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## Document

Number: 

# -ne) II-A-9 Docket Number: 

# A-83-2 2

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Sheet 118 of 118P. 2 

## A

## - i 

## 3 - 2 2-

REVIE WO F TH E NATIONA L AMBIEN T AI R QUALIT YSTANDARD S FO R LEAD :

EXPOSUR E ANALYSI S METHODOLOG YAN D VALIDATIO N

DRAF T REPOR T

Ai rQualit yManagemen tDivisio n Offic e o fAi rQualit yPlannin yan d Standard s U.S
. Environmenta l Protectio n Ayency Researc h Trianyl e Park , N.C
. 2771 1

Augus t198 8P. 3



### Thi s documen ti s a

n OAQP S staf fdraf ttha ti s bein g circulate d fo rtechnica l revie wand comment . I tha s no tbee n full y reviewe d withi n EP

Aand does no trepresen tAgenc ypolicy
.P. 4

TABL E O F CONTENT S Pag e 

### Lis to fFigure s ii i Lis to fTable s ii i I . Introductio n I- l II . Lea d Exposure : Multimedi a Consideration s .. . II- l A
. Airborn e Lea d 11- 3 B
. Lea d i n Soi l 11- 6 C
. Lea d i n Dus t11- 8 D
. Lea d i n th e Die t E. Lea d i n Wate r F
. Lea d i n Pain t III . Estimatin g Lea d Exposure s and Bloo d Lea d Level s A . Alternativ e Modelin g Approache s B . Calculatin g Bloo d Lea d Distribution s Aroun d Predicte d Mean s 1-1 1 1-1 2 1-1 3 II- l II- l
II- 2 IV . Integrate d Lea d Uptake/Biokineti c Mode l IV- 1 A . Estimate s o f Lea d Uptak e IV- 3 B . Uptak e an

d Bloo d Lea d Concentration s IV- 5 V . Statistica l Relationship s Betwee n Bloo d Lea d an d Airborn e Lead : Us e i n Disaggregat e an d Aggregat e Model s V- l A . Disaggregat e Mode l V- 3 B . Aggregat e Mode l V-1 3 VI . Validatio n o f Integrate d Lea d Uptake/Biokineti c Exposur e Mode l VI- 1 A
. Validatio n Usin g Eas tHelen a Dat a VI- 2 B
. Applicatio n o fUptake/Biokineti cMode l t o Othe rDat a Set s VI-1 1 C
. Conclusion s VI-1 6P. 5 1 1 

### TABL E O F CONTENT S (Continued ) Pag e VII . Applicatio n o f Lea d Exposur e Modelin g VII- 1 Appendi xA . Estimate s o f Lea d Uptak e A- l Appendi xB . Estimatio n o f th e Relationshi p Betwee n Soil , Dust ,

an d Ambien t Lea d B- l Appendi xC . Estimatin g 199 0 Baselin e Bloo d Lea d Average s C- 1 Reference sNumbe r ii i

LIST O F FIGURE S

Titl e 1 ' 1

Pag e P. 6

2- 1 Principa l Pathway s o fHuma n Exposur e t o Lea d 11- 2 2- 2 Trend s i n Maximu m Quarterl yLea d Concentration s fo r11- 5

Variou s Monito rType s 4- 1 Summar

yo fRelationship s Betwee n Dail yLea d Uptak e IV-1 4 an d Bloo d Lea d fo rDifferen tAg e Group s 5- 2 Summar

yo fEpidemiologica l Studie s o n Lea d Expose d Childre n V-1 5 5- 3 Bloo d Lead/Ai rLea d Slope s i n Childre n fo rDifferen tAg e V-1 7

an d Exposure s 6- 1 Compariso n o fDistributio n o fMeasure d Bloo d Lea d Level s VI- 7

i n Children , 1- 5 year s o fAge , Livin g Withi n 2.2 5 mile s o fE.Helen a Smelte rvs . Level s Predicte d b yUptake/Biokineti c Mode l (Ru n B)
. 6- 2 Compariso n o fDistributio n o fMeasure d Bloo d Lea d Level s VI- 8

i n Children , 1- 5 year s o fAge , Livin g Withi n 2.2 5 mile s o fE.Helen a Smelte rvs . Level s Predicte d b yUptake/Biokineti c Mode l (Ru n C)
.

LIS T O F TABLE S Numbe r Titl e Pag e 2- 1 Typica l Lea d Concentration s i n Variou s Exposur e Medi a II- 2 2- 2 Frequenc yDistribution s o f Maximu mQuarterl yLea d

Concentration s b

yTyp e o f Sit e . 11- 5 3- 1 Compariso n o f Estimate d GSD s Acros s Severa l Studie s 111- 5 3- 2 Illustrativ e Bloo d Lea d Distribution s Assumin g Differen t 111- 8

Mea n Bloo d Lead s an d Geometri c Standar d Deviation s 4- 1 Estimate d 199 0 Averag e Lea d Intak e an d Uptak e i n 2-Yea r IV- 4 Childre n Unde r Averag e Ai r Lea d Level sP. 7 I V
4- 2 Predicte d Equilibrate d Bloo d Lea d Level s Ove rTim e Among ' IV-1 2

Childre n wit h Constan tLea d Uptake s 5- 1 Disaggregat e Mode l o fContribution s fro m Variou s Medi a V- 8

t o 199 0 Media n Bloo d Lea d Level s o fU.S
. Childre n ( 2 Year s o fAge) : Backgroun d Level s an d Incrementa l Contribution s fro m Ai r 6- 1 Compariso n o fIntegrate d Lea d Uptake/Biokineti cMode l VI- 6

Prediction s t o 198 3 Measurement s i n Eas tHelen a 6- 2 Children' s Bloo d Lea d Level s Measure d i n Omaha , 1971-197 7 VI-1 3

Vs
. Integrate d Uptake/Biokineti cMode l Prediction s 6- 3 Children' s Bloo d Lea d Level s Measure d i n Silve rValley , VI-1 5

Montan a 1974-197 5 Vs
. Integrate d Uptake/Biokineti cMode l Prediction s A- l Age-Specifi cEstimat e o fTota l Dietar yLea d Intak e fo rA- 5

1990-199 6 A- 4 Long-Ter m Relationship s Betwee n Dust , Soi l an d Ambien tLea d A- 5 Estimatin g Short-Ter m Response s i n Equilibriu m Soi l an d

Dus tLea d Level s fro m Change s i n Ambien tLea d B- l Environmenta l Lea d Concentration s i n Omaha , Nebrask a B- 2 Linea rMode l Paramete rEstimate s fo rAir , Soi l an d Dus t

