e o f lead . Thes e studie s canno t clarif y whethe r

th e effec t o f

lea di s exerte do n th e enzym e itsel f o r o n overal l mitochondria l function . I t i s possibl e tha t mitochondria l transpor t o f iro n an dferrochelatas e ar e bot haffecte db y lead . Th e effec t

o f lea do n iro n incorporatio n int o pro toporphyri n i s no t

limite dt o th e normoblas t and/o r t o th e hematopoieti c system . Formatio n ofth e heme

containin g protein , cytochrom e P450 , whic hi s a n in

tegra l par t

o f th e live r

mixed-functio n oxidas e system , ma y als o b e inhibite db y lead. 14 4 Accumula

tio n o f protoporphyri n in th e presenc e o f lea dha s bee n show n t o occu r

als o i n culture dcell s o f chic k dorsa l roo t

ganglion , indicatin g tha t inhibitio n o f hem e synthesi s take s plac e in th e neura l tissu e a s well. 14 5 Thes e observations , an dth e fac t tha t lea di s know n t o disrup t

mitochondria l structur e an dfunc

tion , indicat e tha t

th e lea deffec t

o n hem e synthesi s i s exerte di n al l bod y cells , possibl y wit hdifferen t dose/respons e curve s holdin g fo r effect s i n differen t cel l types . O n th e othe r hand , it mus t b e note dtha t increase dlevel s o f protoporphyri n i n th e erythrocyt e reflec t

a n accumulatio n o f

substrat e an d therefor e impl y afunctiona l alteratio n o f mitochondria l functio n in th e sam e way tha t th e in

crease durinar y excretio n o f urinar y 8-AL A implie s impairment . I n othe r

words , if

areserv e activit y o f ferrochelatas e exists , suc ha s ha s bee n suggeste dfo r 8-ALAD , accumulatio n o f protoporphyri n in th e erythrocyte s indicate s tha t thi s ha s bee n hampere d b y th e lea deffec t

t o th e poin t

tha t th e substrat e ha s accumulated . Fo r

thes e reasons , a s wel l a s fo r it s im

plicatio n o f

th e impairmen t

o f mitochondria l func

tion , accumulatio n o f

protoporphyri n ha s bee n take n t o indicat e physiologica l impairmen t relevan t

t o huma n health. 14 6 Th e elevatio n o f

erythrocyt e protoporphyri n wa s show n t o b e exponentiall y correlate dwit hbloo d lea dleve l b y Piomell i in astud y o f 9 0 children , coverin g th e bloo dlea dleve l rang e fro m5 t o 9 0 /ig/dl. 14 7 I n alate r

stud y o f

103 8 children , 56 8 o f who mha dbloo dlea dlevel s greate r tha n 4 0 /tg/dl, 14 8 thi s correlatio n wa s confirmed , an di t wa s clearl y show n tha t

al l childre n wit hbloo dlea d level s greate r

tha n 6 0 figldl

ha derythrocyt e pro toporphyri n greate r

tha n 25 0 figldl

re dbloo dcell s (RBC's) . Kamholt z e t

al. 14 9 an dSass ae t

al. 15 0 als o showe dasimila r

degre e o f

correlatio n an dindicate d tha t avalu e o f

140 fig FEP/d l RBC' s woul dappea r t o b e amor e appropriat e cut-of f poin t fo r screenin g childre n fo r

lea dpoisoning . Thi s value , als o sug geste db y McLara n e t al., 15 1 wa s accepte db y Piomell i e t

al., 15 2 wh o indicate dtha t mor e tha n 7 0 percen t o f childre n wit habloo dlea dleve l o f 4 0 t o 11-1 1P.5 6

4 9 figldl hav e erythrocyt e protoporphyri n i n exces s o f thi s value . Severa l additiona l studie s hav e con firmedth e exponentia l correlatio n betwee n bloo d lea dan derythrocyt e protoporphyri n i n chil

d ren i40,i53-i56 anc iinleadworkers. 123 ' 133 ' 140 ' 157

. 15 8 Sass ae t al. 15 0 demonstrate dtha t abette r correla

tio n wa s observe dbetwee n bloo dlea dan d erythrocyt e protoporphyri n in childre n withastead y bloo dlea dlevel . Thi s findin g suggeste dtha t asig

nifican t par t ofth e scatte r

observe dwhe n bloo dlea d i s correlate dt o erythrocyt e protoporphyri n o n a rando mbasi s i s th e resul t o f fluctuation s o f

lea d cause db y da y t o da y variatio n an dexperimenta l er ror . Lamol ae t

al. 14 0 demonstrate dtha t th e slop e o f elevatio n o f

erythrocyt e protoporphyri n versu s bloo dlea di s steepe r

i n childre n tha n i n adul t lea d workers . Thi s observatio n wa s confirme db y Roel s e t al. 15 9 wh o als o demonstrate dtha t th e slop e o f elevatio n i s simila r

i n childre n an dfemales . Reiger t e t al. 16 0 an dLev i e t

al. 16 1 als o demonstrate dtha t a n elevatio n o f

erythrocyt e protoporphyri n ca n predic t whic hchildre n ten dt o increas e thei r bloo dlea d leve l an dsuggeste dtha t erythrocyt e protoporphyri n i s amor e valuabl e indicato r o f childhoo dbod y burde n o f

lea dtha n th e bloo dlea dleve l itself. I n adul t workers , th e elevatio n o f erythrocyt e pro toporphyri n wa s show n t o correlat e wit hbloo dlea d level , ALAD , ALA-U , an dth e duratio n o f exposur e t o lead. 15 8 Chishol me t al. 16 2 suggeste dtha t

in childre n erythrocyt e porphyri n i s abette r indicato r o f overexposur e t o lea dtha n bloo dlead . I n additio n t o bein g elevate di n lea dintoxication , erythrocyt e protoporphyrin s ma y als o b e elevate di n iro n defi

ciency , bu t

t o alesse r

degree . Severa l studie s hav e indicate dtha t

erythrocyt e protoporphyri n level s ar e a n excellen t

indicato r

o f th e bod y iro n store 16416 5 an dtha t thes e level s ma y als o b e use dt o discrimi

nat e betwee n th e microcyti c anemi ao f iro n deficien

c y (wher e the y ar e elevated ) an do f thalassemi atrai t (wher e the y ar e normal). 166 " 16 8 Thes e observation s an dth e dat acollecte do n ove r 300,00 0 childre n screene db y bot herythrocyt e pro toporphyri n an dbloo dlea di n Ne w Yor k Cit y wer e th e basi s fo r

th e statemen t

b y th e Cente r

fo r Diseas e Contro l (CDC ) i n whic ha n elevatio n o f erythrocyt e protoporphyri n abov e 6 0 figldl o f whol e bloo din th e presenc e o f

abloo dlea dleve l abov e 3 0 figldl wer e indicate da s cut-of f point s fo r

th e detectio n o f childhoo dlea dpoisoning. 14 6 Mos t studie s o n th e relationshi p betwee n erythrocyt e protoporphyri n an dbloo dlea dhav e focuse do n person s (childre n o r adul t workers ) wit h markedl y elevate dbloo dlead . Som e studies , however , hav e she dligh t o n th e threshol dleve l belo w whic hn o effec t

i s observed . I n astud y o f childre n wit hbloo dlea dlevel s ove r th e rang e o f

2 0 t o 4 0 figldl, Sass ae t

al. 15 0 coul dno t

detec t an y threshol deffect . Dat afro mRoel s e t al., 15 9 wh o studie d14 3 schoo l childre n havin g bloo dlea dlevel s rangin g fro m5 t o 4 0 figldl, indicat e athreshol d effec t at bloo dlea dlevel s betwee n 1 5 an d2 0 figldl. I n astud y b y Piomell i e t al. 16 9 o f 181 6 childre n age d 2 t o 1 2 year s (media n ag e 4. 7 years) , th e threshol d fo r n o effec t

o f bloo dlea do n erythrocyt e proto porphyri n wa s estimate dt o b e 15. 5 figldl, usin g bot h probi t analysi s an dsegmenta l curve-fittin g tech

niques . Becaus e a n elevatio n o f erythrocyt e pro toporphyri n i s cause dals o b y iro n deficiency , i t i s importan t

t o tak e int o consideratio n th e iro n stat e o f th e populatio n unde r

stud y i n an y evaluatio n ofth e relationshi p o f

thi s hematologica l inde x t o lea dex posure . N o informatio n i s availabl e withregar dt o th e iro n stat e o f

th e populatio n studie db y Sass ae t al. 15 0 I n th e Roel s study, 15 9 similarly , n o direc t measurement s o f

th e iro n statu s wer e obtained ; however , th e childre n studie drange di n ag e fro m1 0 t o 1 5 years , agrou p i n whic hiron-deficienc y anemi a i s uncommon . Moreover , th e difference s i n bloo d lea dwer e clearl y relate dt o livin g nea r o r awa y fro m lead-emittin g smelters . Ther e i s n o reaso n t o believ e tha t th e childre n wh o liv e nea r asmelte r

shoul dhav e lowe r iro n store s tha n th e childre n wh o liv e in rura l areas . Also , i n th e sam e study , it mus t b e note dtha t th e hematocri t

ofth e childre n livin g i n th e rura l are a wa s slightl y bu t

significantl y lowe r

tha n th e hematocri t

o f th e childre n livin g nea r th e smelter ; therefore , i

f anything , th e prevalenc e o f an y iro n deficienc y ma y hav e bee n greate r in th e rura l childre n (wit hth e lowes t EP ) tha n in th e childre n livin g nea r

th e smelte r

(wit hth e highes t

EP) . Thes e facts sugges t

tha t iron-deficienc y anemi awa s no t a facto r in th e elevatio n o f

erythrocyt e protoporphyri n observe di n thi s study , bu t tha t thi s E Pincreas e wa s directl y relate dt o lead . I n th e stud y o f Piomell i e t al., 16 9 a n analysi s o f

childre n age d2 t o 4 year s versu s childre n olde r

tha n 4 year s faile dt o sho w an y differenc e in th e EP/bloo dlea drelationship . Thi s indicate s tha t

iron-deficienc y anemia , whic hi s muc h mor e prevalen t

i n th e younge r

children , di dno t

in

fluenc e th e E Presponse . Moreover , i n th e sam e study , th e iro n store s wer e measure di n childre n wit h bloo dlea dlevel s < 1 5 figldl an di n childre n wit h bloo dlea dlevel s o f

1 5 t o 2 8 figldl

an dn o differenc e 11-1 2wa s observed . I t appears , therefore , tha t th e effec t

o f th e lea do n EP , whic hi s extremel y wel l documente d a t th e muc hhighe r

bloo dlea dlevel , occur s als o i n childre n wit hbloo dlea dlevel s betwee n 1 5 an d2 8 figldl. Thes e studie s consistentl y demonstrat e tha t an elevatio n o f

erythrocyt e protoporphyrin , whic hindi

cate s physiologica l impairmen t o f hem e synthesi s an dmitochondria l function , ca n b e detecte din childre n a t

abloo dlea dleve l tha t i s wel l belo w level s normall y encountere din screenin g pro cedures . 11.4. 4 Othe rHematologica l Effect s Th e effect s o f

lea do n 8-ALA D an do n iro n incor

poratio n in protoporphyri n ar e th e bes t known . I n lea dintoxication , however , othe r abnormalitie s o f hem e synthesi s ar e observed . Thes e includ e an in

crease dactivit y o f

8-AL A synthetase, 17 0 whic hma y resul t b y derepression , accordin g t o th e schem e o f negativ e feedbac k

contro l propose db y Granic k an d Levene. 17 1 In vivo inhibitio n o f coproporphyrinoge n an duroporphyrinoge n decarboxylase s in rabbits' 7 2 an dinhibitio n o f

uroporphyrinoge n I synthetase 17 3 hav e bee n reported . O n th e othe r hand , n o ac cumulatio n o f

porphobilinoge n ha s bee n observe din humans . A n increase dexcretio n o f coproporphyri n i n th e urin e o f

lea dworker s an dchildre n wit hlea d poisonin g i s wel l known . Urinar y coproporphyri n ha s bee n use dextensivel y a s aclinica l indicato r o f lea dpoisoning . I t

i s no t known , however , whethe r thi s effec t

result s fro mspecifi c enzym e inhibition , fro mupstrea maccumulatio n o f substrat e secondar y t o inhibitio n o f

iro n incorporatio n int o proto porphyrin , o r

fro mboth ; or , alternatively , whethe r it i s expresse da s adisturbanc e o f coproporphyri n transpor t throug hth e mitochondria l membrane . Similarly , n o dat aar e availabl e t o establis ha threshol dbloo dlea dleve l belo w whic hn o exces s coproporphyri n excretio n in th e urin e take s place . Beside s th e effec t

o f lea do n hem e synthesis , hemoglobi n synthesi s ma y als o b e impaire dbecaus e o f inhibitio n b y lea do f

th e synthesi s o f

globi n (th e protei n moiet y o f

hemoglobin) . Kassena r e t al. 17 4 showe dimpairmen t

o f globi n synthesis . Thi s wor k wa s confirme db y th e result s o f Wad ae t al. 17 0 Whit e an dHarvey 17 5 showe dadecrease dsynthesi s o f a chain s compare dt o /3-globi n chains . Recently , Al i e t al. 17 6 hav e show n a n effec t o n globi n synthesi s in vitro o n huma n reticulocyte s at lea dconcentration s a s lo w a s IO 6 M , whic hcorrespond s t o abloo dlea d leve l o f 20/ig/dl . 11.4. 5 Summar y o f Effect s o f

Lea d o n th e Hematopoieti cSyste m A numbe r

o f significan t

effect s o n th e hematopoieti c syste min human s hav e bee n observe d in lea dpoisoning . Thes e effect s ar e prominen t i n clinica l lea dpoisoning , bu t the y ar e stil l presen t

t o a lesse r degre e eve n in person s withlowe r bod y bur

den s o f lead . Anemi ai s aclinica l fixtur e o f lea dintoxication . I t result s fro mbot hincrease derythrocyt e destructio n an ddecrease dhemoglobi n synthesis . Erythrocyte s ar e microcyti c an dhav e abnorma l osmoti c fragilit y a s aresul t

o f direc t effec t o f lea do n th e cel l membrane , an dsho w basiphili c stipplin g cause db y th e inhibitio n o f

pyrimidine-5'-nucleotidase . Erythrocyt e surviva l tim e i s shortened , an dthi s result s in hemolysis . I n children , athreshol dleve l fo r anemi ai s abou t 4 0 fid Pb/dl , wherea s th e correspondin g valu e fo r adult s i s abou t

5 0 fig Pb/dl . Lea dinterfere s wit hhemoglobi n synthesi s b y in

hibitin g synthesi s o f

th e globi n moiet y an daffectin g severa l step s in th e synthesi s o f th e hem e molecule . Mos t sensitiv e t o lea di n th e hem e syntheti c pathwa y i s th e activit y o f

th e enzym e 8-ALAD , azinc-acti

vate denzym e tha t

mediate s th e conversio n o f tw o molecule s o f

8-AL A int o prophobilinogen . Inhibi

tio n o f thi s enzym e result s in increase dplasm alevel s an durinar y excretio n o f 8-ALA . Lea dals o inhibit s th e las t ste p (incorporatio n o f iro n int o pro toporphyrin) , whic htake s plac e in th e mitochondria , probabl y b y interferenc e withth e mitochondria l transpor t o f iro n an dcoproporphyrin . Thi s effec t result s in th e accumulatio n o f coproporphyrin , whic hi s excrete di n th e urine , an do f pro toporphyrin , whic hi s retaine din th e erythrocytes , in th e hem e molecule . Th e overal l effec t o f lea di s ane t decreas e i n hem e synthesis , which , i n tur n derepresse s th e enzym e involve din th e firs t ste p o f hem e synthesis , 8-AL A synthetase . Inhibitio n o f

8-ALA D occur s a t

extremel y lo w bloo dlea dlevel s an dha s bee n show n t o star t at a bloo dlea dleve l o f

10/ig/dl . Th e resultan t increase d urinar y 8-AL A excretio n als o start s at aver y lo w bloo dlea dleve l an dbecome s pronounce dat abloo d lea dleve l 240/ig/dl . Th e precis e threshol dfo r coproporphyri n excre tio n i s no t

wel l established . I t

i s probabl y simila r

t o th e threshol dfo r

8-ALA , bu t

i t i s les s specific . An increas e i n erythrocyt e protoporphyri n occur s a t a threshol dbloo dlea dleve l o f approximatel y 1 6 /ig/d l in children . I n adul t females , th e threshol di s 11-1 3P.5 8

probabl y similar . I n adul t males , th e threshol di s probabl y slightl y highe r (2 0 t o 2 5 /ig/dl) . Th e threshol dfo r

increas e in 8-AL A synthetas e i s no t es tablished , bu t

increase s hav e bee n notice dat bloo d lea dlevel s o f

24 0 /ig/dl . Althoug hdoub t

exist s a s t o th e health-effect s sig

nificanc e o f

8-ALA D inhibition , increase durinar y 8-AL A excretio n abov e 4 0 figldl i s accepte da s an effec t probabl y reflectin g physiologica l impair

ment. 2 Elevatio n o f

erythrocyt e protoporphyri n ha s th e sam e implicatio n o f physiologica l impairmen t in vivo a s i s foun din urinar y 8-ALA . Also , becaus e elevatio n o f

erythrocyti c protoporphyri n indicate s impairmen t

o f mitochondria l function , it i s con sidere do f

greate r physiologica l relevance. 17 7 Fo r thes e reasons , th e consensu s o f clinician s wh o partic

ipate di n th e preparatio n ofth e statemen t in 197 5 b y CD C togethe r

withth e America n Academ y o f Pediatric s wa s tha t

thi s findin g shoul db e use da s a n indicato r o f asignifican t

an dworrisom e bod y burde n o f

lead . 11. 5 EFFECT S O F LEA D O N NEURO PHYSIOLOG Y AN D BEHAVIO R Neurologica l an dbehaviora l deficit s hav e lon g bee n recognize da s som e o f th e mor e sever e conse quence s o f

toxi c exposur e t o lead. 17818 2 Wha t level s o f lea dexposur e ar e necessar y t o produc e specifi c deleteriou s neurologica l o r behaviora l effect s an d whethe r suc heffect s ar e reversible , however , hav e bee n controversia l medica l issue s extensivel y de

bate dsinc e th e earl y 1900's . M uc ho f th e impetu s fo r debat e o n th e subjec t ha s bee n generate db y progressivel y increasin g medica l concer n ove r a n evolvin g scientifi c literatur e tha t ha s consistentl y suggested , a s mor e informatio n i s gained , tha t lea d exposur e level s previousl y accepte da s harmles s ar e actuall y sufficien t

t o caus e significan t

neurologica l o r behaviora l impairments . A t presen t i t i s generall y accepte dthat , a t

toxic , hig hlevel s o f

lea dexposur e tha t produc e bloo dlea dlevel s greate r tha n 8 0 t o 10 0 /ig/dl , aperso n i s a t unacceptabl e ris k

fo r th e occurrenc e o f

th e clinica l syndrom e o f fulminan t lea dencephalopathy . Thi s syndrom e include s neurologica l an dothe r symptom s o f

suc hseverit y tha t immediat e medica l attentio n and , frequently , hospitalizatio n i s demande din orde r t o avoi dir

reversibl e neura l damag e o r death . Th e ris k

in

volve di s unacceptabl e becaus e o f th e unpredic

tabilit y ofth e symptom s observe da t hig hbloo dlea d levels . Base do n th e literatur e reviewe dbelow , i t no w als o appear s tha t lowe r level s o f

lea dex posure , yieldin g bloo dlevel s belo w 8 0 /ig/dl , pro duc e muc hles s well-define dbu t medicall y signifi

can t neurobehaviora l deficit s i n apparentl y asymptomati c adult s an dchildren , tha t is , i n th e ab

senc e o f th e neurologica l symptom s o r othe r sign s tha t typif y acut e lea dintoxicatio n requirin g immedi

at e clinica l treatment . Th e rang e o f

lea dexposure s necessar y t o produc e th e mor e subtle , subclinica l neurobehaviora l deficit s i s difficul t

t o estimat e withcertaint y an dremain s a matte r o f considerabl e controversy . Ther e i s som e evidenc e reviewe dbelo w tha t suggest s tha t

suc h effect s ma y occu r

a t bloo dlea dlevel s eve n a s lo w a s 3 0 t o 4 0 /ig/dl , wherea s certai n othe r negativ e find

ings sugges t

th e lac k

o f neurobehaviora l effect s at bloo dlea dlevel s les s tha n 8 0 /ig/dl . I n a n effor t t o estimat e th e exposur e level s necessar y fo r manifesta

tio n o f th e ful l rang e o f

neurobehaviora l effect s o f lead , th e presen t

discussio n wil l criticall y revie w th e literatur e dealin g withth e obviousl y toxi c effect s o f hig hleve l lea dexposure s an dwit hth e mor e subtl e neurobehaviora l effect s associate dwit hlowe r ex posur e levels . Th e relevan t

literatur e o n th e neurobehaviora l effect s o f lea dha s bee n derive dfro mstudie s o f bot h human s an dothe r

mammalia n species . Suc heffect s hav e bee n indexe db y mean s o f avariet y o f

ap proaches , including : (1 ) th e assessmen t o f structura l neuropatholog y b y classica l histologica l an d ultrastructura l analyse s o f morphologica l damage ; (2 ) th e analysi s o f

altere dneurochemica l parameter s o r processe s b y variou s biochemica l assays ; (3 ) th e assessmen t

o f altere delectrophysiologica l response s in bot hth e centra l an dperiphera l nervou s system ; (4 ) th e assessmen t

o f neurobehaviora l effect s bot hb y neurologica l examination s an ddivers e type s o f behaviora l testin g methods ; an d(5 ) th e assessmen t o f alteration s i n neuropharmacologica l response s affectin g man y o f

th e type s o f

variable s assesse db y th e othe r approaches . Th e effect s o f toxic , high-leve l exposure s t o lea dhav e bee n wel l documente db y mos t ofthes e approaches . A t lower-leve l exposures , however , th e demonstratio n o f lea deffect s b y an y o f th e abov e type s o f

assessment s ha s bee n complicate d b y severa l othe r

methodologica l consideration s tha t shoul db e note da s aprelud e t o an y critica l revie w o f th e literature . Dat aabou t

lea dexposur e hav e bee n obtaine dvi a tw o basicall y differen t methods , epidemiologica l an dexperimental . Unfortunately , thes e methodologica l technique s ar e highl y correlate d wit hth e specie s studied ; tha t is , epidemiologica l techniques , wit hthei r

uniqu e problems , provid e mos t huma n data , an dexperimenta l technique s ar e 11-1 4use dt o provid e mos t nonhuma n data . Althoug h epidemiologica l studie s hav e immediat e environ

menta l relevanc e at

th e huma n level , ther e ar e ofte n difficul t problem s associate dwit hinterpretatio n o f th e findings . Wit hepidemiologica l studies , th e exac t parameter s o f

th e mos t

recen t exposur e level , th e duratio n o f

an y leve l o f

exposure , an dth e mod e o f intak e usuall y canno t

b e entirel y known . Similarly , an y previou s lea dlevel s an dexposur e duration s usuall y canno t

b e definitivel y established . I t i s als o possibl e tha t

othe r variable s tha t

wer e highl y corre late dwithth e presenc e o f environmenta l lead , suc h a s socioeconomi c level , previou s behaviora l o r neurologica l damage , etc. , ar e responsibl e fo r th e effect s observe drathe r tha n lea dexposur e alone . Ther e i s anee dfo r

appropriat e an dsensitiv e measure s o f

exposur e effects , especiall y whe n testin g fo r low-leve l effect s fo r

whic hless-than-dramati c neurobehaviora l deficit s ca n b e expected . Neverthe

less , th e contributio n o f lea dexposur e t o an y neurobehaviora l deficit(s ) ca n b e reasonabl y esti

mate dwit hprope r

control s fo r

man y o f

th e abov e extraneou s factors . Obviousl y suc hparameter s a s exposur e level s an d duration s ca n b e define dwithmuc hmor e precisio n in experimenta l studie s carrie dou t in th e laborato

ry . Unfortunately , however , appropriat e experimen

ta l design s ar e frequentl y lacking . I n addition , en vironmenta l relevanc e o f experimenta l laborator y dat ai s limite db y tw o majo r considerations . Th e mos t seriou s o f

thes e i s th e fac t

tha t nonhuma n model s are , o f

necessity , typicall y use dfo r th e estab

lishmen t o f dose-respons e curves , an dit i s wel l know n tha t

alarg e specie s differenc e exist s in sen sitivit y t o lead, 5 2 s o tha t adequat e nonhuma n ex posur e model s ar e difficul t t o devise . A secon d proble mi s tha t

anima l experiment s frequentl y us e dose s o f lea dmuc hhighe r

tha n woul db e expecte dt o occu r i n th e environment . Beside s th e questio n o f ex posur e levels , experimenter s mus t atten dt o prope r experimenta l control s fo r possibl y reduce dnutritio n level s becaus e o f

foo dpalatability , i

f th e deliver y syste mi s vi afoo do r

water ; effect s o f

altere dmater na l behavior , i

f th e deliver y i s vi ath e mother' s mil k o r th e placenta , etc . Further , i f centra l nervou s syste m(CNS ) alteration s ar e noted , i t i s ofte n difficul t t o separat e damag e cause db y direc t versu s indirec t effect s o n neura l tissue . Again , despit e th e abov e difficulties , usefu l dat ao n th e neurobehaviora l effect s o f lea dhav e bee n obtaine d throug hanima l studies , withpotentia l implication s fo r understandin g huma n exposur e effects . Ke y variable s tha t

hav e emerge din determinin g th e effect s o f lea do n th e nervou s syste minclud e (1 ) th e duratio n an dintensit y o f exposur e an d(2 ) ag e a t exposure . I n referenc e t o ag e a t exposure , evidenc e exist s fo r

greate r vulnerabilit y o f

th e developin g nervou s syste min th e youn g tha n o f th e full y mature dnervou s syste min adults . Particula r atten tio n will , therefore , b e accorde dt o th e discussio n o f th e neurobehaviora l effect s o f lea din childre n a s a specia l grou p a t

risk . 11.5. 1 Huma n Studie s 11.5.1. 1 EFFECT S O FHIGH-LEVE LLEA D EXPOSURE S Th e severel y deleteriou s effect s o f exposure s t o hig hlevel s o f

lead , especiall y fo r

prolonge dperiod s tha t produc e over t

sign s o f acut e lea dintoxication , ar e b y no w wel l documente din bot hadult s an d children . Th e mos t

profoun deffect s tha t

occu r in adult s ar e referre dt o a s th e clinica l syndrom e o f lea dencephalopathy , describe di n detai l b y numerou s investigators. I8318 6 Earl y feature s o f th e syndrom e tha t

ma y develo p withi n week s o f initia l exposur e includ e dullness , restlessness , irritability , poo r attentio n span , headaches , muscula r tremor , hallucinations , an dlos s o f memory . Thes e symptom s may progres s t o delirium , mania , convulsions , paralysis , coma , an ddeath . Th e onse t o f suc hseriou s symptom s ca n ofte n b e quit e abrupt , wit hconvul

sions , coma , an deve n deat hoccurrin g ver y rapidl y in patient s tha t

shortl y befor e wer e apparentl y asymptomati c o r

exhibite dmuc hles s sever e symptom s o f

acut e lea dintoxication. I8518 7 Symptom s o f

encephalopath y simila r t o thos e tha t occu r in adult s hav e bee n reporte dt o occu r in in

fant s an dyoun g children, 8590 ' 8518818 9 wit ha markedl y highe r

incidenc e o f

sever e en cephalopathi c symptom s an ddeath s occurrin g in the mtha n i n adults . Thi s ma y reflec t th e greate r difficult y i n recognizin g earl y symptom s in youn g childre n tha t

allow s intoxicatio n t o procee dt o a mor e sever e leve l befor e treatmen t i s initiated . I n regar dt o th e ris k

o f deat hin children , th e mortalit y rat e fo r prechelatio n therap y perio dencephalopath y case s wa s approximatel y 6 5 percent. 19 0 Variou s author s hav e reporte dth e followin g mortalit y rate s fo r childre n experiencin g lea dencephalopath y sinc e th e inceptio n o f

chelatio n therap y a s th e standar d treatmen t

approach : Enni s an dHarrison, 19 1 3 9 per cent ; Agerty, 19 2 2 0 t o 3 0 percent ; McKhan n an d Vogt, 18 9 2 4 percent ; Mellin s an dJenkins, 19 3 2 4 per cent ; Levinso n an dZeldes, 19 4 1 9 percent ; Tanis, 19 5 1 8 percent ; an dLewi s e t al., 1 9 5 percent . Thes e data , a s wel l a s othe r

dat atabulate dmor e recently, 2 indi

11-1 5P.6 0

cat e tha t onc e lea dpoisonin g ha s progresse dt o th e poin t o f encephalopath y alife-threatenin g situatio n clearl y exist s and , eve n wit hmedica l intervention , i s ap t t o resul t

i n afata l outcome . Th e morphologica l finding s in case s o f fata l lea d encephalopath y vary.' 97 *' 9 9 O n macroscopi c ex aminatio n th e brain s ar e ofte n foun dt o b e edematou s an dcongested . Microscopi c finding s o f cerebra l edema , altere dcapillarie s (endothelia l hy

pertroph y an dhyperplasia) , an daperivascula r glia l proliferatio n ar e ofte n noted . Neurona l damag e i s variabl e an dma y b e cause db y anoxia . I n som e case s gros s an dmicroscopi c change s ar e minimal. 19 8 Th e neuropathologi c finding s a s reporte dar e essentiall y th e sam e fo r

adult s an dchildren . Lea dencephalopa

th y i s considere db y som e t o b e primaril y a vasculopathy , wit hth e encephalopath y reflectin g perturbe dblood-brai n barrie r function; 19819 9 tha t is , damag e t o neurona l element s ma y b e secondar y t o lea deffect s o n th e vascula r system . Evidenc e fo r suc heffect s ha s bee n advance db y Pentschew. 19 8 Pentschew 19 8 describe dneuropatholog y finding s fo r 2 0 case s o f

acut e lea dencephalopath y in infant s an dyoun g children . Th e mos t commo n findin g wa s activatio n o f

intracerebra l capillarie s characterize d b y dilatio n ofth e capillarie s withswellin g ofth e en dothelia l cells . Diffus e astrocyti c proliferatio n in th e gra y an dwhit e matte r

wa s als o present . Accordin g t o Pentschew , thi s proliferatio n i s th e earlies t morphologica l respons e t o a n increas e i n per meabilit y o f

th e blood-brai n barrie r (dysoria) . Concurren t

wit hth e dysori c alteration s wer e change s tha t

Pentschew 1 9 8 attribute dt o hemodynami c disorders . Thes e ischemi c change s wer e manifeste da s cel l necrosis , perineurona l in

crustations , o r

neuronophagi a(los s o f neurons) . Th e isocorte x an dth e basa l gangli awer e area s o f pre dilectio n fo r

th e ischemi c changes . Pentsche w con clude dtha t

th e structura l change s i n infantil e lea d encephalopath y ar e amixtur e o f dysori c an d hemodynami c parenchyma l alterations . I n th e cerebellum , whic hin arestricte dsens e i s th e pre dilectio n are ao f

damage , th e change s ar e purel y dysoric . I n additio n t o producin g th e abov e effect s o n th e CNS , lea dals o clearl y cause s damag e t o periphera l nervou s system s (PNS ) o f bot hma n an danimal s a t toxic , hig hexposur e levels . Th e PN S change s in

volv e predominantl y th e larg e myelinate dmoto r fibers. 200 Pathologi c change s i n th e PN S consis t o f segmenta l demyelinatio n an din som e fibers , axona l degeneration. 20 0 Th e lea deffec t appear s t o b e in th e Schwan n cell , wit hconcomitan t disruptio n o f

th e myeli n membranes. 20 1 Remyelinatio n ha s bee n ob

serve din anima l studies , suggestin g eithe r tha t th e lea deffec t

ma y b e reversibl e o r

tha t no t al l o f th e Schwan n cell s ar e affecte dequally. 20 1 Report s o f pe s cavus deformitie s resultin g fro mol dperiphera l neuropathie s i n humans, 20 2 however , sugges t tha t lead-induce dneuropathie s o f sufficien t

severit y coul dresul t

in permanen t

periphera l nerv e damage . Morphologically , th e neuropath y i s charac

teristicall y detectabl e onl y afte r prolonge do r

hig h exposur e t o lea do r

both ; dat afro mexperimenta l studie s indicat e tha t

ther e ar e distinctl y differen t sensitivitie s amon g differen t species . Perhap s o f

eve n greate r

concer n tha n th e occur renc e o f fatalitie s ar e th e neurologica l sequela e tha t occu r in case s o f

sever e o r

prolonge dnonfata l episode s o f

lea dencephalopath y tha t ar e qualitativel y quit e simila r t o thos e see n withman y type s o f traumati c o r

infectiou s cerebra l injury , with th e occurrenc e o f

permanen t

sequela e bein g mor e commo n i n childre n tha n in adults. 859019 3 Th e mos t sever e sequela e in childre n ar e cortica l atrophy , hy

drocephalus , convulsiv e seizures , an dsever e menta l retardation. 859019 3 Mor e subtl e sequela e als o occur , suc ha s impaire dmoto r coordination , altere dsenso ry perception , shortene dattentio n span , an dslowe d learning . Thes e latte r

effect s hav e bee n reporte din childre n withknow n hig hexposure s t o lea dbu t withou t ahistor y o f

th e life-threatenin g form s o f acut e encephalopathy. 85 T 86

- 9 '' 20 3 O f historica l in

teres t her e i n relatio n t o th e extremel y slo w progres s in recognizin g th e ful l consequence s o f lea dintox

icatio n i s th e fac t

that , althoug hman y case s o f child

hoo dlea dpoisonin g ha dbee n reporte dsinc e th e earl y 1900's,' 80 *' 8 2 it

wa s severa l decade s befor e th e wor k o f McKhan n an dVogt 18 9 an dByer s an d Lord 8 5 calle dattentio n t o th e long-ter mirreversibl e neurobehaviora l sequela e o f acut e lea dintoxication . Establishin g precis e threshol dvalue s fo r lea dex posure s necessar y t o produc e th e abov e acut e intox

icatio n symptom s o r

sequela e in human s i s difficul t in vie w ofth e usua l inaccessabilit y o f extensiv e dat a o n environmenta l lea dlevel s contacte db y th e vic

tim , th e perio do f

exposure , o r

th e bod y burden s o f lea dexistin g prio r

t o th e manifestatio n o f clinicall y significan t

symptoms . Nevertheless , enoug hinfor

matio n i s availabl e t o allo w fo r reasonabl e estimate s t o b e mad e regardin g th e rang e o f bloo dlea dlevel s neede dt o produc e acut e encephalopathi c symptom s o r death . Accordin g t o Kehoe 20420 6 bloo dlea d level s wel l i n exces s o f

12 0 /ig/d l ar e usuall y necess ar y t o produc e suc hdeleteriou s irreversibl e effect s fo r adults . Recurren t

bout s o f

lea dintoxicatio n in 11-1 6P.6 1

th e absenc e o f

acut e encephalopath y ma y als o lea d t o progressiv e menta l deterioration . Othe r dat aex ist , however, 18 7 tha t

sugges t tha t acut e lea dintoxica

tion , includin g sever e gastrointestina l symptom s o r sign s o f encephalopath y o r

both , ca n occu r

in adult s a t lea dlevel s somewha t

les s tha n 100 /ig/dl ; bu t am biguitie s i n thes e dat amak e interpretatio n difficult . Th e dat ao n threshol dlevel s fo r childre n indi

cat e tha t lowe r bloo dlea dlevel s hav e bee n asso ciate dwit hth e occurrenc e o f acut e encephalopath y symptom s an ddeath . Probabl y th e mos t extensiv e compilatio n o f

informatio n bearin g o n thi s poin t i s a summarization 18 7 o f

dat afro mth e wor k o f Chisholm 8420 7 an dChishol man dHarrison. 9 0 Tha t dat acompilatio n relate s th e occurrenc e o f acut e en cephalopath y an ddeat hi n childre n in Baltimor e t o bloo dlea dlevel s determine db y th e Baltimor e Cit y Healt hDepartmen t

(dithizon e method ) betwee n 193 0 an d1970 . Elevate dbloo dlea dlevel s associ

ate dwit hasymptomati c case s o r les s sever e sign s o f acut e lea dpoisonin g wer e als o tabulated . Asymptomati c increase dlea dabsorptio n wa s ob

serve da t bloo dlevel s rangin g fro m6 0 t o 30 0 /ig/d l (mea n = 10 5 figldl). Acut e lea dpoisonin g symptoms , othe r

tha n sign s o f

encephalopathy , wer e observe dfro mapproximatel y 6 0 t o 45 0 /ig/d l (mea n = 17 8 /ig/dl) . Sign s o f mil dencephalopath y (hy

perirritability , ataxia , convulsions ) an dsever e en cephalopath y (stupor , coma , convulsion s repeate d ove r a24-h r perio do r

longer ) wer e associate dwit h bloo dlea dlevel s o f

approximatel y 9 0 t o 70 0 o r 80 0 /ig/dl , respectivel y (mean s = 32 8 an d33 6 /ig/dl , respectively) . Th e distributio n o f bloo dlea dlevel s associate dwit hdeat h(mea n = 32 7 /ig/dl ) wa s es sentiall y th e sam e a s fo r level s yieldin g eithe r

mil d o r sever e encephalopathy . Thes e dat asugges t tha t threshol dbloo dlea dvalue s fo r deat hin childre n ar e essentiall y identica l t o thos e fo r acut e encephalopa

th y an dtha t

suc heffect s ar e manifeste di n childre n startin g a t

bloo dlea dlevel s o f

approximatel y 10 0 /ig/dl . Othe r

evidenc e reviewe dbelow , however , suggest s tha t

th e threshol dfo r

acut e encephalopath y effect s i n th e mos t

highl y susceptibl e childre n may , in som e rar e instances , b e somewha t lowe r tha n th e 10 0 /ig/d l figur e arrive da t o n th e basi s o f

th e Baltimor e dat acompilatio n presente dabove . Occasionall y appearin g in th e literatur e sinc e th e 1930' s ar e scattere dreport s o f acut e lea dencepha

lopath y o r

deat hoccurrin g i n childre n at wha t wer e formerl y considere dt o b e moderatel y elevate d bloo dlea dlevels . Fo r

example , Cumings 18 5 liste d reference s t o studie s o n acut e lea dencephalopath y tha t appeare dfro m193 8 t o 1956 . Severa l ofth e re port s purportedl y demonstrate dacut e encephalopa

th y in childre n at

bloo dlea dlevel s eve n dow n t o 3 0 t o 5 0 /ig/dl . Detaile danalyse s o f th e article s referenced , however , indicat e tha t th e actua l dat a reporte di n mos t

di dno t clearl y associat e suc hlow

leve l exposure s t o th e occurrenc e o f acut e en cephalopath y symptoms . Still , case s in a t leas t som e o f th e reference darticle s an din othe r report s reviewe dbelo w sugges t tha t acut e encephalopath y occurre di n afew childre n a t bloo dlea dlevel s belo w 100 /ig/dl . Again , th e ambiguitie s in thes e dat aregardin g confirmatio n o f lea dexposur e an d eliminatio n o f

alternativ e etiologica l factor s mak e interpretatio n difficult . A furthe r precautio n ha s t o d o wit hth e analytica l method s themselve s in term s o f usin g goo dmethod s wit hskille dpersonnel . I n 1938 , Gant 20 8 reporte do n fiv e case s o f acut e lea dencephalopath y in childre n unde r 2 year s o f age . Bloo dlea dlevel s o f 6 0 an d8 0 /ig/dl , a s wel l a s 190 , 240 , an d32 0 /ig/dl , wer e obtaine dfo r th e differen t childre n upo n firs t

admissio n t o th e hospi

tal . Al l fiv e ha dconvulsions . Smith 18 7 liste da3

- year-ol dfemal e patien t a s havin g abloo dlea dleve l o f 6 0 /ig/d l a t

th e tim e o f

acut e lea dintoxicatio n fro mpain t

ingestion , followe db y deat hattribute dt o plumbis m2 day s afte r

a7 0 /ig/d l readin g wa s ob

taine ddurin g aperio dwhe n onl y mil dsymptom s o f lea dpoisonin g wer e present . I n 1956 , Bradle y e t al. 20 9 reporte dtha t

1 9 childre n unde r

5 year s ol d fro malo w incom e are ao f Baltimor e wer e foun dt o sho w CN S symptom s tha t include dirritability , lethargy , o r

convulsion s at

bloo dlea dlevel s below , a s wel l a s above , 10 0 figldl. Eigh t childre n wh o ha d bee n previousl y classifie da s asymptomati c an dwh o ha dbloo dlea dlevel s o f 5 0 t o 8 0 /ig/d l wer e late r hospitalize ddurin g th e study 21 0 fo r treatmen t

o f acut e lea dencephalopathy ; bloo dlea dlevel s a t th e tim e o f late r hospitalizatio n wer e no t reporte dbu t wer e likel y furthe r

elevated . Othe r

dat aar e re ported 2 " o n 1 0 childre n fro malow-incom e are ao f Providence , Rhod e Islan dwh o wer e selecte da t 4 t o 8 year s o f

ag e fo r afollow-u p investigatio n o f possi

bl e long-ter mneurobehaviora l deficit s resultin g fro mearlie r

acut e encephalopath y episodes . Bloo d lea dassay s obtaine da t

th e tim e o f

th e initia l hospi

talizatio n o f

th e childre n becaus e o f acut e en cephalopath y symptom s ( 4 ou t o f 1 0 ha dconvul

sions , 8 ou t

o f 1 0 ha dataxia , 7 ou t

o f 1 0 ha ddrowsi

ness , an d6 ou t

o f 1 0 ha dirritability ) yielde dmax imu mbloo dlea dvalue s tha t average d8 8 ± S.D . 4 1 /ig/dl . Becaus e individua l case s wer e no t described , however , n o clea r

associatio n betwee n particula r lea dintoxicatio n symptom s an dspecifi c bloo dlea d 11-1 7P.6 2

level s ca n b e established . Overall , th e abov e report s sugges t tha t a t leas t som e childre n —

perhap s especiall y inner-cit y childre n les s tha n 4 year s ol d— ma y b e vulnerabl e t o acut e encephalopath y a t bloo d lea dlevel s o f

8 0 t o 100 /ig/dl . Fro mth e precedin g discussion , i t ca n b e see n tha t severit y o f

symptom s varie s widel y fo r differen t adult s o r childre n a s afunctio n o f increasin g bloo d lea dlevels . Som e sho w irreversibl e CN S damag e o r deat ha t level s les s tha n 10 0 /ig/dl , wherea s other s may no t sho w an y o f

th e usua l clinica l sign s o f lea d intoxicatio n eve n at

bloo dlea dlevel s in th e 100 t o 20 0 /ig/d l range . Thi s differenc e ma y b e cause d(1 ) b y individua l biologica l variatio n i n susceptibilit y t o lea deffects ; (2 ) b y change s in bloo dlea dvalue s fro mth e tim e o f

initia l damagin g intoxication ; (3 ) b y bette r toleranc e fo r

agraduall y accumulatin g lea d burden ; o r

(4 ) b y an y numbe r

o f othe r interactin g factors , suc ha s nutritiona l stat e o r inaccurat e deter

mination s o f

bloo dlead . I n an y case , i n attemptin g t o estimat e exposur e level s fo r advers e healt heffect s o f lead , th e rang e o f

exposur e level s yieldin g damag

in g effect s t o th e mos t

susceptibl e individual s need s t o b e emphasize drathe r tha n an y averag e leve l at whic hsuc heffect s ar e seen . Fo r adults , i t

woul dap pea r tha t th e mos t susceptibl e individual s d o no t ex hibi t acut e encephalopath y symptom s unti l bloo d lea dlevel s o f

100 /ig/d l ar e reache dor , mor e typically , ar e substantiall y exceeded . I n regar dt o children , th e majorit y o f case s showin g acut e en cephalopathi c symptom s hav e bloo dlea dlevel s o f 100 /ig/d l o r

more . Fo r

aver y few cases , level s a s lo w a s 8 0 /ig/d l hav e bee n reported . 11.5.1. 2 EFFECT S O FLOW-LEVE LLEA D EX

POSURE S Als o o f grea t relevanc e fo r

establishin g safety limit s fo r exposur e t o lea di s th e questio n o f whethe r exposure s lowe r

tha n thos e producin g symptom s o f over t acut e intoxicatio n ma y exer t mor e subtle , subclinica l neurobehaviora l effect s in apparentl y asymptomati c adult s o r

children . Attentio n ha s bee n focuse di n particula r

o n whethe r

exposure s leadin g t o bloo dlea dlevel s in th e 3 0 o r 4 0 t o 8 0 /ig/d l rang e ma y lea dt o neurobehaviora l deficit s in th e absenc e o f an y classica l sign s o f

lea dencephalopathy . Th e literatur e o n thi s subjec t i s somewha t

limite dan d controversia l bu t

stil l allow s fo r

certai n statement s t o b e mad e abou t

th e possibl e hazar do f lo w t o moderat e lea dexposur e levels . If suc hneurobehaviora l deficit s occurre di n adult s wit hgrea t

frequency , on e migh t

expec t thi s t o b e reflecte db y highe r

rate s o f absence s o r

report s o f neurologicall y relate dsymptom s amon g occupa tionall y expose dlea dworkers . Som e recen t epidemiologica l studie s hav e investigate dpossibl e relationship s betwee n moderatel y elevate dbloo d lea dlevel s an dgenera l healt ha s indexe db y record s o f sic k absence s tha t

hav e bee n certifie db y physi

cians . N o correlatio n betwee n elevate dbloo dlea d level s an dsicknes s rate s o r type s o f symptom s re porte dwer e found 21 2 fo r group s o f

worker s in alea d storag e batter y factor y fro mhigh- , medium- , an d low-exposur e area s versu s contro l worker s in nonex posur e area s o f

th e sam e plant . I t

shoul db e noted , however , tha t

mea n bloo dlea dlevel s fo r worker s in th e thre e exposur e group s wer e 60 , 50 , an d4 2 /ig/dl , respectively , compare dwit h4 5 /ig/d l fo r th e so calle dnonexposur e contro l group , renderin g th e conclusion s o f

th e repor t

o f dubiou s value . Simila r negativ e finding s wer e reporte db y Robinson 21 3 fo r tetraethyl-lea d(TEL ) worker s havin g mea n bloo d lea dvalue s o f

4 3 /ig/d l an ddail y urinar y excretio n o f 0.08 9 m g o f

lea dpe r lite r urin e ove r

a n 8

- t o 10

- yea r perio d( 3 t o 4 time s th e rat e fo r contro l group) . Dat ao n sicknes s rate s wer e base do n aretrospectiv e stud y o f record s ove r

a20-yea r

period . Absenc e o r sicknes s reports , however , ar e probabl y no t sensitiv e enoug hmeasure s t o detec t subtl e neurobehaviora l symptoms . Onl y afew studie s hav e employe dmor e sensitiv e psychometri c an dneurologica l testin g procedure s in an effort t o demonstrat e subclinica l lead-induce d neurobehaviora l effect s in adults . Fo r example , Morga n an dRepko 21 4 reporte dpreliminar y result s o f a n extensiv e stud y o f

behaviora l function s in 19 0 lead-expose dworker s (mea n bloo dlea dleve l = 60. 5 ± 17. 0 /ig/dl) . I n 6 8 percen t o f th e subjects , bloo dlea dwa s <8 0 /ig/dl . Th e majorit y ofth e sub

ject s wer e expose dbetwee n 5 an d2 0 years . Th e author s examine d3 6 nonindependen t measure s o f genera l performanc e an dobtaine d4 4 measure s o f sensory , psychomotor , an dpsychologica l functions . Initia l dat aanalysi s suggeste dtha t bloo dlea dlevel s correlate dwithsevera l reaction-tim e measures , an d 8-ALA D change s correlate dwit heffect s o n hand

ey e coordination . Thi s study , therefore , suggeste d tha t belo w abloo dlea dleve l o f 8 0 /ig/d l som e behaviora l change s di doccu r in adul t workers . I n addition , variabilit y o f performanc e increase dwit h increasin g bloo dlea dlevel ; however , onl y durin g perio do f high-deman dperformanc e di daworker' s capacit y clearl y decreas e a s aresul t o f lea dex posure . Unfortunately , aspect s o f th e Morga n an d Repk o wor k

ca n b e criticize dbecaus e o f methodologica l problems , includin g reporte dap 11-1 8P.6 3

paratu s failure s durin g testin g o f subjects . Also , finding s analogou s t o thos e reporte db y Morga n an d Repk o wer e no t

obtaine din asimila r

study 21 5 tha t foun dn o difference s betwee n contro l an dlead-ex

pose dworker s o n anumbe r o f psychometri c an d othe r performanc e tests . I n additio n t o th e abov e study 21 3 suggestin g possi

bl e CN S dysfunctions , numerou s investigation s hav e provide delectrophysiologica l dat aindicatin g tha t periphera l neuropath y symptom s ar e associate da t time s wit hbloo dlea dvalue s < 8 0 /ig/dl . A s reviewe db y Seppalainen, 21 6 reduction s in nerv e conductio n velocitie s an delectromyographi c deficit s hav e bee n observe di n patient s wit hknow n lea dpoisonin g bu t

withou t clinica l neurologica l symptoms. 21721 9 Mor e recently , suc hperiphera l nerv e deficit s wer e establishe db y Seppalainen 22 0 fo r lea dworker s whos e bloo dlea dlevel s wer e a s lo w a s 5 0 /ig/d l an dha dneve r exceede d7 0 /ig/d l durin g thei r entir e exposur e perio d(mea n = 4. 6 years) , a s determine db y regula r

monitoring . Simila r

result s wer e obtaine din astud y b y Melgaar de t al. 22 1 o n au tomobil e mechanic s expose dt o TE Lan dothe r lea d compound s in lubricatin g an dhigh-pressur e oils . Result s of amultielementa l analysi s ofth e worker' s bloo dfo r

lead , chromium , copper , nickel , an d manganes e indicate daclea r associatio n betwee n lea dexposur e an dperiphera l nerv e damage . Hal f o f th e worker s (1 0 o f

20 ) ha delevate dbloo dlea d level s (6 0 t o 12 0 /ig/dl ) an dshowe ddefinit e electromyographi c deficits . Mea n bloo dlea dleve l fo r th e contro l grou p wa s 18. 6 /ig/dl . Melgaar de t al. 22 1 reporte dadditiona l result s o n associatin g lea d exposure s wit hpolyneuropath y o f unknow n etiolog y i n 1 0 case s fro mth e genera l population . Anothe r stud y reporte drecentl y b y Arak i e t al. 22 2 provide s furthe r confirmatio n o f

th e Seppalainen 22 0 an d Melgaar de t

al. 22 1 findings i n tha t

evidenc e fo r

pe riphera l neuropath y effect s wer e reporte dfo r lead

industr y worker s wit hbloo dlea dvalue s o f 2 9 t o 7 0 /ig/dl . Th e ver y lo w bloo dlea dlevels , belo w 5 0 /ig/dl , reporte di n som e o f th e abov e studies , however , shoul dprobabl y b e viewe dwit hcautio n unti l furthe r

confirmator y dat aar e reporte do n sam ple s o f large r siz e usin g wel l verifie dbloo dassa y results . I n summary , th e abov e studies , whe n take n together , appea r

t o provid e reasonabl y stron g evi

denc e tha t

subclinica l periphera l neuropathie s occu r i n som e adult s havin g bloo dlea dlevel s i n th e 5 0 t o 7 0 /ig/d l range . Furthermore , althoug hi t coul db e argue dtha t

substantiall y highe r

lea dbod y burden s existin g befor e th e tim e o f som e o f th e studie s wer e actuall y responsibl e fo r producin g th e neuropathies , i t appear s tha t

i n a t leas t on e case 22 0 bloo dlevel s al

way s belo w 7 0 /ig/d l wer e sufficien t t o caus e periphera l nerv e dysfunctions . Tha t stud y b y Seppalainen 22 0 wa s als o generall y methodologicall y sound , havin g bee n wel l controlle dfo r th e possibl e effect s o f

extraneou s factor s suc ha s temperatur e difference s a t

th e nerv e conductio n velocit y assess men t sites . O n th e othe r

hand , it shoul db e note dtha t th e dat areporte dfo r

contro l subject s wer e obtaine d at a n earlie r

tim e (197 1 t o 1973 ) tha n dat afo r th e lea dexpose dsubject s (earl y 1973) ; an dn o bloo d lea dlevel s wer e reporte dfo r th e contro l subjects . Still , whe n th e Seppalainen 22 0 result s ar e viewe dcol

lectivel y wit hth e dat afro mothe r studie s reviewe d above , stron g evidenc e appear s t o exis t fo r periph

era l neuropathie s occurrin g in adult s a t bloo dlea d level s o f 5 0 t o 7 0 /ig/d l or , possibly , at eve n lowe r levels . I n additio n t o suspecte dneurobehaviora l effect s o f relativel y low-leve l lea dexposure s i n adults , ther e i s a n increasin g concer n tha t low-leve l ex posure s producin g bloo dlea dlevel s o f 4 0 t o 8 0 /xg/d l (o r

eve n less ) in childre n ma y induc e subtl e neurologica l damage , especiall y t o th e ver y youn g developin g CNS . Thi s issu e ha s attracte dmuc hat tentio n an dgenerate dconsiderabl e controvers y dur

in g th e pas t

decade . Th e evidenc e fo r an dagains t

th e occurrenc e o f

significan t

neurobehaviora l deficit s a t relativel y lo w level s o f

lea dexposur e is , a t

thi s time , quit e mixe dan dlargel y interpretabl e onl y afte r a thoroug hcritica l revie w o f th e methodologie s employe din eac hofth e variou s importan t studie s o n th e subject . On e o f th e majo r

approache s tha t

ha s bee n employe di s th e retrospectiv e analysi s o f lea dlevel s existin g in population s o f apparentl y asymptomati c childre n tha t

ar e the n divide dint o nonexpose dcon tro l an don e o r

mor e lead-expose dexperimenta l group s fo r

comparison s o f

thei r performanc e i n variou s neurologica l an dpsychometri c tests . A few studie s hav e bee n followe db y subsequen t furthe r reevaluatio n o f

th e sam e childre n b y th e sam e in

vestigator s in a n effort

t o asses s whethe r

indication s o f continuin g neurobehaviora l impairmen t stil l ex isted . Amon g th e majo r studie s tha t

hav e employe d thi s basi c approac han dtha t ar e widel y cite di n regar dt o thi s issue , thos e o f d e l aBurd e an d Choate, 22322 4 Perin o an dErnhart, 22 5 Alber t e t al., 22 6 an dLandriga n e t al. 22 7 sugges t

significan t effect s o f asymptomatic , low-leve l lea dexposure . I n contrast , th e studie s o f

Kotok, 22 8 Lansdow n e t al., 22 9 an dMcNei l e t

al. 23 0 repor t

generall y negativ e 11-1 9P.6 4

results . Tw o othe r

studies , on e b y Landriga n e t al. 23 1 an don e b y Koto k

e t al., 23 2 althoug hno t

reportin g clearl y statisticall y significan t difference s betwee n moderatel y lead-expose dan dcontro l subjects , nevertheles s repor t

certai n finding s tha t

ar e highl y suggestiv e o f

arelationshi p betwee n moderat e lea d exposur e an dcognitiv e impairment . Amon g th e severa l studie s presentin g evidenc e fo r CN S deficit s bein g associate dwithbloo dlevel s of les s tha n 8 0 figldl

ar e th e wor k

o f d e l aBurd e e t a l 223,22 4 an( - p e r i n o an dErnhart. 225 D e laBurd e e t al. 22 3 observe ddysfunction s ofth e CNS , fin e moto r dysfunction , impaire dconcep t formation , an d altere dbehaviora l profil e in 7 0 preschoo l childre n exhibitin g pic aan delevate dbloo dlea dlevel s (i n al l case s abov e 3 0 /ig/dl , mea n = 5 9 /ig/dl ) in com pariso n t o matche dcontro l subject s no t engagin g in pica . I n afollow-u p stud y o n th e sam e childre n (a t 7 t o 8 year s old) , d e l aBurde 22 4 reporte dfurthe r confirmatio n o f

continuin g CN S impairmen t a s assesse db y avariet y o f

psychologica l an dneurologi

ca l tests . Thi s wa s despit e th e fac t tha t man y o f th e bloo dlea dlevel s o f

th e lead-expose dchildre n ha d b y the n droppe dsignificantl y fro mth e initia l study . I n general , th e d e laBurd e e t al. 22322 4 studie s appea r t o b e methodologicall y sound , havin g man y feature s tha t strengthe n th e cas e fo r

th e validit y ofthei r

find

ings . Fo r example , ther e wer e appreciabl e number s o f childre n (6 7 lead-expose dan d7 0 controls ) whos e bloo dlea dvalue s wer e obtaine din preschoo l year s an dwh o wer e ol denoug h( 7 years ) durin g th e follow-u p stud y t o cooperat e adequatel y fo r reliabl e psychologica l testing . Th e specifi c psychometri c test s employe dwer e wel l standardize dan daccepte d a s sensitiv e indicator s o f minima l brai n damage , an d th e neurobehaviora l evaluation s wer e carrie dou t blind , tha t

is , withou t

th e evaluator s knowin g whic h wer e contro l o r

lead-expose dsubjects . Th e d e laBurde 223

- 22 4 studie s migh t b e criticize d o n severa l points , non e o f whic hi n th e fina l analysi s provid e sufficien t

ground s fo r

rejectin g thei r validity . On e difficult y i s tha t bloo dlea dvalue s wer e no t determine dfo r

contro l subject s in th e in

itia l study , bu t

th e lac k o f histor y o f

pica , a s wel l a s toot hlea danalyse s don e late r fo r th e follow-u p study , rende r

i t ver y improbabl e tha t

appreciabl e number s o f

lead-expose dsubject s migh t hav e bee n wrongl y assigne dt o th e contro l group . Also , result s indicatin g n o measurabl e coproporphyrin s i n th e urin e o f contro l subject s a t

th e tim e o f

initia l testin g furthe r hel p t o confir mprope r assignmen t

o f thos e childre n t o th e nonexpose dcontro l group . A secon d poin t o f criticis maddresse s th e probabl y inappropri

at e us e o f multipl e chi-squar e statistica l analyse s i n th e manne r

employe dt o analyz e th e result s o f th e study . Upo n recomputatio n ofth e statistica l signifi

canc e o f observe ddifferences , b y mean s ofth e mor e appropriat e Fisher' s exac t probabilit y tes t

an dac countin g fo r

th e numbe r

o f test s conducted , severa l measure s originall y reporte dt o b e statisticall y sig

nifican t stil l tur n ou t

t o b e significan t

a t p <0.0 5 o r lower . On e las t

proble mrelate s t o ambiguitie s in subjec t selectio n tha t

complicat e interpretatio n o f th e ful l meanin g ofth e result s obtained . Becaus e i t i s state dtha t

th e lead-expose dgrou p include d childre n wit hbloo dlea dlevel s o f 4 0 t o 10 0 /ig/dl , o r o f a t leas t 3 0 /ig/d l wit h"positiv e radiographi c finding s o f

lea dline s in th e lon g bones , metalli c deposit s in th e intestines , o r both, " th e reporte d deficit s migh t

b e readil y attribute dt o bloo dlea d level s a s lo w a s 3 0 /ig/dl . Othe r evidence, 10 1 however , suggest s tha t

suc hasimpl e interpretatio n ma y no t b e completel y accurate . Tha t is , th e wor k

o f Bett s etal. 10 1 indicate s tha t lea dline s ar e usuall y no t see n unles s bloo dlevel s excee d6 0 /ig/d l fo r mos t childre n a t

som e tim e durin g exposure , althoug h som e (approximatel y 2 5 percent ) ma y sho w lea d line s a t bloo dlea dlevel s o f

4 0 t o 6 0 /ig/dl . Vir

tuall y non e hav e lea dline s a t level s belo w 4 0 /ig/dl . I n vie w o f

this , th e d e l aBurd e result s probabl y ca n b e mos t reasonabl y interprete da s demonstratin g lastin g neurobehaviora l deficit s a t bloo dlea dlevel s in exces s o f

5 0 t o 6 0 /ig/dl . Simila r conclusion s ar e als o warrante do n th e basi s o f result s o f

th e Perin o an dErnhar t study, 22 5 whic hdemonstrate darelationshi p betwee n neurobehaviora l deficit s an dbloo dlea dlevel s rang in g fro m4 0 t o 7 0 /ig/d l in agrou p o f 8 0 inner-cit y preschoo l blac k

children . On e o f

th e mor e interest

in g aspect s ofth e findings , i s tha t th e norma l correla

tio n o f .5 0 betwee n parent' s intelligenc e an dtha t o f thei r offsprin g wa s foun dt o b e reduce dt o onl y . 1 0 in th e lead-expose dgroup , presumabl y becaus e o f th e influenc e o f

anothe r facto r (lead ) tha t

interfere d withth e norma l intellectua l developmen t o f th e lead-expose dchildren . Man y ofth e methodologica l virtue s o f

th e d e l aBurd e studies 22322 4 wer e als o presen t i n th e Perin o an dErnhart 22 5 work , an d bloo dlea ddetermination s an dstatistica l analyse s appeare dsound . Abou t th e onl y alternativ e ex planatio n fo r

thes e result s migh t

b e difference s i n th e educationa l background s o f th e parent s o f

th e con tro l subject s whe n compare dwit hlead-expose dsub

jects , becaus e parenta l educatio n leve l wa s foun dt o b e significantl y negativel y relate dt o th e bloo dlea d level s o f th e childre n participatin g i n thi s study . 11-2 0Parent s o f childre n i n th e lead-expose dgrou p ha d significantl y poore r

educationa l background s tha n th e contro l grou p parents . Th e importanc e o f thi s poin t lie s in th e fac t

tha t severa l othe r

studies 23323 5 hav e demonstrate dtha t th e highe r

th e parenta l educatio n level , th e mor e rapi dth e developmen t an dth e highe r

th e intelligenc e quotient s (I.Q.'s ) o f thei r children . I t

i s nevertheles s interestin g tha t th e d e l aBurd e studie s an dth e Perin o an dErnhar t wor k poin t t o essentiall y th e sam e conclusion , i.e. , tha t neurobehaviora l deficit s occu r at bloo dlea dlevel s possibl y a s lo w a s 4 0 /ig/dl . Also , i n bot hcases , th e childre n studie dwer e fro minner-city , low-incom e areas . Tw o othe r

studie s withpositiv e finding s had , fo r th e mos t part , som e seriou s methodologica l limita

tions . Alber t

e t al. 22 6 foun dtha t

asymptomati c childre n ( 5 t o 1 5 year s old ) whos e bloo dlea dlevel s at a n earlie r

ag e wer e elevate d( > 6 0 /ig/dl ) late r ha dsignificantl y mor e menta l disorder s an dpoore r schoo l performanc e tha n acontro l grou p wit hlowe r lea dlevel s i n bot hbloo dan ddeciduou s teeth . Un

fortunately , however , n o assa y ofth e lea dburden , in eithe r bloo do r

teeth , wa s don e fo r

abou t one-hal f o f th e childre n i n th e contro l group ; an dn o significan t effect s wer e reporte dfo r childre n wit hlea dlevel s < 6 0 /ig/dl . Also , anothe r majo r criticis mi s tha t

som e childre n i n th e contro l grou p ha drelativel y hig h bloo dlea dlevel s ( > 4 0 /ig/dl) . I n anothe r study , Landriga n e t

al. 22 7 foun dtha t

asymptomatic , lead

expose dchildre n livin g nea r asmelte r

score dsignifi

cantl y lowe r

tha n matche dcontrol s o n measure s o f performanc e I.Q . an dfinger-wris t tapping . Th e con tro l childre n i n thi s stud y were , however , no t wel l matche db y ag e o r

se x t o th e lead-expose dgroup , althoug hi t

shoul db e pointe dou t tha t result s re maine dstatisticall y significan t eve n afte r

appropri

at e adjustment s wer e mad e fo r ag e differences . I n anothe r

relevan t study , presente di n adoctora l dissertatio n b y Rummo, 2 1 1 significan t neurobehaviora l deficit s wer e foun d(hyperactivity , lowe r score s o n McCarth y scale s o f cognitiv e func

tion , etc. ) fo r

childre n wh o ha dpreviousl y ex perience dhig hlevel s o f lea dexposur e tha t

ha dpro duce dacut e lea dencephalopathy . Mea n maximu m bloo dlea dlevel s for

thos e childre n a t

th e tim e o f

en cephalopath y wer e 8 8 ± S.D . 4 0 /ig/dl . Childre n wit hmoderat e degree s o f bloo dlea delevation , however , wer e no t

significantl y differen t

fro mcon trol s o n an y measur e o f cognitiv e functioning , psy chomoto r

performance , o r

hyperactivity . O n th e othe r hand , if

th e dat afo r

performanc e o n th e McCarth y Genera l Cognitiv e Inde x o r severa l McCarth y Subscale s ar e plotte dgraphically , a s i n

Figure s 11- 2 an d11-3 , the n arathe r interestin g relationshi p betwee n tes t performanc e an dlevel s ari dduratio n o f

lea dexposur e become s apparent . 9 5

9 0

8 5

8 0

7 5 1 1



# ki 1 1

V - \ - \ - * — 1 1 CONTROL S SHORT-TER M LONG-TER M ENCEPHALOPATH Y DEGRE E O F LEA D EXPOSUR E Figur e 11-2 . McCarth y Genera l Cognitiv e Index score s a s a functio n o

f degre e o

f lea d exposure. 21 1 

### T T

MOTO R PERCEPTUA L VERBA L MEMOR Y QUANTITATIV E

CONTROL S SHORT-TER M LONG-TER M ENCEPHALOPATH Y DEGRE E O F LEA D EXPOSUR E Figur e 11-3 . Score s o n McCarth y Subscale s a s a functio n o f degre e o

f lea d exposure. 21 1 Althoug hth e score s fo r short-ter mmoderate-ex

posur e subject s ar e essentiall y th e sam e a s contro l values , a n interestin g aspec t i s tha t th e score s fo r long-ter mmoderate-exposur e subject s consistentl y fal l belo w thos e fo r

contro l subject s an dli e betwee n th e latte r

an dth e encephalopath y grou p scores . Thus , i t woul dappea r

tha t long-ter mmoderat e lea d exposur e may , i n fact , exer t subtl e neurobehaviora l effects . Thi s migh t

b e show n t o b e statisticall y sig

nifican t b y mean s o f

othe r type s o f

analyse s o r

if large r sample s wer e assessed . I t shoul db e note dtha t (1 ) th e maximu mbloo dlea dlevel s fo r th e short

ter man dlong-ter mexposur e subject s wer e al l >4 0 11-2 1P.6 6

/ig/d l (mean s = 6 1 ± S.D . 7 an d6 8 ± S.D . 1 3 /ig/dl , respectively) , wherea s contro l subject s al l ha dbloo dlea dlevel s belo w 4 0 /ig/d l (mea n = 2 3 ± S.D . 8 /ig/dl) ; an d(2 ) th e contro l an dlead-expose d subject s wer e inner-cit y (Providence , Rhod e Island ) childre n wel l matche dfo r socioeconomi c back

ground , parenta l educatio n levels , incidenc e o f pica , an dothe r

pertinen t

factors . A somewha t

simila r patter n o f

result s emerge d fro mamor e recen t

stud y b y Koto k

e t al. 23 2 i n whic h 3 6 Rochester , Ne w York , contro l grou p childre n withbloo dlea dlevel s < 4 0 /ig/d l wer e compare d with3 1 asymptomati c childre n havin g distinctl y ele

vate dbloo dlea dlevel s (6 1 t o 20 0 /ig/dl) . Bot h group s wer e wel l matche do n importan t backgroun d factors , including , notably , thei r propensit y t o ex hibi t pica . Again , n o clearl y statisticall y significan t (p <.05 ) difference s betwee n th e tw o group s wer e foun do n anumbe r

o f differen t test s o f cognitiv e an d sensor y functions . A s indicated , however , b y tes t result s fro mth e Koto k e t al . study 23 2 presente di n Tabl e 11-3 , th e mea n score s ofth e control-grou p childre n wer e con sistentl y highe r

tha n thos e ofth e lead-expose dgrou p fo r al l si x o f

th e abilit y classe s listed . Also , i n on e cas e th e leve l o f

significanc e achieve dborderlin e significanc e (.1 0 >p >.05) , apatter n o f result s tha t hint s at atren dexistin g towar dlowe r abilit y level s fo r th e lea dgroup . Th e author s cautiousl y state d tha t "th e dat ad o no t

prov e tha t

thes e childre n hav e sustaine dn o neurologi c damag e b y lead " an dtha t "late r longitudina l testin g ma y demonstrat e cogni

tiv e o r educationa l deficiencies. " The y als o indi

cate dtha t

"evaluatio n o f

behavior , neurologic , o r moto r functionin g wa s no t

carrie dout " an dnote d tha t "subtl e cognitiv e an dfine moto r change s wer e demonstrate di n a n extensiv e an dcarefull y con trolle devaluatio n o f

asymptomati c childre n resid

in g i n th e vicinit y o f

a n E l Pas o lea dsmelter." 22 7 The y g o o n t o impl y tha t th e earlie r

exposur e t o lea d i n infanc y o f

th e E l Pas o childre n an dthei r longe r perio do f

exposur e (mea n = 6. 6 year s versu s < 3 year s fo r th e Rocheste r

group ) migh t

accoun t fo r th e disparit y i n result s .betwee n th e tw o studies . Thei r results , o n th e othe r

hand , plu s th e patter n see n in th e Rummo 2 " study , ca n b e construe da s evidenc e consisten t

wit hth e finding s o f th e d e laBurd e studies 22322 4 an dother s reviewe dabov e tha t repor t result s linkin g lo w t o moderat e level s o f lea dex posur e t o significan t

behaviora l impairments . Othe r studie s hav e produce dmixe do r negativ e result s i n attempt s t o determin e whethe r arelation

shi p exist s betwee n lea dexposur e an dCN S deficit s TABL E 11-3 . COMPARISO N O F TES TRESULT S I N LEA D AN D CONTRO L GROUPS 23 2 Abilit yclas s Socia l maturit y Spatia l Spoke n vocabular y Information comprehensio n Visua l attentio n Auditor ymemory Grou p

Lea d Contro l Lea d Contro l Lea d Contro l Lea d Contro l Lea d Contro l Lea d Contro l Mea n I.Q . ±S.D .

123. 5 ±22. 7 126. 3 ±17. 7 92. 0 ±18. 0 100. 8 ±18. 7 91. 7 ±13. 9 92. 9 ±13. 7 94. 5 ±14. 9 96. 3 ±16. 6 89. 7 ±18. 3 93. 3 ±23. 0 93. 0 ±24. 0 99. 9 + 32. 0 Significanc e p>.1 0 .1 0 >p >.0 5 p>.1 0 p>.1 0 p>.1 0 p >.1 0 usin g variou s standardize dpsychometri c techniques , neurologi c examinations , an drating s b y teachers , parents , o r

experimenters . Fo r

example , Kotok 22 8 reporte dearlie r

tha t developmenta l deficiencie s (usin g th e Denve r

Developmen t

Screenin g test , whic hi s asomewha t

insensitiv e measur e o f

develop

ment ) i n agrou p o f

asymptomati c childre n havin g elevate dlea dlevel s (5 8 t o 13 7 /ig/dl ) wer e identica l t o thos e in acontro l grou p simila r in age , sex , race , environment , neonata l condition , an dpresenc e o f pica , bu t whos e bloo dlea dlevel s wer e lowe r (2 0 t o 5 5 figldl). Th e deficiencie s coul db e correlate dwith inadequacie s i n th e children' s environment . Childre n in th e lead-expose dgroup , however , ha d bloo dlea dlevel s a s hig ha s 13 7 /ig/dl , wherea s som e o f th e control s ha dbloo dlea dlevel s a s hig ha s 5 5 /ig/dl . Thus , th e stud y wa s in effec t acompariso n o f tw o group s wit hdifferen t degree s o f

elevatio n i n lea dexposur e rathe r

tha n on e o f

lead-expose dver su s nonexpose dcontro l children . I n severa l studie s o f

childre n livin g in th e vicinit y o f smelter s o r

factories , significan t

neurobehaviora l effect s hav e typicall y no t bee n foun dat

moderat e elevation s o f

bloo dlea dlevels . Fo r example , Lansdow n e t

al. 22 9 foun darelationshi p betwee n bloo dlea dleve l in childre n an dth e distanc e the y live dfro mlead-processin g facilities , bu t n o rela

tionshi p betwee n bloo dlea dleve l an dmenta l func

tionin g wa s found . Onl y aminorit y o f th e lead-ex

pose dsampl e ha dbloo dlea dlevel s ove r 4 0 /ig/dl , however , on e woul dno t expec t astrikin g relation

shi p betwee n menta l functionin g an dlea dlevel s be

lo w suc halevel . I n a n extensive , generall y thoroug hstudy , McNei l e t al. 23 0 foun dtha t

asampl e o f

childre n livin g nea r

a lea dsmelte r

i n E l Pas o wa s comparable,medicall y 11-2 2an dpsychologicall y t o matche dcontrol s livin g

elsewher e i n th e sam e cit y othe r tha n i n th e direc t effect s o f

lea d(bloo dlea dlevel , fre e erythrocyt e protoporphyri n levels , an dX-ra y findings) . Lead

expose dchildre n i n th e grou p livin g nea r th e smelte r did , however , hav e significantl y differen t per sonalit y tes t

results , whic hwer e ascribe db y th e author s a s bein g du e t o recen t upheava l in th e live s o f th e lead-expose dchildre n wh o ha dbee n recentl y force dt o mov e fro mth e vicinit y ofth e smelter . Con

siderabl e communit y unres t existe dat

th e tim e o f bot hth e McNei l e t

al . study 23 0 an dth e wor k o f Landriga n e t

al. 22 7 o n th e E l Pas o smelte r are a population , whic hgre w ou t o f circumstance s associ

ate dwit hth e discover y o f th e lea dexposure s an d dispositio n o f

lega l matter s surroundin g them . Th e impac t o f th e extraneou s unres t

o n bot hstudie s ha s tende dt o clou dinterpretatio n o f th e tru e meanin g o f thei r respectiv e result s whic hi n tur n hav e becom e quit e controversial . Se e Appendi x Efo r mor e infor

mation . Th e personalit y tes t result s ofth e McNei l e t al. 23 0 stud y coul dnevertheles s hav e bee n cause db y th e effect s o f

lea do n th e expose dgroup . Also , it shoul db e note dtha t

afew suggestiv e trend s towar d statistica l significanc e fo r certai n interaction s be

twee n lea dan dag e o f subject s ( p <.10 ) wer e re porte dfo r

som e o f

th e cognitive-functio n tes t measures . Base do n th e abov e results , th e author s o f th e Lansdow n e t

al. 22 9 an dth e McNeil 23 0 paper s con clude dtha t

n o evidenc e wa s foun dfo r th e occur renc e o f neurobehaviora l effect s at subclinica l lea d exposur e level s i n thei r

studies . Perhap s tha t

conclu

sio n coul db e generalize dt o sugges t tha t n o signifi

can t CN S deficit s typicall y occu r a s aresul t

o f subclinical , lo w t o moderat e lea dexposure s o f childre n livin g i n th e vicinit y o f smelter s o r

othe r lead-processin g facilities . T o th e exten t tha t thos e childre n ma y diffe r

in significan t

way s fro mth e inner-cit y childre n show n b y d e l aBurde, 223

- 22 4 Perin o an dErnhart, 22 5 an dAlbert 22 6 t o hav e neurobehaviora l impairment s a t bloo dlea dlevel s a s lo w a s 4 0 t o 5 0 figldl, ambiguou s result s fro mth e smelte r childre n ar e no t

necessaril y contradictor y t o th e bette r

establishe dfinding s o f significan t

CN S effect s fo r

inner-cit y children . Furthermore , it shoul db e note dtha t

report s o f

periphera l neuropa thie s fo r bot hpopulation s o f

childre n a t

lo w t o moderat e lea dexposur e levels , a s described , ma y in

dicat e tha t

bot hgroup s ar e at

significan t

ris k fo r a t leas t tha t typ e o f neura l tissu e damage . A n additiona l approach , differen t fro mth e basi c strateg y employe di n th e abov e studies , ha s bee n utilize di n othe r studie s in a n effort

t o demonstrat e tha t lo w o r moderat e bloo dlea dlevel s caus e signifi

can t neurobehaviora l deficits . Thi s approac hcon sist s o f identifyin g population s o f childre n wit hdiag

nose dneurobehaviora l deficit s o f unknow n etiolog y an dassayin g bloo dlea do r makin g othe r

assessment s in orde r t o lin k pas t lea dexposure s t o th e children' s presen t neurobehaviora l impairments . Thus , fo r ex ample , effort s hav e bee n mad e t o implicat e moder

at e o r lo w leve l lea dexposure s a s acausativ e facto r in a t leas t som e case s o f

hyperactivit y o f

unknow n etiology . Th e possibilit y tha t suc hlow-leve l lea dex posure s induc e hyperactivit y ha s gaine dcredenc e throug hth e wel l documented 8720 3 fac t tha t hyperac

tivit y i s on e o f

th e frequen t

neurobehaviora l se quela e observe din childre n wh o surviv e episode s o f acut e encephalopath y resultin g fro mhigh-leve l lea d exposures . Th e evidenc e fo r an dagains t

th e hy

pothesi s tha t

low-leve l lea dexposure s produc e hy

peractivit y ha s bee n accumulatin g at arapi drat e durin g th e pas t

few year s an dha s generate dcon siderabl e controvers y o n th e subject . Onl y afew o f th e mor e salien t

finding s ar e viewe dbelo w an di n th e sectio n o n anima l studie s (Sectio n 11.5.2) . I n acase-contro l study , Davi de t al. 23 6 compare d th e incidenc e o f

elevate dbloo dlea dlevel s i n fiv e group s o f

children : (1 ) apur e hyperactiv e grou p withn o apparen t

caus e fo r

hyperactivity ; (2 ) agrou p o f hyperactiv e childre n withahighl y probabl e caus e o f hyperactivity , e.g. , prematurity ; (3 ) agrou p o f hy

peractiv e childre n wit hapossibl e cause ; (4 ) agrou p o f childre n wh o ha drecovere dfro mlea dpoisoning ; an d(5 ) anonhyperactiv e contro l group . Pur e hy

peractiv e childre n ha dstatisticall y significantl y highe r bloo dlea dlevel s (mea n = 26. 2 ± 8 figldl) tha n control s (mea n = 22. 2 ± 9. 6 /ig/dl) , wherea s childre n wit hahighl y probabl e caus e di dno t (mea n = 22. 9 ± 6. 6 /ig/dl) . Similarly , th e pur e hyperactiv e childre n tende dt o excret e mor e lea dtha n control s o r probabl e caus e hyperactive s whe n give n asingl e d©s e o f penicillamine . Althoug hth e causa l relation

shi p betwee n lea dexposur e an dhyperactivit y canno t b e sai dt o b e prove db y thi s study , th e dat ao f Davi d e t al., 23 6 whe n place dwit hfinding s o f hyperactivit y in childre n know n t o hav e recovere dfro mlea d poisonin g an dnumerou s anima l studie s demonstrat

in g alteration s in moto r activit y followin g lea dad

ministrations , migh t

b e interprete da s supportin g th e hypothesi s tha t

arelationshi p betwee n moderat e lea dexposur e an daltere dmoto r activit y exists . O n th e othe r

hand , severa l othe r

point s argu e agains t acceptanc e o f

suc hathesi s at

thi s time . Fo r on e thing , th e Davi de t al. 23 6 stud y itsel f

an dth e 11-2 3P.6 8

author' s conclusion 6 ca n b e questione do n severa l bases . I n tha t

study , fo r

example , th e closenes s ofth e matc ho f subject s in th e fiv e group s oi j variable s othe r tha n ag e an dse x i s no t clearl y specifie db y th e authors . Also , th e interpretatio n o f difference s in bloo dlea dlevel s in th e 7-to-8-year-ol dchildre n i s fraugh t withnumerou s problems , no t #i e leas t

o f whic hi s th e fac t

tha t suc hlevel s ar e probabl y no t ver y accurat e indice s o f long-pas t

lea dexposure s tha t presumabl y occurre ddurin g presclhoo l years . Man y factor s i n th e interi mbetwee n presume dlea d exposur e an dassay fo r

lea dcoul daffec t

th e results , includin g possibl e differentiall y highe r incidence s o f pic ai n th e hyperactiv e childre n tha n in contro l sub

jects . Klei n e t

al. 23 7 hav e note dtha t

pic ama y b e par t o f certai n behaviora l syndrome s tha t exis t eve n in th e absenc e o f

lea dexposure , bu t

tha t woul dpre dispos e th e affecte dchil dtowar dmor e lea dinges

tio n b y virtu e ofth e habit' s presence . Indteed , ther e i s evidenc e tha t

amon g mentall y subnorma l childre n whos e menta l deficienc y ca n b e definitel y attribute d t o etiologie s othe r

tha n lea dpoisonin g tha t ther e i s bot hahig hincidenc e o f pic aan dmodteratel y ele

vate dbloo dlead. 23 8 Last , it shoul db e note dtha t

a numbe r o f othe r investigators, 2 ".227,229.230,23 9 wn o expressl y looke dfo r

evidenc e o f

lead-induce dhy

peractivit y a s par t

o f thei r screenin g fo r neurobehaviora l deficit s associate dwithbloo dlea d level s a s lo w a s 4 0 figldl, faile dt o fin dan y signifi

can t effect s tha t

suppor t th e thesi s tha t

low-leve l lea dexposure s induc e hyperactivity . Thus , eve n thoug hth e hypothesi s i s intriguin g an dcertainl y worth y o f

furthe r investigation , it

canno t b e state dat thi s tim e tha t

sufficien t

evidenc e exist s t o establis h hyperactivit y a s aneurobehaviora l defici t clearl y as sociate dwit hlo w o r

moderat e lea dexposures . I n additio n t o th e abov e dat abearin g o n possibl e link s betwee n subclinica l lea dexposure s an dth e in

ductio n o f

hyperactivity , certai n recentl y reporte d data 2 4 0 provid e evidenc e implicatin g increase d heav y meta l absorption , includin g lea duptake , i n th e etiolog y o f

learnin g disabilities . Mor e specifically , childre n identifie dfo r othe r classifica

tio n purpose s a s havin g learnin g disabilitie s wer e foun dt o hav e significantl y elevate dlevel s o f lead , a s wel l a s cadmiu man dsom e othe r metals, , in thei r

hai r whe n compare dwithcontro l childre n no t classe da s learnin g disabled . I n fact , adiscrimin»an t functio n analysi s yielde d9 8 percen t accurac y i

mclassifyin g childre n a s norma l o r

learnin g disable dbase do n a combine dfacto r

o f cadmium , cobalt , manganese , chromium , an dlithiu mlevels . Lea dwa s no t in

clude di n thi s five-meta l discriminan t function , sinc e it s predictiv e valu e wa s wel l serve db y cobal t an d cadmiu mbecaus e o f

asignifican t

negativ e correla

tio n betwee n lea dan dcobal t ( r = .67; p <.01 ) an da significan t

positiv e correlatio n betwee n lea dan d cadmiu m( r

= + .53 ; p <.01) . Unfortunatel y fo r presen t purposes , n o bloo dlea dlevel s o r possibl e pas t exposur e historie s wer e provide dfo r th e childre n i n th e abov e study. 24 0 Othe r recen t studie s analogou s in basi c approac h t o tha t employe db y Davi de t al. 23 6 an dPih l an d Parkes 24 0 hav e provide dintriguin g ne w informatio n tendin g t o lin k

prenata l lea dexposure s t o th e late r developmen t

o f menta l retardation . Fo r example , Beatti e e t

al. 24 1 identifie d7 7 retarde dchildre n an d 7 7 norma l childre n matche do n age , sex , an d geography . Th e residenc e durin g th e gestatio n ofth e subjec t wa s identified , an dafirst-flus hmornin g sampl e oft?;* * wate r

wa s obtaine dfro mth e residence . O f 6 4 matche dpairs , n o norma l childre n wer e foun d t o com e fro mhome s serve dwithwate r containin g hig hlea dlevel s (>80 0 /ig/liter) , wherea s 1 1 o f th e 6 4 retarde dchildre n cam e fro mhome s serve dwit h wate r containin g hig hlea dlevels . Th e author s con clud e tha t

pregnanc y in ahom e withhig hlea din th e wate r suppl y increase s b y afacto r o f 1. 7 th e ris k

o f bearin g aretarde dchild . I n afollow-u p t o th e Beatti e study , Moor e e t al. 24 2 obtaine dlea dvalue s fro mbloo dsample s draw n durin g th e secon dwee k o f lif e an dstore do n filte r paper . Thes e sample s ha dbee n obtaine da s par t o f a routin e phenylketonuri ascreenin g stud y an dwer e kep t o n file. Bloo dsample s wer e availabl e fo r 4 1 of th e retarde dan d3 6 o f th e norma l childre n in th e origina l stud y b y Beattie . Bloo dlea dconcentration s in th e retarde dchildre n wer e significantl y highe r tha n value s measure din . norma l children . Mea n bloo dlea dfo r

retardate s wa s 1.2 3 ± 0.4 3 /iMol/lite r

(25. 5 ± 8. 9 /ig/dl ) an dfo r normal s wa s 1. 0 ± 0.3 8 /iMol/lite r (20. 9 ± 7. 9 figldl). Th e difterenc e in lea dconcentration s wer e significan t (p = 0.0189 ) b y th e Mann-Whitne y test . Thes e tw o studie s sugges t tha t lea dexposur e t o th e fetu s durin g th e critica l perio do f brai n developmen t ma y caus e perturbation s in brai n organizatio n tha t ar e expresse dlate r

i n menta l retardatio n syndromes , an dthe y rais e fo r

carefu l scrutin y th e risk s o f in

trauterin e exposur e t o lead . Insufficien t informatio n exists , however , t o allo w estimatio n ofth e level s o f lea dexposur e o f

pregnan t

wome n tha t

migh t caus e thos e prenata l effect s in th e fetu s tha t ma y resul t

i n late r neurobehaviora l impairments . On e las t advers e effec t

o f lea do n neura l functio n in childre n remain s t o b e considered , an dtha t i s th e 11-2 4possibl e inductio n o f periphera l neuropathie s b y low-to-moderat e lea dexposures . I t i s generall y ac cepte dtha t

lead-induce dperiphera l neuropathies , althoug hfrequentl y see n in adult s afte r prolonge d exposures , ar e extremel y rar e i n children . Severa l articles 243 " 24 5 in th e literature , however , d o describ e cas e historie s tha t

confir mth e occurrenc e o f lead-in

duce dperiphera l neuropathies , a s indexe db y electromyography , assessment s o f nerv e conductio n velocity , an dobservation s o f othe r over t neurologi

ca l signs , suc ha s tremor , wris t an dfoot

drop , etc . Som e o f thes e fran k

neuropathi c effect s hav e bee n observe dfo r

severa l case s at

bloo dlea dlevel s o f

6 0 t o 8 0 /ig/dl, 24 5 an di n othe r case s periphera l neuropath y wa s associate dwithbloo dlea dvalue s o f 3 0 /ig/dl ; however , in th e latte r cases , lea dline s in lon g bone s sugges t

probabl e pas t

exposure s leadin g t o prio r bloo dlea dlevel s a t

leas t a s hig ha s 4 0 t o 6 0 /ig/d l an dprobabl y i n exces s o f 6 0 /ig/d l (base do n th e dat ao f

Bett s e t al. 101 ) . I n eac hofth e presen t cas e studies , ther e wa s reporte dsome , i f no t complete , recover y o f

affecte dmoto r

function s afte r

treatmen t fo r lea dpoisoning . Further , i t shoul db e note dtha t

a tentativ e associatio n ha s bee n hypothesize dbetwee n th e existenc e o f

sickl e cel l diseas e an dincrease dris k o f periphera l neuropath y a s aconsequenc e o f child

hoo dlea dexposure . Mos t o f th e case s reporte din

volve dinner-cit y blac k children , severa l withsickl e cel l trait . I n summary , it appear s tha t

(1 ) evidenc e fo r fran k periphera l neuropath y i n childre n cer tainl y exists ; (2 ) suc hneuropath y ca n b e associate d rathe r wel l wit hbloo dlea dlevel s a t leas t a s lo w a s 6 0 /ig/dl ; an d(3 ) evidenc e suggest s tha t inner-cit y childre n withsickl e cel l diseas e may b e at specia l risk . Furthe r evidenc e fo r

lead-induce dperiphera l neuropathie s in childre n i s provide db y th e dat ao f Landriga n e t

al. 23 1 derive dfro mastud y o f childre n livin g in clos e proximit y t o asmelte r in Idaho . Th e nerv e conductio n velocit y result s fro mthi s stud y ar e presente din Figur e 1 1 - 4 in th e formo f ascatte r diagra mrelatin g peronea l nerv e conductio n velocitie s (NCV ) t o bloo dlea dlevel s in th e childre n studied . N o clearl y pathologi c conductio n velocitie s wer e observed , althoug hastatisticall y significan t negativ e correlatio n wa s foun dbetwee n peronea l NC V an dbloo dlea dlevel s ( r = 0.38 , p <.0 2 b y one-taile dt

test) . Thes e results , therefore , provid e evidenc e fo r

significan t

slowin g o f

nerv e conductio n velocit y and , presumably , advancin g periphera l neuropath y a s afunctio n o f increase dbloo dlea d levels . Th e dat ad o no t

allo w fo r

clea r statement s t o b e mad e regardin g an y threshol dfo r apathologi c slowin g o f

NCV .