Lea d Relationship s C- 1 Selecte d 197 8 Bloo d Lea d Level s fro m NHANE S I I C- 2 Predicte d Change s i n Averag e Bloo d Lea d Level s Associate d

wit h Gasolin e Lea d Tren d C- 3 Trend s i n Dietar yLea d Intake : Tota l Intak e (an d

Atmospheri cContributions ) C- 4 Adjustment s t o 197 8 Mean Bloo d Lea d Level s fo rDietar y

Lea d Reduction s C- 5 Derivatio n o f199 0 "Baseline " Averag e Bloo d Lea d Level s C- 6 Maternal:Chil d Bloo d Lea d Concentration s an d Ratio s A-1 2 A-1 2 B- 5 B- 8 C- 2 C- 6 C- 8 C-1 2 C-1 5 C-1 7P. 8

REVIE WO

F TH E NATIONA LAMBIEN TAI R QUALITYSTANDARDS FU R LEAD : Exposur e Analysi s Methodolog yan d Validatio n I . INTRODUCTION EP Ai s assessin g healt h risk s associate d wit h lea d exposure , especiall y nea rstationar ysource s o fatmospheri clea d emission s (e.y. , lea d smelters) , unde ralternativ e regulator yscenario s fo rit s revie wo fth e Nationa l Ambien tAi rQualit yStandard s (NAAQS ) fo rlead
. Th e scientifi can d technica l informatio n o n lea d ha s bee n reviewe d i n EPA' s "Ai rQualit y Criteri a fo rLead " (EPA , 1986)
. A"staf fpaper" , i n fina l preparation , wil l evaluat e an d interpre tth e mos trelevan to ftha tinformatio n t o hel p th e Administrato ri n selectin g th e averayin ytimes , forms , an d level s fo r th e primar yan d secondar ystandards. * Acritica l elemen ti n thi s proces s wil l b e a n exposur e analysi s whereb ybloo d lea d level s ar e estimate d amon g population s expose d unde ralternativ e lea d regulation s i n th e future
. (A n exposur e analysi s o ffou rlea d sources , i.e. , fou r"cas e studies" , i s currentl ybein g prepare d usin g methodologie s documente d i n thi s report. ) Thi s repor tsummarize s relevan tinformatio n o n lea d exposur e an d present s th e modelin g methodoloyie s tha tth e staf fbelieve s shoul d b e con sidere d fo rth e lea d NAAQ S exposur e analysis
. Result s o fvalidatin yon e o fthes e methodologie s ar e als o presented
. Normally , suc h description s woul d b e incorporate d int o th e staf f paper . Du e t o th e comple xnatur e o flea d exposur e analysis , w e chos e t o separat e thi s repor tt o achiev e a mor e thorouy h revie wan d als o t o mak e i teasie rfo ryenera l us e i n lea d exposur e analysi s unrelate d t o th e NAAQ S review
. Thi s repor tshoul d the n b e considere d a s a supplemen t t o *Th e curren tprimar ystandar d fo rlea d (t o protec tpubli chealth ) i s 1. 5 microgram s pe rcubi cmete r(py/nr) , maximu m arithmeti cmean average d ove r a calenda rquarter . Th e secondar ystandar d (t o protec tpubli cwelfare ) i s identica l t o th e primar ystandard
.P. 9 1- 2 th e OAQP

S staf fpaper . I ti s intende d fo rthos e reader s familia rwit h th e technica l informatio n containe d i n th e criteri a documen t (hereafte r referre d t o as "CO")
. Thi s repor tdoe s no tdiscus s healt h effect s associate d wit h lea d o rth e implication s o fdifferen tlevel s o flea d exposure . Tha t informatio n i s reviewe d i n th e criteri a documen tan d wil l b e inteyrate d i n th e staf fpape rwit h result s o fth e exposur e analysis
. Bot h thi s pape ran d th e staf fpape rwil l b e circulate d fo rrevie wbyth e Clea n Ai r Scienc e Advisor yCommitte e an d th e public
. Th e approac h use d i n thi s pape ri s t o asses s an d inteyrat e exposure relate d informatio n derive d fro m th e criteri a documen t revie wtha tth e staf fbelieve s shoul d b e considere d i n th e revie wo fth e primar ylea d NAAQS
. Sectio n I I present s relevan tfeature s o fhuman exposur e t o atmospheri can d non-atmospheri csource s o flea d throuy h variou s pathways
. Sectio n II I introduce s differen tapproache s t o estimat e th e impac to f alternative , a i rlea d level s o n lea d bod yburden s amon ydifferen tpopulations
. Sectio n I Van d Vdiscus s th e methodoloyie s o fthes e differen tapproache s i n detail
. Sectio n V I present s result s o fvalidatio n exercise s usin yth e uptake/biokineti cmodel
. Sectio n VI I present s som e application s o fth e modelin g approache s describe d i n thi s repor ti n additio n t o thei rrol e i n th e revie wo fth e lea d NAAQS
.P.1 0

I I
. LEA

D EXPOSURE : MULTIMEDI ACONSIDERATION S I n orde rt o asses s th e risk s associate d wit h alternativ e lea d NAAQS , i ti s necessar yt o understan d th e influenc e exerte d byatmospheri clea d o n th e tota l lea d exposur e o fth e population(s ) o fconcer n throug h variou s exposur e pathways
. Relevan tdat a o n thes e pathway s an d th e relationship s betwee n ai rlea d an d lea d i n othe rmedi a ar e summarize d i n thi s section
. Th e source s an d pathway s o fhuman lea d exposur e ar e diagramme d i n Figur e 2- 1 an d typica l level s o flea d i n differen tmedi a t o whic h U.S
. population s ar e expose d ar e presente d i n Tabl e 2-1 . Huma n exposur e t o lea d ca n b e trace d primaril yt o lea d i n pain tpiyments , solde ri n canne d food s an d plumbing , as wel l as t o atmospheri clead
. Althoug h airborn e lea d i s a principa l startin g poin to fenvironmenta l contamination , ora l intak e o f deposite d atmospheri clea d i s ofte n th e primar yidentifiabl e facto rpredictin g th e bloo d lea d o fyoun g children
. Hig h correlation s hav e bee n foun d betwee n children' s bloo d lea d an d th e lea d conten to fhousehol d dust , playgroun d dust , mouthin g behavior , lea d o n children' s hand s an d househol d cleanlines s (Sayr e e tal. , 1974 ; Bake re tal. , 1977 ; Charne ye tal. , 1980 ; Roel s e t al. , 1980 , Yanke l e tal. , 1977 ; Angl e e tal. , 1979 ; Walte re tal. , 1980 ; Brunekree fe tal. , 1981 ; Quah e tal. , 1982 ; Bellinge re tal. , 1986 ; Bornschei n e tal. , 1986)
. Larg e scal e isotopi cstudie s provid e stron g evidenc e tha tai rlea d ha s a rapi d an d measurabl e effec to n ingeste d lead , eve n i n adul tpopulation s a tlo wlevel s o fai rlea d (Facchett i e tal. , 1985)
. I ti s necessary , therefore , t o attemp tt o quantif yho watmospheri c anission s ca n influenc e human exposur e no tonl ythrouy h direc tinhalatio n o flead-containin g particle s bu tthroug h ingestio n o flea d whic h deposit s ont o soil , dusts , vegetation , an d othe renvironmenta l surfaces
.P.1 1 