> 62.0 0 z O o 56.8 0 -

° 51.6 0 - lll l

YICONDUCTIO N VELOCITY I =

_I r • = •0.38 1 I n = 202 )

—• • •

—• •• _•••• •• ••V I

—•. # • am a •• «••..• ••"# •• •• 

### —*!%*&*+

: • mzTr

9 —*"y ! -»-jL •

••a

a a a • . •* ••

. •• 1 1 1 * 1 lll l 54. 8 - .04 5 x (BLOO D LEAD )

• ** . • ••

1 1 1 1 "

-

—

0 1 5 3 0 4 5 6 0 75 9 0 105 12 0 13 5 15 0 BLOO D LEAD , <rg/d l Figur e 11-4 . Peronea l nerv e conductio n velocit y versu s bloo d lea d level , Idaho , 1974.23 1 11.5.1. 3 SUMMAR Y AN D CONCLUSION S FO R HUMA N STUDIE S Rathe r tha n simpl y recapitulatin g in briefe r form th e finding s reviewe dabove , a n attemp t will b e mad e her e t o integrat e informatio n derive dfro mth e revie w an dt o focu s o n certai n ke y issue s concernin g th e impac t

o f lea do n huma n neurobehaviora l func

tions . Amon g th e ke y point s t o b e addresse dare : (1 ) th e interna l exposur e levels , a s indexe db y bloo d lea dlevels , a t

whic hvariou s advers e neurobehaviora l effect s occur ; (2 ) th e reversibilit y o f suc hdeleteriou s effects ; an d(3 ) th e population(s ) tha t appea r t o b e mos t

susceptibl e t o neura l damage . Regardin g th e first

issue , it woul dappea r

fro m dat areviewe dabov e tha t surprisingl y lo w level s o f bloo dlea dcan , a t

times , b e associate dwit hth e mos t extrem e effect s o f

lea dpoisoning , includin g severe , irreversibl e brai n damag e a s indexe db y th e occur renc e o f acut e o r chroni c encephalopath y symptom s o r deat ho r both . Fo r

mos t adults , suc hdamag e doe s no t occu r unti l bloo dlea dlevel s wel l i n exces s o f 12 0 /xg/d l ar e reached . Evidenc e doe s exist , however , fo r

th e occurrenc e o f

acut e encephalopa

thy an ddeat hin som e adult s at bloo dlea dlevel s somewha t

belo w 12 0 figldl. Fo r

children , th e effec

tiv e bloo dlea dlevel s fo r producin g encephalopath y o r deat har e lower , typicall y startin g a t approx imatel y 10 0 /ig/dl . Again , however , goo devidenc e exist s fo r th e occurrenc e o f

encephalopath y i n som e a t lowe r levels , i.e. , 8 0 t o 10 0 /ig/dl . 11-2 5P.7 0

I t shoul db e emphasize dtha t onc e encephalopath y occur s deat hi s no t

a t al l a n improbabl e outcome , regardles s o f

th e qualit y o f

medica l treatmen t availabl e at

th e tim e o f

an y acut e crisis . I n fact , cer tai n diagnosti c o r

treatmen t

procedure s themselve s ten dt o exacerbat e matter s an dpus hth e outcom e towar dfatalit y ifth e natur e an dseverit y ofth e prob

le mar e no t

full y recognize do r

ar e misdiagnosed . I t i s als o crucia l t o not e th e rapidit y withwhic hacut e encephalopath y symptom s o r deat hca n develo p in apparentl y asymptomati c individual s o r in thos e onl y apparentl y mildl y affecte db y elevate dbod y burden s o f

lead . I t

i s no t unusua l fo r

rapi d deterioratio n t o occur , wit hconvulsion s o r com a suddenl y appearin g an dprogressin g t o deat hwithi n 4 8 hr . Thi s strongl y suggest s tha t eve n in apparentl y asymptomati c individual s rathe r sever e neura l damag e probabl y doe s exis t at hig hbloo dlea dlevel s eve n thoug hit

i s no t yet overtl y manifeste din ob

viou s encephalopathi c symptoms . Thi s tend s t o b e born e ou t

b y studie s showin g tha t childre n havin g hig hbloo dlea dlevel s (ove r 8 0 t o 10 0 /ig/dl) , bu t no t observe dt o manifes t acut e encephalopath y symptoms , ar e permanently , cognitivel y impaired , a s ar e individual s wh o surviv e acut e episode s o f lea d encephalopathy . Othe r evidenc e tend s t o confir mtha t som e typ e o f neura l damag e doe s exis t in asymptomati c children , an dno t necessaril y onl y at

ver y hig hlevel s o f

bloo d lead . Th e bod y o f

studie s o n low

- o r

moderate-leve l lea deffect s o n neurobehaviora l functions , a s sum marize di n Tabl e 11-4 , presen t overal l arathe r

im

pressiv e arra y o f

dat apointin g t o tha t

conclusion . Severa l well-controlle dstudie s hav e foun deffect s tha t ar e clearl y statisticall y significant , wherea s other s hav e foun dnonsignifican t bu t borderlin e effects . Eve n som e studie s reportin g generall y non significan t

finding s at

time s contai n dat aconfirmin g statisticall y significan t

effects , whic hth e author s at tribut e t o variou s extraneou s factors . Anothe r wa y t o loo k a t th e situatio n i s t o conside r tha t elevate d bloo dlea dleve l i s th e singl e commo n facto r extan t in al l o f th e group s showin g significan t behaviora l deficit s i n th e differen t studies . I t

shoul dals o b e note dthat , give n the'likel y subtl e natur e o f som e o f th e behaviora l o r

neura l effect s probabl e a t lo w level s o f lea dexposure , on e woul dno t expec t t o fin d strikin g difference s in ever y instance . Th e bloo d lea dlevel s associate dwithneurobehaviora l deficit s in asymptomati c childre n appea r t o b e i n exces s o f 5 0 t o 6 0 /ig/dl . Grea t uncertaintie s remain , however , a s t o whethe r thes e exposur e level s (ob

serve dbloo dlea dlevels ) represen t th e level s tha t wer e responsibl e fo r th e behaviora l deficit s ob

served . Monitorin g o f

lea dexposure s i n th e subject s ha s in al l case s bee n highl y intermitten t durin g th e perio do f

lif e precedin g th e behaviora l assessment . I n mos t cases , onl y on e o r

tw o bloo dlea dvalue s ar e provide dpe r

subject . 11.5. 2 Anima l Studie s Pentsche w an dGarro 5 2 initiall y describe dan anima l mode l o f

lea dencephalopath y in whic h morphologica l change s occurre dsimila r t o thos e re porte din children . Neonata l rat s wer e expose dt o lea db y feedin g mother s adie t containin g 4 percen t lea dcarbonate . Th e lea dwa s the n transmitte dt o th e sucklin g youn g vi ath e mothers ' milk . Betwee n 2 3 an d2 9 day s o f

age , 9 0 percen t

o f th e animal s develope dparaplegi alastin g n o longe r tha n 2 weeks . Eighty-fiv e t o 9 0 percen t o f th e paraplegi c animal s die ddurin g thi s period . Neuropathologica l examinatio n o f thes e animal s reveale dcapillar y activation , glia l proliferation , area s o f transudation , an dspott y hemorrhages , pri

maril y in th e cerebellu man dth e striatum . Th e whit e matte r o f th e cerebra l hemispheres , especiall y th e corpu s collosum , wa s als o involved , thoug ht o a lesse r extent . Ischemi c neurona l change s in foca l distributio n wer e rar e an dwer e localize din th e cerebra l cortex . Pentsche w an dGarro 5 2 conclude d tha t th e lea dencephalopath y ofth e sucklin g ra t wa s cause db y adisorde r

i n th e permeabilit y o f

th e capillaries , resultin g in dysori c encephalopathy . Th e sucklin g ra t

therefor e differ s fro mth e huma n in tha t th e latte r

show s amixtur e o f

bot hdysori c an d hemodynami c alterations . Furthe r verificatio n o f th e dysori c natur e o f

lea dencephalopath y in th e sucklin g ra t

wa s provide db y Lamper t e t al., 5 3 wh o use deithe r

colloida l thoriu mdioxid e (Thorotrast ) o r Trypa n Blue , neithe r

o f whic hnormall y pene trate s th e blood-brai n barrier . I n sucklin g rat s poisone dwith4 percen t lea dcarbonate , however , bot hThorotras t

an dTrypa n Blu e wer e foun dt o penetrat e th e striatu man dcerebellum . Sinc e th e initia l descriptio n b y Pentsche w an d Garro, 5 2 lea dencephalopath y in th e ra t ha s bee n replicate db y Thoma s e t al. 24 6 Michaelso n an d Sauerhoff, 24 7 an dKrigma n an dHogan. 24 8 Clase n e t al. 24 9 reporte dlea dencephalopath y in juvenil e Rhesu s monkey s expose dt o 0. 5 g o f lea d pe r da y fo r

6 t o 1 8 weeks . The y reporte d morphologica l change s simila r t o thos e occurrin g in humans , whic hconsiste do f edematou s change s in th e cerebella r

an dsubcortica l whit e matter . Diffus e 11-2 6P.7 1

Referenc e D e l a Burd e an d Choat e (1972)2* 3 O e l a Burd e an d Choat e (1974)22 * Perin o an d Ernhar t (1974)225 Puesche l etal . (1972)9 9 Landriga n e

t al . (1975)22 ?

Rumm o (1974)2 " ' TABL E 11-4 . SUMMAR YO F RESULT S O F HUMA N STUDIE S O N NEUROBEHAVIORA L EFFECT S Populatio n studie d Inne rcity (Richmond , VA

) Followu p sam e subjects Inne rcit y (Ne wYork , NY

) Inne rcity (Boston , MA

) Smelte rare

a (E l Paso , TX

)

Inne rcit y (Providence , Rl ) A TMODERAT E BLOO D LEA D LEVEL S N/grou p Contro l = 7

2 Lead = 7 0 Contro l =6 7 Lead = 7 0 Contro l =5 0 Lead = 3 0 Contro l = 5

6 Lead = 56 Contro l =4 6 Lead = 7 8

Contro l Ss = 4

5 Shor t P b Ss = 1 5 Long P b Ss = 20 Age a t

testing , y r 4 4 7 7 3- 6 3- 6 ? ? 3-1 5 (x = 9.3 ) 3-1 5 (x = 8.3 )

4- 8 (5=5.8 ) 4- 8 (x** = 5.6 ) 4- 8 (x= 5.6 ) Bloo d lead .

mm No t assayed ' 40-100 " Se e above " Se e above " 10-3 0 40-70 <4 0 >4 0 <4 0 40-6 8

x = 23 ±8 7 = 61 ±7

x = 68 ±1 3 Psychometri c test s employe d Stanfor d Binet I Q Othe rmeasure

s WIS C Ful l Scal e IQ Neurologi cexam Othe rmeasure

s McCarthyGenera l Cognitiv e McCarthySubscales Stanford-Binet IQ Neurologi cexam WIS C Ful l Scal e IQ

< WPPS I Ful l Scal e IQ WIS C + WPPS I Combined WIS C + WPP I Subscales Neurologi ctestin g McCarthyGenera l Cognitiv e McCarthySubscales Neurologi cexam ratin g Summar y o f result s ( C = control ; Pb = lead) 3 C = 9 4 Pb = 8 9 C >P b o n 3/

4 test s C=90Pb=8 7 C bette rtha n P

b C >Pbon9/1 0 tests C = 90 Pb = 8

0 OPbo n 5/

5 scale s C = ?Pb = 86 C bette rtha n Pb C=93Pb=8 7 C = 9 1 Pb = 8

6 C = 9 3 Pb = 8 8 OPbo n 13/1 4 scales C >P b o n 4/

4 tests C = 93 ; S = 94 ; L = 88 ; P = 7

7 C+S>L>Pon5/ 5 tests C+SL> P o n rating s TT'TTT - '- - - "

Level s o f significance " p <.0 5 N.S.-P <.0 1 p <.0 1 p<.0 1 N.S. p <.00 1 p <.0 1 N.S. p <.0 1 — p<.00 1 N.S . N.S . p <.0 1 N.S. p <,0 1 N.S. p <.00 1 N.S. p <,0 1 (pvsC ) N.S. p <.0 1 . (pvsC ) N.S .

Koto k e t al . (1977)23 2 Inne rcity

(Rochester , NY

) Pos tencep h Pb = 1 0 4- 8 (x = 5.3 ) Control=3 6 1.9-5. 6 (x = 3.6 ) Lead=3 1 1.7-5. 4 (x = 3.6 ) x = 8 8 ±40 11-4 0 61-20 0

Koto k(1972)22 8 Lansdow n e t al . (1974)22 9 McNei l etal . (1975)230 Inne rcity

(Ne wHaven , CT

) Contro l = 2

5 Lead = 2 4 1.1-5. 5 (x = 2.7 ) 1.0-5. 8 (x = 2.8 ) Inne rcityContro l = 17 2 61 6 (London , England ) Lead = 4 3 61 6 Smelte rare

a Control = 61-152 1.5-1.8(Mdn = 9 ) (E l Paso , TX

) Lead = 23-16 1 1.5-1.8(Mdn = 9 ) 20-5 5 58-13 7 <4 0 40-60 + <4 0 >4 0 Objectiv

e neurologi ctest s IQEfo rsi xabilit y classes : Socia l maturity ; Spatia l relations ; Spoken vocab ; Info , comprehension ; Visua l attention ; Auditor ymemor y Denve r Developmenta l Scal e WIS C WAI S McCarthyGenera l Cognitiv e WISCWAI S Ful l Scal e IQ Oseretsk y Moto rLeve l Californi a Person ality Frosti g Perceptua l Quotien t Finger-Thum b Appositio n C+S>L>Po n

3/1 2 test s I Q Equivalen t fo r each : C = 126Pb=12 4 C = 10 1 Pb = 92 ; C = 9 3 Pb = 92 ; C = 9 6 Pb = 95 ; C = 9 3 Pb = 9 0 C = 10 0 Pb = 9 3 OPbo n 1/

3 Subscale s C = 10 0 Pb = 10110 5 C=82Pb=8 1 C=89Pb=8 7 C = 10 1 Pb = 9 7 C = 8 0 Pb = 7 2 C = 10 0 Pb = 10 3 C = 2 7 Pb = 2 9 N.S. p <.0 1

(pvsC ) p <.10fo r spatia l p > . 10fo ral l othe rabilit y classe s N.S . N.S . N.S . N.S . N.S . N.S . N.S . N.S . a Mea n tes t score s obtaine d fo r contro l childre n ar e indicate d b y C = T ; mea n score s fo r respectiv e lead-expose d group s are indicate d b y P b = x (excep t fo r Rummo'-- ' stud y where C = control , S = short-ter m lead-ex pose d subjects ; L = lon g ter m lead-expose d grou p an d P = postencephalopath y lea d group) . b N.S . = nonsignificant , i.e . p >.05 . Not e exceptio n o fp <.05 . Not e exceptio n o f p < . 1 0 liste d fo rspatia l abilit y result s i n Koto k et al. 2 3 2 study . ^Urinar y coproporphyri n level s wer e not elated . < - O r 3 0 /xg/d l o r abov e wit h positiv e radiologi c findings . Th e latte rsuggest earlie rexposur e i n exces s o f 50-6 0 Mg/dl . e Assay s fo r lea d i n teet h showe d th e Pb-expose d grou p t o b e approximatel y twic e a s hig h a s control s (20 2 /ig/ g vs . 11 2 /ig/g , respectively) . Use d fo r childre n ove r5 year s o f age . 8 Use d fo r childre n unde r5 year s o f age . 11-2 7P.7 2

astrocytosi s an dglia l nodule s wer e foun din whit e matte r alon g wit hperivascula r exudate . Lea dencephalopath y in th e mous e wa s firs t de

scribe db y Rosenblu man dJohnson 25 0 who , lik e Pentsche w an dGarro , use dth e sucklin g animal . I n contras t t o th e ra t

brain , th e striatu man d cerebellu mo f

mic e fe deithe r

0. 5 o r 1 percen t

lea d carbonat e displaye donl y fain t stainin g withTrypa n Blu e (excep t

fo r asingl e anima l withdarkl y staine d cerebellum ) an donl y occasiona l paraplegia . Th e mos t strikin g vascula r

chang e in th e poisone dmic e wa s th e appearanc e o f intervascula r

strand s throughou t

th e brain , especiall y in th e hippocampu s an dbasa l ganglia . Rosenblu man dJohnson 25 0 con clude dtha t

n o cerebra l edem aan dfoca l destructiv e lesion s wer e foun din th e mous e brains . Therefore , th e histologica l respons e o f th e sucklin g mous e ex pose dt o lea ddiffer s fro mtha t see n i n th e sucklin g rat . Thes e difference s ar e probabl y no t attributabl e t o differen t

exposur e level s ( 4 percen t carbonat e in th e ra t versu s 1 percen t

in th e mouse) , becaus e th e foo dconsumptio n pe r

uni t bod y weigh t

i s thre e t o fou r time s greate r

in th e mous e tha n in th e rat , mak

in g th e externa l exposure s roughl y equivalent . Well s e t al. 25 1 hav e recentl y reporte do n experi

menta l lea dencephalopath y in calves . Fou r Jerse y bul l calve s wer e expose dt o 2 0 mg/kg/da y o f lea d acetate , beginnin g at

3 month s o f

ag e an dlastin g fo r 8 t o 27 3 days . Histologica l evaluatio n ofth e brain s o f expose danimal s reveale dfoca l vacuolatio n ofth e neuropil , neurona l necrosis , an dchange s in th e capillar y wall s in th e cerebra l corte x an din subcor

tica l areas . Lesion s i n thes e cattl e wer e simila r t o thos e see n in childre n withlea dencephalopath y in tha t bot hsho w no t

onl y vascula r

change s in th e brai n withedem abu t als o area s o f

neurona l necrosis . I n summary , th e histopathologica l change s as sociate dwit hlea dencephalopath y var y amon g specie s an dar e characterize db y thei r relativ e in

volvemen t

o f neurona l degeneratio n an dvasculopa

thy . Th e fac t

tha t lea dencephalopath y i s reporte dt o occu r i n th e absenc e o f

cerebra l edem ain man, 19 8 mouse, 25 0 an dguine apig 25 2 i s argumen t fo r adirec t neurona l involvemen t

o f lead . Recen t

studie s have , in fact , suggeste ddirec t neurona l alteration s b y lead . Bul l e t

al. 25 3 reporte dtha t

lea dinterfere s wit hpotassium-stimulate drespiratio n o f ra t cerebra l corte x slices , an dNathanso n e t al. 1 7 re porte dtha t

lea dinhibite dbrai n adeny l cyclas e in vitro. N o distinctio n ca n b e mad e in thes e studies , however , betwee n neurona l an dothe r cel l types . Thus , adirec t

biochemica l effec t

o f lea do n th e neuro n canno t b e definitivel y conclude dfro mthes e studies . Th e relativ e involvemen t o f th e capillar y be di n th e lea dencephalopath y ma y depen do n th e degre e o f maturatio n a t

th e tim e o f

exposure . Bouldi n e t al. 25 2 fo r example , wer e abl e t o produc e lea den cephalopath y i n adul t

guine apig s withn o cerebra l edem ao r increase dcapillar y permeability , wherea s th e sucklin g ra t

show s thes e effect s almos t ex clusively . Sinc e th e initia l descriptio n o f lea dencephalopa

th y in th e ra t

b y Pentsche w an dGarro, 5 2 considera

bl e effort ha s bee n mad e t o defin e mor e closel y th e exten t o f CN S involvemen t

a t subencephalopathi c level s o f lea dexposure . Thi s experimenta l effort ha s focuse dalmos t

exclusivel y o n th e developin g organ ism . Th e interpretatio n of alarg e numbe r o f exper U ment s dealin g withearl y exposur e t o lea dhave , however , bee n confounde db y anumbe r o f flaw s in experimenta l design . Perhap s th e mos t

notabl e o f

thes e experimenta l shortcoming s ha s bee n th e presenc e o f undernutri

tio n i n experimenta l animals . Change s i n nutritiona l statu s durin g earl y brai n developmen t ar e know n t o produc e change s in behavior. 25425 5 Castellan o an d Oliverio, 25 6 fo r

example , reporte damarke ddela y in neurologica l development , a n increas e in explorato

r y locomoto r

activity , an dalowere davoidanc e per formanc e in mic e tha t

wer e undernourishe ddurin g earl y developmen t

b y bein g reare din larg e litters . Neurochemica l processe s hav e als o bee n show n t o b e affecte db y earl y undernutrition . Eckher t e t al. 25 7 re porte dchange s i n cholinergi c enzym e activitie s whe n rat s wer e place do n protein-deficien t diet s durin g variou s period s o f development . Thei r result s indicat e tha t

"th e relationshi p betwee n th e activit y o f

individua l cholinergi c enzymes , nutri

tiona l statu s an ddevelopmenta l ag e i s comple x an d i s no t th e sam e fo r

differen t brai n region s o r

eve n th e sam e brai n regio n expose dt o undernutritio n durin g differen t period s o f

development. " Therefore , i n reviewin g th e anima l literatur e concerne dwit hth e neurotoxicolog y o f

lea dexposure , th e possibl e con tributio n o f

undernutritio n mus t

b e considered . Furthermore , th e possibilit y als o exist s tha t lea dan d undernutritio n ma y b e havin g asynergisti c effec t o n nervou s syste mdevelopment . I n thi s case , th e method s o f

pair-feedin g currentl y employe di n som e studies 247

- 25 8 ma y no t

provid e adequat e contro l fo r thi s undernutrition . Example s o f dietar y factor s know n t o affec t

susceptibilit y o f

lea dtoxicit y hav e bee n reviewe db y Goye r an dMahaffey. 25 9 Animal s fe ddiet s containin g lowe r tha n recom - -2 8mende dconcentration s o f nutrient s generall y retai n highe r concentration s o f

lea din tissue s tha n animal s o n norma l diets. 25 9 However , almos t nothin g i s know n abou t

th e effect s o f

elevatin g nutrien t

intak e abov e recommende dlevel s —whic hi s th e cas e wit h mos t commercia l laborator y chow s —o n th e tox icity o f lead . Additiona l researc hi s neede di n thi s area , an dunti l furthe r

dat aar e availabl e o n th e in

fluenc e o f

varyin g degree s o f

overnutrition , varia

tio n i n nutrien t

intak e mus t

b e suspecte do f

alterin g th e toxicit y o f

lead . 11.5.2. 1 DEVELOPMEN T Severa l laboratorie s hav e reporte do n th e effect s o f perinata l lea dexposur e o n physical , reproduc

tive , an dneurologica l development. 24725026026 1 Un

fortunately , in anumbe r o f studie s eithe r

n o contro l wa s provide dfo r

undernutrition, 25026026 2 o r under

nourishe dpair-fe dcontrol s showe dsimila r develop

menta l delays, 24 7 thu s maskin g an y direc t effect s o f lead . Make r e t al. 26 3 als o examine dth e effect s o f lea d exposur e o n brai n developmen t in mice . Tw o method s wer e use din an attemp t t o contro l fo r

th e effect s o f earl y undernutrition . I n th e firs t experi

ment , tw o pair-fe dlitter s wer e used . Pair-feedin g wa s accomplishe db y allowin g alitte r acces s t o a n amoun t o f norma l cho w equivalen t t o tha t consume d b y alitte r

o n a0. 8 percen t

lea ddiet . Bot hpair-fe d litter s showe dareductio n in brai n weigh t at 3 0 day s o f age , a s di dth e lead-treate danimals . Th e tw o pair

fe dlitters , however , differe din th e relativ e reduc

tio n in brai n weight , on e showin g a n identica l respons e t o th e lead-treate dgroup s an don e showin g brai n weight s intermediat e betwee n control s an d lead-treate danimals . A secon dattemp t t o alte r th e nutritiona l stat e ofth e animal s wa s accomplishe db y alterin g litte r

size s ( 3 pup s versu s 6 pups) . Bod y weight s o f

contro l animal s o f

th e tw o litte r

siz e group s wer e equivalent , however , s o tha t varyin g th e litte r siz e ove r

thi s rang e di dno t

effectivel y produc e undernutrition . Therefore , th e conclusio n o f Make r e t al. 26 3 tha t

underconsumptio n o f

foo dalon e doe s no t accoun t fo r th e slo w developmen t

o f litter s o n a lea ddie t i s no t supporte db y thei r

data . Reite r e t al. 26 4 examine ddevelopmen t i n rat s ex pose dt o lea dbot hprenatall y an ddurin g lactatio n vi ath e mothers ' milk . The y reporte dadela y i n bot h th e ag e a t

ey e openin g an dth e ag e a t developmen t

o f th e ai r rightin g refle x i n th e 5 0 pp mtreatmen t group . Thi s exposur e leve l wa s show n t o produc e n o depressio n i n growth , whic hsuggeste dadirec t effec t o f lea do n nervou s syste mdevelopment . N o differenc e i n th e developmen t ofth e acousti c startl e respons e wa s observed . Kimme l et al., 26 5 usin g a simila r experimenta l design , als o reporte ddelay s i n bot hsurfac e an dai r

rightin g in rat s expose dt o 5 0 o r 25 0 pp mlead ; an dn o difference s wer e foun din eithe r auditor y startle , pinn adetachment , ey e open ing , ea r opening , o r

inciso r eruption . Sexua l maturatio n appear s t o b e on e aspec t o f developmen t

tha t i s quit e sensitiv e t o disruptio n b y lea dexposure . Kimme l e t al. 26 5 reporte dadose-re

late ddela y in vagina l openin g in femal e rat s ex pose dt o 25 , 50 , o r

25 0 pp mlea dacetat e in th e drinkin g wate r

startin g at

conception . I n th e grou p expose dt o 2 5 pp mlead , n o difference s in growt h rate s wer e observed . Thi s suggest s adirec t effec t o f lea do n sexua l maturatio n rathe r tha n achang e sec ondar y t o bod y weigh t

changes . De r e t al. 26 6 reporte do n th e combine deffec t o f parentera l administratio n o f lea dacetat e an dlo w protei n die t

(10 0 fig subcutaneousl y daily , age s 2 0 t o 6 1 days ) o n sexua l developmen t in th e Sesc o rat . Lea dsignificantl y delaye dth e ag e a t whic hvagina l openin g occurre di

n animal s o n th e contro l diet . Female s give n lea din combinatio n wit hlo w protei n diet s di dno t

exhibi t vagina l openin g throug h6 1 day s o f age . Th e author s interpre t thes e dat ao n th e basi s o f alead/protein-deficienc y interaction . However , sinc e animal s wer e give n 10 0 fig o f lea d pe r da y regardles s o f

bod y weight s an dsinc e thei r bod y weight s wer e at

2 6 percen t

o f control , th e dosag e o f lea dpe r uni t bod y weigh t

wa s 40 0 percen t greate r tha n lead-treate danimal s o n acontro l diet , whic hma y accoun t

fo r th e additiona l dela y i n maturation . Gra y an dReiter 26 1 studie dth e effect s o f lea dad

ministratio n ( 5 mg/m l i n th e drinkin g wate r a t par turition ) o n sexua l maturatio n in th e mouse . Vagina l openin g wa s delaye dabou t 4 day s in lead-treate d animals . N o dela y i

n developmen t

wa s see n i n pair

fe dcontrols , furthe r

suggestin g aprimar y effec t o f lea do n sexua l maturation . Furthermore , n o dela y i n sexua l maturatio n wa s observe din animal s whe n lea dwa s discontinue dat weaning . Therefore , th e presenc e o f

lea dat th e tim e o f

maturatio n appear s essentia l fo r

th e lead-induce ddela y an dma y b e re late dt o it s effect s o n circulatin g hormone s at th e tim e o f puberty . 11.5.2. 2 LOCOMOTO RACTIVIT Y I n th e anima l model , th e mos t commonl y employe dbehaviora l inde x o f lea dtoxicit y ha s bee n locomoto r

activity . A s withothe r

behavior , locomo

to r activit y i s influence db y avariet y o f factor s tha t 11-2 9P.7 4



### includ e sex , age , time andduratio n o f testing , typ e o

f measurement , etc . Th e relativ e influenc e o f thes e factor s on th e observe dactivit y will var

y wit hth e experimental metho demployed . Th e endpoin t bein g measure di s activit

y (no t necessarily ambulation) , andth e nervous-systemprocesse s responsibl e fo r thi s activit

y andthei r

relativ e contribution s ma y be different . Tapp, 26 7 

### fo

r example , compare dseve n different measure s of

activit y i n th e rat an dfound virtuall y n o intercorrelation . Thes e result s sugges t tha t th e test s he employe dwer e no t measurin g th e sam e behavior . Capobianc o andHamilton 26 8 

### ex amine dth e effects o

f variou s brai n lesion s on am bulatio n a s measure db

y thre e different

methods : open-field , stabilimeter , an dactivit y wheels . Thes e differen t measure s of

activit y were affecte d differentl y b

y agive n brai n lesion . Lesion s o f th e diagonal band , fo

r example , produce dincrease dac tivit y i n th e runnin g wheel , decrease dactivity i n a stabilimeter , an dno chang e i n activit y i n a n open field . No t onl y i s th e typ e o

f activity-measurin g devic e important , bu t als o o f importanc e i s th e lengt

ho f time over whichth e activit

y i s measured . Short-term measurement s o

f activit y i n anovel environmen t hav e bee n terme dexploratory activit y o r locomoto r reactivity an dprimaril y reflec t th e animal' s reactio n t o th e novel environment . Thi s reactivity i n turn will b e affectedb

y th e structur e o

f th e environment . I

n orde r t o determin e spontaneou s o r basal activity levels , a n animal mus t

resid e i n a n environmen t

over long period s o

f time . Onc e th e animal i s establishe d i n th e environment , th e activit y level s of

th e animal , especiall y th e rodent , will be highly dependen t o n th e tim e o

f day . Therefore , i

n reviewin g th e lea

dliterature , i

t mus t be remembere dthat

locomoto r

activit y measure ment s d o no t

represen t aunitary behavior ; carefu l consideratio n mus t

b e given t o th e particular experi

menta l method s employed . I

n addition , attempt s t o extrapolat e th e result s o

f a n activit y measurement

i n animal s directl y t o th e clinical situatio n ar e unwar ranted . A brie f

summar y of pertinen t studie s i s given i n Tabl e 11-5 . TABL E 11-5 . EFFECT S O F LEA D EXPOSUR E O N LOCOMOTO R ACTIVITYI N LABORATOR YANIMAL S

Referenc e Alle n etal.*' * Bornschei n etal. 2 7 0

Brown" "

Driscol l an d Stegner" "

Grayan d Reiter"' 1

Hasting s etal."' *

Kostas etal." " Specie s

Monkey Mouse , (Charle s River ) CD- I Rat(Ba rF • Rabbitry ) Ra t (Simonsen )

Mouse , (Charle s River ) CD- I Rat , (Long Evans , Charle s River ) Rat(Long-Evans ) Blu e Spruc e Exposure condition s

0.5- 9 mg/kg/da yfo r1 2 week s 5 mg/m l lea d acetat e i n drinkin g water , startin g at parturitio n 3 5 mg/k g P.O . t o dam s fro m parturition to 2 1 day s 10 * an d 10 " M lea d acetat e i n drinkin g wate r fro m conceptio n 5 mg/m l lea d acetat e i n drinkin g water , startin g a t parturition 0. 2 o r1. 0 mg/m l fro m parturition t o 2 1 day s

0.05-5.0 % lea d acetat e i n mother' s cho

wfro m parturitio n unti l 2 1 days . Continue d i n offsprin g a t 0.25-2 5 pp m i n cho

w unti l 3 5 day s Lea d concen tration . ^1 % Bloo d Brai n 160-40 0 120-19 0 200-30 6

Contro l = 11± 4 0. 2 mg/m l = 29± 5 1. 0 mg/m l = 42± 4 Test conditions , i n orde ro presentation : 1 . Metho d 2 . Lengt h of testin g 3 . Grou p siz e 4 . Aj e Observe d locomoto r activit y Proximit ycounte r 3 hours Individua l 3 5 day s Photoactomete r 2 0 mi n Individua l 4 9 day s Open-fiel d 2 mi n Individua l 3 1 day s Residentia l maz e 90-24 0 mi n Individua l 30 , 50,13 0 day s Runnin g whee l 3 week s Individua l 30-5 1 day s Shuttl e box , activit y whee l 1 h r Individua l 75-7 7 days ; 90-9 3 day s Nutritiona l statu s Norma l Undernourishe d

Undernourishe d

Undernourishe d

Norma l Result s

Hyperactivit y (qualitativ e measures ) Norma l

Norma l

Hypoactiv e (61 % o

f control ) Hypoactiv e (75-80 % of control ) Norma l

Norma l - 0.05 % grou p Hyperactivit yi n shuttl e undernourishe d i n bo x(182 % o

fcontrol) . 5-5.0 % Norma l i n activit y

wheel . 

### 11-3 0TABL E 11- 5 (continued) .

Referenc e Overman 27

5

Reiter"' " Reite retal." 7 6

Reite re t al. 2 ' 4 Cahil l etal. 27 '

Reite retal. 2 " '

Sauerhof f an d Michaelson 27 8 Sauerhoff27 ' Silbergel d an d Goldberg262.280.28 i Specie s

Rat , (Long Evans Charles River)

Rat , Spragu e Dawley , Charles Rive r

Rat , Spragu e Dawley , Blu e Spruc e

Mouse , Charles River , CD- I

Rat , Spragu e Dawley , C

O

Mouse , Charles River , CD- I Sobotk a an d Cook

2 " 2 Rat , Spragu e an d Sobotk

a e t al. 28 3 Dawle

y(Charle s River )

Sobotk a etal. 28 4

Winnek e etal. 28 '

Zenicketal. 2 " " Do g (Beagle )

Ra t (Wistar )

Rat , Spragu e Exposur e condition s

10 , 30 , 90/mg/kg/da

yb y intubatio n fro m 3-2 1 day s o f ag e

5 % lead carbonate i n mother' s cho

wfro m parturitio n t o 1 6 days , 5 0 ppm i n drinkin g wate r fo rremainde ro

f experimen t 5,5 0 ppm i n drinkin g water . 40 da

y pretreatmen t o

f parents . Continue d fro m conceptio n throug h adulthoo d 5 mg/m l lead acetat

e i n drinkin g wate rfro m parturitio n unti l 4

5 day s 4 % lea d carbonate i n mothers ' cho

wfro m parturitio n t o 1 6 day

s post-partum , 40 ppm i n drinkin g wate r 2 , 5,1 0 mg/m l lead acetat e i n drinkin g wate r startin g a t parturitio n 8-9 1 mg/kg/da

yb y intubatio n fro m 3-2 1 day s o f ag e

1 o r4 mg/kg/da

yorall y fro m 2 week

s to 5 month s 1.3 8 g lead acetate/k

g o f cho w(74 5 pp m Pb) fo r 60 day s pretreatmen t to mothers . Continue d i n offsprin g fro m -conceptio n t o testin g 75 0 o r100 0 mg/kg/da

yto female s o n restricte d waterin g schedul e fro m 21-99 day s o f age . Exposur e continue d throug h gestatio n an d weaning . Lea d concen tration . fig% Bloo d 2 1 day s 90 mg/k g = 226 ±2 1 3 5 day s 9 0 mg/k g = 56± 5

18 0 da y males 0 = 5 ±0. 5 5 = 6 + 0. 4 50 = 10 ± 0. 6

22 day s 8 1 mg/k g = 71±1 2 3 5 day s 8 1 mg/k g = 23±1. 4

1 6 day s 26. 6 19 0 day s • 28. 5 Brai n

18 0 da y males 0=18 + 50 = 20 ± 50 = 27 ±

2 9 day s 88 ±1. 1 Tes t conditions , i n orde rof

presentation : 1 . Metho d 2. Lengt h of testin g 3 . Grou p siz e 4 . Ag e Jiggl e platfor m Fou rday s Individua l 22-6 5 Jiggl e cage ; Residentia l maz

e 4 min ; 1 4 day

s Individual ; grou p o

f 3 13-4 4 days ; 120-160 day s Residentia l maz

e 5 day s Group s o f 3 2 12 0 day s 2 Residentia l maz

e 2 day s Individua l 10 0 day s Selectiv e activity mete r 2 4 hour s Group s o f 6 26-29 , 5 0 Proximit ycounte r 3 hour s Individua l 30-15 0 day

s Photoactomete r 3 0 mi n Individua l 24-2 8 day s Ope n fiel d Individua l 3- 4 month s Ope n fiel d 3 min , o n consecutiv

e day s Individua l 90-140 day

s Open fiel d 3 min , o n 1 0 consecutiv

e day s Individua l 22-3 2 day s Nutritiona l statu s Norma l

Undernourishe d

Norma l

Undernourishe d

Undernourishe d

Undernourishe d

Norma l

No t indicate d

Norma l

Undernourishe d Result s Hyperactiv

e

Transien t hyperactivity (200 % o f contro l a

t 1 3 days) . Norma l a

t 4 4 days . Norma l level s i n adults ; bu t disrupte d ultradia n rhythms . Hypoactivit

y(53-78 % o

f controls )

Norma l

Hyperactiv

e a t 29 day s (140190 % o

f control ) Norma l a t 50 day s Hyperactivit

y(300-400 % o f control )

Norma l

Hypoactiv e Hyperactiv

e (129 % o

f control )

Initia l hypoactivityi n 10 0 mg/k g grou p (days 1 an d 2 ) Hyperactiv

e b y th e 7t h tes t day .

11-3 1P.7 6

Th e dat at o b e reviewe dher e sugges t tha t perinata l lea dexposur e produce s a n altere dreac tivit y o f a n anima l t o anove l environment . Reac

tivit y i s increase din th e youn g animal , bu t thi s in

crease dreactivit y disappear s a s th e anima l matures . I n th e adul t

animal , o n th e othe r

hand , th e lea dex posur e result s i n areduce dreactivity . A s wil l b e seen , th e exac t

natur e ofth e chang e i n locomoto r ac tivit y brough t

abou t b y thi s altere dresponsivenes s will depen dheavil y o n th e structur e o f th e tes t en vironment . Sauerhof f an dMichaelson 27 8 an dSauerhoff 27 9 ex pose dlactatin g female s t o lea dusin g amodificatio n o f th e Pentsche w an dGarro 5 2 exposur e regimen . Litte r mate s wer e teste da s agrou p at 2 5 t o 2 8 day s o f ag e in ates t

cas e simila r

t o th e hom e cage . Th e dat awer e collecte din fou r block s o f

3 h r an don e bloc k o f 1 2 hr , extende dove r

4 days . Althoug hthe y ar e presente da s count s pe r hou r fo r a24-h r period , dat arepresen t

reactivit y attributabl e t o multipl e short-ter mexposure s t o anove l environment , and , therefore , ar e no t

comparabl e withdat aobtaine db y continuou s samplin g ove r a24-h r period . Offsprin g of alead-expose dmothe r exhibite delevate dactivit y levels . Sinc e onl y on e grou p ( n = 6 pups ) wa s teste d fro meac htreatment , however , n o statistica l tes t ca n b e applie dt o thes e data . Usin g asimila r

exposur e regimen , Reiter 25 8 an d Reite r e t al. 27 6 expose danimal s t o 5 percen t lea d carbonat e i n th e cho w startin g a t parturition . Animal s wer e repeatedl y teste dat variou s ages , beginnin g a t

1 3 day s o f

age , usin g a4-mi n jiggl e platfor mactivit y measurement . Thi s measurin g devic e detect s bot hlocomoto r activit y an dstation

ar y bod y movements . The y reporte da n increase d activit y (20 0 percen t

o f control ) i n 13-day-ol d animals . Thi s elevate dactivit y decline dwit hag e an dreturne dt o contro l level s b y 4 4 day s o f age . Comparison s wer e mad e wit hpair-fe dcontrol s sinc e thi s exposur e resulte di n asignifican t growt himpair

ment . Whethe r

thi s retur n t o norma l level s wa s cause db y maturatio n o r b y repeate dtestin g wa s no t determine di n thi s study . Animal s wer e als o teste da s adult s (12 0 days ) in aresidentia l maze , whic hallow s continuou s measuremen t o f activit y ove r

extende d period s o f

time ; thi s tes t

showe dn o difference s i n th e activit y level s a s aresul t o f treatment . However , th e ultradia n rhythm s o f

activit y see n i n contro l animal s durin g th e nocturna l perio d(short-term , 4/h r oscillatio n i n activity ) wer e absen t i n lead-expose d animals . Overmann 27 5 use dasimila r jiggl e platfor mt o measur e activit y in 22

- t o 65-day-ol drats . A s in th e Sauerhof f an dMichaelso n study, 27 8 animal s wer e rotate dbetwee n testin g cages , and , therefore , th e ob

serve dincreas e in activit y wa s consisten t wit ha lead-induce dchang e in locomoto r reactivity . I n thi s experiment , pup s wer e directl y expose db y dail y in

tubatio n rangin g fro m1 0 t o 9 0 mg/kg/day . Thi s ex posur e i s simila r

t o tha t use db y Sobotk aan d Cook, 28 2 wh o employe dintubatio n level s o f 9 t o 8 1 mg/kg/day , bu t

wh o reporte dn o difference s in ac tivit y in aphotoactometer . On e strikin g differenc e betwee n thes e tw o experi

ment s wa s i n th e reporte dbloo dlea dlevels , show n in Tabl e 11-6 . Therefore , th e highe r interna l ex posur e see n in Overmann' s experimen t ma y hav e ac counte dfo r

th e differenc e i n th e observe d behaviora l effects , althoug hdifference s i n experi

menta l protoco l may als o hav e accounte dfo r difference s in th e behaviora l effects . TABL E 11-6 . LEA D EXPOSUR E AN D RESULTIN G BLOO D LEA D LEVEL S I N EXPERIMENT S MEASURIN G LOCOMOTO R

ACTIVITYI N RAT S Bloo d lead.ug/d l Experimen t 2 1 t o 2 2 day s 35 day s Sobotk a an d Coo k 2 8 2 an d Sobotk a etal. 2 " (8 1 mg/kg/day ) Overmann 27 5 (9 0 mg/kg/day ) 7 1 ±12. 4 2 3 ±1. 4 226. 1 ± 21. 1 5 6 ± 4. 6 Tw o differen t

laboratorie s hav e reporte do n th e effect s o f lea dadministratio n o n open-fiel dactivit y in 30

- t o 40-day-ol drats . Driscol l an dStegner 27 2 re porte dadecrease dactivit y in animal s teste dfo r 2 min . Zenic k

e t al. 28 6 teste danimal s fo r 3 mi n i n a n ope n fiel do n 1 0 consecutiv e days . O n th e firs t 2 day s o f testing , animal s fro mth e hig hexposur e grou p (100 0 mg/kg/da y i n th e drinkin g wate r o f th e mother ) showe dadecrease dactivit y simila r t o tha t reporte db y Driscol l an dStegner. 27 2 B y th e sevent h da y o f testing , however , thes e animal s wer e ambulat

in g a t ahighe r leve l tha n controls . Thes e dat aca n als o b e interprete da s a n increase dlocomoto r reac tivit y i n lead-treate danimal s tha t i s initiall y manifeste din a n ope n fiel da s decrease dambulation . Wit hrepeate dexposure , th e animal s sho w a n ele

vate dactivit y simila r

t o tha t in previousl y reporte d studies . Th e differenc e in th e directio n o f lead-in

duce dchang e i n initia l activit y level s in thes e ope n fiel dexperiment s a s compare dt o th e jiggl e platfor m experiments 25827 5 i s probabl y aresul t o f th e difference s i n th e siz e o f th e tes t environments . Th e large r ope n fieldresult s in decrease dactivit y in lead-expose dhyperreactiv e animals , wherea s i n th e 11-3 2smalle r jiggl e platfor mth e animal s sho w increase d activity . Finally , Hasting s e t

al. 27 3 reporte dn o difference s i n running-whee l activit y o f 30-day-ol danimal s ex pose dt o lea db y sucklin g wit hmother s receivin g 1 mg/m l lea din th e drinkin g water . Thi s exposur e resulte di n bloo dlea dvalue s o f 4 2 figldl a t weaning . Sinc e animal s d o no t

normall y sho w muc hrunnin g activit y upo n initia l exposur e t o th e runnin g wheel , ' th e effect s o f

thi s lea dexposur e o n reactivit y canno t b e adequatel y tested . Thes e result s d o demonstrat e tha t long-ter mrunnin g whee l activit y ( 3 weeks ) wa s no t disrupte di n thes e young , lead-expose danimals . A t o r abou t th e tim e o f

sexua l maturation , lea d exposur e ha s no t

bee n show n t o alte r

activit y level s i n th e rat . A s previousl y indicated , Sauerhof f an d Michaelson 27 8 an dReite r e t al. 2 7 6 foun dn o difference s in activit y in animal s teste dbetwee n 4 4 an d5 0 day s o f

age . Thes e wer e animal s whic hwer e reporte dt o hav e increase dactivit y at ayounge r

age . Brown 27 1 als o reporte dn o difference s i n locomoto r activit y i n animal s teste da t 4 9 day s o f

ag e eithe r

in an photoactomete r

o r i n an ope n field . Availabl e dat aals o sugges t tha t perinata l ex posur e t o lea dma y produc e adecrease dreactivit y in th e adul t animals . Kosta s e t

al. 27 4 measure dlocomo

to r activit y in adul t

rat s expose dt o eithe r

0.05 , 0.5 , o r 5. 0 percen t

lea dcarbonat e in th e cho w fro mpar turitio n unti l weanin g an dt o 0.25 , 2.5 , o r 2 5 pp m fro mweanin g unti l 3 5 day s o f age . Tw o measure ment s o f activit y wer e employed . Animal s teste dfo r 1 h r in ashuttl e bo x activit y cag e wer e foun dt o hav e increase dactivity , wherea s animal s teste din runnin g wheel s showe dn o differenc e fro mcontrols . Thi s lac k o f sensitivit y o f

th e runnin g whee l t o lead-in

duce dchange s in activit y i s consisten t withth e find

in g o f Hasting s e t

al. 27 3 Again , th e natur e o f th e chang e i n shuttl e bo x activit y ma y b e interprete din term s o f alead-induce ddecreas e in reactivit y towar danove l environment , sinc e rat s mad e mor e reactiv e woul dten dt o freez e i n thi s environment , thu s causin g decrease dambulation . Winnek e e t al. 28 5 foun dasimila r

chang e in reactivit y a s indi

cate db y open-fiel dactivit y score s ove r 5 successiv e day s o f testing . Lead-treate drat s ha dsignificantl y elevate dactivit y o n th e firs t 3 day s o f

testing , an d activit y ha dreturne dt o norma l o n day s 4 an d5 . Reite r e t al. 26 4 reporte dalead-induce ddecreas e i n activit y i n adul t

animal s teste din aresidentia l maze . Thi s tes t

syste mallowe dfo r

measuremen t

o f variou s component s o f

th e animals ' activity , includ

in g exploratory , diurnal , an dnocturna l activity . Ex

plorator y activit y wa s initiall y suppresse din lead

treate danimals , bu t thi s differenc e disappeare da s th e animal s becam e establishe din th e environment . O n th e othe r

hand , activit y level s remaine dsup presse ddurin g th e nocturna l period . I n asecon dstudy , Reite r e t al. 27 6 reporte dn o differenc e in residential-maz e activit y o f adul t lead

treate danimals . The y speculate dtha t th e lac k o f a lea deffec t

o n locomoto r

activit y in th e secon dex perimen t ma y hav e bee n th e resul t o f th e choic e o f anima l supplie r

(Charle s River) . Sinc e th e Charle s Rive r animal s wer e normall y les s activ e in th e maze , i t ma y hav e bee n difficul t t o lowe r

thei r activit y furthe r wit htreatment . Difference s in experimenta l protocol , i.e. , difference s in dos e an dperio do f ex posure , however , als o may hav e accounte dfo r th e difference s in observe dactivity . I n summary , dat ao n th e ra t sugges t tha t perinata l exposur e t o lea dmay produc e a n increase dreac tivit y whic hdisappear s a s th e anima l matures . Thi s effec t coul dresul t

fro madela y in norma l matura tio n o f forebrai n inhibitor y systems. 28 7 A s th e lead

treate danimal s mature , the y pas s throug haperio d o f norma l reactivit y whic hthe n progresse s t o a decrease dreactivit y in th e adul t animal . Thes e dat a woul db e consisten t

withamaturationa l la g see n in children 28 8 an dpos e a n interestin g hypothesi s tha t require s furthe r

testing . Sobotk ae t

al. 28 4 hav e reporte ddecrease dambula

tio n i n youn g dog s expose dt o lea dan dteste din a7

- b y 7-f t ope n field . Alle n e t

al. 26 9 expose dinfan t monkey s t o lea dvi athei r formul aan dreporte dhy

peractivit y fro m3 t o 5 month s o f age . Thes e dat a an dth e dat ao f

Sobotk ae t

al. 28 4 ar e consisten t

with th e lead-induce dincreas e in reactivit y see n i n th e youn g rat . Th e dat ao f Alle n e t

al. 26 9 mus t

b e qualified , however , sinc e n o quantitativ e measur e o f activit y wa s made . I n aserie s o f

ofte n cite dpapers , Silbergel dan d Goldberg 262

- 280

- 28 ' reporte dlead-induce dhyperac

tivit y in mice . Lactatin g female s wer e expose dt o lea dacetat e in th e drinkin g water , startin g a t par turition , in concentration s o f eithe r 2 , 5 , o r

1 0 mg/ml . Th e author s reporte da300

- t o 400-percen t increas e in locomoto r

activit y tha t

extende dfro m3 0 t o 15 0 day s o f

ag e in th e offspring . Th e lac k of acon tro l fo r th e growt hretardatio n foun din th e iead

treate dgroup s make s interpretatio n o f thes e dat a difficult . A s previousl y indicated , Castellan o an d Oliverio 25 6 reporte dtha t earl y undernutritio n pro duce s hyperactivit y in mice . Therefore , th e observe d hyperactivit y ma y hav e resulte dfro mth e under

nutrition , independen t

of alea deffect . Greate r con cern , however , stem s fro mth e subsequen t failur e o f 11-3 3P.7 8

tw o differen t

laboratories 261

- 27028 9 t o replicat e th e findings o f

Silbergel dan dGoldberg , usin g th e sam e strai n o f mous e an dth e sam e exposur e regimen . Bornschei n e t

al. 27 0 expose dlactatin g mic e t o 5 mg/m l lea dacetat e an dteste doffsprin g i n activit y chamber s identica l t o thos e employe db y Silbergel d an dGoldberg. 262

- 280

- 28 1 The y wer e unabl e t o verif y lead-induce dhyperactivit y in mic e eve n thoug h undernutritio n wa s als o presen t in thei r animals . Gra y an dReiter 26 1 wer e als o unabl e t o demon

strat e hyperactivit y in lead-expose dmice , usin g a residentia l maz e t o measur e activity . Furthermore , Reite r e t al. 28 9 wer e unabl e t o finddifference s i n th e activit y o f

mic e experimentall y expose dt o lea dfro m birt ht o 4 5 day s in Goldberg' s laborator y an dthe n transporte dt o th e author' s laborator y fo r behaviora l testing . Silbergel dan dGoldberg 280

- 28 1 als o studie dth e locomoto r

respons e o f

lead-expose dmic e t o variou s drug s tha t

ar e use din th e treatmen t an ddiagnosi s o f minima l brai n dysfunctio n i n children . Mos t

nota bly , the y reporte dtha t

thei r lead-treated , hyperac

tiv e mic e responde dparadoxicall y t o th e stimulant s amphetamin e an dmethylphenidate . Examinatio n o f th e activit y dat afollowin g administratio n o f methylphenidate 28 ' raise s question s a s t o th e exac t natur e o f

th e paradoxica l response . Bothcontro l an dlead-treate danimal s responde dwithincrease d locomoto r

activit y followin g 4 0 mg/k g o f methylphenidate ; however , th e respons e ofth e lead

treate dmic e wa s markedl y attenuated . Withi n 9 0 t o 12 0 min , animal s wer e belo w thei r predru g level . Thi s tim e cours e i n th e respons e woul db e expecte d i f th e lead-treate danimal s wer e enterin g int o stereotypi c behavio r

( abehaviora l patter n char

acteristicall y see n followin g hig hdose s o f amphetamine-lik e compounds). 29 0 Althoug hth e author s stat e tha t

n o stereotypi c behavio r occurre d i n lead-treate danimals , n o quantitatio n o f thi s behavio r wa s made . Furthermore , thi s stereotypi c behavio r ha s bee n observe din lead-treate dmic e b y othe r investigators. 27 0 Again , th e possibl e contribu

tio n o f earl y undernutritio n t o thes e result s mus t b e considered . Bornschei n e t al. 27 0 foun dthi s paradoxi

ca l lowerin g o f

activit y i n undernourishe dmic e followin g 1 0 mg/k g o f

d-amphetamine , bu t

onl y dur

in g th e secon dhou r

followin g dru g administration . I n th e firs t

hour , activit y showe dth e expecte din

crease , althoug ht o alesse r exten t tha n in controls . Thes e author s postulate dtha t earl y undernutritio n shift s th e dose-respons e curv e t o th e lef t suc htha t animal s give n hig hlevel s o f amphetamin e (1 0 mg/kg ) ente r

int o stereotype dbehavio r soone r tha n controls , whic hprevent s th e occurrenc e an dth e

recordin g o f

locomoto r

activity . Reiter 25 8 examine dth e dose-respons e relationshi p t o amphetamin e in control , undernourished , an d lead-expose drats . H e found , a s di dBornschei n e t al., 27 0 tha t

undernutritio n shifte dth e dose-respons e curv e t o th e left . Lea dtreatment , o n th e othe r hand , shifte dth e dose-respons e curv e t o th e right . Thus , unde r th e appropriat e conditions , lea dexposur e pe r s e ca n b e show n t o produc e a n attenuate drespons e t o amphetamine . Th e occurrenc e o f atru e paradoxi

ca l response , however , i s questionable . Th e lead-induce dattenuate drespons e t o amphetamin e ha s bee n observe dregardles s o f whethe r th e reporte dpredru g activit y level s wer e elevated, 280

- 28 1 normal, 258

- 28 2 o r depressed. 26 4 Th e determinatio n o f

th e exac t

natur e o f

thi s altere d response , i.e. , altere dCN S sensitivit y versu s altere d absorption , distribution , an dmetabolism , require s furthe r study . 11.5.2. 3 LEARNIN GABILIT Y Ther e i s littl e doub t

tha t acute , high-leve l lea dex posur e i n youn g childre n ca n produc e over t manifestation s o f

neurotoxicity. 182

- 20 3 Menta l retar datio n i s a n establishe dsequel ao f lead-induce den cephalopath y in children. 85

- 8 6 Th e exten t an dnatur e o f lead-induce dneurotoxicit y followin g long-ter m low-leve l lea dexposur e durin g th e developmenta l year s i s als o o f

continuin g interest . A s indicate dpre viously , restrospectiv e studie s i n childre n ar e generall y equivoca l an dar e compromise db y seriou s experimenta l desig n limitations , e.g. , unsatisfactor y documentatio n o f

lead-exposur e histor y prio r t o behaviora l testin g an dinappropriat e o r unsatisfacto

r y contro l groups. 29 1 I n a n attemp t

t o overcom e som e of

thes e limita

tions , investigator s hav e turne dt o anima l model s o f chronic , low-leve l exposure . Th e majo r portio n o f thi s wor k

ha s bee n carrie dou t

in rats . Tabl e 11- 7 provide s asummar y ofth e pertinen t studies , includ

in g exposur e conditions , testin g conditions , an d results . I n a n attemp t

t o structur e thi s literatur e an d facilitat e evaluation , th e organizatio n show n i n Tabl e 1 1 - 8 ha s als o bee n developed . I t separate s th e dat aalon g tw o lines : (1 ) task s tha t reportedl y are , o r ar e not , sensitiv e t o change s arisin g fro mth e ex posur e condition s an d(2 ) th e stag e o f learnin g dur

in g whic heffect s are , o r ar e not , demonstrable . Th e acquisitio n colum n indicate s investigation s o f th e rat e a t whic hanimal s formassociation s betwee n stimulu s an dreinforcemen t conditions . Measure s 11-3 4P.7 9



### utilize dt o quantif

y th e proces s are number s o f day s o

f th e quantitativ e natur e o f th e behavio r

afte r th e an dtrial s o r

proble mpresentation s require dt o desire dcriterio n ha s bee n attained . Th e reversal/ex

reac hsome predetermine dlevel of performance . Th e percentag e o

f th e tes t populatio n attainin g th e define dcriterio n per

uni t tim e i s als o acommo n tinctio n column contain s studie s of behavio r ob

serve dfollowin g th e removal o f (extinction ) o r alteratio n o

f (reversal ) th e condition s tha t produc e measure . Th e performanc e colum n include s studie s reinforcement . TABLE 11-7 . PROTOCOL S USE D FO

R TH E STUD

YO F ANIMAL LEARNIN G

Referenc e Brady e t al.» " Brown , D. 27 1

Brown , S . et al." "

Driscol l an d Stegner?" "

Overmann 29 *

Snowdon"9

5

Sobotk a etal. 2 « 3 Specie s

Ra t Ra t

Ra t

Ra t

Ra t

Ra t

Ra t Behaviora l tas l

Apparatu s wate r T-maz e T-maze T-maz e Tmaz e T-maz e Tmaz e T-maz e T-maz e wate r Tmaz e Shuttle bo x Y-maz e Shuttle bo x Shuttle bo x Shuttle bo x E-maz e E-maz e E-maz e 2-compar t men t chambe r 2-compartmen t chambe r Operan t C F maz e C F maz e Shuttle bo x Rewar d

neg . pos . pos . pos . pos . pos . pos . pos . neg . neg . pos . neg . neg . neg . pos . pos . pos . neg . neg . pos . pos . pos . neg . Task " Simult . BD . Succ . B.D . Succ . B.D . Succ . B.D . Succ . B.D . Succ . B.D . Succ . B.D . Succ . B.D . Spatia l discrim . 2-wa y Simult . B.D . 2-wa y 2-wa y 2-wa y Spatia l discrim . Tactil e discrim . Visua l discrim . 1-wa y Passiv e avoi d Tempora l disc . Maze learnin g Maz e learnin g 2-wa y Lea d

Period b PG.G. L L L L(ls t lOd ) L(lastlld ) L(lastlld ) L(lastlld ) Birt h t o da y 1 0 Variou s ( 8 days to 5 weeks ) 5 week s PG.G.L.PW PG,G,L,PW PG,G,L,PW PG,G,L,P W L L t L L L Adul t exposur e andP W L 3-2 1 day s postpartu m exposur e

Level " 50 0 GAV 10 0 W 2 5 GAV ' 35 GAV 3 5 GAV " 7 0 GAV 14 0 GAV 5 IP " 10 0 IP * 10 0 IP " 207 0 DT < 207 0 DT ' 207 0 DT ' 207 0 DT ' 5,16,4 9 GA V 5,16,4 9 GA V 5,16,4 9 GA V 5,16,4 9 GA V * 5,16,4 9 GA V 5,16,4 9 GA V 2.7,4. 4 6. 6 IP " 4. 4 IP « 5.15,4 4 GA V Numbe r Litte r pe rtes t grou p 4 ? 7 7 7 7 7 7 7

7 7 7 7 7 7 7 7 7 7 7 7 1 7 6- 7 Subject s pe rtes t grou p 1 7 6 7 5- 6 5- 6 5- 6 5- 6 7 6 6 8 4 5 1 2 1 2 7 7 7 7 7 7 8-1 0 3 6 28-3 4 Grow1h d

rat e N N N N N N A N 7

7 A A N A N N N N N N A A 7 Bloo d lea d

Pea k 7 7 7 4 6 2 0 1 9 7 28 8 7

7 7 7 7 7 33,17 4 22 6 33,17 4 22 6 33,17 4 22 6 33,17 4 22 6 33,17 4 22 6 33,17 4 22 6 7

7 1 1 2 1 2 3 Mg/d l

Attes t 7 7 7 7 7 7 7 2 3 7

7 7 7 7 7 15,23 , 5 6 7 7 7 7 7 7

7 7 Learnin g performanc e Impaire d Impaire d Impaire d Impaire d N o effect N o effec t Impaire d Impaire d N o effect N o effect Impaire d Improve d Impaire d Improve d N o effec t Impaire d o n reversa l N o effect N o effec t Impaire d N o effec t Impaire d N o effec t Impaire d Impaire d

11-3 5 (continued )P.8 0

TABL E 11- 7 (continued) .

Lea d exposure Numbe r

Referenc e Specie s Apparatu s Rewar d Task " Penod b Litte rSubject s pe rtes t pe r tes t Growt h Level " grou p grou p rat e Bloo d lead , fig/d ! Learnin g Pea k A

t les t performanc e Sobotk a an d Ra

t Cook" 2

Carso n e t al.30i.30 2 an d VanGelde r e t al.so o Shee p

Bowma n an d Monke y Bushnell~4 3 2 - compartmen t chambe r Shuttle box Shuttle box Operan t Slecta« 6 Shapir o etal. 2 " Hasting s etal. 2 "

Winnek e e t al.28 5 Bornschein 29 8 Bornschein 2 ' " Sobotk a etal.28 4 VanGelde r etal.30 0 Ra

t Ra t Ra t

Ra t

Mous e Mous e Do g

Shee p Operan t

Operan t Shoc k gri d Shoc k gri d Operan t Lashle y jumpin g stan d Operan t Operan t Tmaz e Operan t Operan t Operan t C F maz e C F maz e Operan t WGT A neg .

neg . neg . neg . pos . pos . neg . neg . pos . pos . pos . pos . pos .

pos . pos . pos . pos . pos . pos . pos . passiv e avoi d 1-wa y 2-wa y Spatia l discrim . F l schedul e V I 3 0 schedul e Flinc h SEA Succ . B.D . Simult . PD&S D Simult . B.D . Simult . B.D . Simult . R.O . Auditory discrim . F l schedul e F l schedul e Maz e learnin g Maz e learnin g Simult . FD&S D 3-2 1 day s

post partu m

P W(da y 22-57 ) P W (day 90126 )

PG.G. L P W

2-week5 mont h post partu m Adul t exposur e 9 weeks

5 days 1 2 week s pos t partu m G L.P L 5,15,44 " ?

GA V 7

50,30 0 — 100 0 W ' .0 9 • 5 2 — IP « 109 , 54 6 W ' 109 , 54 6 W ' 109 , 54 6 W ' 74 5 OT' — 103,54 6 5 273 0 W ' 109,54 6 7 W ' 1. 4 W ' —

10 0 GA V — 100 0 DT ' — 53 0 DT ' — 2.3,4.5 " — D T 2,4,8,16 " — D T 2,3,4,5 " — D T 0.3,1. 0 — 5- 8

5- 8 5- 8 5- 8 3

1 0 1 0 1 0 1 0 1 5 A 1 4 N 1 0 N 18,61,7 1

18,61,7 1 18,61,7 1 18,61,7 1 9,28,4 0

29,4 2 29,4 2 29,4 2 2 9 7 9 -19 0 8 0 18 0 8 5 N o effec t

N o effec t Impaire d Impaire d reversa l Altere d Altere d N o effec t 5, 9 Les s 5, 9 aggressiv e 5, 9 N o effec t 2 9 Impaire d 29,12 0 Impaire d 2 9 Impaire d reversa l

—Impaire d Impaire d 5 5 6- 8 4 6- 8 4 7

7 7

7

7

— 3

0 1 7 17-2 5 57,8 1 123,16 2 17,2 5 50,8 5 3

0 1 7 91 4

— 9,1 4 50,8 5 N o effec t N o effec t N o effec t N o effec t Impaire d Impaire d reversa l "Succ . B.D . = Successive brightnes s discrimination . Simult . 8.D . = Simultaneou s brightnes s discrimination . 1-wa y = One-wa y avoidance . 2-wa y = Two-wa y avoidance . F D = For m discrimination . S D = Sii e discrimination . Flinc h T = Tail-flinc h test . SE A = Shoc k

elicite d aggression . C F mu e = Close-fiel d male . Operan t = Operan t chamber . WGT A = Wisconsi n Genera l Tes t Apparatus . b PG = Pregestatio n period , externa l exposur e t o dam . G = Gestatio n period , externa l exposur e t o dam . L = Lactatio n period , externa l exposure t o dam . P W - Post weanin g period , externa l exposur e t o pup . C DT = Die t GAV ° Gavag e I P = Intraperitonea l W = Drinkin g wate r % = (forma l A = Altere d "mg/kg/da y 'pp m 

### 11-3 6P.8 1

A revie w ofth e studie s liste din Tabl e 1 1- 7 lead s t o th e followin g genera l critique . Fe w anima l studie s adequatel y simulat e th e lea dexposur e condition s foun din youn g childre n eithe r wit hrespec t

t o th e level s o f exposur e o r

th e timin g o f

the . exposure . Ther e i s ofte n a n inadequat e o r nonexisten t

histor y o f lea dexposur e withrespec t t o bot hth e externa l an dinterna l dose . I n regar dt o th e genera l experi

menta l designs , severa l desig n deficiencie s fre

quentl y occur . Thes e include : (1 ) limite dsampl e siz e o r large r sample s derive dfro mafew litter s —th e latte r permit s geneti c effect s t o hav e an inordinat e influenc e o n th e result s —an d(2 ) inappropriat e ap plicatio n o f

statistica l method s an dconfoundin g o f variables , e.g. , materna l undernutritio n o r neonata l growt hretardation , whic hresult s i n a n inabilit y t o determin e specifi c cause s fo r demonstrate deffects . Th e selectio n o f

behaviora l task s i s ofte n mad e with littl e o r n o apparen t

rational e tha t

woul dai din th e formulatio n an dtestin g o f hypothese s an din

terpretatio n o f

data . Finally , mos t

investigator s d o no t provid e adequat e documentatio n o f th e relativ e sensitivit y o f

th e behaviora l task s bein g use dwhic h coul db e accomplishe dwit hth e us e o f astandar d referenc e compound . Sinc e thi s ha s no t bee n done , failur e t o observ e adisruptio n in tas k acquisitio n o r performanc e coul db e take n t o mea n tha t (1 ) th e tas k i s no t sensitiv e enoug ht o detec t th e defici t

o r (2 ) th e neura l system s whic hmediat e th e behavio r o n tha t tas k ar e no t affecte db y lea da t

th e exposur e level s examined . I n spit e o f

th e extensiv e methodologica l difference s in thes e studies , severa l conclusion s ca n b e draw n fro mth e dat ashow n i n Table s 11- 7 an d 11-8 . TABL E 11-8 . STAG E O F LEARNIN G Treatmen t effect s Presen t

Absen t

> Acquisitio n Brad yetal.292. a Brown304, b Carso n etal.soi. b Driscol l an d Stegner272.a. b Hasting s etal.273 b Overmann 2 94. a Snowdon 295

- b Sobotk a e t al.283. a Winnek e etal.285 b Mille retal.sos. b Bornschei n e t al.298

•* > Carso n e t al.soo. b Hasting s e t al.273. b Overmann 2 9 i a.b Sobotk a e t al. 2

83. a Winnek e etal.285. b Performanc e Shapir o etal. 29 TM Slecta296. b Bornschei n e t al. 298

- b Reversa l 'extinctio n Overmann294.a. b Sobotk a etal.283. a Bornschei n e t al. 298

- 1 " Bowman303. b

Overmann 2 94. a Sobotk a etal. 2 83. a Mille retal.305. b

a Negativ e reinforcer . b Posi t iv e reinforcer . Althoug hlearnin g paradigm s ar e bein g use dt o demonstrat e effect s o f lea do n CN S function , th e presen t dat ad o no t

permi t aclea r distinctio n be

twee n th e effect s o f

lea dexposur e o n cognitiv e func

tio n (learning/memory ) an deffect s o n sensory moto r function , arousal , o r motivation , whic hin tur n ca n produc e performanc e differences . Therefore , som e o f

th e studie s appearin g i n th e col

um n title d"Acquisition " (Tabl e 11-8 ) may , in fact , belon g i n th e "Performance " column . Thi s i s especiall y tru e o f

studie s tha t

repor t larg e grou p difference s o n th e firs t da y o f acquisitio n (cf

. 292 , 299) . Ne w studie s specificall y designe dt o tes t fo r thi s distinctio n mus t

b e conducted . Task s tha t

us e bot hpositiv e an dnegativ e reinfor

cer s appea r t o b e equall y sensitiv e t o disruptio n followin g lea dexposur e (Tabl e 11-8) . Therefore , lea dexposur e doe s no t appea r t o hav e aselectiv e effec t o n aspecifi c motivationa l system . Treatmen t

effect s hav e bee n reporte dbot hb y thos e investigator s usin g manua l testin g procedure s whic hrequir e ahig hdegre e o f experimenter-subjec t interactio n (cf

. 285 , 292 , 304 ) an db y thos e usin g automate doperan t

chamber s wit hminima l experi

menter-subjec t

interactio n (cf

. 283 , 294 , 306) . Thus , report s o f

significan t

treatmen t

effect s canno t

b e ascribe dt o experimente r bias . Th e effect s appea r

t o persis t

beyon dth e immedi

at e exposur e perio dwit hbehaviora l disruptio n 1-3 7P.8 2

demonstrabl e i n animal s wit hnorma l bloo dlea d level s (cf . 283 , 285 , 304 , 306) . Procedure s hav e bee n inadequat e fo r reproducin g qualitativ e an dquantitativ e change s in behavior . Thi s ha s limite dth e abilit y t o tes t hypothese s per tainin g t o th e sit e o f actio n o f

lead-induce d behaviora l changes . I t i s no t ye t clea r whethe r th e observe deffect s ar e direc t effect s o f

lea do n th e developin g nervou s syste mo r whethe r th e effect s ar e indirectl y mediate d throug htreatment-induce dalteration s in materna l behavior , materna l milk , o r on e o f severa l potentia l periphera l targe t

system s in th e neonate . Som e type s o f

learnin g problem s appea r t o b e mor e sensitiv e t o lead-relate ddisruptio n tha n others . Fo r

example , in th e passiv e avoidanc e paradigm , acquisitio n an dextinctio n ar e reportedl y no t sensitive. 282

- 29 4 Simpl e patter n discriminatio n i s als o apparentl y insensitiv e t o lea dexpo sure . 285,294,30 1 Othe r

form s o f

visua l discrimina

tio n suc ha s size 285

- 30 1 an dbrightness 272

- 292

- 304

- 30 6 ap pea r t o b e particularl y sensitive . Th e tw o report s o f altere dsiz e discrimination 285

- 30 1 may in fac t b e specia l case s o f

brightnes s discriminatio n sinc e th e differen t siz e stimul i (whit e patter n o n ablac k back

ground ) als o reflec t

differen t

amount s o f

light . Furthe r testin g wil l b e necessar y t o resolv e thi s issue . Active-avoidanc e task s ar e als o bein g use dsuc cessfull y t o examin e effect s obtaine dfollowin g lea d exposure . Bothone-wa y avoidance 294

- 30 6 an dtwo way , shuttle-avoidanc e tasks 272

- 28 3 reflec t adisrup

tio n i n norma l behavior . Th e on e exceptio n i s a negativ e finding b y Sobotk ae t al. 28 3 usin g aone-wa y avoidanc e task . Thi s negativ e effec t ma y b e relate d t o th e fac t

tha t shoc k wa s terminate dautomaticall y afte r 5 seconds , independen t o f th e animals ' behavior . Thi s i s no t

th e usua l procedure , an dit s effec t canno t b e evaluate dsinc e n o dat awer e pre sente dfo r

thi s particula r

task . Deficit s in tas k

performanc e d o no t

appea r t o b e specie s specifi c sinc e the y ar e reporte dfo r rats, 272

- 283

- 294

- 30 4 mice, 29 8 dogs, 30 5 sheep, 30 ' an d monkeys. 30 3 Furthermore , recen t studie s sugges t

tha t behaviora l alteration s may b e presen t in rat s ex pose dt o lea dfollowin g weaning. 296

- 29 7 Thes e re port s ar e contrar y t o th e generall y hel dopinio n tha t adul t o r post-weanin g rat s ar e insensitiv e t o lea dex posure . 293.295.30

i sinc e th e numbe r

o f reporte d studie s usin g adul t

exposur e protocol s i s extremel y limited , however , i

t i s no t possibl e t o rul e ou t

th e suggestio n tha t

thes e conflictin g dat amerel y reflec t difference s in tas k

sensitivity . Mor e researc husin g adul t exposur e protocol s an dmor e sophisticate d behaviora l testin g paradigm s wil l b e necessar y t o resolv e th e conflict . 11.5.2. 4 EFFECT S O FLEA D O N AGGRESSIV E BEHAVIO R Tw o report s appeare din th e literatur e in 197 3 whic hsuggeste dtha t

lea dexposur e produce da n in

crease daggressiveness . Silbergel dan dGoldberg 26 2 reporte dtha t

mic e expose dt o eithe r 5 o r 1 0 mg/m l o f lea dha da"heightene dfrequenc y o f fightin g a s determine db y th e incidenc e o f bit e frequencie s ob

serve do n litter-mat e male s house dtogether. " Sauerhof f an dMichaelson 27 8 als o referre dt o a n in

crease daggressivenes s in lead-expose drat s durin g th e fourt hwee k

o f development . I n neithe r report , however , wa s ther e a n attemp t t o quantitat e thes e observation s o f

increase daggression . Hasting s e t

al. 30 6 expose dlactatin g rat s t o lea d(0 , 109 , o r 54 5 ppm ) fro mparturitio n t o 2 1 days . Thi s lea dtreatmen t

produce dn o chang e in growt hin th e offspring . Individua l pair s of mal e offsprin g (fro m th e sam e treatmen t

groups ) wer e teste da t

6 0 day s o f ag e fo r shock-elicite daggression . Lead-expose d group s showe dsignificantl y les s aggressiv e behavio r tha n th e contro l group . Ther e wer e n o significan t difference s amon g th e group s in th e flinch/jum p threshold s t o shock . Thi s latte r findin g suggest s tha t th e difference s see n in th e shock-elicite daggressio n wer e no t cause db y difference s in shoc k threshold . Gra y an dReiter 26 1 reporte do n th e aggressiv e behavio r o f mic e expose dt o 5 mg/m l lea dacetat e fro mparturition . Aggressiv e behavio r wa s measure d b y introducin g a n adul t mal e intrude r

int o th e hom e cag e o f a n individua l experimenta l male . Contro l male s wounde dth e intrude r 8 5 time s o n th e averag e durin g a14-hou r

tes t period , wherea s intruder s t o lead-treate dan dpair-fe dmal e cage s ha dmean s o f 3 2 an d35 , respectively . Therefore , th e reduce dag gressiv e behavio r

see n in thes e experiment s canno t b e explaine db y lea dexposur e alone , becaus e simila r reduction s wer e observe din pair-fe dcontrols . Nevertheless , in bot hth e ra t an dth e mous e aquan titativ e examinatio n o f

aggressiv e behavio r

suggest s tha t lea dca n caus e adecreas e rathe r tha n a n in

creas e in aggressiv e behavior . 11.5.2. 5 NEUROCHEMISTR Y Th e effect s o f

in vivo lea dexposur e o n avariet y o f neurochemica l substance s an dprocesse s hav e bee n studie di n th e pas t

severa l year s (se e Tabl e 11-7) . Perhap s mos t

notabl e ar e th e investigation s o f lea d effect s o n bot hputativ e neurotransmitte r system s an do n energ y metabolis min th e centra l nervou s 11-3 8

### system . Muc hofth e work , b y it s nature , ha s require d th e us e o f experimental animal model s fo r broa d screenin g fo

r possibl e effects acros s man y different transmitte r

system s or

fo r testin g specifi c hypothese s o f altere dtransmitte r

functions . Unfortunately , thes e studie s o

n th e neurochemical effects o f leadex posure ar e hindere db

y th e sam e problem s i

n experi

menta l desig n a s thos e discusse di n th e sectio n o

n behavioral studies . Researc ho

n neurotransmitte r

system s ha s con centrate dprimaril y on th e effects o f lea dexposure o n cholinergi c an dmonoaminergi c functions , proba

bl y becaus e o

f th e extensiv e backgroun dliteratur e that exist s on th e basi c neurochemistr y o f thos e transmitter s an dbecaus e o f th e documentatio n ex tan t o n th e neurophysiological andbehaviora l role s playe db y thes e transmitters . Th e approache s employe di

n thes e studie s hav e included : (1 ) biochemical assay s o

f steady-stat e level s o

f transmit

ter substance s i

n brai n tissue; 277



### - 283



### - 288



### - 307 

### " 31 5 

### (2 ) assessmen t o f synthesi s andturnove r

rates; 309



### - 31 5 

### (3 ) measurement

o f th e activity o

f enzyme s responsibl e fo r transmitte r

synthesi s o r

degrada

- t 

### j on; 

### 283,309,3 i 1,313,316-318 (4 ) assessmen t o f transpor t processe s involve di

n synapti c uptake o

f transmitter s or thei r precursors; 308



### - 309



### - 31 6 

### and(5 ) assessment o f synapti c releas e mechanisms 308



### - 309



### - 315



### - 31 6 

### (se e Tabl e 11-9) . TABL E 11-9 . IN

VIVO EFFECT S O F LEA D EXPOSUR E O N NEUROCHEMISTR Y Lea d concentratio n Specie s Exposure Nutritiona l statu s Blood .

Ittlil Brain .

Mil Neurochemica l paramete r Silbergel d an d Goldberg30 8 Mous e

Silbergel d etal.30 9 Mous e

Carrol l etal.3i * Mous e

Brow n et al. 31 8

Goite ran d Michaelson*" ' Ra

t

Ra t

Michaelso n an d Sauerhoff*' * Sauerhoffan d Michaelson" 8 Gran t e t al."' " Ra

t Ra t Ra t 5 mg/m l lea d acetat e i n drinkin g wate rstartin g at parturitio n

5 mg/m l lea d acetat e i n drinkin g wate rstartin g a t parturitio n 2,5,1 0 mg/m l lea d acetat e i n drinkin g wate rstartin g a t parturitio n

7. 5 mg/k g (IP ) fro m birt h t o 1 0 day s of ag e

5% lea d acetat e i n mother' s die t fro m parturitio n t o 1 6 days pos t partum , 4 0 pp m i n drink in g wate r Intubate d wit h 1. 0 mg/day fro m parturitio n t o 1 6 day s pos t partum , 4 0 pp m i n drinkin g wate r Undernourishe d

Undernourishe d

Undernourishe d

Norma l

Undernourishe d 1 ) Hig h affinit ytranspor t of phenylalanine , glycine , leucine , NE , 5HT , GABA , DA , choline , an d tyrosin e 2 ) Steady-stat e AC h NED A 1 ) AC h releas e 2 ) Stead ystat e NE , HVA , VMA 3 ) MA O 4 ) Cholin e transpor t 1)K + -induce d releas e of AC h an d cholin e 2 ) Spontaneou s releas e o f AC h 3 ) Steady-stat e level s o f ACh , cholin e 4 ) CA TCB KACh E ACh E (regiona l brai n analysis )

Steady-stat e NE , D

A 1 ) Decrease d hig h affinit y

transpor t o f dopamin e an d cholin e Increase d hig h affinit y transpor t o f tyrosin e 2 ) Increase d stead ystat e level s of N E 1 ) Decrease d 40 % 2 ) Increase d 27 , 41 , 15 % respectivel y 3 ) Increase d 20 % 4 ) Decrease d 50 % 1 ) Inhibite d K + induce d releas e of cholin e an d AC h 2 ) Increase d spontaneou s AC h releas e 3 ) N o chang e i n stead ystat e level s 4 ) N o chang e N o chang e i n medulla oblongata , corpu s striatum , cerebellum , cerebru m o rhippocampus . Inhibite d i n midbrai n (16% ) Increase d N E at 3 3 day s o f ag e (13%) ; n o chang e i n D

A

5% lea d acetat e i n mother' s die t fro m par turitio n unti l da

y16 , 2 5 pp m i n drinkin g wate r 4 % lea d carbonat e i n mother' s die t fro m par turitio n unti l 1 6 days , 4 0 pp m i n die t 0 , 25, 10 0 o r20 0 mg/kg/da yb

ygavag e o n postnata l day s 3-2 5 Undernourishe d Undernourishe d ? ?

0 = 2 5 = 10 0 = 20 0 = Contro l = 0. 1

4 % = 0.8 8

, 1 6 2 6 4 3 6 3 0.1 5 0.3 8 0.5 1 0.6 8 1 ) Steady-stat e D A 2 ) Steady-stat e 5HT , GABA , an d N E Steady-stat e NE , D

A Steady-stat e NE , D

A (regiona l brai n analysis ) 1 ) Decrease d D A(20% ) 2 ) N o chang e Decrease d D

A(20% )

N o chang e (continued ) 11-3 9P.8 4 •r * •

TABL E 11- 9 (continued) .

Referenc e Hrdina3l 3

Moda k etal.3 n

Sobotka etal." 8 " ShihandHanin3i 5

Cahil l etal." "

Silbergel d an d Chisolm3i 9 Gerbe re t al.31 2 Bhatnagar3i 7

Bul l etal." " Specie s

Ra t

Ra t

Ra t Ra t Ra t

Mous e Mous e Rat (200 - 25 0 g ) Ra t (200 - 40 0 g ) Holtzma n an d Hsu""" 1 Ra

t

Abbreviations : AC h •Acetylcholin e CA T•Cholin e acetyltranferas e ACh E •Acetylcholinesteras e N E - Norepinephrin e D A - Dopamin e 5N T•5-riydroiytrypt a Exposure 0. 2 an d 1. 0 mg/k g I P (lOOg)fo r4 5 days

1 % lea d acetat e i n drinkin g wate rat parturitio n

8-9 1 mg/kg/da yb

yintuba tio n fro m 3-2 1 days o f ag e 4 % lea d carbonat e i n mother' s chowfro m par turitio n t o 2 1 days , 4 0 pp m i n die t 5 , 5 0 pp m i n drinkin g water . 4 0 daypretreat men t of parent s continue d fro m conceptio n throug h adulthoo d 5 mg/m l lea d acetat e i n drinkin g wate rstartin g a t parturitio n 0.1-100 0 mg/ l lea d acetat e i n drinkin g wate rfo ron e yea r 0,1,2 % lea d acetat e fo r7 0 day s 1 ) 6 7 /x M in

vitro lea d chlorid e 2)3,12 , 6 0 mg/Pb/K g tota l dos e ove r2 week

s 4 % lea d carbonat e at 2 week s postpartu m

min e (serotonin ) GAB A •Gamm a aminobutyri c aci d CP K- Cholin e phosphokinas e Nutritiona l statu s 7 Lea d concentratio n

Blood . nW 7 Brai n ste m N E 5H T Under- Contro l = 0 nourishe d

Norma l Under nourishe d Norma l

Undernourishe d ?

•>

— Impaire d growt h i n 6 0 mg/k g grou p Undernourished , reduce d brai n weight s 1% = 24 5

8 7 1 ?

18 0 da y 0 = 5 5 = 6 5 0 = 1 0 7

?