## ri- 2

SURFAC E AN O QROUN O WATE R

DRINKIN G WATE R

MA N FIGUR E 2-1 . PRINCIPA L PATHWAY S O F HUMA

NEXPOSUR E TO LEAD . HEAV Y ARROW S AR E THOS E PATHWAY S DISCUSSE D INGREATES T DETAIL . FROMCD , FIGUR E 7-1 .

TABL E 2-1 . TYPICA

L LEA D CONCENTRATION S INVARIOU S EXPOSUR E MEDI A Mediu m Ambien t A1r(pg/m3) b Indoo rA1 r(pg/m 3 )
Soi l (ppm )
Stree t Oust (ppm) d House Oust (ppm) d
Typica l Food s (ppm ) Wate r(yg/l ) Paint e Rura l Are a U. l 0.0 3 - U.0 8
5-3 0
8 0 - 13 0 (90 ) 5 0 - 50 0 (300 )
0.00 2 - 0. 8 5-7 5 M9/

L
< 1 - >5 mg/cm 2 Urba n Are a 0. 1 - U. 3 0.0 3 - 0. 2
3 0 - 450 0
10 0 - 5,00 0 (1500 ) 5 0 - 3,00 0 (1000 )
Sam e Sam e Sam e Nea rPoin t Source(s) a

0. 3 - 3. 0 0. 2 - 2. 4
15 0 - 15,00 0 (25,000 ) 10 0 - 20,00 0 (10,000 )
Sam e Sam e Sam e Reference s

Faoro , 198 8 See Footnot e c CO , Tabl e 7-11 ; Mlelk e e t al. ; 1983 ; Se e Tabl e B- 3 Nriagu , 1978 ; CO , Tabl e 7-2 6 U.S . EPA , 1977 ; Landriga n e t al. , 1975 ; Mors e e t al. , 1979 ; Angl e and Mclntlr e (1979 ) Flege l e t al . (1988 ) BMskln , 198 8 Billic k an d Gray , 197 8

aW1thi n 2- 5 k

m ofsource

s includin g primar

yan d secondar

ylea d smelters , batter yplants . Represent s quarterl yaverages monitored i n 1986 . c Range ofindoor/outdoo rratio s use d (0. 3 - 0.8 ) fro m CO , Tabl e 7- 6 excep t nea rpoin t source

s wher e larg e particle s pre dominat e an d infiltratio n int o home s i s low , rati o appear s t o b e close rt o 0. 3 (Cohen an d Conen , 1980) . a Value s i n parentheses represen t estimate s provide d i n C D (Table s 7-1 8 an

d 7-20 ) a

s typica l averages . eS1nce ther e ma

yb e severa l layer s oflead-base d pain t o n a give n surface , absolut e concentratio n oflea d i s les s usefu l tha n mg/cm 2 . Survey s b yHU D i n Pittsburg h showe d tha t mor

e tha n 70

Xo fpre-194 0 dwe^lr; ; unit s an d 20 Xo fpost 196 0 unit s ha

d a t leas t on

e surfac e wit h mor

e tha n 1. 5 mg/cm 2 lea d pain t (NAS , 1980) .P.1 2 

### II- 3 Unti l recently , betwee n 85-90 % o fairborn e lea d i n th e U.S
. originate d fro m gasolin e combustion , wit h mos to fth e remainde rfro m stationar yindustria l processe s suc h as primar yan d secondar ylea d smelting , batter yplants , an d combustio n o foil , coal , wast e oi l an d municipa l waste . Becaus e o fth e accelerate d reductio n o fth e lea d conten ti n gasoline , concer n regardin g lea d emission s int o th e ambien t ai ri s shiftin g almos texclusivel yt o relativel yconfine d area s surroundin ysignifican tstationar ysource s o f lea d an d thi s paper' s focu s wil l b e o n estimatin g exposure s an d risk s i n thos e locales
. A
. Airborn e Lead 1 . Physical , Chemica l an d Spatia l Characteristic s Ambien tai rlea d level s resul tfro m curren tindustria l emissions , lead-contaminate d roa d an d wind-blow n dust , an d automotiv e exhaust
. Th e industria l contributio n include s point , fugitiv e process , an d material s handlin g emission s fro m lea d mininy , smelting , an d recover yoperations
. Curren tcontribution s o froa d an d othe rfugitiv e dus tvary , wit h locatio n an d th e influenc e o fhistoricall ycontaminate d soil
. I n general , abou t50 % o fautomotiv e lea d emission s deposit s withi n a fewhundre d meter s o fmajo rroadway s (Daine s e tal. , 1970 ; Huntzicke re t al. , 1975 ; Inyall s an d Garbe , 1982 ) whil e th e ranainin yparticle s ar e smal l enouy h t o remai n airborn e an d ca n trave l hundred s o rthousand s o fkilometers
. Thi s likel yaccount s fo rth e surfac e contaminatio n o fpola rglaciers , oceans , an d othe rremot e location s aroun d th e glob e (Settl e an d Patterson , 1982)
. I n contras tt o automobil e exhaust , atmospheri clea d emission s fro m industria l plant s tha tproces s lea d an d it s product s hav e contribute d littl e t o th e overal l pollutio n loa d acros s large , regiona l area s althoug h fallou tP.1 3 

### II- 4 fro m thes e source s ca n b e sever e o n a loca l scale
. Th e trajectorie s "o f atmospheri cemission s fro m industria l source s var ywit h win d spee d an d direction
. Hig h concentration s aroun d lea d smelter s an d othe rmajo r emitter s resul tmainl yfro m fugitiv e emissions , predominatel ymad e u p o f larg e (> 7 micrometer s (pm) ) lea d particle s resultin g fro m material s handliny , furnac e upsets , an d furnac e charyin g an d tappin g operation s (Landriga n e tal. , 1975 ; Jennet te tal. , 1977 ; Batty e e tal. , 1985)
. Beyon d th e immediat e are a ( * 2 km ) o flea d stationar ysources , proces s emission s fro m stacks , predominatel yas lea d sulfate s an d oxide s wit h a siz e rang e betwee n 1 an d 1 0 pm , becom e th e majo rsourc e o flea d i n soil s an d ai r(Dor n e tal. , 1976 ; Roel s e tal. , 1980 ; Davidso n an d Osborn , 1984)
. 2 . Ambien tConcentration s A s indicate d i n th e C D (Sectio n 7.2.1) , lea d level s i n urba n area s an d nea rpoin tsource s hav e bee n markedl yreduce d sinc e 1977 byth e us e o funleade d gasolin e i n ne wcar s equippe d wit h catalyti cconverters , th e lead-in-gasolin e phasedow n program , an d stead yreduction s i n anission s fro m stationar ysource s as a resul to fth e 197 8 lea d NAAQS
. Recen t(1980-1983 ) ai rqualit ydat a fo rstationar ysourc e sites , micro-scal e roadsid e sites , middl e scal e roadsid e sites , neighborhoo d scal e roadsid e sites , an d othe r non-classifie d site s ar e summarize d i n Tabl e 2- 2 (Battye , 1984)
. Th e monitorin g site s locate d nea rstationar ysource s reporte d th e majorit yo f quarterl yaverag e concentration s ove r1. 5 pg/nP
. Trend s i n maximu m quarterl yaverage s betwee n 198 0 an d 198 3 ar e illustrate d i n Figur e 2-2 . Thes e trend s dat a ar e generall ybase d o n a limite d numbe ro favailabl e monitorin g site s tha tremaine d i n servic e sinc e 198 0 (e.g. , 2 7 stationar ysourc e sites , 9 neighborhoo d scal e sites)
.P.1 4 II- 5 TABL E 2-2 . FREQUENC Y DISTRIBUTION S O F MAXIMU

M QUARTERL

Y LEA D CONCENTRATION

S

- B Y TYP E C F SITE *

Sit e type/time fram

e 198 0 through198 3 Al l monitors 0 Stationary

sourc e Microscal e roadside 3 Middl e scal e Neighborhoo dscal e 198 3 onl y Al l monitors 0 Stationary

sourc e Microscal e roads1de d Middl e scal e Neighborhoo dscal e Percen t <0. 5
69 62 1 7 39 6 1
7 1 5 3 1 6 53 7 2 o f sit e 0.5-1. 0
2 2 1 6 40 42 3 2
19 2 4 47 3 3 28 year s i n concentratio n 1.0-1. 5 1.5-2. 0
5 8 2 7 18 5
5 9 32 13 0 2

3 1 3 0 0
1 2 5 0 0 ranges 0 >2. 0
2 1 1 3 0 2
3 1 1 0 0 0 Mean
0.5 3 0.9 5 0.9 9 0.6 8 0.5 1
0.5 1 0.8 8 0.8 3 0.6 0 0.4 0 Tota l

site
year s
118 9 15 9 3 0 3 3 6 2
36 0 4 5 1 9 1 5 2 9 Tota l

numbe r o f site s
41 4 5 6 1 8 1 5 2 9
36 0 4 5 1 9 1 5 2 9
d Dat a ar e fro m th e SAROA D syste m an d represen t th e number s o fsite-year s fo rwhic h th e maximu m quarterl yconcentration s fal l withi n th e designate d concentratio n ranges . T o be included , a site-yea rmust hav e fou rvali d quarter s o fdata . ^Concentratio n range s ar e i n unit s o fug/m3 . c Include s site s previousl yclassifie d int o categorie s (e.g. , urban ) tha t do no t meet an yo fth e curren t definitions . d M1croscal e site s ar e withi n 5-1 5 meter s fro m a majo rroadwayan d 2- 7 meter s above th e ground . 

### Source:Battye , 198

4

K! -

ti l L J 

## 1 2

L U 2. 0 1 .9 1 . 8 1 . 7 1 . 6 1 . 5 1 .4 - 1 . 3 

### 1 - 2 H 1 . ! 1 . 0 0. 9 0. 8 0. 7 0. 6 0. 5 0. 4 0. 3 0. 2 O. 1 . 0 . 0 MICROSCAL E



### " v * ^ \ STATIONAR YSOURCE S

• M \



### -- K 

# MoSEPSBtiSlS?0

SCAL E AL L MONITOR S 

## ^ss S

"^ a

198 0 198 1 198 2 198 3

Yea r FIGUR E 2-2 . TREND S I NMAXIMU M QUARTERL Y LEAD CONCENTRATIO NFO R VARIOU S

MONITO R TYPES . SOURCE : BATTYE , 1984 .P.1 5 

### II- 6 Despit e th e ne

wsitin g guideline s implemente d i n 198 2 tha tadde d site s close rt o traffi cemissions , microscal e reading s hav e bee n declining , correspondin g t o th e phasedow n o fth e lea d conten ti n gasolin e an d reduction s i n leade d gasolin e usag e du e t o th e yradua l phase-ou to folde rcar s burnin g leade d gasoline
. Similarly , annua l an d maximu m quarterl yaveray e lea d level s nea rpoin tsource s hav e als o decrease d sinc e 1980 , partl ydu e t o increase d control s bylead-emittin g source s i n complianc e wit h stat e implementatio n plan s as wel l as t o decrease d industria l productio n a t lead-enittin g facilitie s (Silvasi , 1985)
. B ySeptembe r1988 , th e informatio n presente d her e wil l b e update d t o includ e dat a u p throug h 1987 . B
. Lea d i n Soi l Th e natura l occurrenc e o flea d i n th e earth' s crus taverage s 5-5 0 p g lead/ g soi l i n variou s soils * (CD , p . 7-28)
. Much o fth e lea d i n th e atmospher e deposit s o n terrestria l surface s wher e i ti s retaine d i n organi ccomplexe s nea rth e soi l surfac e (CD , p . 7-31)
. Th e abilit yo f soi l t o immobiliz e lea d largel ydepend s o n soi l p H an d organi cconten t (i.e. , fulvi can d humi csubstances)
. Man yU.S
. soil s appea rt o hav e a larg e capacit yt o bin d lea d wit h onl ya smal l fractio n dissolve d i n soi l moistur e wher e i ti s availabl e fo rplan tuptake
. Th e environmenta l impac to flea d o n th e biot a o fterrestria l an d aquati cecosystem s i s discusse d i n Chapte r6 o fth e CD
. Th e uppe rlaye ro froadsid e soil s ma ycontai n deposite d atmospheri c lea d i n concentration s o f3 0 t o 200 0 ppm i n exces s o fnatura l level s withi n 2 5 meter s o fth e roadbed , beyon d whic h concentration s declin e abruptl yi n
''On e pg/ g i s equivalen tt o on e par tpe rmillio n o r1 ppm .P.1 6