7

— Contro l = 0.0 8 3 = 13. 2 12 = 72. 6 60 = 38 0 7 Brain ,

Hill 7

7

— 7

18 0 day 0 = 1 8 5 = 2 0 5 0 = 2 7 7

7

7

— 0.0 6 0.1 7 0.4 1 1.02 7 Neurochemica l paramete r Cerebrocortico l ACh , ACh E N E - 20-27 % decreas e 5H T- N o chang e 1 ) Steady-stat e AC h 2 ) CA T 3)ACh E

1 ) Steady-stat e NE , DA , 5H T 2)ACh E 1 ) Steady-stat e ACh , cholin e 2 ) AC h turnove r Steady-stat e NE , D

A

Brai n HV Aan d VMA Steady-stat e 5H T Tyrosinas e activit y

K + stimulate d respiratio n of cerebra l slice s K + stimulate d respiratio n o f cerebra l slice s Cerebra l an d cerebella r mitochondria l respiratio n Result s AC h = 32-48 % increas e ACh E - N o significan t chang e 1)Increase d AC h i n dien cephalo n (12% ) 2 ) Increase d i n medulla pons , hippicampu s an d cerebra l corte x(11-12% ) 3 ) Lowe ri n medulla-pans , midbrai n an d dien cephalo n (10-20% ) 1 ) N o chang e 2 ) Decrease d (marginal ) 1 ) N o chang e i n ACh , in crease d cholin e 2 ) Decrease d AC h turnove r (33-51% ) Decrease d D

Aa t 2 8 days of ag e Increase d N E a t 18 0 days of ag e Increase d 3 3 an d 48 % N o chang e N o effec t

Inhibitio n Inhibite d a t 1 2 an d 6 0 mg/k g exposur e leve l Impaire d respiratio n afte r2 week s o f treatmen t

11-4 0Severa l studie s utilizin g hig hlevel s o f lea dex posur e hav e reporte dinhibitio n o f cholinergi c func

tion . I n aserie s o f

experiment s o n th e mouse , Silbergel de t

al. 308

- 30 9 an dCarrol l e t al. 31 6 reporte d decrease dpotassium-induce dreleas e o f acetylcholin e (ACh ) an ddecrease dhigh-affinit y transpor t o f choline . Unfortunately , n o contro l fo r growt hretardatio n wa s provide din thes e experi

ment s an drelativel y hig hexterna l exposure s t o lea d wer e require dt o produc e th e effect . Thi s wa s als o tru e i n th e ra t

studie s reporte db y Moda k e t al. 31 1 an dShi han dHanin. 31 5 A t lowe r level s o f

externa l exposure , wit hn o accompanyin g growt hretarda

tion , n o consisten t

effect s o n cholinergi c functio n hav e bee n reporte d(cf . 28 3 an d318) . Thus , if im

paire dcholinergi c functio n durin g in vivo lea dex posur e i s als o foun din th e absenc e o f undernutri

tion , and/o r

growt hretardation , whic hi s probabl e in vie w ofth e in vivo wor k

reporte dlate r

i n thi s section , the n it s relevanc e t o behaviora l effect s see n a t lowe r exposur e level s will nee dexamination . Th e effect s o f

lea dexposur e o n catecholamin e functio n hav e als o bee n extensivel y studied . Find

ings hav e bee n reporte do f increase dsteady-stat e level s o f norepinephrine, 277

- 307

- 30 8 increase dactivit y o f monamin e oxidas e (MAO), 30 9 increase dsynap tosoma l transpor t

o f th e precurso r

tyrosine, 30 8 an d increase damount s o f

th e norepinephrin e metabolite , vanilly l mandeli c acid , an dhomovanilli c aci di n th e brain. 31 9 I n studie s o n steady-stat e level s o f norepinephrine , change s hav e bee n reporte deithe r i n th e absenc e o f

undernutrition 22 7 o r

whe n value s hav e bee n compare dt o pair-fe dcontrols. 30 7 How

ever , inconsistencie s withi n agive n laborator y (cf . 27 8 vs . 307) , absenc e o f simila r finding s in differen t laboratorie s (cf

. 28 3 an d310) , an dfinding s o f de

crease dsteady-stat e levels 31 3 mak e an y conclusion s regardin g lead-induce dchange s in noradrenergi c system s equivocal . Thi s uncertaint y i s als o foun din th e report s o n dopamin e change s followin g lea dex posur e (cf

. 277 , 278 , 31 4 vs . 283 , 307 , 310) . Huma n studie s attemptin g t o relat e subclinica l lea dexposure s t o sign s o f altere dbrai n monoamin e functio n hav e bee n initiate dutilizin g urinar y level s o f monoamin e neurotransmitte r metabolite s a s in

dice s o f CN S monoamin e turnove r rates . Althoug h initia l studie s o n catecholamin e excretio n hav e sug geste dalea deffect , a happende dnot e b y Silbergel d an dChisholm 31 9 indicate ddifficult y i n findin g on e o f th e earlie r

reporte deffect s i n subsequen t studies . Thi s clinica l stud y agai n emphasize s som e o f th e problem s an duncertaintie s tha t hav e bese t

in

vestigation s o f

low-leve l toxicity . Also , a s indicate d b y Wende r e t al., 32 1 urinar y metabolite s reflec t pri

maril y periphera l nervou s syste mactivity . I n anothe r study 32 2 altere dlevel s o f 5-hydroxyindol e aceti c aci d(5-HIAA ) wer e reporte din th e urin e o f occupationall y lead-expose dbatter y factor y workers , suggestin g possibl e lea deffect s o n serotoni n (5-hydroxytryptamine ) systems . N o paralle l supportiv e evidenc e fro manima l studie s ha s bee n advance dfo r

suc ha n effect , however , an di n fac t mos t report s clai mnegativ e finding s fo r an y typ e o f measurement s o f

brai n serotoni n func

tion . 283,308,312-314 Th e reason s fo r

th e inconsistencie s o f lead-in

duce dchange s in monaminergi c an dcholinergi c function s ma y b e th e resul t i n par t o f interlaborator y difference s in dosin g regimen s an dothe r variation s in experimenta l protocol . On e not e o f caution , however , i s appropriat e her e in tha t highl y variabl e result s ar e see n withi n differen t laboratories , eve n withth e sam e exposur e regimens , assa y procedures , etc. , fro mexperimen t

t o experiment . Thi s migh t sug ges t tha t som e subpopulation s o f rat s o r mic e migh t b e resistan t

t o lea deffect s o n monoamin e transmit

ter s wherea s other s ar e mor e vulnerable , possibl y becaus e o f

geneti c factors , subtl e variation s i n diet , etc . Mor e carefull y controlle dstudie s i n th e futur e tha t explicit y manipulat e suc hvariable s (genetics , nutrition , etc. ) ma y revea l lea deffect s eve n a t lo w exposur e levels , give n th e righ t circumstance s o r populatio n segmen t

tested . Finally , th e recen t

repor t o f Nathanso n an d Bloom 32 3 indicate dtha t in vitro lea dexposur e in

hibit s adeny l cyclas e activit y (I 5 0 = 2. 4 fiM). Thi s enzym e i s responsibl e fo r th e synthesi s o f

cycli c adenosin e 3',5'-monophosphat e (c-AMP ) whic hha s bee n show n t o pla y an importan t rol e in th e mechan

is mo f actio n o f

anumbe r

o f hormones , includin g neurotransmitters . Th e effect s o f lea dexposur e o n adeny l cyclas e an dth e resultan t effect s o n neuro transmitte r

system s warran t

furthe r investigation . Severa l recen t

report s hav e deal t

wit hth e effect s p f lea dexposur e o n brain-energ y metabolism . Bul l e t al. 25 3 reporte dtha t

bot hin vivo an din vitro lea d exposur e inhibite dpotassium-stimulate drespira

tion . O f interes t wa s th e findin g tha t

lowe r brai n level s o f lea d(approximatel y 1 /30th ) wer e require d t o inhibi t respiratio n in vivo tha n in vitro. Also , thes e result s wer e see n in animal s showin g norma l growt h (1 2 mg/k g group) . Simila r finding s o f

inhibite d respiratio n usin g isolate dmitochondri awer e re porte db y Holtzma n an dHsu 32 0 an db y Brierley. 32 4 I n contras t

t o th e genera l lac k

o f consisten t

effect s o n steady-stat e level s o f cholinergi c substance s an d 11-4 1P.8 6

associate denzymes , consisten t evidenc e fo r

effect s o f lea do n cholinergi c synapti c uptak e an dreleas e mechanism s hav e bee n reported . Mor e specifically , lea dresemble s othe r divalen t cation s i n tha t

it appear s t o interfer e withchemicall y mediate dsynapti c transmissio n a s demonstrate db y studie s o f

periphera l neura l functions . Kostia l an d Vouk 32 5 reporte dtha t

in vitro perfusio n o f

th e ca t superio r cervica l ganglio n wit h4. 8 fiM lea dnitrat e depresse do r

blocke dnerv e transmission . Contrac

tio n o f th e nictitatin g membran e durin g acetylcholin e perfusio n wa s unaltered . Also , perfu

sio n o f th e ganglio n wit hexces s calciu mrestore d acetylcholin e releas e an dthu s reverse dth e lea d blockade . Fro mthes e finding s Kostia l an dVou k conclude dtha t

lea ddepresse dsynapti c transmissio n b y impairin g acetylcholin e releas e fro mth e pre synapti c terminals . Manali s an dCooper 3 2 6 an dCoope r an d Manalis 32 7 showe dtha t lea dca n influenc e bot hpre an dpostsynapti c events . Usin g th e fro g (Rana ippiens) sciatic-nerve/sartorius-muscl e preparatio n in vitro, the y demonstrate dtha t th e principa l effec t

o f lea dwa s o n presynapti c transmitte r release , althoug hlea dha daweak , curare-lik e effec t o n th e postsynapti c respons e t o applie dacetylcholine . The y confirme dth e finding s o f Kostia l an dVouk 32 5 tha t lea ddepresse s th e phasi c releas e o f transmitte r evoke db y nerv e stimulation . The y furthe r observe d tha t lea dincrease s spontaneou s releas e o f acetylcholin e a s evidence db y increase dminiatur e end-plat e potential s (MEPP's) . Thes e MEPP' s represen t th e respons e ofth e postsynapti c membran e t o release dacetylcholin e in quantitie s tha t ar e in

sufficien t t o depolariz e th e membran e t o threshol d levels . I n asubsequen t experimen t

Kobe r an d Cooper 32 8 demonstrate dtha t i n th e frog , lea dblock s synapti c transmissio n i n th e sympatheti c ganglio n b y competitiv e antagonis mo f spike-evoke dentr y o f calciu mint o th e presynapti c nerv e terminal s wit ha resultan t reductio n in acetylcholin e release . Experiment s b y Silbergel de t al. 329

- 33 0 indicate da simila r blockad e o f

transmitte r

releas e b y lea di n th e rat . Furthermore , the y reporte dareduce dforc e o f contractio n i n the . phrenic-nerve/diaphrag mpre paratio n fro mmic e expose dt o lea dfro mbirt h throug h6 0 day s o f

age . Th e nerve-muscl e prepara tio n fro mthes e lead-expose danimal s showe da reductio n i n forc e o f

contractio n wit hnerv e stimula

tion . Also , areduce dforc e o f contractio n wa s re porte dupo n direc t

stimulatio n o f

th e muscle . Thi s observatio n agree s wit hth e wea k postsynapti c effect s o f lea dreporte db y Manali s an dCooper; 32 6 bu t unfortunately , n o dat awer e presente db y Silbergel de t

al. 329

- 33 0 o n th e muscl e contractio n followin g electrica l stimulation , s o th e relativ e im

portanc e o f

thi s findin g canno t

b e evaluated . Finally , Coope r

an dSteinberg 33 1 demonstrate dtha t lea di s als o capabl e o f

blockin g neura l transmissio n a t th e adrenergi c synapse . The y measure dth e con tractio n forc e o f

th e rabbi t

saphenou s arter y follow

in g stimulatio n o f

th e sympatheti c nerv e endings . Again , th e result s indicate dtha t lea dblock s muscl e contractio n b y an effec t o n th e nerv e terminal s rathe r tha n a n effec t

o n th e muscle . Sinc e th e respons e recovere dwhe n calciu mconcentratio n wa s increase di n th e bathin g solution , it wa s conclude d tha t lea ddoe s no t

deplet e transmitte r

store s in th e nerv e terminal s bu t mor e likel y block s norepinephrin e release . I n summary , in vitro experiment s hav e demon

strate dtha t

lea dinterfere s withsynapti c transmis

sio n i n th e periphera l nervou s system . Thi s effec t ap pear s t o b e relate dt o acompetitiv e inhibitio n o f calcium-mediated , evoke dreleas e o f th e neurotransmitters . Further , lea dwa s show n t o in

creas e th e spontaneou s releas e o f transmitte r

fro m som e synapses . Th e effect s o f

lea do n synapse s withi n th e CN S hav e no t bee n extensivel y studied . Carrol l e t al., 31 6 however , reporte dadecreas e i n potassium-induce d releas e o f

bot hcholin e an dacetylcholin e fro mcorti

ca l mince s o f

mic e chronicall y expose dt o lead . Thes e change s in acetylcholin e metabolis msugges t that , a s i s th e cas e o f

th e periphera l nervou s system , th e centra l cholinergi c functio n ma y b e depresse db y lead . Thi s i s furthe r

supporte db y arepor t o f Shi h an dHanin 31 5 tha t

lea dexposur e decrease din vivo acetylcholin e turnove r

rat e i n cortex , hippocampus , midbrain , an dstriatu m(35 , 54 , 51 , an d3 3 percen t decreases , respectively ) in ra t brai n afte r

neonata l lea dexposures . Alon g withth e in vitro findings , thi s provide s additiona l evidenc e supportiv e o f lead-in

duce ddysfunction s o f

cholinergi c synapti c uptak e an dreleas e mechanisms . Unfortunately , thes e result s an dman y fro mth e abov e periphera l functio n studie s wer e obtaine da t rathe r hig hexposur e level s an dmos t

wer e performe do n undernourishe do r growth-retarde danimals . On e fina l not e concern s th e relationshi p betwee n level s o f lea di n bloo dan dbrain . Severa l studie s o n rodent s hav e reporte dsimultaneou s lea dvalue s fo r bloo dan dbrai n resultin g fro mlea dexposure s o f variou s durations . Bornschei n e t al. 27 0 expose dmic e t o 5 mg/m l lea dacetat e startin g a t parturition . Brain/bloo dratio s showe dastead y increas e fro m2 0 11-4 2t o 10 0 day s o f age . Ratio s o f

1.05 , 2.55 , an d4.0 8 wer e reporte dfo r

mic e at 20 , 40 , an d10 0 day s o f age , respectively . Thi s increas e in th e brain/bloo d ratio s resulte dfro mbot hastead y increas e in brai n lea dlevel s (increasin g fro m20 0 fig %a t 2 0 day s o f ag e t o 58 4 /ug % at

10 0 day s o f

age ) an dadecreas e in bloo dlea dlevel s (decreasin g fro m19 0 pp ma t 2 0 day s t o 14 3 pp ma t

10 0 days) . Cahil l e t al. 27 7 reporte dbloo dan dbrai n level s o f lea di n rat s expose dfro mconceptio n t o eithe r 0 , 5 , o r 5 0 pp mlea din th e drinkin g water . A t parturition , brain/bloo dratio s o f

offsprin g wer e 0.9 1 an d0. 5 fo r exposur e level s o f

5 an d5 0 ppm , respectively . A t 18 0 day s o f

age , thes e ratio s wer e 3. 3 an d2.7 , respectively . A rati o o f

approximatel y 1 wa s als o re porte db y Gran t

e t al. 31 0 in 30-day-ol drat s expose d t o variou s level s o f

lea dfro m3 t o 2 5 day s o f age . Thes e dat aar e consisten t withth e result s o f Bornschei n e t

al. 27 0 an dindicat e tha t initiall y brain/bloo dratio s ar e approximatel y unit y bu t tha t withcontinue dexposur e th e ratio s steadil y increase . 11.5.2. 6 SUMMAR Y AN D CONCLUSION S Dat aobtaine din laborator y animals , suc ha s tha t reporte di n th e ra t

b y Pentsche w an dGarro, 5 2 indi

cat e tha t encephalopath y i s produce db y high-leve l perinata l exposur e t o lead . Thi s encephalopath y oc cur s t o varyin g degree s i n differen t specie s an di s characterize db y th e relativ e involvemen t o f neurona l degeneratio n an dvasculopathy . I t seem s clea r

tha t wit hregar dt o CN S toxicit y th e developin g organis mrepresent s th e populatio n at greates t risk . Whethe r

thi s increase dris k

i s at tributabl e t o agreate r sensitivit y o r

t o agreate r susceptibilit y o f

th e developin g organis mwil l re quir e furthe r

testing . Tha t

is , wit hagive n externa l exposure , th e CN S o f th e developin g organis m reache s ahighe r

concentratio n o f

lea dan di s therefor e mor e susceptibl e t o poisoning . Whethe r th e threshol dfo r

agive n effec t

o f lea di s lowe r

i n th e immatur e nervou s syste mversu s th e adul t wil l nee d t o b e determined . Ther e i s als o goo devidenc e tha t perinata l ex posur e t o lea deve n a t

moderat e exposur e level s will produc e delay s in bot hneurologica l an dsexua l development . Becaus e thes e effect s hav e bee n dem

onstrate dt o occu r

in th e absenc e o f

eithe r under

nutritio n o r

growt hretardation , it ha s bee n sug geste dtha t

the y represen t

direc t effect s o f

lea di n th e respectiv e orga n systems . I n th e anima l studies , locomoto r activit y ha s bee n th e mos t commonl y use dbehaviora l inde x o f lea d toxicity . Th e dat areviewe dher e sugges t tha t perinata l exposur e t o lea dproduce s a n increas e i n

th e animal' s behaviora l reactivity . Ifth e tes t condi

tion s ar e appropriate , thi s increase dreactivit y wil l b e manifeste da s increase dlocomoto r activity , althoug hsom e tex t

situation s will sho w reduce dac tivity . Therefore , th e altere dactivit y level s pe r s e ar e merel y reflectiv e of amor e basi c nervou s syste m dysfunction . Clos e scrutin y o f th e availabl e dat a woul dals o sugges t

tha t altere dlocomoto r

activit y in youn g animal s occur s onl y at moderatel y hig hex posur e levels . A compariso n o f th e dat ao f

Sobotk a an dCook 28 2 an dOvermann 27 5 ar e o f interes t i n thi s regar d(se e Tabl e 11-4) . Usin g gastri c intubation , Overman n reporte dhyperactivit y in youn g rat s whos e 21-da y bloo dlea dlevel s wer e 22 6 figldl. Sobotk aan dCook , usin g asimila r exposur e regi

men , foun dnorma l activit y level s wit h22-da y bloo d lea dlevel s o f

7 1 figldl. I t

appears , therefore , tha t thi s earl y chang e in reactivit y occur s at fairl y hig h bloo dlea dlevels . I t

ma y be , then , tha t

th e change s in activit y currentl y reporte din laborator y animal s ar e mor e representativ e o f apost-encephalopathi c hyperactivit y tha n o f

subclinica l effect s a s ha s bee n suggested . O n th e othe r

hand , th e reactivit y change s reporte d in olde r animal s withlifetim e exposur e occu r a t muc hlowe r

bloo dlevel s (cf

. 264 , 277 , an d285) . Finally , report s o n th e effect s o f lea dexposur e o n th e acquisitio n and/o r performanc e o f

operan t response s indicat e tha t

perinata l exposur e t o moder

at e an dlo w level s o f

lea dma y disrup t

thi s behavior . Thus , externa l exposure s tha t resul t in bloo dlea d level s rangin g fro m3 0 t o 8 0 figldl hav e bee n re porte dt o disrup t

cognitiv e functio n (se e Tabl e 11-5) . A s i s tru e withth e clinica l data , thi s are are quire s furthe r

investigation . I t ha s bee n repeatedl y indicate dtha t seriou s methodologica l problem s exis t i n th e anima l literatur e whic hmak e i t difficul t t o interpre t

man y of'th e availabl e data . Futur e researc hin thi s are a woul dbenefi t

fro mmor e tightl y controlle dexperi

ment s including : 1 . Bette r documentatio n o f

interna l exposure , no t onl y withrespec t

t o lea dlevel s bu t

als o withrespec t

t o correlativ e indice s o f lea dtox icity , e.g. , ALAD , protoporphyrin , etc . 2 . Th e us e o f

exposur e protocol s tha t d o no t pro duc e confoundin g variable s suc ha s under

nutrition , difference s in bot hlitte r siz e an d numbe r o f litter s pe r

treatmen t

group , etc . 3 . Validatio n o f

behaviora l test s usin g bot h positiv e contro l substance s an dcros s corre 11-4 3P.8 8

latio n withothe r

physiologica l indices . Thi s woul dinclud e researc haime dat mor e closel y definin g bot hth e relativ e sensitivit y o f th e CN S compare dt o othe r orga n system s a s wel l a s th e contributio n o f

othe r indirec t action s o f lea do n th e resultin g behaviora l changes . 

### 11. 6 EFFEC T O F LEA D O NTH E RENA L SYSTE M 11.6. 1 Acut e Effect s Mor e tha n 6 0 year s ag o an Englis htoxicologist , Thoma s Oliver, 33 2 distinguishe dacut e effect s o f lea d o n th e kidne y fro mlead-induce dchroni c nephropa

thy . Acut e rena l effect s o f lea dar e see n in person s dyin g o f acut e lea dpoisonin g o r suffering fro mlead

induce danemi aand/o r encephalopath y an dar e usuall y restricte dt o nonspecifi c degenerativ e change s i n rena l tubula r linin g cells , usuall y cloud y swelling , an dsom e degre e o f cellula r necrosis . Cell s o f th e proxima l convolute dtubule s ar e mos t severel y affected . A s lon g ag o a s 1928 , Pejie 33 3 emphasize dtha t

th e degenerativ e change s i n prox ima l tubules , rathe r

tha n th e vascula r

change s ofte n referre dt o in earlie r

studies , ar e primar y evidenc e o f injur y t o th e kidne y in lea dpoisoning . Man y sub

sequen t studie s hav e show n a t

leas t thre e pathologi

ca l alteration s i n th e rena l tubul e withonse t durin g th e earl y o r

th e acut e phas e o f

lea dintoxicatio n in th e kidney . Thes e includ e th e formatio n o f inclusio n bodie s i n nucle i o f

proxima l tubula r

linin g cell s an d th e developmen t

o f functiona l a s wel l a s ultrastruc

tura l change s in rena l tubula r mitochondria . Dysfunctio n o f

proxima l rena l tubule s (Fanconi' s syndrome ) i s manifeste db y aminoaciduria , glycosuria , an dhyperphosphaturia , an dwa s firs t note di n acut e lea dpoisonin g b y Wilso n an d coworker s i n 1953. 33 4 Plasm aamin o acid s wer e nor mal , whic hsuggeste dtha t th e aminoaciduri aan d othe r functiona l abnormalitie s wer e o f rena l origin . Subsequently , aminoaciduri ain childre n withacut e lea dpoisonin g wa s observe db y Marsde n an d Wilson 33 5 i n England , an dChisholm 85

- 8 6 foun dtha t 9 o f 2 3 childre n wit hlea dencephalopath y ha d aminoaciduria , glycosuria , an dhypophosphatemia . Aminoaciduri awa s see n mor e consistentl y i n Chisolm' s studie s tha n th e othe r tw o manifestation s o f tubula r damage . Thus , th e amin o aci dtranspor t syste mi s probabl y mor e sensitiv e t o th e toxi c action s o f lea dtha n th e transpor t system s fo r

glucos e an d phosphate . Th e aminoaciduri awa s generalize di n tha t th e amin o acid s excrete din greates t amount s wer e thos e normall y presen t i n urine . Th e conditio n wa s relate dt o severit y o f clinica l toxicit y an dwa s mos t marke din childre n withencephalopathy . Th e aminoaciduri adisappear s afte r treatmen t

wit h chelatin g agent s an dclinica l remissio n o f othe r symptom s o f

lea dtoxicity. 8 5 Thi s i s a n importan t ob

servatio n relativ e t o th e long-ter mo r chroni c effect s o f lea do n th e kidney . I n agrou p o f

childre n withsligh t

lead-relate d neurologica l signs , generalize daminoaciduri awa s foun din 8 o f

4 3 childre n withbloo dlea dlevel s o f 4 0 t o 12 0 /ig/dl. 9 9 I t shoul db e note dtha t th e childre n reporte dt o hav e aminoaciduri ai n th e stud y o f Pueschel 9 9 wer e no t

specificall y identifie da s t o thei r lea dexposure . Thus , it i s no t possibl e t o stat e wha t leve l o f lea dexposur e withi n th e bloo dlea d rang e o f 4 0 t o 12 0 ug/d l wa s associate dwithth e effects . A simila r

rena l tubula r

syndrom e ha s bee n reporte dt o occu r

in industriall y expose dadults. 33 6 11.6. 2 Chroni cEffect s Ther e i s convincin g evidenc e in th e literatur e tha t prolonge dlea dexposur e i n humans 33 7 ca n resul t i n chroni c lea dnephropathy . Crame r e t al. 33 7 i n 197 4 reporte do n agrou p o f

7 lead-expose dworker s wh o ha dbee n expose du p t o 2 0 years . Aminoaciduri awa s no t found , an dinuli n clearanc e an drena l bloo dflo w wer e als o reporte dnormal . Th e averag e bloo dlea d leve l wa s 10 0 ug/dl , th e minimu mwa s 7 1 ug/dl , an d al l ha dstrikingl y hig hurinar y AL A excretion . Som e wit hver y lon g exposure s wer e reporte dt o hav e in

terstitia l an dperitubula r fibrosis , determine db y rena l biopsy . Thi s pathologica l findin g i s commonl y referre dt o a s chroni c lea dnephropathy , whic hi s characterize db y slo w developmen t o f contracte d kidney s withpronounce darterioscleroti c changes , fibrosis , glomerula r

atrophy , an dhyalin e degenera

tio n o f thes e vessels . Thi s i s aprogressiv e disease , sometime s resultin g in rena l failure . I t seem s t o oc cu r sporadically , primaril y in industriall y expose d worker s an din olde r

adult s wh o hav e bee n diag

nose da s havin g lea dpoisonin g earl y in life . Ther e i s als o som e evidenc e tha t it occur s i n long-tim e drinker s o f

lead-contaminate dwhiskey , a s reporte d b y Morri s e t

al. 33 8 i n th e case s o f

1 6 adult s treate d ove r a10-yea r

period . Thi s stud y reporte dlea d poisonin g manifeste db y th e sam e symptom s foun d in children . Th e mos t

specifi c pathologica l chang e reporte dwa s th e presenc e o f larg e number s o f

acid

fas t intranuclea r

inclusion s withi n th e cell s o f th e kidne y tubule s an dliver . Bal l an dJorenson 33 9 re porte dahig hfrequenc y o f saturnin e gou t

resultin g fro mth e consumptio n o f lead-contaminate d whiskey , convincingl y demonstratin g reduce drena l uri c aci dclearanc e associate dwit hplumbism . 11-4 4I n aserie s o f 10 2 case s o f

lea dpoisonin g studie d b y Lili s e t

al.', 34 0 1 8 case s o f

clinicall y verifie d chroni c nephropath y wer e found . Fo r th e whol e series , th e mea n bloo dlea dleve l wa s approximatel y 8 0 ug/dl , wit harang e o f 4 2 t o 14 1 ug/dl . Nephropath y wa s mor e commo n amon g patient s wh o ha dbee n expose dt o lea dfo r mor e tha n 1 0 year s tha n amon g thos e wh o ha dbee n expose dfo r les s tha n 1 0 years . I n bot hstudies , reduce dure a clearanc e precede dreduce dcreatinin e clearance . I n th e Danilovi c study, 34 1 7 o f 2 3 case s ha dbloo d lea dlevel s o f

abou t 10 0 t o 20 0 ug/dl . I n th e studie s o f Albahar y e t

al., 34 2 bloo dlea dlevel s wer e no t re porte dbu t

exposur e level s mus t

hav e bee n quit e hig h becaus e th e mea n AL A excretio n wa s abou t 3 7 mg/2 4 h r fo r 2 9 workers . Thes e studie s indicat e tha t th e natur e o f

th e effec t

i s glomerulovascular , with reductio n i n clearanc e o f ure aand , in mor e protracte dexposures , als o o f endogenou s creatinine . Also , reduce dclearanc e o f uri c aci dwa s observe din th e stud y o f

Albahar y e t

al. 34 2 I n th e recentl y reporte dstudie s o f Wedee n e t al., 34 3 eigh t

subject s suspecte do f

excessiv e occupa tiona l exposur e wer e give n detaile dexamination s fo r rena l function . Fou r

o f th e subject s showe dsign s o f abnorma l rena l function . I n on e subjec t with asymptomati c rena l failure , chelatio n therap y in

crease dth e glomerula r filtratio n rate , th e p-amin o hippurat e (PAH ) extraction , an dth e maxima l PA H excretio n rate , an dimprove dth e proxima l tubul e ultrastructure , despit e decrease drena l plasm aflow . Thre e ofth e subject s showe dproxima l tubul e abnor

malitie s vi abiopsy . I n eigh t subjects , lead-induce d nephropath y wa s establishe db y exclusion . Th e bloo dlea dvalue s ofth e individual s range dfro m4 8 ug/dl , fo r

th e subjec t

havin g asymptomati c rena l failure , t o 9 8 ug/dl . Th e lea dlevel s ofth e othe r tw o subject s in th e preclinica l rena l dysfunctio n categor y wer e 5 1 an d6 6 ug/dl . Al l subject s showe dglomeru

la r filtratio n rate s o f

les s tha n 8 7 ml/min/1.73m 2

. Th e author s sugges t

o n th e basi s ofthes e studie s tha t lea dnephropath y may b e an importan t occupationa l hazar din th e U.S . lea dindustry . A serie s o f

report s fro mQueensland , Australia, 34 4 point s t o astron g associatio n betwee n sever e lea d poisonin g i n childhoo dincludin g centra l nervou s syste msymptom s an dchroni c nephriti s in earl y adulthood . Henderson 34 5 followe du p 40 1 childre n wh o ha dbee n diagnose da s havin g lea dpoisonin g in Brisban e betwee n 191 5 an d1935 . Ofthes e 40 1 sub

jects , 16 5 ha ddied , 10 8 fro mnephriti s o r hyperten

sion . Thi s i s greatl y in exces s o f expectation . Infor

matio n wa s obtaine dfro m10 1 ofth e 18 7 survivors , an d1 7 o f thes e ha dhypertensio n and/o r albuminuria . I n amor e recen t study , Emmerson 34 6 presente dacriterio n fo r implicatin g lea da s an etiologica l facto r

i n suc hpatients : th e patient s shoul dhav e a n excessiv e urinar y excretio n o f lea d followin g administratio n o f calciu mEDTA . I n hi s study , 3 2 patient s wit hchroni c rena l diseas e at tributabl e t o lea dpoisonin g ha dsimilarl y elevate d excretio n o f

lead . Th e presenc e o f intranuclea r

in

clusio n bodie s i s ver y helpfu l i n establishin g arela

tionshi p betwee n rena l lesion s an dlea dtoxicity , bu t inclusio n bodie s ar e no t alway s presen t

in person s withchroni c lea dnephropathy . Attempt s t o confir mth e relationshi p betwee n childhoo dlea dintoxicatio n an dchroni c nephropa

thy hav e no t

bee n successfu l i

n a t leas t tw o studie s in th e Unite dStates . Tepper 9 0 foun dn o evidenc e o f chroni c rena l diseas e in 4 2 person s withawell-docu

mente dhistor y o f

childhoo dplumbis m2 0 t o 3 5 year s earlie r

a t th e Bosto n Children' s Hospital . Likewise , Chisolm 34 7 foun dn o evidenc e o f rena l dis

eas e in 6 2 adolescent s know n t o hav e ha dlea dintox

icatio n 1 1 t o 1 6 year s earlier . A n importan t distinc

tio n betwee n th e Australia n grou p an dpatient s in th e Unite dState s wa s tha t non e o f

Chisholm's 34 7 subject s showe devidenc e o f increase dresidua l bod y lea dburde n followin g th e EDT A mobilizatio n test . Thi s differenc e ha s suggeste dt o Chishol mtha t lea d toxicit y i n th e Australia n childre n mus t hav e bee n o f adifferen t

type , withamor e protracte dcours e tha n tha t experience dby th e America n children . Mos t childre n in th e Unite dState s wh o suffer fro mlea d toxicit y d o s o earl y i

n childhood , betwee n th e age s o f 1 an d4 , th e sourc e usuall y bein g ora l ingestio n o f fleck s o f wal l pain t

an dplaste r

containin g lead . 11. 7 REPRODUCTIO N AN D DEVELOPMEN T A s reviewe dthu s fa

r in th e presen t

chapter , th e ad

vers e effect s o f

lea do n th e hematopoietic , nervous , an drena l system s hav e bee n wel l documente dacros s awid e rang e o f

exposur e level s an drepresen t atria d o f symptom s classicall y associate dwithlea dpoison

ing . Extensiv e evidenc e fo r advers e effect s o f

lea do n reproductio n an ddevelopmen t ha s als o bee n ac cumulatin g in th e literatur e fo r man y year s an dha s becom e amatte r

o f increasin g medica l concern . Dat afro mbot hhuma n an danima l studie s indicat e tha t lea dexert s gametotoxic , embryotoxic , and , possibly , teratogeni c effect s tha t impac t o n th e pre an dpostnata l surviva l an ddevelopmen t ofth e fetu s an dnewborn , respectively . I n addition , it appear s tha t th e viabilit y an ddevelopmen t ofth e fetu s ma y als o b e markedl y affecte db y lea dindirectl y vi aad

1 1 -4 5P.9 0

vers e effect s o n variou s healt hparameters , e.g. , nutritiona l stat e o r

bloo dchemistry , ofth e expectan t mother . Th e vulnerabilit y o f th e fetu s t o suc hlea d effect s whil e in utero ha s contribute dt o concer n tha t pregnan t wome n may b e aspecia l grou p a t ris k fo r lea dpoisoning . Certai n informatio n o n advers e lea d effect s o n mal e reproductiv e functions , i t shoul d als o b e noted , ha s le dt o additiona l concer n regard

in g th e impac t

o f lea do n men . 11.7. 1 Huma n Studie s Dat asuggestin g tha t

lea dexert s advers e effect s o n huma n reproductiv e function s hav e existe din th e literatur e sinc e befor e th e tur n o f th e century . Fo r example , Legge, 34 8 i n summarizin g th e report s o f 1 1 Englis hfactor y inspector s in 1897 , foun dtha t o f 21 2 pregnancie s i n 7 7 femal e lea dworker s onl y 6 1 livin g childre n wer e produced . Fiftee n worker s ha dneve r becom e pregnant . Ther e wer e 2 1 stillborns , miscar

riage s occurre d9 0 times , and , o f 10 1 childre n born , 4 0 die di n th e firs t

year . Legg e als o note dtha t whe n pregnan t animal s wer e fe dlea dthe y alway s aborted . H e conclude dtha t

materna l exposur e t o lea d resulte din adirec t

actio n ofth e elemen t

o n th e fetus . I n 1911 , Oliver 18 0 publishe dstatistic s i n Britai n o n th e effec t

o f lea do n pregnanc y (Tabl e 11-10 ) whic hshowe dtha t

th e miscarriag e rat e wa s elevate d amon g wome n employe din industrie s in whic hthe y wer e expose dt o lead .

TABL E 11-10 . STATISTIC S O N TH E EFFEC T O F LEA D O N PREGNANCY" "

Sampl e Housewive s Femal e worker s (mil l work ) Female s expose d to lea d premaritall y Female s expose d to lea d afte r marriag e Numbe ro f abonion s an d stillbirth s pe r 100 0 female s 43. 2 47. 6 86. 0 133. 5 Numbe ro f

neonata l death s (firs t year ) pe r 100 0 female s 15 0 21 4 157 27 1 Sinc e th e tim e o f

th e abov e studies , wome n hav e bee n largel y exclude dfro moccupationa l exposur e t o lead . Eve n befor e th e effect s o f industria l lea dex posur e o n pregnanc y wer e documented , however , lea dcompound s wer e know n fo r thei r embryotoxi c propertie s an dwer e ofte n use dt o induc e crimina l abortion. 34 9 I n astud y b y Lane, 35 0 wome n expose d t o lea dlevel s o f

7 5 ug/m 3 wer e examine dfo r effect s o n reproduction . Longitudina l dat ao n 1 5 pregnan cie s indicate da n increas e i n th e numbe r o f stillbirth s an dabortions . N o dat awer e give n o n urinar y lea din women , bu t

me n i n thi s sampl e ha durinar y level s o f 7 5 t o 10 0 ug/liter . I n amor e recen t study 35 1 ofth e pregnancie s o f 104 Japanes e wome n marrie dt o lea dworker s befor e an d afte r thei r husband s bega n lea dwork , miscarriage s increase dt o 84.2/100 0 pregnancie s fro maprelea d rat e o f 45.6/1000 . Th e miscarriag e rat e fo r 7 5 wome n no t

expose dt o lea dwa s 59.1/1000 . Anothe r recen t stud y b y Fahi me t

al. 35 2 i n human s suggest s tha t

subtoxi c lea dabsorptio n durin g preg nanc y ma y b e associate dwitha n increase dincidenc e o f preter mdeliver y an dearl y membran e rupture : 25 3 wome n delivere din Rolla , Missour i (Regio n I) , whic hi s 6 0 t o 8 0 mile s fro mlea dsmelters , an d 24 9 wome n delivere di n Columbia , Missour i (Regio n II) , wher e ther e i s n o lea dindustry . Th e in

cidenc e o f

ter mpregnancie s withearl y membran e ruptur e wa s 1 7 percen t

in Regio n I an d0.4 1 percen t in Regio n II . Th e incidenc e o f prematur e deliverie s wa s 13.0 4 an d3 percent , respectively . A hig hcor relatio n wa s foun dbetwee n lea dconcentration s in materna l an dfeta l blood : bot hwer e significantl y highe r in th e case s o f

preter mpregnancie s an dearl y membran e rupture s tha n in ter mpregnancies . Pregnanc y i s astres s tha t ma y plac e awoma n a t highe r ris k fo r lea dexposure . Bot hiro n deficienc y an dcalciu mdeficienc y increas e th e susceptibilit y o f lea dtoxicity , an dwome n hav e a n increase dris k o f bot hdeficiencie s durin g pregnanc y an dpostpartum . Th e caus e o f

th e increase dperinata l mortalit y may b e amutageni c o r

teratogeni c effec t

o f lead. 35 3 Th e abov e studie s clearl y demonstrat e a n advers e effec t o f lea do n huma n reproductiv e functions , rangin g fro mreduce dpregnanc y rate s t o increase d incidenc e o f

miscarriages , prematur e deliveries , an dstillbirths . Th e mechanism s underlyin g thes e effect s ar e unknow n at

thi s time . Man y factor s coul d contribut e t o th e abov e results , rangin g fro mlea d effect s o n materna l nutritio n o r hormona l stat e befor e o r

durin g pregnanc y t o mor e direc t gametotoxic , embryotoxic , o r teratogeni c effect s tha t coul daffec t

fertilit y o r

feta l viabilit y durin g gestation . Effort s hav e bee n mad e t o defin e mor e precisel y th e point s a t whic hlea dma y affec t reproductiv e function s bot hin th e huma n femal e an dmale , an di n othe r

animals , a s reviewe dbelow . I n regar dt o potentia l lea deffect s o n ovaria n func

tio n in huma n females , Panova 35 4 reporte dastud y o f 140 wome n workin g in aprintin g plan t fo r les s tha n 1 yea r

( 1 t o 1 2 months ) wher e ambien t ai r level s wer e < 7 u g lead/m 3

. Usin g aclassificatio n o f variou s ag e group s (2 0 t o 25 , 2 6 t o 35 , an d3 6 t o 40 ) an dtyp e o f

ovaria n cycl e (normal , anovular , an d disturbe dlutei n phase) , Panov aclaime dtha t statisticall y significan t

difference s existe dbetwee n 11-4 6P.9 1

th e lead-expose dan dcontro l group s in th e ag e rang e o f 2 0 t o 2 5 years . I t

shoul db e note dtha t

th e repor t doe s no t sho w th e ag e distribution , th e leve l o f sig

nificance , o r

th e dat ao n specificit y o f hi s metho do f classification . Also , Zielhui s an dWibowo, 35 5 i n a critica l revie w o f

th e abov e study , conclude dtha t stud y desig n an dpresentatio n o f dat aar e suc htha t

it i s difficul t

t o evaluat e th e author' s conclusio n tha t chroni c exposur e t o lo w lea din ai r lead s t o adis

turbe dfunctio n o f

ovaries . I t

shoul db e note dtha t n o consideratio n wa s give n t o th e dus t level s o f lead , a n importan t

facto r in prin t shops . Unfortunately , littl e els e beside s th e abov e repor t exist s i n th e literatur e i n regar dt o assessin g lea d effect s o n ovaria n functio n o r othe r factor s affectin g huma n femal e fertility . No r ar e ther e man y studie s offerin g firmdat ao n materna l variables , e.g. , hor

mona l state , tha t

ar e know n t o affec t

th e abilit y o f th e pregnan t

woma n t o carr y th e fetu s ful l term . I n addition , ther e ar e n o studie s tha t demonstrat e con clusivel y adirec t

lead-induce dteratogeni c effec t o n th e huma n fetus , althoug hth e transfe r o f lea dacros s th e huma n placent aan dit s potentia l threa t t o th e conceptu s hav e bee n recognize dfo r mor e tha n acen tury. 35 6 Nevertheless , documentatio n o f placenta l transfe r o f lea dt o th e fetu s an ddat ao n relevan t parameters , e.g. , feta l bloo dlea dlevel s resultin g fro msuc htransfer , hel p t o buil dth e cas e fo r apo tential , bu t

a s ye t no t clearl y defined , threa t

fo r sub

tl e teratogeni c an dothe r deleteriou s healt heffects . Th e placenta l transfe r

o f lea dha s bee n estab

lished , in part , b y variou s studie s tha t hav e disclose d measurabl e quantitie s o f lea din huma n fetuse s o r newborns . A n analysi s o f huma n feta l tissue s b y Barltrop 35 7 demonstrate dtha t placenta l transfe r

o f lea dbega n a s earl y a s th e 12thwee k o f gestatio n an d tha t tota l lea dconten t

increase dthroughou t

feta l development , wit hth e highes t concentration s occur rin g in bone , kidney , an dliver , an dlesser , bu t sig

nificant , amount s occurrin g i n blood , brain , an d heart . Barltro p ha s als o pointe dou t tha t th e dis

tributio n o f

lea dwithi n th e fetu s a t differen t stage s o f developmen t

i s probabl y mor e importan t tha n th e tota l amoun t

presen t a t birth . O f interes t i n thi s regar dar e th e dat ao f Schroede r an dTipton, 35 8 wh o showe dtha t th e mea n lea dleve l in brain s o f

stillbor n U.S . childre n ( n = 22 ) wa s 1 0 pp m(dr y ash) , bu t

tha t ther e wa s a n undetectabl e leve l fo r norma l infants , youn g children , an dteen s ( 0 t o 1 9 years ; n = 23) . I n thi s study , however , th e level s o f detectio n ar e no t

stated , s o tha t

th e relativ e increas e in leve l canno t b e assessed . Also , i t

i s no t clea r t o wha t

exten t feta l tissu e preparatio n an d preservatio n wer e controlle dfo r contamination . Wibberl y an dcoworkers 35 9 hav e recentl y foun d tha t placenta l lea dlevel s i n th e cas e o f stillbirt ho r neonata l deat hwer e significantl y highe r tha n in th e cas e o f norma l births . Placenta l level s wer e greate r tha n 1. 5 ug/ g in onl y 7 percen t ofth e norma l births , wherea s level s wer e greate r tha n thi s i n 6 1 percen t

o f th e stillbirth s o r

neonata l deaths . Thi s doe s no t mea n tha t

lea di s acausa l facto r

i n suc hdeath s an d coul dindicat e tha t

lea daccumulate s in th e placent a in time s o f

feta l stress . Ther e ar e anumbe r

o f recen t studie s o n th e passag e o f

lea dthroug hth e placenta l barrie r a s assesse db y lea dlevel s i n cor dbloo dand/o r mater na l blood . Fo r

example , i n th e stud y o f Gershani k

e t a l 360,36 1 9 8 cord-bloo dsample s matche dwit h materna l bloo dsample s showe dahig hcorrelatio n betwee n lea dlevel s in infant s (mea n = 10. 1 ug/dl ) an dthei r

mother s (mea n = 10. 3 figldl), wit ha produc t momen t correlatio n coefficien t o f 0.6377 . Thi s suggest s tha t

infant s ma y b e bor n wit hbloo d lea dlevel s tha t

essentiall y matc hthos e o f thei r mothers . I n regar dt o assessin g group s a t ris k fo r suc hprenata l exposure , thes e author s als o studie da grou p o f 21 8 cord-bloo dsample s (17 0 urban , 4 8 rural ) an dobserve dtha t th e mea n urba n valu e (9. 7 ug/dl ) wa s significantl y differen t ( p <0.05 ) fro mth e mea n rura l valu e (8. 3 ug/dl) , suggestin g ahighe r ris k o f urba n newborn s fo r

prenata l lea dexposure . Similarly , Scanlon 36 2 sample dcord-bloo drandoml y fro mnorma l infant s whos e mother s ha dsuburba n ( n = 15 ) o r urba n ( n = 13 ) residences . Th e averag e ur ba n valu e wa s 22. 1 figldl (1 0 t o 3 7 ug/dl) , wherea s th e correspondin g suburba n leve l wa s 18. 3 ug/dl . Smokin g wa s withou t

significan t

effec t o n thes e levels . Thes e result s ten dt o confir mth e finding s o f Gershani k

e t al. 36 1 Harri s an dHolley, 36 3 o n th e othe r hand , surveye dcor dan dmaterna l bloo din 2 4 pair s (1 1 suburba n an d1 3 urban ) an dfoun damea n cord-bloo dvalu e o f

12. 3 ug/d l an damea n materna l bloo dleve l o f

13. 2 ug/dl . N o significan t differenc e wa s therefor e see n in cord-bloo dlevel s a s afunctio n o f materna l residence , thoug halarge r sampl e migh t hav e yielde dsignifican t effect s sinc e th e one s foun d wer e in th e sam e directio n a s thos e foun din othe r studies . Tha t th e prenata l exposur e o f th e fetu s t o lead , eve n in th e absenc e o f

teratogeni c effects , ma y b e o f consequenc e in regar dt o advers e healt heffect s i s demonstrate db y studie s relatin g feta l an dcord

bloo dlevel s t o som e change s i n feta l hem e synthesi s an dclaime dincidence s o f prematur e births . Haa s e t al. 36 4 examine d29 4 mother-infan t pair s fo r

bloo d 11-4 7P.9 2

lea dlevel s a s wel l a s fo r th e correspondin g urinar y AL A levels . Th e materna l bloo dmea n wa s 16.8 9 figldl an dth e feta l bloo dmea n wa s 14.98 , witha correlatio n o f

0.53 8 (p <0.001) . I n th e infants , th e level s o f

bloo dlea dan durinar y AL A wer e positivel y correlate d( r = 0.1877 , p <0.0I) . Whethe r abiologica l significanc e exist s here , however , i s no t

clear . Accordin g t o th e authors, 36 4 th e positiv e correlatio n betwee n lea di n bloo dan d urinar y AL A fo r

th e grou p a s awhol e indicate d ther e wa s alread y a n effec t a t lowe r bloo dlea d levels , i.e. , increase dsusceptibilit y o f hem e syn thesis . I n astud y o f

Fahim 36 5 o n cord-bloo dlea dlevels , bloo dlea dvalue s in pregnan t wome n havin g pre ter mdeliver y an dprematur e membran e rupture , an dresidin g i n alea dbel t are a(minin g an dsmeltin g area) , ha dsignificantl y highe r bloo dlea dlevel s tha n wome n deliverin g a t

ful l term . A confusin g aspec t o f thi s study , however , i s th e similarit y o f bloo dlea d level s i n wome n i n th e nonlea dan dlea dbel t areas . Thoug hanumbe r

o f othe r problem s ma y b e see n withth e analytica l aspect s o f thi s study , i t

mus t b e note dtha t

amon g th e 24 9 pregnan t wome n i n th e contro l grou p outsid e th e lea dbel t are ath e percen tag e o f wome n havin g preter mdeliverie s an dpre matur e ruptur e wer e 3 an d0. 4 percent , respectively , wherea s th e correspondin g value s fo r th e lea dare a (n = 253 ) wer e 13.0 4 an d16.9 9 percent , respec tively . Wit hreferenc e t o mor e subtl e prenata l effects , Palmisan o e t

al. 36 6 note dfailur e t o thriv e an d neurologica l deficit s i n a10-week-ol dinfan t whos e mothe r ha dlea dpoisonin g concomitan t wit h alcoholis mdurin g pregnancy . Whe n thi s infan t wa s challenge dwit hachelatin g agent , a n abnorma l urin

ar y excretio n o f

lea dwa s observed , indicatin g in

trauterin e exposure . Postnata l exposur e i n thi s cas e wa s rule dout . Other , mor e controlle dlaborator y studie s o n animal s (discusse dlater ) als o sugges t tha t teratogeni c effect s occur , bu t usuall y onl y a t

ver y hig hlea dexposur e levels . A report 36 7 o n fata l birt hdefect s in childre n con ceive ddurin g aperio do f tim e whe n thei r

fathe r wa s lea dpoisone dhint s a t

importan t

effect s o f

lea do n th e fetu s bein g mediate dvi ahuma n male s a s wel l a s females . Certai n othe r

studies 369

- 37 0 demonstrate d likel y lea deffect s o n variou s aspect s o f mal e reproductiv e functions . Lancranja n e t

al. 3 6 8 hav e reporte dtha t moderatel y increase dlea dabsorptio n (bloo dlea d mea n = 52. 8 ug/dl ) resulte di n gonada l impair

ment . Th e effect s o n th e teste s wer e show n t o b e direc t i n tha t test s fo r

hypothalamopituitar y in

fluenc e wer e negative . A grou p o f 15 0 workme n wh o ha dlong-ter mexposur e t o lea din varyin g degree s wa s studied . Clinica l an dtoxicologica l criteri awer e use dt o categoriz e th e me n int o fou r groups : lead

poisone dworkme n (74. 5 ug/dl ) an dthos e showin g moderat e (52. 8 figldl), sligh t (4 1 figldl), an d physiologi c (2 3 ug/dl ) absorptio n o f lead . Seme n analysi s reveale dasthenospermia , hypospermia , an d teratospermi ain lead-poisone dworker s an dthos e withmoderatel y increase dabsorptio n oflea d(bloo d lea dlevel s = 5 0 t o 8 0 ug/d l fo r th e latter) . Th e ab

norma l spermatozo ainclude dbinucleated , bicephalus , amorphous , an dtapere dforms . I n con trast , slightl y increase do r physiologi c absorptio n o f lea dha dn o effect s o n th e reproductiv e abilit y o f workmen . I n th e revie w o f

Stofen, 36 9 dat afro mth e wor k o f Nesko v in th e USS Rwer e reporte dinvolvin g 6 6 worker s expose dchiefl y t o lead-containin g gasolin e (organi c lead) . I n 5 8 me n ther e wa s adecreas e o r disappearanc e o f

erection , in 4 1 ther e wa s earl y ejaculation , an din 4 4 ther e wa s adiminishe dnum be r o f spermatocytes . Th e literatur e reviewe dher e o n lea deffect s o n huma n reproductio n an ddevelopmen t leave s littl e doub t a s t o th e fac t

tha t lea ddoes , in fact , exer t sig

nifican t advers e healt heffect s o n reproductiv e func

tions . Mos t

studies , however , hav e typicall y looke d at th e effect s o f

prolonge dmoderate-to-hig hex posure s t o lead , e.g. , thos e encountere din industria l situations , an dman y report s d o no t provid e definit e informatio n o n externa l exposur e level s o r bloo d lea dlevel s at

whic hspecifi c effect s ar e observed . 11.7. 2 Anima l Studie s Anima l experiment s hav e demonstrate dtha t level s o f lea dtha t

ar e compatibl e wit hlif e hav e in

terfere dwithnorma l reproduction . Man y studie s assesse dth e effect s o f

lea dexposur e o f

bot hparent s o n reproduction . Schroede r an dMitchener, 37 0 fo r example , showe dareductio n in th e numbe r o f offsprin g o f

rat s an dmic e tha t

wer e give n drinkin g wate r containin g lea din aconcentratio n o f 2 5 ppm . I n asubsequen t

report, 37 1 however , i t

wa s note dtha t animal s in th e earlie r

stud y wer e chromiu mdefi

cient . N o effect s wer e foun din animal s wit hnorma l diets . Th e combine deffec t o f materna l an dpaterna l ora l lea dintoxicatio n upo n reproductiv e perfor

manc e wa s studie din rat s b y Morri s e t al. 37 2 wh o re porte dsignifican t

reductio n i n weanin g percentag e amon g offsprin g o f

rat s fe d51 2 pp mlead . Stow e an d Goyer 37 3 assesse dth e relativ e paterna l an dmaterna l 11-4 8P.9 3

effect s o f

lea da s measure db y th e progen y o f F , lead-toxi c rats . Sprague-Dawle y femal e rat s bein g fe dlaborator y cho w withan dwithou t 1 percen t

lea d acetat e wer e bre dt o normal , mature , Sprague

Dawle y males . Th e pregnan t rat s wer e continue do n thei r respectiv e ration s withan dwithou t lea d throughou t

gestatio n an dlactation . Offsprin g o f thes e matings , th e F : generation , wer e fe dth e ration s o f thei r dam s an dwer e mate din combination s a s follows : contro l femal e t o contro l mal e (CF-CM) , contro l femal e t o lead-toxi c mal e (CF-PbM) , lead

toxi c femal e t o contro l mal e (PbF-CM) , an dlead

toxi c femal e t o lead-toxi c mal e (PbF-PbM) . Th e result s identifyin g specifi c deleteriou s paterna l an d materna l effect s o f

lea dtoxicit y upo n ra t

reproduc

tio n ar e show n in Tabl e 11-11 . TABL E 11-11 . REPRODUCTIV E PERFORMANC E O F F , LEAD-TOXI C RATS***-* * Paramete r Typ e o f matin g CF-C M CF-Pb M PbF-C M PbF-Pb M Litter s observe d Pups/litte r Pu p birt h weight , g Weane d rats/litte r Surviva l rate , % 2 2 11.9 0 ± 0.40 a 6.7 4 ± 0.1 5 9.8 4 ± 0.5 0 89.8 0 ±3.2 0 Litte rbirt h weight/Da m breedin g weight , % 28.0 4 ±1.3 0 Litte rbirt h weight/Da m whelpin g weight , % 19.0 9 ±0.8 0 Gestatio n gain/Pup s pe rlitter , g 11.5 4 ±0.6 0 Nonfeta l gestational/Gain/fetus , g 3.9 3 ±0.3 8 2 4 10.1 0 ±0.5 0 5.9 2 ±0.13 c 7.0 4 ±0.77<

= 73.7 0 ± 7.9 0 22.3 0 ± 0.90 = 15.9 7 ± 0.58 = 11.20 ± 0.7 4 4.8 3 ±0.4 7 3 6 8.7 8 ± 0.30 b 5.4 4 ± 0.13=." " 5.4 1 ± 0.74C 1 52.6 0 ± 7.2 0 19.3 5 ± 1.00c 14.2 8 ± 0.66 c 11.1 7 ± 0.5 4 4.1 5 ± 0.4 2 1 6 7.7 5 ± 0.50 = 4.8 0 ± 0.19C-M

J 2.7 2 ± 0.70cd. e 30.0 0 ± 8.20C.-

U 15.3 8 ± 1.10C-

U 11.5 8 ± 0.78=--". ' 12.3 4 ± 1.2

4 3.9 6 ± 0.4 6

a Mea n ±S.E.M . b Significantl y( p <0.05 ) les s tha n mea n fo rCF-CM . ^Significantl y( p <0.01 ) les s tha n mea n fo rCF-CM . -"Significantl y( p <0.01 ) les s tha n mea n fo rCF-PbM . e Significantl y( p <0.01 ) les s tha n mea n fo rPbF-CM . 'Significantl y( p <0.05 ) les s tha n mea n fo rPbF-CM . Th e paterna l effect s o f

lea dinclude da1 5 percen t reductio n i n th e numbe r o f pup s bor n pe r

litter , a1 2 percen t reductio n in th e mea n pu p birt hweight , an d a n 1 8 percen t

reductio n i n pu p surviva l rate . Th e materna l effect s oflea dinclude da2 6 percen t reduc

tio n i n litte r

size , 1 9 percen t

reductio n i n mea n pu p birt hweights , an d4 1 percen t reductio n in pu p sur vival . Th e combine dmal e an dfemal e effect s o f lea d toxicit y resulte di n 3 5 percen t reductio n in th e num be r o f pup s pe r

litter , 2 9 percen t

reductio n i n th e pu p birt hweights , an d6 7 percen t reductio n i n pu p surviva l t o weaning . Stow e an dGoyer 37 3 classifie d th e effec t o f lea dupo n reproductio n a s gametotoxic , intrauterine , an dextrauterine . Th e gametotoxi c effect s o f lea dappea r

t o b e irreversibl e an dha dad

ditiv e mal e an dfemal e components . Th e in

trauterin e effect s resulte dfro mth e transmammar y passag e o f

lea dfro mth e da mt o th e sucklin g pu p addin g insul t

t o th e gametotoxi c an duterin e en vironmenta l effects . Th e effect s o f

lea do n th e reproductio n o f sexuall y matur e mal e an dfemal e Sesc o rat s wer e reporte db y Hildebran de t

al. 37 4 Th e animal s wer e orall y fe d lea dacetat e a t dose s o f

5 an d100 u g fo r

3 0 days . Contro l female s possesse dth e sam e level s o f lea d concentratio n in thei r

bloo da s thos e fo r

mal e con trols . However , fo r

th e treate danimal s th e bloo d lea dlevel s fo r

th e female s wer e highe r tha n thos e fo r th e males : 3 0 figldl

versu s 1 9 ug/d l a t

5 u g lea dace tate , an d5 3 ug/d l versu s 3 0 ug/d l a t 100 u g lea d acetate . The y note dimpotenc e an dprostati c hy

perplasi ain th e male s a t th e lowe r

dose , progressin g t o testicula r

damag e wit hinhibitio n o f sper matogenesi s in thos e reachin g bloo dlevel s o f 5 0 ug/dl . I n th e females , the y note dirregularit y ofth e estru s cycl e a t

bot hdoses . Whe n lea dlevel s reache d 5 0 ug/dl , th e femal e rat s develope dovaria n follicu

la r cyst s wit hareductio n i n th e numbe r o f corpor a lutea . A subsequen t

stud y employin g Sprague

Dawle y rat s wa s unabl e t o replicat e thes e find

ings. 37 5 A numbe r

o f othe r studie s hav e focuse dmor e specificall y o n eithe r

materna l o r

paterna l lea dex posur e effects . Fo r

example , in referenc e t o materna l effects , histopathologica l change s i n ovarie s i n lead

poisone dRhesu s monkey s hav e bee n demon

11-4 9P.9 4

strated. 37 6 Mos t

othe r anima l studie s hav e utilize d rodents . Kenned y e t

al. 37 7 administere da n aqueou s solu

tio n oflea dt o mic e (day s 5 t o 1 5 o f gestation ) an dt o rat s fro mday s 6 t o 1 6 o f gestation . A t

dosag e level s o f 7.14 , 71.4 , an d71 4 mg/k g bod y weigh t ther e wer e n o observe deffect s o n th e numbe r o f fetuse s resorbe do r

th e numbe r

o f viabl e fetuses . N o teratogeni c effect s o n gros s examinatio n wer e seen , an da n effec t

o n bod y weigh t

wa s observe donl y at th e highes t

leve l employe d(71 4 mg/kg) . Hubermon t

e t al. 37 8 expose dfemal e rat s t o lea din drinkin g wate r

(0.1 , 1 , an d1 0 ppm ) fo r 3 week s befor e mating , durin g pregnancy , an d3 week s afte r delivery . I n th e highes t exposur e grou p (1 0 ppm) , materna l an dnewbor n bloo dan dkidne y lea dvalue s wer e elevated . Inhibitio n o f 8-ALA D an delevatio n o f FE Pin tissue s wer e als o noted . Maisi n e t al. 37 9 expose dfemal e mic e t o lea din th e die t (0. 1 an d0. 5 percent ) fro mth e da y o f vagina l plu g t o 1 8 day s afterwards . Th e numbe r o f pregnan cie s decrease dan dth e numbe r o f embryo s succumb

in g afte r implantatio n increased . Similarly , Jacquet 38 0 expose dfemal e mic e vi a lea din die t

(0.125 , 0.25 , an d0.5 0 percent ) fro m vagina l plu g t o 1 6 t o 1 8 day s afterwards . A t th e mid

dl e dosage , pregnanc y incidenc e decreased , th e numbe r o f embryo s dyin g befor e implantatio n in

creased , an dth e numbe r o f corpor alute ashowe da decrease . A t

th e highes t

dosage , th e numbe r

o f embryo s dyin g afte r

implantatio n increased , wherea s decrease s in bod y weigh t o f survivin g embryo s wer e seen . Othe r studie s hav e focuse do n lea deffect s o n paterna l reproductiv e functions . Fo r example , th e dat afro mstudie s o f

rabbits, 38 1 guine apigs, 38 2 an d rats 373

- 38 3 indicat e tha t

paternall y transmitte deffect s fro mlea dca n occur , includin g reduction s in litte r size , in weight s o f

offspring , an din surviva l rate . Col e an dBachhuber, 38 1 usin g rabbits , wer e th e firs t t o confir mexperimentall y th e paterna l effect s o f lea dintoxication . Th e litter s o f dam s sire db y lead-toxi c mal e rabbit s wer e smalle r tha n thos e sire db y contro l males . Weller 38 2 similarl y demon

strate dreduce dbirt hweight s an dsurviva l amon g offsprin g o f

lead-toxi c mal e guine apigs . Verm ae t

al. 38 4 fe da2-percen t

aqueou s solutio n o f lea dsubacetat e in drinkin g wate r t o 1 4 mal e Swis s mic e fo r 4 weeks . Th e tota l mea n intak e o f lea d amounte dt o 1.6 5 g . The y place dth e mal e wit h3 virgi n untreate dfemale s fo r 1 week . Th e overal l in

cidenc e o f pregnancy , indicativ e o f fertility , wa s 52. 7 percen t

in th e contro l grou p a s compare dt o 27. 6 percen t

i n th e treate dgroup . Th e fertilit y ofth e treate dmale s wa s reduce dt o 5 0 percent . The y calculate dth e mutagenicit y inde x (numbe r o f earl y feta l deaths/tota l implants ) t o b e 10. 4 fo r lead

treate dmic e versu s 2. 9 fo r control s (X 2 = 10.4 , p < 0.05) . I n th e stud y o f

Maisi n e t

al., 37 9 mal e mic e receive d 0. 1 an d1 percen t

lead , a s th e acetate , in th e diet . Th e percentag e o f

abnorma l spermatozo aincrease d withincreasin g exposure . Ultrastructura l change s wer e present . I n th e revie w o f

Stofen, 36 9 severa l studie s fro m Russia n laboratorie s wer e evaluated . A s cite db y St6fen , Egorov ae t

al. , fo r example , injecte dlea da t ados e o f 2 ug/k g 6 time s ove r

a10-da y perio dan d observe ddamag e t o teste s an dspermatozoa . Stofe n als o reporte dtha t

Golubov ae t

al . foun dmorpho

logica l change s in teste s o f rat s tha t

receive d2 m g lead/k g bu t

no t i n rat s receivin g 0. 2 mg/kg . Lea dappear s t o b e teratogeni c in som e species , at leas t a t hig hexposur e levels . McClai n an d Becker, 38 5 for

example , administere dsingl e dose s o f 2 5 t o 7 0 mg/k g o f

lea dnitrat e intravenousl y t o preg nan t rat s o n day s 8 throug h1 7 o f gestation . A urorectocauda l syndro mo f malformation s wa s pro duce dwhe n lea dwa s administere do n th e 9t hda y o f gestation . Th e lea dnitrat e wa s increasingl y embryo

an dfetotoxi c whe n administere do n late r day s o f gestatio n (day s 1 0 t o 15 ) bu t no t teratogenic . Fer m an dCarpenter 38 6 a s wel l a s Fer man dFerm 38 7 re porte dincrease dembryoni c resorptio n an dmalfor

matio n rate s whe n variou s lea dsalt s wer e ad

ministere dt o pregnan t

hamster s o n th e 8t hda y o f gestation . Th e teratogeni c effec t o f lea dwa s almos t completel y restricte dt o th e tai l region . Malforma

tion s ofth e sacra l an dcauda l vertebrae , resultin g in absen t o r stunte dtails , wer e observed . Th e reason s fo r

th e localizatio n ofth e teratogeni c effect s o f lea dar e unknow n at

thi s time . Fer man d Ferm 38 7 hav e suggeste dtha t th e specificit y coul db e explaine db y a n interferenc e withspecifi c enzymati c event s durin g earl y development . Lea dalter s mitochondria l functio n an denhance s o r inhibit s a variet y o f

enzymes, 38 8 an y o r

al l o f whic hcoul din

terfer e wit hnorma l development . Ferm 38 9 ha s als o reporte dtha t

i n th e presenc e o f

cadmiu mth e teratogeni c effec t

o f lea din hamster s i s potentiated . Studie s b y Giliani 390

- 39 1 sho w tha t lea di s teratogeni c t o chic k

embryos . Whe n 2-day-ol d embryo s wer e give n varyin g dose s o f lea dacetat e (0.00 5 t o 0.0 8 mg/egg ) an dwer e examine do n th e 1 1 -5 0P.9 5

8thda y o f

incubation , congenita l cardia c anomalie s wer e demonstrated. 39 0 Th e incidenc e o f cardia c anomalie s ros e withincreasin g dose s o f lead . Othe r importan t

anomalie s wer e reduce dbod y size , micromelia , shortene dneck , microophthalmia , rup ture dbrain , shortene dbeak , twiste dnec k an dlimbs , an deverte dviscera. 39 1 Th e mos t commo n develop

menta l anomalie s wer e retarde dgrowt han dnec k abnormalities . I t

shoul db e note dtha t i n thes e studie s high , acut e dose s o f lea dwer e administered . Ther e i s apaucit y o f

informatio n regardin g th e teratogenicit y an ddevelopmenta l toxicit y o f chroni c lea dexposure . Kimme l e t al. 26 5 expose dfemal e rat s chronicall y t o lea dacetat e vi adrinkin g wate r (0.5 , 5 , 50 , an d25 0 ug/g ) fro mweanin g throug hmating , gestation , an dlactation . N o teratogeni c effect s wer e observed , althoug hexposur e t o 25 0 ug/ g lea dace tat e cause dasligh t

bu t nonsignifican t

increas e in feta l resorptions . Th e lead-treate danimal s pro duce dlitter s o f

norma l numbers , bu t

th e offsprin g fro mth e 50

- an d250-ug/ g group s weighe dles s at weanin g an dshowe ddelay s in physica l develop

ment . Reite r

e t al. 26 4 hav e als o observe ddelay s in th e developmen t

o f th e nervou s syste min offsprin g expose dt o 5 0 ug/ g lea dthroughou t gestatio n an d lactation . Whethe r

thes e delay s in developmen t resul t fro madirec t

effec t o f lea do n th e nervou s syste mo f

th e pup s o r

reflec t secondar y change s (resultin g fro mmalnutrition , hormona l inbalance , etc. ) i s no t

clear . Whateve r

th e mechanism s in

volved , thes e studie s sugges t tha t low-level , chroni c exposur e t o lea dma y induc e postnata l developmen

ta l delay s in rats . I t shoul db e note dtha t

th e abov e report s o n nor ma l developmenta l delay s migh t b e analogou s t o certai n suggeste dneurobehaviora l effect s o f lea d fro min utero exposure s o f human s (Sectio n 11.5) . I n addition , it

ha s bee n demonstrated 39 2 tha t con centration s o f

lea do f

approximatel y 170 ug/d l whol e bloo dca n inhibi t 8-ALA D activit y in bot h bloo dan dbrai n o f

sucklin g rats . Althoug hbrai n tissu e wa s no t

purge do f

residua l blood . ALA D con tributio n t o brai n ALA D activit y woul dno t b e ex pecte dt o b e significant . I t i s possibl e tha t

8-ALA D activit y migh t

b e diminishe din utero at thes e lea d level s an dtha t

lea dat thes e level s migh t

hav e harmfu l consequence s o n neurologica l developmen t ofth e fetus . Ther e i s nee dfo r mor e critica l researc h t o evaluat e th e possibl e subtl e toxi c effect s o f lea dt o th e fetus . Thi s overal l evaluatio n i n th e offsprin g ma y nee dt o b e correlate dwithth e possibl e additiv e effect s o f

paterna l lea dburden . A t thi s time , however , insufficien t

evidenc e exist s t o allo w for fir mstatement s o n exposur e level s at whic han y suc h effect s o n th e fetu s fro mmaterna l o r paterna l lea d burden s migh t

b e observed . 11. 8 TH E ENDOCRIN E SYSTE M Th e endocrin e effect s o f lea dar e no t

wel l define d a t th e presen t

time . Lea di s known , however , t o decreas e th e thyroi dfunctio n i n ma n an dexperimen

ta l animals . Porritt 39 3 suggeste din 193 1 tha t lea d dissolve dfro mlea dpipe s b y sof t wate r wa s th e caus e o f hypothyroidis mi

n individual s livin g in southwes t England . Later , Kreme r an dFrank 39 4 reporte dth e simultaneou s occurrenc e o f myxedem aan dplumb

is min ahous e painter . Monaenkova 39 5 in 195 7 ob

serve dimpaire dconcentratio n o f 131 I b y thyroid s in 1 0 ou t o f 4 1 patient s withindustria l plumbism . Sub

sequently , Zel'tser 39 6 showe dtha t in vivo 13I I uptak e an dthyroxin e synthesi s b y ra t thyroi dwer e decrease db y lea dwhe n dose s o f 2 an d5 percen t lea dacetat e solutio n wer e administered . Uptak e o f 131 I , sometime s decrease din me n wit hlea dpoison

ing , ca n b e offse t

b y treatmen t

wit hthyroid-stimulat

in g hormon e (TSH). 397

- 39 8 Lea dma y ac t t o depres s thyroi dfunctio n b y inhibitin g S H group s o r b y dis

placin g iodin e i n aprotei n sulfony l iodin e carrier, 39 7 an dth e result s sugges t

tha t excessiv e lea dma y ac t a t bot hth e pituitar y an dth e thyroi dglan ditsel f t o im

pai r thyroi dfunction . Sandstea de t

al. 39 9 studie dth e effect s o f lea din

toxicatio n o n th e pituitar y an dadrena l functio n i n man . Ther e wa s adecreas e in secretio n o f pituitar y gonadotrophi c hormones . Thei r dat asuggeste dtha t lea dma y interfer e wit hpituitar y functio n i n ma n an dma y produc e clinicall y significan t hypopituitar

is min some . It s effect s o n adrena l functio n wer e les s consistent , bu t

som e o f

th e patient s showe da decrease dresponsivenes s t o a n inhibito r (metapyrone ) o f

11-beta-hydroxylatio n in th e syn thesi s o f Cortisol . Excessiv e ora l ingestio n o f lea din ma n ha s resulte din pathologica l change s in th e pituitary

adrena l axi s a s indicate db y decrease dmetapyron e responsiveness , adepresse dpituitar y reserve , an d decrease dimmunoreactiv e ACTH. 400

- 40 1 Thes e sam e event s ma y als o affec t adrena l glan dfunctio n inasmuc ha s decrease durinar y excretio n o f 17-hy

droxycorticosteroid s wa s observe din thes e patients . Suppressio n o f

responsivenes s t o exogenou s ACT H i n th e zon afasciculat ao f th e adrena l corte x ha s bee n reporte din lead-poisone dsubjects, 40 2 an d impairmen t

o f th e zon aglomerulos aofth e adrena l corte x ha s als o bee n suggested. 40 3 Ther e als o i s som e evidenc e suggestin g tha t lea d 11-5 1P.9 6

may caus e aderangemen t in serotoni n metabolis m o r utilization . Tryptopha n i s th e precurso r o f th e neuroendocrin e regulator y amine , serotonin . A n effec t o f lea do n serotoni n synthesi s o r utilizatio n i s inferre di n par t

fro mth e observatio n o f Urbanowic z e t al. 40 4 wh o reporte daris e in 5-hydroxyindol e aceti c aci d(5-HIAA ) excretio n i n th e urin e o f worker s heavil y expose dt o lead . Thi s ris e precede d th e ris e in urinar y 8-AL A an dcoproporphyrin . A simila r ris e in 5-HIA A excretio n wa s note di n moderatel y lead-expose dworkers. 32 2 Mor e re cently , however , Schiel e e t al., 40 5 usin g adifferen t analytica l method , wer e unabl e t o fin dan y signifi

can t elevatio n in 5-HIA A excretion . 11. 9 TH E HEPATI C SYSTE M Th e effec t

o f lea dpoisonin g o n live r functio n ha s no t bee n extensivel y studied . I n alaborator y stud y o f 30 1 worker s in alea dsmeltin g an drefinin g facility , Coope r

e t al. 40 6 foun dseru mglutami c ox alaceti c transaminas e (SGOT ) activit y a t a n in

crease dvalu e o f

11. 5 percen t

i n subject s wit hbloo d lea dlevel s belo w 7 0 ug/dl , 2 0 percen t i n thos e wit h abloo dlea dleve l o f

abou t 7 0 ug/dl , an d5 0 percen t i n worker s wit habloo dlea dleve l o f abou t 10 0 ug/dl . Th e correlatio n betwee n bloo dlea dlevel s an dSGO T wa s no t

statisticall y significant . I n th e ab

senc e o f informatio n o n th e possibl e influenc e o f diet , infection , o r

persona l habits , however , th e author s wer e unabl e t o dra w an y definit e conclu

sion s concernin g th e etiolog y o f thes e changes . Th e live r i s th e majo r

orga n fo r

th e detoxificatio n o f drugs . I n acut e lea dpoisoning , th e mixed-func

tio n oxidas e syste mo f

live r endoplasmi c reticulu m i s impaired. 40 7 Th e activit y o f thi s enzym e system , involve di n th e hepati c biotransformatio n o f medicaments , hormones , an dman y environmenta l chemicals , i s closel y relate dt o th e availabilit y ofth e microsoma l hemoprotein , cytochrom e P-450. 40 8 I t ha s bee n show n tha t

i n rat s lea dinduce s inhibitio n o f hem e synthesi s and , therefore , cause s areductio n i n cytochrom e P-45 0 levels , wit hconsequen t impair

men t ofth e mixed-functio n oxidas e system. 40 9 Drug

metabolizin g activitie s wer e significantl y decrease d i n th e lead-poisone danimals . Intensit y an dduratio n o f thes e change s wer e dos e dependent . In vivo ex periments , base do n th e duratio n o f pentobarbita l sleepin g time , provide dfurthe r evidenc e fo r

th e in

hibitio n o f

dru g metabolis mi n lead-poisone drats . Thes e dat awoul dsugges t tha n a n enhance dsen sitivit y t o xenobiotic s (drugs , pesticides , foo daddi

tives , etc. ) shoul db e expecte dt o occu r i n lead

poisone danimals . Alvare z e t al. 41 0 studie dth e effec t oflea dexposur e o n dru g metabolis mi n childre n an d adults . Ther e wer e n o difference s betwee n tw o nor ma l childre n an deigh t lead-poisone dchildre n in thei r capacitie s t o metaboliz e tw o tes t drugs , anti

pyrin e an dphenylbutazone . Thi s migh t sugges t tha t lo w plasm aconcentration s o f lea dd o no t

hav e a n effec t o n th e hepati c cytochrom e P-450-dependen t enzymati c activitie s i n children . I n 2 acutel y poisone dchildren , in who mplasm alevel s o f lea d exceede d6 0 figldl, antipyrin e half-live s wer e sig

nificantl y longe r

tha n normal , an dtherap y wit h EDT A le dt o biochemica l remissio n o f th e diseas e an drestoratio n o f

derange ddru g metabolis m towar dnormal . Hepati c dru g metabolis min eigh t adul t patient s showin g marke deffect s o f chroni c lea dintoxicatio n o n th e erythropoieti c syste mwa s studie db y Alvare z e t al. 4 " Th e plasm aeliminatio n rat e o f antipyrine , which , a s note dabove , i s adru g primaril y metabolize db y hepati c microsoma l enzymes , wa s determine din eigh t

subject s prio r

t o an dfollowin g chelatio n therapy . I n seve n o f eigh t subjects , chela

tio n therap y shortene dth e antipyrin e half-lives , bu t th e effec t wa s minimal . Th e tw o author s conclude d tha t chroni c lea dexposur e result s i n significan t in

hibitio n o f

th e hem e biosyntheti c pathwa y withou t causin g significan t

change s i n hepati c cytochrom e P-450-associate denzymati c activities . 11.1 0 TH E CARDIOVASCULA RSYSTE M Unde r condition s o f

long-ter mexposur e a t hig hlevels , arterioscleroti c change s hav e bee n demonstrate din th e kidney . I n 1963 , Dingwall-For

dyc e an dLane 8 2 reporte damarke dincreas e i n th e cerebrovascula r

mortalit y rat e amon g heavil y ex pose dlea dworker s a s compare dwit hth e expecte d rate . Thes e worker s wer e expose dt o lea ddurin g th e firs t quarte r o f thi s centur y whe n workin g condition s wer e quit e bad . Ther e wa s n o simila r increas e in th e mortalit y rat e fo r

me n employe dmor e recently . Hypertensio n i s a n importan t elemen t

in th e etiolog y o f

cerebrovascula r

deaths . Tabersha w an d Cooper 41 2 di da n epidemiologica l stud y o f 126 7 worker s wh o ha dbee n expose dt o lea da s aresul t o f thei r occupatio n i n eithe r

th e batter y o r

lea dsmelt

in g industr y betwee n 194 7 an d1970 . Man y wer e foun dt o hav e bloo dlea dconcentration s in exces s o f 8 0 ug/dl . Th e author s conclude dtha t ther e wa s ex ces s mortalit y associate dwithonl y tw o categorie s o f illness , chroni c nephriti s an dhypertension . Th e in

crease dincidenc e o f

hypertensio n in lea dworker s ha s als o bee n reporte db y Monaenkov aan d Glotova 41 3 an dVigdortchik. 41 4 O n th e othe r hand , 11-5 2Crame r an dDahlberg 41 5 studie dth e incidenc e o f hy

pertensio n i n apopulatio n o f 36 4 industriall y ex pose dmen , 27 3 o f

who mha dalong-ter mexposur e t o lead . The y subdivide dth e worker s int o lead

affecte dan dnonlead-affecte dgroup s base do n th e urinar y coproporphyri n test . Ther e wa s n o statisticall y significan t differenc e betwee n th e group s no r

wa s th e incidenc e highe r tha n tha t

ex pecte dfo r

nonexpose dme n in th e genera l popula

tion . Othe r

report s o n th e questio n d o no t sho w hy

pertensio n t o b e undul y prevalen t amon g lea d workers. 350

- 41 6 I t

i s no t clear , therefore , whethe r th e vascula r effect s o f

lea din ma n ar e direc t effect s o n bloo dvessel s o r

whethe r th e effect s ar e secondar y t o rena l effects . Ther e ar e conflictin g report s regardin g whethe r lea dca n caus e atherosclerosi s i n experimenta l animals . Sroczynsk i e t al. 41 7 observe dincrease d seru mlipoprotei n an dcholesterol , an dcholestero l deposit s in th e aorta s o f rat s an drabbit s receivin g larg e dose s o f

lead . O n th e othe r

hand , Prerovska, 41 8 usin g simila r

dose s o f lea dgive n ove r

a n eve n longe r perio do f

time , di dno t

produc e atheroscleroti c le

sion s i n rabbits . Structura l an dfunctiona l change s o f th e myocar diu mhav e bee n note din childre n withacut e lea d poisoning , but , t o date , th e exten t o f suc hstudie s ha s bee n ver y limited . Case s hav e bee n describe din adult s an di n children , alway s withclinica l sign s o f poisoning . Ther e is , o f

course , th e possibilit y tha t th e coexistenc e o f

lea dpoisonin g an dmyocarditi s i s coincidental . I n man y case s in whic hencephalopa

th y i s present , th e electrocardiographi c abnor

malitie s disappeare dwit hchelatio n therapy , sug gestin g tha t

lea dma y hav e bee n th e origina l etiologi

ca l factor. 41942 1 Silve r an dRodriguez-Torres 42 1 note dabnorma l electrocardiogram s in 2 1 o f 3 0 childre n (7 0 percent ) havin g symptom s o f lea dtox icity . Afte r

chelatio n therapy , th e electrocar

diogram s remaine dabnorma l i n onl y fou r

(1 3 per cent ) o f th e patients . Electro n microscop y o f th e myocardiu mo f

lead-intoxicate drat s ha s show n diffus e degenerativ e changes. 42 2 I n arevie w o f fiv e fata l case s o f

lea dpoisonin g i n youn g children , degenerativ e change s i n hear t muscl e wer e reporte d t o b e th e proximat e caus e o f death. 9 1 I t

i s no t clea r tha t suc hmorphologica l change s ar e aspecifi c respons e t o lea dintoxication . Kosmide r an d Petelnz 42 3 examine d3 8 adult s ove r 4 6 year s o f

ag e wit hchroni c lea dpoisoning . The y foun dtha t 6 6 per cen t ha delectrocardiographi c changes , whic hwa s 4 time s th e expecte drat e fo r tha t ag e group . Makase v an dKrivdina 42 4 observe datwo-phas e chang e in th e permeabilit y o f bloo dvessel s (first , in

crease dpermeability ; second , decrease dper meability ) in rats , rabbits ; an ddog s tha t receive da solutio n o f

lea dacetate . A phas e chang e in th e con ten t o f catecholamine s in th e myocardiu man din th e bloo dvessel s wa s observe din subacut e lea dpoison

in g i n dogs. 42 5 Thi s effec t appear s t o b e alin k

in th e comple x mechanis mofth e cardiovascula r patholog y o f lea dpoisoning . 11.1 1 TH E IMMUNOLOGI C SYSTE M Recen t report s sugges t

tha t exposur e t o lea dma y interfer e withnorma l susceptibilit y t o infection . Hemphil l e t

al. 42 6 foun dtha t

mic e injecte dwith , subclinica l dose s o f

lea dnitrat e fo r

3 0 day s showe d greate r susceptibilit y t o challeng e withSalmonella typhimurium tha n control s tha t receive dasalin e in

jectio n containin g n o lead . Sely e e t al. 42 7 foun dtha t rat s injecte dwit hlea dacetat e (minima l effectiv e dos e o f 1 mg/10 0 g bod y weight ) wer e susceptibl e t o avariet y o f

bacteria l endotoxin s (toxin s produce d b y th e bacteri athemselves ) t o whic hthi s specie s i s ordinaril y resistant . Administratio n o f lea dacetat e in drinkin g wate r

t o mal e mic e fro m4 week s o f ag e t o sacrific e at

9 t o 1 2 week s ol dincrease dth e toxi c respons e o f

th e mic e t o 5 classe s o f viruse s agains t whic hit wa s tested. 428

- 42 9 Thes e viruse s wer e a n RN A picornaviru s (encephalomyocarditis) , aDN A herpesviru s (pseudorabies) . an RN A leukemi aviru s (Rausche r

leukemia) , an dRN A arboviru s B (St . Loui s encephalitis) , an dan RN A arboviru s A (wester n encephalitis) . Amon g th e factor s tha t may b e involve din pro ducin g thi s decrease dresistanc e t o infectio n i s th e decrease dproductio n o f antibodies . William s e t al. 43 0 reporte dtha t

lea dbind s antibodie s in vitro an d coul dpotentiall y d o s o in vivo. Chroni c exposur e t o mic e o f lea dacetat e in drinkin g wate r produce da significan t

decreas e in antibod y synthesis , particu

larl y gamm aglobulins. 43 1 Phagocytosi s (ingestio n o f foreig n materia l b y a cel l specialize dfo r

tha t purpose ) b y alveola r macrophage s i s believe dt o b e a n importan t ste p in th e remova l o f

dus t particle s an dbacteri afro mth e respirator y tract . Consequently , th e activitie s o f alveola r macrophage s ar e importan t aspect s o f pulmonar y defense . Bingha me t al. 43 2 foun dtha t

th e continuou s inhalatio n o f lea dsesquioxid e aeroso l (1 0 ug/m 3 t o 150 ug/m 3 ) b y rat s fo r 3 t o 1 2 month s significantl y reduce dth e numbe r o f alveola r macrophages . Electro n microscopi c examinatio n o f th e lung s o f

rat s tha t

ha dinhale dparticulat e lea d oxid e (20 0 ug/m 3 ) fo r

1 4 day s reveale dultrastruc

11-5 3P.9 8

tura l damag e (mitochondri aan dendoplasmi c reticulum ) t o th e alveola r macrophage s an dth e typ e I alveola r

epithelia l cells . Biochemically , acon siderabl e los s in th e activit y ofth e benzopyren e hy

droxylatin g enzym e in th e alveola r macrophage s wa s observe db y Bruc he t al. 43 3 Fe w studie s hav e bee n mad e o f th e effect s o f

lea d o n th e immunologi c syste min man . Reigar t an d Graber 43 4 studie d1 2 preschoo l childre n havin g ele

vate dfre e erythrocyt e protoporphyri n an dbloo d level s 2 4 0 figldl

an dseve n nonlead-burdene d childre n fo r

evidenc e o f

impairmen t

o f thei r im

munologica l responses . The y foun dn o difference s betwee n th e contro l grou p an dth e lead-expose d grou p wit hreferenc e t o complemen t levels , t o im

munoglobulins , o r

t o anamnesti c respons e t o th e tetanu s toxoi dantigen . Hicks 43 5 point s ou t

tha t ther e i s anee dfo r systemati c epidemiologica l studie s o n th e effect s o f elevate dlea dlevel s o n th e incidenc e o f infectiou s disease s in man . Th e paucit y o f informatio n canno t suppor t th e formulatio n o f

an y dose-respons e rela

tionshi p a t

thi s time . 11.1 2 TH E GASTROINTESTINA L SYSTE M Coli c i s usuall y aconsisten t earl y sympto mo f

lea d poisoning , warnin g o f

muc hmor e seriou s effect s tha t ar e likel y t o occu r

wit hcontinue dan dprolonge d lea dexposure . Althoug hmos t commonl y see n in in

dustria l exposur e cases , coli c i s als o alea dpoisonin g sympto mpresen t

in infant s an dyoun g children . Beritic 43 6 reporte do n th e case s o f 1 3 o f 6 4 me n expose do n thei r

job s t o occupationa l level s o f lead . Th e 1 3 ha dcolic , probabl y lea drelated , an dcon stipation . The y ha dbloo dlea dlevel s rangin g fro ma littl e les s tha n 4 0 t o 8 0 ug/d l a s determine db y polarography , atechniqu e whic htend s t o yiel d value s lowe r

tha n th e actua l bloo dlevels . Th e diag

nosi s o f lead-cause dcoli c wa s supporte db y finding s o f hig hurinar y coproporphyrin , excessiv e basophili c stippling , reticulocytosis , an dsom e degre e o f anemia , al l o f

whic har e othe r

clinica l sign s o f

lea d poisoning . Althoug hthes e symptom s ar e wel l documente din th e literature , ther e ar e insufficien t dat ab y whic ht o establis hadose-respons e relationshi p fo r a n effec t o f lea do n th e gastrointestina l system . 11.1 3 REFERENCE S FO RCHAPTE R1 1 1 . Ulmer , D . D . an dB . L . Vallee . Effect s o f lea do n biochemica l systems . In: Trac e Substance s i n Environmen

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n som e chroni c intoxication s wit hindustria l poison s (lead , carbo n disulphide , benzene) . Git . Tr . Prof . Zabol . 75(0:32-36 , 1969 . 414 . Vigdortchik , N . A . Lea dintoxicatio n i n th e etiolog y o f hy

pertonia . J . Ind . Hyg . 77:1-6 , 1935 . 415 . Cramer , K . an dL . Dahlberg . Incidenc e o f hypertensio n amon g lea dworkers . Brit . J . Ind . Med . 25:101-104 , 1966 . 416 . Dressen.W . C , T.J . Edwards , W.H . Reinhart , R . T . Page , S . H . Webster , D . W . Armstrong , an dR . R . Sayers . Th e contro l o f

lea dhazar di

n th e storag e batter y industry . Publ . Health . Bull . (Wash. ) No . 262 , 1941 . 417 . Scroczynski , J. , K . Zajusz , S . Kossmann , an dA . Wegill . • Effec t o f experimenta l lea dpoisonin g o n th e developmen t o f arteriosclerosis . Pol . Arch . Med . Wewn . 58:641-646 , 1967 . 418 . Prerovska , J . Einflus s vo n Ble i au f biochemisch e Veran

derunge n imSeru mun dVeranderunge n i n de r Aderwan t imHinblic k

au f Atherosklerose . in: Proc . o f th e Int' l Symp : Environmenta l Healt hAspect s o f Lead , Amster

dam , 2- 6 October , 1972 . Luxembourg , Commissio n o f th e Europea n Communities . 1973 . p . 551-558 . 419 . Myerson , R . M . an dJ . H . Eisenhauer . Atrioventricula r conductio n defect s i n lea dpoisoning . Am . J . Cardiol . 77:409-412 , 1963 . 420 . Freeman , Rreversibl e myocarditi s du e t o chroni c lea d poisonin g i n childhood . Arch . Dis . Child . 40:389-393 , 1965 . 421 . Silver , W . an dR . Rodriguez-Torres . Electrocardiographi c studie s i n childre n wit hlea dpoisoning . Pediatr . 47:1124-1127 , 1965 . 422 . Asokan , S . K. , C . A . Malpass , Jr. , an dF . T . Ulmer . Cir

culation . 44(Suppl . 2):101-104 , 1971 . 423 . Kosmider , S . an dT . Petelnz . Zin i n y elektrokar

diograficzn e u startazyc hoso b prezewelekly m aawodowy mzatrueie molowiem . Pol . Arch . Med . Wewn . 52:4.37-442 , 1962 . 424 . Makasev , K . K . an dL . V . Krovdina . Statu s o f th e in

terstitia l tissue s o f

vascula r

wall s an dthei r

penetratio n unde r lea dpoisoning . Tr . Nauen-issl . In-t aKraev . Pat . Kaz . SSR . 25:11-13 , 1972 . 425 . Mambeeva , A . A . an dI . D . Kobkova . Th e concentratio n o f catecholamine s in tissue s o f th e cardiovascula r

syste m i n experimenta l lea dintoxication . Izv . Akad..Nau k Kazahst . SSR . Ser . Biol . 7:77-82 , 1969 . 426 . Hemphill , F. , M . L . Kaerberle , an dW . B . Buck . Lea dsup pressio n o f

mous e resistanc e t o Salmonella typhimurium. Science . /

72:1031-1032 , 1971 . 427 . Selye , H. , B . Tuckweber , an dL . Bertok . Effec t o f lea dace tat e o n th e susceptibilit y o f rat s t o bacteria l endotoxins . J . Bacteriol . 97:884-890 , 1966 . 428 . Gainer , J . H . Activatio n o f Rausche r

leukemi aviru s b y metals . J . Natl . Cance r Inst . 57:609-613 , 1973 . 429 . Gainer , J . H . Lea daggravate s vira l diseas e an drepresse s th e antivira l activit y o f interfero n inducers . Environ . Healt hPersp . Exp . lss . 7: 1 13-119 , 1974 . 430 . Williams , H . W. , W . T . Caraway , an dW . A . DeYoung . In

activatio n o f

antibodies : A causativ e facto r o f brai n patholog y i n acut e lea dintoxication . Arch . Neurol . Psy

chiat . 72:579-582 , 1954 . 431 . Koller , L . D . an dS . Kovacic . Decrease dantibod y forma

tio n i n mic e expose dt o lead . Nature . 250:148-150 , 1974 . 432 . Bingham , E. , E . A . Pfitzer , W . Barkley , an dE . P . Redford . Alveola r macrophages : Reduce dnumbe r i n rat s afte r prolonge dinhalatio n o f lea dsesquioxide . Science . 762:1297-1299 , 1968 . 433 . Bruch , T. , A . Brockhaus , an dW . Dehnen . In: Proceeding s o f th e Internationa l Symposium : Environmenta l Healt h Aspect s o f

Lead , Amsterdam , Octobe r 2-6 , 1972 . Luxem

bourg , Commissio n o f th e Europea n Communities , p . 221-230 . 434 . Reigart , J . R . an dC . D . Graber . Evaluatio n o f th e humora l immun e respons e o f childre n wit hlo w leve l ex posure . Bull . Environ . Contam . an dToxicol . 16: 1 12-117 , 1976 . 435 . Hicks , R . M . Air-born e lea da s an environmenta l toxin . Chem-Biol . Interact . 5:361-390 , 1972 . 436 . Beritic , T . Lea dconcentratio n foun di n huma n bloo din associatio n wit hlea dcolic . Arch . Environ . Health . 25:289-291 , 1971 .

11-6 5P.1 0



## 12 . ASSESSMEN T O F LEA D EXPOSURE S AN D ABSORPTIO N

I N HUMA N POPULATION S 1 2 1 INTRODUCTIO N Althoug hepidemiologica l studie s provid e th e mos t directl y relevan t

dat afo r

settin g ambien t

ai r qualit y standards , suc hinvestigation s ar e subjec t t o methodologica l an dpractica l difficulties . O f mos t interes t ar e studie s relatin g ambien t ai r lea dex posure s directl y t o huma n healt heffect s in variou s populatio n groups . Unfortunately , few suc hstudie s exist . Standard s setting , then , mus t rel y o n con structin g (1 ) th e linkag e betwee n exposure s t o en vironmenta l source s o f

lea dan dth e incorporatio n o f lea dfro mthos e source s in variou s segment s o f th e populatio n a s measure db y bloo dlea dlevel s an d(2 ) th e relationshi p betwee n level s o f lea di n th e bloo d an dassociate dhealt heffects . Thi s chapte r

wil l examin e th e detail s o f studyin g bloo dlea dlevel s i n huma n populations . Include d wil l b e a n examinatio n o f th e statistica l considera

tion s o f suc hinvestigation s a s wel l a s adiscussio n o f th e characteristic s o f

th e frequenc y distributio n o f bloo dlea dvalue s an do f ho w thes e ma y b e use da s tool s in settin g environmenta l standards . I n addi

tion , th e effect s o f

geographi c an ddemographi c variable s o n lea dburden s wil l b e considered , Finally , th e epidemiologica l an dclinica l studie s o n th e relationship s betwee n environmenta l lea dex posure s an dhuma n absorptio n wil l b e described , and , wher e available , quantitativ e estimate s o f thos e relationship s will b e presented . 12. 2 LEA D I N HUMA N POPULATION S I n thi s section , th e statistica l approache s fo r assessin g bloo dlea dlevel s in huma n population s wil l b e discussed , a s wil l thei r application s an dim

plications . Thi s discussio n will b e followe db y a descriptio n o f

finding s relatin g t o th e geographi c an ddemographi c distribution s o f bloo dlea dlevels . 12.2. 1 Statistica l Description s an d Implication s Man y survey s hav e describe dbloo dlea dvalue s i n huma n populations . No t unexpectedly , th e in

vestigators ' choice s o f

statistic s t o describ e centra l tendencie s an ddispersio n pattern s ar e no t uniform . Thi s lac k

o f uniformit y make s compariso n o f th e variou s studie s quit e difficult . Fo r example , centra l tendencie s ar e expresse da s eithe r arithmeti c o r geometri c means , an dth e measure s o f dispersio n als o vary . Ofte n th e arithmeti c mea n o f th e distribu

tio n i s muc hlarge r

tha n th e geometri c mean . 12.2.1. 1 FOR M O FTH EDISTRIBUTIO N O F BLOO D LEA D LEVEL S Severa l author s hav e eithe r suggeste do r

implie d tha t th e distributio n o f

bloo dlea dlevel s fo r an y relativel y homogeneou s populatio n closel y follow s a lognorma l distribution. 1 3 Lognormalit y ha s als o bee n note dfo r

othe r metals , suc ha s 90 S r

in bone s o f huma n populations. 4 Sne e ha s suggeste dtha t th e Pearso n syste mo f

curve s provide s aslightl y bette r fit fo r th e dat ao f

Aza r e t al . tha n th e lognormal, 5 bu t th e improvemen t

derive dfro mthi s syste mdoe s no t see msufficien t

t o warran t

th e us e o f

thi s little

know n technique . Yanke l e t al. 1 an dTeppe r

an d Levin 2 bot hfoun dthei r lea ddat at o b e lognormall y distributed . Furthe r

analysi s o f

th e Housto n stud y o f Johnso n e t

al., 6 th e Souther n Californi astud y o f Johnso n e t

al., 7 an dth e stud y o f Aza r e t al. 3 als o confirme dtha t

alognorma l distributio n provide da goo dfit t o th e data . Fo r

thes e reasons , muc ho f wha t i s presente din thi s chapte r i s base do n th e accep tanc e tha t

homogeneou s population s hav e alognor

ma l distributio n o f

bloo dlea dvalues . Th e lognorma l distributio n an dit s applicatio n t o biologica l measurement s ar e discusse db y severa l authors. 48

- 9 A variabl e i s sai dt o hav e alognorma l distributio n i

f th e logarith mo f

th e variable-i s nor mall y distributed . Becaus e o f th e skewe dnatur e o f th e lognorma l distribution , th e media n (50t hper centile ) i s amor e meaningfu l estimat e o f centra l ten denc y tha n th e arithmeti c mean . Fo r th e norma l dis

tribution , th e bes t

estimat e o f

th e media n i s X , th e simpl e arithmeti c mean . Forth e lognorma l distribu

tion , th e bes t

estimat e o f

th e media n i s th e geometri c mea n (GM) : 12- 1' *"*•*"" ' P.1 1

G M = Exp[ S (In(Xi))/n] . (12-1 )

i = 1 Th e standar ddeviatio n o f th e logarithm s is : S = [1 (ln(X;)

- ln(GM)) 2 /n-l]"2 . (12-2 ) i = 1 Th e geometri c standar ddeviation , als o know n a s th e standar dgeometri c deviation , i s give n by :

GS D = Exp(S) . If onl y th e arithmeti c mean , X , an darithmeti c stan dar ddeviation , SD , ar e given , the n th e geometri c mea n an dth e geometri c standar ddeviatio n ca n b e estimate dby: 1 0

G M = X/( l + SD 2 /X 2 )'' 2 (12-3 ) an d GS D Exp[(ln(SD 2 /X 2 + l))'/2] . (12-4 ) Th e geometri c standar ddeviatio n mus t b e in

terprete ddifferentl y tha n th e arithmeti c standar d deviation . Usin g th e SD , approximatel y 6 8 percen t o f th e populatio n wil l fal l betwee n (mea n - SD ) an d (mea n + SD) . Thes e sam e limit s fo r th e lognorma l distributio n becom e GM/GS D an d(GM)(GSD) . Fo r example , i

f apopulatio n ha s ageometri c mea n bloo dlea dleve l o f

2 0 withaGS D o f

1.3 , the n 9 5 percen t o f th e populatio n will hav e bloo dlea dlevel s betwee n 20/(1.3) ' % an d(20)(1.3)'- 9 6 o r 11.9 6 an d 33.45 . 12.2.1. 2 PERCENTIL EESTIMATE S O FTH E LOGNORMA LDISTRIBUTIO N Fro mth e G M an dGSD , estimate s o f percentile s o f th e lognorma l distributio n ca n easil y b e obtaine d eithe r numericall y o r

graphically . Numerically , th e pthpercentile , X i s estimate db y

X p = (GM)(GSD) Z P(12-5 ) wher e z i s th e z valu e fro mastandar dnorma l table . Th e followin g value s ar e ofte n used : Percen t Percen t Percen t 1 2. 5 5 1 0 p -2.32 6 -1.96 0 -1.64 5 -1.28 2 2 5

5 0 7 5 9 0 p -.67 4 0.00 0 0.67 4 1.28 2 9 5 97. 5 9 9 99. 9 p

1.64 5 1.96 0 2.32 6 3.09 0 Anothe r metho do f

obtainin g percentil e estimate s i s agraphica l on e usin g lognorma l probabilit y paper . On e poin t

i s place dwher e th e geometri c mea n intersect s th e 50t hpercentile . A secon dpoin t i s place dwher e (GM ) (GSD) 2 32 6 intersect s th e 99t h percentile . A lin e draw n throug hthes e tw o point s give s th e estimate dcumulativ e frequenc y distribu

tion . Figur e 12-1 , fo r

example , i s draw n wit han assume dgeometri c standar ddeviatio n o f 1.3 .

Q 2 0 —

GM-GEOMETRI C MEA N GS D - GEOMETRI C STANDAR D DEVIATIO N Illl l ! I 1 I I I I 9 5 5 0 PERCEN TO F POPULATIO N WIT H BLOOD.LEA D LEVEL S

EXCEEDIN G GIVE N VALU E Figur e 12-1 . Estimate d cumulativ e distributio n o f bloo d lea d level s lo r population s i n whic h th e geometri c mea n leve l i s 15 , 25 , o r 4 0 M9/dl . Fro mthi s descriptio n o f th e distribution , esti

mate s ca n b e obtaine do f th e percentag e o f

bloo d lea dvalue s expecte dt o excee dan y give n leve l for an y give n geometri c mea n bloo dlea dlevel . Fo r ex ample , (Figur e 12-1 ) in th e population s wit h geometri c mea n bloo dlea dlevel s o f 15 , 25 , an d4 0 Aig/d l whol e blood , 0.1 , 10 , an d6 8 percent , respec tively , wil l hav e bloo dlea dlevel s exceedin g 3 5 Mg/dl . A s state dabove , Figur e 12- 1 wa s draw n wit ha GS D o f 1.3 . Th e effec t

o f varyin g th e geometri c standar ddeviation s o n th e percentag e exceedin g a specifie dbloo dlea dvalu e i s show n in Figur e 12- 2 becaus e th e valu e o f

th e GS D ha s bee n show n t o var y acros s studie s (Tabl e 12-1) . A marke deffec t ca n be . noted . I t i s ver y important , therefore , t o b e sur e o f

10 0 8 0 ; I I 11Illll

^ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 IK -

G M = GEOMETRI C MEA N — GS D • = GEOMETRI C STANDAR D DEVIATIO N — 1 MINI - O 1 0 S 8

PERCEN TO F POPULATIO N WIT H BLOOD-LEA D LEVEL S EXCEEDIN G GIVE N VALU E Figur e 12-2 . Estimate d cumulativ e distributio n o l bloo d lea d level s lo r population s havin g a geometri c mea n bloo d lea d leve l o f 2 5 Mg/dl , bu t geometri c standar d deviation s o l 1.2 , 1.3 , o r 1.5 . 12- 2P.1 2

th e valu e use dfo r

th e geometri c standar ddeviatio n i f th e lognorma l distributio n i s t o b e use din settin g environmenta l standards . Becaus e mos t

bloo dlea ddat ahav e bee n reporte d a s arithmeti c mean s an dstandar ddeviations , an d becaus e th e ra w dat aar e no t generall y available , thi s chapte r wil l us e th e ter m"mean " fo r arithmeti c mean . Th e arithmeti c standar ddeviations , whe n available , wil l b e identified . If th e geometri c mean s ar e available , the y will b e reporte da s geometri c mean s withth e geometri c standar ddeviatio n pro vided . TABL E 12-1 . ANALYSI S O F VARIANC E FO R TH E LOGARITHM S O F BLOO D LEA D VALUE S FO R SELECTE D STUDIE S (Geometri c standar d deviation s give n i n parentheses )

Stud y Idaho ' Seve n Cit yStudy ? Souther n California-Males 7 Souther n California-Females 7 Houston 6 Azar 3 Populatio n siz e 87 9 190 8 64 107 189 149 Replicate s

pe r observatio n 3 1 2 2 2 2- 8 Numbe r

o l duplicate s 16 b 17 1 64 107 189 NA C Populatio n

variance 3 0.19 0 (1.55 ) 0.09 0 (1.35 ) 0.22 4 (1.60 ) 0.18 3 (1.53 ) 0.18 2 (1.53 ) 0.14 8 (1.47 ) Withi n grou p

variance 3 0.072 (1.31 ) 0.082 (1.33 ) 0.18 1 (1.53 ) 0.16 7 (1.51 ) 0.06 9 (1.30 ) 0.09 9 (1.37 ) Measuremen t

varianc e 0.01-2 " (1.12 ) 0.06 3 (1.28 ) 0.21 6 (1.59 ) 0.14 1 (1.45 ) 0.094 (1.36 ) 0.04 9 (1.25 )

a Include s measuremen t variation . D Base d o n a separat e Cente rfo rDiseas e Contro l versu s Idah o compariso n o f 1 6 sample s o f 1975 data , whic h ar e differen t fro m th e 1974 dat a fo rth e Idah o study. 1 Th e estimate s o f populatio n an d withi n grou p varianc e com e fro m th e origina l study . cNo t available . 12.2.1. 3 VARIATIO N I N BLOO D LEA D VALUE S Th e tota l variatio n i n bloo dlea dvalue s fo r an y stud y i s compose do f

thre e varianc e components : (1 ) betwee n group , (2 ) withi n grou p o r individual , an d (3 ) metho dvariation . Th e metho dvarianc e result s fro mbot hsamplin g an danalytica l measuremen t variations . Th e withi n grou p varianc e result s fro m th e differenc e in biologica l respons e amon g in

dividual s wit hth e sam e exposur e a s wel l a s demographi c difference s i n age , sex , race , socioeconomi c status , an denvironmenta l back

groun do f

th e individual s in agroup . Th e withi n grou p varianc e i s ameasur e o f th e homogeneit y o f peopl e in agroup , bu t als o include s metho d variance . Th e betwee n grou p varianc e result s fro m th e difference s i n th e compositio n o f peopl e i n a group , suc ha s polic e officer s o r housewives . I n studyin g th e effec t

o f lea dexposur e o n bloo dlea d levels , i t i s necessar y t o separat e thes e source s o f variatio n t o kno w whethe r th e stud y result s ar e meaningful . I f

th e bloo dlea dsamplin g an danalysi s error s ar e large , an y effect s o f differen t

lea dex posur e ma y no t b e seen . I n asimila r

manner , if

th e grou p chose n fo r

astud y i s no t

homogeneous , th e withi n grou p varianc e ma y b e s o larg e tha t th e difference s i n bloo dlea dvalue s canno t b e inter

prete da s resultin g fro mexposure . Th e source s o f variatio n ar e estimate din Tabl e 12- 1 fo r severa l studie s fo r

whic hth e ra w dat awer e available . Th e variatio n i s expresse di n term s o f th e natura l logarithm s o f

th e bloo dlea dvalues , an dth e cal

culation s wer e mad e usin g standar danalysi s o f varianc e techniques . Th e variance s ar e converte dt o geometri c standar ddeviation s an dthes e value s ar e show n i n parentheses . Tabl e 12- 1 show s tha t

alarg e portio n o f

th e tota l variatio n i s cause db y measuremen t variation , ex cep t possibl y fo r

th e Idaho 1 study . Th e measuremen t variatio n wa s unusuall y larg e fo r th e Souther n Californi astudy, 7 suggestin g tha t result s fro mthi s stud y shoul db e viewe dwit hcaution . Excep t fo r th e Souther n Californi astudy , th e GS D fo r withi n grou p variatio n wa s consistentl y nea r 1.3 . Thi s numbe r

in

clude s bot hbiologi c an dmeasuremen t variation . I t i s possibl e fo r

th e measuremen t

variatio n t o excee d 12- 3P.1 3



### th e withi n grou p variatio n i f ther e i s more than on e readin g per

individual , however , a s wa s th e cas e i n bot hth e Souther

n Californi aandHousto n studies . 

### 12.2.1. 4 PROBLE M O F FALS E EXCEEDENCE S Lucas 1 1 

### ha s describe daproble mtha t he term s "fals e exceedences. " Fo r

example , alognormal dis

tributio n wit

hageometri c mea

n o f 2 5 an da geometri c standar ddeviatio n o f 1. 3 will hav e 3. 7 percen t o f th e distributio n abov e 40 . A s ahypotheti

ca l example , i

f half o f th e variatio n i s cause db y measurement

variation , the n th e "true " distributio n woul dhav e ageometri c standar ddeviatio n o f 1.2 andwoul dhav e only 0. 6 percent o f th e distributio n abov e 40 . Fals e exceedence s become areal proble mi f a threshol dvalue, suc

has 40 , i s determine dfro m source s o f dat alackin g alarg e measurementvariation . I n suc hcases , th e estimate dpercentag e o f th e distributio n abov e afixedlevel will be a n over estimate a s shown i

n th e previou s paragraph . I t i s ex tremel y difficult

t o obtai n more accurat e estimate s becaus e th e appropriat e varianc e ca n only b e esti

mate dindirectl y andonly i n case s wher

e ther e ar e replicat e measurement s o n th e same individual . If , however , th e threshol ditself i s estimate dfro

mdat a havin g thi s same measurement variation , the n th e proble mi s more difficult . In suchcases , th e ob

serve dvariance s includin g measurement variatio n ma y b e more appropriate . A s th e technolog y o f measurement

improves , th e proble mwill become muchles s significant . 12.2. 2 Geographi cVariability in Huma n Bloo d Lea d Level s Numerou s studie s hav e been conducte dthrough

ou t th e worl destablishin g mea n bloo dleadcon centration s fo

r variou s remote , rural , suburban , an d urban populations . B

y examinin g th e difference s amon g th e observe dlevel s acros s thes e populations , inference s ca

n b e draw n concernin g th e ubiquit y o f leadexposure s a s well a s thei r relativ e magnitudes . A wor dof caution , however , mus t

b e inserte dhere . Man y o f thes e dat ahav e been collecte dover a perio do f tim e i n whichmeasurement

technolog y fo

r bloo dleaddetermination s ha s change dan dim

proved . Also , sometime s neither th e method s o

f analysi s no r

th e samplin g schem

e usedhav e been re ported . Studie s o f remot e population s hav e been usedt o estimate th e natura l backgroun dbloo dleadlevel fo r humans. 121 5 

### Likewise , studie s comparin g eithe r rura l o r suburban population s hav e bee n usedt o es tablis hth e effect of urban livin g o n bloo dlead levels . Al l thes e studies , however , ca n b e usedt o demonstrat e th e broa dvariety of population s i

n whichleadfro

mal l environmenta l source s ha s been foundi n people . Only afe w studies 121 5 

### hav e focusedon remot e populations . Goldwate r

andHoover 1 2 

### conducte da n internationa l study o

f urban an drura l population s i n whichinvestigator s fro m1 4 countrie s partici

pated ; only non-occupationall y expose dadult s wer e studied . On e laborator y di dal l th e chemica l analyses . Som

e o f thes e population s —Ne

w Guine a aborigines , fo

r exampl e —wer

e thought

t o b e remot e fro

mth e effects o

f industrialization . Th e mea n an dstandar ddeviation s o f bloo dleadfor

th e aborigines , however , wer e 2 2 an d5 /ug/dl , respec tively . Examinatio n o

f thei r livin g habit s coul dshed no ligh t on th e source s o

f thi s lead . I

n contras t

t o this , urban resident s fro

mPer u i n th e sam e study ha d amea n o f 7 /ig/d l an dastandar ddeviatio n o f 5 Mg/dl . Stopps 13



### - 1 4 

### reporte ddat ao n remote populations . Tabl e 12- 2 present s th e bloo dleadmean s a s rangin g fro m2 3 t o 12/ug/10 0 g . I n contras t

t o th e finding s o

f Goldwate r

an d Hoover 1 2 

### an dStopps, 131 4 

### Hecker e t al. 1 5 

### i n amore recent study o f Amazo n Rive r

Basin Indians , using anodi c strippin g voltammetry , foundamea n bloo d leadof 0.8 3 figldl

wit hastandar ddeviatio n of

0.5 9 i n 9 0 subjects . Th e urinary level s were no t quit e a s lo w a s th e bloo dlead s (mean , 7. 9 /ug/dl ; SD , 5.7) , bu t stil l ar e low i

n compariso n wit

hth e value s re porte di n Goldwate r

an dHoover. 1 2 TABL E 12-2 . BLOO D LEA D LEVEL S O F REMOT E

POPULATIONS 13 - 1 4 Population s Brazilia n Indian s Marshal l Islander s Peruvia n Indian s Islander s of f Australi a Bushme n Ne wGuine a native s Eas t African s Sampl e siz e 1 1 3 3 3 9 2 8 6 8 6 7 6 3 Bloo d lead .

ug/10 0 g 2 3 2 3 1 8 17. 5 1 6 1 3 1 2 

### A number

o f studie s hav e specifically contraste d bloo dleadresult s between rural , suburban , an dur ba n populations. 2162 1 

### Tw o o f th e methodologicall y bette r studie s ar e thos e o

f Teppe r an dLevin, 2 

### an d Nordman. 1 6 

### Teppe r

an dLevin 2 

### conducte dastudy of th e bloo dleadlevel s o

f 1 1 group s o

f housewive s fro m8 U.S . metropolitan areas . Thre e o f these , Chicago , Ne

w York , an dPhiladelphia , hadurban

12- 4P.1 4

subura n compariso n groups . Tabl e 12- 3 display s th e result s o f th e contrast s betwee n thos e group s a s cal

culate db y Hasselbla dan dNelson. 2 2 I n ever y case , a significan t

differenc e wa s obtained . TABL E 12-3 . AG E AN D SMOKING-ADJUSTE D GEOMETRI C MEA N BLOO D LEAD S I N URBA N VERSU S SUBURBA N

AREA S O F THRE E CITIE S

Cil y Chicago , I L Philadelphia , P

A Ne wYork . N Y Thre e citie s togethe r Urba n 17.5 5 20.1 2 16.4 7 18.0 5 Bloo d Lead , ug % Suburba n 14.02 17.8 8 15.2 4 15.7 1 Urba n exces s

3.5 3 2.2 4 1.2 3 2.34 Significan t

>0.0 1 >0.0 1 >0.0 1 >0.0 1 Nordman 1 6 studie daserie s o f population s in Fin

lan dincludin g downtow n urban , suburban , an d rura l populations . N o statisticall y significan t difference s wer e observe dbetwee n urba n an drura l o r suburba n residents . But , interestingly , non e o f th e population s studied , whic hinclude dtraffi c police

men , streetsweepers , downtow n Helsink i residents , an drura l controls , ha damea n bloo dlea dleve l tha t exceede d13. 5 figldl. Othe r studie s permittin g urba n rura l comparison s includ e thos e o f

Hofreute r

e t al., 1 7 Creaso n e t

al., 1 8 Scanlon, 1 9 Gershani k

e t al., 2 0 an dCohe n e t

al. 2 1 Hofreute r

e t al., 1 7 in 1960 , collecte dbloo dsample s fro mabou t

12 0 peopl e in eac ho f 6 citie s an dfro m 16 2 peopl e i n arura l are a(centra l Ohio) . Tabl e 12- 4 display s th e result s o f

thes e comparisons . I n al l ur ba n surve y sites , th e mea n bloo dlea dleve l wa s sig

nificantl y highe r

tha n in th e rura l surve y sites . TABL E 12-4 . BLOO D LEA D CONCENTRATION S I N SI X URBA N AN D ON E RURA L POPULATIO N

Surve ysit e Ne wOrleans , L

A Chicago , I L Ne wYork , N Y Cincinnati , O H Dallas , T X Denver , C O Rura l No . o l sample s 130 9 7 11 2 137 12 8 13 1 16 2 Mea n

bloo d lead . jjg/100 g 2 2 2 0 2 0 2 0 1 8 1 9 1 4 Urba n

exces s 8 6 6 6 4 5 Creaso n e t

al. 1

- 8 studie dmilitar y recruit s in th e Chicag o are aa t

th e tim e o f

thei r induction . B y th e ver y natur e o f

th e sample , onl y youn g mal e adult s wer e included . Further , analysi s wa s restricte dt o thos e havin g live da t

th e sam e hom e addres s fo r tw o o r mor e years . Th e populatio n wa s broke n dow n b y rac e an dthre e residentia l locations , namel y urban , suburban , an doutstate . Media n bloo dlevel s fo r white s wer e 22 , 20 , an d3 6 figldl fo r th e urban , suburban , an doutstat e populations , respectively .

Scanlon 1 9 reporte do n umbilica l cor dbloo dlea d level s fo r infant s bor n t o Bosto n are awomen . Mea n bloo dlea dlevel s fo r

urba n infant s wer e 22. 1 /ug/d l compare dwit h18. 3 /ug/d l fo r th e suburba n newborn . Thi s differenc e wa s no t statisticall y signifi

cant . Gershani k

e t al. 2 0 studyin g alarge r

sampl e o f

cor d blood s in Shreveport , Louisiana , however , foun da statisticall y significan t

differenc e betwee n urba n an d suburba n infan t

cor dbloo dlea dlevels , 9. 7 ± 3. 9 versu s 8. 3 ± 2. 4 /xg/dl , respectively . Cohe n e t

al. 2 1 reporte do n arural-urba n com pariso n fo r

children , age d1 t o 5 years , livin g in 2 rura l countie s an di n Hartford , Connecticut . Althoug hth e 2 sample s wer e adequatel y matche do n age , ther e wa s amajo r

racial/ethni c differenc e — th e urba n populatio n bein g eithe r blac k o r Puert o Rica n an dth e rura l primaril y white . Th e mea n an dstan dar ddeviatio n o f

th e bloo dlea dconcentration s wer e 32. 7 ± 14. 8 an d22. 8 ± 11. 0 fo r th e urba n an d rura l populations , respectively . Som e o f thes e sam e studies , a s wel l a s others , ca n b e use dt o discer n awide r pictur e o f

th e variabilit y o f bloo dlea dlevels. 12141 7 I n th e Goldwate r an d Hoove r study, 1 2 urba n populatio n mea n bloo dlea d level s wer e foun dt o rang e fro m7 t o 2 5 figld\, wherea s th e mea n fo r

rura l area s range dfro m9 t o 3 2 /xg/dl . Th e wid e rang e o f mean s i n bot hpopula

tio n type s suggest s tha t lea dca n b e foun di n man y locations . Nordman 1 6 reviewe dth e availabl e literatur e o n bloo dlea dlevel s an dconclude dtha t "th e Pb- B mea n value s fo r

occupationall y unexpose drura l an d urba n population s rang e fro m1 0 t o 2 6 /ug/dl. " Ex

ception s t o thi s genera l rang e ar e found , however . Lower-than-usua l bloo dlea dlevel s hav e bee n re porte dfro msom e part s o f Swede n an dFinland . There , level s in wome n wer e foun dt o b e 1 0 /ug/dl. 16

- 2 3 O n th e othe r hand , higher-than-usua l bloo dlea dvalue s hav e bee n reporte dfro msection s o f Ital y an dFrance. 242 7 Zurl o e t al., 2 4 in particular , reporte dver y hig hbloo dlea dlevel s fo r adult s in th e Mila n area , urba n mea n o f 3 0 /xg/d l fo r

male s an d 23. 7 figldl

fo r females . Dat aobtaine dfro madult s withi n th e Unite d State s follo w asimila r pattern. 2172 8 I n dat afro m Teppe r an dLevin, 2 difference s wer e note din th e geometri c mea n bloo dlea damon g th e 1 1 popula

tion s o f housewive s studied . Th e lowes t bloo dlea d value s wer e foun din Houston , Texas , wit haG M an daGS D o f

12. 5 an d1.31 , respectively , wherea s th e highes t

wer e foun din Rittenhouse , asectio n o f 12- 5P.1 5



### Philadelphi a—G M an dGS D o f 20. 6 an d1.33 , respectively . In th e 196 0 Hofreuter

e t al . study, 1 7 

### bloo dsam ple s wer e collecte dfro

mpeopl e i

n si x metropolita n area s an don e rura l contro l site . Th e mea n bloo d leadvalue s varie dfro

m1 4 t o 2 2 /ug/10 0 g . Th e max imu mobserve dvalue s range dfro m3 8 t o 6 0 Mg/10 0 g . Kubot ae t al. 2 8 

### studie dbloo dleadlevel s i n mal e resident s o

f 1 9 intermediate-size dcitie s acros s th e Unite dStates . Mea

n bloo dlevel s were foundt o vary fro m7.2 5 /ug/d

l i n Lafayette , Louisiana , t o 20.3 4 figldl i n Jacksonville , Florida . Th e highes t reporte d value, 109.2 7 /xg/dl , occurre di n Fargo , North Dakota . A wide rang e i

n value s wa s reporte dfo r eachcity , th e larges t

bein g 5.9 1 t o 109.2 7 /xg/d l i n Fargo . Further , th e author s report thre e citie s wit

h mea n bloo dleadlevel s belo w 8.0 0 /ug/dl , namely Lubbock , Texas , 7.95 ; Geneva , Ne w York , 7.65 ; an dLafayette , Louisiana , 7.2 5 /xg/dl . Thes e low value s approximat e thos e foundi n part s o f Scan

dinavia. 1 6 

### Worker s a

t 2 3 DuPon t

Company plant s wer

e studie dover

a5-yea r period , 1967 throug h1971. 2 9 

### No time tren dwa s note dfor bloo dleadlevels , an d th e sample s wer

e poole dper

plan t fo r th e 5 years . Th e geometri c mea

n value s varie dfro

malow o

f 15. 5 /ug/10 0 g fo

r th e Ashland , Wisconsin , plan t t o a hig ho f 21. 6 /ug/100 g a

t th e Lo s Angeles , California , plant . Th e overal l geometri c mea n fo r th e 2 3 loca

tion s was 18. 2 /ug/10 0 g . Dat aaddressin g geographi c variatio n o f bloo d leadvalue s i

n childre n ar e no t

a s extensive . Fo r

th e Unite dStates , Fin e et

al., 3 0 

### Baker

e t al., 3 1 

### an d Joselo w e t al. 3 2 

### provide dth e bes t

availabl e infor

mation . Fin e e

t al. 3 0 

### studie d615 1 childre n age d1 t o 6 year s i n 1 4 intermediate-size dcitie s i n Illinoi s i

n 1971 . Bloo dleadvalue s (Tabl e 12-5 ) were deter

mine db y a n atomi c absorptio n technique . Mea n value s fo r citie s range dfro

m19. 8 t o 32. 9 figldl; th e mea n fo r al l 1 4 citie s was 25. 5 /ug/dl . Thes e value s ar e indicativ e o

f source s o f leadi n th e children' s en vironment . Baker et al. 3 1 

### determine dbloo dleadvalue s fo r 167 2 childre n age d1 t o 5 livin g i n 1 9 town s contain

ing smelter s an d3 contro l towns . Th e smelter com munitie s wer

e selecte dfo

r study becaus e they had not previousl y been subject

t o thoroug hinvestiga

tion . Bloo dleadvalue s wer e determine db

y a n atomi c absorptio n technique . Th e mea n bloo dleadlevel s fo

r th e leadan dcop per smelter town s di dno t

diffe r fro mthos e contro l towns , a s shown i

n Tabl e 12-6 . Th e childre n livin g TABL E 12-5 . MEA N BLOO D LEA D VALUE S FO R CHILDRE N I N 1 4 INTERMEDIATE-SIZE D CITIE S I N ILLINOIS , 1971 3 0

Cit y Auror a Springfiel d Peori a Eas t St . Loui s Decatu r Jolie t Roc k Islan d Eas t Molin e Harve yan d Phoeni x Eas t Chicag o Height s Chicag o Height s Robbin s Carbondal e Rockfor d Tota l No . O l childre n screene d 44 9 67 0 38 7 37 6 79 3 38 3 28 5 29 8 22 6 172 53 7 103 264 1,208 6,15 1 % o l city' s

childre n age s 1- 6 y r screene d 5.0 9 7.2 8 2.9 7 4.0 9 5.84 4.5 4 5.6 0 12.32 4.9 0 17.1 3 10.3 6 6.7 8 17.4 6 7.3 1 6.1 4 Mea n bloo d

lea d value , ug/d l 28. 2 31. 5 32. 9 28. 6 21. 5 27. 8 25. 0 23. 5 22. 6 27. 3 25. 2 22. 2 28. 5 19. 8 25. 5 

### i n zin c smelter

towns , however , showedsignificantly higher bloo dleadvalue s than th e othe r thre e groups . Th e lowes t

mea n bloo dleadvalue , 9.1 5 /ug/dl , was foundi n childre n fo

r McGill , Nevada , wherea s th e highes t mea n valu e was foundfo

r Bartlesville , Oklahoma, wit

h28.6 0 /ug/dl . Joselo w e t al. 3 2 

### compare dth e bloo dleadlevel s o f childre n aged3 t o 5 year s i n Newark , Ne

w Jersey , andHonolulu , Hawaii , i

n 1973 . Th e study include d 15 2 childre n who wer

e matche dfor

ag e an dse

x int o 2 group s o

f 7 6 fro meachcity . Th e mea

n bloo dlead valu e fo r th e Newar

k childre n wa s 2 8 /ug/dl , con siderabl y higher

than tha t

foun di

n Honolul u children , 1 7 /xg/dl . 12.2. 3 Demographi cVariable s an d Huma n Bloo d Lea d Level s Fewe r dat aar e availabl e t o evaluat e th e effects o f age , sex , an drac e on bloo dleadlevels . Childre n consistentl y develo p higher bloo dlead level s than d o adult s i

n th e same environmenta l set ting . In E

l Paso , Texas, 3 3 

### i

n 1972 , 7 0 percent

o f childre n 1 t o 4 year s ol dlivin g nea r aprimary lead , copper , an dzin c smelter

hadbloo dleadlevel s >4 0 /xg/dl , an d1 4 percen t

exceede d6 0 /ug/dl . I n childre n 5 t o 9 year s old , 4 5 percen t exceede d4 0 figldl, a s di d3 1 percen t o f measurement s i

n in

dividual s 1 0 t o 1 9 year s ol dan d1 6 percen t of thos e over 19 . In th e vicinit

y o f aprimary leadsmelter

i n Idah o i n 1974 , th e geometri c mea n bloo dleadlevel s shown i n Tabl e 12- 2 wer

e obtained. 1 

### A s ca

n b e see n fro mTabl e 12-7 , childre n under 1 0 year s o

f ag e consistentl y hadhigher

bloo dleadvalue s than olde r childre n an dadult s withi n th e same environment . 12- 6P.1 6

TABL E 12-6 . BLOO D LEA D LEVEL S (WHOL E BLOOD ) I N CHILDRE N I N U.S . SMELTE R AN D COMPARISO N TOWNS , 1975 3 1

Cit y No . o l sample s Mea n SE a G M GS D Percen t exceedin g 35 ug/d l Compariso n town s Albuquerque , N M Perryville , M O Safford , A Z Tota l Lea d smelte rtown s Bixby , M O Glover , M O Herculaneum , M O Tota l Coppe rsmelte rtown s Ajo . AZ Anaconda , M T Coppe rHill , T N Douglas , AZ Hayden , A Z Hurley , M N McGill , N V Miami , A Z Morenci , A Z Sa n Manuel , AZ Whit e Pine . M l Tota l Zin csmelte rtown s Amarillo . T

X Bartlesville , O K Corpu s Christi . T

X Monaco , PA Palmerton , PA Tota l 8 1 8 5 9 2 25 8 4 8 2 3 8 7 15 8 10 5 6 4 8 6 9 7 10 0 4 2 5 0 9 4 10 0 10 1 7 0 90 9 8 4 8 7 1 2 6 2 10 2 34 7 17.7 0

16.8 8 15.2 6 16.5 6 13.7 6 12.0 5 18.8 0 16.3 4 12.5 5 13.3 8 16.6 3 20.4 7 21.2 4 14.3 3 9.1 5 17.0 0 13.8 7 18.0 1 18.6 2 16.3 6 22.3 4 28.6 0 19.0 2 14.8 4 17.5 1 21.0 4 0.6 3

0.7 4 0.7 1 0.4 1 0.9 6 1.1 9 0.9 4 0.6 6 0.4 6 0.9 5 0.7 4 0.8 6 0.8 5 1.2 3 0.5 2 0.7 4 0.5 6 0.5 5 0.7 4 0.2 5 1.1 6 1.9 1 1.4 2 0.8 2 0.6 0 0.6 6 16. 8

15. 8 13. 8 15. 4 12. 4 11. 1 17. 2 14. 6 11. 7 11. 6 15. 4 18. 9 19. 9 12. 8 8. 9 15. 5 12. 9 17. 2 17. 8 14. 8 20. 9 23. 6 18. 4 13. 7 16. 5 18. 6 1.3 9

1.4 2 1.5 7 1.5 7 1.6 6 1.5 8 1.5 4 1.6 4 1.4 5 1.7 7 1.4 7 1.4 9 1.4 2 1.6 0 1.4 5 1.5 9 1.4 7 1.3 7 1.3 4 1.5 8 1.4 1 1.9 2 1.3 2 1.4 9 1.4 2 1.6 3 0. 0

2. 4 1. 1 1. 2 0. 0 0. 0 8. 0 4. 4 0. 0 1. 6 1. 2 3. 1 5. 0 4. 8 0. 0 3. 2 0. 0 1. 0 2. 9 2. 0 4. 8 31. 0 0. 0 1. 6 1. 0 9. 5 S E = standar d error . TABL E 12-7 . GEOMETRI C MEA N AN D GEOMETRI C STANDAR D DEVIATION S (I N PARENTHESES ) O F BLOO D LEA D LEVEL S BYAG E AN D STUD YSECTO R (-ug/dl ) Stud y secto r I I I II I <1 0 66(1.33 ) 47(1.30 ) 34(1.26 ) Age . year s 10-1 9 39(1.26 ) 33(1.23 ) 28(1.40 ) >2 0

38(1.32 ) 33(1.33 ) 30(1.35 ) Likewise , astud y o f

traffi c exposur e i n Dallas , Texas, 3 4 foun dmea n bloo dlea dconcentration s o f 1 2 t o 1 8 /xg/d l i n childre n a s contraste dwit h9 t o 1 4 figldl in adults , whe n exposur e level s ar e controlled . Simpso n e t

al. 3 5 summarize dth e result s o f 2 7 neighborhoo dscreenin g program s conducte d throughou t

th e Unite dState s in th e sprin g an dsum me r o f 1971 . The y foun dtha t childre n les s tha n 3 year s o f ag e ha dalowe r

rat e o f elevate dbloo dlea d tha n childre n olde r

tha n 3 years . O f

thos e unde r

3 years , 25. 8 percen t

ha dvalue s o f

2 40. 0 /xg/dl , wherea s 31. 4 percen t

o f thos e 3 year s o f

ag e o r olde r ha dvalues240.0/xg/dl . Ela me t al. 3 6 studie dpediatri c patient s in a Chicag o outpatien t

service . Th e proportio n o f childre n (Tabl e 12-8 ) withbloo dlea dvalue s 2 5 0 figldl varie dwithage ; th e proportio n ove r 5 0 figldl peake da t

1 8 t o 3 0 month s o f

age . TABL E 12-8 . PROPORTIO N O F CHILDRE N WIT H BLOO D LEA D VALUE S BETWEE N 5 0 AN D 9 9 /xg/dl , B YAGE ,

CHICAG01971-1975 3 6 Age . month s % Bloo d lea d 50lo99/jg/d l 6-1 7 18-3 0 31-4 2 43-5 2 55-6 6 2 4 4 0 1 6 1 2 7 A stud y o f

Philadelphi aghett o children 3 7 con ducte din 197 2 throug h197 3 provide s dat arelevan t t o th e relationshi p betwee n ag e an dbloo dlea dlevel . Th e stud y populatio n consiste do f 155 9 blac k childre n age d6 month s t o 1 8 year s o f age . Tabl e 12- 9 present s th e bloo dlea dlevel s b y age . I n bot h 12- 7P.1 7



### G6P D normal an ddeficient children , th e bloo dlea

d pattern o f increas e an ddecreas e b y advancin g ag e pertains . Th e only increase , but asubstantial one , i s observe dbetween childre n les s than 1 yea r o f ag e andthos e 1 t o 3 year s old . Bloo dlea dlevel s decreas e i

n al l succeedin g ag e groups . Billic k e t al, 3 8 

### analyze ddat afro

mNe w Yor k Cit y leadscreenin g program s fro m197 0 throug h1976 . Th e dat ainclud e ag e i

n months , sex , race , residenc e expresse das healt

hdistrict , screenin g information , TABL E 12-9 . MEA N BLOO D LEA D (/xg% ) B YAGE , SEX , AN D G6P D STATU S I N 155 9 URBA N BLAC KCHILDREN 3 7 Age , year s Sex Numbe r G6P D norma l G6P D deficien t < 1 1- 3 4- 8 9-1 3 14-1 8 Bot h

Male s Female s Bot h Male s Female s Bot h Male s Female s Bot h Male s Female s Bot h Male s Female s 6 1 32 2 9 28 9 133 156 40 4 17 7 22 7 39 4 18 9 20 5 242 9 4 14 8 19. 1 ±

19. 5 ± 19. 2 + 29. 1 ± 30. 5 ± 28. 8 ± 25. 0 ± 24. 6 ± 25. 1 ± 21. 3 ± 20. 4 ± 21. 7 ± 18. 7 ± 18. 5 ± 18. 8 ± 9. 5 9. 0 9. 2 14. 6 15. 1 11. 0 12. 6 13. 2 11. 1 10. 4 10. 9 9. 7 9. 7 10. 1 8. 9 9

6 3 4 0 3 0 1 0 5 5 3 8 1 7 44 2 9 1 5 2 1 1 3 8 18. 3 ±8. 2

18. 8 ±8. 2 17. 3 ±8. 4 33. 2 ±15. 5 33. 1 ±15. 5 33. 6 ±13. 5 25. 7 ±13. 4 25. 2 ±12. 9 26. 1 ±13. 5 23. 0 ±12. 5 22. 1 ±11. 8 24. 8 ±13. 9 19. 1 ±9. 9 18. 9 ±9. 3 19. 5 ±10. 1 

### an dbloo dleadvalue s expresse di n decades . Only th e firs t screenin g dat afo

r individual childre n wer

e include dbase do

n th e analysi s o

f venou s blood . Only th e dat a(178,58 8 values ) clearl y identifie das comin g fro

mth e firs t

screenin g o

f agiven chil dwer

e used . Al l bloo dlea

ddetermination s wer

e don e b y th e sam e laboratory . Th e dat apresente dar e preliminary an da

n exhaustiv e analysi s ha s no t been completed . Tabl e 12-1 0 present s th e geometri c mean s fo r th e children' s bloo dleadlevel s b y ag e an d TABL E 12-10 . GEOMETRI C MEA N BLOO D LEA D LEVEL S I N NE W YOR KCITYLEA D SCREENIN G PROGRA M (Calculate d o n th e basi s o f th e Billic k

e t al. 3 8 data ) Grou p an d yea r Black s 1970 197 1 1972 1973 197 4 197 5 1976 Hispani c 1970 197 1 1972 1973 197 4 197 5 1976 White s 1970 197 1 197 2 197 3 1974 197 5 1976 1-1 2

27. 2 25. 2 22. 3 22. 6 22. 2 20. 5 18. 1 21. 5 19. 9 18. 7 20. 1 19. 7 17. 4 17. 9 21. 0 19. 9 17. 1 20. 3 18. 6 19. 1 20. 7 13-2 4

31. 2 29. 7 26. 3 26. 9 25. 7 22. 9 20. 7 24. 9 22. 9 20. 6 21. 8 21. 4 19. 6 18. 6 23. 9 22. 8 20. 2 21. 5 20. 5 20. 0 17. 2 25-3 6

31. 2 30. 4 26. 7 26. 3 25. 5 22. 9 21. 2 25. 5 25. 0 22. 1 22. 5 23. 0 20. 6 19. 2 24. 7 22. 9 22. 0 21. 9 20. 0 19. 0 19. 1 Age . month s

37-4 8 28. 4 29. 8 25. 8 25. 6 24. 4 22. 3 20. 9 23. 9 24. 9 22. 6 23. 1 22. 6 20. 9 19. 3 25. 0 23. 0 21. 1 22. 1 21. 1 18. 2 18. 7 49-6 0

31. 4 28. 7 25. 0 24. 5 23. 7 21. 7 20. 3 24. 1 24. 4 22. 1 22. 2 22. 1 20. 6 19. 2 23. 7 23. 9 21. 2 20. 6 21. 4 19. 8 18. 4 61-7 2

22. 9 27. 7 24. 3 24. 1 22. 2 21. 8 19. 2 24. 5 23. 9 22. 0 21. 6 20. 1 20. 0 18. 2 24. 9 21. 9 21. 4 21. 6 21. 3 18. 0 17. 7 73 ^

25. 7 27. 0 23. 8 23. 1 22. 1 19. 6 19. 3 24. 0 23. 9 21. 3 21. 7 20. 3 18. 5 18. 4 22. 5 21. 7 20. 6 21. 1 19. 6 17. 3 17. 5 

### 12- 8P.1 8



### rac e fo r th e 7 years . It

shoul db e mentione dtha t th e mean s presente dwere derive db y EPA fromth e ra

w dat aprovide db

y Billic k et al. 3 8 

### Becaus e th e bloo d leadlevel s were availabl e t o th e neares t 1 0 /xg/dl , th e midpoint s of

eac hinterva l were usedt o calculat e th e geometri c means . Thes e mean s wer e calculate d fo r each2-mont

hinterval fo

r eac hag e an dethni c grou p an dwere then combine dacros s th e si x 2

- mont hinterval s using a

n unweighte dgeometri c mea n s o a s t o minimiz e an

y seasonal effects . It shoul dbe note dthat

al l racial/ethni c group s show a n increas e i

n geometri c mea

n level s fro

m< 1 t o 1 t o 2 year s o

f age . Figure 12- 3 show s th e trend s fo r 1970 . Simila

r pattern s hol dfo

r othe r years . Th e 1

i

- Illl l

/ BLAC K

/ HISPANI C "*• —. . / ^^

\ / WHIT E ^ v Illl l ^

- T

AGE , year s Figur e 12-3 . Geometri c mean s fo r bloo d lea d value s by rac e an d age , NewYor k

City , 1971 . 

### difference s in age-associate dpattern s for th e thre e racial/ethni c group s ma

y b e influence db

y th e sub

stantia l difference s i

n populatio n size s fo

r th e groups : white s were th e smalles t group , Hispanic s wer e next , an dblack s th e largest . Tabl e 12-1 1 show s th e siz e o f th e group s fo

r th e 7 years . TABL E 12-11 . NUMBE R O F CHILDREN' S INITIA L SCREEN S I N NE W YOR KCIT YPROGRAM S B YRACE/ETHNICIT YAN D

YEAR , 1970-19773 * Yea rWhit e Blac k Hispani c 197 0 197 1 197 2 197 3 197 4 197 5 197 6 1,28 2

2,79 6 1,35 0 82 3 60 1 65 6 49 1 8,83 9

23,17 4 16,73 0 9,72 2 4,13 9 4,58 5 3,75 5 8,25 1

18,74 0 10,15 3 6,87 5 2,49 8 2,62 0 2,17 8 

### age s 8 day s t o 8 year s showedincreasin g mea n bloo d leadlevel s wit

hage : 3. 3 ± 2. 6 figldl

i n th e first yea r o f life , increasin g wit

heachyea

r t o amea n o f 11. 5 ± 4. 9 figldl a t ag e 6 t o 8 . I n contras t t o studie s o

f children , mos t

studie s o f adul t population s d o no t

show any marke deffect

o f agin g o n bloo dlea

dlevels . 17



### . 4 

### 0- 4 

### ' Nordman found that male s an dfemale s over

th e ag e o f 6 5 year s had lowe r bloo dleadvalue s than th e res t o f th e adul t populatio n i

n hi s study. 1 6 

### Effects o f se x on bloo dleadlevel s appear t o b e ag e dependent . Adul t

female s ar e commonl y foun d t o hav e lower

level s than males.2,16,17,23,2 4 Amon g children , however , se

x doe s no t

appear t o b e a differentiatin g factor. 424 3 

### Teppe r an dLevin 2 

### hav e suggeste dthat

th e difference s foundi

n bloo dlead level s o f adul t me n an dwome

n ar e no t th e resul t

o f eithe r difference s i

n leadintake fromfoo do r from difference s i

n hematocri t

level s between them . Dat afor th e assessment

of rac e a s afacto r

i n bloo d leadlevel s ar e relativel y scarce . 18.25,38,44,4 5 Th e earlie r studies 184 4 

### repor t

onl y th e number

o f case s abov e aspecifie dbloo dleadlevel . On e study 1 8 

### show s higher

leadlevel s for

black s than Puert o Ricans , bu t

th e other 4 4 

### report s tha t

black s hadhigh

er level s than nonblacks . In thei r study o f military recruits , Creaso n e t al. 1 8 

### compare dwhite an dblac k subjects . Dat ai

n Tabl e 12-1 2 show higher

mea n value s fo

r al l blac k group s than fo r th e whites . TABL E 12-12 . BLOO D LEA D LEVEL S (/ug/dl) 1 8 I N MILITAR Y

RECRUITS , BYRAC E AN D PLAC E

Plac e Numbe r Urba n 5 8 Suburba n 4 Outstat e 1 5 Mea n

3 8 8 0 5 9 90t h percentil e 8 5 124 105 Numbe r

20 3 21 8 40 6 Mea n

3 1 2 7 3 9 90t h percentil e 6 9 5 4 7 1



### I t i s o f interes t t o not e that

th e age-associate dpat tern observe di

n th e Unite dState s wa s no t see n i n a Wes t German 3 9 

### study . In tha t

study , 36 3 childre n o

f Th e Billic k

e t al. 3 8 

### dat ashow higher

geometri c mean bloo dlea dvalue s fo r black s tha n fo r Hispanic s o r

fo r whites . Tabl e 12-1 3 present s thes e geometri c mean s fo

r th e thre e racial/ethni c group s fo r 7 years . Th e consistenc y o f th e associatio n i s remarkable . Numerou s dat ahav e been publishe dshowin g th e effec t o f variou s occupation s o n bloo dlea d levels. 1625404 6 

### In general , thes e dat asupport th e conclusio n that

worker s expose dt o automobil e ex haust , leadfumes , o r

dus t i n manufacturin g carry higher leadburden s than thos e wh o d o not . 12- 9P.1 9

TABL E 12-13 . GEOMETRI C MEA N BLOO D LEA D LEVEL S ( M g/dl ) I N NE W YOR K LEA D SCREENIN G PROGRAM , 1970-1976 , FO R CHILDRE N U P T O 7 2 MONTH S O F AGE , B Y

RAC E AN D YEAR " Yea r 1970 197 1 197 2 197 3 197 4 197 5 197 6 Blac k

28. 6 28. 5 25. 0 25. 0 23. 9 22. 0 20. 0 Hispani c

24. 0 23. 4 21. 3 21. 9 21. 6 19. 8 18. 7 Whil e

23. 8 22. 4 20. 4 21. 3 20. 8 19. 0 18. 6 12. 3 RELATIONSHIP S BETWEE N EXTER NA L EXPOSURE S AN D BLOO D LEA D LEVEL S I n previou s chapters , it ha s bee n show n tha t

lead : 1 . I s emitte dfro mvariou s sources , primaril y automobile s an dindustria l operations . 2 . I s distribute dacros s th e environment . 3 . I s capabl e o f

bein g absorbe dint o th e huma n body . Thi s sectio n wil l describ e th e relationship s observe d betwee n th e differen t

environmenta l exposure s an d th e resultin g absorptio n a s measure db y bloo dlea d levels . Lea dtha t

i s emitte dfro mmobil e sources , e.g . au tomobil e exhausts , an dfro mstationar y sources , e.g . industria l operations , eithe r remain s in th e ai r

o r fall s out , a s discusse din Chapte r 6 . Studie s hav e show n abuildu p o f

lea di n soi l an ddus t

a s aresul t

o f emission s fro mthes e tw o sources . Further , th e lea d i n soi l an ddus t

doe s no t

deriv e onl y fro mthes e source s but , i n addition , fro mth e deterioratio n an d erosio n o f

lea dbase dpaint . Therefore , althoug hsoi l an ddus t ar e direc t

source s o f

huma n exposur e t o lead , the y mus t

als o b e viewe din term s o f th e pri

mar y mobil e an dstationar y source s o f th e lead . Consequently , studie s tha t examin e onl y ambien t

ai r lea dexposure s may , in fact , underestimat e th e tota l contributio n o f

airborn e lea dt o th e population' s lea dburden . Effort s t o estimat e experimentall y th e relativ e im

portanc e o f

combustio n o f

leade dgasolin e t o tota l lea dburde n i n human s hav e onl y recentl y bee n initi

ated . Manto n ha s presente devidenc e fro ma preliminar y stud y usin g lea disotop e ratios. 4 7 Hi s findings sugges t

tha t automobile s supplie dbetwee n 7 ± 3 an d4 1 ± 3 percen t o f th e lea di n bloo do f Dalla s resident s durin g 197 2 t o 1973 . Garibald i e t al., 4 8 i n amajo r

stud y bein g conducte din Italy , ar e attemptin g suc hallocation s o n amuc hlarge r scale . I t i s hope dtha t

thes e dat awil l b e availabl e shortly . Becaus e multipl e source s o f lea dd o exis t

an d becaus e eac hca n contribut e t o th e tota l lea dburde n o f man , a n importan t

questio n t o b e addresse di s th e contributio n o f

eac hsourc e t o th e tota l bod y burden . I n thi s section , individua l studie s examinin g th e con tributio n fro mth e majo r environmenta l source s o f lead , tha t

is , air , soil-dust , paint , food , an dwater , will b e discussed . 12.3. 1 Ai rExposure s Studie s o f

th e relationshi p o f

ai r exposure s t o bloo dlea dlevel s ma y b e separate dint o tw o mai n categories : epidemiologica l an dclinical . Epidemiologica l studie s in tur n ma y b e groupe d int o thre e types : thos e pertainin g t o population s ex pose dt o mobil e source s o f emission , thos e o f population s expose dt o stationar y sources , an dthos e in whic honl y th e amoun t o f airborn e lea di s take n int o accoun t

wit hn o effort

mad e t o identif

y th e source . Studie s dealin g wit hmobil e source s o f lea dwil l b e discusse dfirst , followe db y apresentatio n o f station

ar y source s studies . Studie s concerne dwit hai r lea d level s regardles s o f

source s wil l the n follow , an d clinica l studie s wil l complet e th e presentation . Fro m thi s array , th e studie s tha t permi t th e calculatio n o f th e quantitativ e relationshi p betwee n lea di n ai r an d lea din bloo dwil l b e selectivel y analyze dan ddis

cussed . Clinica l studie s hav e th e advantag e o f permittin g precis e contro l ove r

th e level s o f

exposur e bu t

hav e th e disadvantage s o f

studyin g peopl e unde r some wha t artifica l condition s an do f dealing , b y necessity , wit hver y few subjects . Al l clinica l studie s t o b e presente dwer e limite dt o adults . Epidemiologica l studie s hav e th e advantag e o f studyin g peopl e in thei r natura l state , bu t

frequentl y hav e th e disadvantag e o f rathe r imprecis e estimate s o f th e exposure s encountered . Thes e studie s allo w estimate s o f

th e relationshi p t o b e mad e fo r bot h adult s an dchildren . 12.3.1. 1 MOBIL ESOURC ESTUDIE S 12.3.1.1. 1 Studie s in th e Unite dStates . A 197 3 Housto n stud y examine dth e bloo dlea dlevel s o f parkin g garag e attendants , traffi c policemen , an d adul t female s livin g nea r

freeways. 6 A contro l grou p fo r eac ho f

th e thre e expose dpopulation s wa s selecte db y matchin g fo r age , education , an drace . Unfortunately , th e matchin g wa s no t altogethe r

suc cessful ; traffi c policeme n ha dles s educatio n tha n thei r control s an dth e garag e employee s wer e younge r tha n thei r

controls . Female s wer e matche d 12-1 0P.2 0

adequately , however . Th e finding s fo r th e si x group s studie dar e presente din Tabl e 12-14 . I t shoul db e note dtha t

th e mea n bloo dlea dvalue s fo r traffi c policeme n an dparkin g garag e attendants , tw o group s regularl y expose dt o highe r concentration s o f automotiv e exhausts , wer e significantl y highe r tha n th e mean s fo r

thei r relevan t

contro l groups . Statisticall y significan t

difference s i

n mea n value s wer e no t found , however , betwee n wome n livin g nea r afreewa y an dcontro l wome n livin g at greate r distance s fro mth e freeway . TABL E 12-14 . MEA N BLOO D LEA D LEVEL S FO R STUD YAN D

CONTRO L GROUPS , HOUSTON ^ Grou p Policeme n Control s Garag e attendant s Control s Wome n livin g nea rfreewa y Control s Mean . jjg'd l 23. 1 18. 4 28. 3 21. 3 12. 9 11. 9 S D

9.2 1 7.3 8 10.3 3 9.7 0 4.4 7 4.2 8 Sampl e

siz e 14 1 15 0 11 9 9 5 12 0 11 7 P = 0.0 5

P= 0.0 5

P > 0.0 5 A Californi astudy 7

- 4 9 examine dbloo dlea dlevel s i n relatio n t o exposur e fro mautomotiv e lea di n tw o communities , Lo s Angele s an dLancaste r ( acity representativ e o f

th e hig hdesert) . Lo s Angele s resi

dent s studie dwer e individual s livin g in th e vicinit y o f heavil y travele dfreeway s withi n th e city . The y in

clude dmale s an dfemales , age d1 throug h16 , 1 7 throug h34 , an d3 5 an dover . Th e person s selecte d fro mLancaste r

represente dsimila r

ag e an dse x dis

tributions . O n tw o consecutiv e days , blood , urine , an dfece s sample s wer e collected . Ai r sample s wer e collecte dfro mon e Hi-Vo l sample r in Lo s Angeles , locate dnea r

afreeway , an dtw o suc hsampler s i n Lancaster . Th e Lo s Angele s sample r collecte dfo r

7 days ; th e 2 in Lancaste r wer e utilize dfo r

1 4 days . O n th e firs t

da y o f ai r sampling , soi l sample s wer e collecte din eac hare ain th e vicinit y o f stud y sub

jects . Lea din ambien t

ai r alon g th e Lo s Angele s free

wa y average d6. 3 ± 0.7 1 /xg/m 3 , an din th e Lan

caste r are ath e averag e wa s 0. 6 ± 0.2 1 /ig/m 3

. Th e mea n soi l lea din Lo s Angele s wa s 363 3 figlg, wherea s tha t

foun din Lancaste r

wa s 66. 9 figlg. Highe r concentration s o f

lea dwer e foun di n th e bloo do f children , a s wel l a s younge r an dolde r adult s livin g nea r

th e freeway , tha n i n individual s livin g i n th e contro l area . Tabl e 12-1 5 show s th e mea n bloo dlea dvalue s fo r th e si x groups . Difference s betwee n Lo s Angele s an dLancaste r group s wer e significan t

withth e sol e exceptio n o f th e olde r males . TABL E 12-15 . ARITHMETI C AN D GEOMETRI C MEA N BLOO D LEA D LEVEL S (Mg/dl )

FO R LO S ANGELE S AN D LANCASTER , CA , B YSE XAN D AGE 7

Group s byse x an d age . year s Tota l Male s 1-1 6 17-3 4 35 - Female s 1-1 6 17-3 4 35 - N 12 6 5 6 2 0 2 9 7 7 0 1 8 4 1 1 1 Lo s Angele s

Mea n 16. 4 19. 3 23. 5 16. 6 18. 5 14. 2 16. 7 12. 9 14. 7 SE a

0. 7 1. 1 2. 5 1. 1 2. 0 0. 7 1. 8 0. 6 1. 5 Geometri c

mea n 14. 6 17. 2 20. 8 15. 1 17. 1 12. 8 14. 9 11. 8 13. 4 N

11 9 5 0 2 1 1 8 1 1 6 9 2 5 1 6 2 8 Lancaste r

Mea n 10. 5 11. 8 11. 1 11. 8 13. 0 9. 6 10. 2 9. 1 9. 3 S E

0. 4 0. 6 0. 8 0. 9 2. 0 0. 4 0. 7 1. 2 0. 5 Geometri c

mea n 9. 6 10. 8 10. 4 10. 9 11. 1 8. 8 9. 6 8. 0 8. 7 Significanc e

o f differenc e P b «.00 1 «.00 1 «00 1 .00 3 .0 9 «00 1 •C00 1 <00 1 <00 1

a Standar d error . b I test . I t ha s bee n pointe dou t

b y Sne e that , in th e high

traffic-densit y area , th e reporte d2 9 percen t o f sam ple s i n childre n 1 throug h1 6 year s ol dexceedin g 4 0 figldl represente d5 individuals. 5 0 Fo r 3 o f thes e a secon dbloo dsampl e showe dapproximatel y 2 0 figldl; asecon dsampl e wa s no t collecte dfro mth e othe r 2 . Th e disparit y betwee n bloo dsample s take n o n consecutiv e day s fro mchildre n in th e stud y call s int o questio n th e validit y o f usin g thes e value s t o quantif y th e ai r lea dt o bloo dlea drelationship . Th e difference s betwee n sample s fo r adults , althoug h somewha t

large r tha n thos e foun din othe r studies , appea r acceptabl e fo r

us e i n calculations , however . A stud y o f

th e effect s o f

lower-leve l urba n traffi c densitie s o n bloo dlea dlevel s wa s undertake n in Dallas , Tex. , in 1976. 3 4 Th e stud y consiste do f tw o phases . On e phas e measure dair-lea dvalue s fo r selecte dtraffi c densitie s an dconditions , rangin g 12-1 1P.2 1

fro m^.1,00 0 t o abou t

37,00 0 cars/day . Th e secon d phas e consiste do f

a n epidemiologica l stud y o f traffi c densit y an dbloo dlea dlevel s amon g resi

dents . Figur e 12- 4 show s th e relationshi p betwee n arithmeti c mean s o f

ai r lea dan dtraffi c density . A s ca n b e see n fro mth e graph , areasonabl e fi t i s shown . TABL E 12-17 . SOI L LEA D LEVEL S BYTRAFFI C DENSITY "

-

- o •r- " D I

O

I o I

o

1 O ! "1

0 o o^^^ ^ O O

" " 1 1 T1 0

Y= •0.659 8 + 0.026 3 X X= cars/da y 1 1 1 1 -

-

_ ] 0 4,00 0 8.00 0 12.00 0 16.00 0 20.00 0 24.00 0 28.00 0 32.00 0 36,00 0 38.00 0 TRAFFI C VOLUME , cars/da y Figur e 12-4 . Arithmeti c mea n o f ai r lea d level s by traffi c count , Dallas , 1976.3 " I n addition , durin g thi s phase , dat afo r indoor

outdoo r comparison s o f

ai r lea dlevel s wer e col

lected . I n tw o areas , wit htraffi c densitie s o f 10,00 0 an d20,00 0 cars/day , hig hvolum e sampler s measure dai r

lea doutsid e o f

selecte dhouses . A t

th e sam e time , indoo r

ai r lea dvalue s fo r

thes e house s wer e als o collected . Tabl e 12-1 6 show s th e findings . Approximatel y atenfol ddifferenc e wa s foun dbe

twee n indoor-outdoo r

value s in bot hlocations . I t ha s bee n postulate dtha t a t leas t par t o f thi s differenc e i s th e resul t

o f usin g ai r

conditioners . TABL E 12-16 . MEA N AI R LEA D LEVEL S (fj.g/m3) INDOOR S AN D OUTDOOR S ATTW O TRAFFI C DENSITIES , DALLAS , TEX . 1976* " 10.00 0 cars'da y 20.00 0 car s da y

Outdoo r Indoo r Outdoo r Mea n N 0.18 2

9 0.91 8

9 0.19 9

5 2.10 5

5 I n addition , fo r

al l distance s measure d( 5 t o 10 0 f t fro mth e road) , ai r

lea dconcentration s decline d rapidl y wit hdistanc e fro mth e street . A t 5 0 f t con centration s wer e abou t

5 5 percen t

o f th e stree t

con centration ; a t

10 0 f t concentration s wer e les s tha n 4 0 percen t o f th e stree t

concentrations . I n ai r lea dcol

lection s fro m5 t o 10 0 f t fro mth e street , approx imatel y 5 0 percen t

o f th e airborn e lea dwa s i n th e respirabl e rang e ( < 1 fim) an dth e proportion s i n eac hsiz e clas s remaine dapproximatel y th e sam e a s th e distanc e fro mth e stree t increased . Soi l lea dconcentration s wer e highe r in area s wit h greate r traffi c densit y (Tabl e 12-17) . Th e maximu m soi l leve l obtaine dwa s 73 0 figlg. Traffi c density , vehicles/da y Soi l lea d levels . II gig <1.00 0 1,000-13,49 9 13.500-19,49 9 >19,50 0 73. 6 92. 2 110. 9 105. 9 Dustfal l sample s fo r

2 8 day s fro m9 location s showe dn o relationshi p t o traffi c densities , bu t out doo r level s wer e a t

leas t 1 0 time s th e indoo r

con centratio n in nearb y residences . I n th e secon dphase , thre e group s o f subjects , 1 t o 6 year s old , 1 8 t o 4 9 year s old , an d5 0 year s an d older , wer e selecte din eac ho f 4 stud y areas . Traffi c densitie s selecte dwere : < 1,000 , 8,00 0 t o 14,000 , 14,00 0 t o 20,000 , an d20,00 0 t o 25,00 0 cars/day . Th e stud y group s average dabou t 3 5 subjects , althoug hth e numbe r

varie dfro m2 1 t o 50 . Th e smalles t group s wer e fro mth e highes t traffi c densit y area . N o relationshi p betwee n traffi c densit y an d bloo dlea dlevel s in an y ag e group s wa s foun d (Figur e 12-5) . Bloo dlea dlevel s wer e significantl y highe r in children , 1 2 t o 1 8 figldl, tha n in adults , 9 t o 1 4 figldl.

-

-

~ 1 1 1 1



# A.

f ' \

FEMALE S < 9 * / \

\

MALE S < 9

** -VfC—' " MALE S >4 9 °~~ ^ j ^

_Q

_FEMALES19-4 9 ef " .Q

_5

FEMALE S >4 9

1 1 1 1 < 1,00 0 1,000-13.50 0 13,500 - 19,50 0 19,500 -

38.00 0 TRAFFI C DENSITY , cars/da y Figur e 12-5 . Bloo d lea d concentratio n an d traffi c densit y b y sex an d age , Dallas , 1976. 3 4 Galk e e t al. 4 3 studie dbloo dlea dlevel s i n 18 7 Sout hCarolin achildre n l t o 5 year s ol di n relatio n t o lea din soi l an dt o automobil e traffic . Th e arithmeti c mea n bloo dlea dleve l wa s relate dt o bot h factors , a s show n i

n Tabl e 12-18 . 12-1 2P.2 2

TABL E 12-18 . BLOO D LEA D CONCENTRATION S I N RELATIO N T O SOI L LEA D CONCENTRATION S AN D TRAFFI C DENSITY* * (MQ/dl )

Soi l lea d concentrations . uglg <58 5 >58 5 Tota l Lo wmea n

(951-167 7 cars/day ) 3 2 (7)a 36(10 ) 34(9 ) Automobil e traffi cdensit y

Hig h mea n (2446-963 7 cars/day ) 41(8 ) 43(11 ) 42(10 ) Al l densitie s

35(8 ) 41(11 ) 38(10 )

a Standar d deviatio n o f a singl e observation . Capri o e t

al. 5 1 compare dbloo dlea dlevel s an d proximit y t o majo r

traffi c arterie s i n astudy , re porte din 1971 , tha t

include d522 6 childre n i n Newark , Ne w Jersey . Ove r 5 7 percen t

o f th e childre n livin g withi n 10 0 f t o f roadway s ha dbloo d lea dlevel s greate r

tha n 4 0 figldl. Fo r

thos e livin g betwee n 10 0 an d20 0 f t fro mth e roadways , mor e tha n 2 7 percen t

ha dsuc hlevels ; an da t distance s greate r tha n 20 0 ft , 3 1 percen t exceede d4 0 figldl. Tabl e 12-1 9 indicate s tha t th e effec t

o f automobil e traffi c wa s see n onl y in th e grou p tha t live dwithi n 10 0 f t o f th e road . TABL E 12-19 . BLOO D LEA D LEVEL S I N CHILDRE N AGE D 1 T O 5 I N NEWARK , NJ , I N RELATIO N T O DISTANC E O F RESIDENC E FRO M A MAJO R ROADWAY , 1971 "

(M9/dl ) Distanc e o f residenc e fro m roadway , ft <10 0 100-20 0 >20 0 numbe r Percen t bloo d lea d level s <4 0 42. 6 72. 4 68. 4 340 1 40-5 9

49. 3 24. 2 26. 9 156 2 >6 0 8. 1 3. 4 4. 7 26 3 Numbe r

75 8 507 396 1 522 6 N o othe r source s o f

lea dwer e considere din thi s study . Dat afro mothe r

studie s o n mobil e source s in

dicate , however , tha t

i t i s unlikel y tha t

th e bloo d lea dlevel s observe din thi s stud y resulte dentirel y fro mautomotiv e exhaus t emissions . Daine s e t

al . studie dblac k

wome n livin g nea r

a heavil y travele dhighwa y in Ne w Jersey. 5 2 Th e sub

ject s live di n house s o n street s parallelin g th e high

way a t 3 distances , 3.7 , 38.1 , an d121. 9 m . Ai r lea d a s wel l a s level s fo r

bloo dlea dwer e measured . Mea n annua l ai r

lea dconcentration s wer e 4.60 , 2.41 , an d2.2 4 /ttg/m 3 , respectively , fo r th e 3 dis

tances . Th e mea n ai r

lea dconcentratio n fo r

th e are a closes t t o th e highwa y wa s significantl y differen t fro mtha t i n bot hth e secon dan dthird , bu t th e mea n ai r lea dconcentratio n o f

th e thir dare awa s no t

sig

nificantl y differen t

fro mtha t

o f th e second . Th e result s o f

th e bloo dlea ddetermination s parallele d thos e o f th e ai r lead . Mea n bloo dlea dlevel s o f th e 3 group s o f

women , in orde r

o f increasin g distance , wer e 23.1 , 17.4 , an d17. 6 fig/100g, respectively . Again , th e first

grou p showe dasignificantl y highe r mea n tha t

th e othe r

two , bu t

th e secon dan dthir d groups ' bloo dlea dlevel s wer e simila r t o eac hother . Daine s e t

al., 5 2 in th e sam e publication , reporte da secon dstud y in whic hth e distance s fro mth e high

way wer e 33. 5 an d45 7 meter s an dwher e th e sub

ject s wer e whit e uppe r middl e clas s women . Althoug hth e ai r

lea dlevel s wer e triviall y differen t at thes e tw o distances , th e bloo dlea dlevel s di dno t differ . Becaus e th e resident s neares t th e roa dwer e alread y 3 3 m( + 10 0 ft ) fro mit an dbecaus e othe r studie s ha dshow n a n exponentia l declin e in ai r lea d level s wit hincreasin g distanc e fro mth e road , reach

in g backgroun dai r

lea dlevel s at

25 0 ft , th e explana

tio n may li e i n th e fac t

th e ai r lea dlevels , althoug h statisticall y different , wer e insufficien t t o b e reflecte di n th e bloo dlea dlevels . I t i s no t possibl e t o substantiat e thi s possibilit y becaus e th e observe dai r lea dvalue s fo r

th e tw o distance s wer e no t reported . I n 1964 , Thoma s e t

al. 5 3 investigate dbloo dlea d level s i n 5 0 adult s wh o ha dlive dfo r a t leas t 3 year s withi n 25 0 f

t o f afreewa y (Lo s Angeles ) an dthos e o f 5 0 other s wh o ha dlive dfo r alik e perio dnea r

th e ocea n o r a t leas t 1 mil e fro mafreeway . Mea n bloo d lea dlevel s fo r

thos e nea r

th e freewa y wer e 22. 7 ± 5. 6 fo r me n an d16. 7 ± 7. 0 figldl fo r women . Thes e concentration s wer e highe r tha n fo r contro l subject s livin g nea r

th e ocean : 16. 0 ± 8. 4 figldl fo r me n an d 9. 9 ± 4. 9 figldl

fo r women . Th e highe r

values , however , wer e simila r

t o thos e o f

othe r Lo s Angele s populations . Measure dmea n ai r concentration s o f lea din Lo s Angele s fo r

Octobe r 196 4 wer e 12.2 5 ± 2.7 0 jag/m 3 a t

alocatio n 3 0 f

t fro mth e San Bernar

din o freeway ; 13.2 5 ± 1.9 0 /u.g/m3 a t anothe r loca

tio n 4 0 f t fro mth e sam e freeway ; 6.4 0 ±2.1 5 /Lig/m 3 a t afourt hfloo r

locatio n 30 0 f

t fro mth e freeway ; an d4.6 0 ± 1.9 2 /u.g/m3 1 mil e fro mth e neares t free

way . Th e investigator s conclude dtha t th e difference s observe dwer e consisten t wit hcoastal-in

lan datmospheri c an dbloo dlea dgradient s i n th e Lo s Angele s basi n an dtha t th e effec t

o f residentia l proximit y t o afreewa y (2 5 t o 25 0 ft ) wa s no t demon

strated . 12.3.1.1. 2 Britis hstudies . I n aBirmingham , Eng

land , study , mea n bloo dlea dlevel s i n 4 1 male s an d 5 8 female s livin g withi n 80 0 mo f ahighwa y in

terchang e wer e 14.4 1 an d10.9 3 figldl, respectively , jus t prio r t o th e openin g o f

th e interchang e in Ma y 1972.5 4 pro mOctobe r

197 2 t o Februar y 197 3 th e respectiv e value s fo r

th e sam e individual s wer e 18.9 5 an d14.9 3 fig/dl. I n Octobe r 197 3 the y wer e 12-1 3P.2 3

23.7 3 an d19.2 1 figldl. Th e investigator s note d difficultie s i n th e bloo dcollectio n metho ddurin g th e baselin e perio dan dchange dfro mcapillar y t o venou s bloo dcollectio n fo r th e remainin g tw o sam ples . T o interpre t

th e significanc e o f

th e chang e i n bloo dcollectio n method , som e individual s gav e bot hcapillar y an dvenou s bloo da t th e secon dcol

lection . Th e mean s fo r bot hcapillar y an dvenou s blood s wer e calculate dfo r th e 1 8 male s an d2 3 female s wh o gav e bot htype s o f blood. 5 5 Th e venou s bloo dmea n value s fo r

bot hthes e male s an dfemale s wer e lower , 0. 8 an d0. 7 figldl, respectively . I f thes e difference s i n mean s wer e applie dt o th e mean s o f th e thir dseries , th e mean s fo r male s woul db e reduce dt o 24. 8 ,ug/d l an dtha t fo r th e female s t o 18. 7 figldl. Thes e adjuste dmean s stil l sho w a n in

creas e ove r

th e mean s obtaine dfo r th e first series . O n th e othe r

hand , discardin g th e mean s calculate d fo r th e first serie s an dcomparin g onl y th e mean s fo r venou s bloods , namel y serie s tw o an dthree , agai n show s a n increas e fo r

bot hgroups . Th e increas e in bloo dlea dvalue s wa s large r tha n expecte dfollow

in g th e mode l o f

Knelso n e t

al. 5 6 becaus e ai r

lea d value s nea r

th e roa dwer e approximatel y 1 ,u.g/m 3

. Th e investigator s conclude dtha t eithe r th e lea d aeroso l o f

ver y smal l particle s behave dmor e lik e a ga s s o tha t

considerabl y mor e tha n 3 7 percen t o f in

hale dmateria l wa s absorbe do r tha t ingestio n o f lead-contaminate ddus t migh t b e responsible . Studie s o f

taxica b driver s hav e employe ddifferen t variable s t o represen t

th e drivers ' lea dexposure, 575 8 on e bein g night

- versu s day-shif t drivers; 5 1 th e other , mileag e driven. 5 8 I n neithe r cas e wa s an y differenc e observed . Th e studie s reviewe dsho w tha t automobile s pro duc e sufficien t

emission s t o increas e ai r an dnearb y soi l concentration s o f

lea da s wel l a s increas e bloo d lea dconcentration s i n childre n an dadults . Th e proble mi s o f

greate r importanc e whe n house s ar e locate dwithi n 10 0 f

t (3 0 m ) o f

th e roadway . 12.3.1. 2 STATIONAR Y SOURC ESTUDIE S 12.3.1.2. 1 Primar y smelters . Mos t studie s o f

nonin

dustry-employe dpopulation s livin g i n th e vicinit y o f industria l source s o f

lea dpollutio n wer e triggere d becaus e evidenc e o f

sever e healt himpairmen t ha d bee n found . Subsequently , extremel y hig hexposure s an dhig hbloo dlea dconcentration s wer e found . Th e followin g studie s documen t th e healt hproblem s tha t ca n develo p a s wel l a s som e o f th e relationship s be

twee n environmenta l exposur e an dhuma n response . 12.3.1.2.1. 1 El

Paso, Texas. I n 1972 , th e Cente r fo r Diseas e Control , formerl y th e Communicabl e Dis

eas e Center , studie dth e relationship s betwee n bloo d lea dlevel s an denvironmenta l factor s i n th e vicinit y o f aprimar y smelte r

emittin g lead , copper , an dzin c locate di n E l Paso , Texas , tha t ha dbee n i n operatio n sinc e th e lat e 1800's. 33

- 5 9 Estimate dlea demission s fro mthi s smelte r

wer e 29 7 metri c ton s i n 1969 , 51 9 metri c ton s i n 1970 , an d31 7 metri c ton s i n 1971, 3 3 Thes e figures , however , includ e onl y stac k emis

sions ; th e quantitie s i n fugitiv e emission s vi aventila

tion , windows , etc. , ar e unknown . Dail y high

volum e sample s collecte do n 8 6 day s betwee n Februar y an dJun e 197 2 average d6. 6 /ig/m 3 o f lead . Concentration s range dfro m0.4 9 t o 7 5 /ig/m 3

. Thes e ai r

lea dlevel s fel l of

f rapidl y wit hdistance , reaching , a s woul db e expected , backgroun dvalue s approximatel y 5 k

mfro mth e smelter . Level s wer e highe r downwind , however . Hig hconcentration s o f lea di n soi l an dhousedus t wer e found , wit hth e high

es t level s occurrin g nea r

th e smelter . Th e geometri c mean s o f 8 2 soi l an d10 6 dus t

sample s fro mth e sec to r closes t t o th e smelte r

wer e 179 1 an d402 2 figlg, respectively . Geometri c mean s o f bot hsoi l an ddus t lea dlevel s nea r

th e smelte r

wer e significantl y highe r tha n thos e in stud y sector s 2 o r 3 kmfarthe r

away . Sixty-nin e percen t

o f childre n 1 t o 4 year s ol dliv

in g nea r th e smelte r

ha dbloo dlea dlevel s > 4 0 /xg/dl , an d1 4 percen t

ha dbloo dlea dlevel s tha t exceede d6 0 figldl. Concentration s in olde r in

dividual s wer e lower ; nevertheless , 4 5 percen t o f th e childre n 5 t o 9 year s old , 3 1 percen t o f th e in

dividual s 1 0 t o 1 9 year s old , an d1 6 percen t o f th e individual s abov e 1 9 ha dbloo dlea dlevel s al l ex ceedin g 4 0 figldl. Th e dat apresente dpreclud e calculation s o f

mean s an dstandar ddeviations . Dat afo r peopl e age d1 t o 1 9 year s livin g nea r th e smelte r showe darelationshi p betwee n bloo dlea d level s an dconcentration s o f lea din soi l an ddust . Fo r individual s withbloo dlea dlevel s >4 0 figldl, th e geometri c mea n concentratio n o f lea di n soi l at thei r home s wa s 258 7 figlg, wherea s fo r thos e wit ha bloo dlea dconcentratio n <4 0 figldl, hom e soil s ha d ageometri c mea n o f

141 9 figlg. Fo r

housedust , th e respectiv e geometri c mean s wer e 644 7 an d206 7 Mg/g

Analysi s foun dth e effec t o f lengt ho f

residenc e t o b e importan t

onl y i n th e secto r

neares t th e smelter . Forty-thre e percen t

o f th e 1

- t o 19-year-old s wh o ha dlive dther e 2 o r

mor e year s ha dbloo dlea d value s 24 0 figldl, wherea s onl y 1 8 percen t o f th e 1

- t o 19-year-old s wh o ha dlive dther e les s tha n 2 year s ha dsimila r

levels . Additiona l source s o f

lea dwer e als o investigated . A relationshi p wa s foun dbetwee n bloo dlea dcon 12-1 4centration s an dlea dreleas e fro mpottery , bu t th e numbe r o f individual s involve dwa s ver y small . N o relationship s wer e foun dbetwee n bloo dlea dlevel s an dhour s spen t

ou t o f door s eac hday , schoo l atten dance , o r employmen t

o f aparen t a t th e smelter . Th e reporte dprevalenc e o f

pic aals o wa s minimal . I t wa s conclude dtha t

th e primar y facto r

associ

ate dwithelevate dbloo dlea dlevel s in th e childre n wa s ingestio n o r

inhalatio n o f

dus t containin g lead . Dat ao n dietar y intak e o f lea dwer e no t

obtaine d becaus e th e climat e an dproximit y t o th e smelte r prevente dan y farmin g i n th e area . I t wa s unlikel y tha t th e dietar y lea dintake s o f th e childre n fro m nea r th e smelte r

an dfarthe r

awa y wer e significantl y different . 12.3.1.2.1. 2 Kellogg, Idaho. I n 1970 , EP A carrie d ou t astud y o f

alea dsmelte r

in Kellogg , Idaho. 60

- 6 1 Th e stud y wa s par t

o f anationa l effort

t o determin e th e effect s o f

sulfu r dioxide , tota l suspende dparticu

late , an dsuspende dsulfates , singl y an din combina

tio n wit hothe r

pollutants , o n huma n health . I t focuse do n mixture s o f th e sulfu r

compound s an d metals . Althoug hit

wa s demonstrate dtha t childre n ha devidenc e o f

lea dabsorption , insufficien t en vironmenta l dat awer e reporte dt o allo w furthe r quantitativ e analyses . I n 1974 , followin g th e hospitalizatio n o f tw o childre n wit hsuspecte dacut e lea dpoisoning , CD C joine dth e Stat e o f Idah o in acomprehensiv e stud y o f childre n in th e area. ' 6 2 Th e studie s conducte di n thi s are aunfortunatel y use dabewilderin g arra y o f designation s in thei r

reports , bu t

al l ar e relate dt o th e sam e industria l complex . Th e sourc e o f

exposur e wa s a*smelte r whos e record s showe dtha t

emission s o f

lea dint o th e at mospher e average d8. 3 metri c ton s pe r mont hfro m 195 5 t o 1964 , 11. 7 metri c ton s fro m196 5 t o Sep

tembe r 1973 , an d35. 3 metri c ton s fro mOctobe r 197 3 t o Septembe r

1974. 6 2 I n Septembe r

1973 , afir e destroye dth e mai n filtratio n facilit y fo r th e smelter . Th e stud y wa s initiate din Septembe r 1974 , afte r

tw o childre n wer e hospitalize dwithsymptom s o f lea d poisoning . A t

tha t time , bloo dlea dlevel s 24 0 figldl wer e foun din 38 5 (41. 9 percent ) o f 91 9 childre n les s tha n 1 0 year s ol dwh o wer e examined . Abou t 9 9 per cen t o f th e 17 2 childre n livin g withi n 1. 6 k mo f th e smelte r ha dbloo dlea dvalue s 24 0 figldl. Th e mea n bloo dconcentratio n decline dwithdistanc e fro mth e poin t o f emissio n (Tabl e 12-20) . Bloo dlea dlevel s wer e consistentl y highe r i n childre n 1 t o 4 year s ol d tha n in thos e 5 t o 9 year s old . I n addition , highe r level s i n childre n wer e associate dwit hreporte dac tiv e ingestio n o f

lead-containin g materia l (pica) , withlowe r

socioeconomi c status , an dwit hparenta l employmen t

a t th e smelte r

o r a t alea dmine . A sig

nifican t negativ e relationshi p betwee n bloo dlea d TABL E 12-20 . GEOMETRI C MEA N BLOO D LEA D LEVEL S B YARE A COMPARE D WIT H ESTIMATE D AI R LEA D LEVEL S FO R 1 - T O 9-YEAR-OL D CHILDRE N LIVIN G NEA R IDAH O SMELTE R (Geometri c standar d deviations , sampl e sizes , an d distance s fro m smelte r ar e als o given) " G M bloo d lead . ug/d l 65. 9 47. 7 33. 8 32. 2 27. 5 21. 2 GS D 1.3 0 1.3 2 1.2 5 1.2 9 1.3 0 1.2 9 Sampl e siz e 17 0 19 2 17 4 15 6 18 8 9 0 Estimate d ai rlead . /xg/m J 18. 0 14. 0 6. 7 3. 1 1. 5 1. 2 Distanc e fro m smelter . k m 0 - 1. 6 •1.6 - 4. 0 4.0-10. 0 10.0-24. 0 24.0-32. 0 abou t 7 5

a EPAanalysi s o f dat a fro m Yanke l e t al. 1 leve l an dhematocri t

valu e wa s found . Seve n o f 4 1 childre n (1 7 percent ) withbloo dlea dlevel s 28 0 figldl wer e diagnose db y th e investigator s a s bein g anemi c o n th e basi s o f

hematocri t

les s tha n 3 3 per cent , wherea s onl y 1 6 o f 100 6 childre n (1. 6 percent ) withbloo dlea dlevel s < 8 0 figldl wer e s o diag

nosed . Althoug hn o over t

neurologi c diseas e wa s ob

serve di n childre n wit hhighe r lea dintake , difference s wer e foun di n nerv e conductio n velocity . Detail s o f

thi s findin g wer e discusse di n apreviou s chapter . Beginnin g in 1971 , ambien t concentration s o f

lea d in th e vicinit y o f

th e smelte r

wer e determine dfro m particulat e matte r

collecte din high-volum e ai r samplers . Dat aindicate dtha t monthl y averag e level s measure di n 197 4 (Figur e 12-6 ) wer e thre e t o fou r time s th e level s measure di n 1971. 6 3 Individua l exposure s t o lea dwer e estimate db y interpolatio n fro mthes e high-volum e data , an dastron g correla

tio n wa s foun dbetwee n th e estimate s an dth e measure dbloo dlea dlevel s ( r + 0.72) . 12-1 5P.2 5

Figur e 12-6 . Monthl y ambien t ai r lea d concentration s i n Kellogg , Idaho , 197 1 throug h 1975. 6 3 

### Subsequently , Yanke l et

al . publishe dadditiona l informatio n concernin g th e 197 4 study a s well a s th e result s o f afollow-up study conducte di n 1975. ' Th e follow-up wa s undertake n t o determin e th e effec

tivenes s o f contro l measure s initiate dafte r th e 197 4 study . Between Augus t

197 4 an dAugus t

1975 , th e mea

n annual ai r

leadlevel s decrease da t al l station s monitore d(Figur e 12-7) . In orde r o f increasin g dis

tanc e fro mth e smelter , th e concentration s i n th e tw o year s wer e 18. 0 t o 10. 3 /Ag/m 3 

### , 14. 0 t o 8. 5 /ng/m3 

### , 6. 7 t o 4. 9 jug/m3 

### , and , finally, 3. 1 t o 2.5/ig/m 3 

### a t 1 0 t o 24 km . Simila

r reduction s were note di n th e housedus t leadconcentrations . In aseparat e report , von Lindern an dYanke l describe dreduction s i

n bloo dleadlevel s o

f childre n fo r who mdetermination s wer

e mad e i n bot hyears. 6 0 

### I t wa s pointe dou t

tha t th e childre n wit

hth e highes t bloo dleadlevel s i

n 197 4 hadbeen relocated ; thei r removal an dsubsequent

relocatio n woul dcompli

cate an y analysi s i

n whichthey wer

e included . T o compensate fo

r this , th e author s als o presente dsepa ratel y th e bloo dleadlevel s for thos e childre n livin g i n th e sam e home bot

hyears . Thi s greatl y reduce d th e number

o f observation s reported . Th e result s (Tabl e 12-21 ) demonstrat e that significant

reduc

tion s i n bloo dleadconcentratio n ca n b e effected , an dtha t they were observe di

n eac hstudy area . In area s III , IV , an dV , al l mea n bloo dlea

dlevel s wer

e <4 0 figldl. Th e report

o f Yanke l et

al. 1 

### showedtha t

ther e I 1 AUG . 197 4 rrrr\ AUG . 197

5

CONTRO L 

# D_D_n 3 4 5 B YARE A (SE E TEXT ! Figur e 12-7 . Annua l ambien t ai r lea d concentration , b y area , befor e th e August 197 4 an d Augus t 1975 surveys. 1 

### wer e reduction s i

n environmenta l leadcontamina

tio n between 197 4 an d1975 , an dtha t th e correla

tion s between bloo dleadlevel s an denvironmenta l o r demographi c factor s wer e consistent

fro mon e yea r t o th e next . Fiv e factor s influenced , i n a statisticall y significant

manner , th e probability of a chil ddevelopin g a

n excessiv e bloo dleadlevel : 1 . Concentration s of

lea di n ambien t

ai r (Mg/m 3 

### ) . 2 . Concentratio n o

f leadi n soi l (ppm) . 3 . Ag e (years) . 4 . Cleanlines s o

f th e hom e (subjectiv e evaluatio n code d0 , 1 , and2 , wit h2 signifying dirtiest) . 5 . Genera l classificatio n o f th e parents ' oc cupatio n (dimensionless) . Althoug hth e stronges t

correlatio n foundwas be

twee n bloo dlea

dlevel andair

lea dlevel , th e author s conclude dthat

i t was unlikel y that

inhala

tio n o f contaminate dair

alon e coul dexplai n th e ele

vate dbloo dleadlevel s observed . Yanke l an dvon Lindern reasone dtha t even thoug hai r

leadwas th e principa l source , amajor rout e o f exposure was th e ingestio n of leadi n soi l anddust. 1 

### They propose dtha t t o protec t

th e health 12-1 6P.2 6

TABL E 12-21 . MEA N BLOO D LEA D LEVEL S I N CHILDRE N LIVIN G I N VICINIT YO F A PRIMAR YLEA D SMELTER , 1974 an d 197 5

Grou p N H N I I X Stud yare a an d dat a se t II I N •) ( N I V X N V X Bloo d level s >80,ug/d| a i n 197 4 tes t Reteste d i n 1975 Differenc e Bloo d level s >6 0 bu t <8 0 /ug/d l i n 1974 tes t Reteste d i n 1975 Differenc e Bloo d level s <60n.g/d l i n 197 4 tes t Reteste d i n 1975 Differenc e 90. 2 52. 3 -38. 0

64. 5 — 47. 4 8 -17. 2 — 52. 3 — 80. 0

61. 0 -19. 0

69. 6 50. 3 -19. 3

47. 0 45. 6 37. 4 2 3 36. 0 2 0 39. 8 -14.9 —-11. 0 —- 5. 8 1 4 43. 7 37. 4

- 6. 3 61. 0

51. 0 -10. 0 43. 4 33. 5

- 9. 9

a Adapte d fro m vo n Linder n an d Yankel. 6 3

o f th e childre n i n thi s are ath e regulatio n o f environ

menta l standard s mus t

tak e int o accoun t

al l o f thes e route s o f exposure . Thes e investigator s develope damathematica l mode l base do n th e 197 4 dat atha t include deac ho f th e fiv e factor s tha t

ha dbee n show n t o b e correlate d wit hincrease dbloo dlea dlevels . Th e model , show n below , ca n b e use dt o estimat e th e effec t o f varia

tion s i n th e environmenta l factor s o n mea n bloo d lea dlevel s i n children : 1 n (Pb-B ) =3.1 + 0.04 1 (Air ) + 2. 1 x 10 5 (Soil ) + 0.08 7 (Dust ) + 0.01 8 (Age ) + 0.02 4 (Occupation) . (Se e abov e fo r

definitio n o f

units) . (12-6 ) 12.3.1.2.1. 3 CDC-EPA study. Bake r e t al., 3 1 i n 1975 , surveye d177 4 childre n 1 t o 5 year s old , mos t o f who mlive dwithi n 4 mile s o f 1 9 lead , copper , o r zin c smelter s locate di n variou s part s o f th e Unite d States . Bloo dlea dlevel s wer e modestl y elevate d nea r tw o o f th e 1 1 coppe r

an dtw o o f

th e fiv e zin c smelters . Althoug hbloo dlea dlevel s in childre n wer e no t elevate di n th e vicinit y o f thre e lea d smelters , thei r

FE Plevel s wer e somewha t highe r tha n thos e foun din controls . Increase dlevel s o f lea d an dcadmiu mi n hai r

sample s wer e foun dnea r lea d an dzin c smelters ; thi s wa s considere devidenc e o f externa l exposure . N o environmenta l determina

tion s wer e mad e fo r

thi s study . 12.3.1.2.1. 4 Meza Valley, Yugoslavia. A Yugosla

via n stud y in th e Mez aValle y investigate dex posure s t o lea dfro mamin e an dasmelte r ove r a perio do f

years. 646 9 Th e min e an dsmelte r ar e lo

cate dnea r

arive r flowin g i n th e valley . Th e smelte r produce s abou t

23,00 0 metri c ton s annually . Afte r contro l equipmen t

wa s installe do n 1 o f

2 lead-emit

tin g stacks , emission s wer e calculate dt o b e 203. 2 metri c tons/year . I n 1967 , 24-h r lea dconcentration s measure dfro m4 differen t day s varie dfro m1 3 t o 8 4 /*g/m 3 i n th e villag e neares t th e smelter , an dcon centration s o f

u p t o 6 0 /ig/m 3 wer e foun da s far a s 5 kmfro mth e source . Mea n particl e siz e i n 196 8 wa s <0. 8 /im. Th e lea dlevel s wer e abou t 25,00 0 pp mi n th e mos t contaminate darea . Analysi s o f som e com mo n foodstuffs showe dconcentration s tha t wer e 1 0 t o 100 time s highe r

tha n correspondin g foodstuf f fro mth e leas t

expose dare a(Mezica). 6 4 After Januar y 196 9 whe n partia l contro l o f emis

sion s wa s establishe da t th e smelter , weighte d averag e weekl y exposur e wa s calculate dt o b e 2 7 figlm*i n th e villag e nea r th e smelter . I n contras t t o this , th e cit y o f