II- 7 relatio n t o traffi cdensit yan d vehicl e spee d (Pay e an d Ganje , 1970 ; Quarle s e tal , 1974 ; Wheele ran d Rolfe , 1979 ; Pierso n an d Brachaczek , ly76)
. Topsoi l lea d concentration s aroun d variou s lea d poin tsource s generall y decreas e exponentiall ywithi n a 3-1 0 k m radiu s fro m 100-60,00 0 ppm dow n t o backgroun d level s (Yanke l e tal. , 1977 ; Schmit t e tal. , 1979 ; Roel s e tal. , 1978 ; Dieme l e tal. , 1981 ; Fugas , 1977)
. However , elevate d soi l lea d level s hav e eve n bee n foun d a tdistance s exceedin g 20-2 5 k m fro m som e smelter s (Wixson , 1978)
. Limite d dat a indicat e tha tlea d i n soi l nea r primar yan d secondar ylea d smelter s occur s as lea d oxides , sulfide , sulfate , an d elementa l lea d (Olso n an d Skogerboe , 1975 ; Corri n an d Natusch , 1977)
. Urba n soil s ar e contaminate d b ylea d fro m a combinatio n o fautomotiv e an d poin tsourc e depositio n as wel l as fro m lea d i n pain to n indoo ran d outdoo rsurfaces
. Elevate d soi l lea d concentration s (a s hig h a s 200 0 ppm ) hav e bee n foun d withi n 1 0 fee to fwood fram e house s painte d wit h lead-base d pain t(Te rHaa ran d Aronow , 1974)
. Accumulation s o flea d i n soil s (an d dusts ) aroun d bric k o rston e structure s hav e als o bee n found , an d ca n b e partiall yattribute d t o washof flea d collecte d o n roofs , ledges , an d exterio r wall s (Wheele ran d Rolfe , 1979) , an d possibl yt o a n aerodynami ceffec to f th e structure s o n depositio n o flea d fro m nearb ysources . Vegetabl e garde n soi l sample s collecte d i n a 30-mil e radiu s o fdowntow n Baltimor e had lea d level s u p t o 10,90 0 pp m wit h a media n valu e o f10 0 ppm (Mielk e e tal. , 1983)
. Much o fthi s lea d wa s attribute d t o automotiv e exhaus tan d industria l emission s becaus e o fth e nea rabsenc e o flea d painte d house s an d th e clustere d patter n o flea d level s aroun d downtown
. Soi l lea d concentration s i n a sampl e o fcit ypark s hav e als o bee n reporte d t o b e high , rangin g fro m 20 0 t o 330 0 ppm (Cho

we tal. , 1975 ; Zimdah l an d Hassett , 1977)
.P.1 7


### II- 8 Improvement s i n ai rqualit yd o no tnecessaril yinvolv e reduction s i n soi l lea d a tth e sam e rate . Th e decontaminatio n o fth e environmen ti s a ver ycomple xan d slo wprocess , particularl yfo rsoi l lea d whic h ha s bee n show n t o remai n a televate d level s severa l year s afte rlea d manufacturin g plant s hav e cease d operatin g (Prpic-Maji ce tal. , 1984)
. Whil e lea d i n soi l i s relativel yimmobile , i tstil l ma yente rth e foo d chain , b e ingeste d directly , o rma

yb e redisperse d int o th e ai ran d resuspende d int o wate rby win d scatterin g o fsoi l particle s an d dust
. Consequently , population s livin g i n area s wit h historica l accumulation s o flea d i n soi l ma ycontinu e t o b e expose d t o lea d fo rindefinit e period s despit e effectiv e control s o f atmospheri cemissions
. C
. Lead i n Dus t Ous ti s a norma l componen to fth e home (i.e. , "hous e dust" ) as wel l as th e outdoo renvironmen twher e i tca n b e foun d o n sidewalks , playgrounds , driveways , an d othe rh-ar d surfaces
. Anthropogeni cmaterial s deposite d o n thes e outdoo rsurface s wil l b e referre d t o as "stree tdusts"
. I n addition , th e ver yto p laye ro fsoil s (includin g lea flitter ) t o whic h people , particularl y children , com e i n direc tcontact , ar e considere d i n th e criteri a documen t t o b e "soi l dusts"
. Bot h hous e dus tan d street/soi l dus tcontai n lea d fro m atmospheri c deposition , "natural " soil , an d pain tchips
. A s wit h roadsid e soil , significan t correlation s betwee n lea d concentration s i n stree tdus t an d th e proximit y an d densit yo ftraffi chav e bee n foun d (Rolf e e tal. , 1977 ; La u an d Wong , 1982)
. Concentration s o flea d i n dust s o n playgrounds , streets , an d soi l surface s als o increas e wit h highe rai rlea d concentration s an d wit h proximit y t o stationar ylea d source s (Roel s e tal. , 1980 ; Brunekree fe tal. , 1981 ; Yanke l e tal. , 1977)
. A s summarize d byNriag u (1978) , stree tdust s fro mP.1 8 

### II- 9
differen tU.S
. citie s containe d betwee n 30 0 an d 18,00 0 pp m lead
. Asurve y o fstree tdust s i n 77 midwester n citie s showe d a n averag e lea d conten to f 1,63 6 ppm i n residentia l neighborhood s an d 2,41 3 pp m i n commercia l an d industria l area s (NAS , 1980)
. Limite d chemica l analyse s o froadsid e soil s an d dust s fro m U.S
. citie s foun d lea d predominatel yas sulfate , alon g wit h mino ramount s o foxid e an d halid e salt s (Olso n an d Skogerboe , 1975 ; Corri n an d Natusch , 1977)
. Pavemen tdust , stree tdust , gutte rdebris , an d househol d dus tsample s contai n mostl ylarg e lea d particle s rangin g betwee n 4 0 an d 100 0 p m (Pierso n an d Brachaczek , 1976 ; Sturge s an d Harrison , 1985 ; Dugga n an d Inskip , 1985)
. Highe rlea d concentration s ar e usuall yfoun d i n th e smalle rsize d fractions ; th e concentratio n i n a sampl e o fstree tdus t sieve d a t10 0 pm , fo rexample , i s usuall ya tleas ttw o t o fou rtime s greate r tha n tha ti n th e sam e sampl e sieve d a t1,00 0 p m (Dugga n an d Inskip , 1985)
. Preliminar ywor k

indicate s coars e particle s larye rtha n a fe whundre d micrometer s i n diamete rare.easil ybrushe d of fhand s an d clothin g wherea s onl yth e smalle rone s (<100-20 0 pm) readil yadher e t o finger s an d ar e thu s mor e likel yt o b e ingeste d (Dugga n an d Inski p 1985)
. Airborn e lea d deposite d o n streets , sidewalk s an d driveway s i s highl y mobil e an d subjec tt o furthe rdistributio n bywin d an d water . Windblow n particle s associate d wit h dus tar e ap tt o b e redeposite d withi n th e urba n environmen t becaus e o fth e comple xwin d current s cause d b ybuilding s an d stree tcanyons . Ther e i s som e evidenc e o n th e persistenc e o flea d i n stree tdust
. Asurve yo frainwashe d area s i n th e U.K
. an d Ne wZealan d conclude d tha tth e norma l acidit yo frai n (p H betwee n 4 an d 5 ) wa s insufficien tt o completel ydissolv e an d transpor tlea d particles , an d tha t residu e nea rstreet s pose s a healt h hazar d t o childre n wh o ar e pron e t o inges tstree tdust s (Da ye tal. , 1979)
. However , Laxe n an d Harriso nP.1 9 11-1 0 (1977 ) foun d tha tonl ya ligh trainfal l ( 2 t o 3 mm ) i s sufficien tt o .remov e 90% o fth e lea d fro m th e roa d surface , mainl yt o surroundin g soi l an d t o waterways . Furthermore , base d o n depositio n fluxe s aroun d a majo rroadwa y ove ra yea ran d concentration s o flea d i n th e roa d drainag e water , Harriso n e tal
. (1985 ) estimate d tha tremova l o flea d i n runof fwater s exceed s tha t deposite d o n th e roadsid e verges . Th e rat e o fremova l o flea d fro m stree t dust s i s als o dependen to n th e frequenc yan d efficienc yo fstree tcleanin g operation s an d i tappear s reasonabl e t o assum e tha twit h continuou s input , lea d concentration s i n street , curb , an d sidewal k dus twil l ris e betwee n precipitatio n an d stree tcleanin g episodes , an d dro p thereafter
. Lead level s i n hous e dus tca n als o b e expecte d t o var yconsiderabl y dependin g o n hous e cleanin g practices , as demonstrate d byCharne ye tal. , (1983) , as wel l as o n th e presenc e an d conditio n o flead-base d painte d surfaces , th e presenc e o fciyarett e smoke , th e amoun to fdus tan d soi l blow n int o o rcarrie d int o th e hous e o n clothin yand
. shoe s (especiall yo n thos e occupationall yexpose d t o lead) , indoo rsource s o flea d othe rtha n pain t(e.g. , solderiny) , th e permeabilit yo fth e home t o outdoo rai r(whic h ca n var ywit h season) , an d outdoo rconcentration s o fai rlead
. Survey s o f a divers e se to fhome s indicat e a wid e rany e o fhous e dus tlea d level s betwee n 1 8 an d 16,00 0 ppm (EPA , 1977 ; Harrison , 1979 ; Angl e an d Mclntire , 1979 ) an d as hig h as 100,00 0 pp m withi n 2 k

m o fsmelte r(Landriga n e tal. , 1975)
. Fo rpresen tpurposes , th e importan tpoin tt o not e i s tha t unlik e lea d tha ti s incorporate d int o soil , lea d i n surfac e dusts , bot h indoor s an d outdoors , i s mobil e an d ca n b e expecte d t o respon d ove rtim e t o a much greate rdegre e t o change s i n atmospheri clea d anissions
. Thi s ha s bee n observe d aroun d poin tsource s where , followin g th e installatio n o r supplementatio n o femissio n control s an d significan timprovement s i n ai rP.2 0 

### 11-1 1 lea d q'uality , siynifican t drop s i n concentration s o flea d i n playyroun d dust , surfac e dus to n soil , an d i n hous e dus thav e bee n observe d withi n 1 t o 2 year s (Mors e e tal. , 1979 ; Prpic-Maji ce tal. , 1984)
. Thi s als o suyyest s tha tlea d i n surfac e dust s i n non-poin tsourc e area s shoul d declin e a s a resul to fth e lea d phasedow n i n gasoline
. T o asses s th e impac to fatmospheri clea d o n children' s tota l exposure , i ti s necessar yt o estimat e th e contribution s o fdifferen tai rlea d level s t o outdoo ran d indoo rsoil/dus t lea d level s a s wel l a

s th e amoun to fdir t a chil d ma

yingest , bot h inadvertantly , an d deliberately
. Thes e issue s are addresse d i n th e modelin yapproache s presente d i n Section s I Van d V
. D
. Lead i n th e Die t Th e inyestio n o ffoo d i s a majo rcomponen to fmos tindividuals ' tota l lea d uptake , althoug h th e relativ e contributio n i s a functio n o fthei r aye , an d th e siz e an d typ e o fdiet
. Th e occurrenc e o flea d i n th e die t ma yb e a resul to fa ) natura l source s o flead ; b ) depositio n o fairborn e lea d particle s ont o crops , forage , feed , soils , an d water ; an d c ) th e harvesting , processing , transportation , packaging , preparation , an d storag e o ffoo d durin g whic h lea d ca n b e introduce d a tever ystage , eithe rbyatmospheri cdepositio n o rthroug h metalli ccontamination , particularl yfro m solde ri n can s o ri n plumbing
. Recen tstudie s o n lea d conten to fvariou s foods , bot h befor e an d afte r processing , packaging , an d preparation , an d o n foo d consumptio n pattern s i n th e U.S. , provid e informatio n o n dietar ylea d intake s fo rdifferen t population s (Beloia n an d McDowell , 1981 ; Wolni k e tal. , 1983 ; Nationa l Food Processor s Associations , 1982 ; Pennington , 1983 ; U.S
. FDA , 1983 , 1984)
. Usin ythes e dat a fo r1982-83 , a "Multipl e Sourc e Foo d Model " wa s develope d i n th e C

D tha tapportion s lea d i n "typical " chil d an d adul tdiet s t o th e followin ysources : natura l soi l lead , direc t atmospheri clea d adde d t oP.2 1