Zagreb, 6 5 whic hha s n o larg e station

12-1 7P.2 7



### ar y sourc e o

f lead , ha da n averag e weekl

y ai r lea d level o f 1. 1 figlm*. I n 1968 , th e averag e concentratio n o f ALA i n urin e sample s fro

m91 2 inhabitant s o

f six village s varie db y villag e fro

m9. 8 t o 1 3 mg/liter . A contro l grou p ha damea

n ALA o f 5. 2 mg/liter . Dat aon lead i n bloo dan dth e ag e an dse x distributio n o

f th e villager s wer

e no t given. 6 4 

### O f th e 91 2 examined , 55 9 ha da n ALA leve l > 1 0 mg/liter o f urine . In 1969 , amore extensiv e study o f 28 6 individual s wit

hALA >1 0 mg/liter

was under

taken. 6 6 

### ALA- U decrease dsignificantly fromth e previou s year . When th e publishe ddat awer e ex amine dclosely , ther e appeare dt o b e som e discre

pancie s i n interpretation . Th e exposure fro mdus t an dfro mfoodmigh

t hav e been affectedb

y th e con tro l devices , bu t

no dat awer

e collecte dt o establis h this . In on e village , Zerjau , ALA- U droppe dfro m 21. 7 t o 9. 4 mg/liter

i n childre n 2 t o 7 year s o

f age . Correspondin g ALA- U value s fo r 8

- t o 15-year-old s an dfo r adul t me n an dwome

n were reduce dfro

m 18. 7 t o 12.1 , from23. 9 t o 9.9 , an dfro m18. 5 t o 9. 0 mg/liter , respectively . Becaus e leadconcentration s i n air 6 5 

### eve

n afte r 196 9 indicate da

n averag e expo sure o f 2 5 ^g/m 3 

### , i

t i s possibl e that

som e other ex planatio n shoul db e sought . Th e autho r indicate di

n th e report tha t th e decreas e i

n ALA- U showed"th e dependenc e o n meteorologic , topographic , an dtech

nologi c factors." 6 6 

### Leadi n bloo dwas determined , but accordin g t o th e report

"determinatio n o

f leadi n bloo dcoul dno t

be usedfo

r exposure evaluatio n becaus e al l obtaine dvalue s were i n th e norma l limits " (unde r

8 0 figldl

bloo da s define db

y th e author). fi 

### f > I n ligh t o f curren t knowledge , thi s defini

tio n o f normal level s i s excessively high . Th e excretio n o

f nonchelate dleadi

n urin e i n 8. 5 percen t o f 20 9 individual s was abov e 0. 1 mg/liter . Th e highes t

valu e recorde dwa s 0.1 9 mg/liter . When treate dwit

hC aEDTA , th e mobilize dleadi n th e urin e o f thes e individual s range dfro m0. 5 t o 4. 2 mg/liter , indicatin g th e presenc e o f tota l body bur

den s rangin g fro

mnormal t o te n time s normal. 666 8 

### Anothe r findin g o

f thi s projec t

was asignificant increas e i n reticulocytes , especiall y i n children. 6 6 

### Forty-seve n percent

o f expose dadult s complaine d o f pai n i n thei r bone s compare dwit

honly 3 percen t o f th e controls . Fuga s et al. 6 9 

### i n alate r repor t estimate dth e time

weighte daverag e exposure o f several population s studie ddurin g th e cours e o f thi s project . Stationary sampler s a s well a s personal monitor s were use dt o estimate th e exposure t o airborn e leadfo r variou s part s of th e day . Thes e value s were the n couple d wit hestimate dproportion s o f tim e a t whichthes e ex posure s held . In Tabl e 12-22 , th e estimate dtime

weighte dbloo dleadvalue s a s well a s th e observe d mea n bloo dleadlevel s fo

r thes e studie dpopulation s ar e presented . An increas e i n bloo dlea dvalue s oc cur s wit hincreasin g ai r

leadexposure . TABL E 12-22 . MEA N BLOO D LEA D LEVEL S I N SELECTE D YUGOSLAVIA N POPULATIONS , B YESTIMATE D WEEKL Y TIME-WEIGHTE D AI R LEA D EXPOSURE 6 9

Populatio n Rura l I Rura l I I Rura l II I Postme n Custom s officer s Stree t ca rdriver s Traffi cpoliceme n N 4 9 4 7 4 5 4 4 75 4 3 2 7 Time weighte d ai rlea d Mg/m 3 0.07 9 0.09 4 0.14 6 1. 6 1. 8 2. 1 3. 0 Mea n bloo d

lea d level , jjg/d l 7. 9 11. 4 10. 5 18. 3 10. 4 24. 3 12. 2 S D

4. 4 4. 8 4. 0 9. 3 3. 3 10. 5 5. 1 

### 12.3.1.2.1. 5 East

Helena, Montana. EPA i n 197 2 investigate dalead-emittin g smelter comple x i

n Eas t Helena , Montana. 6 0 

### Th e quantitie s o f leademission s wer e no t known . Air

leadconcentration , measure d i n 1969 , yielde daverage s fromseveral station s tha t varie dfrom0. 4 t o 4 /xg/m3 

### ; th e maximum24-hr valu e wa s foun dt o b e 1 5 figlm*. In th e cit y o f Helena , th e averag e concentratio n was 0. 1 jig/m 3



### . Leadi n soi l wa s foundt o b e 4000 , 600 , an d100 figlg at distance s o

f 1.6 , 3.2 , an d6. 4 k

m(1 , 2 , an d4 miles) , respectively , fromth e smeltin g complex . Un

contaminate dsoi l nea

r th e Helen aValle y showe da mea n o f 1 6 figlg. Deposite dlead(dustfall ) wa s foundt o var

y fro m3 t o 10 8 mg/m 2 

### -mont hi n Eas t Helen aan dfro

m1 t o 7 mg/m^-mont

hi n Helena . Studie s on human s b

y Hamme r

e t al. 6 1 

### wer

e limite dt o children ; leadvalue s i n hai r an dbloo d wer e foundt o b e higher

i n Eas t Helen athan i

n Helena , th e respectiv e average s bein g 15. 6 ± 5. 1 an d11. 6 ± 4. 0 figldl

i n bloo dan dabou t

4 0 an d1 3 ppmi n hair . Th e hai r

value s indicate ddifferential exposure t o lead . However , i n th e opinio n o

f th e in

vestigators , althoug hth e bloo dleadvalue s indicate d a n elevate dexposure , i

t hadno t been excessive . N o advers e healtheffects hadbeen note di n thes e children . 12.3.1.2.1. 6 Other

smelter studies. Othe r

report s i n th e literatur e hav e als o shown tha t peopl e livin g nea r smelter s hav e increase dburden s o f leadi n thei r bodies. 707 2 

### I t

i s clear , therefore , tha t

emission s from primary lea dsmelter s can caus e elevate dbloo dlead level s an dothe r

indicator s o

f increase dlea dburden s i n population s livin g nea

r thes e stationary emissio n sources . 12-1 8P.2 8

Th e questio n o f

th e accurac y o f

th e reporte d analyti c result s in thes e studie s i s difficul t t o addres s becaus e the y spanne daperio do f tim e in whic hma jo r stride s wer e take n in improvin g analytica l tech

nology . Hence , th e mor e recen t studie s ar e likely , bu t no t necessarily , t o provid e mor e accurat e infor

mation . Althoug hman y o f

th e report s specifie dtha t th e bloo dlea dlevel s wer e don e in duplicate , thi s unfor

tunatel y doe s no t

ensur e thei r

accuracy . Thi s prob

le mi s discusse din mor e detai l in Chapte r 9 . 12.3.1.2. 2 Othe r

industria l sources . Exposure s fro mbot haprimar y an dsecondar y smelte r i n th e in

ner-cit y are ao f

Omaha , Neb . hav e bee n reporte db y Angl e e t al . i n aserie s o f

publications. 737 6 Studie d fro m197 0 t o 197 7 wer e childre n fro ma n urba n schoo l immediatel y adjacen t t o asmal l batter y plan t an ddownwin dfro mtw o othe r lea demissio n sources , school s i n amixe dcommercial-residentia l area , an dschool s in asuburba n setting . Children' s bloo dlea dlevel s wer e obtaine db y macr o techniqu e fo r 197 0 an d1971 , bu t

Delve s micr o assa y wa s use d fro m197 2 on . Th e differenc e fo r th e chang e i n tech

nique s wa s take n int o accoun t in th e presentatio n o f th e data . Ai r

lea dvalue s wer e obtaine db y Hi-Vo l samplers , an ddustfal l value s als o wer e collected . Tabl e 12-2 3 present s th e authors ' summar y o f al l th e data , showin g tha t

a s ai r lea dvalue s decreas e an d the n increase , dustfal l an dbloo dlea dvalue s follow . Th e author s use dregressio n models , bot hlog-linea r an dsemilog , t o calculat e ai r lead/bloo dlea dratio s an dobtaine dvalue s o f 10.0 4 an d0.4 , respectively . Th e 0. 4 valu e i s equivalen t t o arati o o f

10. 4 at a n ai r lea dleve l o f

1. 0 pig/m 3

. TABL E 12-23 . AIR , DUSTFALL , AN D BLOO D LEA D CONCENTRATION S I N OMAHA , NEB. , STUDY , 1970-1977 a ' 75 - 7 6

Grou p Al l urba n children , sit e m: 1970-7 1 1972-7 3 1974-7 5 1976-7 7 Childre n a t schoo l c . sit e c : 1970-7 1 1972-7 3 1974-7 5 1976-7 7 Al l suburba n children , sit e r : 1970-7 1 1972-7 3 1974-7 5 1976-7 7 1.4 8 0.4 3 0.1 0 0.5 2 1.6 9 0.6 3 0.1 0 0.6 0 0.7 9 0.2 9 0.1 2 M 9

±l+ ± + +l+ + +l+ + + Air , m 3 IN) b 0.14(7:65 ) 0.08(8;72 ) 0.03(10:72 ) 0.07(12:47 ) 0.11(7:67 ) 0.15(8:74 ) 0.03(10:70 ) 0.10(12:42 ) 0.06(7:65 ) 0.04(8:73 ) 0.05(10:73 ) — Dustfall . ng m 3 - m o IN) C

— 10. 6 ±0.3(6 ) 6. 0 ±0.1(4 ) 8. 8 (7)

— 25. 9 ±2.4(5 ) 14. 3 + 4.1(4 ) 33. 9 (7 )

— 4. 6 ±1.1(6) 2. 9 ±0.9(4 ) — Blood . Mg'd l (N) d 31. 4 + 0.7(168 ) 23. 3 ±0.3(211 ) 20. 4 ±0.1(284 ) 22. 8 ±0.7(38 ) 34. 6 ±1.5(21 ) 21. 9 ±0.6(54 ) 19. 2 + 0.9(17 ) 22. 8 ±0.7(38 )

— 19. 6 ±0.5(81 ) 14. 4 ±0.6(31 ) 18. 2 ±0.3(185 ) r Pb-B » Pb-A = -0.9 5 ( N = 10 ) Pb- B = 10.0 4 Pb- A+ 17.0 6 r lnPb-B » Pb-A = 0.9 1 ( N = 10 ) 1 n Pb- B = 0. 4 Pb- AI 2.8 6 Bloo d lea d 1970-7 1 i s byth e macr o technique , correcte d fo ra n establishe d laborator ybia s o f 3 ng dl , macro-micro ; al l othe rvalue s ar e b yDelve s micr o assay . N = Numbe ro f months ; numbe ro f 24-hou rsamples . N = Numbe ro f months . N = Numbe ro t bloo d samples . Specifi c report s presen t variou s aspect s o f

th e wor k done . Blac k

childre n i n th e tw o elementar y school s closes t

t o th e batter y plan t

ha dhighe r

bloo d lead s (34. 1 figldl) tha n thos e i n elementar y an d junio r hig hschool s farthe r

awa y (26. 3 /xg/dl) . Bes t estimate s o f

th e ai r exposure s wer e 1.6 5 an d1.4 8 Mg/m 3 , respectively. 7 3 Th e late r stud y compare d thre e populations : urba n versu s suburba n hig h schoo l students , age s 1 4 t o 18 ; urba n blac k children , age s 1 0 t o 12 , versu s suburba n whites , age s 1 0 t o 12 ;

blacks , age s 1 0 t o 12 , wit hbloo dlea dove r 2 0 fig percen t versu s schoolmate s wit hbloo dlea dlevel s belo w 2 0 fig percent. 7 4 Th e urba n versu s suburba n hig hschoo l childre n di dno t diffe r significantly , 22. 3 ± 1. 2 t o 20. 2 ± 7. 0 figldl, respectively , wit h mea n value s o f

ai r lea dconcentration s o f 0.4 3 an d 0.2 9 figlm 3

. Fo r

th e 1 5 student s wh o ha denviron

menta l sample s take n fro mthei r homes , correlatio n 12-1 9coefficient s betwee n bloo dlea dlevel s an dsoi l an d

housedus t

lea dlevel s wer e 0.3 1 an d0.2 9 respec tively . Suburba n 10-to-12-year-old s ha dlowe r bloo d lea dlevel s tha n thei r

urba n counterparts , 17. 1 ± 0. 7 an d21. 7 ± 0. 5 figldl, respectively. 7 4 Ai r lea d exposure s wer e highe r i n th e urba n tha n i n th e suburba n population , althoug hth e averag e exposur e remaine dles s tha n 1 /xg/m 3

. Dustfal l lea dmeasure ments , however , wer e ver y muc hhigher : 32.9 6 mg/m 2 -mont hfo r

urba n 10-to-12-year-old s versu s 3.0 2 mg/m 2 -mont hfo r

suburba n ones . Soi l lea dan dhousedus t lea dexposur e level s wer e significantl y highe r

fo r th e urba n blac k

high-lea d grou p tha n fo r

th e urba n low-lea dgroup . A signifi

can t correlatio n (r

= 0.49 ) betwee n bloo dlea dan d soi l lea dlevel s wa s found . I n aDallas , Texas , stud y o f tw o secondar y lea d smelters , th e averag e bloo dlea dlevel s o f expose d childre n wa s foun dt o b e 3 0 figldl versu s a n averag e o f 2 2 figldl i n contro l children. 7 7 Fo r th e tw o stud y populations , th e ai r

an dsoi l lea dlevel s wer e 3. 5 an d 1. 5 /xg/m 3 an d72 7 an d25 5 ppm , respectively . Direc t automobil e traffi c exposur e wa s no t con sidered . I n Toronto , Canada , th e effect s o f tw o secondar y lea dsmelter s o n th e bloo dan dhai r lea dlevel s o f nearb y resident s hav e bee n extensivel y studied. 787 9 I n apreliminar y report , Robert s e t al. 7 8 state dtha t bloo dan dhai r

lea dlevel s wer e highe r i n childre n livin g nea r

th e tw o smelter s tha n in childre n livin g in a n urba n contro l area . Biologi c an denvironmenta l lea dlevel s wer e reporte dt o decreas e wit hincreasin g distanc e fro mth e smelte r stacks . A late r an dmor e detaile drepor t identifie dahig h rat e o f lea dfallou t

aroun dth e tw o secondar y smelters. 7 9 Fallou t

i n th e vicinit y o f

th e smelter s wa s cause dprimaril y b y larg e particulat e fugitiv e emis

sion s rathe r

tha n stac k

emissions . Lea demission s fro mth e tw o smelter s wer e estimate dt o b e 15,00 0 an d30,00 0 kg/yr . Lea dconcentration s in soi l wer e a s hig ha s 40,00 0 an d16,00 0 ppm , respectively , clos e t o th e 2 smelter s an ddroppe dof f exponen tiall y wit hdistance . The y reache durba n back

groun dlevel s o f

10 0 t o 50 0 ppm , 20 0 t o 30 0 mfro m th e smelter . Horn , i n alate r report , pointe dou t

tha t th e extremel y hig hsoi l level s wer e th e resul t o f som e sample s containin g scra p batter y plate ; in hi s repor t h e state s tha t

th e soi l lea dlevels , excludin g thos e contaminate dsamples , approache d800 0 pp min nonresidentia l area s an dexceede d400 0 pp mi n severa l residentia l yards. 8 0 H e als o pointe dou t severa l othe r

deficiencie s in th e data. 8 0 A genera l criticis mh e levele da t th e study' s interpretatio n wa s tha t th e author s conclude dtha t soi l lea dwa s th e mai n sourc e o f

lead , aputativ e findin g i n Horn' s view , especiall y considerin g tha t fe w soi l sample s wer e taken . Lea dconcentration s i n dustfal l wer e muc hhighe r a t 1 o f th e 2 smelters , exceedin g 150 0 mg/cm 2

- month . Thes e concentration s als o exhibite da n expo nentia l decreas e wit hdistanc e simila r t o tha t ob

serve dfo r

soils . Becaus e th e lea dfallou t occurre d ove r asmal l are aan dconsiste dprimaril y o f larg e particle s (i n som e case s th e mas s media n diamete r wa s a s larg e a s 4. 6 ± 1. 3 fim), i t wa s believe dtha t th e emission s originate dmainl y fro mdust-produc

in g operation s a t

lo w heigh t

rathe r tha n fro mstac k emissions. 7 8 Lea dconcentration s in ai r rangin g fro m1. 0 t o 5. 3 /xg/m 3 wer e onl y twic e thos e foun dat othe r Toront o urba n site s awa y fro mth e smelte r (0. 8 t o 2. 4 /xg/m 3 ) . Th e rang e o f

dail y concentration s wa s muc hgreater . A t 6 0 mfro mth e stack , lea din 9 6 ai r sample s range dfro m0. 5 t o 72 5 /xg/m 3 , wherea s a t 22 0 m9 4 sample s varie dfro m<0. 5 t o 1 4 /ng/m 3

. Tw o group s o f childre n livin g withi n 30 0 mo f eac ho f

th e smelter s ha dgeometri c mea n bloo dlevel s o f 2 7 an d 2 8 /xg/dl , respectively ; th e geometri c mea n fo r 123 1 control s wa s 1 7 figldl. Twenty-eigh t percen t o f th e sampl e childre n teste dnea r on e smelte r

durin g th e summe r an d1 3 percen t

of th e sampl e childre n teste d nea r th e secon dsmelte r

durin g th e winte r

ha dbloo d lea dlevel s >4 0 figldl. Onl y 1 percen t o f th e con trol s ha dbloo dlea dlevel s >4 0 /xg/dl . Fo r children , bloo dlea dconcentration s increase dwithproximit y t o bot hsmelter s bu t

thi s tren ddi dno t

hol dfo r adult s generally . Lea dlevel s in hai r

sample s average d4 1 figlg i n th e smelte r

area s an d1 3 figlg in th e contro l area. 7 8 Bloo dlea dan dhai r

lea dlevel s wer e foun dt o b e re lated , thu s indicatin g afairl y constan t rat e o f ab

sorption . Th e author s conclude dtha t fo r childre n withexcessiv e lea dabsorptio n th e majo r rout e o f lea dintak e wa s ingestio n o f contaminate ddir t

an d dust. 78

- 7 9 Increase dexcretio n o f 8-aminolevulini c aci dan dcoproporphyrin s wa s observe di n mos t o f thes e cases , an dincrease ddensit y o f bon e metaphyse s wa s observe din fou r children . Bloo dlea dlevel s i n 29 3 Finnis hindividual s age d 1 5 t o 8 0 wer e significantl y correlate dwit hdistanc e o f habitatio n fro masecondar y lea dsmelter. 8 1 Th e geometri c mea n bloo dlea dconcentratio n fo r 12 1 male s wa s 18. 1 figldl; tha t fo r 17 2 female s wa s 14. 3 figldl. I n 5 9 subject s wh o spen t thei r entir e da y a t home , apositiv e correlatio n wa s foun dbetwee n 12-2 0m . Onl y on e o f thes e 5 9 individual s ha dabloo dlea d > 4 0 figldl, an dnon e exceede d5 0 /xg/dl . A weake r

correlatio n wa s obtaine dbetwee n ALA D activit y an ddistanc e fro mth e smelter , thi s bein g du e almos t

entirel y t o th e femal e subjects . Ex

aminatio n o f

ALA D activit y fo r

male s showe dit

t o b e simila r

regardles s o f

distanc e fro mth e smelter . Th e author s speculat e tha t thi s coul db e cause db y othe r lea dexposure s in th e mal e population . Tw o report s fro mth e USS Rdescrib e effect s o f lea di n a n are anea r

asmelter. 828 3 Averag e con centration s o f

lea din ai r

wer e a s hig ha s 4. 1 /xg/m 3 a t adistanc e o f

150 0 m ; pea k

exposure s a t

thi s distanc e reache d9. 7 /ng/m 3

. Neurologica l disturbance s wer e note di n 5 0 percen t

o f th e subject s fro mth e smelte r area , compare dwit h6 percen t in controls . N o dat a wer e give n o n age , sex , an dtyp e o f disturbances. 8 2 I n alate r study , childre n fro mth e are awer e foun dt o excret e mor e coproporphyri n tha n control s an dals o mor e lead. 8 3 Th e highes t lea dconcentratio n in urin e wa s reporte dt o b e 5 0 /xg/liter . Studie s o f

th e effect s o f

storag e batter y plant s hav e bee n reporte dfro mFranc e an dItaly. 848 5 Th e Frenc hstud y foun dtha t childre n fro ma n in

dustrialize dare acontainin g suc haplan t excrete d mor e AL A tha n thos e livin g in adifferen t area. 8 4 In

crease durinar y excretio n o f lea dan dcopropor phyri awa s foun din childre n livin g u p t o 30 0 f t fro mabatter y plan t

in Italy. 8 5 Neithe r

stud y gav e dat ao n plan t

emission s o r

lea di n air . Thes e studie s demonstrat e tha t stationar y source s withi n urba n area s d o contribut e t o increase s in ai r lea dlevels . The y sho w no t onl y tha t

mea n exposur e level s ar e highe r

bu t tha t th e rang e o f

exposure s en countere di n thei r

vicinitie s i s muc hlarge r fo r dail y o r longe r averagin g time s tha n i n th e vicinit y o f mobil e sources . Increase s o f 2 t o 3 /xg/m 3 in ai r

lea d concentration s hav e bee n associate dwit hhighe r bloo dlea dlevel s in expose dpopulations . Althoug hth e significantl y highe r ai r lea dcon centration s decreas e rapidl y wit hdistanc e fro mth e poin t o f emission , the y contribute , togethe r wit h mobil e emissions , t o th e generall y highe r ai r level s foun di n urba n area s an dthu s t o th e highe r bloo d lea dlevel s foun di n urba n populations . 12.3.1. 3 URBA N POPULATIO N STUDIE S Anothe r grou p o f

studie s dealin g wit hurba n population s examine dai r lea dan dbloo dlea d value s withou t

considerin g th e specifi c source s o f th e lea di n th e air. 2 ' 316

- 41 ' 1 2 Aza r e t al. 3 obtaine d24-h r ai r lea dexposure s fo r

150 male s ove r

a2

- t o 4-wee k perio dusin g persona l samplers . Stud y group s con siste do f 3 0 me n in eac ho f

5 city-occupatio n catego ries . Th e subject s include dcabdrivers , plan t employees , an doffic e workers . Fro mtw o t o eigh t bloo dsample s wer e obtaine dfro meac hsubjec t dur

in g th e ai r

monitorin g phase . Bloo dlea ddeter

mination s wer e don e in duplicate . Tabl e 12-2 4 pre sent s th e geometri c mean s fo r ai r lea dan dbloo d lea dfo r th e fiv e groups . Th e geometri c mean s wer e calculate db y EP A fro mth e ra w dat apresente din th e authors ' report. 3 TABL E 12-24 . GEOMETRI C MEA N AI R AN D BLOO D LEA D LEVEL S (/xg/10 0 g ) FO R FIV E CITY-OCCUPATIO N GROUPS 3

(Dat a calculate d b

y EPA )

Grou p Plan t employee s Starke , F L Plan t employee s Barksdale , W l Cabdriver s Philadelphia . PA Offic e worker s Lo s Angeles . C A Cabdriver s Lo s Angeles . CA Geometri c mea n ai rlead . ng/m 3 0.5 9 0.6 1 2.5 9 2.9 7 6.0 2 GS D

2.04 2.3 9 1.1 6 1.29 1.1 8 Geometri c

mea n bloo d lead . ug/10 0 g 15. 4 12. 8 22. 1 18. 4 24. 2 GS D

1.4 1 1.4 3 1.1 6 1.2 4 1.20 Sampl e

siz e 2 9 3 0 3 0 3 0 3 0 Regressio n equation s calculate db y th e author s fo r member s o f

eac ho f th e individua l stud y group s reveale dn o slope s significantl y greate r tha n zero . I n vie w o f th e rathe r

narro w rang e o f

lea dexposure s observe dwithi n th e groups , thi s resul t i s no t surpris

ing . Examinatio n o f

th e slope s fo r

eac hstud y grou p showe dthe y wer e homogeneou s an dthu s coul db e combined . Th e specifi c metho do f combinatio n ca n b e argued , however . Aza r e t al . chos e t o us e dumm y variable s t o represen t

th e differin g intercept s o f th e stud y group s becaus e th e intercept s wer e no t homo

geneous . I n effect , thi s mean s drawin g alin e wit ha poole dslop e o f

0.15 3 throug hth e averag e bloo d lea dconcentration . Th e Teppe r

an dLevin 2 study , describe di n detai l previously , include dbot hai r an dbloo dlea d measurements . Housewive s wer e recruite dfro m "location s i n th e vicinit y o f ai r monitors. " Wome n include dwer e > 1 9 an d< 8 0 year s o f age , ha dn o histor y o f

lea dpoisoning , an dha dno t eate n wil d game . Tabl e 12-2 5 present s th e geometri c mea n ai r an dbloo dlea dvalue s obtaine di n th e study , a s calculate db y EP A fro mth e ra w data . Geometri c mea n ai r lea dvalue s range dfro m0.1 7 t o 3.3 9 12-2 1P.3 1

/xg/m 3 , an dgeometri c mea n bloo dlea dvalue s range dfro m12. 5 (1.31 ) t o 20. 6 (1.33 ) /xg/dl . TABL E 12-25 . GEOMETRI C MEA N AI R AN D BLOO D LEA D VALUE S FO R 1 1 STUD YPOPULATIONS 2 (Dat a calculate d b

y EPA )

Communit y Lo s Alamos , N M Okeana.O H Houston , T

X Port Washington , N Y Ardmore , PA Lombard , I L Washington , D C Rittenhouse , PA Bridgeport , I L Greenwic h Village . N Y Pasadena , C A Geometri c mea n ai rlead . /i g 'm 3 0.1 7 0.32 0.8 5 1.1 3 1.1 5 1.1 8 1.1 9 1.6 7 1.7 6 2.0 8 3.3 9 Bloo d lead./jg'd l

G M 14. 9 15. 6 12. 5 15. 4 18. 0 13. 9 19. 2 20. 6 17. 6 16. 6 17. 5 GS D 1.2 8 1.3 9 1.3 1 1.28 1.3 8 1.2 7 1.2 6 1.3 3 1.2 7 1.2 8 1.3 1 Sampl e

siz e 18 5 156 186 19 6 14 8 146 21 9 136 146 13 9 19 4 Nordma n reporte dapopulatio n stud y fro mFin

land 1 6 i n whic hdat afro mfiv e urba n an dtw o rura l area s wer e compared . Thi s stud y wa s describe din detai l above . Ai r

lea ddat awer e collecte db y sta tionar y samplers . Al l level s wer e comparativel y low , particularl y i n th e rura l environment , wher e acon centratio n o f

0.02 5 /xg/m 3 wa s seen . Urban-subur

ba n level s range dfro m0.4 3 t o 1.3 2 /ig/m 3

. A stud y wa s undertake n b y Tsuchiy ae t al. 4 1 in Toky o usin g mal e policeme n wh o worked , bu t no t necessaril y lived , i

n th e vicinit y o f

ai r samplers . I n thi s study , fiv e zone s wer e established , base do n degre e o f urbanization , rangin g fro mcentra l cit y t o suburban . Ai r

monitor s wer e establishe da t variou s polic e station s withi n eac hzone . Ai r samplin g wa s conducte dfro mSeptembe r 197 1 t o Septembe r

1972 ; bloo dan durin e sample s wer e obtaine dfro m228 3 policeme n i n Augus t

an dSeptembe r

1971 . Finding s ar e presente din Tabl e 12-26 . A consisten t cor relatio n betwee n ai r

an dbloo dlea dmean s fo r th e five zone s i s shown . TABL E 12-26 . MEA N AI R AN D BLOO D LEA D VALUE S FO R

FIV E ZONE S I N TOKY O STUDY 4 1

Ai rlead , jig'm ^ Bloo d lead . ng 100 g 0.02 4 0.19 8 0.44 4 0.83 1 1.15 7 17. 0 17. 1 16. 8 18. 0 19. 7 Goldsmith 4 2 obtaine ddat afo r elementar y schoo l (9

- an d10-year-olds ) an dhig hschoo l student s in 1 0 Californi acommunities . Lowes t ai r lea dexposure s wer e 0.2 8 /xg/m 3 an dhighes t wer e 3. 4 /xg/m 3

. Fo r boy s in elementar y school , bloo dlea dlevel s range d fro m14. 3 t o 23. 3 /xg/dl ; thos e fo r girl s range dfro m 13. 8 t o 20 4 figldl

fo r th e sam e rang e o f

ai r lea dex posures . Th e hig hschoo l studen t populatio n wa s mad e u p o f

onl y male s fro msom e o f th e 1 0 towns . Th e ai r lea drang e wa s 0.7 7 t o 2.7 5 /xg/m 3 an dth e bloo dlea drang e wa s fro m9. 0 t o 12. 1 /xg/dl . Fo r th e hig hschoo l student s th e tow n wit hth e highes t ai r lea dvalu e di dno t

hav e th e highes t

bloo dlea dlevel . A furthe r commen t

o n methodolog y pertain s t o th e fac t tha t aconsiderabl e la g tim e occurre dbetwee n th e collectio n an danalysi s o f th e bloo dsamples . 12.3.1. 4 CLINICA LAN D EXPERIMENTA L STUDIE S I N RELATIO N T O AI R LEAD/BLOO D LEA D RATIO S Griffi n an dhi s colleague s undertoo k tw o studie s usin g volunteer s expose din aga s chambe r t o a n ar tificiall y generate daeroso l o f submicron-size dparti

cle s o f lea ddioxide. 8 6 Al l volunteer s wer e intro

duce dint o th e chambe r 2 week s prio r

t o th e initia

tio n o f th e exposure ; th e lea dexposure s wer e schedule dt o las t

1 6 weeks , althoug hth e volunteer s coul ddro p ou t

wheneve r

the y wished . Twenty-fou r volunteers , includin g 6 controls , participate di n th e 10. 9 /xg/m 3 exposur e study . Twenty-on e subjects , in

cludin g 6 controls , participate din th e 3. 2 /xg/m 3 ex posur e study . No t

al l volunteer s complete dth e ex posur e regimen . Bloo dlea dlevel s wer e foun dt o stabiliz e afte r

approximatel y 1 2 weeks . Amon g I I me n expose dt o 10. 9 /xg/m 3 fo r at leas t 6 0 days , a stabilize dmea n leve l o f 34. 5 ± 5. 1 /xg/d l bloo dwa s obtained , a s compare dwithan initia l leve l o f 19. 4 ± 3. 3 /xg/dl . A

U bu t 2 o f th e 1 4 me n expose dat 3. 2 /xg/m 3 fo r

at leas t 6 0 day s showe dincrease s an da stabilize dleve l o f

25. 6 ± 3. 9 figldl

wa s found , com pare dwithan initia l leve l o f 20. 5 ± 4. 4 /xg/dl . Thi s represente dan increas e o f abou t 4 0 percen t

abov e th e bas e level . Fro mth e dat aTabl e 12-2 7 wa s constructed , whic hshow s th e tim e neede dt o reac hspecifi c bloo d lea dlevel s a t

th e tw o ai r

lea dconcentrations . A s ca n readil y b e see n eve n a t th e lowe r

exposure , i

t take s onl y 7 week s fo r

th e populatio n mea n bloo dleve l t o increas e b y 5 /xg/dl . I n th e article , th e author s describe dbot hth e chemistr y an dparticl e siz e o f th e lea daerosol s generated . I n general , th e aerosol s use din thi s ex perimen t wer e somewha t

les s comple x chemically , a s wel l a s somewha t

smaller , tha n thos e foun din th e ambien t environment . Griffi n e t al., 8 6 however , poin t ou t tha t goo dagreemen t

wa s achieve do n th e basi s o f th e compariso n o f

thei r observe dbloo dlea d 12-2 2TABL E 12-27 . LENGT H O F TIM E NEEDE D FO R MEA N BLOO D LEA D VALUE S T O REAC H SPECIFIE D LEVEL S A TTW O EXPOSUR E LEVEL S Exposur e grou p 1 1 1 2 2 2 Ai rlea d level , jjg' m 10. 9 10. 9 10. 9 3. 2 3. 2 3. 2 Avg . baselin e bloo d lea d level , (tig-'d l Targe t bloo d lea d level , jjg/d l 25 3 0 35 2 5 3 0 35 Tim e neede d t o reac h targe t level , w k 1 t o 2 4 6 7 No t reache d No t reache d 20. 0 20. 0 20. 0 20. 8 20. 8 20. 8 level s withthos e predicte db y Goldsmit han dHex

ter' s equation, 8 7 tha t

is , log 1 0 bloo dlea d= 1.26 5 + 0.243 3 lo g 1 0 atmospheri c exposure . I n contras t

t o th e stud y o f

Griffi n e t

al . tha t approximate s th e exposur e regime n o f environ

mentall y expose dpersons , Keho e studie dlong-ter m exposure s unde r

condition s approximatin g thos e o f occupationall y expose dindividuals. 8 8 Keho e ex pose dasubjec t

t o an ai r lea da s th e sesquioxid e firs t at 7 5 /xg/m 3 the n at

15 0 /xg/m 3

. Definit e increase s in urinar y an dbloo dlea dlevel s emerge dunde r eac h exposure . Ther e appeare dt o b e aplatea u reache din th e bloo dlea dlevel s upo n astead y stat e exposure . Gros s compile ddat afro mlea dbalanc e studie s conducte db y Keho e betwee n 193 4 an d197 2 an d determine dtha t

increase s o f

level s in blood , urine , an dfece s unde r

controlle dclinica l exposur e wer e 0.3 8 /xg/dl , 0.8 8 /xg/day , an d2.5 0 /xg/day , respec tively , fo r

eac hincreas e o f

1 /xg/m 3 i

n ai r lea d levels. 8 9 Th e derivatio n o f

thes e estimate s i s currentl y un know n bu t

wa s base do n th e result s o f ingestio n an d inhalatio n studie s carrie dou t o n 1 6 individual s ove r 21,00 0 person-days . Durin g thi s period , ther e wer e 10 2 stud y period s fo r

th e 1 6 subjects . Non e o f th e subject s experience dharmfu l effect s a s aresul t o f th e lea dexposures , th e highes t o f whic hwer e ap proximatel y 3 0 /xg/m 3 o n a24-h r basi s (ever y othe r da y t o 6 day s pe r

week ) fo r

stud y period s u p t o 62 8 days . Wit hasingl e exception , i n non e o f th e subject s di dth e bloo dleve l excee d4 0 /xg/dl . ' Rabinowit z an dcolleague s hav e conducte d studie s o f

lea dmetabolis mb y stabl e isotope s tha t permi t th e determinatio n o f

blood/ai r

lea drelation

ships. 909 1 I n on e study , asingl e voluntee r wa s con fine din ahospital' s metaboli c researc hwar dfo r a perio do f

10 9 day s fo r

2 3 h r aday. 9 0 H e wa s the n remove dint o a"clean " roo min whic hth e ai r wa s filtere dt o remov e th e particulat e lead . Fo r th e firs t 1 5 day s in th e room , hi s dail y lea dintak e wa s supplemente db y lea daddition s t o th e die t t o com pensat e fo r th e los s o f

ai r lea dintake . A t

th e en do f thi s 15-da y perio dth e dietar y lea dsupplemen t wa s discontinued . H e immediatel y showe dadeclining

bloo dlea dleve l tha t eventuall y reache da minimum . H e the n lef t th e "clean " roo man dhi s bloo dlea dleve l wen t

bac k up . Unfortunately , hi s bloo dlea ddi dno t

stabiliz e afte r

hi s exi t fro mth e "clean " room . A furthe r

repor t present s data , involvin g addi

tiona l volunteers , fro mwhic habloo dt o ai r lea d rati o ca n b e derived. 9 1 Subsequen t t o astabilizin g perio din ametaboli c ward , the y entere dth e filtere d ai r roo man dbloo dlea dlevel s decreased . Th e bloo d lea dlevel s di dstabiliz e upo n exi t fro mth e clea n room . Chamberlai n e t

al. 92

- 9 3 reporte do n studie s in whic hgasolin e containin g tetraethy l lea dlabele d with 203 P b wa s burne di n an interna l combustio n engin e an dth e resultin g tagge dlea dexhaus t aeroso l wa s inhale db y 6 volunteers . Th e lea dcon centration 9 2 wa s typicall y abou t 6 mg/m 3 an dth e tota l particulat e 3 0 mg/m 3

. Th e aggregate s o f parti

cle s abou t

0. 6 fim i

n diamete r

wer e stable : thos e . 5 0.0 1 fim tende dt o coagulate . Exposure s wer e for 3 0 mi n o r less , an dth e progres s o f th e lea dthroug hth e bod y wa s monitored . It

wa s foun dtha t

abou t 4 0 per cen t o f th e particle s wa s retained , an dtha t 6 0 per cen t wa s exhaled . Th e lun g clearanc e rat e for 203 P b activit y varie dmarkedly , dependin g o n whethe r th e aeroso l wa s irradiated . Th e transferenc e o f activit y t o th e bloo dpeake dat 5 0 h r afte r inhalatio n at

4 8 percen t o f th e initia l lun g burden . At 7 2 hr . abou t hal f o f th e lea dha dbee n remove dt o bon e an dothe r tissue s an dth e othe r

hal f ha dbecom e attache dt o re dcells . Th e amoun t o f 203 P b in th e bloo dwa s foun dt o declin e withabiologica l hal f lif e o f 1 6 days . Chamberlai n e t

al . the n extrapolate dthes e high

level , short-ter mexposure s t o longe r ter mones . Th e followin g formul aan ddat awer e use dt o calculat e a blood-to-ai r

leve l ratio : 12-2 3P.3 3

[T |/2 ] [%Deposition ] [%Absorption ] [Dail y

ventilation ] [Bloo dvolume ] [0.693 ] where : a = bloo dt o ai r lea drati o biologica l hal f

lif e (12-7 )

1 1/ 2 Dat ause dwere : 1 . Airborn e leve l = 1 /xg/m 3 2 . Exposur e = 2 4 hr/da y 3 . Dail y ventilatio n = 15m 3 /da y 4 . % Depositio n =40 * 5 . % Absorptio n = 50 * 6 . Bloo dvolum e = 540 0 ml 'Thes e value s wer e determine d experimentall y in this study ; al l other s are authors ' assumptions . Usin g th e abov e equatio n an dvalues , Cham

berlai n e t

al. 9 3 obtaine darati o o f 1.2 , i n contras t

t o avalu e o f

1. 1 reporte di n a n earlie r report, 9 2 wher e slightl y differen t

assumption s wer e made . I n thi s earlie r report, 9 2 dat afro mKehoe 8 8 an dWilliam s e t al. 9 4 wer e use di n asimila r manne r t o calculat e ratio s o f 1. 1 an d1.1, respectively . I t i s interestin g t o not e th e differenc e i n th e ratio s calculate db y Gross 8 9 an dChamberlai n e t al. 9 2 fro mth e Keho e data . However , th e extrapolatio n o f Chamberlai n e t al . o f th e short-ter mt o long-ter mexposur e i s i n clos e agreemen t

wit hth e result s o f

Keho e an do f William s e t

al. , a s Chamberlai n e t al . calculate d them . Chamberlain' s ratio s hav e bee n recalculate db y Bridbord 9 5 o n th e basi s o f amor e activ e person' s dail y ventilatio n o f

2 0 m 3

. This , h e states , woul d yiel darati o o f

1. 6 /xg/d l fo r

eac h1 /xg/m 3 o f

ai r lea d exposure . 12.3.1. 5 BLOOD/AI RLEA D RELATIONSHIP S Summarizatio n o f

th e relationshi p betwee n lea di n ai r an dlea di n bloo drequire s th e consideratio n o f severa l distinc t

line s o f evidence . Thes e include : th e minima l ai r

lea dconcentratio n a t

whic hbloo dlea d level s ar e first

elevated , th e for man dmagnitud e o f th e relationship , th e proportio n o f th e populatio n whos e bloo dlea dleve l exceed s an y specifi c valu e a t an y give n ai r

lea dconcentration , an dwhethe r th e for mo r magnitud e o f

th e relationshi p varie s de

pendin g o n whethe r

th e ai r lea dexposur e i s increas

ing , remainin g constant , o r decreasing . O n th e first

point , onl y afew studie s hav e suffi

cientl y precis e estimate s o f ai r lea dexposure s t o per mi t thi s calculation , namel y Yanke l e t al. 1 an dAza r e t al. 3 EP A use dWilliam' s 9 6 tes t o n th e dat afro m bot hthes e studie s t o determin e th e ai r lea dlevel s a t whic hbloo dlea dlevel s wer e foun dt o b e signifi

cantl y highe r

tha n th e geometri c mea n bloo dlea d level s o f th e group s expose dt o th e lowes t ai r lea d level , whic hthu s serve da s controls . William' s tes t i s amultipl e compariso n tes t designe dt o mak e suc h comparisons . Fo r dat afro mth e Yanke l e t al . study, 1 EP A poole dth e lowes t

tw o ai r lea dexposur e area s ( V an dVI ) t o for mth e contro l group . Th e tes t showe dtha t

are aI V wa s th e first , in th e ordere ddata , tha t

showe dsignifican t

elevatio n o f bloo dlea dvalues . Th e correspondin g ai r lea dcon centratio n fo r

thi s are awa s 1. 7 /xg/m 3

. EPA , usin g thi s sam e tes t fo r th e Aza r

e t al . study, 3 showe dtha t

bloo dlea dvalue s fo r

th e Phila

delphi acabdriver s wer e significantl y differen t fro m tha t fo r th e poole dStark e an dBarksdal e plan t employee s tha t

constitute dth e contro l population . Bloo dlea dvalue s fo r th e Lo s Angele s offic e worker s wer e als o significantl y highe r tha n thos e o f contro l populations . Th e correspondin g ai r lea dex posure s wer e 2. 6 an d3. 1 /xg/m 3

. respectively . Th e clinica l stud y o f

Griffi n e t

al. 8 6 provide s dat a tha t suppor t th e result s o f

th e EP A analysi s o f

Aza r e t al. 3 data . Th e dat asho w tha t individual s expose d t o 3. 2 /xg/m 3 ha dadefinit e increas e i n thei r bloo d lead s a s aresul t

o f thi s exposure . Thus , th e availabl e dat aar e consisten t a s t o th e valu e o f ai r lea dconcentratio n a t

whic hbloo dlea d level s begi n t o increase . Th e Yanke l e t al . data 1 demonstrate dthi s increas e a t 1. 7 ,u.g/m 3 ; th e Aza r

e t al . data, 3 a t

2. 6 /xg/m 3

. Thes e result s ar e no t incon

sisten t becaus e th e Aza r

e t al . stud y di dno t

hav e a populatio n expose dt o aleve l o f ai r lea dbetwee n 1 an d2. 6 /xg/m 3

. Th e derivatio n o f

th e functiona l relationshi p be

twee n ai r

lea dexposur e an dbloo dlea dlevel s ha s technica l difficultie s becaus e th e tru e for mo f thi s relationshi p i s no t

linear . N o matte r

wha t th e difficult y i n makin g thi s assessmen t is , th e for mo f th e relationshi p i s extremel y importan t becaus e i t

i s use dt o determin e th e effec t o f achang e in th e bloo d lea dlevel s a s afunctio n o f th e ai r lea dvalues . Som e studies , b y th e ver y natur e o f thei r design , onl y permi t

calculatin g th e rati o betwee n achang e i n bloo dlea dan dassociate dchang e i n th e ai r lea dcon centration . Fo r

thes e situations , th e calculate drati o ca n b e considere da s a n estimat e o f th e averag e rati o ove r th e rang e o f

th e ai r lea dlevel s encountered . Fo r thos e studie s in whic hafunctiona l relation

shi p ca n b e derived , thi s rati o ca n b e estimate dfo r a give n ai r

lea dconcentratio n b y evaluatin g th e derivativ e o f

th e functiona l relationshi p a t tha t 12-2 4

### value . Thi s rati o i s subjec t t o considerabl e chang e over th e rang e o

f ai r leadlevel s encountered , de

pendin g on th e for

mo f th e relationshi p that

wa s fitted . W e hav e chosen , wherever

possible , t o us e th e author' s ow

n mode l fo

r th e relationship. Th e earlies t

attemp t t o us e epidemiological dat a t o calculat e ablood-to-ai r leadrelationshi p was mad e b y Goldsmithan dHexter. 8 7 

### A linea r regres sion equatio n of

th e logarith mo

f th e bloo dlead level on th e ai r

lea dlevel was performe do n dat a fro mth e Three-City Study. 4 0 

### Dat afro mKehoe' s ob

servation s on 4 individual s experimentall y expose d t o 1 0 an d15 0 /xg/m3 

### i

n apattern equivalen t

t o anor ma l wor k exposure wer

e foundt o fi

t th e equation . Th e slop e o

f thi s lin e was no t

significant

belo w 2 figlm 3 

### o f ai r exposure , possibly becaus e fe w observa

tion s wer e availabl e i

n th e Three-City Study belo w that level . Th e derive dslop e o f th e regressio n lin e suggest s a n increas e o

f 1. 3 /xg/d l fo r eachmicrogram o f ai r lead . Aza r e t al. 3 

### usedalog-lo g mode l t o fi t thei r data ; th e data , a s well a s th e regressio n line , ar e presente d i n Figure 12-8 . Th e slopes , that is , th e ratios , wer

e calculate dfromth e equation , lo g Pb- B = 1.255 7 + 0.15 3 (lo g Pb-A) , a

t th e fou r air leadvalue s shown i n Tabl e 12-28 . Thes e slope s range dfro m2. 6 at a n ai r leado f 1.0 /xg/m3 

### t o 0. 7 a

t a n ai r leado f 5. 0 /xg/m3



### . I t i s importan t

t o not e tha t

al l fou r ai r lead concentration s of

interes t ar e well withi n th e rang e o f th e ai r level s observed .

4 0

2 0

1 0 - 1

• ' _—^— 7~ * * . •* • l 1

L-^-r~ • *. . 9 •

1 1

• ' " ' »

1 1 1 1

. °

. O LO S ANGELE S OFFIC E WORKER S ALO S ANGEt-E S CA B DRIVER S • BARKSDALE . WISCONSI N 7STARKE , FLORID A • PHILADELPHI ACA B DRIVER S 1 1 1 TOTA L AI R LEAD , ng/ m Figur e 12-8 . Bloo d lea d versu s ai r lea d fo r urba n mal e workers. 3

TABL E 12-28 . ESTIMATE D BLOO D LEA D T O AI R LEA D RATIO S FO R FOU R AI R LEA D CONCENTRATION S

Stud y Epidemiologica l Azar a Tepper-Levin b Nordman b Nordman " Fugas b Johnson b Johnson ^ Tsuchiya b Goldsmith b Goldsmith b Yankel-vo n Lindern a Chamberlains-William s Daines b Clinica l Griffin " Griffin " Rabinowitz " Gross 0 Chamberlain 0 Chamberlainc-Keho e Populatio n Adul t male s Adul t female s Adul t male s Adul t female s Adult s Adul t male s Adul t female s Adul t male s Childre n male s Childre n female s Childre n Adult s Blac k female s Adul t male s Adul t male s Adul t male s Adult s Adult s Adult s Sampl e siz e 14 9 190 8 53 6 47 8 33 0 6 4 10 7 59 1 20 2 20 3 87 9 48 2 (unknown ) 1 1 @10. 9 14 ® 3. 2 2 (21,00 0 person-days )

7 5 1. 0

2.5 7 0.8 7

1.1 6 Rati o a t

ai rlea d concentrations , 2. 0 1.4 3 0.9 2

1.2 1 u. g/m ' 3. 5

0.8 9 1.0 0 (0.42) ° (0.11 ) (2.64 ) (0.80 ) (0.60 ) (3.84 ) (2.30 ) (1.70 ) 1.2 7 (1.10 ) (2.30 ) (1.40 ) (1.65 ) (1.7,2.5 ) (0.38 ) (1.20 ) (1.10 ) 5. 0

0.6 6 1.0 8

1.3 7

a Authors ' regressio n equatio n evaluate d a t specifi cai rlead . b EPAcalculation . cAuthors ' calculations . d Ratio s presente d i n parenthese s ar e no t calculate d fro m an yregressio n equation . 

### 12-2 5P.3 5

On e o f th e authors , Snee, 5 0 ha s sinc e reanalyze d th e dat ausin g amor e complicate dmode l fo r th e relationship . Hi s newe r mode l attribute s les s o f th e increas e in bloo dlea dt o ai r lea dexposure s an d mor e t o geographi c are adifferences . Th e improve

men t in fit b y us e o f

thi s newe r

mode l i s insignificant . Furthermore , i n th e ne w model , th e are adifference s ar e correlate dwithth e ai r lea ddifferences . Fo r thes e reasons , th e origina l mode l i s believe dt o b e mor e appropriat e fo r

estimatin g th e tota l effec t o f ai r lead . Yanke l e t

al. 1 use dalog-linea r

mode l (Equatio n 12-6 ) t o fit

thei r data . Th e slope s o f

th e fou r ai r lea d value s show n in Tabl e 12-2 8 wer e calculate dfro m thi s equation . Thes e range dfro m1. 2 a t a n ai r lea d leve l o f 1. 0 /xg/m 3 t o 1. 4 at

a n ai r lea do f 5. 0 yxg/m 3

. Again , al l ai r

lea dconcentration s wer e withi n th e rang e o f th e data . On e assumptio n inheren t in th e calculatio n o f

th e regressio n o f

bloo dlea do n ai r

lea dusin g standar d leas t square s i s tha t

th e ai r lea dvalue s hav e bee n measure dwithn o error . Unfortunately , thi s assump tio n i s no t

correct . Obviously , th e monitore dai r lea d value s ar e no t

th e exac t

value s inhale db y th e sub

ject s in th e exposur e area . Th e effec t o f measuremen t erro r in th e independen t

variabl e i s discusse db y Kendal l an dStuart. 9 7 I n general , th e calculatio n regressio n coefficient s ar e underestimate s o f th e tru e values . If eithe r th e erro r

in th e dependen t

variable , o r th e erro r

in th e independen t

variable , o r

th e rati o o f th e tw o error s wer e known , the n improve desti

mate s coul db e calculated . Th e Yanke l e t

al . study 1 give s sufficien t informa

tio n t o estimat e th e effec t o f thi s problem . Th e author s assigne d1 o f

3 3 differen t

estimate dex posur e level s t o eac hindividua l in th e study . If th e withi n leve l variance s o f bloo dlea dvalue s ar e poole dfo r

thes e 3 3 levels , th e resul t i s apoole d GS D o f 1.28 . Usin g th e valu e o f 1.2 8 for th e erro r

in th e dependen t

variable , th e regressio n coefficien t o f 0.04 1 reporte db y Yanke l an dvo n Linder n become s 0.052 . Thi s adjustmen t increase s th e estimate d bloo dlea dt o ai r

lea drati o fro m1.2 1 t o 1.44 a t 2 figlm 3 an dfro m1.3 7 t o 1.6 9 at 5 Mg/m3

- Thi s proble mmay exis t in som e o f

th e othe r studies , bu t

it i s no t aseriou s proble min tw o o f th e othe r mor e importan t

studies . I n th e Aza r

study, 3 persona l sampler s wer e used , s o tha t individua l ex posure s wer e measure dmor e accuratel y tha n in an y othe r epidemiologi c study . I n th e Griffi n stud y th e ai r lea dlevel s wer e controlle dextremel y closely , s o tha t ther e wa s almos t

n o variatio n i n th e exposur e value . Th e reanalysi s o f th e Tepper-Levi n study 2 a s re porte db y Hasselbla dan dNelson 2 2 wa s use dt o esti

mat e th e relationshi p o f ai r lea dt o bloo dlea dlevels . A log-linea r

mode l wa s use dtha t

allowe dfo r

ag e an dsmokin g differences , a s wel l a s th e ai r lea dex posure . Thi s formo f

th e mode l wa s chose n becaus e i t gav e abette r

fit t o th e dat atha n di dth e log-lo g model . Th e slope s wer e calculate dfro mth e log

linea r mode l a t

th e fou r ai r lea dvalue s show n in Ta

bl e 12-28 . Thes e slope s range dfro m0. 9 a t a n ai r lea do f 1. 0 figlm 3 t o 1. 1 a t

a n ai r lea do f 5. 0 /xg/m 3

. Th e ai r lea dvalue s onl y range dfro m0. 2 t o 3. 4 /u.g/m 3 , however , Daine s e t

al . reporte dtw o studie s examinin g variation s in bloo dlea dratio s withdistanc e fro m bus y highways. 5 2 Th e studie s wer e conducte di n Camden , Ne w Jersey , an dinvolve dblac k females . Onl y on e o f

thes e studie s ca n b e use dt o determin e th e bloo dlead/ai r

lea drati o becaus e n o ai r lea ddat a wer e reporte dfo r

th e othe r

study . I n thi s study , bloo dlea dievel s o f

blac k female s livin g in resi

dence s tha t

wer e 3.7,38.1 , an d121.9 mdistan t fro m th e highwa y wer e determined . Yearl y mea n ai r an d bloo dlea dlevel s fo r

thes e thre e group s ar e pre sente di n Tabl e 12-29 . Fro mthes e value s arati o ma y b e calculate da s follows : 23.1-17. 6 rati o = A ,,, ~ ~A = 2. 3 fo r th e tota l population . 4.60-2.2 4 Usin g asimila r

calculation , housewive s wer e foun d t o hav e arati o o f

3 . TABL E 12-29 . YEARLYMEA N AI R AN D BLOO D LEA D LEVEL S O F BLAC KFEMALE S I N RELATIO N T O DISTANC E O F RESIDENC E FRO M A BUS YHIGHWA Y Stud y are a Are a A Area B Area C I n Yugoslavia , Fuga s e t al . i n th e stud y describe d earlier, 6 9 estimate dth e weekl y time-weighte dai r lea dexposure s o f

eigh t populatio n groups . Th e esti

mate s wer e base do n ai r lea dvalue s monitore dat variou s location s an destimate dproportion s o f tim e th e individual s spen t

at thos e locations . Th e time

weighte dexposur e estimates , sampl e sizes , an d bloo dlea dlevel s fo r

thi s stud y wer e presente d earlie r (Tabl e 12-22) . A weighte dregressio n analysi s wa s chose n fo r thes e dat abecaus e th e sam pl e size s o f

th e custom s officer s an dpoliceme n varie dfro mthos e fo r

th e othe r

groups . Th e rang e o f ai r lead s wa s fro m0.07 9 t o 3. 0 ,ug/m 3

. Th e resultin g slop e i s 2.64 , an di s presente di n Tabl e 12-28 . Distanc e fro m highway , m 3. 7 38. 1 121. 9 Ai rlead .

Mg/m ' 4.6 0 2.4 1 2.2 4 Bloo d lea d

jjg/l00 g 23. 1 17. 4 17. 6

12-2 6P.3 6

Snee 5 0 ha s criticize dth e inclusio n o f th e streetca r driver s becaus e o f

difference s in socia l statu s an d habit s fro mth e othe r

groups . Th e effec t

o f removin g thes e subject s woul db e t o reduc e th e calculate d slope . Thi s grou p wa s no t remove dbecaus e th e ai r lea dexposur e wa s mor e precisel y estimate dtha n in othe r studies . Dat ao n Toky o policeme n reporte db y Tsuchiy ae t al. 4 1 an ddiscusse din detai l previousl y in thi s chapte r ma y als o b e use dt o calculat e aslope . Unfor

tunately , th e slop e tha t

i s derive dca n onl y b e looke d upo n a s confirmator y evidenc e an dno t a s additiona l evidenc e becaus e o f

th e tim e differenc e betwee n samplin g th e ai r

an dsamplin g th e blood . Anothe r possibl e complicatin g facto r i s th e rural-urba n gra dien t tha t parallel s th e ai r

lea dconcentrations . Weighte dregressio n analysi s wa s use do n th e bloo d an dai r lea ddat areporte din Tabl e 12-26 . Th e esti

mate dslop e i s 3. 8 an di s recorde din Tabl e 12-28 . Th e observe drang e in ai r lea dconcentration s wa s 0.02 4 t o 1.15 7 Mg/m 3

. Fro mth e Johnso n e t

al . stud y in California, 6 esti

mate s o f th e rati o betwee n bloo dan dai r lea dlevel s ca n b e derived . Becaus e o f analysi s problem s en countere din th e bloo dlea ddetermination s o f children , it

wa s decide dtha t

avali destimat e coul d no t b e derived . Therefore , onl y dat afo r adult s wil l b e treate dhere . I t

wa s decide dt o poo l th e dat afo r adult s an dpresen t

separat e ratio s fo r

male s an d female s age d1 7 an dabove . Geometri c mea n bloo d lea dlevel s wer e use din th e calculatio n becaus e th e bloo dlea ddat awer e foun dt o follo w alog-norma l distribution . Fo r males , th e poole dgeometri c mean s wer e 15. 5 an d11. 0 figldl

fo r Lo s Angele s an dLancaster , respectively . Fo r

females , th e correspondin g value s ar e 12. 1 an d8. 4 figldl. Th e rati o wa s calculate da s follow s fo r

males : rati o = (15.5-11.0)/(6.3-0.6 ) = 0.8 . Th e rati o fo r

female s wa s 0.6 . Thes e value s ar e tabulate din Tabl e 12-28 . Nordma n in hi s doctora l dissertation 1 6 reporte d o n bloo dan dai r

lea dlevel s fo r

severa l population s i n Finlan d(Tabl e 12-30) . Becaus e o f th e larg e varia

tio n i n th e sampl e size s fo r thes e populations , EP A calculate daweighte dregressio n equation . Th e slop e o f th e equatio n wa s estimate dfo r bot hmale s an d female s separatel y an di s 0. 4 an d0.1 , respectively , a s presente din Tabl e 12-28 . I t shoul db e note dtha t th e rang e o f

ai r lea dconcentration s covere db y thi s stud y wa s 0.02 5 an d1.3 2 Mg/m 3

. Dat afro mGoldsmith 4 2 o n elementar y an dhig h schoo l childre n in anumbe r o f Californi atown s ca n als o b e use di n th e calculatio n o f th e slopes . EP A ha s TABL E 12-30 . BLOO D AN D AI R LEA D LEVEL S B YSEXI N FINNIS H POPULATIO N STUDY TM

Grou p Pertumma a Pyhajaru i Suburba n Downtow n Policeme n Stree t sweeper s Ai rlead , Mg/m 3 0.02 5 0.02 5 0.74 0.9 0 1.3 2 1.3 2 Mal e bloo d lead ,

N 24 3 — 37 14 2 2 8 8 6 ixg/d l Av g 12. 1 — 10. 6 11. 4 13. 5 13. 3 S D 4. 5 — 2. 8 3. 3 2. 8 4. 1 Femal e bloo d lead ,

N 25 6 9 3 8 1 3 7 — 1 1 /jg/d i Av g 9. 6 8. 6 9. 7 8. 5 — 10. 4 S D 3. 5 2. 5 2. 6 2. 0 — 3. 0 separatel y analyze dth e ra w dat afro mthi s stud y fo r elementar y schoo l male s an dfemales . Th e result s o f thes e analyse s sho w ratio s o f 2.3 0 an d1.70 , respec tivel y (Tabl e 12-28) . Chamberlai n e t

al. 9 2 analyze dth e dat ao f William s e t

al. 9 6 o n occupationall y expose dperson s usin g persona l monitors . Chamberlai n adjuste dth e occupationa l exposure s t o 24-h r exposure s b y calculatin g th e elevatio n in bloo dlea dfro manon expose dpopulation . H e calculate daslop e o f 1.1 . Clinica l studie s als o provid e dat ausefu l in quan titatin g th e relationshi p betwee n bloo dan dai r lead . Griffi n e t

al., 8 6 i n thei r

clinica l stud y o f

th e larges t numbe r o f subject s t o date , expose dindividual s t o 2 level s o f ai r lea dconcentrations , 10. 9 an d3. 2 Mg/m 3

. Th e stud y design , it wa s believed , preclude s fittin g a n overal l equatio n t o thes e data , an dasepa rat e calculatio n o f

arati o i s presente dfo r

th e tw o ex periments . I n bot hexperiments , th e backgroun dai r lea dlevel s wer e estimate dt o b e 0.1 5 Mg/m 3

- 1 ° tn e 3. 2 Mg/m 3 ai r

lea dexposure , th e me n increase dthei r mea n bloo dlea dlevel s fro m20. 5 t o 25. 6 figldl. Thi s yield s arati o o f

1.6 5 (25.6-20.5)/(3.2-0.15) . Th e 10. 9 Mg/m 3 ai r

lea dexposur e resulte din a n in

creas e o f bloo dlea dlevel s fro m19. 4 t o 34. 5 figldl. Thi s give s arati o o f

1.4 0 (34.5-19.4)/ ( 10.9-0.15) . Thes e value s ar e show n in Tabl e 12-28 . Chamberlai n e t

al. 9 2 reanalyze dth e Keho e result s b y adjustin g th e 37.5-h r exposure s pe r

wee k t o a24

- h r equivalent . The y use ddat afro m5 subject s whos e 24-h r equivalen t

exposure s range dfro m0. 6 t o 73. 5 Mg/m 3

. Th e calculate dratio s range dfro m0. 6 t o 2.0 , wit ha n overal l mea n o f 1. 1 fo r th e data . I n contras t

t o th e analysi s o f

Kehoe' s wor k

b y Chamberlai n i n whic ha1. 1 rati o wa s calculated , Gross 8 9 report s arati o o f 0.3 8 fo r thes e data . A t

thi s time , n o detail s ar e availabl e concernin g hi s methods . Therefore , th e apparen t discrepanc y be

twee n thes e tw o analyse s canno t b e evaluated . Chamberlai n e t

al., 92 * 9 3 a s discusse dearlier , calculate dratio s o f

1. 1 an d1. 2 base do n th e ex 12-2 7P.3 7



### trapolatio n o

f ashort-termexposure t o along-ter m one . Th e calculatio n involve s anumber o f experi

mentall y determine da s well a s assume dnumbers . A s describe dpreviously , Rabinowitz e t al. 9 1 

### studie dthre e individual s fo r metaboli c change s i

n bloo dleada s afunctio n o f change s i n th e ai r lead concentration . In contras t t o th e othe r

clinical studie s describe dwherei n ai r leadlevel s were in

creased , i n thi s study th e subject s wer e place di

n a "clean room " i

n whichth e ai r

was filtered . Thi s study , therefore , pertain s t o th e situatio n i n which th e ai r leadconcentratio n ha s decreased . Th e bloo d leadlevel s were determine dfro mth e stabilize d mea n bot hwhe n th e subjec t

was breathin g normal a s well a s filtere dair . On e o f th e me n di dno t hav e a stabilize dbloo dleadafte r returnin g t o breathin g normal air ; therefore , he coul dno t b e usedi n deter

minin g th e ratio . Th e relevan t dat afo r calculatin g th e rati o ar e include di

n Tabl e 12-31 . TABL E 12-31 . BLOO D AN D AI R LEA D DATA

FRO M CLINICA L STUDY 9 1

Subjec t D E Estimate d

Norma l air , J J g/m 3 0.9 1 0.9 1 ai r lea d

Filtere d air , li g/m 3 0.07 2 0.07 2 Bloo d lea d

Norma l air , /»g/l00 g 20. 2 16. 3 Filtere d air ,

Mg/10 0 g 18. 8 14. 2 

### Th e calculatio n fo

r subjec t D was don e a s follows : rati o = (20.2-18.8)/(0.91-0.072 ) = 1.7 . Th e calculatio n fo

r subjec t E result s i

n arati o o

f 2.5 . Only on e dat ase

t (Aza r e t al. 3 

### ) i s availabl e o

n whicht o estimat e adose-respons e relationship , that is , th e proportio n o

f apopulatio n exceedin g a specifiedbloo dleadlevel for an y specifi c exposure . Th e reason s fo

r th e paucit

y o f dat aar e twofold : (1 ) acces s i s neede dt o th e ra

w dat aand(2 ) th e exposure dat ashoul db e relativel y precise . Th e regressio n equatio n fo r th e Aza r study 3 

### ha s alread y been discussed . Th e mea n squar e erro r (MSE ) abou t

thi s equatio n was calculate dfo r al l fiv e area s combined . Fro mth e MSE , estimate s o f th e percentag e o

f th e populatio n exceedin g agiven bloo dleadlevel fo

r agiven ai r

leadlevel ar e given by : Percen t= Plog, 0 (bloo d lead ) - 1.2257-0.153 1 log | 0 (ai rlead) 1 100 

## f 

## r l ( 

# HMSE" 2 

# ] } where : N(x ) i s th e cumulativ e normal integral o f a standar dnormal variabl e up t o th e poin t x . Thes e percentage s ar e given i

n Tabl e 12-3 2 fo

r arang e o

f ai r leadvalues . Thes e tabulate dpercentage s ma y no t b e represen tativ e o f th e general population , sinc e they ar e base d on asingl e study o

f 149 subjects . They ar e presente d becaus e they ar e th e bes t estimate s availabl e o

f a dose-respons e relationship. TABL E 12-32 . ESTIMATE D PERCENTAG E O F POPULATIO N EXCEEDIN G A SPECIFI C BLOO D LEA D LEVE L I N RELATIO N

T O AMBIEN TAI R LEA D EXPOSURE *

Percen t exceedin g bloo d lea d leve l ol : r lead , ig/m 3 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5 4. 0 4. 5 5. 0 6. 0 7. 0 8. 0 20. 0 ug/d l 15.2 2 26.2 0 34.1 2 40.2 3 45.1 5 49.2 3 52.6 9 55.6 7 58.2 7 60.5 7 64.4 5 67.6 3 70.2 8 30. 0 f<g/d i 0.5 9 1.6 7 2.8 8 4.1 2 5.3 5 6.5 7 7.75 8.9 0 10.0 1 11.0 9 13.1 6 15.1 0 16.9 2 40. 0 Mg/d l 0.0 2 0.0 7 0.1 6 0.2 6 0.3 8 0.5 1 0.6 6 0.8 1 0.9 7 1.1 4 1.4 8 1.8 3 2.2 0

a Dat a derive d Iro m th e equatio n o l Aza r et al. 3 

### Th e las t element i n definin g th e relationshi p be

tween leadi

n bloo dan dleadi

n ai r i s adiscussio n o

f th e effec t that varyin g th e concentratio n o f leadi n ai r ha s on th e bloo dlea

dlevels . Mos t

o f th e dat a previousl y presente dhav e deal t wit hsteady stat e o r increasin g ai r

leadconcentrations . Thi s sectio n will summariz e th e result s of

studie s showing th e effect of decreasin g th e concentratio n o f leadi n ai r on th e bloo dleadlevel s o

f huma n populations . Rabinowit z et

al.' s study 9 I

### provide s estimate d ratio s fo r tw o subject s under

carefull y controlle d condition s who experience dadecreas e i n thei r ai r leadconcentrations . Fo r

th e tw o subjects , a1 Mg/m 3 

### decreas e i n ai r leadlevel s resulte di

n a2 figllOO g decreas e i n bloo dlea

dlevels . Baker 9 8 

### presente ddat at o th e EPA Scienc e Ad

visor y Boardshowing decrease s i n bloo dleadlevel s i n th e vicinit

y o f a n Idah o smelter

between 197 4 an d 197 5 (fabl e 12-33) . Informatio n fro mal l study area s combine dindicate dthat bloo dleadlevel s had decrease db

y 2. 3 figldl

fo r each1 Mg/m

3 

### reductio n i n ai r lead . Thi s sam

e investigato r

provide daddi

tional informatio n i

n aseparat e communicatio n t o EPA showing that , whe

n analyse s wer

e limite dt o childre n o

f nonsmelter

workers , bloo dleadlevel s decrease d2. 0 figldl

i n al l study area s fo

r eac h decreas e o

f 1 figlm 3 

### o

f ai r lead . I f th e analyse s in

clude donl y thos e childre n of nonsmelter

worker s expose dt o ai r

leadlevel s rangin g fro

m0. 5 t o 1 0 12-2 8Mg/m 3 , bloo dlea dlevel s decrease d1. 3 figldl fo r eac huni t

decreas e in ai r

lea dan dals o showe da highe r rati o a t greate r ai r lea dconcentrations . Fro m thes e analyses , i t

seem s apparen t

tha t asingl e rati o canno t describ e th e dat afro mthi s study . TABL E 12-33 . COMPARISO N O F BLOO D LEA D LEVEL S I N CHILDRE N WIT H AI R LEA D LEVEL S FO R 1974 AN D 1975

(EP A analyses )

Stud y are a 1 2 3 4 Bloo d lea d levels ,

1974 6 9 4 9 3 6 3 3 II

g/d l 1975 4 6 3 8 3 2 2 7 Diff . 2 3 1 1 4 5 A i

1974 1 8 1 4 6. 7 3. 1 lea d levels ,

Ii g/m 3 197 5 10. 3 8. 6 4. 9 2. 5 Diff . 7. 7 5. 4 1. 8 0. 6 Pb- B diff. /

Pb- Adiff . 3. 0 2. 0 2. 2 8. 0 Dat afro mAngl e an dMclntire' s studies 737 6 i n Omah aals o provid e dat ai n thi s regard . The y foun d bloo dlea dlevel s o f

urba n children , age d6 t o 18 , t o consistentl y decreas e durin g th e year s 197 0 t o 1973 . Thi s decreas e wa s almos t 1 0 figldl

acros s al l stud y groups . Furthermore , thi s decreas e ha s bee n foun d t o b e closel y correlate dwithadecreas e in ai r lea d fro mabou t

1. 5 t o les s tha n 0. 5 Mg/m 3

. I n areanalysi s o f th e ful l dat abase , Angl e ha s calculate da n overal l equatio n o f

Pb- B = 10.0 4 (Pb-A ) + 17.06 , r = 0.95 . Dat afro mNe w Yor k

Cit y analyze db y HUD 3 8 an ddescribe di n detai l i n th e demographi c variabilit y sectio n o f

thi s chapte r

ma y als o provid e supportiv e dat afo r

th e notio n tha t

adecreas e i n bloo dlea dleve l i s associate dwithdecrease dai r lea d exposure . I n th e Ne w Yor k lea dscreenin g progra m geometri c mea n bloo dlea dvalue s hav e bee n note d a s decreasin g consistentl y fro m197 0 t o 1976 . Dur

in g thi s time , som e change s occurre di n th e numbe r o f childre n sampled , s o tha t th e mor e recen t

year s hav e fa r fewe r dat apoint s tha n th e earlie r years . N o significan t

brea k in th e tren dwa s observe da s th e chang e i n sampl e siz e wa s noted . Dat afro mon e Hi

Vo l ai r statio n provide dcontinuou s ai r lea dvalue s ove r thi s perio di n Ne w Yor k City . Th e ai r

lea d value s measure dthere , no t reall y representativ e o f th e exposur e o f

th e childre n bein g studied , hav e bee n followin g asimila r pattern . I t

i s als o interestin g t o not e tha t

lea din gasolin e i n Ne w Yor k Cit y wa s als o bein g reduce ddurin g thi s period . Th e quantitativ e estimate s provide dfro mth e thre e studie s discusse dsho w decreasin g ai r lea dcon centration s var y fro maminimu mo f 1. 3 t o 8 o r

1 0 figldl. Thes e dat asugges t tha t agreate r

rati o ma y hol dfo r

decrease s in ai r

lea dtha n fo r

stead y stat e o r increasin g exposures . I n summary , in al l quantitativ e studie s presented , apositiv e relationshi p betwee n bloo dlea dan dai r lea dha s bee n found . Th e for man dmagnitud e o f th e relationship , however , ha s no t bee n foun dt o b e con stan t bu t varie s in th e studie s reviewed . Tabl e 12-2 8 summarize s th e quantitativ e estimate s derive dfro m th e revie w an danalysi s o f th e literature . I n general , th e dat asho w tha t th e bloo dlea dt o ai r lea drati o i s no t

constan t ove r th e rang e o f

ai r ex posur e encountere d(i t varie s in mos t

studie s be

twee n 1 an d2) , tha t

male s appea r

t o hav e highe r ratio s tha n females , an dtha t childre n hav e aslightl y highe r rati o tha n adults . Also , th e dat asugges t tha t mor e attentio n shoul db e give n t o studie s o f decreas

in g ai r lea dconcentration s in tha t th e ratio s derive d fro msuc hstudie s appea r highe r tha n thos e o f

stead y stat e o r increasin g exposures . 12.3. 2 Soi l an d Dus tExposure s Th e relationshi p o f

exposur e t o lea dcontaine di n soi l an dhousedus t

an dth e quantit y o f lea di n humans , particularl y i n children , ha s bee n th e sub

jec t o f scientifi c investigatio n fo r som e time. 7 8 "- 1 0 5 Dugga n an dWilliams 10 5 hav e recentl y publishe da n assessmen t

o f th e ris k o f increase dbloo dlea dresult

in g fro mth e ingestio n o f lea din dust . Som e o f

thes e studie s hav e bee n concerne dwithth e effect s o f suc h exposures: 789910 2 other s hav e concentrate do n th e mean s b y whic hth e lea din soi l an ddus t become s availabl e t o th e body. I0310 4 I n on e o f

th e earlies t

investigations , Faire y an d Gra y conducte daretrospectiv e stud y o f lea d poisonin g case s in Charleston , Sout hCarolina. 9 9 Two-inc hcor e soi l sample s wer e collecte dfro m17 0 randoml y selecte dsite s in th e cit y an dwer e com pare dwit hsoi l sample s take n fro mth e yard s o f home s wher e 3 7 case s o f lea dpoisonin g ha doccur red . Th e soi l lea dvalue s obtaine dha dawid e range , fro m1 t o 12,00 0 ppm , wit h7 5 percen t o f th e sam ple s containin g les s tha n 50 0 ppm . A significan t relationshi p betwee n soi l lea dlevel s an dlea d poisonin g case s wa s established ; 50 0 pp mwa s use d a s th e cutpoin t

i n th e chi-squar e contingenc y analysis . Thi s stud y wa s th e firs t t o examin e thi s comple x proble mand , althoug hdat asuppor t th e soi l lea dhypothesis , the y wer e no t suc ha s t o allo w fo r quantificatio n o f

th e relationshi p betwee n soi l lea dan dbloo dlea dlevels . Furthermore , becaus e n o othe r sourc e o f

lea dwa s measured , th e associatio n foun dmigh t

hav e bee n cause db y confoundin g addi

tiona l source s o f

lead , suc ha s pain t

o r air . 12-2 9P.3 9



### A late r study b y Galk e e t al. , als o i

n Charleston , usedahouse-to-hous e survey t o recrui t 194 blac k preschoo l children. 4 3 

### Soil lead , pain t lead , an dai r lea dexposure s a s measure db y traffi c densit

y wer e establishe dfo

r eac hchild . When th e populatio n was divide dint o 2 group s base don th e median soi l lead valu e (58 5 figlg), a5-Mg/d l differenc e i

n bloo dlead level s wa s obtained . Soil lea dexposure fo

r thi s populatio n range dfro

m9 t o 789 0 figlg. A multipl e regressio n analysi s o

f th e dat ashowedthat

vehicl e traffi c pattern , whe

n define db

y are ao f recruitmen t (i.e. , higho r

low) ; leadlevel i

n exterio r sidin g paint ; andleadi

n soi l wer e al l independentl y an dsignifi

cantl y relate dt o bloo dleadlevels . Barltro p e

t al. 10 0 

### describe dtw o studie s i n Englan d investigatin g th e soi l leadt o bloo dleadrelationship . In th e firs t

study , childre n aged2 an d3 an dthei r mother s fro

mtw o town s chosen fo

r thei r soi l lea d conten t eachhadthei r

bloo dleadlevel determine d fro macapillary sample . Hai r sample s wer

e als o col

lecte dan danalyze dfo

r lead . Leadconten t

o f th e suspende dparticulat e matte r andsoi l was measured . Soil sample s fo

r eachhome wer

e acomposite o

f several 2-in . cor e sample s take n fro mth e yar do

f eachhome . Chemical analysi s o f th e leadconten t

o f soil i n th e tw o town s showedatwo - t o threefol d difference , wit

hth e value s i

n th e contro l town being abou t 20 0 t o 30 0 pp

mcompare dwit

habou t 70 0 t o 1000 pp mi n th e expose dtown . A differenc e was als o note di n th e mea n ai r leadconten t

o f th e tw o towns , 0.6 9 Mg/m

3 

### compare dwit

h0.2 9 Mg/m

3



### . respectively . Althoug hthi s differenc e existed , bot hai r lea d value s wer

e though t low enoug hno t

t o affec t th e bloo dlevel value s differentially . Mea n surfac e soi l leadconcentration s fo

r th e tw o communitie s wer e statisticall y different , th e mean s fo r th e hig han dlow communit y bein g 90 9 and39 8 ppm , respectively . Despite thi s difference , n o statisticall y significant difference s in mothers ' bloo dlea dlevel s o r children' s bloo do r

hai r level s o f lea dwer e noted . Ther e was , however , suggestiv e evidenc e o f a differenc e i

n hai r leadlevel s fo

r children . Furthe r statistical analysi s o

f th e data , using correlationa l analysi s o n eithe r

ra w o r log-transforme dbloo dlead data , likewis e faile dt o show astatistical relationshi p o f soi l leadwit

heither bloo dleado r

hai r lead . Th e secon dstudy was reporte di n bot hpre liminar y an dfinal form. 10010 1 

### In th e more detaile d report, 10 1 

### children' s home s were classifie db y thei r soi l leadconten t

into thre e groups , namely < 1,000 , 1000 t o 10,000 , an d> 10,00 0 ppm . A s shown i n Ta

bl e 12-34 , children' s mea n bloo dleadlevel s in

crease dcorrespondingl y fro m20. 7 t o 29. 0 figldl. Mea n soi l leadlevel s fo

r th e low an dhighsoi l ex posure group s wer

e 42 0 an d13,96 9 ppm , respec tively . Mothers ' bloo dlevels , however , di dno t reflec t thi s trend ; no r

were th e children' s feca

l lead level s different

acros s th e soil exposure areas . TABL E 12-34 . MEA N BLOO D AN D SOI L LEA D CONCENTRATION S I N ENGLIS H STUDY 10 1 Categor y o f soi l lead , pp m <100 0 1000-1000 0 >1000 0 Sampl e siz e 2 9 4 3 1 0 Children' s

bloo d lead , n g/d l 20. 7 23. 8 29. 0 Soi l lea d

PP m 42 0 339 0 1396 9 

### Othe r studie s hav e investigate dth e relationshi p o f dus t leadt o absorption. 337810210 6 

### Som e o f thes e als o include dmeasurement s o f soi l lead . Lepo w e t al., 10 6 

### fo r example , studie dth e leadcon ten t o f air , housedust , an ddirt , a s well a s th e lea d conten t o f dir t on hands , food , an dwater , t o deter

mine th e caus e o

f chronicall y elevate dbloo dlead level s i n te n 2

- t o 6-year-ol dchildre n i n Hartford , Connecticut . Leadbase dpaint s hadbeen eliminate d a s asignificant

sourc e o

f lea dfo r thes e children . Ambient ai r leadconcentration s varie dfro m1. 7 t o 7. 0 Mg/m

3



### . Th e mea

n lea dconcentratio n i

n dir t was 1,20 0 figlg an di

n dust , 11,00 0 figlg. Th e mea n con centratio n o

f leadi n dir t on children' s hand s was 2,40 0 ppm . Th e mea

n weigh t o f sample s o

f dir t fro m hand s wa s 1 1 mg , whichrepresente donl y asmal l fractio n o f th e tota l dir t

on hands . Observatio n o f th e mouthin g behavio r

i n thes e youn g childre n lead t o th e conclusio n that

th e hands-in-mouthexposure rout e wa s th e principal caus e o f excessiv e lead accumulatio n i

n thes e children . Angl e e t al., 7 4 

### studyin g childre n i n Omaha , Nebraska , foundseveral interestin g association s be

tween soi l o r

housedus t

leadconcentration s an d bloo dleadlevels . In thi s report , thre e group s o f childre n wer

e compared : (1 ) suburban versu s urban hig hschool , (2 ) suburban versu s urban 10

- t o 12

- year-olds , an d(3 ) blac k

elementary schoo l childre n wit hbloo dlead< 2 0 versu s > 20 . Air leadlevels , al l o f whichwere les s than 1 Mg/m 3 

### , were no t

shown t o b e relate dt o bloo dleadlevels . Soil an dhousedus t wer e associated , althoug hno t alway s statisticall y significantly . Creaso n e t al., 10 2 

### studyin g hai r

metal level s i

n th e Ne w Yor k metropolitan area , usedbot hdustfal l an d housedus t

a s thei r

exposur e variables . Thre e geographi c area s i

n metropolita n Ne

w Yor k wer e chosen t o represen t

a n exposure gradient . Limite d dustfal l an dhousedus t

sample s wer

e take n t o verif

y 12-3 0th e gradien t an dt o estimat e it s magnitude . Hai r sample s wer e collecte dfro mresident s i n location s enrolle din othe r

ai r pollutio n studies . Mea n tota l environmenta l an dhai r lea dlevel s wer e the n com pared . Hai r

lea dlevel s range dfro m1 2 figlg in th e lo w are at o 1 7 figlg in th e high . Mea n dustfal l an d housedus t

lea dlevel s range dfro m2 t o 1 6 mg/m 2

- month , an dfro m27 9 t o 76 6 figlg. respectively . Hai r lea dlevel s in bot hchildre n an dadult s wer e foun dt o b e significantl y relate dt o bot hdustfal l an d housedus t

lead . N o attemp t

wa s mad e t o determin e th e origina l sourc e o f

thes e dusts . Further , th e stud y desig n di dno t

permi t th e establishmen t

o f whic ho f th e tw o dus t

type s o r bot hwer e th e actua l contribu

tor s t o th e hai r

lea dlevels . Th e investigator s con clude dtha t

th e primar y caus e o f

elevate dbloo dlea d level s in childre n wa s ingestio n o r inhalatio n o f

dus t containin g lead . Tw o othe r

studies , whic hwer e describe din mor e detai l in Sectio n 12.3 , ca n b e use dt o examin e th e relationshi p o f

lea din soi l an ddus t withlea di

n blood. 1

- 3 4 Yanke l e t

al . showe dtha t

lea din bot hsoi l an ddus t wa s independentl y relate dt o bloo dlea d levels . I n thei r

opinion , 100 0 pp msoi l lea dexposur e wa s caus e for

concern . Reanalysi s o f th e Dalla s traffi c stud y showe dasignifican t slop e o f bloo dlea d level s i n relatio n t o soi l lea dlevel s (/3 = 0.0662). 3 4 Lastly , Shellshear' s cas e repor t fro mNe w Zealan d ascribe s amedicall y diagnose dcas e o f lea dpoison

in g t o hig hsoi l lea dconten t i n th e child' s hom e environment. 10 7 Tw o studie s hav e investigate dth e mechanis mby whic hlea dfro msoi l an ddus t get s int o th e body. 10310 4 Sayr e e t

al . in Rochester , Ne w York , demonstrate dth e feasibilit y o f housedus t

bein g a sourc e o f lea dfo r children. 10 3 Tw o group s o f houses , on e inner-cit y an dth e othe r suburban , wer e chose n fo r th e study . Lead-fre e sanitar y pape r towel s wer e use dt o collec t

dus t sample s fro mhous e surface s an d th e hand s o f

children. 10 8 Th e median s fo r th e han d an dhousehol dsample s wer e use da s th e cutpoint s in th e chi-squar e contingenc y analysis . A statisticall y significan t

differenc e betwee n th e urba n an dsubur

ba n home s fo r

dus t level s wa s noted , a s wa s a relationshi p betwee n househol ddus t level s an dhan d dus t levels. 10 6 Te r Haa r an dAronow 10 4 investigate dlea d absorptio n in childre n tha t ca n b e attribute dt o in

gestio n o f

dus t an ddirt . The y reasone dtha t becaus e th e proportio n o f

th e naturall y occurrin g isotop e 210 P b varie s fo r

pain t chips , airborn e particulates , fallou t dust , housedust , yar ddirt , an dstree t dirt , it woul db e possibl e t o identif y th e source s o f

ingeste d lead . The y collecte d24-h r excret afro m8 hos

pitalize dchildre n fo r

th e firs t da y o f hospitalization . Thes e children , 1 t o 3 year s old , wer e suspecte do f havin g elevate dbod y burden s o f lead , an don e cri

terio n fo r

th e suspicio n wa s ahistor y o f pica . Te n childre n o f

th e sam e ag e level , wh o live din goo d housin g in Detroi t

an dth e suburbs , wer e selecte da s control s an d24-h r

excret awer e collecte dfo r them . Th e excret awer e drie dan dstabl e lea da s wel l a s 210 P b conten t

wa s determined . Fo r seve n hospi

talize dchildren , th e stabl e lea dmea n valu e wa s 22.4 3 figlg dr y excreta , an dth e eight hchil dha da valu e o f 164 0 figlg. Th e controls ' mea n fo r stabl e lea dwa s 4. 1 figlg dr y excreta . However , th e respec tiv e mean s fo r

210 P b expresse da s pCi/ g dr y matte r wer e 0.04 4 an d0.040 . Th e author s conclude dtha t becaus e ther e i s n o significan t differenc e betwee n thes e mean s fo r 210 Pb , th e hypothesi s tha t youn g childre n withpic aea t dus t i s no t supported . However , al l tha t

th e data , in fact , d o sho w i s tha t bot hgroup s o f

childre n wer e comparabl e a s t o th e amount s o f

210 P b an dvastl y differen t i n respec t

t o stabl e lea dpe r

gra mo f dr y excreta . Th e hospitalize d childre n ingeste dlarge r amount s o f

materia l con tainin g stabl e lead . Grantin g tha t th e hospitalize d childre n ingeste dleade dpain t chip s an dth e control s di dnot . doe s no t

permi t th e conclusio n tha t

al l th e 210 P b foun din al l th e childre n originate din foo d an dtha t n o dir t an ddus t

wa s ingeste db y contro l childre n wherea s hospitalize dchildre n at e onl y pain t chips . Th e dat afro mal l thes e studie s ca n b e summarize d fairl y succinctly . Ther e i s evidenc e tha t childre n ca n pick u p lea dfro mthei r

environmen t

b y gettin g i

t o n thei r hands . Dugga n an dWilliams 10 5 hav e sum marize dth e literatur e o n th e amount s o f lea din

geste db y ingestio n o f

dust . I n thei r

opinion , aquan tit y o f 5 0 M g o f lea di s ingeste ddail y b y childre n b y mean s o f stree t dust . A s yet

ther e ar e n o soli ddat a directl y demonstratin g th e nex t link , tha t

is , transfe r o f dus t an dsoi l fro mhan dt o mouth . A clinica l cas e repor t ha s indicated , however , tha t soi l lea dlevel s ca n lea dt o excessivel y elevate dbloo dlea dlevels . Also , th e dat ao f

Barltrop 10 1 an dGalk e e t al. 4 3 indi

cat e tha t soi l lea dexposures , ofte n foun din urba n settings , ca n contribut e betwee n 5 an d8 figldl t o th e blood' s lea dburden. 3310 1 Th e consensu s appear s t o b e tha t observabl e in- , crease s in bloo dlea dlevel s occu r a t soi l o r dus t lea d exposure s o f

50 0 t o 100 0 ppm . Fro mth e dat aavail

abl e in th e literature , asummar y tabl e (Tabl e 12-35 ) wa s constructe db y EPA . A regressio n analysi s wa s use dt o relat e th e logarith mo f th e 12-3 1P.4 1



### bloo dleadt o th e logarith mo f th e soil lead . Fro m th e regression , acoefficient , b , th e mea n percen t ag e increas e i n bloo dlea

dfo r atw o fol dincreas e i

n soil TABLE 12-35 . SUMMAR

YO F SOI L LEAD/BLOO D LEAD RELATIONSHIP S 

### lead , ca n b e calculated : % increas e = 10

0 [exp(b/lo g (2)) ] (12-7 )

Stud y Age , years Regressio n coefficient , log-lo g Geom . mea n bloo d lead , ug/d l Geom . mea n soi l level . »g/ g Mea n % increas e

i n Pb- B fo r 2 x soi l leve l Charleston.SC 4 3 Kellogg , ID 1 Dallas , TX 3 4 England 10 1 1- 5 1- 9 1- 5 2-3 0.043 2

0.052 8 0.066 2 0.084 0 36. 4 37. 5 11. 4 23. 2 451. 6

1518. 1 91. 6 1849. 1 3. 0

3. 7 4. 7 6. 0 

### Tabl e 12-3 5 show s asurprisin g consistenc y i n th e percentag e increas e i

n mea n bloo dleadlevel s for

a twofol dincreas e i

n soi l leadlevel s ( 3 t o 6 percent) , given th e wide diversity i n population s studie dand soi l level s encountered . Th e Charlesto n study in

volve dblac k

preschoo l childre n livin g i n th e inner cit y wit hseveral additiona l known environmenta l source s of lead . Th e Idah o study was o f asmelter site i n arura l setting . Barltrop' s dat afro mEnglan d showedvirtuall y n o environmenta l sourc e othe r than that fro msoil . Th e Dalla s study was o f acom munit y tha t wa s relativel y leadfree . It i s interestin g t o note tha t

th e larger

estimate s o

f th e percentag e in

creas e i n bloo dleadoccurre di

n th e childre n wit

h th e lowes t bloo dlea

dlevels . 12.3. 3 Food an

d Wate rExposures In typical urban settings , foodprobabl y con stitute s th e body' s larges t direc t sourc e o

f lea d becaus e almos t

ever y ite mi n th e die t contain s som

e measurabl e amoun t

o f th e metal . Thre e approache s hav e been usedt o estimat e die

tary intake o

f lead : duplicat e meals , marke t basket surveys , an dfeca

l leaddeterminations. Th e esti

mate ddietar y lea dintak e of American s ha s decrease dmarkedl y sinc e th e presentatio n of Kehoe' s dat ai

n th e 1940's , whichindicated , base d o n feca l leaddeterminations , that th e dail y intake was between 100 an d35 0 fig/day. 88 

### Mos t o f th e more recent

comparabl e data 210911 0 

### hav e reduce d that estimate t o between 5 0 an d15 0 Mg/day . Th e Californi astudy o

f Johnso n e

t al. 7 

### point s t o adail y intake o f abou t 10 0 t o 15 0 Mg . suc

hintake bein g simila r for bot hrura l an durban populations . Also , Chishol man dHarrison, 10 9 

### i n astudy o

f childre n aged1 2 t o 3 5 months , foundamea n feca l excretio n rat e o f 13 2 Mg/day , an dBarltro p an dKillol aavalu e o f 130Mg- 11 0 

### Muchrecent

wor k ha s been concerne dwit hth e leadconten t

o f th e marke t

basket o r tota l die t

i n whichth e conten t

o f food s meetin g typical nutri

tiona l need s i s analyzed . Th e foodstuff s ar e assem ble di n accordanc e wit

hnationa l foo dsampl e sur veys . On e suchstudy 11111 2 

### ha s indicate dthat th e leadconten t

o f th e die t o f youn g adult s average s 15 0 t o 20 0 Mg/day , andanother 11 3 

### cite s afigur e o f 25 4 Mg/da y fo r 15

- t o 20-year-ol dmales . A t leas t 3 0 per cent o f thi s amoun t

i n th e latte r

study was attribute d t o th e consumptio n o

f canne dfoods . Kolbye 11 1 

### an d Mahaffe y et al. 11 2 

### hav e suggeste da

n averag e food

base dintake o

f 8 0 t o 100 M

g o f leadfo r childre n 1 2 t o 3 5 month s old . Additiona l studie s i n thi s field hav e been reviewe db

y Mahaffey. 11 2 

### Despite th e abov e estimate s o f dietary leadcon tent , th e quantitativ e relationshi p between dietary intake an dbloo dlea

dlevel s i s no t

well established ; th e bulk o f th e studie s describe di

n Chapte r 1 0 that addres s thi s relationship , however , point t o asus taine dvalu e o

f 6 figldl fo r 10 0 M g o f dietary leadin

take . Water , itself

, ca n als o b e asourc e o

f significant quantitie s o

f leadwit hth e metal present

i n th e sup ply itself . Mor e frequent , however , i s a n increas e i

n th e quantity o

f particulat e or

dissolve dleada s water i s delivere dfro

mth e treatmen t

plan t t o th e use

r throug hth e leadpipe s ofte n foundi n olde r housing . Mos t natura l water s contai n onl y fro m1 0 t o 2 0 Mg/lite r o f leadan dmos t

problem s occur

whe n lead pipin g i s usedi

n area s i n whichth e drinkin g water i s lea dsolvent ; tha t

is , i t i s sof t an dha s alow pH . Althoug hth e us e o

f lea dpipin g ha s been largel y prohibite din recen t

construction , occasiona l episode s o

f poisonin g fro

mthi s leadsourc e stil l oc cur . Thes e case s mos t

frequentl y involv e isolate d farm s o r house s i n rura l areas , but

asurprisin g situa

tio n was reveale di

n 197 2 whe

n Beatti e et

al. 114



### - 11 5 

### showedth e seriousnes s o

f th e situatio n i

n Glasgow , Scotland , whichha

dver y pur e bu t

sof t drinkin g water a s it s source . They demonstrate daclear asso ciatio n between bloo dlea dlevel s an dinhibitio n o

f th e enzyme ALA D i

n childre n livin g i

n house s wit

h (1 ) leadwater

pipe s an dleadwater

tanks , (2 ) n o 12-3 2lea dwate r tan k bu t withmor e tha n 6 0 f

t o f lea dpip

ing , an d(3 ) les s tha n 6 0 f t o f lea dpiping . Th e mea n lea dconten t

o f th e wate r

a s supplie db y th e reservoi r wa s 17. 9 figlliler; tha t take n fro mth e faucet s o f group s 1 , 2 , an d3 wa s 934 , 239 , an d10 8 Mg/l'ter , respectively . Anothe r Englis hstudy 1 1 6 showe daclea r differenc e betwee n th e bon e lea dconten t o f th e population s o f

Glasgo w an dLondon , th e latte r hav

in g ahard , relativel y nonsolven t wate r supply.