11-1 2 foo d crop s befor e harves tan d durin g processing , indirec tatmospheric " lea d tha tha s bee n incorporate d i n soils , lea d i n solde rfro m foo d can s an d drinkin g water , an d lea d whos e origi n canno tb e determine d a tpresen t (CD , Sectio n 7.3.1.2)
. Th e mode l wa s validate d usin g th e sam e parameter s alon g wit h mor e recen tfoo d dat a fro m 198 4 an d 198 5 t o successfull ypredic t continuin g decline s i n dietar ylea d intake
. Fo rexample , dietar ylea d intak e fo ra 2-yea rol d chil d ha s droppe d fro m abou t45-5 0 pg/da yi n 197 8 t o a n estimate d 13. 1 pg/da yi n 1985 ; comparabl e decline s (fro m 45-5 0 pg/da yt o 15-2 0 pg/day ) hav e bee n see n i n differen tadul tpopulation s sinc e 198 2 (Flege l e tal. , 1988. ) Thes e trend s ar e attributabl e t o th e drasti creductio n i n gasolin e lea d emission s an d th e voluntar yphaseou to flead-soldere d can s byU.S
. manufacturer s sinc e th e lat e 1970's
. Thi s downward shif ti s expecte d t o continu e u p unti l th e earl y1990' s as lea d fro m bot h thes e source s drop s further
. Th e method s b ywhic h estimate s o fdietar ylea d intak e fro m th e Multipl e Sourc e Foo d Mode l ar e derive d an d applie d t o modelin g tota l lea d exposur e ar e discusse d i n Appendi xAan d Sectio n V
. E
. Lea d i n Wate r Lea d i s a natural , usuall yminor , constituen to fsurfac e an d groun d waters . Atmospheri clea d ca n ente raquati csystem s throug h direc t fallou to ri n surfac e runof fas suspende d particle s o radsorbe d t o soi l particles
. Undermos t condition s (pH , temperature , alkalinity) , lea d form s insolubl e salt s an d precipitate s t o sediments , whic h probabl yaccount s fo r th e lo wlea d conten to fU.S
. sourc e wate rsupplies ; th e averag e concentratio n rangin g betwee n 3 an d 4 microgram s P b pe rlite rwate r(pg/L ) (NAS , 1980)
. I n contrast , lea d level s i n household , school , o roffic e buildin g drinkin g wate rca n b e much hiyhe rdu e t o plumbin g corrosio n an d subsequen t leachin g o flead , rangin g betwee n 1 0 an d 3 0 pg/ 1 o n average . Th e combinatio nP.2 2
11-1 3 o fcorrosiv e (i.e. , sof to racidic ) wate ran d lea d pipe s o rlea d soldere d joint s i n distributio n system s o rhouse s create s localize d zone s o fhig h lea d concentration s u p t o 38 0 pg/ 1 (Wort h e tal. , 1981)
. I n general , level s ar e highes ti n sample s o fho tand/o rstagnan t"firs tdraw " water . Drinkin g wate ri s a majo rsourc e o flea d exposur e amon g man yinfant s whil e the yar e dependen to n bab yformula s durin g thei rfirs t year , as wel l as youn g children
. EPA' s Offic e o fDrinkin g Wate rwil l soo n propos e revisin g th e existin g lea d standar d o f5 0 pg/ Lt o 5 pg/L , measure d a tth e treatmen tplant , wit h a "no-actio n level " averag e o f1 0 pg/L , measure d a tth e home tap . Estimate d contribution s tha tnatural , atmospheri can d solde rlea d mak e t o tota l lea d exposur e vi a drinkin g wate ran d tota l die tar e addresse d i n th e modelin g approache s presente d i n Section s I Van d V
. F
. Lead i n Pain t

Ingestio n o flead-containin g pain ti s considere d t o b e th e mos t frequen tcaus e o fsever e lea d intoxicatio n amon g childre n (Chisolm , 1984 ; CDC , 1985)
. Significan tcorrelation s hav e bee n foun d betwee n th e quantit y an d conditio n o flea d painte d surface s i n home s an d bloo d an d feca l lea d level s i n inne rcit ychildre n (Urban , 1976 ; CD , pp . 11-15 6 t o 11-160)
. Significan t difference s i n bloo d lea d level s hav e bee n foun d i n relatio n t o housin g conditio n amon g childre n as youn g a s nin e months , wit h highes t level s i n childre n livin g i n deterioratin g pre-Worl d WarI I housing , intermediat e level s i n well-maintaine d an d rehabilitate d olde rhousing , an d lowes tlevel s i n childre n i n publi chousin g an d newe runit s fre e o flea d pain t(Clar k e t al. , 1984)
. Othe rinvestigation s indicat e tha t i n additio n t o peelin g lead-base d paints , "intact " lead-base d pain tcontribute s t o elevate d bloo d lea d level s i n childre n vi a chalkin yo rweatherin g (Gilber te tal. ,P.2 3
11-1 4 1979 ; Galk e e tal. , 1975)
. Furthe rrisk s ar e associate d wit h conventiona l pain tremova l technique s (i.e. , sanding , burnin g hea tguns ) whic h ca n generat e concentration s o ffin e lea d dus tu p t o 10 0 pg/m 3 (NIBS , 1988)
. Unde rth e 197 1 Lead-Base d Pain tPoisonin g Preventio n Act , whic h ha s sinc e bee n amended , th e Departmen to fHousin g an d Urba n Developmen tha s regulator yan d researc h responsibilitie s fo reliminatin g th e hazard s o f lead-base d pain tpoisonin g i n federall yfunde d housing
. I n 1977 , th e Consume rProduc tSafet yCommissio n banne d as hazardous , househol d pain t (includin g to yan d furnitur e paint ) containin g mor e tha n 0.06 % lead
. Thi s wa s a n importan tste p bu ti tdoe s no taffec thazard s pose d b ylead-base d paint s alread ypresen to n ol d housin g surfaces
. Prio rt o 1940 , som e interio r paint s containe d mor e tha n 50 % (500,OO U ppm ) lead
. Use o flea d piymen t paint s decline d slowl ybetwee n 194 0 an d th e late
. 196U' s afte rwhic h i t decline d a ta rapi d rat e (NAS , 1972)
. Pop e (1986a ) estimate s tha ti n 1980 , th e interio rand/o rexterio rsurface s o fbetwee n 21. 5 an d 47. 3 millio n household s i n th e U.S. , mostl ybuil tbefor e 1960 , containe d greate rtha n 0. 7 mg/cm^