- I n astud y o f

120 0 bloo ddonor s in Belgium, 11 7 person s fro mhome s withlea dpipin g an dsupplie d withcorrosiv e wate r

ha dsignificantl y highe r bloo d lea dlevels . I n Boston , Mass. , an investigatio n wa s mad e o f wate r distribute dvi alea dpipes . I n additio n t o th e dat ao n lea din water , accoun t wa s take n o f socioeconomi c an ddemographi c factor s a s wel l a s othe r source s o f

lea din th e environment. 11811 9 Par

ticipants , 77 1 person s fro m38 3 households , wer e classifie dint o ag e group s o f <6 , 6 t o 20 , an d>2 0 year s o f ag e fo r analysis. 11 8 A clea r

associatio n be

twee n wate r

lea dan dbloo dlea dwa s apparen t (Ta

bl e 12-36) . Fo r

childre n unde r

6 year s o f

age , 34. 6 percen t o f thos e consumin g wate r withlea dabov e th e U.S . standar do f

5 0 Mg/'i te r

ha dabloo dlea d valu e 2 3 5 figldl. wherea s onl y 17. 4 percen t o f thos e consumin g wate r

withi n th e standar dha dbloo dlea d valuesof23 5 figldl. TABL E 12-36 . BLOO D LEA D LEVEL S O F 77 1 PERSON S I N RELATIO N T O LEA D CONTEN TO F DRINKIN G WATER ,

BOSTON , MASS. 11 8 Person s consumin g wate r(standin g gra b samples ) Bloo d lea d levels , /jg/d l <50ii g Pb/lile r f5G>gPb/lite r No . Percen t Percen t Tota l <3 5 >3 5 Tota l 62 2

6 1 68 3 9 1

9 10 0 6 8

2 0 8 8 77. 3

22. 7 100. 0 69 0

8 1 77 1

x = 14.35 ; d l = 1 . P <0.01 . Greathous e e t

al . hav e publishe da n extensiv e regressio n analysi s o f

thes e data. 11 9 Bloo dlea d level s wer e foun dt o b e significantl y relate dt o age , educatio n o f

hea do f household , sex , an dwate r lea d exposure . O f

th e tw o type s o f

wate r sample s taken , standin g gra b an drunnin g grab , th e forme r wa s show n t o b e mor e closel y relate dt o bloo dlea d level s tha n th e latter . A s note din Chapte r

1 0 o f thi s document , roughl y 1 0 percen t

o f lea di n soli dfoodstuffs i s absorbe db y adults ; th e correspondin g valu e fo r liquid s i s abou t 5 0 percent . Th e relativ e ris k fo r exposur e t o water born e lea dis , therefore , considerabl y greater . 12.3. 4 Effect s o f Lea d i n th e Housin g Environ ment : Lea d i n Pain t A majo r sourc e o f

environmenta l lea dexposur e fo r th e genera l populatio n come s fro mlea dcon taine di n bot hinterio r

an dexterio r

pain t o n dwell

ings . Th e amoun t

o f lea dpresent , a s wel l a s it s ac cessibility , depend s upo n th e ag e o f th e residenc e (becaus e olde r

building s ar e painte dwithpain t manufacture dbefor e lea dconten t wa s regulated ) an dth e physica l conditio n o f th e paint . I t

i s generall y accepte db y th e publi c an db y healt hpro fessional s tha t

lea dbase dpain t

i s th e majo r

sourc e o f pediatri c lea dpoisonin g withclinica l symptom s in th e Unite dStates. 12 0 Th e leve l an ddistributio n o f lea dpain t

in adwell

in g i s acomple x functio n o f history , geography , eco nomics , an dth e decoratin g habit s o f it s residents . Lea dpigment s wer e th e firs t pigment s produce do n a larg e commercia l scal e whe n th e pain t industr y bega n it s growt hin th e earl y 1900's . I n th e 1930' s lea dpigment s wer e graduall y replace dwithzin c an d othe r opacifiers . B y th e 1940's , titaniu mdioxid e becam e availabl e an dha s no w becom e th e mos t commonl y use dpigmen t fo r residentia l coatings . Ther e wa s n o regulatio n o f th e us e o f

lea di n hous e paint s unti l 1955 , whe n th e pain t industr y adopte da voluntar y standar dtha t limite dth e lea dconten t in paint , fo r interio r uses , t o n o mor e tha n 1 percen t b y weigh t o f th e nonvolatil e solids . A t abou t th e sam e time , loca l jurisdiction s bega n adoptin g code s an d regulation s tha t

prohibite dth e sal e an dus e o f in

terio r paint s containin g mor e tha n 1 percen t lead. 12 1 I n spit e o f

th e chang e i n pain t

technolog y an d loca l regulation s governin g it s use , an dcontrar y t o popula r belief , interio r

pain t wit hsignifican t amount s o f

lea dwa s stil l availabl e in th e 1970's . A 197 1 stud y in Ne w Yor k Cit y foun dtha t

8 o f 7 6 paint s teste dha dalea dconten t rangin g fro m2. 6 t o 10. 8 percent , wel l abov e th e city' s legall y permissi

bl e 1 percen t

level. 12 2 Late r

studie s b y th e Nationa l Burea u o f

Standards 12 3 an db y th e Consume r Pro

duc t Safety Commission 12 4 showe dacontinuin g decreas e i n th e numbe r o f interio r paint s wit hlea d level s greate r

tha n 1 percent . B y 1974 , onl y 2 per cen t o f th e interio r

paint s sample dwer e foun dt o hav e greate r

tha n 1 percen t

lea din th e drie dfilm. 12 4 Th e leve l o f

lea din pain t

in aresidenc e tha t shoul db e considere dahazar dremain s i n doubt . No t onl y i s th e tota l amoun t o f lea din pain t

important , bu t als o th e accessibilit y b y achil do f th e painte d 12-3 3P.4 3

surfac e a s wel l a s th e frequenc y o f ingestion . At

tempt s t o se t

a n acceptabl e lea dlevel , in situ, hav e bee n unsuccessfu l an dpreventiv e contro l o f lea d pain t hazard s ha s bee n concerne dwit hlevel s o f lea d in pain t currentl y manufactured . I n on e o f it s reviews , NA S concluded : '"Sinc e contro l o f th e lea d pain t hazar di s difficul t

t o accomplis honc e multipl e layer s hav e bee n applie din home s ove r tw o t o thre e decades , an dsinc e contro l i s mor e easil y regulate d at th e tim e o f

manufacture , w e recommen dtha t th e lea dconten t

o f paint s b e se t

an denforce dat

tim e o f manufacture." 12 5 Lega l contro l o f

lea dpain t

hazard s i s bein g at tempte db y loca l communitie s throug hhealt ho r housin g code s an dregulations . A t th e Federa l level , th e Departmen t

o f Housin g an dUrba n Develop

men t ha s issue dregulation s for lea dhazar dabate

men t in housin g unit s assiste do r supporte db y it s programs . Generally , th e lea dleve l considere d hazardou s range s fro m0. 5 t o 2. 5 mg/cm 2 , bu t th e leve l o f lea dconten t

selecte dappear s t o b e depen

den t mor e o n th e sensitivit y o f fiel dmeasuremen t

b y differen t regulator y bodie s (usin g X-ra y fluorescen t lea ddetectors ) tha n o n direc t biologica l dose

respons e relationships . Regulation s als o requir e lea dhazar dabatemen t

whe n th e pain t

i s loose , flak

ing , peeling , o r

broken , o r

i n som e case s whe n it

i s o n surface s withi n reac ho f achild' s mouth . Som e studie s hav e bee n carrie dou t t o determin e th e distributio n o f

lea dlevel s in pain t

in residences . A surve y o f

lea dlevel s in 237 0 randoml y selecte d dwelling s i n Pittsburg hprovide s som e indicatio n o f th e lea dlevel s t o b e found. 12 6 Figur e 12- 9 show s th e distributio n curve s fo r

th e highes t

lea dleve l foun d in dwelling s fo r

thre e ag e groupings . Th e curve s bea r ou t th e statemen t

ofte n mad e tha t

pain t withhig h level s o f lea di s mos t

frequentl y foun di

n pr e 194 0 residences . On e canno t assume , however , tha t hig h leve l lea dpain t

i s absen t

i n dwelling s buil t

afte r 1940 . I n th e cas e o f

th e house s surveye din Pitts

burgh , abou t

2 0 percen t

o f th e residence s buil t

afte r 196 0 hav e at

leas t on e surfac e withmor e tha n 1. 5 mg/cm 2 lead . Th e distributio n o f

lea dwithi n a n individua l dwellin g varie s considerably . Figur e 12-1 0 present s th e distributio n o f

th e highes t

pain t lea dmeasure ment s o n walls , doors , an dwindow s fo r al l th e building s sampled . Thes e dat asho w tha t th e lea di s no t uniforml y distribute dthroughou t th e units . Lea d pain t i s mos t frequentl y foun do n door s an dwin

dow s wher e lea dlevel s greate r tha n 1. 5 mg/cm 2 wer e foun do n 2 percen t

o f th e surface s surveyed , wherea s A l

LEA D LEVE L (X) . mg/c m Figur e 12-9 . Cumulativ e distributio n o f lea d level s i n dwellin g units:* " onl y abou t

l percen t

o f th e wall s ha dlea dlevel s greate r tha n 1. 5 mg/cm 2

. 12 6 Th e literature 12 0 generall y accept s th e premis e tha t th e presenc e o f

lea din pain t

i s anecessar y bu t no t sufficien t

conditio n fo r

ahazar dt o b e present . Accessibilit y in term s o f peeling , flaking , o r

loos e pain t i s als o anecessar y conditio n fo r th e presenc e o f ahazard . Figur e 12-1 1 show s th e distributio n o f lea dlevel s an dnonintac t condition s fo r

dwelling s an dsurface s fo r

th e Pittsburg hsample . O f th e tota l sample s surveyed , abou t 1 4 percen t

o f th e residence s woul dhav e accessibl e pain t wit halea dconten t greate r tha n 1. 5 mg/cm 2

. I t i s no t possibl e t o extrapolat e th e result s o f th e Pittsburg hsurve y nationally ; however , additiona l dat afro mapilo t

stud y o f 11 5 residence s i n Wash

ington . D.C . showe dsimila r results. 12 7 A n attemp t

wa s mad e i

n th e Pittsburg hstud y t o obtai n informatio n abou t th e correlatio n betwee n 12-3 4A l 

### 1

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0. 8

0. 7

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## 1 M 1 M " 1 \ \ 1 * K 1 M - 1 \ \ I VjW-DOOR S 

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_

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-

LEA D LEVE L (X) , mg/c m Figur e 12-10 . Cumulativ e distributio n o l lea d level s b y loca tio n i n dwelling , al l ages. 12 6 th e quantit y an dconditio n o f lea dpain t

i n building s an dth e bloo dlea do f

childre n wh o reside dthere. 12 8 Bloo dlea danalyse s an dsocioeconomi c dat afor 45 6 childre n wer e obtaine dalon g withth e informatio n abou t lea dlevel s in th e dwelling . Figur e 12-1 2 shows-th e cumulativ e distributio n o f th e bloo dlea d level s fo r thi s group . Figur e 12-1 3 i s aplo t o f th e bloo dlea dlevel s versu s th e fractio n o f surface s withi n adwellin g wit hlea dlevel s o f a t leas t 2 mg/cm 2

. Analysi s o f

th e dat ashow s alo w correlatio n betwee n th e bloo dlea dlevel s o f th e childre n an d fractio n o f

surface s withlea dlevel s abov e 2 mg/cm 2 , bu t astronge r

correlatio n betwee n th e bloo dlea d level s an dconditio n o f th e painte dsurface s in th e dwellin g i n whic hchildre n reside . Thi s latte r cor relatio n appeare dt o b e independen t o f th e lea d level s i n th e dwellings . Tw o othe r

studie s hav e attempte dt o relat e bloo d lea dlevel s an dpain t

lea da s determine db y X-ra y fluorescence . Reec e e t

al . in Cincinnat i studie d8 1 LEA D LEVE L (XI . mg/cm * Figur e 12-11 . Cumulativ e distributio n o f lea d level s i n dwell in g unit s wit h unsoun d pain t conditions. 12 6 childre n fro mtw o lowe r socioeconomi c com munities. 12 9 Bloo dlead s wer e analyze db y th e dithizon e method . Ther e wa s considerabl e lea din th e hom e environment , bu t i t wa s no t reflecte din th e children' s bloo dlead . Analyti c procedure s use dt o tes t th e hypothesi s wer e no t described ; neithe r

wer e th e ra w dat apresented . Galk e e t al . in thei r

stud y o f

inner-cit y blac k childre n measure dth e pain t lead , bot hinterio r

an d exterior , a s wel l a s soi l an dtraffi c exposure. 4 3 I n a multipl e regressio n analysis , exterio r sidin g pain t lea dwa s foun dt o b e significantl y relate dt o bloo d lea dlevels . Althoug hmos t

o f th e evidenc e indicate s tha t th e sourc e o f exposur e i n childhoo dlea dpoisonin g i s almos t invariabl y peelin g lea dpain t an dbroke n lead-impregnate dplaste r foun din poorl y main

12-3 5P.4 5

5 io o 5 8 0 "TT " ~n —r—i—i i i i i i i—i—i— i i i i i i - |

STD . DEV. = 1.3 9 MEDIA N =20.7wg/d l

\ III I IIIII1 IIIII Figur e 12-12 . Cumulativ e frequenc y distributio n o f bloo d lea d level s foun d i n Pittsburg h housin g survey. 12 6 

### Th e finding s ar e presente di n orde r t o plac e i

n prope r perspectiv e bot

hth e concep t

o f tota l leadex posure an dth e concep t

that lea dpain t i s on e sourc e o f leadtha t contribute s t o th e tota l bod y load . Th e backgroun dcontributio n o f leadfro mothe r source s i s stil l no t known eve

n fo r thos e childre n fo

r who ma potential lead-pain t

hazardha s been identified ; nor i s i t known wha

t proportio n o

f leadcame fromwhich source . TABL E 12-37 . RESULT S O F SCREENIN G AN D HOUSIN G INSPECTIO N I N CHILDHOO D LEA D POISONIN G CONTRO L

PROJEC TB YFISCA L YEAR" 1 . 1 "

z > U J LJ J

Q 2 0 O o I I I I I I I I

SURFACE S I N BA D CONDITION , i.e. , PEELIN G

_CHALKING , O R POO R SUBSTRAT E

AL L SURFACE S * •

I I I I •

' I I I o I I

-

—— •—

I Fisca l year 8

Result s 1976' " 197513 ' 1974" '

0 0. 1 0. 2 0. 3 0. 4 0. 5 0. 6 0. 7 0. 8 0. 9 1. 0

FRACTION S O F SURFACE S WIT H LEA D > 2 mg/cm 2 Figure 12-13 . Correlatio n of children' s bloo d lea d level s wit h fraction s of surface s withi n a dwellin g havin g lea d concentra tion s 2 2 m g Pb/cm 2 . 

### taine dhouses , ther e ar e als o report s o f exposure case s that canno t b e equate dwit

hth e presenc e o

f leadpaint . Further , th e analysi s o f pain t i n home s o f childre n wit

hleadpoisonin g ha s no t consistentl y reveale dahazardou s leadcontent. 12 0 

### For example , on e paper reporte d546 6 sample s o f pain t obtaine d fro mth e home environmen t o f leadpoisonin g case s i n Philadelphi abetween 196 4 an d1968 . Amon g thes e 546 6 sample s o

f paint , 6 7 percen t

yielde dposi

tiv e finding s define da s pain t wit hmore than 1 per cent lead. 13 0 

### Dat apublishe do r

mad e availabl e b

y th e Center fo r Diseas e Control , Departmen t o f Health , Educa

tion , an dWelfare , als o show that asignificant

num be r o f childre n wit

hundu e lea

dabsorptio n occup y building s that

wer e inspecte dfo

r lead-base dpaint hazards , bu t

i n whichno hazar dcoul db e demon

strated. 13113 2 

### Tabl e 12-3 7 summarize s th e dat aob

taine dfro

mth e HE

Wfundedlead-base dpaint poisonin g contro l project s fo r fisca l year s 1974 , 1975 , an d1976 , plu s th e transitio n quarte r Jul y 1 , 197 6 t o September

30 , 1976 . Thes e dat ashow that i n abou t 4 0 t o 4 5 percen t

o f confirme dcase s o

f ele

vate dbloo dleadlevels , apossibl e sourc e o f lea d pain t hazar dcoul dno t

be located . Th e implication s o f thes e finding s ar e no t

clear . They shoul dnot , however , weaken th e rol e o f lead-base dpain t

a s a major environmenta l sourc e o f leadfo r children . No . childre n

screene d No . childre n wit h elevate d lea d exposur e No . dwelling s inspecte d No . dwelling s wit h lea d hazar d 500,46 3 440,65 0 371,95 5 69,131 " 28,5971 = 16,228< = 50,27 6 30,22 7 23,09 6 28,33 3 17,60 9 13,74 2

a Fisca l yea r197 6 include s transitio n quarter . b CD C Classe s ll-IV . 0 Confirme d bloo d lea d leve l if"4 0 ug/dl . 

### 12.3. 5 Secondary Exposur e o f Childre n from Parents ' Occupationa

l Exposure Excessiv e intake an dabsorptio n o f leadfo r childre n ca

n resul t whe n aparen t

who work s i

n a dust y environmen t

wit hahig hleadconten t

bring s dus t home on hi s clothes , shoes , o r even hi s automo bile . Onc e home , thi s dus t i s the n availabl e t o hi s children . Excessiv e intake andabsorptio n als o ca n occur whe n childre n voluntaril y inges t nonfoo ditems , suc has clay , plaster , or

pain t chips . Thi s i s th e classi

ca l pica , whichrefer s t o th e intentional ingestio n o f nonfoo dmateria l rathe r

than t o th e passive , nonin

tentiona l ingestio n o

f dus t fro madirty finge

r o r piec e o f candy that

ha s been droppe dan dthu s con taiminated . Landrigan e

t al. 6 2 

### reporte dthat

th e 174 childre n o f smelter worker s who live dwithi n 2 4 k mo f th e smelter hadsignificantly higher

bloo dleadlevels , a mea n o f 55. 1 figldl, than th e 51 1 childre n o f person s i n othe r occupation s wh

o live di n th e same area s whos e mea

n bloo dleadlevel was 43. 7 figldl. Analyse s b

y EP A staf f o f th e dat acollecte di

n Idah o showedthat

employment

o f th e father

a t th e lea dsmelter , a

t azin c smelter , o r

i n th e leadmin e 12-3 6resulte din highe r bloo dlea dlevel s in th e childre n livin g in th e sam e hous e withsuc hfather s tha n childre n whos e father s wer e employe din differen t location s (Tabl e 12-38) . TABL E 12-38 . GEOMETRI C MEA N BLOO D LEA D LEVEL S (Mg/dl ) O F CHILDRE N BY PARENTA L EMPLOYMEN T

(EP A analysi s o

f 1974 data ) Ag e an d stud y are a 1 t o 3 year s 1 2 3 4 5 6 4 t o 9 year s 1 2 3 4 5 6 Lea d smelte r

worke r 77.1(12)= * 56.8(11 ) 33.7(6 ) 29.6(4 ) — — 73.6(32 ) 49.6(21 ) 33.3(21 ) 30.9(4 ) 24.5(2 ) — Lead/zin c

min e worke r 65.7(25 ) 53.5(21 ) 54.5(15 ) 36.0(16 ) 31.8(29 ) — 65.8(28 ) 43.8(32 ) 35.5(39 ) 33.0(53 ) 27.1(79 ) — Zin csmelte r

worke r 66.3(11 ) 55.1(6 ) 32.3(2 ) 41.7(4 ) — — 59.3(16 ) 51.9(4 ) 35.2(7 ) 35.6(5 ) — — Othe r

occupatio n 65.9(13 ) 48.5(30 ) 34.8(26 ) 31.5(22 ) 27.2(16 ) 22.4(34 ) 59.2(33 ) 44.9(67 ) 32.1(58 ) 29.1(44 ) 26.4(60 ) 20.5(56 )

a Sampl e size s i n parentheses . Th e effec t

associate dwit hparenta l employmen t appear s t o b e muc hmor e prominen t in th e mos t

con taminate dstud y area s neares t t o th e smelter . Thi s ma y b e th e effec t

o f a n intervenin g socioeconomi c variable : th e lowes t

pai dworkers , employe di n th e highes t exposur e area s withi n th e industry , migh t b e expecte dt o liv e i n th e mos t undesirabl e locations , whic har e closes t

t o th e smelter . Th e importanc e o f

th e infiltratio n b y lea ddust s int o clothing , particularl y th e undergarments , o f lea dworker s ha s bee n demonstrate di n anumbe r o f studie s o f

th e effect s o f

smelters. 13 3 I t

wa s note di n th e Unite dKingdo mtha t elevate dbloo dlea dlevel s wer e foun di n th e wive s an dchildre n o f worker s eve n whe n the y reside dsom e considerabl e distanc e

fro mth e facility . I t

wa s mos t

prominen t

i n th e familie s o f

worker s wh o themselve s ha delevate d bloo dlea dlevels . Quantitie s o f lea ddus t wer e foun d in workers ' car s an dhomes . I t apparentl y i s no t sufficien t fo r afactor y merel y t o provid e oute r pro tectiv e clothin g an dshowe r facilitie s fo r

lea d workers . I n anothe r

stud y in Bristol , fro m65 0 t o 140 0 pp mo f

lea dwa s foun di n th e undergarment s o f worker s a s compare dwit h3 t o 1 3 pp mi n undergar

ment s o f contro l subjects . Lea ddus t wil l remai n o n th e clothin g eve n afte r

laundering : u p t o 50 0 m g o f lea dha s bee n foun dt o remai n o n a n overal l garmen t afte r washing. 13 4 Bake r e t al. 13 5 foun dbloo dlea dlevel s >3 0 figldl in 3 8 o f 9 1 childre n whos e father s wer e employe da t asecondar y lea dsmelte r in Memphis , Tenn . House

dust , th e onl y sourc e o f lea di n th e home s o f

thes e children , containe damea n o f 268 7 figlg compare d with40 4 figlg i n th e home s o f agrou p o f

matche d controls . Mea n bloo dlea dlevel s in th e workers ' childre n wer e significantl y highe r tha n thos e fo r control s an dwer e closel y correlate dwit hth e lea d conten t o f househol ddust . I n home s wit hlea di n dus t < 100 0 figlg, 1 8 childre n ha damea n bloo d lea dleve l o f

21. 8 ± 7. 8 figldl, wherea s i n home s wher e lea din dus t

wa s >700 0 figlg, 6 childre n ha d amea n bloo dlea dleve l o f 78. 3 ± 34. 0 figldl. Landriga n e t

al. 6 2 als o reporte dapositiv e histor y o f pic afo r 19 2 o f th e 91 9 childre n studie di n Idaho . Thi s histor y wa s obtaine db y physicia n an dnurs e in

terview s o f

parents . Pic awa s mos t commo n amon g 2-year-ol dchildre n an donl y 1 3 percen t o f thos e withpic awer e abov e ag e 6 . Highe r bloo dlea dlevel s wer e observe di n childre n wit hpic atha n i n thos e withou t pica . Tabl e 12-3 9 show s th e mea n bloo d lea dlevel s i n childre n a s the y wer e affecte db y pica , occupatio n o f

th e father , an ddistanc e o f residenc e fro mth e smelter . I t

i s interestin g that , amon g th e TABL E 12-39 . GEOMETRI C MEA N BLOO D LEA D LEVEL S FO R CHILDRE N BASE D O N REPORTE D OCCUPATIO N O F FATHER , HISTOR Y O F PICA , AN D DISTANC E O F RESIDENC E FRO M SMELTER "

Are a 1 2 3 4 5 6 Distanc e Iro m smeller , k m 1. 6 1. 6 t o 4. 0 4. 0 t o 10. 0 10. 0 t o 24. 0 24. 0 t o 32. 0 75 . Pic a

78. 7 50. 2 33. 5 — — — Lea d smelte r worke r N o

pic a 74. 2 52. 2 33. 3 30. 3 24. 5 — Lead/zin cmin e

Pic a 75. 3 57. 1 36. 7 38. 0 31. 8 — worke r N o

pic a 63. 9 46. 9 33. 5 32. 5 27. 4 — Zin csmelte r

Pic a 69. 7 62. 7 36. 0 40. 9 — — worke r N o

pic a 59. 1 50. 3 39. 6 36. 9 — — Othe r

occupation s N o Pic a pic a 70. 8 59. 9 37. 2 46. 3 33. 3 32. 6

—39. 4 28. 0 26. 4 17. 3 21. 4 12-3 7P.4 7

population s livin g neares t t o th e smelter , environ

menta l exposur e appear s t o b e sufficien t a t time s t o mor e tha n overshado w th e effect s o f pica , bu t

thi s findin g ma y als o b e cause db y inadequacie s inheren t i n collectin g dat ao n pica . Thes e dat aindicat e tha t in aheavil y contaminate d area , bloo dlea dlevel s in childre n ma y b e signifi

cantl y increase db y th e intentiona l ingestio n o f non foo dmaterial s havin g ahig hlea dcontent . Dat ao n th e parents ' occupation s are , however , mor e reliable . I t

mus t b e remembere dals o tha t th e stud y area s wer e no t homogeneou s socioeconomically . I n addition , th e typ e o f wor k an individua l doe s in an industr y i s probabl y muc h mor e importan t

tha n simpl y bein g employe din a particula r

industry . Th e presenc e i n th e hom e o f

an industria l employe e expose doccupationall y t o lea d may produc e increase s in th e bloo dlea dlevel s rang in g fro m1 0 t o 3 0 percent . 12.3. 6 Miscellaneou s Source s o f Lea d Althoug hn o studie s ar e available , it i s conceiva

bl e tha t destructio n o f

lead-containin g plastic s (t o recove r copper) , whic hha s cause dcattl e poisoning , als o coul dbecom e asourc e o f lea dfo r humans . A mor e genera l proble mi s wast e disposal , becaus e lead-containin g material s ma y b e incinerate dan d may thu s contribut e t o increase dai r lea dlevels . Thi s sourc e o f lea dha s no t

bee n studie din detail . Th e consumptio n o f

illicitl y distille dliquo r ha s bee n show n t o produc e clinica l case s o f lea dpoison

ing . Domesti c an dimporte dearthenwar e wit him

properl y fire dglaze s hav e als o bee n relate dt o clini

ca l lea dpoisoning . Thi s sourc e become s importan t whe n food s o r

beverage s hig hin aci dar e store din container s mad e fro mthes e material s becaus e th e aci drelease s lea dfro mth e wall s o f th e containers . Particula r

cosmetic s popula r

amon g som e Orien

ta l an dIndia n ethni c group s contai n hig hpercen tage s o f lea dtha t sometime s ar e absorbe db y user s in quantitie s sufficien t

t o b e toxic . 12. 4 SUMMAR Y Bloo dlea dlevel s i n homogeneou s huma n popula

tion s hav e almos t

invariabl y bee n foun dt o b e log

normal . A numbe r

o f suc hdat aset s wer e examine d an dthe y displaye dageometri c standar ddeviatio n (GSD ) rangin g fro m1. 3 t o 1.5 . Fro mth e lognorma l distribution , give n amea n bloo dlea dleve l an da n estimate dgeometri c stan dar ddeviation , i t

i s possibl e t o predic t

th e percen tage s o f apopulatio n whos e bloo dlea dlevel s excee d aspecifie dvalue . I t

i s als o possibl e t o estimat e th e likel y increas e in mea n bloo dlea dlevel s fo r a populatio n expose dt o specifi c increase s in environ

menta l lead . Couplin g thes e tw o procedure s pro vide s ametho db y whic hstandard s ma y b e chose n t o protec t th e healt ho f

th e population . Bloo dlea dlevel s hav e bee n foun dt o exhibi t con siderabl e geographi c variability . Generall y the y ar e lowes t in rura l settings , highe r in suburba n areas , an dhighes t

in inner-cit y areas . Thes e value s follo w th e presume dlea dexposur e gradient . Bloo dlea d value s wer e als o foun dt o var y b y age , sex , an drace , althoug hin asomewha t mor e comple x fashion . Generally , youn g childre n hav e th e highes t levels , withlittl e differenc e betwee n sexes . I n olde r seg ment s o f th e population , afte r

eliminatin g occupa tiona l exposur e in lea dworkers , male s hav e ahighe r bloo dlea dtha n females . Th e publishe ddat acom parin g th e bloo dlea dlevel s o f variou s racia l an d ethni c group s o f

th e populatio n sugges t tha t black s hav e highe r

bloo dlea dlevel s tha n whites , with Puert o Rican s sometime s at a n intermediat e level . Result s o f

th e numerou s studie s o f environmenta l exposure s o f

ma n hav e indicate dstrongl y tha t ma n doe s indee dtak e u p lea dfro meac hsourc e t o whic h h e i s exposed . Equall y important , thes e studie s hav e show n tha t

th e bloo dlea dleve l i s th e summatio n o f th e absorptio n fro meac ho f thes e sources . Dat afo r th e tw o mos t

widesprea denvironmenta l source s othe r

tha n foo dpermi t

summar y statement s concernin g thei r

quantitativ e relationshi p wit h bloo dlea dlevels : ratio s betwee n bloo dlea dlevel s an dai r lea dexposure s wer e show n t o rang e generall y fro m1: 1 t o 2:1 . Thes e wer e not , however , constan t ove r th e rang e o f

ai r lea dconcentration s encountered . Ther e ar e suggestiv e dat aindicatin g tha t th e ratio s fo r

childre n ar e in th e uppe r en do f th e rang e an dma y eve n b e slightl y abov e it . Ther e i s als o som e sligh t

suggestio n tha t

th e ratio s fo r

male s ar e highe r

tha n thos e fo r

females . Fo r soi l lea dexposures , aconsisten t associatio n wit hbloo dlea dlevel s ha s bee n established . Childre n expose dt o highe r soi l an dhousedus t

lea d concentration s hav e bee n show n t o hav e elevate d concentration s o f

lea do n thei r

hands , bu t

a n associ

atio n o f elevate dbloo dlea dlevel s wit helevate d han dlea dlevel s ha s no t ye t bee n established . Quan

titatively , bloo dlea dlevel s hav e bee n show n t o in

creas e 3 t o 6 percen t

whe n th e soi l o r

dus t lea dcon ten t i s doubled . Significan t

wate r lea dexposure s i n thi s countr y hav e occurre donl y in place s usin g leade dpipe s couple dwit hasof

t wate r supply . Suc hexposure s hav e bee n show n t o b e associate dwit hsignifican t 12-3 8elevation s o f bloo dlead . The y hav e als o bee n linke d t o case s o f

menta l retardation . Exposur e t o leade dpain t stil l comprise s aver y seriou s proble mfo r

America n childre n i n urba n set tings . Althoug hne w regulation s governin g th e lea d conten t o f pain t shoul dalleviat e th e proble mi n ne w housing , th e poorl y enforce dregulatio n an dlac k o f regulatio n o f

th e pas t hav e lef

t aheav y burde n o f lea dexposure s fro mpaint . Mos t o f th e studie s o n lea dpoisonin g in childre n hav e assume da n associ

atio n wit hleade dpaint , bu t ver y rarel y hav e thes e studie s measure dth e amoun t o f exposure . Ther e is , nevertheless , stron g suggestiv e evidenc e tha t th e contributio n fro mthi s sourc e ca n b e ver y significant . Lea dexposur e vi afoo di s though t t o b e th e sourc e o f asignifican t

portio n o f

bloo dlead . Direc t

quan titativ e equation s describin g th e relationshi p o f bloo dt o foo dlea dlevel s hav e no t bee n published , bu t studie s describe din Chapte r 1 0 d o addres s thi s relationship . 12. 5 REFERENCE S FO RCHAPTE R1 2 1 . Yankel , A . J. , I . vo n Lindern . an dS . D . Walter . Th e Silve r Valle y lea dstudy . Th e relationshi p betwee n childhoo d bloo dlea dlevel s an denvironmenta l exposure . J . Ai r Pollut . Cont . Assoc . 27:763-767 . 1977 . 2 . Tepper , L . B . an dL . S . Levin . A surve y o f ai r an dpopula

tio n lea dlevel s i n selecte dAmerica n communities . En

viron . Qual . an dSafe. , Supplemen t II : Lead . 152-195 , 1975 . "3 . Azar , A. , R . D . Snee . an dK . Habibi . A n epidemiologi c ap proac ht o communit y ai r lea dexposur e usin g persona l ai r samplers . Environ . Qual . an dSafe. , Supplemen t II : Lead . 254-288 , 1975 . 4 . Schubert , J. , A . Brodsky . an dS . Tyler . Th e lognorma l functio n a s astochasti c mol do f th e distributio n o f

stron tium-9 0 an dothe r

fissio n product s i n humans . In: Healt h Physics , Vol . 13 . Ne w York , Pergammo n Press . 1967 . p . 1187-1204 . 5 . Snee , R . D . Developmen t o f a n Ai r Qualit y Valu e fo r Lea dfro mCommunit y Studies . E . I . d u pon t d e Nemour s & Co. , Wilmington , Delaware . Technica l Repor t No . PLMR-3-77 . Januar y 1977 . 6 . Johnson . D . E. , J . B . Tillery , J . M . Hosenfeld , an dJ . W . Register . Developmen t o f Analyti c Technique s t o Measur e Huma n Exposur e t o Fue l Additives . Souther n Researc hInstitute , Sa

n Antonio , Texas . Prepare dfo r U.S . Environmenta l Protectio n Agency , Researc hTriangl e Park , Nort hCarolina . Publicatio n No . EPA-650/1-74

- 003 . Marc h1974 . 7 . Johnson , D . E. , J . B . Tillery . an dR . J . Prevost . Level s o f platinum , palladiu man dlea di n population s o f Souther n California . Environ . Hlth . Persp . /2:27-33 , 1975 . 8 . Aitchison , J . an d} . A.C . Brown . Th e Lognorma l Distribu

tion . London , Cambridg e Universit y Press . 1966 . 9 . Johnson , N . L . an dS . Kotz . Continuou s Univariat e Dis

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127 . Chisohlm , J . J. , Jr . an dH . E . Harrison . Th e exposur e o f childre n t o lead . Pediatr . 78:943-958 , 1956 . Barltrop , D . an dN . H . P . Killala . Feca l excretio n o f lea d b y children . Lancet . 2:1017-1019 , 1967 . Kolbye , A . C , K . R . Mahaffey , J . A . Fiorino , P . C . Cor

neliussen , an dC . F . Jelinek . Foo dexposur e t o lead . En

viron . Hlth . Persp . 7:65-74 , 1974 . Mahaffey , K . R . Quantitie s o f lea dproducin g healt h effect s i n humans : Source s an dbioavailability . Environ . Hlth . Persp . 79:285-296 , 1977 . Complianc e Progra mEvaluatio n F Y 197 4 Heav y Metal s i n Food s Surve y (7320.13C ) (Chemica l Contaminant s Project) . Burea u o f

Foods , U . S . Foo dan dDru g Adminis

tration , Washington , D . C . Jun e 19 , 1975 . 9 9 p . Beattie . A . D. , J . H . Dagg , A . Goldberg , I . Wang , an dJ . Ronald . Lea dpoisonin g i n rura l Scotland . Brit . Med . J . 2:488-491 , 1972 . Beattie . A . D. , M . R . Moore , W . T . Devenay , A . R . Miller , an dA . Goldberg . Environmenta l lea dpollutio n in a n ur ba n sof t wate r area . Brit . Med . J . 2:491-493 , 1972 . Crawford , M . D . an dT . Crawford . Lea dconten t o f bone s i n ahar dan dsof

t wate r area . Lancet . 7:699-701 , 1969 . D e Graeve , J. , D . Rondia , an dP . Jamin . Lea dconcentra tion s in drinkin g wate r an dbloo dlea dlevel s i n an adul t population . In: Proc . Inter . Symp . o n Recen t Advance s i n th e Assessmen t

o f th e Healt hEffect s o f Environmenta l Pollution , II . Luxembourg , Commissio n o f th e Europea n Communities . 1975 . p . 523-535 . Worth , D . Lea di n drinkin g water , apubli c healt hprob

le mwit hasolution . J . Amer . Publi c Healt hAssoc . (I n press) . 1977 . Greathouse . D . G. , G . F . Craun , an dD . Worth . Epidemiologica l stud y o f th e relationship s betwee n lea di n drinkin g wate r

an dbloo dlea dlevels . In: Trac e Substance s i n Environmenta l Health . X . D . Hamphill , (ed.) . Colum

bia , Universit y o f

Missour i Press . Lin-Fu . J . S . Vulnerabilit y o f childre n t o lea dexposur e an dtoxicity . Ne w Englan dJ . Med . 289:1229-1233 , 1289-1293 . 1973 . Berger . H . W . Th e NB S lea dpain t poisonin g project : Housin g an dothe r

aspects . Nationa l Burea u o f Standards , Gaithersburg , Maryland . Technica l Not e No . 759 . Febru

ar y 1973 . Bird , D . Ne w Yor k

Times , Augus t

8 , 1971 . Lea dPain t

Surve y Samplin g Pla n an dPreliminar y Screen

in g Repor t

10958 . Nationa l Burea u o f Standards , Gaithersburg , Maryland . 1973 . A Repor t t o Congres s in Complianc e wit hth e Lea dBase d Pain t Poisonin g Preventio n Act . Consume r Produc t Safety Commission , Washington , D . C . Decembe r 1974 . Recommendation s fo r

th e Preventio n o f

Lea dPoisonin g i n Children . Assembl y o f Lif e Sciences , Nationa l Academ y o f Sciences , Washington , D . C . Jul y 1976 . 8 5 p . Shier , D . R . an dW . G . Hall . Analysi s o f Housin g Dat a Collecte di n aLead-Base dPain t Surve y i n Pittsburgh , Pennsylvania . Nationa l Burea u o f Standards , Washington , D . C . (I n preparation. ) 1977 . Hall , W. , T . Ayers , an dD . Doxey . Surve y Plan s an dDat a Collectio n an dAnalysi s Methodologies : A s aResul t o f a Pre-Surve y fo r

th e Magnitud e an dExten t o f th e Lea d Base dPain t

Hazar di n Housing . Nationa l Burea u o f Stan

dards , Gaithersburg , Maryland . Repor t No . NBSI R 74-426 . Januar y 1974 . 12-4 2128 . Urban , W . D . Statistical Analysi s o f Bloo dLea

dLevel s o f Childre n Surveyedi

n Pittsburgh , Pennsylvania : Analytical Methodolog y andSummar y Results . Fina

l contrac t re port . Contrac t

IAA-H-35-75 . Department o f Housin g and Urba n Development , Washington , D . C . Apri l 1976 . 129 . Reece , R . M. , J . A . Reed , C . S . Clark , R . Angoff , K . R . Casey , R . S . Challop , andE . A . McCabe . Elevate dbloo d lea dlevel s andth e in situ analysi s o f wall paint

b y X-ra y fluorescence . Amer . J . Dis . Child . 724:500-502 , 1972 . 130 . Tyler , R . L . Philadelphi acombat s "silent epidemic " i

n th e "ghetto " leadpoisonin g control . J . Environ . Hlth . 55:64-71 , 1970 . 131 . Hopkins , D . R . andV . N . Houk . Federally-assiste d screenin g project s fo

r childhoo dlea

dpoisonin g control : Th e firs t thre e year s (July 1972-Jun e 1975) . Amer . J . Publi c Hlth . 66:485-486 , Ma y 1976 . 132 . Morbidity andMortality Weekl y Report . Departmen t

o f Health , Education , andWelfare , Rockville , Maryland . February 11 , 1977 . 1 33 . Martin , A . E. , F . A . Fairweather , R . St . J . Buxton , andR . M . Roots . Recent

Epidemiological Studie s o f Environ

menta l Lea do f Industria l Origin . Luxembourg , Commis

sion o f th e Europea

n Communities . 1975 . 134 . Medical Aspect s o

f Lea dAbsorptio n i

n Industria l Pro

cesses . Lea

dDevelopment

Assoc , London , England . 1973 . 135 . Baker , E . L. , D . S . Folland , T . A . Taylor , M . Frank , W . Peterson , G . Lovejoy , D . Cox . J . Housworth , andP . J . Landrigan . Lea

dpoisonin g i

n childre n o

f lea dworkers ; hous e contaminatio n wit

hindustrial dust . Ne

w Englan dJ . Med . 296:260-261 , 1977 .

12-4 3P.5 3



## 13 . EVALUATIO N O F HUMA N HEALT H RISK S 1 

## FRO M EXPOSUR E T O LEA D AN D IT S COMPOUND S 13. 1 INTRODUCTIO N Th e precedin g chapter s o f thi s documen t

hav e de

scribe dlea dproduction , th e eonomic s o f lea d utilization , th e dispersio n o f lea di n th e environ

men t —particularl y in air , dust , an dsoi l —and , finally , hav e reviewe dth e effect s o f lea do n th e healt ho f man . Althoug hattemptin g t o relat e thes e variou s issue s t o on e another , thi s chapte r specificall y wil l attemp t t o asses s an dt o quantitat e th e healt heffect s tha t

aris e fro mexposur e o f ma n t o lea din th e environmen t and , mor e precisely , fro m exposur e t o lea din air . Si x centra l question s t o b e addresse dar e a s follows : 1 . Wha t ar e th e source s o f

lea din th e environ

ment ? (Section s 13. 2 an d13.3 ) 2 . Wha t ar e th e route s an dmechanism s b y whic hlea dfro mthes e source s enter s th e body ? (Section s 13. 2 an d13.3 ) 3 . Wha t par t d o averagin g time s fo r thes e ex posure s play ? (Sectio n 13.4 ) 4 . Ho w doe s th e bod y respon dt o th e entranc e o f lead ? (Sectio n 13.5 ) 5 . Ar e ther e group s withi n population s whic h ar e particularl y vulnerabl e t o lead ? (Sectio n 13.6 ) 6 . Wha t i s th e magnitud e of

th e ris k exposure s in term s o f

th e numbe r

o f person s expose din variou s subgroup s o f

populations ? (Sectio n 13.7 ) Eac ho f th e abov e question s i s addresse dseparatel y a s asubsectio n o f

thi s chapter , an dth e relevan t sec tio n i s note dbesid e eac hquestion . No w tha t

th e question s t o b e addresse din thi s treatmen t

o f ris k assessmen t

hav e bee n outlined , it

i s necessar y t o defin e th e term s whic hwil l b e employed . Thes e include : 1 . Dose i s th e amoun t

o r concentratio n o f

a chemica l tha t

i s presente dove r

tim e t o an organism , organ , cell , o r subcellula r

compo nent . Ideally , dos e shoul db e define da s th e amoun t o r concentratio n o f

th e chemica l a t

a specifi c intracellula r

sit e o f effect . 2 . External dose i s th e amoun t

o f th e contami

nan t in th e externa l environmen t (air , water , food , etc. ) t o whic hhuman s ar e exposed . 3 . Effective dose o r

internal dose i s th e amoun t o f th e contaminan t

absorbe db y th e body . 4 . Effect i s abiologi c chang e whic hresult s fro m exposur e t o achemical . 5 . Dose-effect

relationship i s aquantitativ e relationshi p betwee n th e dos e an dth e specifi c effec t

tha t i s establishe dafte r

grada

tion s in th e severit y o f a n effec t

hav e bee n measured . 6 . Critical

effect i s th e firs t

advers e functiona l change , reversibl e o r

irreversible , t o b e cause db y exposur e t o aparticula r chemical . 7 . Subcritical

effect i s achang e tha t

i s demonstrabl e b y biochemica l o r othe r test , bu t whic hdoe s no t

appea r t o impai r

func

tion ; som e suc hchange s ma y b e adaptiv e in nature . 8 . Critical

dose o r critical concentration i s th e leve l o f achemica l a t

whic hth e critica l effec t appears . 9 . Critical

organ i s th e orga n whic hmanifest s th e critica l effect ; i t

nee dno t

b e th e orga n withth e highes t

concentratio n o f

th e chemi

ca l no r tha t whic hultimatel y suffer s th e mos t seriou s injury . Dose-effec t

relationship s will var y amon g th e member s o f

apopulation . Respons e i s th e propor tio n o f th e populatio n tha t

manifest s aparticula r effec t at aparticula r

dos e level. 1 Thi s i s amor e restrictiv e definitio n o f respons e tha n tha t

use din bioassa y a s describe db y Finney. 2 Th e relationshi p betwee n dos e an dth e proportio n respondin g i s th e dose-respons e relation , whic hwil l mos t commonl y b e expresse db y asigmoid-shape dcurve . 13. 2 SOURCES , ROUTES , AN D MECHAN ISM S O F ENTR Y 13.2. 1 Source s O f th e estimate d161,22 5 metri c ton s o f lea demit

13- 1P.5 4



### te dint o th e atmospher e i n 1975 , th e combustio n o f gasolin e additive s an dwast e oi l accounte dfo

r 9 5 percen t of tota l inventorie demissions . Eac ho f th e remainin g emissio n source s account s fo r onl y a smal l part o f th e tota l quantity o

f lead , bu t ha s th e potentia l o

f creatin g localize dsituation s o f highair leadconcentrations , e.g. , primary lea dsmelters . Onc e leadi s introduce dinto th e air i t undergoe s a variety o f processe s includin g dr

y deposition , pre cipitation , an dresuspension . Thes e processe s resul t i n avariabl e proportio n o

f lea dbein g retaine di

n th e air an dthe n bein g distribute dover awide area . Othe r portion s ar e deposite don land , i n dust , an do

n water , resultin g i

n increase dleadconcentration s i n each . Othe r use s o f lea dresul t i n additiona l huma

n ex posure . Th e additio n o

f leadt o paint

make s lea

d directl y availabl e b

y ingestio n o

f paint chip s and paint-saturate dplaster . I n additio n i

t become s in

directl y availabl e throug hdus t contaminate dwit

h leadfreedb

y th e weatherin g proces s o f paint . Thi s primary sourc e i s currentl y under regulation , bu t

a vas t stock o f housin g painte dwit

hhigh-lead-conten t pain t stil l exists . Lead' s malleability an dductility hav e resulte di n th e us e o f thi s metal i

n pipe s fo r carryin g drinkin g water . When suchpipe s ar e usedi n area s wit

hsof t water o f low pH , apotentia l exist s fo r heavy lea

d contaminatio n o

f drinkin g water . It

i s difficult

t o estimat e th e overal l magnitud e of thi s danger , bu t ther e hav e been specifi c localize dexample s i n th e Unite dStates . A final quantitativel y significant sourc e o f leadi s th e huma n diet . Leadpresent

i n foodstuff

s i s th e su m o f th e amoun t

present i n th e ra w foodstoc k

an do f lea dintroduce dvi aprocessin g an dpackaging . Can

nedproduct s sucha s vegetable s an dmil k hav e been show n t o contai n higher

quantitie s o

f leadthan th e sam e product s package ddifferently . Thi s i s due , i n part , t o th e presenc e o

f leadsolde r

i n th e seam s o

f cans . Baby food s hav e als o been shown t o hav e high

er leadcontent s becaus e o f th e preservative s used . Th e origi n o

f leadi n ra w foo dstock s i s stil l amatte r o f som e controversy , althoug hpart o f i t i s likel y t o b e th e consequenc e o

f man' s activitie s whichresul t i n makin g leadavailabl e fo r uptake b

y animal s an d plants . Suc

hredistributio n an dsubsequent uptake o f leadb y plant s i s well illustrate db y fivefoldincrease s i n th e amount

o f lea dpresent i n tre e ring s over

a50

- yea r period . I t i s importan t

t o realiz e that

huma n exposure an d intak e ar e no t

limite dt o th e primary source s of lead i n th e environmen t

but , rather , t o th e su

mo f prim

ary , secondary , an dtertiary sources . Tabl e 13- 1 dis

play s thes e sources . TABLE 13-1 . SOURCE S O F LEAD FORHUMAN EXPOSURE S Primary exposur e sourc e Ai r

Pain t Wate rfro m leade d pipe s Foo d

a Reentrainmen t Secondar y exposur e sourc e Dus t an d soi l Wate r Dus t an d soi l Tertiar y exposur e sourc e Foo d Runof f wate r Air a Runof f wate r Air a



### 13.2. 2 Route s an

d Mechanisms of

Entr y Chapte r 1 0 present s dat aon th e entry of leadint o th e huma n body . Tw o route s o

f entr y are o f principal importance, inhalatio n andingestion . Intak e o f air

born e lea di s governe db

y th e physica

l an dchemical state o f inhale dlead , particl e siz e retentio n i n th e lung , andabsorptio n fro mth e lun g int o th e re d bloo dcells . Th e secon dmajo

r rout e o f entr y i s ingestion , bot

h o f foodando

f nonfoo dmaterial . Uptake i s con trolle db y th e nutrien t

balanc e o

f th e foodingested , particularl y that

o f iron , b y th e physica

l natur e o

f th e lead-bearin g materia l ingested , an db y th e chemical compositio n o

f th e substance . Here , too , th e leadi s absorbe db

y circulatin g re dbloo dcells . Th e tota l interna l dos e o

f leadwhichconfront s th e orga n system s o

f th e bod y i s th e su

mo f th e leadin

tak e b y bothroute s o

f entry : inhalatio n an dinges

tion . Thu s th e tota l interna l dos e represent s th e sum matio n o f al l external source s t o whichth e body i s exposed . Som

e o f thes e exposure s ma

y b e o f different relativ e significanc e i

n divers e populatio n group s du e t o variance s i n metabolis mo r

behavio r amon g different

segment s of

th e population . 13. 3 EVIDENC E O F INCREASE D BLOO D LEA D LEVEL S IN HUMAN S EXPOSE D T O ENVIRONMENTA L LEA D 13.3. 1 Relationship s Between Bloo d Lea d Level s an d Single-Source Exposure s Researc hha s been conducte don al l si x major ex posur e source s —air , dust , soil , water , paint , an d food . Chapte r

1 2 provide dth e detaile ddescription , evaluation , an dfinding s o f thos e studies . No t

al l source s hav e been studie dwit hth e same intensity , 13- 2P.5 5

an dfoo dha s bee n studie dleast . I n addition , foo da s atertiar y exposur e sourc e i s difficul t t o evaluate . Lea dconten t

i n foo ddu e t o packagin g an dprocess in g ha s bee n studie dmor e thoroughl y tha n contribu

tio n fro mtha t

lea dpresen t

at th e poin t

o f origin . Single-sourc e studie s o f ai r hav e include dbot h epidemiologica l an dclinica l investigations . Clinica l dat auniforml y demonstrat e th e actua l uptak e o f air

born e lea dint o blood , an depidemiologi c dat aals o generall y suppor t

suc harelationship . Studie s concerne dwithdus t an dsoi l lea dex posure s will b e considere dtogethe r sinc e in man y studie s th e investigator s di dno t attemp t t o dea l with thes e source s separately . Considerabl e evidenc e ex ist s tha t thes e exposure s ca n b e significan t determi

nant s o f bloo dlea dlevels . Furthermore , investiga

tion s o f childre n expose dt o lead-contaminate ddus t hav e demonstrate dmor e lea do n th e children' s hands , thu s documentin g aplausibl e rout e o f entr y whic hi s du e t o norma l ora l behavio r in youn g children . I t

ma y b e wort hreiteratin g her e tha t th e dos e o f lea dingeste dfro mdus t an dsoi l appear s t o b e additiv e t o tha t

inhale dfro mair . Th e popula r

assumptio n tha t

lead-base dpain t

i s th e singl e causativ e agen t o f elevate dbloo dlea d level s in childre n ha s resulte di n limitin g th e defini

tio n o f high-ris k

childre n t o thos e residin g in olde r housing . A s aresult , lea dscreenin g program s hav e bee n establishe dwithth e sol e purpos e o f identifyin g childre n withelevate dlea dlevel s amon g thos e liv

in g i n ol dhousing . Abatemen t effort s hav e fre

quentl y bee n unabl e t o fin dlea dpain t source s fo r childre n withhig hbloo dlevel s foun db y suc h screenin g programs . Th e possibl e contributor y rol e o f airborn e lea dt o th e lea dburde n o f urba n childre n ha s unti l recentl y receive dlittl e attention . Finally , studie s fro mGlasgo w an dBosto n hav e show n elevate dbloo dlea dlevel s i n conjunctio n wit helevate dlevel s o f

lea din th e drinkin g water . Secondar y effect s o f

occupationa l exposur e hav e bee n examine di n childre n whos e parent s wor k in lea dindustries . I t

ha s bee n foun dtha t

parent s carr y hom e lead-contaminate ddust . Significan t relation

ship s betwee n hous e dus t level s an dbloo dlea d level s hav e invariabl y bee n establishe din thes e studies . 13.3. 2 Multiple-Sourc e Exposure s Studie s measurin g th e quantit y o f lea di n multipl e sources , aroun dprimar y lea dsmelter s o r in urba n settings , hav e consistentl y demonstrate da n additiv e relationshi p betwee n bloo dlea dlevel s an dexposur e t o th e severa l source s studied . 13.3. 3 Effec to f Hos tFactor s o n Bloo d Lea d Level s Hos t characteristic s tha t

mediat e th e relationshi p betwee n exposur e t o lea dan dbloo dlea dleve l hav e bee n examine din severa l studies . I n particular , ag e ha s bee n show n t o b e asignifican t facto r in deter

minin g bloo dlea dlevels ; thi s relationshi p i s dis

cusse dbelo w in mor e detai l i n th e sectio n (13.6 ) o n population s at

greates t risk . Se x difference s hav e bee n foun dt o b e ag e related . Particularl y amon g preschoo l boy s an dgirls , vir

tuall y n o differenc e ha s bee n established . I n th e adul t population , however , male s generall y exhibi t highe r level s tha n females . Dat ao n th e racial/ethni c facto r ar e sparse . On e stud y ha s reported.tha t blac k childre n hav e highe r lea dlevel s tha n d o whit e children . Althoug hth e sig

nificanc e o f

th e racial/ethni c facto r canno t b e estab

lishe da t thi s time , i

t seem s reasonabl e t o assum e tha t it i s th e socioeconomi c rathe r tha n th e geneti c dimensio n o f

thi s variabl e tha t

ma y prov e t o b e rele

vant . Socioeconomi c variable s suc ha s incom e an d educatio n hav e no t

bee n examine dadequatel y a s in

dependen t

factors . Associate dcharacteristic s suc ha s residenc e in ol dhousing , o r proximit y t o high-den

sity traffi c arterie s o r

t o stationar y source s suc ha s smelters , hav e bee n show n t o b e directl y relevant . I n epidemiologica l studie s th e healt hstatu s a s a variabl e ha s no t

bee n examined . Condition s suc ha s iro n deficienc y anemia , othe r state s o f malnutrition , sickl e cel l anemia , an dlactos e intoleranc e a s hos t factor s i n lea dintak e an ddeterminant s o f physiologica l an dpathologica l change s hav e onl y recentl y com e unde r

study . N o finding s ar e availabl e a s yet . 13.3. 4 Summar y o f

th e Quantitativ e Relationshi p Statistica l evaluatio n o f th e dat acollecte dfro m populatio n an dclinica l studie s ha s bee n presente din th e previou s chapter . Ther e it wa s note dtha t

th e weigh t o f th e evidenc e indicate s tha t bloo dlea d level s follo w alognorma l distributio n i n expose d population s wit hageometri c standar ddeviatio n o f 1. 3 t o 1.5 . I t

wa s als o see n tha t

th e lognorma l distri

butio n ha s propertie s tha t mak e it amenabl e t o us e i n th e standard-settin g process , sinc e i t permit s a n esti

mat e o f th e proportio n o f

th e populatio n whos e bloo dlea dlevel s excee dan y specifie dlevel . Detaile dexaminatio n o f th e clinica l an d epidemiologica l studie s relatin g ai r lea dlevel s t o bloo dlea dlevel s i s presente di n Chapte r 12 . Evi

denc e indicate s tha t

apositiv e relationshi p exist s be

13- 3P.5 6

twee n bloo dan dai r

lea dlevels , althoug hth e exac t functiona l relationshi p ha s no t yet bee n clarified . Availabl e dat aindicat e tha t i n th e rang e o f

ai r lea d exposure s generall y encountere db y th e population , th e rati o o f

th e increas e in bloo dlea dpe r uni t o f ai r lea di s fro m1 t o 2 . I t appear s tha t

th e rati o for childre n i s i n th e uppe r en dof th e rang e an dtha t ratio s fo r

male s ma y b e highe r tha n thos e fo r females . Quantitativ e relationship s ca n als o b e establishe d betwee n bloo dlea dlevel s an dexposur e t o lea din soil . Ther e i s genera l agreemen t tha t bloo dlea d level s begi n t o increas e a t soi l lea dlevel s o f

fro m 50 0 t o 100 0 ppm . Mea n percen t increase s in bloo d lea dlevels , give n atwofol dincreas e i n soi l lea d levels , range dfro m3 t o 6 . Thi s i s aremarkabl e con sistency , give n th e divergenc e o f th e population s studied . 13. 4 AVERAGING-TIM E CONSIDERATION S On e o f th e majo r

area s o f concer n in dealin g with quantitatio n o f

th e relationshi p betwee n ahealt h effec t an da n externa l dos e o f som e environmenta l pollutan t i s th e determinatio n o f ho w lon g a n ex posur e mus t

occu r befor e ther e i s a n effect . Evidenc e presente din Chapte r 1 2 indicate s tha t

a 5 figldl increas e in bloo dlea dca n resul t fro ma n ai r lea dexposur e o f

3. 2 /ug/m 3 fo r

aperio do f

7 weeks . Furthermore , FE Plevel s hav e bee n show n t o in

creas e withi n 2 week s o f a n increas e o f

bloo dlea d levels . Therefore , an ai r lea dexposur e o f

3. 2 figlm 3 lastin g abou t

1 t o 2 month s ca n definitel y increas e th e bloo dlea dlevel . 13. 5 BIOLOGICA L AN D ADVERS E HEALT H EFFECT S O F LEA D I N MA N Lea ddoe s no t

presentl y hav e associate dwit hi t an y biologica l effec t

i n ma n whic hca n b e considere d beneficial ; therefore , an y consideratio n o f th e healt h effect s o f lea di n ma n mus t

b e don e fro mapoin t

o f vie w tha t acknowledge s th e absenc e o f an y healt h benefit/healt hcos t

ratio . A n additiona l an dextremel y importan t aspec t o f lead' s effec t

o n healt himpairmen t

tha t mus t b e con sidere di n ris k

assessmen t

i s th e questio n o f

whethe r thes e effect s ar e reversibl e onc e present . Physiologica l damag e t o centra l nervou s syste m tissu e i s presentl y widel y accepte da s bein g irreversi

ble ; thu s preventio n o f

lea dexposur e i s mos t

urgen t whe n on e consider s sever e neurologica l effects . Irreversibilit y i s als o accepte din th e cas e o f rena l tissu e damag e resultin g fro mchroni c lea dexposure , particularl y i n case s wher e thes e effect s ar e manifeste dmorphologically . W e spea k o f physiologica l irreversibilit y i n th e case s o f neurologica l o r

rena l tissues , bu t

th e con cep t o f irreversibilit y o f

a n effec t

bein g likel y o r assure db y nonbiologica l factor s suc ha s continuing , long-ter mexposur e t o airborn e lea dmus t als o b e considered . Hematologica l effect s ar e o f relevanc e here . Althoug hanumbe r o f thes e hematologica l effect s ma y b e biochemicall y reversible , i f th e prob

abilit y o f

th e perso n bein g remove dfro mth e ex posur e settin g inducin g thes e effect s i s sligh t o r non existent , fo r

whateve r

reason , the n defacto irrever

sibilit y exists . Thi s sectio n summarize s th e biologica l effect s o f lea do n ma n wit hparticula r referenc e t o significanc e o f thes e effect s fo r

huma n health . Muc ho f th e atten tio n in thi s sectio n will b e directe dt o thos e biologi

ca l effect s whic hma y collectivel y b e terme d "subclinical. " B y definition , subclinica l effect s ar e disruption s i n function , whic hma y b e demonstrate d b y specia l testin g bu t

no t b y th e classi c technique s o f physica l examination ; usin g th e ter m"subclinical " in n o wa y implie s tha t

thos e effect s ar e withou t con sequence s t o huma n health . 13.5. 1 Assessmen to f

Hematologica l Effect s o f Lea d A multiplicit y o f

effect s o f

lea do n th e hematopoieti c syste mexists . Thes e effect s wer e dis

cusse din detai l in Chapte r 11 , Sectio n 3 , an dar e briefl y summarize dhere . 13.5.1. 1 ANEMI A Anemi ai s aclassi c manifestatio n o f clinica l lea d intoxication , ofte n occurrin g prio r t o neurologica l an dothe r

syste mimpairment . Th e mechanis mo f anemi ai n lea dexposur e apparentl y involve s bot h decrease dproductio n o f hemoglobi n an denhance d destructio n o f

erythrocytes . Report s o n childre n in

dicat e tha t

statisticall y significan t decrease s i n hemoglobi n level s begi n t o appea r a t abloo dlea d leve l o f 4 0 figldl o r somewha t

below . I n adult s asig

nifican t decreas e i n hemoglobi n leve l appear s t o becom e eviden t

a t abloo dlea dleve l o f

5 0 figldl. 13.5.1. 2 LEA D EFFECT S O N HEM ESYN

THESI S A larg e numbe r

o f studie s hav e bee n don e o n th e effect s o f lea do n hem e synthesi s i n humans . Lea d interfere s wit hhem e synthesi s at severa l point s alon g th e heme-biosyntheti c pathway . Th e tw o mos t im

portan t point s o f

interferenc e are : (1 ) th e con densatio n o f

tw o unit s o f

8-aminolevulini c aci d dehydratas e t o formporphobilinoge n an d(2 ) th e in

13- 4sertio n o f iro n int o protoporphyri n I X whic hi s catalyze db y th e enzym e ferrochelatase . 13.5.1. 3 EFFEC T O FLEA D O N 8-AMINO

LEVULINAT EDEHYDRATAS E(8-ALAD ) AN D 8-AMINOLEVULINI C ACI D (8-ALA ) EX

CRETIO N A numbe r

o f studie s hav e show n th e hig hsen sitivit y o f 8-ALA D t o lea dan dth e negativ e correla

tio n betwee n bloo dlea dan dth e logarith mo f 8

- ALA D activity . Thes e studie s ar e describe din Sec

tio n 11.3 . I t

appear s tha t

thi s relationshi p hold s tru e fo r industria l workers , th e genera l population , an d children . Th e dose-respons e relationshi p betwee n bloo d lea dan dth e logarith mo f ALA D activit y appear s t o b e linea r

coefficien t

o f correlatio n (r ) = 0.84 . ALA D inhibitio n i s firs t note da t whol e bloo dlevel s o f 1 0 t o 2 0 figldl

(Chapte r

11) . Thi s hig hdegre e o f sensitivit y make s applicatio n an dinterpretatio n o f th e tes t difficult . ALA D inhibitio n i s virtuall y com plet e a t bloo dlea dlevel s o f

7 0 t o 9 0 figldl. Dat asummarize db y Hernberg 3 sugges t tha t hem e biosynthesi s i s no t

decrease db y ALA D inhibitio n unti l activit y o f

th e enzym e ha s falle n t o les s tha n 2 0 t o 3 0 percen t

o f normal . I n additio n t o it s effec t o n re dbloo dcel l ALAD , lea dappear s t o inhibi t ALA D activit y i n liver . I t ha s als o bee n suggeste d tha t in youn g childre n lea dmay inhibi t activit y o f ALA D in brain . 13.5.1. 4 EFFEC T O FLEA D O N IRO N INSER

TIO N INT O PROTOPORPHYRI N Accumulatio n o f

protoporphyri n in erythrocyte s in lea dexposur e i s th e resul t o f lead-induce dinhibi

tio n o f th e intramitochondria l enzyme , ferro

chelatase . Th e inhibitor y effec t o f lea do n fer

rochelatas e ma y eithe r

b e direc t

o r ma y b e mediate d b y adisruptio n in th e functio n o f mitochondria l membranes . Th e effec t

o f lea do n th e formatio n o f hem e i s no t limite dt o th e hematopoieti c system . Experimenta l anima l studie s hav e show n alea deffec t o n th e heme

requirin g protein , cytochrom e P-450 , a n integra l par t o f th e hepati c mixed-functio n oxidas e (Chapte r 11) , th e systemi c functio n o f whic hi s detoxificatio n o f exogenou s substances . Hem e synthesi s inhibitio n als o take s plac e i n neura l tissue . Th e elevatio n o f

fre e erythrocyt e protoporphyri n (FEP ) ha s bee n show n b y alarg e numbe r o f studie s t o b e exponentiall y correlate dwithbloo dlea dleve l in childre n an dadults . Presen t informatio n show s tha t a t relativel y fixe d bloo dlea dvalue s childre n an dprobabl y wome n

hav e highe r

protoporphyri n level s in thei r bloo d tha n adul t

males . Th e exac t

reaso n fo r

thi s i s no t known , bu t

it ma y b e o f

endocrinologica l origin . Elevatio n in protoporphyri n i s considere dno t onl y t o b e abiologica l indicato r o f impaire d mitochondria l functio n o f erythroi dtissu e bu t

als o a n indicato r

o f accumulatio n o f

substrat e fo r

th e enzym e ferrochelatase . I t therefor e ha s th e sam e pathophysiologica l meanin g a s increase durinar y 8

- AL A (vide supra). Fo r

thes e reason s accumulatio n o f protoporphyri n ha s bee n take n t o indicat e physiologica l impairmen t in humans , an dthi s clini

ca l concensu s i s expresse di n th e 197 5 Statemen t o f th e Cente r

for Diseas e Contro l (CDC) , USPHS . Th e criterio n use db y CD C t o indicat e a n effec t o f lea d o n hem e functio n i s an FE Pleve l o f 6 0 /xg/d l i n th e presenc e o f

abloo dlea dleve l abov e 3 0 figldl whol e blood . Mor e recen t

informatio n relatin g t o threshol do f lea deffect s indicate s tha t FE Plevel s begi n t o in

creas e at abloo dlea dvalu e o f 1 5 t o 2 0 fig Pb/d l bloo din childre n an dwome n and , at asomewha t highe r value , 2 0 t o 2 5 fig Pb/ d1 blood , in adul t men . 13.5.1. 5 OTHE REFFECT S O N HEM ESYN

THESI S Ther e ar e othe r

abnormalitie s o f

hem e synthesi s tha t ar e aresul t

o f lea dexposure . Fo r

example , it

i s wel l know n tha t

a n increase durinar y copro porphyri n leve l i s foun di n lea dpoisone dchildre n an dlea dworkers . I t

i s no t know n whethe r

thi s effec t result s fro mspecifi c enzym e inhibition , fro m upstrea maccumulatio n o f substrat e secondar y t o th e inhibitio n o f

iro n insertio n int o protoporphyrin , o r fro madisturbanc e o f coproporphyri n transpor t throug hth e mitochondria l membrane . A n increase dactivit y o f 8-AL A synthetas e i s see n in lea dintoxication , bu t thi s chang e probabl y arise s a s anegativ e feedbac k

contro l t o 8-AL A respons e t o inhibitio n upstrea min th e heme-biosyntheti c path

way . Fe w dat aexis t

t o quantitat e th e healt hsignifi

canc e o f thi s effect . 13.5.1. 6 EFFECT S O FLEA D O N GLOBI N SYN ^ THESE S Hemoglobi n synthesi s ma y als o b e impaire db y th e inhibitio n b y lea do f

globi n biosynthesis . Globi n i s th e protei n moiet y o f

hemoglobin . On e recen t stud y show s a n effec t

o n globi n synthesi s in vitro o n huma n reticulocyte s a t

lea dconcentration s correspondin g t o abloo dlea dleve l o f 2 0 figldl. 13- 5P.5 8



### 13.5. 2 Assessmen t

of Neurobehaviora l Effect s o f Lead A s reviewe di

n Chapte r 11 , a n extensiv e literatur e document s th e advers e effects o f leado n th e centra l an dperiphera l nervou s system s o f man y huma n and nonhuman mammalian species . Only limite ddose

respons e dat aexis t

that migh t allo w external lea

d exposure parameter s t o b e linke ddirectl y t o th e oc currenc e o

f particular

neurobehaviora l effects . I n contrast , more dat aexis t

relatin g bloo dleadlevel s t o neurobehaviora l deficits ; major emphasi s her e i s therefore focusedon th e concis e summarizatio n o f relationship s between huma n bloo dlea

dlevel s an d neurobehaviora l effects . 13.5.2. 1 CENTRA LNERVOU S SYSTE M EFFECT S Among th e mos t

profoundl y deleteriou s effects o f leadpoisonin g ar e thos e associate dwit hsevere CN S damag e tha t

occur a t toxi c hig hexposure levels . Th e acut e overt

manifestation s o

f neura l damag e at

high lea dexposure level s includ e suc hsymptom s a s ir

ritability , stupor , convulsions , and/o r coma , which characteriz e th e well-know n encephalopath y syn drome . Suchsymptom s a

t time s occur

abruptl y dur

in g th e cours e o

f muchmilder

symptomatolog y o r eve n i n apparentl y asymptomati c lea dpoisone din

dividual s an dma

y progres s t o deat

hwithin 4 8 hr . Even i n th e absenc e o

f deat hor prolonge duncon sciousness , i

t i s no w widely accepte dthat

irreversi

bl e neura l damag e typicall y occur s as on e o f th e se quela e o f nonfatal lea dencephalopath y episodes . Suc hpermanen t

neural damag e i s reflecte db y sign s o f continuin g CN S impairment rangin g fro

msubtl e neurobehaviora l deficit s t o severe menta l retarda

tio n o r continuin g mental incompetence . Wha t i s no t ye t universall y agree dupon , however , ar e th e lea d level s sufficien

t t o produc e leadencephalopath y an d it s sequelae . I n regardt o th e issue o

f threshol dlevel s fo

r lea d encephalopathy , bloo dleadlevel s o f 12 0 figldl o r more ar e currentl y widely accepte da s necessar y t o produc e encephalopath y symptom s i n adults . Th e publishe devidenc e bearin g on thi s point , however , i s ver y limited . Include damon g suc hevidenc e ar e a fe w scattere dreport s suggestin g tha t acut e en cephalopath y o r

deat hma y occur i n adult s a t bloo d lea dlevel s under

10 0 figldl (from8 0 t o 100 figldl), but th e rarity o

f suchcase s an dambiguitie s i n th e re porte ddat arende r

i t difficult t o accep t thos e report s as evidenc e fo

r encephalopath y i

n adult s a

t bloo d lea dlevel s belo w 120 figldl. Muchbette r

evidenc e exist s fo

r th e occurrenc e o

f lea dencephalopath y i

n childre n a

t bloo dleadlevel s belo w 120figldl

o r even 100/xg/dl . That

is , i t i s well documente dthat

suchsymptom s occur

fo r some childre n beginnin g at

th e 100 figldl

level ; also , several scattere dreport s sugges t that somewha

t lowe r threshol dlevel s ma

y obtain , i.e. , i

n th e 8 0 t o 10 0 figldl range , althoug hsuchreport s mus t b e viewedwit

hcautio n a s i

n th e cas e fo

r analogou s result s fo r adults . A s indicate dearlier , th e issue o f whether ap parentl y asymptomati c childre n experienc e subtl e neurobehaviora l deficit s a t low-to-moderat e bloo d lea dlevel s i n th e 4 0 t o 8 0 /xg/d

l rang e remain s asub

jec t o f muchcontroversy . A thorough , critica l revie w o f

th e relevan t

literatur e presente di n Chapte r 11 , nevertheless , lead s t o th e conclusio n that bloo dlea

dlevel s o

f 5 0 t o 6 0 figldl

ar e likel y sufficien t t o caus e significant

neurobehaviora l im

pairment s fo

r at leas t som e apparentl y asymptomati c children . Th e impairment s consis t mainly o f cogni

tiv e or sensory-moto r

integratio n deficits , bu t d o not appea r t o includ e th e occurrenc e o f hyper

activity ; tha t

latte r effec t seem s t o b e muc

hbette r es tablishe da s on e o

f th e neurological sequela e follow

ing encephalopath y at

higher leadlevels . 13.5.2. 2 PERIPHERA LNEUROPATH Y EFFECT S In additio n t o th e abov e CN S effects , periphera l nervou s syste

mdamag e als o result s fro mexposure s t o lead . Suc

heffects hav e been bes t

documente da s occurrin g afte

r long , chronic , high-leve l exposure s i n adult s exhibitin g othe r

symptom s o

f leadintoxica

tion . Recent

studie s o

f apparentl y asymptomati c adults , usuall y occupationall y expose dt o lead , however , presen t

reasonabl y stron g evidenc e forperiphera l neuropath y a

t more moderat e leadex posure levels , i.e. , at

bloo dleadlevel s i

n th e rang e o f 5 0 t o 7 0 figldl. Periphera l neuropath y effects ar e typicall y associate dwit

hadul t exposures , havin g been reporte dmuc

hles s frequentl y fo

r children . A fe w report s o

f lead-induce dperiphera l neuropathie s i n children , however , contai n evidenc e fo r th e oc currence , i

n som e rar e instances , a

t bloo dleadlevel s a s low a s 5 0 t o 6 0 figldl. 13.5.2. 3 RESULT S O FANIMA LSTUDIE S AS SUPPORTIV EEVIDENC E Review o f th e literatur e o

n th e neurobehaviora l effects o f lea di n animal s provide s evidenc e suppor tiv e o f th e abov e conclusion s fro mhuma n studies . That is , ther e appear s t o b e adifferential sensitivit y o f newbor n o r young animal s o

f man y specie s t o th e neurobehaviora l effects o

f lead . Thi s applie s bot

ht o 13- 6P.5 9

th e inductio n o f

lea dencephalopath y a t hig hex posur e level s an dmor e subtl e neurobehaviora l deficit s a t

lower , mor e moderat e exposur e levels . I n regar dt o specifi c type s o f subtl e neurobehaviora l effects , hyperactivit y appear s t o occu r mainl y a t bloo dlea dlevel s i

n exces s o f

7 0 t o 8 0 figldl

and , therefore , probabl y mos t closel y parallel s th e pos t encephalopathi c hyperactivit y wel l demonstrate da s on e o f th e sequela e o f

lea dencephalopath y in humans . Othe r

behaviora l changes , interprete da s indicativ e o f

cognitiv e impairment s resultin g fro m CN S effects , appea r

t o occu r

in animal s a t

bloo d lea dlevel s belo w thos e associate dwit hacut e en cephalopathi c effects , i.e. , in th e 3 0 t o 8 0 /xg/d l bloo dlea dleve l range . Thi s parallel s rathe r closel y th e effect s observe dfo r

humans , especiall y children , excep t tha t cognitiv e deficit s hav e no t bee n ver y wel l documente din th e childre n at level s belo w 5 0 t o 6 0 figldl. Th e externa l lea dexposure s yieldin g th e abov e result s fo r

animals , however , typicall y appea r t o b e muc hhighe r

tha n thos e producin g comparabl e effect s i n humans ; th e comparabilit y o f anima l studie s an dhuma n studie s i s therefor e ofte n ques tioned . If

on e focuse s o n th e resultin g bloo dlea d level s achieved , regardles s o f associate dexterna l dose , however , th e result s o f th e anima l studie s paralle l thos e o f

th e huma n studie s remarkabl y well . I n discussin g th e neurobehaviora l effect s o f lead , abov e in th e presen t

sectio n an di

n Chapte r

11 , adis

tinctio n ha s repeatedl y bee n mad e betwee n thresh

ol dlevel s yieldin g sever e symptom s o f lea d encephalopath y see n at hig hexposur e level s an d mor e subtl e neurobehaviora l deficit s observe dat lowe r exposur e levels . Thi s approac hma y inappro

priatel y conve y a n impressio n o f suc heffect s occur rin g in adiscrete , step-lik e fashio n a s particula r threshol dbloo dlea dlevel s ar e reached . I t i s impor

tan t t o not e tha t

thi s ma y occu r

insofar a s shiftin g fro mapparen t

no-effec t

level s t o level s a t

whic h fairl y wel l substantiate dneurobehaviora l effect s hav e bee n foun dt o occur , i.e. , aroun d5 0 t o 6 0 figldl; beyon dtha t

point , however , furthe r increase s in relativ e level s o f

neura l damage , a s indicate db y increasingl y sever e neurologica l o r behaviora l deficits , occu r

i n amor e o r

les s smoothl y ascendin g fashio n in relatio n t o increasin g bloo dlea dlevels . Thes e relationship s ar e presente dlate r i n a n approximat e manne r

i n Tabl e 13-2 . Du e t o difference s i n individua l susceptibility , it shoul db e emphasize dtha t

th e uppe r

en do f th e rang e o f

bloo d lea dlevel s a t

whic hsubtl e neurobehaviora l effect s hav e bee n reporte dt o occu r fo r som e individual s merge s o r

overlap s substantiall y wit hth e lowe r en d o f

th e rang e a t

whic hmuc hmor e sever e en cephalopathi c symptom s hav e bee n observed , an d tha t th e shif t fro msubtl e t o sever e neura l symptom s may b e quit e abrupt . 13.5. 3 Effect s o f

Lea d o n Reproductio n an d Developmen t Althoug hth e effect s o f lea dexposur e in human s hav e usuall y bee n associate dwit hth e hematopoietic , neural , an drena l systems , concer n need s t o b e equall y directe dt o th e entir e are ao f reproductio n an ddevelopment , wit hspecia l emphasi s o n th e vulnerabilit y o f

pregnan t

wome n or , mor e ac curately , th e vulnerabilit y o f th e fetus . Attentio n in thi s are ai s focuse do n tw o aspect s o f reproduction : (1 ) th e gametotoxi c effect s o f lead , i.e. , lea deffect s o n spermatogenesi s an dovaria n function , an d(2 ) postconceptio n event s throug h delivery . 13.5.3. 1 HUMA N GAMETOTOXICIT Y Som e dat ainvolvin g effect s o f lea dexposur e o n th e fertilit y o f

male s exist , an dthes e hav e bee n ob

serve da t bloo dlea dlevel s o f

5 0 t o 8 0 /xg/d l unde r condition s o f

occupationa l exposure . Wit hregar dt o women , on e stud y o n lea deffect s (se e Reproductio n an dDevelopmen t

section , Chapte r

11 ) raise s th e possibilit y tha t

th e ovaria n cycl e ma y b e disturbe din th e ag e rang e o f

2 0 t o 2 5 year s withai r lea dlevel s aroun d7 /xg/m 3

. 13.5.3. 2 POSTCONCEPTIO N LEA D EFFECT S Bot hearl y literatur e an dmor e curren t studie s conclusivel y sho w tha t lea dcrosse s th e placenta l barrier . Suc hfeta l exposur e therefor e commence s a t abou t th e en do f

th e firs t trimeste r

(1 2 weeks ) an d continue s throughou t

feta l development . A s ha s alread y bee n pointe dout , th e distributio n o f lea d withi n th e fetu s a t

differen t stage s o f

developmen t

i s probabl y mor e importan t tha n th e tota l amoun t

pre sen t a t birth . Tissu e analysi s als o demonstrate s that , i n Ameri

can s fro mnewborn s throug hperson s age d1 9 years , brai n lea dlevel s appea r t o b e mos t

elevate da t

birt h an dthe n diminis hwit hdevelopment . A numbe r

o f studie s sho w passag e o f lea dthroug h th e placenta l barrie r

b y comparin g cor dbloo dlea d an dmaterna l bloo dlea dlevels . Thes e studie s furthe r serv e t o she dsom e ligh t o n th e effec t

o f variou s factor s i n infan t bloo dlea dvalues . I n agrou p o f

cor dblood/materna l bloo dmatch

ings , infan t

bloo dlevel s wer e highl y correlate dwit h thos e o f thei r mothers . A secon dstud y showe dtha t 13- 7P.6 0



### bloo dvalue s fo

r infant s whos e mother s wer e urban resident s were significantly higher than thos e o

f rura l infants . A study don e i

n alead-bel t

are ao f th e Unite d State s raise s th e possibilit y that leadma y affect th e cours e o f normal delivery o

f childre n sinc e ther e wer e more incident s o

f pretermdeliver

y an dpre mature membran e ruptur e i n pregnan t

wome n i n thi s regio n compare dt o agrou p fro marelativel y unex pose darea . 13.5. 4 OtherHealt

h Effects 13.5.4. 1 RENA LEFFECT S Nephropath y i s aconditio n usuall y considere di n it s chroni c for

mandthat

ca n bes t b e relate dt o prolonge dexposure t o leadwit hacorrespondin g bloo dlea dleve l o f abou t 7 0 figldl. Becaus e chroni c leadnephropath y result s only afte r prolonge do r repeate dexposures , i

t i s impossibl e t o recapitulat e accuratel y th e exposure history ; therefore , deter

minatio n o

f a n exposure threshol dfo

r thi s conditio n i s impossible . 13.5.4. 2 EFFECT S O FLEA D O N TH EEN

DOCRINOLOGICAL , HEPATIC , CAR

DIOVASCULAR , AN D IMMUNOLOGICA L SYSTEM S Althoug hsom e studie s hav e bee n don e i n referenc e t o eac ho

f th e system s i

n thi s subsection , ther e exist s to o littl e quantitativ e informatio n relat

in g bloo dleadlevel s t o th e endocrinological , hepatic , an dcardiovascular systems . 13.5. 5 Does-Effect/Respons e Relationship s I n an y discussio n o

f th e ris k assessment

directe d towardaparticular

agent , suc

ha s lead , tw o ques tion s arise : 1 . Wha t ar e th e lowes t

level s o f th e interna l dos e (bloo dleadlevel ) that giv e ris e t o an

y biological effect ? 2 . Wha t dose-respons e relationship s ar e ob

taine dtha t

defin e aproportio n o

f apopu latio n manifestin g agiven biological effec t a t aparticular

interna l dose ? Informatio n summarize di n th e precedin g sectio n deal t wit hrelationship s between bloo dlea dlevel s an dvariou s biological effects o f lead . Many o

f th e dat adiscusse dabov e concerne dthreshol dlevel s a t whichhealt

heffects o

f leadar e firs t

observe di

n different populatio n groups . Tabl e 13- 2 summarize s th e threshol dlevel s a

t whichvariou s specifi c hematological an dneurobehaviora l effects hav e been observe dfo

r particular

subpopulations . A number

o f investigator s hav e attempte dt o quantitat e mor e precisel y lead' s dose-respons e relationship , i.e. , th e proportio n o f apopulatio n ex hibitin g healtheffects a

t agiven bloo dleadlevel . TABL E 13-2 . SUMMAR YO F LOWES TOBSERVE D EFFEC TLEVEL S Lowes t observe d effec t leve l Populatio n grou p 1 0 15-2 0 25-3 0 4 0 4 0 4 0 5 0 50-6 0 50-6 0 80-10 0 100-12 0 ALA D inhibitio n Erythrocyt e protoporphyri n elevatio n Erythrocyt e protoporphyri n elevatio n Increase d urinar yAL Aexcretio n Anemi a Coproporphyri n elevatio n Anemi a Cognitiv e (CNS ) deficit s Periphera l neuropathie s Encephalopath ysymptom s Encephalopath ysymptom s Childre n an d adult s Wome n an d childre n Adul t male s Childre n an d adult s Childre n Adult s an d childre n Adult s Childre n Adult s an d childre n Childre n Adult s 

### Du e t o th e limite davailability o f data , mos t

suchat tempt s hav e been restricte dt o effects on th e hematologi c system , i

n particular

th e elevatio n o

f FEP , th e inhibitio n o

f ALA D activity , an dth e ex cretio n o f ALA i n th e urine . I n regardt o definin g dose-respons e relationship s fo r hematological effects , thre e different assessment s o f suchrelationship s hav e been carrie dout 4 6 

### an d published . Fo r example , in th e approac hof Zielhuis, 4 

### dose-respons e relationship s wer e develope dfo

r ALAD , ALA-U , an dFE Pa s obtain

e dfo r adults , mal e andfemale , an dchildren . I n Figure 13- 1 ar e presente dth e dose-respons e dat afo r childre n an dadult s fo

r ALA D a t inhibitio n level s o

f 4 0 an d7 0 percent . In Figure 13-2 , acorrespondin g relationshi p fo

r urinary ALA i s given for adul t males , an dFigure 13- 3 present s th e correspondin g 13- 8P.6 1

dat afo r FE Pin adul t

males , adul t

females , an d children .

z O S « 8 0 I - Q < U J

_ l H = 2 S S 6 0 "> •A u . . O I ; 4 0 — _

— 1 

### 1

x J 

### / / / / / / / / / / / / y 

### l - V 

### / / 1 —(^40 %

70 % / / / / / / / / / 1 1 

# " P

1 * - 1 >40 % >70 %

ADULT S CHILDRE N 1 —

.

_

- I f < O I 2 0

0 1 0 3 0 5 0 7 0 BLOO D LEA D LEVEL , u g Pb/d l Figur e 13-1 . Dose-respons e curv e fo r percen t ALA D inhibi tio n fo r adult s an d childre n a s a functio n o f bloo d lea d level .

° - < 6 0 O w u u A > 5 mg/lite r

mg/lite r

3 0 5 0 BLOO D LEA D LEVEL , u g Pb/d l Figur e 13-2 . Dose-respons e curv e fo r ALA i n urin e (ALA-U ) a s a functio n o

f bloo d lea d level. 4 A s ca n b e see n fro mFigur e 13-1 , ther e appear s t o b e amarke ddifferenc e a t 4 0 percen t

inhibitio n o f ALA D activit y betwee n childre n an dadults , suc ha differenc e decreasin g a s on e goe s t o 7 0 percen t in

hibition . Fo r

example , a t

2 0 /xg/d l bloo dlead , ap proximatel y 1 0 percen t o f adult s sho w 4 0 percen t enzym e inhibition , wherea s th e correspondin g valu e fo r childre n i s somewha t

abov e 8 0 percent . I t

shoul d als o b e note dtha t

ther e i s apparentl y astee p ris e in th e linea r

portio n o f

thes e sigmoi drelationships , e.g. , 2 0 percen t

o f adult s sho w a4 0 percen t inhibi

tio n i n ALA D a t

2 0 figldl bloo dlead , wherea s vir

tuall y al l o f

th e adul t

populatio n show s 4 0 percen t inhibitio n a t

4 0 figldl. A simila r

steepnes s in th e curv e i s see n i n regar dt o children . Figur e 13- 2 present s dose-respons e dat afo r AL A i n urin e exceedin g tw o discret e levels , > 5 an d>1 0 mg/liter , wit hincreasin g bloo dlead . I t ma y b e see n tha t th e respons e in th e linea r portio n o f

th e curv e i s muc hles s stee p tha n fo r ALAD . Fo r

example , fo r approximatel y 5 percen t o f adults , th e no-respons e leve l fo r AL A > 5 mg/lite r

i s abou t 3 0 figldl bloo d lead . A t 6 0 figldl bloo dlead , th e correspondin g per centag e o f

th e populatio n showin g thi s respons e i s in exces s o f 8 0 percent . Th e correspondin g plo t fo r AL A > 1 0 mg/lite r

show s ales s stee p slop e tha n th e forme r case . A t

6 0 figldl

bloo dlead , th e corres pondin g percentag e o f

th e adul t

populatio n i s ap proximatel y 40 . Th e composit e dose-respons e plo t presente din Figur e 13- 3 show s a n increase drespons e i n FE Pi n adul t female s compare dt o adul t males . Childre n sho w agreate r

respons e tha n adul t

male s onl y u p t o bloo dlea dlevel s o f

abou t 4 5 /ug/dl . Th e dat ao f Zielhui s ar e extracte dfro manumbe r o f reports . I n Figur e 13-4 , interestingly , wherei n ar e containe dth e

o A < » 10 0

8 0

6 0

4 0

2 0 -

- 1 1 1 1

ADUL TFEMALE S /* "

1 /l*""' l 1 1 1 1

/ADUL TMALE S

1 / CHILDRE N

1 1 1 -

-

-

-

-

3 0 5 0 BLOO D LEA D LEVEL , u g Pb/d l Figur e 13-3 . Dose-respons e curv e fo r FE P a s a functio n o f bloo d lea d level. 4

Q U J K < (/ > A

ADUL TMALE S

2 0 3 0 BLOO D LEA D LEVEL , u g Pb/d l Figur e 13-4 . Dose-respons e curv e fo r FE P a s a functio n o f bloo d lea d level. 5 13- 9.P.62 _

dose-respons e dat ao f

Roel s e t al. 5 fo r FE Pi n adul t males , adul t

females , an dchildren , it appear s tha t childre n sho w th e mos t heightene dresponse , followe db y adul t

females , an dth e leas t

respons e in adul t males . Th e slop e fo r

th e linea r

portio n o f

th e respons e curv e i s quit e stee p i n th e cas e o f children ; 2 0 percen t

o f th e childre n sho w elevate drespons e (8 2 /xg/d l rbc ) a t

2 0 /ug/d l bloo dlead , wherea s vir

tuall y al l th e childre n excee dthi s valu e a t 3 5 /ug/d l bloo dlead . Th e dose-respons e dat ao f Piomelli 6 ar e presente d i n Figur e 13- 5 an dconsis t o f composit e plot s fo r mea n plu s 1 standar ddeviatio n (3 3 figldl whol e blood ) an dth e mea n plu s 2 standar ddeviation s (5 1 fig FEP/d l whol e blood) . I n th e dat apresente di n Figur e 13-5 . bloo dlea dlevel s in exces s o f 2 8 figldl whol e bloo dwer e no t

use di n tn e calculations . I t ap pear s fro mth e abov e tha t ther e exist s athreshol da t abou t 1 5 figldl

whol e blood .

> 9 8 — Q 9 5 — 9 8 9 5 9 0 75 5 0 2 5

5 2 1 1 NOT E

1 1 1 1 1 1 1 1 POINT S OUTSID E TH E RANG E O F TH E SOLI D LINE S WER E NO TUSE D IN CALCULATION S

0 r > - s * — FE P > MEA N + 1 S.D . (3 3 ug/dl ) ' 

# j* y Jg rf

FEP>MEA N + 2 S.D .

_tm JT

j f

(5 1 ug/di ) 

# ? y* S QV J C (NATURA L FREQUENCY) — 

### o ° /f^ ^ 1 " 1 I I I I 1 ? 2 5 - 

### ° ,„ _

### = < 5 -

0 1 0 2 0 3 0 4 0

BLOO D LEA D LEVEL , ug Pb/d l Figur e 13-5 . Dose-respons e curv e fo rFE P a s a functio n o f bloo d lea d level. 6 EP A ha s carrie dou t

analyse s o f

th e dat afro mth e Aza r e t al . study 7 an dcalculate dadose-respons e curv e fo r urinar y AL A (Figur e 13-6) . Thes e dose

respons e curve s wer e plotte dfo r tw o differen t

cut of f points . Thes e point s wer e th e mea n value s fo r bloo dlea dlevel s les s tha n 1 3 figl 100 g , plu s 1 stan dar ddeviatio n an dplu s 2 standar ddeviations , respectively . Fro mth e mea n plu s 2 standar ddevia

tion s curve , i t

i s readil y apparen t

tha t th e linea r

por tio n o f th e curv e i s quit e steep . A t abloo dlea dleve l o f 2 0 figldl, onl y 6 percen t o f th e populatio n excee d th e mea n plu s 2 standar ddeviation s valu e o f th e contro l population , wherea s a t abloo dlea dleve l o f 50 , 5 0 percen t

o f th e populatio n exceed s tha t value . Furthermore , whe n on e examine s th e figur e a t 4 0 figldl, th e valu e at whic hAL A in urin e i s take n t o sugges t healt himpairment , th e Aza r e t al . dat asho w tha t abou t 3 0 percen t

o f th e populatio n show s a n elevatio n i n thi s parameter .

4 8 0

< <s o s Z 5 0 o

MEAN + 1 S.D . MEA N + 2 S.D . MEA N ALA- U » 0.3 2 FO R BLOO D

LEA D < 1 3 ug/d l J I I I I I BLOO D LEA D LEVEL , u g Pb/d l Figur e 13-6 . EPA calculate d dose-respons e curv e fo r ALA- U (fro m Azare t al. 7 ) . I n Tabl e l 3- 3 ar e tabulate dproportion s o f th e stud y population s in th e Zielhui s an dAza r report s showin g elevate durinar y AL A versu s bloo dlea d level . Th e dat afo r

Zielhui s ar e a s cite di n Figur e 13-2 , th e percentag e o f

subject s wit hALA- U greate r tha n 5 mg/lite r

bein g used . Th e Aza r

dat ain Tabl e 13- 3 refe r t o th e mea n plu s tw o standar ddeviation s dat aset . Fo r

purpose s o f

compariso n o f

dose

respons e dat afo r

FEP , th e studie s o f

Zielhuis, 4 Roels, 5 an dPiomelli 6 ar e tabulate din Tabl e 13-4 . A s in th e cas e fo r

th e tabl e o f

ALA- U data , it

shoul d b e kep t in min dtha t

difference s exis t

in cut-of

f point s fo r

FE Prespons e t o lea din th e variou s studies . TABL E 13-3 . ESTIMATE D PERCENTAG E O F SUBJECT S WIT H ALA- U EXCEEDIN G S mg/lite rFO R VARIOU S BLOO D LEA D LEVEL S Bloo d lea d levels . ijg'd l 1 0 2 0 3 0 4 0 5 0 6 0 7 0 4 Zielhuis . % 0 0 6 2 4 4 8 7 6 9 6 Aza re t at. .

% 2 6 1 6 3 1 5 0 6 9 8 4 13-1 0TABL E 13-4 . ESTIMATE D PERCENTAG E O F CHILDRE N WIT H E P EXCEEDIN G CUT-OF F POINT S FO R VARIOU S

BLOO D LEA D LEVEL S Bloo d lea d level , ug/d l 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 Zielhuis a %

0 6 22 37 49 — —

—' Roel s e t al,. b % 3 2 7 7 3 10 0 — — — — Piomelli. c %

9 1 1 4 8 8 0 — — — —

a E P > E P o

f childre n wit h Pb- B < 2 0 iig/dl . b E P >8 2 ugd l cells . C E P >EPo l 33ug'dl . 13. 6 POPULATION S A T RIS K Populatio n a t

ris k i s asegmen t

o f adefine d populatio n exhibitin g characteristic s associate dwith significantl y highe r

probabilit y o f

developin g acon dition , illness , o r

othe r abnorma l status . Thi s hig h ris k ma y resul t

fro meithe r

greate r inheren t suscep tibilit y o r

fro mexposur e situation s peculia r t o tha t group . Wha t

i s mean t b y inheren t

susceptibilit y i s a hos t characteristi c o r

statu s tha t

predispose s th e hos t t o agreate r

ris k o f heightene drespons e t o an exter na l stimulu s o r

agent . I n regar dt o lead , tw o suc hpopulation s ar e definable . The y ar e preschoo l ag e children , especiall y thos e livin g in urba n settings , an dpreg nan t women , th e latte r

grou p owin g mainl y t o th e ris k t o th e conceptus . Childre n ar e suc hapopulatio n fo r bot ho f

th e reason s above , wherea s pregnan t wome n ar e a t

ris k primaril y du e t o th e inheren t susceptibilit y o f

th e conceptus . 13.6. 1 Childre n a s aPopulatio n a tRis k Childre n ar e developin g an dgrowin g organism s exhibitin g certai n difference s fro madult s i n term s o f basi c physiologi c mechanisms , capabilit y o f copin g withphysiologi c stress , an dthei r relativ e metabol

is mo f lead . Also , th e behavio r o f childre n fre

quentl y place s the min differen t relationshi p t o source s o f

lea di n th e environment , thereb y enhanc

in g th e opportunit y fo r the mt o absor b lead . Furthermore , th e occurrenc e o f excessiv e exposur e ofte n i s no t

realize dunti l seriou s har mi s done . Youn g childre n d o no t

readil y communicat e amedi

ca l histor y o f

lea dexposure , th e earl y sign s o f suc h bein g commo n t o s o man y othe r diseas e state s tha t lea di s frequentl y no t

recognize dearl y a s apossibl e etiologica l facto r

contributin g t o th e manifestatio n o f othe r symptoms . 13.6.1. 1 INHEREN T SUSCEPTIBILIT Y O F TH EYOUN G Discussio n o f

th e physiologica l vulnerabilit y o f th e youn g mus t

addres s tw o discret e areas . No t onl y shoul dth e basi c physiologica l difference s b e con sidere dtha t

on e woul dexpec t

t o predispos e childre n t o aheightene dvulnerabilit y t o lead , bu t als o th e ac tua l clinica l evidenc e mus t b e considere dtha t

show s suc hvulnerabilt y doe s indee dexist . I n Chapte r

10 , Sectio n 10. 6 wa s devote dt o th e metaboli c consideration s in identifyin g susceptibl e subgroups . Factor s discusse din tha t sectio n in

cluded : (1 ) greate r

lea dintak e o f

infant s o n ape r uni t bod y weigh t

basis , whic hi s probabl y relate dt o greate r calori c an dwate r

requirement ; (2 ) greate r intak e a s wel l a s net . absorptio n (se e G I section) , greate r ne t respirator y intak e a s wel l a s greate r ne t absorptio n an dretentio n fro mth e G I tract ; (3 ) rapi d growt hrat e ma y reduc e th e margi n o f safety agains t avariet y o f

stresse s includin g iron , calcium , an d vitami n deficiency ; (4 ) dietar y habit s o f childre n ar e quit e differen t

fro madults ; norma l hand-to-mout h activit y probabl y result s in th e transfe r o f lead-con

taminate ddus t

an ddir t

vi athum b suckin g o r in retrieva l o f

dirt-contaminate dfoodstuffs ; (5 ) th e metaboli c requirement s fo r protein , calcium , an d iro n ar e s o grea t

relativ e t o intak e tha t anegativ e balanc e in thes e factor s ma y exist ; (6 ) in ver y youn g childre n metaboli c pathway s an dfactor s suc ha s th e blood-brai n barrie r

ar e know n t o b e incompletel y developed ; an d(7 ) partitionin g o f lea di n th e bone s o f childre n i s differen t

fro mtha t

o f adults . Onl y 6 0 t o 6 5 percen t

o f th e lea dbod y burde n i s i n th e bone s o f children , an dthi s fractio n ma y b e mor e labile . Hematologi c an dneurologi c effect s i n childre n hav e bee n show n t o hav e lowe r threshold s pe r

uni t o f bloo dlea dtha n in adults . I n particular , th e lowes t observe deffec t

level s fo r

FE Pan danemi aar e lowe r fo r childre n tha n adults . Wit hreferenc e t o neurologi c effects , th e onse t o f encephalopath y an d othe r injur y t o th e nervou s syste mappear s t o var y bot hregardin g likel y lowe r threshold s i n childre n fo r som e effect s an din . th e typica l patter n o f neurologi c effect s presented , e.g. , in encephalopath y o r othe r CN S deficit s bein g mor e commo n in childre n versu s periphera l neuropath y bein g mor e ofte n see n in adults . No t onl y ar e th e effect s mor e acut e in childre n tha n in adults , bu t als o th e neurologi c sequela e ar e usuall y muc hmor e sever e i n children . Upo n carefu l examinatio n o f th e data , it

shoul db e note dtha t

certai n geographi c o r

socioeconomi c fac

13-1 1P.6 4

tor s appea r

t o emerg e a s importan t factor s deter

minin g th e differentia l susceptibilit y o f som e group s o f childre n fo r

lead-induce dneurologi c damage . Tha t is , ther e seem s t o b e distinc t variatio n i n effect s o r alac k thereo f a s reporte dfo r

childre n i n differen t studie s dependin g upo n th e geographi c area s fro m whic hth e stud y population s wer e drawn . Fo r exam ple , th e few credibl e report s o f lea dencephalopath y i n childre n a t

bloo dlea dlevel s les s tha n 10 0 ug/d l al l concer n childre n fro minner-cit y areas . Similarly , statisticall y significan t effect s o r

border

lin e effect s indicativ e o f mor e subtl e neurobe

haviora l deficit s i n lead-expose dchildre n a t moderatel y elevate dbloo dlea dlevel s hav e bee n re porte dfo r

group s o f

childre n draw n fro minner-cit y population s o f

urba n centers . I n contrast , onl y afew statisticall y significan t

neurobehaviora l effect s hav e yet bee n reporte dfo r

population s of

childre n ex periencin g simila r

elevation s in bloo dlea dlevels , bu t residin g nea r

primar y smelte r

facilitie s i n semi

rura l areas . On e canno t

determin e withan y certaint y th e specifi c factor s tha t

migh t contribut e t o th e apparen t differentia l sensitivit y o f inner-cit y childre n t o th e neurobehaviora l effect s o f lead . Severa l possibilities , however , migh t b e reasonabl y con sidered , includin g th e following : 1 . Parameter s o f

lea dexposur e probabl y differe dsubstantiall y fo r th e population s unde r study ; th e smelte r

are achildren , fo r example , may hav e experience dmuc hmor e gradua l accumulation s o f lea ddurin g th e cours e o f

long-term , low-leve l exposure s versu s probabl e repeate dbrie f episode s o f somewha t

highe r leve l exposure s bein g superimpose do n an y long-term , low-leve l exposure s fo r

th e inner-cit y children . 2 . Th e exposure s o f

th e smelte r

childre n likel y include dsignificantl y highe r level s o f

othe r metalli c species , e.g. , zinc , tha t ar e know n t o reduc e th e pathologica l impac t o f lea do n man y orga n systems . 3 . Difference s in nutritiona l statu s likel y ex iste dbetwee n th e smelte r an dinner-cit y children , wit hth e latte r probabl y havin g a highe r incidenc e o f

iron , calcium , an d vitami n deficiency ; o r

othe r difference s in dietar y conten t

an dhabit s migh t

b e invoke d a s a n explanation . 4 . Interaction s betwee n lea dexposure s an d othe r factor s associate dwit hth e stresse s o f urba n versu s nonurba n livin g ma y als o con tribut e t o th e apparen t differentia l suscep tibilit y o f

inner-cit y chilren . 13.6.1. 2 EXPOSUR ECONSIDERATION S Children' s dietar y habit s a s wel l a s th e diet s them

selve s diffe r

markedl y fro madult s and , a s aresult , plac e childre n i n adifferen t relationshi p t o severa l source s o f

lead . Th e dominanc e o f canne dmil k

an d processe dbab y foo di n th e die t o f man y youn g childre n i s an importan t facto r i s assessin g thei r

ex posur e t o lea dsinc e bot hthos e foodstuffs hav e bee n show n t o contai n highe r amount s o f

lea dtha n com ponent s o f

th e adul t

diet . Th e importanc e o f thes e lea dsource s i s no t

thei r relationshi p t o airborn e lea d directl y but , rather , thei r rol e in providin g ahighe r baselin e lea dburde n t o whic hth e airborn e contribu

tio n i s adde d Childre n ordinaril y underg o astag e o f develop

men t in whic hthe y exhibi t

mouthin g behavior , fo r example , thumbsucking . A t thi s tim e the y ar e a t

ris k o f pickin g u p lead-contaminate dsoi l an ddus t o n thei r hand s an dhenc e int o thei r mouth s wher e i t

ca n b e absorbed . Scientifi c evidenc e documentin g a t leas t th e firs t par t o f th e chai n i s available . Ther e is , however , a n abnorma l extensio n o f th e mouthin g behavior , calle dpica , whic hoccur s i n som e children . Althoug hdiagnosi s o f thi s i s difficult , childre n wh o exhibi t thi s trai t

hav e bee n show n t o purposefull y ea t nonfoo ditems . Muc ho f th e lead-base dpain t

proble mi s know n t o occu r becaus e childre n actuall y inges t chip s o f

leade d paint . 13.6. 2 Pregnan tWome n an d th e Conceptu s a s a Populatio n a tRis k Ther e ar e som e rathe r

inconclusiv e dat aindicat

in g tha t wome n ma y in genera l b e at somewha t

high

e r ris k t o lea dtha n men . However , pregnan t wome n an dthei r concept i a s asubgrou p ar e demonstrabl y a t highe r risk . I t shoul db e pointe dou t that , i n fact , it reall y i s no t

th e pregnan t

woma n per

se wh o i s a t greates t ris k but , rather , th e unbor n chil dsh e i s carrying . Becaus e o f

obstetri c complications , how

ever , th e mothe r

hersel f ca n als o b e a t

somewha t greate r risk . Thi s sectio n will firs t describ e th e genera l evidenc e fo r

al l wome n an dthe n th e evi

denc e tha t

pertain s t o pregnan t

wome n exclusively . Studie s hav e demonstrate dtha t women , lik e children , in genera l ten dt o sho w aheightene d respons e o f

erythrocyt e protoporphyri n level s upo n exposur e t o lead . Th e exac t reaso n fo r

thi s heightene drespons e i s no t know n bu t

ma y relat e t o endocrin e difference s betwee n me n an dwomen . I n 13-1 2P.6 5

particular , th e level s o f testosteron e ma y pla y arol e i n thi s response . A s state dabove , th e primar y reaso n pregnan t wome n ar e ahigh-ris k

grou p i s becaus e o f

th e fetu s eac hi s carrying . I n addition , ther e i s som e sugges tiv e evidenc e tha t

lea dexposure s ma y affec t mater na l complication s o f

delivery . Wit hreferenc e t o materna l complication s at delivery , informatio n i n th e literatur e suggest s th e incidenc e o f

preter mdeliver y an dprematur e mem bran e ruptur e relate s t o materna l bloo dlea dlevel . Furthe r stud y o f

thi s relationshi p a s wel l a s studie s relatin g t o discret e healt heffect s in th e newbor n ar e required . Vulnerabilit y o f

th e developin g fetu s t o lea dex posur e arisin g fro mtransplacenta l transfe r o f mother' s bloo dlea dconten t wa s discusse din Sectio n 11.6 . Thi s proces s start s a t th e en do f

th e firs t tri

mester . Cor dbloo dstudie s involvin g mother-infan t pair s repeatedl y hav e show n acorrelatio n betwee n materna l an dfeta l bloo dlea dlevels . Furthermore , th e observe dpositiv e correlatio n o f urinar y AL A level s withbloo dlea dlevel s in newborn s indicate s tha t som e heme-biosyntheti c derangemen t i s ap paren t a t birt han dmus t

therefor e hav e commence d in utero. Furthe r suggestiv e evidence , cite di n Chapte r 11 , ha s bee n advance dfo r prenata l lea dexposure s o f fetuse s possibl y leadin g t o late r highe r instance s o f postnata l menta l retardatio n amon g th e affecte doff

spring . Th e availabl e dat aar e insufficien t t o stat e withan y certaint y tha t

suc heffect s occu r

o r t o deter

min e wit han y precisio n wha t level s o f lea dexposur e migh t b e require dprio r

t o o r durin g pregnanc y in orde r t o produc e suc heffects . 1 3 7 DESCRIPTIO N O F U.S . POPULATIO N I N RELATIO N T O PROBABL E LEA D EX POSURE S I n thi s sectio n estimate s ar e provide do f th e num be r o f individual s potentiall y a t ris k t o lea dex posures . Unfortunatel y th e lates t censu s dat aar e onl y fro m1970, 8 althoug hsom e estimate s ar e avail

abl e fro mth e Nationa l Cente r fo r Healt hStatistic s for 1975. 9 Thi s i s unfortunat e sinc e som e significan t change s ar e though t

t o hav e occurre din th e popula

tio n structur e sinc e th e 197 0 census . Becaus e mos t

lea dexposures , exceptin g area s with primar y lea dsmelters , occu r in wha t th e Burea u o f th e Censu s call s urba n areas , a n estimat e o f th e po tentia l ris k

o f airborn e lea dexposur e ca n b e mad e fro mth e tota l urba n populatio n o f th e Unite dStates . Tha t thi s ma y b e an acceptabl e firs t approximatio n ca n b e gleane db y comparin g th e frequenc y distri

butio n o f ai r lea dconcentration s fo r urba n an drura l Nationa l Ai r

Samplin g Networ k

station s i

n Chapte r 7 . Thi s compariso n readil y show s adistinc t differenc e in exposur e betwee n th e tw o type s o f sta tions . Base do n examinatio n o f th e urba n station s a s wel l a s o f

literatur e dat ao n bot hai r lea dan dsoi l an ddus t lea dvalues , astron g cas e ca n b e mad e t o suppor t th e assumptio n tha t

th e are awhic hth e Burea u o f

th e Censu s call s th e centra l cit y o f th e ur ba n area s i s at

eve n highe r

ris k o f lea dexposure . Therefore , in regar dt o exposure s othe r tha n localize dpoin t

stationar y source s o f lead , th e populatio n at

ris k i s th e urba n on e and , in particular , th e centra l cit y residents . Fo r th e Unite dState s i n 1970 , thes e value s wer e 14 9 an d6 4 millio n people , respectively 8 (Tabl e 13-5) . Fro mth e tabl e it ca n TABL E 13-5 . POPULATIO N AN D PERCEN TDISTRIBUTION , URBA N AN D RURAL , BYRAC E 197 0 CENSUS 4

in n (10° ) Urba n Insid e urbanize d area s Centra l citie s Urba n fringe s Outsid e urbanize d area s Rura l Total . Unite d State s 128.773(72.4 ) 100.952(56.8 ) 49.54 7 (27.9 ) 51.405(28.9 ) 27.822(15.7 ) 48.97 6 (27.6 ) 177.77 3 20,55 2 (80.7 ) 17,49 5 (68.7 ) 14,37 5 (56.5 ) 3,12 0 (12.3 ) 3,05 7 (12.0 ) 4,91 1 (19.3 ) 25.46 3 149.325(73.5 ) 118.447(58.3 ) 63.922(31.5 ) 54.52 5 (26.8 ) 30.878(15.2 ) 53.88 7 (26.5 ) 203,21 2 readil y b e see n tha t

ahighe r proportio n o f

th e non whit e populatio n live s in urba n area s tha n white s (80. 7 versu s 72. 4 percent ) an di s possibl y subjec t t o greate r exposur e t o airborn e lead . Furthermore , thi s disparit y i s eve n greate r whe n on e consider s th e centra l cit y populatio n only , whic hma y b e subjec t t o eve n highe r

level s o f lea dpollutio n fro mamultitud e o f sources . Fro mth e previou s discussio n o f population s a t risk , however , tw o subgroup s o f thi s tota l populatio n wer e define da s bein g a t eve n highe r

ris k — children , especiall y thos e unde r 5 , an dpregnan t 13-1 3TABL E 13-6 . NUMBE R O F BIRTH S B YRAC E AN D SIZ E O F POPULATION 8 P.6 6

Urba n area s o f give n siz e fro m 197 0 censu s Birth s Whit e 772.23 0 286.70 6 600.16 6 1.432.162 3.091.26 4 Blac k 321.41 2 37.02 4 65.79 0 148.13 6 572.36 2 Birth s Other s 24.39 4 4.18 2 10.39 4 28.79 0 67.76 0 Tota l

1.118.03 6 327.91 2 676.35 0 1,609.08 8 3.731,38 6 > 100,00 0 50-99,99 9 10-49,99 9 59,99 9 Tota l

Urba n area s o f give n Siz e fro m 1975 censu s Whit e Blac k Other s Tota l > 100,00 0 50-99,99 9 10-49,99 9 59,99 9 571.47 8 222.73 5 478.38 2 1.279.40 1 276.38 7 37.88 5 64.48 1 132.82 8 26.33 2 5.92 1 13.03 9 35.32 9 874,19 7

266.54 1 555.90 2 1,447.55 8 Tota l 2.551.99 6 511.58 1 80.62 1 3.144,19 8 women . Ther e i s insufficien t evidenc e at

thi s tim e t o determin e whethe r

an y racia l o r

ethni c grou p suffer s an innat e susceptibilit y t o lead . I n th e Unite dState s in 197 0 abou t 1 2 millio n childre n unde r

5 year s o f

ag e live din urba n areas . Approximatel y 5 millio n o f thes e childre n live din centra l cit y areas. 8 Sinc e between-censu s populatio n estimate s ar e no t

availabl e fo r

urban-rura l com parisons , th e onl y way t o us e th e 197 5 populatio n estimate s i s t o assum e tha t th e percen t

distributio n obtaine din 197 0 stil l hold s true . If in fac t tha t i s th e case , th e mor e recen t

estimate s woul db e abou t 1 1 millio n children , in urbanize darea s an d4. 6 millio n in th e centra l city . A n estimat e mad e b y th e Nationa l Burea u o f

Standard s o f

th e tota l chil dpopulatio n withbloo dlea dvalue s equa l t o o r greate r tha n 4 0 figldl i n arecen t

yea r wa s 600,000. 1 0 Thi s tota l i s clearl y acaus e fo r

concer n i n vie w o f

th e healt hdat a presente din Sectio n 13. 4 above . O f course , th e us e o f thi s figure , base do n th e man y lead-screenin g pro gram s conducte din thi s country , i s no t mean t t o im

pl y tha t al l o f thes e value s resulte dfro mairborn e lead . The y probabl y d o not , sinc e pain t lea dex posure s ar e a n additiona l importan t source . But , o n th e othe r hand , th e additio n o f a n airborn e com ponen t o f lea dexposur e o n to p o f thes e level s woul d adversel y affec t

th e publi c health . If

airborn e lea d wer e th e onl y contributio n t o thes e children' s lea d values , th e potentia l healt heffect s ascribabl e t o tha t exposur e coul db e significant . Th e difficult y in estimatin g th e numbe r o f preg nan t wome n expose dt o ai r

lea di s eve n greater ; thi s i s becaus e th e numbe r of. pregnan t

wome n i s no t tabulate do n a n urban-rura l basis . Therefore , fo r thi s document , th e numbe r o f pregnan t

wome n will b e estimate dfro mth e numbe r o f liv e birth s (Tabl e 13-6). 8 Unfortunatel y thes e dat aals o ar e no t tabu

late do n a n urban-rura l basi s but , rather , o n a populatio n siz e o f

plac e o f residence . I t

ca n readil y b e see n tha t

th e tota l numbe r

o f birth s ha s decline d in th e tim e 197 0 t o 1975 . I f on e assume s onl y th e highes t populatio n siz e categor y t o b e a t ris k o f lea d exposure , ther e ar e stil l almos t 900,00 0 newborn s a t ris k o f lea dabsorptio n fro mthei r mothers . 13. 8 REFERENCE S FO RCHAPTE R1 3 1 . Nordman , C . H . Environmenta l lea dexposur e i n Finland . A stud y o n selecte dpopulatio n groups . Dissertation . Universit y o f

Helsinki , Helsinki . 1975 . 2 . Finney , D . J . Statistiea l metho di n biologica l assay . Charle s Griffi n an dCo. , London . 1971 . p . 5 . 3 . Hernberg , S . Biochemical . Subclinica l an dClinica l Response s t o Lea dan dThei r Relatio n t o Differen t

Ex

posur e Levels , a s Indicate db y th e Concentratio n o f Lea d i n Blood . In: Effect s an dDose-Respons e Relationship s o f Toxi c Metals . G . F . Nordber g (ed.) . Elsevie r Scientifi c Publishin g Co. . Amsterdam . 1976 . Par t BIS . 4 . Zielhuis , R . L . Dose-respons e relationship s fo r inorgani c lead : I . Biochemica l an dhematologica l responses . Int . Arch . Occup . Hlth . 55:1-18 . 1975 . 5 . Roels , H. , Buchet , J . P. , R . Lawrie , an dG . Hubermont . Impac t o f ai r pollutio n b y lea do n th e hem e biosyntheti c pathwa y in school-ag e children . Arch . Environ . Hlth . J/: 3 10-316 , 1976 . 6 . Piomelli . S . Reanalysi s o f dat afro mS . Piomelli . C . Sea

man , D . Zullow . A . Curran , an dB . Danidow . Metaboli c evidenc e o f

lea dtoxicit y i n "normal " urba n children . Clin . Res . 25.-495A . 1977 . Presente dt o Environmenta l Protectio n Agenc y staf f an dconsultants . Researc h Triangl e Park . N.C . Septembe r 28 , 1977 . 13-1 47 . Azar , A. . R . D . Snee . an dK . Habibi . A n epidemiologica l 9 . U . S . Nationa l Cente r for Healt hStatistics , Vita l Statistic s approac ht o communit y ai r lea dexposur e usin g persona l o f th e U . S. . 1975 , Dat afo r 197 5 Births . Unpublishe d- ai r samplers . Environ . Qual . Saf.Suppl . 11:254-290 . 1975 . provide db y NCHS . 8 . U . S . Burea u o f

th e Census , Statistica l Abstract s o f th e 10 . Nationa l Burea u o f Standards . Surve y Manua l fo r Unite dStates . 197 6 (97t hEd.) . Washington , D.C . 1976 . p . Estimatin g th e Incidenc e o f Lea dPain t

i n Housing . NB S 18 , Tabl e 19 . ' Technica l Not e 921 , Septembe r 1976 .

13-1 5

# APPENDIX A GLOSSARY * Absorptio n (o f

lead) : Transfe r

o f lea dint o a n organ is mvi aintestina l wall , alveola r surface , o r

skin . Accumulatio n (o f

lead) : Ne t

positiv e differenc e be

twee n intak e an doutpu t o f lea dove r

a n extende d period . Acety l coenzym e A (CoA) : Coenzyme , derive dprin

cipall y fro mth e metabolis mo f glucos e an dfatty acids , tha t

take s par t

i n man y biologica l acetyla

tio n reactions ; oxidize din th e Kreb s cycle . Acetylcholine : Compoun drelease dfro mcertai n autonomi c nerv e endings ; act s i n th e transmissio n o f nerv e impulse s t o excitabl e membranes . Acetylcholinesterase : Enzym e i n excitabl e membrane s tha t

inactivate s acetylcholine . /3-Acety l glucosaminadase : Enzym e tha t hydrolyze s th e termina l glucosaminidi c bond s o f odd-num

bere doligosaccharide s t o yiel dN-acetyl

glucosamin e an dth e nex t lowe r even-numbere d oligosaccharide . Acid-fast : Describe s acel l o r bacteriu mtha t

retain s ady e tha t

ha s anegativel y charge dmolecule . Aci dphosphatase : Enzym e tha t hydrolyzes , in a n aci dmedium , monophosphori c esters , wit h liberatio n o f

inorgani c phosphate . Adenocarcinoma : Carcinom aderive dfro mglandu

la r tissu e o r i n whic hth e tumo r

cell s formrecog nizabl e glandula r

structures . Adenoma : Benig n epithelia l tumo r i n whic hth e cell s for mrecognizabl e glandula r structure s o r

in whic hth e cell s ar e clearl y derive dfro mglandula r epithelium . Adenosin e diphosphat e (ADP) : Coenzym e com pose do f

adenosin e an dtw o molecule s o f phosphori c acid ; importan t i n intermediat e cellu

la r metabolism ; aproduc t o f th e hydrolysi s o f adenosin e triphosphat e (ATP) . Adenosin e triphosphat e (ATP) : Nucleotid e occur rin g i n al l cells , wher e i t serve s i n th e storag e o f energ y an di n th e transfe r o f energ y in metaboli c processes ; compose do f adenosin e an dthre e molecule s o f

phosphori c acid . "Compile d from standar d referenc e work s and , t o alesse rextent , from informatio n furnishe d by expert s in th e respectiv e disciplines . Adenosin e triphosphatas e (ATPase) : Enzym e tha t mediate s th e remova l o f wate r fro mATP : AT P+ H 2 0 —AD P+ orthophosphate . Adeny l cyclase : Enzym e tha t catalyze s th e forma

tio n o f cycli c adenosine-3' , 5'-monophosphat e (cycli c AMP) . Adenyli c acid : (1 ) Generi c nam e fo r agrou p o f isomeri c nucleotides ; (2 ) Phosphori c aci deste r o f adenosine ; als o know n a s adenosin e monophosphat e (AMP) . Adrenaline : Se e Epinephrine . Adrenergic : Describe s th e chemica l activit y o f epinephrin e o r

epinephrine-lik e substances . Adrenergi c synapse : Synaps e a t whic h norepinephrin e i s liberate dwhe n anerv e impuls e passes . Advection : Proces s o f

transpor t

o f a n atmospheri c property , o r

substanc e withi n th e atmosphere , solel y b y th e mas s motio n o f th e atmosphere . Aerodynami c diameter : Expressio n o f aerodynami c behavio r o f a n irregularl y shape dparticl e i n term s o f th e diamete r

o f a n idealize dparticle ; tha t is , aerodynami c diamete r i s th e diamete r

o f a spher e o f

uni t densit y tha t

ha s aerodynami c behavio r identica l t o tha t

o f th e particl e in ques tion . Thus , particle s havin g th e sam e aero dynami c diamete r

ma y hav e differen t

dimension s an dshapes . Aerodynami c drag : Aerodynami c resistance ; retard

in g forc e tha t

act s upo n abod y movin g throug ha gaseou s flui dan dtha t

i s paralle l wit hth e direc

tio n o f motio n o f

th e body . Aerodynami c particl e size : Spher e o f uni t densit y tha t ha s aerodynami c behavio r identica l t o tha t

o f th e particl e i n question . Aerosol : Syste min whic hth e dispersio n mediu mi s a ga s an dth e disperse dphase—compose do f soli d particle s o r

liqui ddroplets—doe s no t settl e ou t unde r th e influenc e o f

gravity . Aeroso l particles : Soli dparticle s 10 l 2 t o 10 ' fim i n diameter , disperse di n agas .P.6 9

Agglomeration : Proces s b y whic hprecipitatio n par ticle s gro w b y collisio n wit ha n assimilatio n o f clou dparticle s o r

othe r precipitatio n particles . Aitke n dus t

counter : Instrumen t

fo r determinin g dus t conten t o f th e atmosphere ; asampl e o f ai r i s mixed , i n a n expandabl e chamber , wit halarg e volum e o f

dust-fre e ai r

containin g wate r

vapor . Upo n sudde n expansion , th e chambe r cool s adiabaticall y belo w it s dewpoint , an ddroplet s for mwit hth e dus t

particle s a s nucle i an dar e counte db y mean s o f

agri dunde r

amicroscope . Aitke n nuclei : Microscopi c particle s i n th e at mospher e tha t

serv e a s condensatio n nucle i fo r drople t growt hdurin g th e rapi dadiabati c expan sio n produce db y an Aitke n dus t counte r (se e above) . Aldolase : Enzym e tha t

act s o n aketose-1-phosphat e t o yiel ddihydroxy-aceton e phosphat e plu s a n aldehyde ; e.g. , fructose-1 , 6-diphosphat e = dihydroxyaceton e phosphat e + D

- glyceraldehyde-3-phosphate . Alkalin e phosphatase : Enzym e tha t hydrolyzes , i n alkalin e medium , monophosphori c esters , wit h liberatio n o f

inorgani c phosphate ; foun di n plasm aan dserum , bone , etc . Alkalinity : Exces s o f

hydroxy l ion s ove r

hydroge n ions , generall y expresse da s milliequivalent s pe r liter . Alveola r

macrophages : Rounde dgranula r phagocyti c cells , withi n th e alveol i o f th e lungs , tha t inges t inhale dmaterial . Ambien t air : Th e surrounding , well-mixe dair . Aminoacy l synthetase : Enzym e tha t catalyze s th e couple dreaction s o f

amin o aci dactivatio n i n whic ha n amin o aci di s first attache dt o adenosin e monophosphat e an dthe n t o atransfer-RN A molecule . e-Amin o grou p o f

lysine : Th e amin o group , NH 2 , at tache dt o e , o r

5th , carbo n ato mfro mth e carbox

y l carbo n i n th e amin o acid , lysine : H 2 N-CH 2 - C H 2 -C H 2 -C H 2 -C H (N H 2 )-COOH . 8-Aminolevulini c aci d(ALA , o r 8-ALA) : COOH

CH 2 -CH 2 -CO-CH 2 -NH 2 ; intermediat e in th e bio

synthesi s o f

heme-containin g compounds ; forme d fro msuccinyl-coenzym e A an dglycine . 8-Aminolevulini c aci ddehydratas e (ALAD) : Enzym e i n hem e biosyntheti c pathwa y tha t medi

ate s formatio n o f

porphobilinoge n fro m8

- aminolevulini c acid . 8-Aminolevulini c aci dsynthetas e (ALAS) : Enzym e i n hem e biosyntheti c pathwa y tha t mediate s th e formatio n o f

8-aminolevulini c aci dfro msuc cinyl-Co A vi a2-amino-3-ketoadipate . Amphetamine : a-Methylphenethylamine . Dru g use dt o stimulat e th e centra l nervou s system , in

creas e bloo dpressure , reduc e appetite , an d reduc e nasa l congestion . Abus e ma y lea dt o de

pendence , characterize db y stron g psychi c depen

denc e associate dwitha n increas e i n RE M (rapid

eye-movement ) sleep , hunger , apathy , an d depression . Anamnesti c response : Rapidl y increase dantibod y leve l followin g renewe dcontac t wit haspecifi c antigen , eve n afte r

severa l years . Anodi c strippin g voltammetry : A n electrochemica l metho do f

analysis . Anophthalmia : Developmenta l defec t characterize d b y complet e absenc e o f

th e eye s o r

b y th e presenc e o f vestigia l eyes . Anorexia : Los s o f

appetite . Anoxia : Relativ e lac k

o f oxygen ; cause db y inade

quat e perfusio n o f

tissue s b y bloo dcarryin g nor ma l amount s o f

oxyge n o r

b y norma l perfusio n o f bloo dcarryin g reduce damount s o f oxygen . Antipyrin e (C,,H 12 ON 2 ) : Compoun duse da s a n an tipyretic , analgesic , an dantirheumati c drug . Are asource : Consist s o f anumbe r

o f poin t source s arrange di n atwo-dimensiona l array . Astrocyti c proliferatio n (astrocytosis) : Proliferatio n o f astrocyte s owin g t o th e destructio n o f nearb y neuron s durin g ahypoxi c o r hypoglycemi c episode . Ataxia : Failur e o f

muscula r

coordination . Atmospheri c turbulence : Motio n o f th e ai r (o r othe r fluids ) i n whic hloca l velocitie s an dpressure s fluctuat e irregularl y in arando mmanner . Avoidanc e task : Behaviora l testin g procedur e use d t o measur e a n animal' s avoidanc e an descap e per formance . I n aone-wa y tas k onl y on e respons e i s appropriate , wherea s in atwo-wa y tas k eithe r o f tw o response s i s appropriate , dependin g o n th e existin g tes t

conditions . Axona l degeneration : Degeneratio n o f axons , th e processe s o r

nerv e fiber s tha t

carr y th e unidirec

tiona l nerv e impuls e awa y fro mth e nerv e cel l body . Balanc e experiments : Experiment s o n ma n o r othe r animal s tha t

involv e quantitativ e measurement s o f intak e (vi arespiratio n an dingestion ) an dlos s (vi aexhalatio n an dexcretion ) o f aspecifi c ele

men t o r substance . A positiv e balanc e mean s tha t mor e i s take n i n tha n i s los t ove r aspecifi c time . Basophili c stippling : Spotte dappearanc e o f relativel y immatur e re dbloo dcell s tha t contai n cytoplasmi c materia l tha t stain s deepl y wit hbasi c dyes . A- 2P.7 0

Biosphere : Th e par t

o f th e earth' s crust , waters , an d atmospher e wher e livin g organism s ca n subsist . Blood-brai n barrier : Th e barrie r create db y semi

permeabl e cel l wall s an dmembrane s t o passag e o f som e molecule s fro mth e bloo dt o th e cell s o f th e centra l nervou s system . Bod y burden : Th e tota l amoun t o f aspecifi c sub

stanc e (fo r

example , lead ) in a n organism , includ

in g th e amoun t

stored , th e amoun t

tha t i s mobile , an dth e amoun t

absorbed . Bon denergy : Th e enthalp y chang e tha t accompanie s th e breakin g o f

achemica l bon dbetwee n tw o atoms . Th e tota l bon denerg y o f amolecul e give s ameasur e o f

it s thermodynami c stability . Boundar y layer : Laye r o f flui din th e immediat e vicinit y o f

aboundin g surface ; refer s ambiguousl y t o th e (1 ) laminar , (2 ) turbulent , (3 ) planetary , o r (4 ) surfac e boundar y layers . Brainstem : Stemlik e portio n o f th e brai n connectin g th e cerebra l hemisphere s wit hth e spina l cord : Bremsstrahlung : Radiatio n tha t i s emitte db y a n electro n accelerate din it s collisio n wit hth e nucleu s o f

a n atom . Brownia n movement : Rando mmovement s o f dis

perse dsmal l particle s suspende di n afluid ; result s fro mrando mcollision s betwee n th e molecule s o f

th e dispersin g mediu man dth e parti

cle s o f th e disperse dphase . CaEDTA : Edathami l calciu mdisodium , whic hi s th e calciu mdisodiu msal t o f ethylene

- diaminetetraacetate , achelatin g agent . CaEDT A i s use di n th e study , diagnosis , an dtreatmen t o f poisonin g b y variou s heav y metals , includin g lead . CaEDT A mobilizatio n test : Tes t i n whic haknow n quantit y o f

CaEDT A i s injecte dparenterall y an d th e amoun t

o f lea dexcrete di n urin e durin g a know n perio dbeginnin g immediatel y thereafte r i s measured . Thi s procedur e i s use dbot hclinicall y an dexperimentall y an di s though t t o provid e a n inde x o f th e mobil e fractio n o f th e tota l bod y burde n o f

lead . Carcinogenesis : Developmen t o f carcinoma ; or , in mor e recen t

usage , producin g an y kin do f malig

nancy . Carcinoma : Malignan t ne w growt hmad e u p o f epithelia l cell s tendin g t o infiltrat e th e surround

in g tissue s an dgiv e ris e t o metastases . Cascad e impactors : Low-spee dimpactio n devic e fo r us e i n samplin g bot hsoli dan dliqui datmospheri c suspensoids ; consist s o f fou r pair s o f jet s (eac ho f progressivel y smalle r size ) an dsamplin g plate s workin g in serie s an ddesigne ds o tha t eac hplat e collect s particle s o f

on e siz e range . Catalase : Enzym e tha t

catalyze s th e decompositio n o f hydroge n peroxide ; contain s fou r hemati n group s pe r

molecule ; foun di n live r an dre dbloo d cells . Catecholamines : Grou p o f sympathomimeti c amine s containin g acatecho l moiety ; especiall y epinephrine , norepinephrine , an ddopamine . Catenation : Propert y o f a n elemen t

tha t enable s it

t o lin k t o itsel f t o formchains , e.g. , carbon . Cerebellum : Larg e dorsall y projectin g par t o f th e brai n havin g th e specia l functio n o f muscl e coor dinatio n an dmaintenanc e o f equilibrium . Cerebra l anoxia : Relativ e lac k o f oxyge n in th e brain . Cerebra l cortex : Thi n laye r o f gra y matte r

o n th e surfac e o f

th e cerebra l hemisphere , folde dint o gyri , wit habou t

two-third s o f

it s are aburie din th e depth s o f

th e fissures . Chelate : Chemica l compoun di n whic hametalli c io n i s sequestere dan dboun dint o arin g b y covalen t bond s t o tw o o r

mor e nonmetalli c atom s in th e sam e molecule . Chelant : Chemica l compoun dtha t will reac t

wit h metal s t o for mchelates ; achelatin g agent . Cholinergic : Stimulated , activated , o r transmitte d b y acetylcholine ; applie dt o thos e nerv e fiber s tha t liberat e acetylcholin e a t asynaps e whe n a nerv e impuls e passes . Cholinesterase : Enzym e tha t catalyze s th e hy

drolysi s o f

acylcholin e t o cholin e an da n anion . Chemica l energy : Energ y produce do r absorbe din th e proces s o f

achemica l reaction . Chi-squar e test : Tes t

o f statistica l significanc e base d o n frequenc y o f

occurrence ; use dt o tes t pro babilitie s o r

probabilit y distribution s (goodnes s o f fit), statistica l dependenc e o r independenc e (association) , an dcommo n populatio n (homogeneity) . Chlorinity : Measur e o f chlorid e content , b y mas s (g/kg) , o f water ; sometime s determine dt o permi t calculatio n o f

salinity . Choroi dplexus : An y o f th e highl y vascular , folde d processe s tha t

projec t int o th e third , fourth , an d latera l ventricle s o f

th e brain . Chromatid : On e o f

th e pai r

o f stands , forme db y longitudina l splittin g o f achromosome , tha t

ar e joine db y asingl e centromer e i n somati c cell s durin g mitosis ; on e o f

atetra do f

strand s forme d b y lengthwis e splittin g o f paire dchromosome s durin g th e diploten e stag e o f meiosis . A- 3P.7 1



### Chromophore : An

y chemical grou p whos e presenc e give s adecide dcolo r

t o acompoun dan dthat unite dwit hcertai n othe r

group s t o for

mdyes . Chromosomes : Threadlik e structure s i n animal o r plan t nuclei, see

n durin g karyokinesi s (nuclear divisio n characteristi c of

mitosis) , tha t

carry th e linearl y arrange dgeneti c material . Chroni c nephritis : Chroni c inflammatio n o f th e kid

neys . Coagulation : Proces s tha t convert s numerou s droplet s into asmalle r

number o f large r pre cipitatio n particles . Coalescence : Mergin g o

f tw o liqui ddrop s int o a singl e larger

drop . Colic : Paroxysmal pai n i n th e abdomen , cause db y spasm , distention , o r

obstructio n o

f an y on e o f th e hollo w viscera . Colloida l materials : Se

e Colloida l system . Colloida l system : A

n intimat e mixtur e o

f tw o sub

stances , on e o

f which , calle dth e disperse dphas e (o r colloid) , i s uniforml y distribute di n afinel y divide dstat e throug hth e secon dsubstanc e (dis

persio n medium) ; th e dispersio n mediumma y b e agas , liquid , o r

solid . Combustio n nucleus : Condensatio n nucleu s forme d a s aresul t

o f industria l o r

natura l combustio n processes . Complement : Comple x protein s i n normal serum that interac t t o combin e wit

hantigen-antibod y complex , producin g lysi s whe n th e antige n i s i

n a n intac t cell ; importan t

i n hos t defens e mechanis m agains t invadin g microorganisms . Complex : Chemical compoun di n whichapart

o f th e molecular bondin g i s o

f th e coordinat e type . Complexing : Formatio n o f acomple x compound ; see Complex . Condensation : Physica

l proces s b

y whichavapo r become s aliqui do r

solid ; opposit e o

f evapora tion . In meteorology , th e ter mi s limite dt o transformatio n o

f vapo r t o aliquid . Condensatio n nucleus : Particle , eithe r liqui do r solid , upo n whichcondensatio n o f water vapo r begin s i n th e atmosphere . Condensatio n particles : Se e Aitke n nuclei . Confidenc e interval : A rang e o f value s (a , < a<a 2 

### ) determine dfromasampl e b y definite rule s s o chosen that , i

n repeate drando msample s fro mth e hypothesize dpopulation , a n arbitaril y fixedpro portio n (1-e ) o

f that rang e will includ e th e tru e value , x , o

f a n estimate dparameter . Th e limits , a , an da 2 

### , ar e calle dconfidenc e limits ; th e relativ e frequenc y (1-e ) wit hwhichthes e limit s includ e a i s calle dth e confidenc e coeffi

cient ; an dth e complementary probability , e , i s calle dth e confidenc e level . A s wit hsignificanc e levels , confidenc e level s ar e commonl y chosen a s .0 5 o r .01 , th e correspondin g confidenc e coeffi

cient s bein g .95 , .99 . Confidenc e interval s shoul dno t b e interprete da s implyin g tha t

th e paramete r

itsel f ha s arang e of values ; it ha s only on e value , a. O n th e othe r hand , th e confidenc e limit s (a p 

### a 2 

### ) , bein g derive d fromasample , ar e rando mvariable s th e value s of whicho n aparticular

sampl e eithe r

d o o r d o no t includ e th e tru e valu e a o f th e parameter . However , i

n repeate dsamples , acertai n propor tio n (namel y 1-e

) o f thes e interval s wil l includ e a , provide dthat

th e actua l populatio n satisfie d th e initial hypothesis . Contamination : Contac t

wit ha n admixtur e o

f a n un natura l agent , wit

hth e implicatio n tha t

th e amoun t i s measurable . Convection : Atmospheri c motion s tha t ar e predomi

nantl y vertical , resultin g i n vertica l transpor t

an d mixin g o f atmospheri c properties . Convulsions : Violent , involuntary contractio n o r serie s of contraction s o

f th e voluntary muscles . Coproge n III : Coproporphyrinoge n III , a n inter

mediar y metabolit e i

n heme biosynthesis . I t

i s a natura l precurso r

o f heme . Coprogenase : Coproporphyrinogenase , th e enzyme that convert s coproporphyrinoge n II I t o pro toporphyri n IX . Coproporphyrin : Urinary pigment derive dfro

m coproporphyrinogen , a

n intermediat e i

n th e bio

synthesi s o

f heme . Coproporphyrinoge n (syn . coprogen) : A full y reduce dcolorles s tetracarboxyli c tetrapyrrole . Isomer s I an dII I ar e foundi n biologi c systems . Cortex : Se

e Cerebra l cortex . Corpu s callosum : Ban do f nerv e tissu e connectin g th e cerebra l hemisphere s i n ma n an dhigher

mam mals . Corpu s striatum : A subcortical mas s o f gray an d white substanc e i

n eac hcerebra l hemisphere , con tainin g th e caudat e nucleu s an dth e lentifor m nucleus . Cortica l atrophy : Wastin g awa y o f th e oute r layer(s) , e.g. , o f th e brai n o r

kidney . Creatinine : C 4 

### H 2 

### ON 3 

### ; compoun dforme db y dehydratio n o

f creatine ; foundi

n urine , blood , an dmuscle . Cristae : Inne r

membrane s o

f mitochondria , th e sur face s o f whichar e studde dwit

hroughl y spherical particle s attache dt o th e crista e b y stalks . A- 4P.7 2

Cumulativ e frequenc y distribution : Proportio n o f a distributio n tha t

lie s belo w agive n value . Curie : Uni t

o f radioactivity ; quantit y o f ra dionuclid e tha t

ha s 3. 7 x IO 1 0 disintegration s pe r minut e (dpm) . Cysteine : Amin o aci dtha t occur s a s aconstituen t o f glutation e an do f

cystine . Cytochrom e c : Smal l hem e protei n containin g on e ato mo f iro n pe r molecule ; it s principa l biologi c functio n i s i n electro n transport . Se e Cytochromes . Cytochrom e c oxidas e (cyt . a 3 ) : Enzym e tha t catalyze s th e oxidatio n o f cytochrom e c : 4 reduce dcytochrom e c + 0 2 = 4 oxidize d cytochrom e c + 2H 2 0 . Cytochrom e c reductase : Enzym e tha t catalyze s th e reductio n o f

oxidize dcytochrom e c : NADH 2 + oxidize dcytochrom e c = NA D + reduce d cytochrom e c. Cytochrom e P-450 : afc-type cytochrome , on e o f th e mixed-functio n oxidase s in th e microsoma l syste mresponsibl e fo r

th e oxidatio n o f

steroid s an ddrug s an dothe r

foreig n compounds . Cytochromes : Comple x protein/hem e respirator y pigment s occurrin g i n plan t an danima l cells , usuall y in mitochondria , tha t functio n a s electro n carrier s in biologica l oxidation . Demyelination : Destructio n o f th e myelin , afatlik e substanc e formin g asheat haroun dth e nerv e fibers . Density : Rati o o f

mas s o f asubstanc e t o th e volum e occupie db y it

(usuall y expresse di n g/cm 3 ) . Dentine : Als o dentin ; chie f substanc e o r

tissu e o f th e teeth , tha t

surround s th e toot hpul p an di s covere db y ename l o n th e crow n an db y cemen tu mo n th e root s o f

th e teeth . Denve r Developmen t

Screenin g Test : Ratin g scale s employe dt o asses s fou r area s o f

chil ddevelop

ment : (1 ) gros s motor , (2 ) fine motor-adaptive , (3 ) personal-social , an d(4 ) language . Deoxyribonuclei c aci d(DNA) : A nuclei c aci di n th e for mo f adoublestrande dheli x o f alinea r polymer ; mad e u p o f

repeatin g unit s o f

2-deoxy

ribose , phosphate , an dapurin e o r apyrimidine ; carrie r o f geneti c informatio n code di n th e se quenc e o f

purine s o r

pyrimidine s (organi c bases) . Deposition : (1 ) Deposi t o f particle s fro mth e am bien t ai r o r atmospher e ont o asurface ; (2 ) remova l o f

particle s fro minhale dai r b y th e respirator y tract . Detectio n limit : A limi t belo w whic ha n elemen t o r compoun dca n no t

b e detecte db y th e metho do r instrumen t

bein g use dfo r

analysis . Dichotomou s sampler : Air-samplin g devic e tha t separate s particulate s int o tw o fraction s o n th e basi s o f diameter ; th e cutpoin t

varie s withth e siz e o f th e aperture . Diffusion : I n meteorology , th e exchang e o f flui d parcel s betwee n region s in spac e i n apparentl y rando msmall-scal e motions . p-Dimethylaminobenzaldehyde : Ehrlich' s reagent ; (CH 3 ) 2 N.C 6 H 4 .CHO . Diphenylthiocarbazone : Se e Dithizone . Dispersion : Distributio n o f finel y divide dparticle s in amedium . Dithizone : Diphenylthiocarbazone ; C 6 H 5 N:N-CS

NH»NH-C 6 H 5 ; reagen t use din th e analysi s o f lead . Dithizon e methods : Colorimetri c method s o f analysi s fo r

lea dtha t

involv e th e reactio n o f lea d withdithizon e t o formlea ddithizonate , whic hi s measure dspectrophotometricall y at 51 0 nm . Dopamine : Hydroxytyramine , produce db y th e decarboxylatio n o f dop a(dihydroxy

- phenylalanine) , whic hi s a n intermediat e produc t in th e synthesi s o f

norepinephrine . Dorsa l roo t

ganglion : Grou p o f

sensor y nerv e cel l bodie s locate do n th e posterio r roo t o f eac hspina l nerve ; join s peripherall y withventral , o r motor , roo t t o formth e nerv e befor e it passe s outsid e th e vertebra l column . Downwind : I n th e sam e directio n tha t th e win di s blowing ; o n o r

towar dth e le e side . Dr y deposition : Th e deposi t o f particle s o n asurfac e in th e absenc e o f

precipitation . Dust : Soli dmaterial s suspende din th e atmospher e in th e for mo f

smal l irregula r

particles , man y o f whic har e microscopi c in size . Dustfall : Dr y depositio n o f airborn e dus t

particles . Dysoria : An y abnormalit y o f vascula r permeability . E. coli: Short , gram-negative , rod-shaped , enteri c bacterium . Edema : Presenc e o f

abnormall y larg e amount s o f flui di n th e intercellula r tissu e space s o f

th e body ; usuall y applie dt o th e demonstrabl e accumula

tio n o f excessiv e flui din th e subcutaneou s tissues . Electromyographic : Pertainin g t o electromyogra

phy , th e recordin g an dstud y o f th e intrinsi c electrica l propertie s o f

skeleta l muscle . A- 5P.7 3

Electro n microprobe : X-ra y metho di n whic h electron s fro mahot-filamen t sourc e ar e acceler

ate delectrostatically , the n focuse dt o a n ex tremel y smal l poin t

o n th e surfac e o f

aspecime n b y a n electromagneti c lens ; metho dfo r non destructiv e analysi s o f

chemica l compositio n b y measuremen t

o f resultin g backscatte r

o r othe r phenomena . Electronegativity : Electro-affinity . Encephalitis : Inflammatio n o f th e brain . Encephalopathy : An y degenerativ e diseas e o f th e brain . Epidemiology : Stud y o f th e distributio n an ddeter

minant s o f

diseas e i n huma n populatio n groups . Epinephrine : Hormon e secrete db y adrena l medull a tha t act s t o increas e bloo dpressur e b y mean s o f stimulatio n o f

hear t actio n an dconstrictio n o f pe riphera l bloo dvessels . Episodal : Adjectiv e i n curren t usag e tha t

denote s a n ai r pollutio n episode ; tha t i s th e occurrenc e o f short-term , pea k

ai r pollutan t

concentration s o f crisi s proportions . Epithelial : Pertainin g t o o r compose do f

epithelium ; tha t is , coverin g o f

externa l o r

interna l bod y sur faces , includin g lining s o f vessel s an dothe r

smal l cavities , compose do f

cell s joine dtogethe r

wit h cementin g substances . Equilibriu mvapo r

pressure : Vapo r

pressur e o f

a syste mi n whic htw o o r

mor e phase s o f

asubstanc e coexis t i n equilibrium . Erosion : Movemen t

o f soi l o r roc k fro mon e poin t

t o anothe r b y th e actio n o f

th e sea , runnin g water , movin g ice , precipitation , o r wind . Erythrocyt e porphyrin : Se e Fre e erythrocyt e pro toporphyrin . Erythrocyt e protoporphyrin : Se e Fre e Erythrocyt e portoporphyrin . Erythrocytes : Re dbloo dcells . Erythropoiesis : Formatio n o f re dbloo dcells . Ethylenediaminetetraaceti c aci d(EDTA) : Use din th e formo f

calcium-disodiu msal t a s achelatin g agen t t o comple x wit hlea dan dothe r metal s an d remov e the mfro mth e bod y b y urinar y excretion . Evaporation : Physica l proces s b y whic haliqui do r soli di s transforme dt o th e gaseou s state ; opposit e o f condensation . Evoked-respons e technique : A techniqu e widel y use di n electrophysiolog y i n whic hastimulu s (e.g. , electri c shock , ligh t flash , click ) i s applie d peripherall y t o th e electrod e use dt o detec t th e response . Exencephaly : A developmenta l anomal y charac

terize db y a n imperfec t cranium , th e brai n lyin g outsid e th e skull . Exposur e level : Concentratio n o f acontaminan t

t o whic hth e populatio n i n questio n i s exposed . Exudate : Material , suc ha s fluid , cells , o r cellula r debris , tha t

ha s escape dfro mbloo dvessel s an d ha s bee n deposite di n tissue s o r o n tissu e surfaces , usuall y a s aresul t

o f inflammation ; contain s hig h conten t o f protein , cells , o r

soli dmaterial s derive dfro mcells . Fallout : I n ai r

pollution , particulat e matte r tha t fall s t o th e surfac e o f

th e eart hthroug hth e actio n o f gravity ; apassiv e phenomeno n unrelate dt o at r mospheri c o r

mechanica l motion . Fancon i syndrome : I n thi s document , th e tria do f glycosuria , hyperaminoaciduria , an dhy r pophosphatemi ai n th e presenc e o f hy 7 perphosphaturi atha t

i s associate dwithinjur y t o proxima l rena l tubula r

cells . Flinch/jum p thresholds : Behaviora l testin g pro cedur e use dt o measur e pai n threshol db y measuri

n g sensitivit y t o shock . Th e shoc k intensit y at whic hanimal s first

flinc han dfirst

jum p in respons e t o foo t

shoc k i s recorded . Flux : Rat e o f

flo w o f som e quantity , ofte n use di n referenc e t o som e formo f energy ; als o calle d transport . Fornix : Genera l ter mfo r a n archlik e structur e o r th e vaultlik e spac e create db y suc hastructure ; forni x o f cerebrum—efferen t

pathwa y o f

th e hippocarri

j pus . Fre e erythrocyt e porphyri n (FED) : Se e Fre e erythrocyt e protoporphyrin . Fre e erythrocyt e protoporphyri n (FEP) : Intermedit

at e in th e biosynthesi s o f heme ; specifically , th e immediat e precurso r

t o hem e synthesi s in whic h on e ato mo f

iro n i s inserte dint o th e pro toporphyri n nucleu s t o for mheme . Use din

terchangeabl y wit herythrocyt e protoporphyri n an derythrocyt e porphyrin . Fugitiv e dust : Dus t

tha t escape s fro mindustria l pro * cesses , soi l surfaces , roadways , etc. ; dus t tha t can no t b e containe db y ai r

pollutio n contro l prac tices . /3-Galactosidase : Enzym e tha t hydrolyze s galac r toside s (compound s containin g asuga r an danon suga r component ) t o produc e D-galactose . Galena : Lea dsulfid e ore . Ganglia : Plura l o f

ganglion , agenera l ter mfo r a grou p o f nerv e cel l bodie s locate doutsid e th e centra l nervou s system ; basa l ganglia—masse s o f gra y matte r

in th e cerebra l hemisphere . A- 6Gastrointestina l mucosa : Mucou s membran e o f th e stomac han dintestine . Geometri c mean : An estimat e o f th e media n o f

alog

norma l distribution , calculate da s th e anti

logarith mo f

th e mea n o f

th e logarithm s o f

th e ob

servations . Geometri c standar ddeviation : A measur e o f disper

sio n fo r alognorma l distribution ; it i s th e anti

logarith mo f

th e standar ddeviatio n o f th e logarithm s o f

th e observations . (Als o know n a s standar dgeometri c deviation. ) Glacier : Mas s o f

lan dic e flowin g slowl y (a t presen t o r in th e past ) fro ma n accumulatio n are at o an are ao f ablation . Glacie r ice : An y ic e tha t

i s o r onc e wa s par t

o f a glacier . Glomerula r

filtration : Filtratio n o f plasm ab y th e glomerul i o f

th e kidne y tha t

remove s fluids , electrolytes ; glucose , amin o acids , an dothe r smal l molecules ; 8 0 t o 8 5 percen t o f wate r an d virtuall y al l o f

th e othe r

substance s ar e reab

sorbe db y th e proxima l tubules . Glomerulus : Anatomica l ter mdesignatin g atuf t o r cluste r o f bloo dvessel s o r

nerves ; ofte n use d alon e t o designat e rena l glomeruli , whic har e coil s o f bloo dvessels , on e projectin g int o th e ex pande den do r

capsul e o f

eac ho f th e uriniferou s tubule s o f

th e kidney . Glucose-6-phosphat e dehydrogenase : Enzym e im

portan t in maintenanc e o f

adequat e concentra tion s o f reduce dglutathion e in re dbloo dcells . Deficienc y o f

thi s enzym e i s inherite da s asex linke dtrait ; i t

mediate s th e reaction , D

glucose-6-phosphat e + NAD P= D-glucono-8

- lacton e 6-phosphat e + NADPH 2 . /3-Glucuronidase : Enzym e tha t mediate s th e hy

drolysi s o f

natura l an dsyntheti c glucuronides ; yield s /3-D-glucuronat e a s aproduct . Glutamat e dehydrogenase : Enzym e tha t mediate s th e remova l o f

hydroge n atom(s ) fro mglutamate , th e sal t o r este r o f glutami c acid , whic hi s adicar

boxyli c amin o acid . Glutathione : Tripeptid e tha t serve s a s acoenzym e an dact s a s arespirator y carrie r o f oxygen . Reduce dglutathion e (GSH ) i s presen t i n re dcell s an di s associate dwit hglucose-6-phosphat e dehydrogenas e an dreduce dnicotinamid e adenin e dinucleotid e phosphat e i n maintenanc e o f re dcel l integrity . Glycosuria : Presenc e i n th e urin e o f glucose , asim

pl e suga r forme dfro mmor e comple x sugar s an d normall y retaine din th e bod y a s asourc e o f energy . Grignar dprocess : A relativel y commo n syntheti c procedur e fo r

th e preparatio n o f

organometalli c compound s fro man organomaghesiu mprecursor . Groundwater : Al l subsurfac e water , especiall y tha t par t tha t i s in th e zon e o f

saturation . Half-life : Tim e require dfo r asyste mdecayin g at

a n exponentia l rat e (suc ha s a n elemen t in radioac

tiv e disintegration ) t o b e reduce dt o one-hal f it s initia l size , intensity , o r numerica l amount . Haze : Fin e dus t

o r sal t particle s disperse dthroug ha portio n o f

th e atmosphere ; th e particle s ar e s o smal l the y canno t

b e fel t o r individuall y see n with th e nake deye , bu t

the y diminis hhorizonta l visibilit y an dgiv e th e atmospher e acharacteristi c opalescen t

appearanc e tha t

subdue s al l colors . Hematofluorometer : Commerciall y availabl e porta bl e spectrofluoromete r use dt o measur e erythrocyt e protoporphyri n (porphyrin ) directly ; in wid e us e in lea dscreenin g programs . Hematopoiesis : Formatio n an ddevelopmen t o f bloo dcells . Hematopoieti c system : Syste mo f cell s in bon e mar row , spleen , an dlymp hnode s concerne dwithfor

matio n o f

cellula r element s o f

th e blood . Hemin : Crystallin e chlorid e o f heme , C3 4 H 33 N 4 0 4 FeCl . Heparin : Mucopolysaccharid e aci doccurrin g naturall y in variou s tissues , especiall y th e live r an dlungs ; sodiu mheparin , amixtur e obtaine d fro manima l tissues , i s an anticoagulan t use din vivo an din vitro. High-volum e sampler : Devic e fo r takin g alarg e sampl e o f

ai r i n aminima l spa n o f

time , routinel y abou t 200 0 m 3 /2 4 h r

(1.3 8 m 3 /min) , o r

eve n a s hig ha s 288 0 m 3 /2 4 h r

( 2 m 3 /min) . Hippocampus : Curve delevatio n in th e inferio r hor n o f th e latera l ventricl e o f th e brain ; importan t functiona l componen t

o f th e limbi c system , th e syste mcontrollin g autonomi c function s an dcer tai n aspect s o f

emotio n an dbehavior . Histidin e residue : On e o f th e naturall y occurrin g peptid e linkage s in aprotein , containin g th e chemica l group , imidazole :

H C = C



### II N N H 

# V C H A- 7P.7 5

Homovanilli c acid : A methylate dmetabolit e o f hy

droxytyramine :

CH 3 0 H O CH 2 -COO H Hydrocephalus : Conditio n characterize db y abnor

ma l accumulatio n o f

flui din th e crania l vault , ac companie db y enlargemen t o f th e head , promi

nenc e o f th e forehead , atroph y o f th e brain , men ta l deterioration , an dconvulsions . Hyperactivity : Abnormall y increase dactivity . Developmenta l hyperactivit y o f childre n i s characterize db y constan t motion—exploring , ex perimenting , etc.—an di s usuall y accompanie db y distractibilit y an dlo w toleranc e fo r frustration . I t usuall y abate s durin g adolescence . Ma y resul t fro mbrai n damag e o r

psychoses . Hyperkinesia : Abnormall y increase dmoto r functio n o r activity ; see Hyperactivity . Hyperkinetic : Characterize db y abnormall y in

crease dmuscula r

movement . Hyperkinetic-aggressiv e behavio r disorder : A dis

orde r characterize db y overactivity , restlessness , distractibility , an dshor t attentio n span . Hyperphosphaturia : Above-norma l amount s o f phosphat e compound s i n th e urine . Hyperuricemia : Abnorma l amount s o f uri c aci di n th e blood . Hypochromi c anemia : A conditio n characterize db y adisproportionat e reductio n o f re dcel l hemoglobin , compare dwit hth e volum e o f packe dcells . Hypophosphatemia : Abnormall y decrease damoun t o f phosphate s in th e blood . Hypothalamus : Portio n o f th e diencephalo n tha t form s th e floo r

an dpar t

o f th e latera l wal l o f

th e thir dventricl e o f

th e brain . Imidazol e group : Se e Histidin e residue . Impactor : Genera l ter mfo r instrument s tha t

sampl e atmospheri c particle s b y impaction ; suc hdevice s consis t o f ahousin g tha t

constrain s th e ai r

flo w pas t asensitize dsamplin g plate . Impinger : Devic e use dt o sampl e dus t o r othe r parti

cle s i n th e air ; draw s i n ameasure dvolum e o f ai r an ddirect s i t

throug haje t

t o impac t

o n awette d surface . In situ: I n th e origina l location . Interstitia l fibrosis : A progressiv e formatio n o f fibrou s tissu e i n th e interstice s i n an y structure ; i n th e lungs , i t

reduce s aeratio n o f

th e blood . In vitro: Outsid e th e livin g organism . In vivo: Withi n th e livin g organism . Iro n deficiency : A deficienc y o f iron-containin g food s in th e die t

suc htha t

no t enoug hiro n i s availabl e fo r

incorporatio n int o newl y forme d hemoglobin ; iro n deficienc y withi n th e bod y ma y als o resul t

fro mpoo r

intestina l absorptio n o f iro n in spit e o f

adietar y sufficiency . Ischemia : Deficienc y o f bloo di n apart , cause db y functiona l constrictio n o r actua l obstructio n o f

a bloo dvessel . Ischemic : Pertainin g to , o r affecte dwith , ischemia . Isocortex : Neopallium ; tha t portio n o f

th e cerebra l corte x showin g stratificatio n an dorganizatio n characteristi c o f

th e mos t

highl y evolve dtyp e o f cerebra l tissue . Isokineti c sampling : Takin g asampl e o f ai r withou t changin g th e spee do r

directio n o f

th e ai r a s it en ter s th e sampler . Jiggl e platform : Apparatu s use di n behaviora l test in g t o measur e an animal' s activity . Generall y consist s o f

aspring-loade dplatfor mequippe d withadetecto r

fo r measurin g movement . a-Ketoglutarate : Sal t

o f a-ketoglutari c acid , a dibasi c ket o aci doccurrin g a s a n intermediat e in carbohydrat e (Kreb s cycle ) an dprotei n metabol

ism . Kilocalorie : Uni t

o f hea t energ y equa l t o 100 0 calo

ries ; als o know n a s larg e calorie . Lacti c aci ddehydrogenas e (LDH) : Catalyze s reduc

tio n o f pyruvi c aci db y reduce dnicotinamid e adenin e dinucleotide ; prevent s buildu p o f pyru vat e i n anaerobi c glycolysis . Leached : Subjecte dt o th e actio n o f percolatin g wate r o r othe r liqui dtha t

remove s th e solubl e substances . Lea dparticles : Lead-containin g particles . Lea dpoisonin g (syn . lea dintoxication , plumbism , saturnism) : A diseas e conditio n reflectin g th e ad

vers e effect s o f

th e absorptio n o f

lea dint o th e system . Lea dsubacetat e (syn . lea dmonosubacetate , monobasi c lea dacetate) : Pb(C 2 H 3 0 2 ) 2 «2P b (OH) 2 . Learnin g paradigm : A particula r se t o f experimenta l condition s use dt o stud y learning . Ligand : A molecule , ion , o r ato mtha t

i s attache dt o th e centra l ato mo f

acoordinatio n compound , a chelate , o r

othe r complex . Lin e source : Consist s o f anumbe r

o f poin t source s arrange din astraigh t

line , usuall y acros s win d (se e Poin t

source) . A- 8P.7 6

Lipoamid e dehydrogenase : Trivia l nam e fo r lipoamid e oxidoreductase ; enzym e catalyzin g th e reaction , NA D + dihydro-lipoamid e = NADH 2 + oxidize dlipoamide . Lithosphere : Th e rigi doute r crus t o f roc k o n th e earth , abou t

8 0 k mdeep ; mor e recently , wit h developmen t

o f plat e tectonic s theory , th e oute r 100 k mo f th e earth' s surface . Lognorma l distribution : A variabl e whos e logarithm s follo w anorma l distributirin . Lumen : Th e cavit y o r channe l withi n atubula r organ ; in thi s document , intestinal . Lymphocyte : Mononuclea r leukocyt e ( awhit e bloo d cell ) wit hadeepl y stainin g nucleu s containin g dens e chromatin ; chiefl y aproduc t o f lymphoi d tissue , it participate s i n humora l an dcell-medi

ate dimmunity . Lysosome : Submicroscopi c organelle , foun db y electro n microscop e in man y type s o f cells , tha t contain s variou s hydrolyti c enzyme s an di s nor mall y involve din localize dintracellula r diges

tion . a-Mannosidase : Enzym e tha t catalyze s th e hy

drolysi s o f

a-D-mannosid e t o an aocoho l an dD

mannose , asimpl e sugar . Mas s media n diamete r

(MMD) : Geometri c media n siz e o f adistributio n o f

particles , base do n weight . Mas s media n equivalen t diamete r

(MMED) : Conve

nien t paramete r

fo r characterizin g airborn e par ticulates ; divide s th e tota l mas s o f aeroso l parti

cle s int o tw o equa l parts : hal f th e mas s reside s in a relativel y smalle r

numbe r o f particle s large r

tha n thi s media n siz e an dhal f reside s i n arelativel y large r numbe r

o f particle s havin g diameter s belo w thi s media n size . Maze : Syste mo f

intersectin g path s use di n test s o f intelligenc e an dlearnin g i n experimenta l animals . McCarth y Scale s o f

Intelligence : A standardize din

tellectua l assessmen t

instrumen t

(appropriat e fo r age s 2. 5 t o 8. 5 yr) , consistin g o f five subtest s yieldin g individua l score s in (1 ) verbal , (2 ) per ceptual-performance , (3 ) quantitative , (4 ) memo ry , an d(5 ) motor , a s wel l a s yieldin g agenera l cognitiv e inde x comparabl e t o a n intellectua l quotien t (I.Q. ) score . Mean : Use dsynonymousl y wit hth e arithmeti c mean ; tha t

is , th e su mo f

th e observation s divide d b y th e sampl e size . Meninges : Thre e membrane s tha t envelop e th e brai n an dspina l cord ; th e dur amater , pi amater , an d arachnoid . Messenge r RN A (mRNA) : Linea r polyme r

o f nucleotide s tha t

i s transcribe dfro man dcomple

mentar y t o asingl e stran do f DNA ; carrie s infor

matio n fo r

protei n synthesi s t o th e ribosomes . Metabolites : En dproduct s o f metaboli c processe s tha t transfor mon e compoun dint o anothe r i n liv

in g cells . Microcyti c anemia : Conditio n in whic hth e majorit y o f th e re dcell s ar e smalle r tha n normal . Micromelia : Developmenta l anomal y characterize d b y abnorma l smallnes s o r shortnes s o f

th e limbs . Microsome : On e o f

th e fine r

granula r

element s o f protoplasm ; par t

o f th e endoplasmi c reticulum , sit e o f variou s metaboli c an dsyntheti c processe s includin g incorporatio n o f amin o acid s int o pro teins . Mist : Microscopi c an dmor e o r les s hygroscopi c wate r droplet s suspende din th e atmosphere . Relativ e humidit y whe n mis t i s presen t

i s ofte n les s tha n 9 5 percent . Mitochondria : Smal l organelle s foun di n th e cytoplas mo f

cells ; principa l site s o f

generatio n o f energy , the y contai n enzyme s o f th e Kreb s an d fatt y aci dcycle s an dth e respirator y pathway . Mobilizabl e lead : Th e fractio n o f th e tota l lea dcon ten t o f th e bod y tha t

ca n b e remove db y chelatin g agents . Molal : Containin g on e mol e o r on e gra mmolecula r weigh t i n 100 0 gram s ( 1 kg ) o f solute . Molar : Containin g on e mol e o r on e gra mmolecula r weigh t o f solut e in 100 0 ml ( 1 liter ) o f solution . Mole : Tha t

amoun t o f chemica l compoun dwhos e mas s in gram s i s equivalen t t o it s formul amass , i.e. , mas s numericall y equa l t o th e molecula r weigh t an dmos t

frequentl y expresse da s th e gra m molecula r

weigh t (th e weigh t

o f on e mol e ex presse din grams) . Midbrain : Mesencephalon ; portion s o f th e adul t brai n derive dfro mth e embryoni c midbrain . Miniatur e end-plat e potential s (MEPP's) : Smal l po tentia l change s in th e neighborhoo do f th e en d plat e representin g th e respons e o f th e membran e t o releas e o f

acetylcholin e in quantitie s insuffi

cien t t o depolariz e th e membran e t o threshol d levels . Monoamine : Organi c compoun dt o whic ha n amin e (-NH 2 group ) i s attached ; e.g. , serotonin . Monamin e oxidase : Flavoprotei n tha t catalyze s th e aerobi c oxidatio n o f

physiologica l amine s t o th e correspondin g aldehyde s an dammonia ; act s upo n serotonin , anervou s syste mregulator , t o yiel d5

- hydroxy-indolealdehyde . A- 9P.7 7



### Monominergic : Stimulated , activated , or transmit

te db y monoamines ; applie dt o nerv e fiber s tha t liberat e monoamine s a

t asynaps e whe

n anerv e impuls e passes . Moto r skills : Skille dmovement s that depen don th e integrity o

f th e nervou s syste

mfo r control . Mutagenicity : Property o f bein g abl e t o induc e geneti c mutation , i.e. , apermanent , transmissabl e chang e i n th e geneti c material . Myelopathy : Patholog y o f th e muscl e fibers . Myxedema : Nonpittin g edem acharacterize db y dry , wax y typ e o f swelling , wit

habnorma l deposit s o

f mucin i n th e skin andothe r

tissues ; associate d wit hhypothyroidism . Nasopharynx : Th e part

of th e pharyn x tha t

lie s abov e th e level o

f th e sof t palate ; th e pharyn x bein g th e muscular , membranou s sa c between th e mouth , th e nares , an dth e esophagus . Nationa l Air

Surveillanc e Network s (NASN) : Net

work s of monitorin g station s fo

r samplin g ai r

t o determin e extent

o f pollution . Establishe djointl y b y Federa l andstate governments . Neoplasm : A

n aberran t

ne w growt ho f abnorma l cell s o r tissu e i n whichth e growt

hi s uncontrolla

bl e an dprogressive . Nephritis : Inflammatio n o f th e kidney . Nephropathy : Diseas e o

f th e kidneys . Nerv e conduction : Passag e o f anerv e impuls e manifeste db

y a n electri c impuls e that

travel s alon g th e nerve . Neuropathy : Functiona l disturbance s and/o r pathological change s i

n th e periphera l nervou s system ; affects th e neuron s (nerv e cells , includin g cel l body , axon , an ddendrites) . Neuropil : Dens e feltwor

k o f interwove n cytoplasmi c processe s o

f nerv e cell s an do

f neuroglial cell s i

n th e centra l nervou s syste

mandi n som e part s o f th e periphera l nervou s system . Nictitatin g membrane : Thi n membrane , o r inner or thir deyelid , present

i n man y animals ; capabl e o

f bein g draw n acros s th e eyeball , a s fo r protection . Norepinephrine : Hormon e secrete dby neurons ; act s a s atransmitte r

substanc e a

t th e periphera l sympatheti c nerv e ending s an dprobabl y i n certai n synapse s i n th e centra l nervou s system . Normal distributio n (Gaussian distribution) : Funda

menta l frequenc y distributio n of statistica l analysis . A continuou s variate , x , i s sai dt o hav e anormal distributio n o r t o b e normall y dis

tribute di f i t possesse s adensit

y function , f(x) , that satisfie dth e equation : f (x) =_U-( X - ^ W (-oo< X <oc) , cr27 r' 

### where fii s th e arithmeti c mea n (o r first moment ) an do - i s th e standar ddeviation . Abou t two-third s o f th e tota l are aunder

th e curv e i s include dbe

tween x = fi-a andx = fi+ o \ Normal population : Collectio n o f quantitie s havin g anormal distribution . Normoblast : Nucleate dpercurso r cel l intermediat e i n th e formatio n o

f erythrocytes . Nuclea r inclusio n bodies : Round , oval , o r ir

regularl y shape dbodie s appearin g i n th e nucle i o

f cells . Nucleus : Small mas s o

f differentiate dprotoplas m ric hi n nucleoprotein s an dsurrounde db y a membrane ; foundi

n mos t animal an dplan t

cells ; contain s chromosome s andfunction s i n metabol

ism , growth , an dreproduction . One-wa y avoidanc e tasks : Se

e Avoidanc e task . Optical emissio n spectrography : Analytical metho d i n whichth e sampl e i s vaporize dan ddecom

posed , an dth e constituen t element s excite db

y a n electrica l ar c o r

ahighvoltag e spark . Th e ligh t emitte da s aconsequenc e o f th e excitatio n passe s throug haspectrograp han dth e resultin g spectru mi s recorde dphotographically . Paraplegia : Paralysi s o

f th e leg s an dlower

part of th e body . Parenchyma : General ter mt o designat e functional element s o

f a n organ as distinguishe dfro mit s framework , o r

stroma . Particl e eddy diffusivity : Th e diffusion o f particle s b y eddie s i n aturbulen t

flow . D-penicillamine : Produc t of penicillin ; whitis h crystallin e powder

usedas ametal complexin g agent t o remov e exces s metal s fro mth e body . Peptidergic : Stimulated , activated , o r transmitte db

y peptides ; applie dt o thos e nerv e fiber s that liber

at e peptide s a

t asynaps e whe

n anerv e impuls e passes . Photolysis : Chemical decompositio n b y th e actio n o

f light . Phreni c nerve : Arisin g fro mth e third , fourth , an d fifthcervical segment s o f th e spinal cord , th e nerv e tha t innervate s th e diaphragm . Pica : Habitua l ingestio n o f nonfoo ditems . Pinna : Projectin g part

of th e ea r lying outsid e th e head . Plumbism : Leadpoisoning ; saturnism . A-1 0Poin t

source : A singl e isolate dstationar y sourc e o f pollution . Polarography : A n electroanalytica l techniqu e in whic hth e curren t

throug ha n electrolysi s cel l i s measure da s afunctio n o f th e applie dpotential . Polyneuropathy : Diseas e tha t involve s severa l nerves . Polysomes : Comple x o f ribosome s boun dtogethe r b y asingl e messenge r

ribonuclei c aci d(mRNA ) molecule . Als o know n a s polyribosome . Porphobilinoge n (PBG) : Intermediat e in th e bio

synthesi s o f

hem e tha t

doe s no t accumulat e unde r norma l circumstances . Porphyrin : An y on e o f

agrou p o f

iron-fre e o r

mag nesium-fre e cycli c tetrapyrrol e derivative s tha t occu r universall y i n protoplasm . The y formth e basi s o f th e respirator y pigments , suc ha s cytochrome s an dchlorophyll , o f animal s an d plants . Precipitation : An y o r

al l form s o f

wate r particles , liqui do r solid , tha t

fal l fro mth e atmospher e an d reac hth e ground . Prevailin g win ddirection : Win ddirectio n mos t fre

quentl y observe ddurin g agive n period . Primar y smelting : Extractio n o f meta l fro more . Promotiona l energy : Energ y require dt o promot e an electro n fro mit s fre e ato mgroun dstat e t o th e hy

bridizatio n stat e require dfo r bonding . Protoporphyri n (PP) : Porphyri n tha t i s th e protein

fre e precurso r

t o hemoglobin , myoglobin , catalase , an dcertai n respirator y pigments . Protoporphyri n IX : A n isome r o f protoporphyrin . Proxima l convolute dtubules : Convolute dportio n o f th e vertebrat e nephro n (functiona l uni t o f th e kidney ) lyin g betwee n Bowman' s capsul e an dth e loo p o f Henle ; function s i n resorptio n o f sugar , N a+ ,C1 , an dwater . Psychomotor : Pertainin g t o moto r effect s o f

cerebra l o r psychi c activity . Pyrimidine-5'-nucleotidase : Enzym e tha t mediate s hydrolysi s o f

pyrimidine-5'-phosphat e t o yeil din

organi c phosphoru s an dth e correspondin g pyrimidin e nucleoside . Pyrrole : Heterocycli c rin g compound , consistin g o f fou r carbo n atoms , on e nitroge n atom , an dfive hydroge n atoms , tha t i s acomponen t

o f chlorophyll , hemin , an dman y othe r importan t naturall y occurrin g substances . Pyruvate : Sal t

o f pyruvi c acid , an importan t inter

mediat e i n carbohydrat e (Kreb s cycle ) an dpro tei n metabolism . Reentrainment : Resuspensio n o f particulat e matter , especiall y dust , in th e ambien t air ; se e tex t

dicus

sio n o f resuspension . Referenc e method : I n thi s document , th e official , ac cepte dmetho dfo r

samplin g an danalysi s o f an elemen t o r compound ; metho dt o whic hothe r method s ar e compare dfo r accurac y an dpreci

sion , and/o r

fo r reportin g o f

data . Relativ e humidity : Dimensionles s rati o o f actua l vapo r pressur e o f

th e ai r t o th e saturatio n vapo r pressure ; usuall y expresse da s percent . Rena l insufficiency : Stat e i n whic hth e kidney s ar e unabl e t o remov e asufficien t proportio n o f

th e effete , o r spent , matte r

o f th e blood . Reticulocytosis : Increas e i n th e numbe r o f reticulocyte s (youn g re dbloo dcell s showin g basophili c networ k

unde r vita l staining ) in th e pe riphera l blood . Ribonuclei c aci d(RNA) : Nuclei c aci din th e formo f alinea r polymer , usuall y asingl e strand , com pose do f

repeatin g unit s o f

nucleotide s (th e organi c bases ; adenine , cytosine , guanine , an d uracil ) conjugate dt o ribos e an dkep t in sequenc e b y phosphodieste r

bonds . Involve din

tracellularl y in protei n synthesis . Ribosomes : Comple x smal l particle s in th e livin g cell , compose do f

variou s protein s an dthre e molecules.o f

RNA ; sit e o f

synthesi s o f

proteins . Samplin g error : Differenc e betwee n ameasure d valu e an dth e tru e valu e tha t result s fro msam plin g technique s an dprocedures . Samplin g train : Pollutan t collectin g devic e consist

in g o f aserie s o f

component s throug hwhic ha n ai r strea mpasses . Component s usuall y includ e prefitter ; pipe s o r

ducts ; mean s fo r

measurin g ai r flow ; a n ai r

pump ; an dadetecto r

o r senso r tha t give s an immediat e readin g or acollecto r

i n whic hth e pollutan t

i s subsequentl y measured . Saturnism : Lea dpoisoning . Schwan n cell : On e o f

th e larg e nucleate dmasse s o f protoplas mlinin g th e inne r surfac e o f

th e neurilemma , amembran e wrappin g th e nerv e fiber. Secondar y smelting : Extractio n o f meta l fro mscra p an dsalvage . Sedimentation : Th e ac t o r proces s o f

depositio n o f sediment ; ca n refe r

(1 ) t o th e depositio n o f air

born e particulat e matte r o n asurfac e o r

(2 ) t o th e depositio n an daccumulatio n o f soli dmatte r

o n th e be do f

abod y o f

water . Seizure : Sudde n onse t

o r recurrenc e o f

adiseas e o r a n attack ; specifically , a n epilepti c attack , o r con vulsion . A-l lP.7 9

Septum-fronta l forebrain : Describe s anatomica l connection s i n th e brai n betwee n th e septa l are a an dth e forebrain . Sequela : An y lesio n o r affectio n tha t

follow s o r

i s cause db y a n attac k

o f disease . Serotonin : A vasoconstrictor , 5-hydroxytryptamine , foun din seru man dman y bod y tissues , includin g th e intestina l mucosa , pinea l body , an dcentra l nervou s system , especiall y th e hypothalamus , midbrain , basa l ganglia , an dspina l cord ; believe d t o b e aneurotransmitte r tha t play s aregulator y rol e i n th e centra l nervou s system . Seru mglutamic-oxaloaceti c transaminas e (SGOT) : Enzym e tha t

transfer s a n amin o grou p fro mL

glutami c aci dt o oxaloaceti c acid , formin g 8

- ketoglutari c aci dplu s L-asparti c acid . Ox

aloaceti c an d8-ketoglutari c acid s ar e bot hmajo r intermediate s in th e citri c aci dcycl e (Kreb s cy cle) , th e energy-generatin g cycle . Seru mglutamic-pyruvi c transaminas e (SGPT) : Enzym e tha t

transfer s an amin o grou p fro mL

glutami c aci dt o pyruvi c acid , formin g 8

- ketoglutari c aci dplu s L-alanine . 8-Ketoglutari c aci di s amajo r

intermediat e i n th e Kreb s cycle , an dpyruvi c aci di s th e immediat e precurso r o f acetylcoenzym e A , whic hcombine s wit hox aloaceti c aci dt o formcitri c aci din th e citri c aci d cycl e (Kreb s cycle) . Shuttl e box : Two-compartmen t chambe r

use din anima l behavior ; th e movemen t fro mon e com partmen t t o th e othe r

i s th e behavio r

tha t i s studied . Sore t band : Ban di n th e viole t en do f th e spectru mo f hemoglobin . Spin abifida : Developmenta l anomal y characterize d b y defectiv e closur e o f

th e bon y encasemen t

o f th e spina l cord . Stabilimeter : Devic e use dt o measur e a n animal' s ac tivit y b y measurin g vertica l movemen t o f th e floor . Stac k emissions : Effluent s release dint o th e at mospher e fro mth e exhaus t flu e o f abuilding ; usuall y refer s t o pollutant s bu t ca n refe r

t o stea m o r othe r nonpollutin g effluents . Standar ddeviation : A measur e o f dispersio n o r variation , usuall y take n a s th e squar e roo t o f th e variance . Standar dgeometri c deviation : Measur e o f disper

sio n o f value s abou t

ageometri c mean ; th e por tio n o f th e frequenc y distributio n tha t i s on e stan dar dgeometri c deviatio n t o eithe r sid e o f th e geometri c mea n account s fo r 6 8 percen t

o f th e tota l samples . Standar dnorma l deviation : Measur e o f dispersio n o f value s abou t

amea n value ; th e positiv e squar e roo t o f th e averag e o f

th e square s o f

th e in

dividua l deviation s fro mth e mean . Stanford-Bine t

I.Q . Test : A standardize dintellec

tua l assessmen t

instrumen t

(appropriat e fo r

age s 2 y r t o adult) , yieldin g agenera l intelligenc e quo tien t (I.Q. ) score . Stead y stat e exposure : Exposur e t o a n environmen

ta l pollutan t

whos e concentratio n remain s con stan t fo r aperio do f

time . Stoichiometry : Numerica l relationshi p o f element s an dcompound s a s reactant s an dproduct s in chemica l reactions . Stratosphere : Atmospheri c shel l abou t 5 5 k mdee p tha t begin s wher e th e tropospher e ends , a t 1 0 t o 2 0 k mfro mth e earth' s surface . Striatum : Corpu s striatum ; subcortica l mas s o f gra y an dwhit e substanc e in fron t o f an dlatera l t o th e thalamu s in eac hcerebra l hemisphere . Stroma : Supportin g tissu e o r matri x o f

a n organ , a s distinquishe dfro mit s functiona l element , o r parenchyma . Subclinica l lea dpoisoning : Toxi c effect s o f lea dtha t d o no t produc e clinicall y discernibl e signs . Succinate : Sal t

o f succini c acid , importan t inter

mediat e in carbohydrat e (Kreb s cycle ) an dpro tei n metabolism . Succinoxidase : Comple x enzym e system , containin g succini c dehydrogenas e an dcytochromes , tha t catalyze s th e conversio n o f succinat e an dmolecu

la r oxyge n t o fumarat e ( aKreb s cycl e intermedi

ate) . Succiny l coenzym e A : COOH(CH 2 ) 2 COOH-S-CoA ; compoun dforme dfro msuccini c aci dan d coenzym e A in th e citri c aci dcycl e (Kreb s cycle) . I t provide s fre e energ y fo r th e synthesi s o f

a molecul e o f

AT Pan dca n participat e in acylatin g reaction s fo r

th e introductio n o f

asucciny l group ; it als o participate s i n othe r metaboli c reactions , suc ha s th e synthesi s o f porphyrins . Sulfhydry l group : Th e -S H grou p occurrin g i n reduce dglutation e an di n cysteine . Superio r cervica l ganglion : A grou p o f nerv e cel l bodie s locate doutsid e th e centra l nervou s system , situate dnea r

th e cervix . Surfac e water : Al l bodie s o f wate r o n th e surfac e o f th e earth . Synapse : Regio n o f

contac t betwee n processe s o f

tw o adjacen t neurons . Synapti c uptake : Movemen t o f achemica l int o th e neuro n i n th e are ao f

th e synapse . A-1 2P.8 0

Synaptosoma l transport : Uptak e o f achemica l int o isolate dsynapses . Synergetic : Workin g together ; an agen t tha t work s synergisticall y withon e o r mor e othe r

agents . Synergisti c effects : Join t effect s o f

tw o o r mor e agents , suc ha s drug s tha t increas e eac hother' s effectivenes s whe n take n together . Telencephalon : Paire dcerebra l vesicles , fro mwhic h th e cerebra l hemisphere s ar e derived . Teratology : Scienc e tha t deal s wit habnorma l developmen t

o f th e fetu s an dcongenita l malfor

mations . Teratospermia : Presenc e o f malforme dspermatozo a i n th e semen . Temperatur e inversion : Laye r o f ai r in whic htem peratur e increase s withaltitude ; ver y littl e tur bulen t exchang e occur s withi n it . Termina l velocity : Se e Termina l fal l velocity . Termina l fal l velocit y (termina l velocity) : Particu

la r fallin g speed , fo r

an y give n objec t

movin g throug haflui dmediu mo f specifie dphysica l properties , a t

whic hth e dra g force s an dbuoyan t force s exerte db y th e flui do n th e objec t jus t equa l th e gravitationa l forc e actin g o n th e object , afte r whic hit fall s at constan t

spee dunles s i

t move s int o ai r layer s o f

differen t physica l properties . I n th e atmosphere , th e latte r effec t i s s o gradua l tha t object s suc ha s raindrops , whic hattai n termina l velocit y a t

grea t height s abov e th e surface , ma y b e regarde da s continuousl y adjustin g thei r speed s t o remai n at

al l time s essentiall y i n th e termina l fal l condition . Topography : (1 ) Genera l configuratio n o f asurface , includin g it s relief ; ma y b e alan do r water-bot

to msurface ; (2 ) natura l surfac e feature s o f a region , treate dcollectivel y a s t o form . Transaminases : Enzyme s tha t catalyz e th e transfe r o f a n amin o grou p o f

a n amin o aci dt o aket o aci d t o for manothe r

amin o acid ; als o know n a s aminotransferases . Transfe r RN A (tRNA) : Smalles t ribonuclei c aci d molecul e foun di n cells ; it s structur e i s comple

mentar y t o messenge r

RN A an dit

function s in transferrin g amin o acid s fro mthei r fre e stat e t o a growin g polypeptid e chain . Transformation : I n thi s document , change s in physi

ca l o r chemica l formo f

lead-containin g particle s o r compound s tha t

occu r withtim e an dspac e durin g atmospheri c an denvironmenta l residenc e and/o r transport . Translocation : Transfe r o f metabolites , nutritiv e materials , o r

othe r substance s fro mon e par t o f a plan t t o another . Transport : I n thi s document , movemen t o f lea dan d it s compound s fro mon e plac e t o anothe r i n th e environment . Transudation : Passag e o f seru mo r

othe r bod y flui d throug hamembran e o r tissu e surface ; ma y o r ma y no t b e th e resul t

o f inflammation . Troposphere : Th e atmospheri c shel l extendin g abou t 1 0 t o 2 0 k

mfro mth e earth' s surface . Trypa n Blue : A n acid , az o dy e use din vita l staining ; unde r norma l conditions , it

doe s no t

ente r mos t area s o f th e brai n fro mth e blood . Tumor : An y abnorma l mas s o f cell s resultin g fro m excessiv e cellula r

multiplication . Turbulence : Stat e o f

flui dflow in whic hinstan

taneou s velocitie s exhibi t irregula r

an dap parentl y rando mfluctuation s s o that , in practice , onl y statistica l propertie s ca n b e recognize dan d analyzed ; turbulenc e ca n transpor t suspende d matte r at rate s fa r in exces s o f

rate s o f transpor t b y diffusio n an dconductio n i n alamina r flow . Two-wa y aviodanc e tasks : Se e Avoidanc e task . Tyrosine : Amin o aci d(p-hydroxyphenylalanine , CgHnOjN ) foun din mos t protein s an dsyn thesize dmetabolicall y fro mphenylalanine . I t i s a precurso r

o f dopamin e an do f

th e hormones , epinephrine , norepinephrine , an d triiodothyronine . Ultradia n rhythms : Biologica l rhyth mwit hafre

quenc y highe r

tha n circadia n (2 4 hr) . Uncertainty : Standar ddeviatio n o f asufficientl y larg e numbe r

o f measurement s o f

th e sam e quan tit y b y th e sam e instrumen t o r methods ; th e non correctabl e inaccurac y o f th e instrument . Upwind : Towar dth e directio n fro mwhic hth e win d i s flowing ; counte r

t o th e wind . Urobilinogen : Colorles s compoun dforme di n th e in

testin e b y th e reductio n o f bilirubi n ( abil e pig

men t tha t i s abreakdow n produc t o f heme) ; som e i s excrete di n th e fece s wher e i t i s oxidize dt o urobilin ; som e i s reabsorbe dan dreexcrete din th e bil e (a s bilirubin ) o r

in th e urine . Uroporphyrin : An y o f

severa l isomeric , metal-fre e porphyrins , occurrin g in smal l quantitie s in nor ma l urin e an dfeces . Vacuolization : Formatio n o f vacuoles , an y smal l space s o r cavitie s forme din th e protoplas mo f a cell . A-1 3P.8 1



### Vacutainers : Registere dtrademark o f seale dam pules , maintaine dunder

aslight vacuuman dcon tainin g a n anticoagulant , int o whichbloo dsam ple s ma y b e draw n directly . Vanilly l mandeli c aci d(vanilmandeli c acid) : A ma jo r metabolit e o

f th e catechloamines ; usedt o asses s quantitativel y th e endogenou s productio n o f catecholamines . Variance : A measure o

f dispersio n o r

variatio n o

f a sampl e fro

mit s expecte dvalue . It i s usuall y calculate da s asu

mo f square ddeviation s abou t a mea n divide db

y th e sampl e size . Wechsler Intelligenc e Tes t

(WISC) : A standardize d intellectua l assessment

instrumen t

(appropriat e fo r age s 6 y r t o 1 6 y r 1 1 mo) , consistin g o

f 1 2 sub

test s designe dt o yiel dverba l an dperformanc e in

tellectua l scores . Wet deposition : Removal o

f particle s fro

mth e at mosphere vi aprecipitation ; rainout . Wind : Air motio n relativ e t o th e surfac e o f th e earth . Vertica l component s ar e relativel y small , especiall y near

th e surfac e o

f th e earth ; hence , th e termdenote s almos t

exclusivel y th e horizonta l component . WPPS I Test : A versio n of th e WIS C test , bu t

consist

ing o f 1 0 subtest s representin g adownwardexten sio n of th e WIS C appropriat e for younge r childre n (age s 4 t o 6. 5 yr) . Xenobiotics : Chemical s foreign t o biologi c systems . X-ray diffractio n analysis : Analysi s o f th e crystal structur e o

f material s b

y passin g Xray s throug h themandregisterin g th e diffractio n (scattering ) imag e o f th e rays . X-ray powder

diffractio n techniques : Analytical technique s i

n whicha

n X-ray bea

mo f known wavelengt hstrike s afinely groun dpowder sam ple ; th e crystal plane s o

f th e powder

diffrac t th e bea man dthes e diffractio n line s ar e recorde don photographi c film. X-ray spectrography : Analytical metho demployin g a n X-ray spectromete r

(instrumen t

fo r producin g th e X-ray spectru mo

f amaterial andmeasurin g th e wavelength s o

f components ) that

i s equippe d wit hphotographi c o r

othe r recordin g apparatus . Zin c erythrocyt e porphyrin : Th e biochemicall y cor rec t for mfo r th e erythrocyt e protoporthyri n o r porphyri n that

i s elevate di

n leadexposure o r iro n deficienc y anemia . Usedinterchangeabl y i n thi s documen t

wit herythrocyt e porphyrin , erythrocyt e protoporthyrin , an dfree erythrocyt e porphyri n o r

protoporthyrin .

A-1 4P.8 2



## APPENDI X B PHYSICAL/CHEMICA L DAT A FO RLEA D COMPOUND S B. l DAT A TABLE S TABL E B-1 , PHYSICA L PROPERTIE S O F INORGANI C LEA D COMPOUNDS ' Compoun d Lea d Acetat e Azid e Bromat e Bromid e Carbonat e Carbonate , basi c Chlorid e Chlorobromid e Chromat e Chromate , basi c Cyamid e Fluorid e Fluorochlorid e Format e Hydrid e Hydroxid e lodat e Iodid e Nitrat e Nitrate , basi c Oxalat e Oxid e d i Oxid e Oxid e (red ) Phosphat e Sulfat e Sulfid e Sulfit e Thiocyanat e Abbreviations : a - aci d a l - alcoho l al k - alkal i d - decompose s exp l - explode s Formul a

P b Pb(C 2 H 3 0 2 ) 2 Pb(N 3 ) 2 Pb(Br0 3 ) 2 -H 2 0 PbBr 2 PbC0 3 2PbC0 3 -Pb(OH) 2 PbCI 2 PbCIB r PbCr0 4 PbCr0 4 -Pb O Pb(CN) 2 PbF 2 PbFC I Pb(CHO) 2 PbH 2 Pb(OH) 2 Pb(l0 3 ) 2 Pbl 2 Pb(N0 3 ) 2 Pb(OH)(N0 3 ) PbC 2 0 4 Pb O Pb0 2 Pb 3 0 4 Pb 3 (P0 4 ) 2 PbS0 4 Pb S PbS0 3 Pb(SCN) 2 gly c- glyco l i - insolubl e s - solubl e M.W . - molecula rweigh t S.G . - specifi cgravit y MP. - meltin g poin t M.W . 207.1 9 325.2 8 291.2 3 481.0 2 367.0 1 267.2 0 775.6 0 278.1 0 322.5 6 323.1 8 546.3 7 259.2 3 245.1 9 261.6 4 297.2 3 209.2 1 241.2 0 557.0 0 461.0 0 331.2 0 286.2 0 295.2 1 223.1 9 239.1 9 685.5 7 811.5 1 303.2 5 239.2 5 287.2 5 323.3 5 S.G . 11.35 3.2 5 — 5.5 3 6.6 6 6. 6 6.1 4 5.8 5 — 6.1 2 6.6 3

— 8.2 4 7.05 4.6 3 — — 6.15 5 6.1 6 4.5 3 5.9 3 5.2 8 9.5 3 9.37 5 9. 1 7 6. 2 7. 5 — 3.8 2 M.P .

327. 5 28 0 expl . d18 0 37 3 d31 5 d40 0 50 1 — 844 — — 85 5 60 1 d19 0 d d14 5 d30 0 40 2 d47 0 d18 0 d30 0 88 8 d29 0 d50 0 101 4 1170 111 4 d d19 0 Solubility , g/10 0 Col d wate r i 44. 3 0.02 3 1.3 8 0.844 1 0.0001 1 i 0.9 9 — 6x10- 6 i s i s 0.064 0.03 7 1. 6 — 0.015 5 0.001 2 0.06 3 37.6 5 19. 4 0.0001 6 0.001 7 i i 1.4x10- 5 0.0042 5 8.6x10- 5 i 0.0 5 Ho t

wate r i 2215 0 0.097 0 S i s 4.7110 0 d i 3.3410 0 — i i s — 0.108 1 2 0 — s i s 0.00 3 0.4 1 12 7 s — — 0.005 6 — i 0. 2 m l Othe r

solvent s s a sgly c — — s a sa.al k sHN0 3 ia l — sa.al k sa.al k sKC N sHN0 3 — ia l — sa.al k sHN0 3 s.al k s.al k s a s a s.al k s a s a . s.al k — s a s a s.al k



### B- lP.8 3

TABL E B-2 . TEMPERATUR E VARIATIO N O F TH E VAPO R PRESSURE S O F COMMO N LEA D COMPOUNDS * Nam e Lea d Lea d bromid e Lea d chlorid e Leadflourid e Lea d iodid e Lea d oxid e Lea d sulfid e Formul a P b PbBr 2 PbCI 2 PbF 2 Pbl 2 Pb O Pb S MP .

327. 4 37 3 50 1 85 5 40 2 89 0 111 4 1 m m

97 3 51 3 54 7 soli d 47 9 94 3 85 2 (solid ) 10m m

1162 61 0 64 8 90 4 57 1 1085 97 5 (solid ) Temperatur e " C

40m m 130 9 68 6 72 5 100 3 644 118 9 . 1048 (solid ) 100m m

142 1 74 5 784 108 0 70 1 1265 110 8 (solid ) 400m m

163 0 85 6 89 3 121 9 80 7 1402 122 1 760m m

1744 91 4 95 4 129 3 87 2 1472 128 1 

### B.2 . TH E CHELAT E EFFEC T Th e stability constant s o

f chelate dcomplexe s ar e normall y several order s o f magnitud e higher

than thos e o f comparabl e monodentat e complexes ; thi s effec t i s calle dth e chelat e effec t andi s ver

y readil y explaine di

n term s o f kineti c considerations . A com pariso n o f th e bindin g o

f asingl e bidentat e ligan d wit hthat o f tw o molecule s o

f achemicall y simila

r monodentat e ligan dshow s that , fo r th e monodentat e case , th e proces s ca

n be represente db

y th e equa tions : M + BF=^M- B (B-l )



### M- B + Br=^MB 2 

### (B-2 ) k d 

### Th e relate dexpression s fo r th e bidentat e cas e are : Th e overal l equilibriu mconstants , therefore , are :

K 

### '-k b 

### k d ; K 

### 2

- k 2 

### k4 

### Fo r agiven metal, M , andtw o ligands , B an dB-B , whichar e chemicall y similar , i t i s establishe dthat

k , an dk a

### hav e value s simila r t o eac hother , a s d o k 2 

### andk b 

### , k 4 

### andk d 

### ; eacho

f thes e pair s o

f term s repre sent s chemicall y simila

r processes . Th e origi n o

f th e chelat e effec

t lie s i n th e ver y larg e valu e o

f k 3 

### rela

tiv e t o that

o f kc 

### . Thi s come s abou t

becaus e k 3 

### repre sent s aunimolecula

r process , wherea s k c 

### i s a bimolecular

rat e constant . Consequently , K2 

### »K, . Thi s concep t

can , o f course , b e extende dto'poly

dentat e ligands ; i

n general , th e more extensiv e th e chelation , th e more stabl e th e meta l complex . Hence , on e woul danticipate , correctly , tha t poly

dentat e chelatin g agent s suc ha s penicillamin e o r EDT A ca n for mextremel y stabl e complexe s wit h meta l ions .

M + B-BF=^M-B- B (B-3 ) B. 3 REFERENCE S FO R APPENDI X B

M-B- B =*rv K )

L B y 1 . Handboo k o f Chemistr y an dPhysics . 56t hEd . R.C . Weas t (ed.) . Cleveland , Th e Chemica l Rubbe r Co . 1975 . (B-4 ) 2 . Stu.ll . D.R . Vapo r pressur e o f

pur e substances : Organi c com pounds . Ind . Eng . Chem . J9(4): 5 1 7-540 . 1947 .

B- 2

# APPENDIX C

ADDITIONA L STUDIE S O F ENVIRONMENTA L CONCENTRATION S O F LEA D Thi s collectio n o f

studie s i s intende dt o exten d an ddetai l th e genera l pictur e o f lea dconcentration s in th e environmen t

an din proximit y t o identifie d majo r source s a s portraye din Chapte r 7 . Th e lis t

i s b y n o mean s all-inclusive , bu t i s intende dt o b e representativ e an dt o supplemen t th e dat acite din Chapte r 7 . C. l GENERA L CENTRATION S AMBIEN T AI RCON C.l . 1 Seven-Cit y Stud y A specia l lea dstud y (Seven-Cit y Study ) wa s con ducte dfo r

12-mont hperiod s betwee n 196 8 an d 197 1 i n Cincinnati , Lo s Angeles , Philadelphia , Houston , Ne w Yor k

City , Washington , D.C , an d Chicago . Sample s o f

ambien t ai r wer e analyze db y atomi c absorptio n spectroscopy . Th e monthl y averag e lea dconcentration s obtaine dar e sum marize din Tabl e C-1 . Thi s study , specificall y designe dt o measur e am bien t lea dconcentration s at avariet y o f

site s withi n eac ho f th e cities , incorporate dtechnique s tha t woul dprovid e th e mos t precis e measur e o f

ambien t lea dconcentration s available . A membran e filte r wa s use dinstea do f

aglas s filter , an dth e sample s wer e collecte dcontinuousl y ove r 2 t o 3 day s rathe r tha n collecte din biweekl y 24-h r period s a s in th e NASN . Th e hig hannua l averag e lea dconcentration s foun din th e Lo s Angele s are aar e largel y attributa

bl e t o heav y automotiv e emissions . C.l. 2 Birmingham , Alabam a Durin g 196 4 an d1965 , seasona l level s o f trac e metal s wer e determine dfro msuspende dparticulat e sample s collecte da t

1 0 are asamplin g site s at Bir

mingham , Alabama , a s apar t o f th e Alabam a Respirator y Diseas e an dAi r Pollutio n Stud y initi

ate di n 1962 . Thi s monitorin g stud y produce ddat a representativ e o f

are asourc e industria l pollution . Sample s fro meac ho f

th e 1 0 site s wer e composite d o n aseasona l basi s t o giv e atota l o f 4 0 poole dsam ples . Th e lea ddat aar e summarize di n Tabl e C-2 . Th e maximu mseasona l lea dconcentratio n (3. 5 /ug/m 3 ) occurre dat

Birmingha msit e 4 durin g th e winter . Onl y 2 site s showe daverag e concentration s > 2 figlm 3 fo r

th e year , Birmingha msit e 4 (3. 0 figlm 3 ) an dTarran t

(2. 3 /Ag/m 3 ) . Thes e result s ar e typica l fo r

amedium-size dindustrialize durba n area . C . 1. 3 Kanawh aValley , Wes tVirginia 3 A comprehensiv e ai r

pollutio n stud y wa s con ducte din th e Kanawh aRive r Valle y in th e vicinit y o f Charleston , Wes t

Virgini a(Figur e C-1) , durin g 196 4 an d1965 . Twenty-four-hou r sample s o f

sus pende dparticulat e matte r wer e collecte da t

1 4 strategicall y locate dsites . Sample s fro mselecte d site s wer e composite do n aseasona l basi s (fal l 1964 , winte r 196 4 an d1965 , an dsumme r 1965 ) an dth e composite s wer e analyze dfo r trace-meta l conten t

b y th e NAS N emissio n spectrographi c procedure . Th e dat afo r lea dar e presente din Tabl e C-3 . Highes t concentration s o f

suspende dlea dwer e foun ddurin g th e fal l o f

196 4 a t th e St . Albans , Kanawh aCity , an d Charlesto n sites . Lea din dustfal l measurement s (settle dparticu

lates ) fo r th e sam e station s ar e als o presente di n Tabl e C-3 . Th e dustfal l wa s collecte db y exposin g wide-mout hjar s fo r

aperio do f

1 month ; the n com posit e sample s wer e analyzed . Th e highes t averag e concentration s o f

settle dlea doccurre da t th e Smither s sit e (11. 2 mg/m 2 -mo) , an dat th e Sout h Charleston-Eas t

sit e (11. 6 mg/m 2 -mo) . Th e combustio n o f

soli d.fuel s (coa l an dcoke ) i s th e primar y sourc e o f

lea demission s in th e Kanawh a Valley . Additiona l source s ar e metallurgica l opera tions , asphal t

hot-mi x production , an dothe r in

dustria l processes . I n mos t cases , thes e source s hav e inadequat e ai r

pollutio n contro l equipment . Th e lea dconcentration s foun dar e somewha t lo w whe n C- 1P.8 5

TABL E C-1 . SUMMAR YO F MONTHL YAVERAG E LEA D CONCENTRATION S FOUN D I N SEVEN-CIT YSTUDY '

City LO S Angele s

Philadelphi a

Cincinnat i

Lo s Alamo s Housto n

Chicag o

Washington , D.C .

Ne wYor k

a C - commercial ; I - industrial ; R Sit e type 8 C C R R R R I C M C C I R M R R R R C R ' I P F F R C R C C C M R R R M R M C R R M R R C C R R F R R M M R R M R R R R Month s o f dat a 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 7 1 2 1 2 1 2 7 1 2 1 2 1 2 1 2 1 2 1 2 1 1 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 Monthl y concentration ,

Min . 2. 4 2. 6 2. 1 2. 7 2. 1 1. 4 1. 7 2. 5 1. 3 1.2 2. 6 1. 5 0. 9 0. 6 0. 6 1. 1 0. 8 0. 7 1. 3 0. 8 1. 2 0. 5 0. 1 0. 2 0. 1 Q 1 0. 7 0. 7 1. 2 1. 5 1. 0 0. 6 0. 6 1. 0 1. 1 1. 0 1. 3 1. 4 1.2 0. 9 1. 1 1.2 0. 7 1. 2 1. 6 1.4 1. 0 0. 9 1. 8 0. 8 1. 1 1.4 1. 4 1. 3 1. 2 6. 8 0. 9 0. 9 0. 8 ( i g/m 3 Max . 5. 8 6. 8 5. 0 5. 4 4. 4 3. 9 7. 0 7. 6 2. 7 2. 6 5. 1 3. 0 2. 0 1. 7 1. 5 2. 6 1. 7 1. 6 3. 1 2. 6 2. 8 1. 2 0. 5 0. 5 0. 3 0. 3 2. 7 1. 9 3. 2 4. 1 2. 2 1. 4 1. 2 1. 7 1. 7 2. 1 2. 2 2. 3 2. 2 2. 7 2. 1 3. 5 1. 6 2. 2 3. 9 2. 8 1. 7 1. 6 3. 5 1. 8 2. 9 2. 6 2. 1 2. 2 2. 7 1. 9 1. 6 1.4 1.4 Avg . 4. 2 4. 5 3. 6 3. 8 3. 1 2. 5 3. 7 4. 8 1.9 1. 8 3. 8 2. 2 1. 4 1. 1 1. 1 1.7 1.3 1. 0 2. 0 1. 5 2. 2 0. 9 0. 3 0. 3 0. 2 0. 2 1. 2 1. 1 2. 2 2. 4 1.3 0. 9 0. 8 1.3 1.4 1.6 1.8 1.9 1.6 1.3 1.6 2. 0 1. 1 1.7 2. 3 1.8 1.2 1. 1 2. 4 1. 1 1.7 2. 1 1.7 1.7 2. 1 1. 4 1.2 1.2 1. 1

- residential ; M - mixed ; F - farm ; an d P - park . TABL E C-2 . SEASONA L LEA D CONCENTRATION S I N BIRMINGHAM , ALABAMA , AREA , 1964-196 5

(/xg/m' )

Plac e Besseme r Birmingha m Birmingha m Birmingha m Birmingha m Fairfiel d Irondal e Mt . Broo k Tarran t Vestavi a Sit e

1 3 4 5 7 1 1 1 1 1 Seasona l averag e Sprin g 0. 9 0. 7 3. 2 1.2 1.2 0. 6 0. 6 0. 5 1. 1 0. 8 Summe r 0. 7 1. 4 2. 8 1. 6 1.4 0. 5 0. 4 0. 6 1. 8 0. 8 concentration s

Fal l 1. 1 1.7 2. 3 1. 8 1.3 0. 6 0. 9 1.0 3. 0 0. 5 Winte r 0. 6 1.4 3. 5 0. 8 1. 8 0. 3 0. 6 0. 5 3. 4 0. 7 Stud y perio d

averag e concentratio n 0. 8 1. 3 3. 0 1. 4 1. 4 0. 5 0. 6 0. 6 2. 3 0. 7 

### on e consider s th e diversity o f industria l activit

y and th e meteorological an dtopographi c characteristic s prevailing . Th e highes t

value s foundwer

e associate d wit hsamplin g site s adjacent

t o major traffi c arteries , whichdemonstrate s th e contributio n fro mmobil e sources . C . 1. 4 Stud y of Lea d Depositio n in 7 7 Cities 4 

### Settle dparticulate s wer

e collecte di

n 7 7 mid

wester n citie s fro

mSeptember

throug hDecember 1968 . Withi n eachcity , site s were chosen t o repre sent residential , commercial , andindustria l areas . Th e leadconten t

o f th e settle dparticulate s was determine db

y atomi c absorptio n spectrophotome

try , andth e deposition s wer e expresse da s mg/m2



### - mo . Th e highes t

amount s foundi

n residential , com mercial , andindustrial area s wer e i n Sout hBend , Indian a(8 0 mg/m2 

### -mo i n November) ; Nashville , Tennesse e (34 6 mg/m2 

### -mo i n October) ; andOmaha , Nebrask a(13 7 mg/m2 

### -mo i n November) ; respec tively . Maximumreading s b y mont hoccurre di

n Muncie , Indian a(industrial ) (10 5 mg/m2 

### -mo i n Sep

tember) ; Nashville , Tennesse e (commercial ) (34 6 mg/m2 

### -mo i

n October) ; Omaha , Nebrask a(in

dustrial ) (13 7 mg/m 2 

### -m o in November) ; an d Waterloo , Iow a(industrial ) (9 4 mg/m 2 

### -m o i n , December) . Th e dat aar e summarize di n Tabl e C-4 . C. 2 SOURCE-ORIENTE D AMBIEN T AI R CONCENTRATION S C.2. 1 Souther

n Solano County , California3 

### Th e State o

f Californi aAir

Resource s Board coordinate dajoin t

study , conducte db

y several stat e agencie s between Marc h197 0 an dNovember 1971 , t o determin e th e caus e o f deatho f anumber

o f horse s i n th e Benici aare afro

m196 8 t o 1970 . Figure C- 2 i s ama

p o f thi s are ashowing samplin g site loca

tions . Th e evidenc e strongl y suggeste dthat th e C- 2TABL E C-3 . LEA D DAT A FRO M KANAWH A

VALLEYSTUDY'

Samplin g sites . locatio n an d no . Fall s View(1 ) Smither s (5 ) Montgomer y(6 ) Ceda rGrov e (7) Marmet(11 ) Kanawh a Cit y(13 ) Charlesto n (15 ) Wes t Charlesto n (17 ) Nort h Charleston- W (19 ) Sout h Charleston- E (20 ) Dunba r(22 ) St . Alban s (24 ) Nitr o (25 ) Nitro-Wes t (27 ) Fal l 1964 — 0. 4 — 0. 5 — 2. 1 — — — 2. 7 — 1.3 1.0 — Winte r

1964-196 5 0. 2 0. 3 0. 6 0. 4 0. 5 0. 8 0. 9 0. 7 0. 7 0. 6 0. 4 0. 9 1. 4 0. 1 Sprin g

1965 — 0. 3 — 0. 2 — 0. 6 — — — 0. 6 — 0. 3 0. 2 — Summe r

1965 0. 0 — 0. 4 — 0. 5 — — — 1. 0 — 0. 4 0. 3 — Stud yperio d

averag e — 0. 2 — 0. 4 — 1. 0 — — — 1.2 — 0. 7 0. 7 — Lea d i n settle d particulates , mg/m^/mo . stud yperio d averag e 11. 2 6. 7 4. 8 3. 8 2. 8 — 8. 6 11. 6 3. 0 3. 4 —

EASTCHARLESTO N CHARLESTO N CRED E WES TCHARLESTO N NORT H CHARLESTON , EAS T NORT H CHARLESTON . WES T SOUTH CHARLESTON . EAS T SOUTH CHARLESTON , WES T DUNBA R INSTITUT E ST.ALBAN S NITR O WES TO F ST. ALBAN S WES TQ F NITR O Figur e C-1 . Location s o f fixe d samplin g station s i n Kanawh a Rive r Valley. 3 TABL E C-4 . DATA O N LEA D DEPOSITIO N I N 7 7

MIDWESTER N CITIES 4 (mg/m 2/mo ) Lea d depositio n Lea d depositio n Are a Residentia l Commercia l Industria l Concentration ,

geometri c 5.2 4 9.8 0 12.7 8 mea n Mont h

Septembe r Octobe r Novembe r Decembe r Concentration .

geometri cmea n 9.1 1 8.7 1 9.1 5 8.0 6 horse s die do f

lea dpoisonin g tha t

wa s cause db y in

gestio n o f

lea ddeposite do n pastur e gras s fro ma smelte r plan t a t Selby , California . Th e ambien t ai r concentration s o f

particulat e lea dwer e typica l o f thos e foun di n urba n an dsuburba n areas . I t wa s con clude dtha t

horse s i n thi s are ashoul dno t b e allowe d t o subsis t o n pastur e gras s alone , bu t shoul dreceiv e supplementa l feed . Table s C- 5 an dC- 6 contai n th e dat ao n suspende dan ddeposite dlea dobtaine ddur

in g th e study . Not e tha t th e fallou t

rate s ar e o n a dail y basis .

Figur e C-2 . Ai r samplin g site s fo r Souther n Solan o County , California , study. 5 C.2. 2 Omaha , Nebraska 6 I n Apri l an dMa y o f

1968 , astud y o f

settle dlea d b y th e EP A Divisio n o f Healt hEffect s Researc h showe dcentra l Omaha , Nebraska , t o hav e th e high

es t concentration s o f

deposite dlea do f

2 2 mid

wester n cities . Becaus e automobil e emission s shoul d reflec t th e relativel y lo w populatio n density , th e possibilit y o f

asignifican t

contributio n t o ai r

lea d C- 3P.8 7

TABL E C-5 . LEA D CONCENTRATION S I N AI R DETERMINE D B YANALYSI S O F SUSPENDE D PARTICULATE , SOUTHER N SOLAN O COUNTY , CALIFORNIA , MARCH-MA Y1970 s

Sit e Carquine z Bridg e Ellio t Cov e Babso n hous e Braitodum p Wals h hous e Brait o T V transmitte r sit e Wesne rpastur e Wesne rpastur e Wesne rpastur e Gome z pastur e Wesne rhous e Sa n Francisco " Fremont 0 Sa n Rafael " Distanc e fro m Selby, a k m 1. 9 3. 0 3. 7 5. 6 5 7 7. 7 7. 8 8. 0 8. 3 10. 0 10. 2 22. 0 20. 0 19. 2 Lea d concentration !

Hig h 8.4 5 0.9 3 0.8 2 0.6 9 0.6 2 1.0 7 0.5 6 0.6 6 0.5 1 0.2 8 0.2 2 3.5 0 2.2 4 2.04 Lo w 0.35 0.2 7 0.5 8 0.0 7 0.1 4 0.2 5 0.4 0 0.1 1 0.0 3 0.0 3 0.02 1.1 5 0.5 9 0.4 1 ,/xg/m 3

Mea n 3.4 9 0.5 2 0.7 0 0.6 4 0.4 0 0.5 9 0.42 0.3 8 0.2 7 0.1 1 0.1 4 2.1 2 1.0 4 1.1 4 a Locatio n o f suspecte d lea d emission s source . Se e text . D 196 9 dat a provide d byBa yAre a Ai rPollutio n Contro l District . TABL E C-6 . TOTA L LEA D AN D LEA D FALLOU T DETERMINE D B YANALYSI S O F DUSTFAL L SAMPLES , SOUTHER N SOLAN O COUNTY , CALIFORNIA ,

JUNE-SEPTEMBE R 1970 *

Sit e Distanc e fro m Selby. a k m Sampl e

period , day s Tota l solids . m g Tota l lead , n9 Lea d fallout . mg/m 2 -da y Carquine z Bridg e Brait o dum p Brait o T V trans mitte rsit e Wesne r pastur e Wesne r pastur e Wesne r pastur e Wesne r pastur e Wesne r pastur e Wesne r pastur e Wesne r pastur e Wesne r pastur e Gome z pastur e Drachma n pastur e 1. 9 3 0 49. 2 5. 6 3 0 58. 7 7. 7 6 0 101. 7 8. 0 3 1 37 0 8. 0 3 1 16 2 8. 0 3 1 171. 4 8. 0 3 1 109. 8 8. 0 3 1 351. 7 8. 0 3 1 220. 2 8. 0 3 0 83. 5 8. 3 3 0 163. 6 10. 0 3 2 45. 0 13. 4 3 0 26. 5 143 5 19 5 2.7 8 0.3 8 52 0 18 5 15 5 19 5 25 5 21 0 453 5 43 0 70 5 15 0 7 5 0.5 0 0.3 5 0.2 9 0.3 7 0.4 8 0.3 9 8.5 1 0.8 3 1.3 7 0.2 7 0.1 5 

### fro

mothe r source s (tw o battery plants , on e refinery ) i n th e centra l cit

y are awa s considered . Conse

quently , fro

mMa y t o November

1970 , monitorin g o f ai r leadi n Omah awas conducte da t five sites : on e industria l (I) , on e commercial (C) , on e mixe d(M) , an dtw o residentia l (R) . All sample s wer e take n a t 15-f t elevation , an dal l dat awer e reporte da s th e composite daverage s o

f 24-hr sample s collecte d3 time s weekly . Th e monthl y composite averag e o f ai r leadconcentration s a

t th e samplin g site s i s shown i n Figure C-3 . Air

lea dlevel s i n centra l Omah aa

t site s C an dI wer

e no t onl y comparabl e wit

hthos e of simi

la r site s i n Chicago , Ne

w Yor k City , an dHousto n fro mth e sam

e months , a s reporte db

y EPA , bu t

th e maximummonthl y mea

n a t th e industria l site (i

n July ) exceede dth e maximummonthl y mea n o f al l site s i n thes e othe r

cities .

ATMOSPHERI C LEA D - OMAH A

MONTHL YCOMPOSIT E MAY- NOVEMBE R 197 0

RESIDENTIA L

a Locatio n o f suspecte d lea d emission s source . Se e text . MAYJU N JU L AU G SE P OC TNO V TIME , month s Figur e C-3 . Omaha , Nebrask a study : mea n monthl y com posit e atmospheri c lea d a t Industrial , commercial , mixed , an d tw o residentia l sites . Mea n i s tha t o f representativ e 24 - hou r sample s collecte d thre e time s weekly . Th e autumna l pea k a t al l bu t th e industria l sit e parallel s th e usua l Omqh a patter n fo r particulates. 6 

### C.2. 3 El Paso , Texas 7 

### ' 8 

### Th e E l Paso , Texas , study wa s initiate di n 197 1 a s aresul t o f th e discover

y o f increase dleaddepositio n i n th e vicinit

y of alocal smelter

whos e emission s C-4

### ros e fro

m25 6 M T i

n 196 9 t o 46 3 M T i

n 1970 . Th e El Pas o City-County HealthDepartmen t the n bega

n specia l ambien t ai r an dsoil samplin g i

n addition t o routin e operatio n o

f thei r nine-statio n particulat e samplin g network . Particulate ' sample s were col

lecte dwit

hhigh-volum e sampler s ove r 24-h r period s andwere the n analyze dfo r leadb y atomi c absorptio n spectroscopy . Th e result s fo r 197 1 fro m th e nine-statio n networ

k ar e given i

n Tabl e C-7 . Dail y samplin g a

t 6 selecte dsite s i

n Smeltertow n was continue dbeginnin g i n February 1972 . Dail y leadconcentration s a

t fou r groun dlevel site s range d fro m0.4 9 t o 7 5 figlm 3 

### an daverage d6. 6 jixg/m 3 

### over 8 6 days . Averag e concentration s o f 3. 6 and6. 5 /ug/m3 

### were founda

t 2 roofto p sites . TABL E C-7 . LEA D CONCENTRATION S I N SUSPENDE D PARTICULAT E AI R SAMPLE S FRO M E L PASO , TEXAS , 197 V

Locatio n Airpor t Northeas t Canutill o Short yWay Tillma n Yslet a Coronad o Ker n Executiv e Distanc e fro m k m 12. 8 E 1 6 N E 15. 2 N W 8N W 4. 8 S E 21. 6 S E 4. 8 N 2.4 E 1. 6 N E sample s

8 4 73 4 5 75 7 0 7 1 9 4 2 6 6 5 Suspende d atmospheri c

lea d concentratio n Rang e 0.3 8 t o 5.8 2 0.1 2 t o 3.6 8 0.1 0 t o 1.5

0 0.1 8 t o 4.5 1 0.0 2 t o 22.1 6 0.1 8 t o 4.8 1 0.0 8 t o 8.6 2 0.1 2 t o 7.2 8 0.2 6 t o 6.6 7 ./jg/m 3

Averag e 0.9 6 0.7 6 0.4 6 1.0 3 2.6 9 1.3 9 0.8 3 2.7 2 1.1 6 

### C.2. 4 HelenaValley , Montana9 

### Durin g th e summer

andfall o

f 1969 , asource oriente dstudy o

f th e Helen aValley , Montana , are a (Figur e C-4 ) wa s undertake n using dustfal l bucket an dhigh-volum e samplin g techniques . Durin g thi s period , Helen aresident s were expose dt o a n averag e dail y leadconcentratio n o f 0. 1 figlm 3 

### , wit

hmax imu mconcentration s o

f u p t o 0. 7 /ug/m 3



### . Th e resi

dent s o f th e Eas t Helen aare awer

e expose dt o a

n averag e dail y concentratio n o f 0. 4 t o 4. 0 /ug/m 3 

### , de

pendin g upo n proximity t o th e source , wit hmax imu mdail y exposure s of

up t o 1 5 figlm 3



### . Withi n a1

- mil e radiu s o

f th e Eas t Helen asmelter , settle dpar ticulat e leadvalue s range dfro m3 0 t o 10 8 mg/m2



### / mo . Tabl e C- 8 summarize s th e dustfal l an dsus pende dparticulat e dat aacquire ddurin g thi s study , an dFigure C- 4 show s th e depositio n o f lead (dustfall ) i

n th e area .

SCALC . kitamM* ? 

# L

HTTLIAU I ••ARTICULAT

C L f AD . g^>10TO<3 0 1)11 1 >J O T

O < MO Figur e C-4 . Settleabl e particulat e lea d radia l distributio n fro m Helen a Valle y environmenta l pollutio n study. 9 

### C.2. 5 Southeas tMissouri 1 0 

### Studie s wer

e carrie dou t

i n 197 1 i n th e Viburnum ' Tren do r Ne w LeadBelt

i n southeas t

Missouri t o determin e th e magnitud e an ddistributio n o f at mospheri c pollutant s fro

mleadminin g an dsmeltin g operations . Thi s industria l distric t ha s become on e o f th e world' s larges t

lead-producin g area s b

y min

in g more than 392,27 7 M T o f lead , o r 7 5 percen t

o f th e entir e U.S . leadproduction , durin g 1970 . Set

tleabl e particulate s wer

e collecte dmonthl y a

t 1 0 location s i

n wester n Iro n Count

y shown i

n Figure C-5 . Annual average s fo

r eac hsite ar e include di n th e figure ; monthl y maximumvalue s ar e liste di n Tabl e C-9 . Annual average s for suspende dlea dcol

lecte di n Glover , Mo . (Site 43 , southeastern Iro n County) , b

y high-volum e sample r

wer e 3. 4 /ng/m3 

### (2 0 samples ) i

n 1970 , 5. 3 /xg/m3 

### (3 2 samples ) i n 1971 , an d5. 6 Mg/m 3 

### (2 8 samples ) i

n 1972 . TABL E C-8 . PARTICULAT E DAT A SUMMAR YFRO M HELEN A VALLEY , MONT. , ENVIRONMENTA L POLLUTIO N STUDY "

Settleabl e particulat e lead . mg/m 2 /m o Suspende d particulat e lea d i n glas s fibe rfilte rsample , iig/rrfl Statio n 1 2 3 4 6 Location 3

0. 8 mi ; 34 ° 2. 5 mi ; 105 ° 0. 4 mi ; 112 ° 4. 5 mi ; 274 ° 0. 5 mi ; 2 ° Jun . 3 1 54 1 — Jul .

1 9 4 10 6 4 — Aug .

1 0 3 5 3 — Sept .

1 9 9 6 3 7 2 7 Oct .

4 0 1 0 10 8 7 6 0 No . sample s

7 6 8 7 8 5 8 2 3 4 Max .

5. 3 2. 5 16. 0 7. 0 15. 0 Min . < md ° < m d < m d < m d 0. 2 Averag e

0.4 5 0.2 4 1.2 5 0.1 0 3.8 9

a Distanc e an d compas s directio n fro m smelte rstack , b Minimu m detectable . C- 5BUIC KTOWt R # 0« 3

Figur e C-5 . Annua l averag e o f settleabl e particulat e lea d at site s nea r Missour i lea d min e an d smelter , g/m J /Tno. 1 0 

### C.2. 6 Helsinki , Finland "

Investigator s fo r

th e Agricultura l Researc h Center i n Tikkurila , Finland , a

n industria l an dresi

dentia l are anea

r Helsinki , foundhighleadlevel s i n soil . T o clarif

y th e origi n o

f thi s exces s lead , th e In

stitut e o f Occupational Healthconducte dadustfal l leadsurvey i

n th e area . Eight

y collector s were lo

cate dover

a40-km 2 

### are afo

r aperio do

f 1 month , Octobe r 6 t o November

7 , 1970 . Individua l ashe d sample s wer

e analyze db

y emissio n spectrograph y an dth e water-solubl e fraction s were analyze db y atomi c absorptio n spectroscopy . Th e highes t

leaddepositio n value s i n Helsinki wer e observe di

n area s wit

hheavy traffi c an drange d fro m1 0 t o 2 0 mg/m2



### /mo a s compare dt o 0 t o 4 mg/m2 

### /mo i n predominantl y housin g an dresidentia l areas . I n th e Tikkuril aarea , industrial contribution s in

crease ddeposite dlea

dvalue s fortyfol di

n som e areas . Th e deposite dleadvalue s range dfro mback

groun di n outlyin g area s t o a s hig

ha s 20 0 mg/m2



### /mo nea r aleadsmelter , wit

hmos t of th e value s belo w 100mg/m 2

### /mo . C.2. 7 Mez a Rive r Valley , Yugoslavia 1 2 

### I n 1967 , wor

k was initiate di

n th e communit

y o f Zerjav , situate di

n th e Slovenia

n Alp s on th e Mez a TABL E C-9 . PEA K

DEPOSITIO N RATE S O F LEA D MEASURE D I N SOUTHEAS TMISSOURI TM

197 1 Statio n no . Win d

directio n Distance , m Lea d deposi tio n rate , mg/m^/m o Win d frequency , % prevailin g directio n May-Jun e Jul y Augus t Septembe r Octobe r Novembe r 6 7 1 0 7 7 3 E

SS E N E SS E SS E WN W 8 1

9 1 63 3 9 1 9 1 6 1 5.8 8

5.54 4.5 7 7.76 5.1 0 2.0 1 18(S) . 12(WNW ) 14(SSE) , 13(S) . 10(SSW ) 14ISSE) . 1KS) . 10ISSW ) 22IS) . 12ISSE) . 121SSW ) 10(N) . 10(W) . 10ISE) . 1 1 (ESE ) 26(S) . 12ISSW) . 10(WSW).8(SSE ) 

### River , t o investigate contaminatio n b y leado f th e air , water , snow , soil , vegetation , an danimal life , a s well a s th e human population . Th e smelter i n thi s communit y produce s abou t

19,95 4 M T o

f lea dan nually ; unti l 196 9 th e stac k emitte dlea

doxide s withou t contro l b y filter s or

other devices . Fiv e sam plin g site s wit

hhigh-volume sampler s operatin g on a 24-hr basi s wer e establishe di

n th e fou r principal settlement s withi n th e Mez aRiver Valle y (Figur e C-6) : (1 ) Zerjav , i

n th e center , th e site of th e smelter , housin g 150 3 inhabitants ; (2 ) Rudarjevo , abou t 2 k mt o th e sout

ho f Zerjav wit

hapopulatio n of

100 ; (3 ) Crna , som

e 5 k mt o th e southwest , populatio n 2198 , where ther e ar e tw o site s (Crna-S Ean dCrna

W) ; an d(4 ) Mezica , avillag e abou t 1 0 k mt o th e northwes t

o f th e smelter

wit h251 5 inhabitants . Th e dat ai n Tabl e C-1 0 ar e sufficien t t o depic t

general environmenta l contaminatio n of strikin g propor tions . C.2. 8 Ontario,Canada 1 * 

### Studie s o f lea dconcentration s i

n soils , vegetation , an dth e ambient

air wer e conducte di

n th e vicinit

y o f asecondar

y smelter an dabattery manufacturin g plan t i n alarg e urban are ai

n southern Ontario . Fo r comparativ e purposes , dat awer e als o collecte di

n a simila r contro l neighborhoo dthat ha dno suchin

dustria l sources . Emission s o f lea dfro mth e smelter wer e estimate dt o be 1 7 ton s per year ; fro mth e bat

ter y plant , 6 ton s pe

r year . Average s an drange s o f C- 6flIVERS rrfflflp SETTLEMENT

S Figur e C-6 . Schemati cpla n o f lea d min e an d smelte rfro m Mez a Valley , Yugoslavia , study. 1 2 TABL E C-10 . ATMOSPHERI C LEA D CONCENTRATION S (24 - hr ) I N TH E MEZ A VALLEY , YUGOSLAVIA , NOVEMBE R 197 1

T O AUGUS T1972 1 2 Sit e Mezic a Zerja v Rudarjev o CrnaS E Crna W Minimu m 0. 1 0. 3 0. 5 0. 1 0. 1 P b concentratio n jjg/m ^

Maximu m 236. 0 216. 5 328. 0 258. 5 222. 0 Averag e

24. 2 29. 5 38. 4 33. 7 28. 4 lea dconcentration s ar e summarize din Tabl e C-11 . Bot hsoi l an dfoliag e sample s showe ddefinit e trend s towar dreduce dconcentration s withincreasin g dis

tanc e fro mth e industria l sources . C. 3 CONCENTRATION S O F LEA D I N SOIL S AN D URBA N DUST S A s mentione din Chapte r 5 , surficia l material s in th e continenta l Unite dState s contai n a n averag e o f abou t 1 5 pp mo f

lead ; 9 4 percen t

o f th e measure ment s showe d3 0 pp mo r less . Highe r

concentration s ar e encountere din th e vicinit y o f lea dor e deposit s and , o f course , in th e proximit y o f huma n activitie s involvin g lead . Soil s apparentl y receiv e lea din th e amount s o f

abou t 1 figlcm 2

/yr fro mprecipitatio n an d0. 2 /ig/cm 2 /y r

fro mdustfall 1 4 i n area s remot e fro mintensiv e huma n activity . Thes e smal l addi

tion s t o th e lea dconten t o f th e soi l ar e no t

detectabl e b y ordinar y mean s becaus e the y ad donl y abou t 0. 2 percen t t o th e tota l lea din th e to p 6 in o f th e soil . Lea dlevel s ar e highe r

i n surfac e soil s tha n in deepe r layers . Swai n an dMitchell 1 5 studie dlea dprofile s i n 8 soi l type s in Scotlan dan dshowe dtha t th e lea d conten t a t 11 5 c m(4 5 in ) average done-hal f tha t at th e surface . Th e reductio n o f concentratio n with dept hi s als o substantiate db y th e finding s o f others . Goldschmidt 1 6 propose dth e theor y tha t lea di s con centrate din th e humu s o r organi c fractio n o f

soil s i n forest s becaus e i

t i s take n u p slowl y b y tre e root s an d transporte dt o th e leaves , whic hfal l an ddecay . Tyler 1 7 point s ou t

tha t apassiv e io n exchang e favor s a n accumulatio n o f

lea dan dothe r

heav y metal s in dea dorgani c matter , litter , an dhumus . H e als o state s tha t

mos t plan t materia l subjecte dt o decom

positio n usuall y show s an increas e in th e concentra tio n o f lead , cadmium , nickel , iron , copper , etc. , calculate do n dr y weight . Th e us e o f

leade dgasoline s ha s produce delevate d soi l lea dlevel s adjacen t t o mos t street s an droad

ways . Thi s phenomeno n wa s firs t observe da s earl y a s 193 3 in England, 1 8 an dha s bee n intensivel y TABL E C-11 . COMPARISO N O F LEA D LEVEL S I N TH E SURROUNDING S O F TW O

LEA D INDUSTR YFACILITIE S AN D A N URBA N CONTRO L AREA " Industr yo r are a Secondar ysmelte r Mea n Rang e Batter yplan t Mea n Rang e Urba n contro l are a Mea n Rang e Soil , pp m (0. 5 c m depth ! 2.61 5 13 3 t o 21.20 0 1.99 6 9 5 t o 17.30 0 48 2 1 8 t o 1.45 0 Tre e foliag e pp m Unwashe d 25 0 3 8 t o 3.53 0 14 9 3 4 t o 45 9 7 3 1 5 t o 25 3 Washe d 18 7 2 7 t o 2.74 0 7 6 1 6 t o 38 7 4 3 10»o12 4 Air , /ig/m ^ (24-hou rsamples ) 3.87 * Max 1 74. 4 2.21 ° Max-31.0 . 1.02 c Max : 4. 0

a Apri l 197 3 t o Ma y1974 . b Novembe r197 3 t o Ma y1974 . c Januar y1974 t o Apri l 1974 . C- 7P.9 1

studie di n recen t

years. 1 9 A n exampl e o f thi s phenomeno n i s take n fro mastud y o f th e Salin e Branc hwatershed , whic hinclude s Champaign , Il

linois . On e face t

o f thi s comprehensiv e study 2 0 con siste do f analyse s fo r

lea di n soi l a t

increasin g dis

tance s fro malow-traffic-volum e stree t (40 0 vehi

cles/day ) an dahigh-traffic-volum e stree t (14,00 0 vehicles/day) . A s show n o n curv e A i n Figur e C-7 , lea dconcentration s stabilize dat abou t 2 0 pp m beyon d1 5 meter s fro mth e low-volum e stree t an d ros e slightl y nea r

th e house . Unfortunately , th e ex terio r constructio n o f

th e hous e i s no t

described . A s curv e B i n Figur e C- 7 shows , lea dconcentration s o f abou t 180 0 pp mi n th e soi l adjacen t t o th e high

volum e stree t

ar e 9 time s highe r

tha n in soi l adjacen t t o th e low-volum e street ; th e concentratio n drop s rapidl y t o aminimu mo f 3 0 pp malittl e mor e tha n 2 0 mfro mth e stree t

an dthe n rise s agai n abruptl y nea r th e hous e t o 9 0 ppm . Thi s hous e i s describe da s bric k an dunguttered . Althoug hsom e leachin g o f lea dfro mpainte dtri mmay b e involved , th e increas e nea r th e hous e i s believe dattributabl e chiefl y t o lea d particle s in traffi c dus t

washe dfro mth e unguttere d roo f b y rai n an ddeposite din th e soi l nex t t o th e house . E 100 0 — a o .

_ • 20 0

DISTANC E FRO M STREET , meter s Figur e C-7 . Soi l transect s b y tw o streets : Curv e A = lowtraffic-volum e (40 0 veh/day) ; Curv e B = high-traffic-volum e (14,00 0 veh/day). 2 0 Soi l lea dlevel s in th e vicinit y o f stationar y source s o f lea demission s ar e ofte n ver y high , and . unlik e th e rapi ddrop-of

f nea r highways , ver y extensive . Thi s i s particularl y tru e fo r

ol dinstallations . Figur e C- 8 show s level s recentl y foun dnea r an ol dsmelte r

in E l Paso , Texas. 2 1 Simila r

data , compile dfro ma3-year

ol dRussia n lea dsmelter, 2 2 ar e show n i n Tabl e C-12 . Th e concentratio n decreas e withbot h dept han ddistanc e i s als o apparen t here . Informa

tio n o n solubl e lea dlevel s in soi l nea r asimila r com ple x i n Grea t

Britia n i s presente din arepor t b y Lit

tl e an dMartin. 2 3 Barltro p reporte dvalue s u p t o 30,00 0 ,u.g/

g in village s i n th e easter n hal f o f Der

byshir e County , England. 2 4 I n thi s instance , th e soi l include dlea dcontaminatio n fro mol dmin e tailing s an dpossibl e natura l mineralization , i.e. , th e con centration s wer e no t

exclusivel y atmospheri c in origin .

DON * ANACOU N

UMTE D STATU !

Figur e C-8 . Surfac e soi l level s (ppm ) o f lea d i n E l Paso , Texas , an d Don a An a County , Ne wMexico , 1972.2 1 TABL E C-12 . LEA D CONTEN TO F SOI L NEA R 3-YEAR-OL D

RUSSIA N SMELTER , E . KAZAKHSTA N (mg/10 0 g air-drie d soil) a Distanc e tro m Surfac e Soi l dept h source , m 50 0 1.000 2.00 0 3.00 0 5.00 0 16.00 0 laye r

23.971 1 9.016 3 1.4207 1.219 2 0.103 1 0.094 3 2 5 c m

4.174 7 1.8368 0.7432 0.599 1 0.064 9 0.077 8 7 5 t o 10 0 c m

0.074 8 — 0.054 5 0.0474 0.023 3 0.029 2 Multiplyin g by1 0 yield s ppm . Tabl e C-13 , derive dfro mstudie s don e in 195 9 an dI960, 2 5 give s lea dlevel s o f soi l adjacen t

t o anothe r Russia n lea dsmelter . Th e plan t i s locate din avalle y surrounde db y mountain s tha t hinde r natura l ventilation . I n addition , plan t emission s ar e inadequatel y controlled . Method s o f sampl e prep aratio n an danalysi s o f th e soi l sample s ar e no t given , however ; no r

i s it state dwhethe r

th e soi l weight s use dwer e fo r

drie do r

undrie dmaterial . Paluc han dKarweta 2 6 reporte dobservation s o n soi l lea dnea r

ane w lead-zin c primar y smelte r in Po

land . Soi l analyse s wer e mad e in severa l area s prio r t o operatio n o f

th e factor y an dafte r

1 yea r o f opera tion . Sample s wer e extracte dwit hho t concentrate d hydrochlori c aci dan danalyze dfo r lea dconten t

b y th e dithizon e method . Level s foun dar e give n in milligram s o f

lea dpe r kilogra mo f

drie dsoil . Value s C- 8TABL E C-13 . LEA D CONTEN TO F SOI L I N VICINIT YO F RUSSIA N LEA D PLAN TI N KAZAKHSTAN' S

fro m k m O n ground s 0. 5 1. 0 1. 5 2. 0 3. 0 5. 0 40. 0 Numbe r

o f sample s 1 2 1 0 2 0 6 6 4 4 4 Maximu m 11.170. 0 2.420. 0 1:170. 0 720. 0 1.070. 0 340. 0 97. 0 3. 0 0 t o 1 c m dept h

Minimu m 1.300. 0 470. 0 130. 0 170. 0 250. 0 130. 0 80. 0 2. 5 Lea d conten t o t so i

Averag e 5.546. 0 1.156. 0 613. 0 369. 0 530. 0 235. 0 88. 5 2. 7 , mg/10 0 g a

Maximu m 6.800. 0 650. 0 990. 0 720. 0 610. 0 260. 0 46. 0 Trac e 2 5 c m dept h

Minimu m 510. 0 130. 0 200. 0 70: 0 70. 0 100. 0 40. 0 Trac e Averag e

3.143. 0 458. 0 430. 0 340. 0 260. 0 180. 0 43. 0 Trac e Multiplyin g b y1 0 yield s ppm . give n ar e th e averag e o f thre e samples . Tw o site s ar e o f particula r

interest , awood s o f

youn g pine s 2 k

m fro mth e smelte r

an datre e nurser y a t

3 km . Befor e an dafte r lea dlevel s in th e to p 5 c mo f soi l a t thes e location s wer e 3 9 an d8 9 mg/k g fo r th e former , an d 5 4 an d8 1 mg/k g for

th e latter . A t

othe r samplin g site s th e dat awer e quit e variable , bu t thes e wer e agricultura l land s subjec t t o cultivation , t o fertiliza

tion , o r t o both . Th e woode dsite s wer e no t disturbe d in thi s manner . C. 4 REFERENCE S FO RAPPENDI X C 1 . Tepper , L . B . an dL . S . Levin . A surve y o f ai r an dpopula

tio n lea dlevel s i

n selecte damerica n communities . Pre

pare dby Universit y o f

Cincinnati , Cincinnati , Ohio , unde r Contrac t No . PH-22-68-28 . U . S . Environmenta l Protec

tio n Agency . Washington , D.C . Publicatio n No . EPA

RI-73-005 . 1973 . 2 . Hauser , T . R. , J . J . Henderson , an dF . B . Benson . Th e polynuclea r

hydrocarbo n an dmeta l concentratio n o f th e ai r ove r th e Greate r

Birmingha mArea . Huma n Studie s Laboratory , U . S . Environmenta l Protectio n Agency . Researc hTriangl e Park , N.C . Unpublishe dReport . 3 . Kanawh aValle y Ai r Pollutio n Study . U.S . Environmenta l Protectio n Agency . Researc hTriangl e Park . N.C . Publica

tio n No . APTD-70-l . Marc h1970 . 4 . Hunt , W . F. , C . Pinkerton , O . McNulty , an dJ . Creason . A stud y i n trac e elemen t

pollutio n o f

ai r i n 7 7 midwester n cities . In: Trac e Substance s i n Environmenta l Health . IV . D . P . Hemphil l (ed.) . Columbia , Universit y o f Missour i Press . 1971 . p . 56-58 . 5 . Maga . J.A. . F.B . Hodges , C.B . Christenson , an dD.J . Callaghan . A Join t

Stud y o f Lea dContaminatio n Relativ e t o Hors e Death s i n Souther n Solan o County . Lo s Angeles . Stat e o f Californi aAi r

Resource s Board . Septembe r 1972 . 17 8 p . 6 . Mclntire , M . S . an dC . R . Angle . Ai r lead : Relatio n t o lea d i n bloo do f

blac k schoo l childre n deficien t i n glucose-6

- phosphat e dehydrogenase . Science . / 77.520-522 , Augus t 1972 . 7 . Henderson , J . J . an dP . A . Hudson . Unpublishe dtri p repor t re : th e Cit y o f

El Pas o an dStat e o f Texa s (Ai r

Contro l Board ) vs . America n Smeltin g an dRefinin g Compan y (ASARCO) , Caus e No . 70-1701 . Ai r Qualit y Enforcemen t Office , EP A Regio n VI . Dallas , Texas . Ma y 12 , 1972 . 8 . Shearer , S . D . an dJ . J . Henderson . E l PasoSmelte r Briefin g Paper . Environmenta l Monitorin g an dSuppor t Laboratory , U.S . Environmenta l Protectio n Agency . Researc hTriangl e Park , N.C . Ma y 1972 . 9 . Helen aValley , Montana , Are aEnvironmenta l Pollutio n Study . U.S . Environmenta l Protectio n Agency . Researc h Triangl e Park , N.C . Publicatio n AP-91 . Januar y 1972 . 10 . Purushothaman , K . Ai r Qualit y Studie s o f

aDevelopin g Lea dSmelte r

Industry . Rolla . Universit y o f Missour i Press . 1972 . 1 3 p . 11 . Laamanen , A . an dA . Ryhanen . Aeria l distributio n o f dustfal l lea di

n th e neighborhoo do f som e lea demitters . Suome n Kemistilehti . (Helsinki) . 44:367-371 , 1971 . 12 . Fugas , M. , D . Majic , R . Paukovic , B . Wilder , an dZ . Skaric . Biologica l Significanc e o f Som e Metal s a s Ai r

Pollutants . Fina l Report . Par t

I : Lead . U . S . Departmen t o f Health , Education , an dWelfare , Consume r Protectio n an dEnviron

menta l Healt hService . Washington , D.C . Januar y 1974 . Linzon , S . N. , B . L . Chai , P . J . Temple , R . G . Pearson , an d M . L . Smith . Lea dcontaminatio n o f urba n soil s an dvegeta tio n b y emission s fro msecondar y lea dindustries . J . Ai r Pollut . Contro l Assoc . 26(7) : 650-654 , 1976 . Lead : Airborn e Lea di

n Perspective . Washington , D.C,Na

tiona l Academ y o f

Sciences . 1972 . p . 28 . 15 . Swaine , D . J . an dR . L . Mitchell . Trac e elemen t distributio n i n soi l profiles . J . Soi l Sci . //(2):347-368 , 1960 . Goldschmidt , V . M . Th e principle s o f distributio n o f

chemi

ca l element s in mineral s an drocks . J . Chem . Soc . (London. ) 655-673 . 1937 . 1 3

14 .

1 6

I 7 . Tyler . G . Heav y metal s pollut e nature , may reduc e produc

tivity . Ambio . /(2):52-59 , 1972 . 18 . Dunn , J . T . an dH . C . L . Bloxam . Th e occurrenc e o f lead , copper , zinc , an darseni c compound s i n atmospheri c dusts , an dth e source s o f

thes e impurities . J . Soc . Chem . Ind . Lon

do n Trans . Commun . 52.189-192 . 1933 . 19 . Smith , W . H . Lea dcontaminatio n o f th e roadsid e ecosystem . J . Ai r Pollut . Contro l Assoc . 26(8):753-770 , 1976 . 20 . Rolfe , G . L . an dA . Haney . An Ecosyste mAnalysi s o f En

vironmenta l Contaminatio n by Lead . Institut e fo r Environ

menta l Studies , Universit y o f Illinoi s at

Urbana-Champaign . Researc hRepor t

No . I . Augus t

1975 . p . 53-56 . 21 . Huma n Lea dAbsorptio n - Texas . U.S . Departmen t o f Health , Education , an dWelfare . Atlanta , Georgia . Mor

bidit y an dMortalit y Weekl y Report . 22(49):405-407 , 1973 . C- 9P.9 3

22 . Pakhotina , N.S . Sanitar y hygieni c evaluatio n o f industria l emission s b y azinc-lea dcombine . In: Surve y o f USS R Literatur e o n Ai r

Pollutio n an dRelate dOccupationa l Dis

eases . U . S . Publi c Healt hService . Washington , D.C . J.-93-97 , I960 . 23 . Little , P . an dM . H . Martin . A surve y o f zinc , lea dan dcad

miu mi n soi l an dnatura l vegetatio n aroun dasmeltin g com plex . Environ . Pollut . 5:241-254 , Jul y 1972 . 24 . Barltrop , D . Significanc e o f lead-contaminate dsoil s an d 25 . 2 6 dust s fo r

huma n populations . Arh . Hig . Rad aToksikol . (Yugoslavia. ) 26:81-93 , 1975 . Smokotnina , T . N . Hygieni c evaluatio n o f ai r pollutio n wit h waste s fro malea dplant . Hig . Sanit . (USSR) . 27(6):87-90 , 1962 . Paluch ; J . an dS . Karweta . Th e accumulatio n o f zin c an d lea di n soi l an dplants . In: Lecture s o f 6t hInt' l Congres s o f Forestr y Specialist s fo r

Smok e Damage . Katowice . (Poland. ) 1968 . p . 127-138 .



### C-1 0P.9 4



## APPENDI X D UNIT S AN D METRI C CONVERSIO N FACTOR S

I n eac ho f

th e discipline s dealin g withlea din a secto r o f th e environment , convention s fo r unit s hav e evolve dtha t

ar e convenien t

t o eac hbu t

no t al

way s familiarl y translatabl e fro mon e t o th e other , eve n whe n expresse din metri c units . Ther e ar e als o tw o distinc t

categorie s o f

measurements : concentra tion s an dtransfe r

rates . Withi n eac hcategor y o f measurements , straightforwar dconversio n factor s translat e th e quantitite s fro mon e syste mo f unit s t o another . Connection s betwee n th e tw o categorie s ar e bridge donl y b y mathematica l model s o f varyin g complexit y tha t

accoun t fo r al l significan t

transfe r rates , bot hint o an dou t o f agive n context , a s wel l a s measur e tha t

context' s capacit y t o distribut e an d equilibrat e an y ne t

chang e tha t

will ad dt o o r substrac t fro mit s initia l concentration .

D. l CONCENTRATION S Airborn e lea dconcentration s ar e customaril y re porte din unit s o f

mas s pe r

volume : microgram s o f lea dpe r cubi c mete r

o f ai r (fig/m 3 ). Concentration s o f lea di n soil s an ddust s ar e reporte din unit s o f mas s pe r mass : microgram s o f

lea dpe r gra mo f th e paren t materia l (figlg), o r

a s part s pe r

millio n (ppm) . Whe n pp mrefer s t o mass , th e expressio n i s interchangeabl e wit hfiglg. Concentration s o f

lea din wate r

(dissolve do r

sus pended ) ma y b e reporte din part s pe r billio n (ppb ) o r microgram s pe r

lite r (/xg/liter) . Fo r

ou r purposes , alite r o f wate r ca n b e equate dwit hlOOOg , an dunit s o f jag/lite r

ca n b e interchange dwit hpp b o r nanogram s pe r

gra m(ng/g) . Concentration s o f

lea di n foo dar e usuall y give n in part s pe r

millio n (ppm) , microgram s pe r gra m (figlg). o r

milligram s pe r

kilogra m(mg/kg) , al l o f whic har e interchangeable . Concentration s o f

lea di n bloo dma y b e reporte d i n microgram s pe r

decilite r

(figldl) o r

i n microgram s pe r

100 gram s (figll 00 g) . Thes e ar e no t equivalen t

sinc e 1 d l o f

bloo dweigh s betwee n 10 5 an d10 6 g . D. 2 TRANSFE RRATE S I n general , transfe r

rate s describ e th e movemen t o f materia l fro mon e mediu mo r contex t t o anothe r in unit s o f

mas s pe r

tim e o r mas s pe r

quantit y (mas s o r volume ) o f

aparen t material . Som e rate s includ e alinea r o r are adimensio n t o expres s th e transfe r pe r uni t o f interfac e betwee n media . Th e lea din ore s tha t

i s transfere dt o smelter s an d henc e t o manufacture dproduct s i s describe db y pro ductio n figure s an dreporte din ton s (short ) pe r yea r (tons/yr ) o r

tonne s (metric ) pe r

yea r (MT/yr) . Th e attendan t dispersa l o f

som e o f tha t lea dint o th e air , water , an dsoi l i s describe db y emissio n factors : ton s pe r yea r (tons/yr) , kilogram s pe r da y (kg/day) , pound s pe r

to n o f ra w materia l o r

produc t (lb/ton) , pound s pe r

thousan dgallon s (lb/10 3 gal) , gram s pe r kilomete r

(g/km) , etc . Th e mos t

familia r transfe r rat e betwee n medi ai s perhap s th e dustfal l o r depositio n rate , reporte din ton s pe r

squar e mil e pe r

yea r (tons/mi 2 /yr) , milligram s pe r

squar e mete r

pe r mont h(mg/m 2 /mo) , etc . Th e culminatin g concer n i s wit htransfe r rates , in

volvin g th e huma n body , throug hinhalatio n an din

gestio n followe db y retentio n an dabsorptio n int o fluid s an dtissues , and , finally , excretion , al l o f whic har e commonl y expresse di n microgram s pe r day , microgram s pe r

kilogra mo f

bod y weigh t

pe r day , or , even , a s microgram s pe r squar e mete r

o f bod y surface . D- lP.9 5



### D. 3 UNIT S D. 4 CONCENTRATIO N CONVERSIO N FACTOR S 1 m = lOV m = 10 2 c m = 10" 3 k m = 3.28 1 f t = 

### 39.3 7 j n

### 1 PP b (mass ) = 1 ng/

g = Ifiglkg 1 pp m(mass ) = 1 figlg = 1 mg/k g 1 m 2 

### = 10 4 

### cm 2 

### = 10- 6 

### km 2 

### = 10.7 6 ft 2 

### = ] mg/lite r (water ) » 1 ppm» I

figlg 155 0 in 2 

### 1 M 

### g/lite r (water ) *£

* 1 pp b lm 3 

### = 10 6 

### cm 3 

### = 999.9 7 liter s = 35.3 1 ft3 

### = ' ^8 / d l

### (blood ) « 0.9 5 fig/l 00 g (blood ) 6. 1 x 104 

### in 3 

### = 264. 2 ga

l D. 5 TRANSFE RRAT ECONVERSIO N l g = 10 * ug = 10 3 

### mg = 10 3 

### kg = 0.03 5 o z = FACTOR S 0 002 2 1 b 1 mg/m 2 

### /mo = 2.85x10- 3 

### ton s (short)/mr 2 

### /m o 1 tonne/y r - 2.7 4 kg/da

y = 1 tonn e (metric ) = 1000 k g = 10 6 

### g = 1.102 3 ton s (short )/y r 1.102 3 ton s (short ) 1 fig/day = 3.5 3 x 10 8 

### o z (av.)/day

D- 2P.9 6



## APPENDI X E ABSTRAC T O F A REVIE W O F THRE E STUDIE S O N TH E EFFECT S O F LEA D SMELTE R EMISSION S I N E L PASO , TEXA S

Presente d b y Warre n R . IVlui r Counci l o n Environmenta l Qualit y Washington , D.C . A tth e Internationa l Conferenc e o n Heav y Metal s i n th e Environmen t Toronto , Ontario , Canad a Octobe r197 5 Th e committe e reviewe dtw o independen t studie s conducte din 197 3 b y Dr . Landriga n (CDC ) an dDr . McNei l (ILZRO ) t o determin e th e effect s o f communit y lea dexposure s nea r th e ASARC O smelte r i n E l Paso , Texas . Th e CD C stud y use darando msampl e approac ht o grou p participatin g children , an din th e ILZR O stud y matc hpaire dgroup s wer e selecte do n th e basi s o f residence . I n bot hstudie s th e criteri afo r subclassificatio n withregar dt o lea dexposur e wer e bloo dlea dlevels . Neuropsychologica l dysfunctio n wa s evaluate db y severa l test s includin g WISC , WPPSI , an dMcCarth y scales . Statistica l difference s in tes t result s coul dno t

b e directl y correlate dt o bloo dlea dlevels . Th e opinio n o f

th e committe e wa s tha t n o firmconclusion s coul db e draw n fro mth e studie s a s t o whethe r o r no t ther e ar e subclinica l effect s o f lea do n childre n in E l Pas o an dtha t th e report s an ddat amad e availabl e hav e no t clearl y demonstrate dan y psychologi c o r neurologi c effect s i n th e childre n unde r study . I t note dth e absenc e o f

majo r chroni c clinica l effects , an dconclude dtha t thes e studie s therefor e d o no t bea r upo n th e con clusion s o f

othe r investigation s unde r

differen t condition s an dthos e in whic hclinica l effect s hav e bee n con firmed. However , becaus e o f inheren t problem s o f

stud y desig n an dth e limitation s in th e test s used , thi s findin g shoul dno t

lea dt o aconclusio n tha t lo w level s o f

lea dhav e n o effect s o n neuropsychologica l performance . Elle n Silbergeld , Ph.D. , NIH , Eilee n Higham , Ph.D. , an dMr . Russel l Jobaris , John s Hopkin s University , Departmen t

o f Medica l Psychology , serve da s specia l consultants . Th e committe e decide dt o limi t it s focu s t o arevie w o f th e thre e studies , an dt o attemp t t o accoun t

fo r an d interpre t th e difference s betwee n th e studies . Thus , aspect s no t relate dt o difference s wer e no t emphasized . Th e committe e limite dit s consideratio n t o th e followin g materials : (1 ) report s o f th e thre e studie s unde r consideration ; (2 ) othe r material s provide db y th e author s o f th e studies ; (3 ) backgroun dinformatio n an d document s collecte db y Dr . Mui r i n E l Paso . Thi s presentatio n toda y consist s o f excerpt s fro madraf

t com mitte e report . E l HISTOR Y E l Pas o i s situate do n th e Mexica n borde r in th e wester n par t

o f Texas . A lea dsmelte r

owne db y America n Smeltin g an dRefinin g Compan y (ASARCO ) ha s bee n locate do n th e southwester n borde r o f th e city , o n th e Ri o Grand e River , sinc e 1887 . Th e are amos t conspicuousl y involve di n th e studies , Smeltertown , wa s a2 x 6 bloc k are alocate dbetwee n th e plan t an dth e river . Smeltertow n i s n o longe r in existence , havin g bee n destroye di n Decembe r 1972 . Abou t

2 k msout ho f

Smeltertow n i s Ol dFor t Bliss , aconsiderabl y smalle r community , whos e inhabitant s wer e considere din some , bu t no t all , o f th e studies . Th e ASARC O smelte r

produce s lead , zinc , copper , an dcadmium . Particulat e matte r i s remove dfro mair

born e waste s in aserie s o f baghouses ; remainin g emission s contai n approximatel y 4 0 l b o f lea dpe r day . Th e E l Pas o Cit y Count y Healt hDepartmen t bega n an investigatio n o f th e ASARC O smelte r

in earl y 1970 , i n preparatio n fo r

an ai r pollutio n sui t

filedb y th e cit y in Apri l 1970 . A s par t o f thi s investigation , Dr . E- lP.9 7



### BertramCarno w was hire db y th e cit y as aconsultant . A

t hi s suggestion , th e cit

y bega n t o sampl e th e bloo d lea dlevel s of

El Pas o childre n t o determin e whether an y hadbeen over-expose dt o lead . Thi s include dalarg e number o f Smeltertow n children . Basedupo n earl y result s i n 1971 , Dr . Carno w visite dE l Paso , an dsa

w a selecte dgrou p o

f childre n wit

hhig hbloo dleadlevels . H e interviewe dth e children , andreviewe dthei r medi

cal records . Th e informatio n containe di n th e medical histories , andDr . Carnow' s interviews , constitut e th e observation s reporte db

y Dr . Carno w i

n th e pape r

presente dt o th e American Pollutio n Contro l Associatio n (APCA). Th e clinical observation s were i n aparagrap ho

f apape r otherwis e devote dt o aconsideratio n o f th e effects o f th e smelter

o n th e environmen t

a s awhole , andth e exten t o f it s emissions . Thi s report contain s n o detail s on th e age , exposures , individua l sign s an dsymptoms , or diagnosti c criteri ause di n th e ten case s re ported . Our

committe e focusedit s attention , therefore , upo n th e tw o full-scal e follow-up epidemiological studie s conducte db

y Dr . Landrigan (CDC ) andDr . McNei l (ILZRO) . In 197 3 ASARC O bega

n aseparat e investigatio n of th e populatio n o

f Smeltertown , an daske dDr . Jame s McNei l o f th e Internationa l LeadZin c Researc hOrganizatio n (ILZRO ) fo r hi s assistanc e i

n th e examinatio n an dpossibl e treatmen t

o f childre n wit

helevate dbloo dlevel s greate r than 6 0 mg/10 0 ml . A s aresul t

of publi c concern ove r

widesprea dleadpoisonin g throughou t th e cit y of El Paso , th e mayo r

re queste dai dfro

mth e Federal Government . A separat e protoco l fo r aCenter fo r Diseas e Contro l (CDC ) study wa s submitte dt o an dapprove db y th e Publi c HealthBoardi n 197 3 wit

hth e understandin g that

th e tw o studie s woul dprocee dindependently , wit hthos e childre n i

n th e ILZR O sponsore dstudy bein g exclude d fro mth e CD C study . In th e summer

o f 1973 , CD C an dILZR O proceede dindependentl y t o collec t dat afo r thei r respectiv e studies . CDC' s examination s wer e don e i n tw o weeks i

n Jun e 1973 , whil e McNeil' s wer e carrie dou t

over th e cours e of th e summe

r wit hth e ai do

f th e El Pas o publi c schoo l system . Th e CD C grou p supplie dt o th e Committe e dat ai n detail , whichwer

e sufficien t t o allo w th e committe e t o conduc t statistical test s an danalyz e characteristic s o f groups . For

th e ILZR O study , thi s committe e requeste d dat asufficien

t t o carry ou t

simila r in-dept hanalyses . Al l of

th e requeste ddat awere supplied ; however , the y wer e no t i n suc hafor ma s t o allo w recalculatio n o f mos t o f th e statistical finding s o

f th e study o r

t o allo w compariso n wit

hth e CD C findings . E. 2 STUD Y DESIGN Th e environmenta l samplin g tha t wa s performe dwas commo n fo r bot ho f thes e studies . I

n th e selectio n o

f study an dcontro l populations , th e Landrigan CD C study usedaclassical approac hof arando msampl e survey t o determin e th e prevalenc e o f abnorma l bloo dleadvalues . Th e 1 3 censu s tract s mos t adjacent t o th e smelter wer e divide dinto thre e areas . Th e samplin g fram e was designe dt o obtai n abou t 100 study subject s fromeac hare afor

variou s ag e groups . O

f 83 3 occupie dresidences , interview s were obtaine dfro m75 8 study subject s i n th e 1-1 9 ag e group . Th e participatin g childre n were divide dint o alead-absorptio n grou p (40-8 0 figllOO ml ) o

f 4 6 andacontro l grou p ( < 4 0 /xg/10 0 ml ) o f 78 . Ther e i s n o detaile ddescriptio n a s t o how th e childre n wer

e chosen . CD C usedthes e same childre n a s th e basi s fo r th e late r study o f neuropsychological dysfunction . All bu t 3 childre n chosen fo

r study came fro

mth e 197 2 prevalenc e survey ; 5 childre n wit hknown preexistin g defect s sucha s wit

hahistory o

f symptom s compatibl e wit hacute leadpoisonin g or acute leadencephalopath y an d thos e who hadreceive dchelatio n therap y wer e excluded . Whil e i t i s understoo dthat

anumber

o f Smeltertow n childre n wit hbloo dleadlevel s over

4 0 /i.g/10 0 m

l wer e eventuall y involve di

n litigation , mos t

o f themtoo k

part i n th e studies . However , on th e recommenda

tio n of th e lawyer s representin g th e children , at leas t on e grou p o

f 1 8 di dno t

participat e i

n th e ILZR O study . In th e absenc e o

f identificatio n b

y name s o

f th e individual s i

n th e thre e studies , i

t ha s been impossibl e t o evaluat e th e effects o

f non-participation . Th e ILZR O study wa s ver y different ; 13 8 childre n fro mSmeltertow n agree dt o participat e i n astudy . Resi

dence , no t bloo dlead , wa s th e selectio n criterion . Tw o contro l group s were chosen , an dwer e reporte dt o hav e been matche do

n age , sex , ethni c background , an dincome , wit hon e se t chosen fro

mE l Pas o an danothe r

se t for thos e 8 year s o

f ag e o r unde r fro marura l are aabou t

1 2 mile s fro

mth e smelter . Thi s classificatio n hadth e effec t of groupin g togethe r

childre n who , under

th e CD C criteria , woul dhav e been i n "lead " an d"control " groups . E- 2Th e criteri ause dfo r subclassificatio n o f

childre n wit hregar dt o lea dexposur e wer e base din bot hstudie s o n th e bloo dlea dlevel . Wherea s th e CD C stud y utilize dbloo dlea dvalue s obtaine da t onl y tw o point s i n time , ILZRO , whic hwa s face dwit hth e proble mtha t man y childre n ha drepeate dbloo dlea dmeasurement s wit hmarke dvariation s ove r aperio do f

1 8 month s (th e level s bein g generall y lowe r afte r exposur e wa s dis

continued) , classifie dchildre n o n th e basi s o f th e averag e o f

th e "tw o highest " recorde dvalues . Thi s criterio n result s in asubstantia l increas e in th e numbe r o f childre n i n th e apparentl y highe r bloo dlea d categor y an dacorrespondin g decreas e i n th e numbe r o f thos e i n th e apparentl y lowe r bloo dlea dleve l category . Althoug hi t

i s understandabl e tha t

thi s typ e o f

selectio n wa s use dt o avoi dunderestimatin g th e proble mo f lea dintoxicatio n in th e populatio n examined , i t ultimatel y resulte din muddlin g o f th e separatio n betwee n group s (an dpossibl y obscurin g eventua l differences) . Fo r example , th e selectio n fo r analysi s o f

childre n fro m th e sam e geographica l area , subclassifie daccordin g t o bloo dlea dlevel , in th e ILZR O study , ma y giv e th e im

pressio n tha t

th e effect s o f

lea ditsel f

ar e bein g studie din ahomogeneou s population . However , sinc e ex posur e wa s geographicall y th e same , othe r factor s inheren t

t o eac hindividua l chil dma y b e responsibl e fo r th e differenc e i n bloo dlea dleve l observed . A n additiona l metho do f classificatio n coul dhav e bee n th e us e o f fre e erythrocyti c protoporphyri n measurement s (FEP ) whic hhav e bee n show n t o provid e a n indicatio n o f metaboli c effect s o f

lea dabsorptio n o n metabolism , particularl y usefu l in bloo dlea dleve l range s (40-6 0 figllOO ml ) wher e analytica l an d biologica l fluctuatio n ma y resul t i n uncertai n classification . (Th e ILZR O stud y include dthi s tes t bu t di dno t includ e i t

a s abasi s fo r

dat aanalysis. ) Absenc e o f elevatio n o f

fre e erythrocyti c protoporphyri n ma y indicat e thos e instance s wher e hig hbloo dlea dlevel s wer e spurious . Th e followin g psychometri c test s wer e employe db y th e tw o studies : 1 . Wechsle r

Intelligenc e Scal e fo r

Children , WIS C (CDC , ILZRO ) 2 . McCarth y Scale s o f

Children' s Abilitie s (ILZRO ) 3 . Wechsle r

Preschoo l an dPrimar y Scal e o f Intelligence , WPPS I (CDC ) 4 . Lincoln-Oseretsk y Moto r Developmen t

Scal e (ILZRO ) 5 . Californi aTes t

o f Personalit y Adjustmen t (ILZRO ) 6 . Frostin g Perceptua l Quotien t (ILZRO ) 7 . Bende r

Visual-Moto r

Gestal t Tes t (CDC , ILZRO ) 8 . Peabod y 9 . WRA T 10 . Wepma n 11 . Draw-a-perso n Al l o f th e test s selecte db y bot hstudie s wer e appropriat e fo r th e age s o f

th e childre n t o who mthe y wer e ad

ministered . Sinc e th e commo n groun dfo r thes e studie s i s th e WIS C test , wit hth e WPPS I use db y CD C an dth e McCarth y Scale s b y ILZR O fo r th e younge r

childre n i n thei r

studies , th e Committe e concentrate do n thes e thre e test s an dth e result s obtaine dfo r them . E. 3 RESULT S Th e stud y b y CD C report s result s fo r 2 7 childre n give n th e WPPS I (1 2 wit hbloo dlea dlevel s 40-8 0 figllOO m l an d1 5 wit hbloo dlea dlevel s les s tha n 4 0 figllOO ml ) an dfo r 9 7 childre n teste dwit hth e WIS C (3 4 i n th e "lea dgroup " an d6 3 i n th e "contro l group") . Statistica l analyse s wer e performe do n groupe ddat awithone taile dtests . Significan t

difference s betwee n lea dan dcontro l group s ar e reporte din thi s stud y fo r th e perfor

manc e IQ' s o f

th e WIC S an dWPPSI . I n subtes t scores , significan t

difference s wer e foun di n Codin g o n th e WIS C an dGeometri c Desig n o n th e WPPSI . Whe n dat afro mbot htest s ar e combined , asignifican t differenc e betwee n lea dan dcontro l group s o n performanc e I Q i s found . N o difference s wer e foun dbetwee n group s i n verba l IQ' s o r

full-scal e IW' s o f

th e WIS C o r

WPPSI . Th e ILZR O stud y base do n matc hpairin g solel y b y residence s report s n o significan t difference s in score s o n th e WIS C o r

McCarth y scale s betwee n group s withincrease dlea dabsorptio n an dpair-matche dcontrols . Statistica l analysi s wa s b y mean s o f two-wa y analysi s o f

varianc e b y ag e an dbloo dlea dlevels . Th e tw o studie s bas e muc ho f thei r conclusion s upo n psychometri c an dneurologica l testin g o f childre n fro mE l Pas o an dSmeltertown . Th e reporte dsignifican t difference s an dpsychometri c an dneuromoto r func

tion s i n th e CD C stud y wer e cloude db y potentiall y importan t methodologica l difficulties . Thes e include d E- 3P.9 9



### ag e difference s between cas e an dcontro l groups , limite dstatistical treatmen t o f th e psychometri c dat acol

lected , and , i

n th e ILZR O study , th e us e o f a n averag e o

f th e tw o highes t

bloo dleadlevel s t o categoriz e lead exposure . In addition , bot

hth e studie s share dth e followin g inheren t problems : 1 . Non-rando mexclusio n o f larg e group s o

f childre n 2 . Uncertaintie s a s t o th e selectio n o f contro l group s 3 . Relianc e upo n bloo dleada s th e indicato r o f leadexposure an dintoxicatio n i n analyse s o

f dat a 4 . Measuremen t

o f alimite daspec t

o f psychological behavio r 5 . Lack o f consideratio n o

f th e potentiall y disruptiv e influence s o n tes t takin g o f th e razin g o

f Smelter

town , closin g o

f it s school , resettlement , litigation , andpubli c controvers y 6 . Inability t o rul e ou t

possibl e preexistin g condition s Th e Committe e stresse dth e las t issue , notin g th e likelihoo dthat an y behaviora l o r

geneti c factor s that

pre dispos e a n individual chil dt o inges t o r absor b more leadthan anothe r chil dequall y expose dma y itself b e correlate dt o he resul t

o f psychometri c testing . In othe r word s a n increase dbloo dleadlevel ma y reflect , rathe r than cause , apreexistin g differenc e i n intelligenc e or

behavior , a

n issue inheren t

i n virtuall y al l retrospectiv e studie s o

f th e effects o

f low level bloo dlead . Th e opinio n o

f th ecommitte e wa s that

no fir mconclusion s coul db e draw n fro mth e studie s a s t o whether o r no t ther e ar e subclinical effects o f leado n childre n i

n E l Pas o andthat

th e report s anddat amad e availabl e hav e no t clearl y demonstrate dan

y psychologi c o r

neurologi c effects i

n th e childre n unde r

study . It note dth e absenc e o f major chroni c clinical effects , andconclude dthat thes e studie s therefor e d o no t bea r upo n th e con clusion s o f other investigation s under

differen t condition s an dthos e i

n whichclinical effects hav e been con firmed. However , becaus e o f inheren t problem s o

f study desig n andth e limitation s i n th e test s used , thi s find

ing shoul dno t

leadt o aconclusio n that

low level s o

f leadhav e n o effects o

n neuropsychological performance .

£ - 4 * US - GOVERNMEN TPRINTIN G OFFICE ; 1978 —757-140/668 1