lea d i n painte d surfaces , a leve l considere d hazardou s t o youn g childre n b yth e Center s fo rDiseas e Contro l (CDC)
. Betwee n 6. 2 an d 13. 6 millio n childre n unde rth e ag e o f7 ar e estimate d t o hav e reside d i n lead-base d painte d housin g i n 198 0 (Pope , 1986a)
. Eve n i fcoate d wit h lo wlevel-leade d paint , th e underlyin g layer s o flead-base d pain ti n olde rhome s represen t a larg e reservoi ro flea d exposur e i n children , particularl yi fther e i s peelin g paint , broke n o rcracke d plaster , o rhole s i n th e walls
. Th e numbe ro flead-base d painte d home s wit h thes e deterioratin g condition s (i.e. , "unsound" ) i n 198 0 i s estimate d t o hav e bee n betwee n 800,00 0 t o 2. 9 millio n wit h approximatel y235,00 0 t o 842,00 0 childre n unde rag e 7 livin g i n suc h home

s (Pope , 1986a)
.P.2 4
11-1 5 Lead-base d pain tcontinue s t o b e th e majo rsourc e o fhigh-dos e lea d exposur e an d symptomati clea d poisonin g fo rchildre n i n th e U.S
. (Chisolm , 1971 ; CDC , 1985) , an d i tappear s tha texposur e t o lead-base d pain twil l continu e t o b e a proble m fo rdecade s t o com e (Schneide ran d Lavenhar , 1986)
. Betwee n 197 3 an d 1980 , onl y10 % o fpre-194 0 housin g unit s an d 5 % o f housin g unit s buil ti n th e 194 0 ' s had bee n remove d fro m ou rnation' s housin g stoc k bydemolition , disaster , o rbyothe rmean s suc h as conversio n t o commercia l spac e (Burea u o fth e Census , 1983)
. Les s tha n hal fo fthes e unit s remove d fro m servic e wer e locate d i n centra l cit yarea s wher e lea d poisonin g i s mos tprevalent
. I n addition , poo rurba n familie s ofte n hav e n o choic e bu tt o liv e i n poorl ymaintaine d olde rhousin ybecaus e th e vas t majorit yo fne

whousin g unit s create d fro m 197 3 t o 198 0 i s locate d outsid e o fcentra l cit yareas , an d acut e shortage s o fmoder n an d lead-free , lo w incom e renta l unit s exis ti n man ycitie s (Farfel , 1985)
. Hig h exposure s t o lea d i n childre n livin g i n olde rhousin g wit h flakin g o rintac tpain twil l no tb e significantl yinfluence d byan ychange s i n atmospheri clea d emissions
. Childre n wit h pic a fo rpain tchip s o rother s livin g i n deterioratin g lead-base d painte d home s wh o ar e excessivel yexpose d t o pain tlead-contaminate d dus tthroug h norma l han d t o mout h activit y canno tb e expecte d t o b e protecte d byan ylea d NAAQ S n o matte rho

wstringent
. Fo rthi s reaso n an d becaus e exposur e t o pain tlea d i s s o highl yvariable , n o attemp twil l b e mad e her e t o quantitativel yestimat e exposure s o fchildre n wh o ar e excessivel yexpose d t o lead-base d pain tunde rvariou s ai rlea d levels , as i s don e fo rothe rexposur e media
. I ti s clea rtha tan yexposure s an d bloo d lea d level s predicte d fo rchildre n unde rvariou s ai rlea d level s usin g th e approache s i n Sectio n II I wil l b e siynificantl yhighe rfo rchildre nP.2 5
11-1 6 

### wit h hig h pain tlea d exposure . Comprehensive plan s fo rsaf e and effectiv e remova l o flead-base d paint s fro m ol d housin g nee d t o b e develope d and im plemented , otherwis e pediatri cplumbis m wil l persis t unti l muc h o fth e presen t housin g stoc k

i s completel yrehabilitate d o rdemolishe d (Chisolm , 1986)
. Preventin g excessiv e exposure t o existin g source s o flea d i n and aroun d housin g mus

tb e addresse d b

ya n appropriat e combinatio n o flegislation , housin g cod e inspectio n and enforcement , financia l incentives , parenta l education , and othe rprograms .P.2 6

'III
. ESTIMATIN G LEA D EXPOSURE

S AN D BLOO D LEA D LEVEL S A
. Alternativ e Modelin g Approache s T o asses s th e healt h risk s associate d wit h alternativ e ai rlea d standards , i ti s necessar yt o estimat e th e bloo d lea d (PbB ) level s tha t woul d b e distribute d i n th e population(s ) o fconcer n unde rvariou s ai rlea d concentrations
. [Th e amoun to flea d measure d i n whol e bloo d i s a n inde xo f th e rapidl ydiffusibl e fractio n o fth e tota l bod yburde n o fabsorbe d lea d an d i s generall yuse d as th e dosage , o rinde xo fexposure , i n investiyatin y th e variou s human healt h effect s associate d wit h lead. ] Lea d exposur e occur s throuy h multipl e medi a bu tunfortunately , lonyitudina l assessment s o f simultaneou s multi-medi a exposure s hav e no tye tbee n made
. Potentiall y usefu l longitudina l analyse s ar e no wbein g carrie d ou tas par to fth e Cincinnat i Lea d Progra m Projec t(Clar k e tal. , 1987)
. Thre e approache s . ar e examine d her e tha tca n b e use d t o estimat e o rpredic tth e impac to finhale d an d ingeste d lea d aerosol s an d compound s o n th e bod yburde n o flea d a s indexe d bybloo d lead
. Thes e approache s ar e presente d in.detai l i n Section s I Van d Vfo rconsideratio n fo rusin g one , two , o ral l thre e i n assessin g th e protectio n provide d byalternativ e lea d NAAQS
. Th e firs tapproach , discusse d i n Sectio n IV , i s t o us e measure d rate s o fabsorption , o r"uptake " o flea d throug h differen tpathway s (e.g. , inhalation , ingestion ) fro m experimenta l studie s togethe rwit h availabl e mathematica l ("biokinetic" ) model s fro m lea d balanc e studie s t o projec teithe rtota l bod yburde n o rth e amoun to flea d i n an yo fth e presume d "physiological " kineti ccompartment s (e.g. , blood , sof ttissue , bone ) a t an ytime
. Th e secon d approach , referre d t o as a n "aggregate " model , i s t o directl yappl ya mathematica l relationshi p betwee n ai rlea d an d bloo d lea d derive d fro m communit yepidemiologica l studie s tha treflect s bot h direc t

### III- 2

inhalatio n exposur e an d indirec texposure s vi a secondar ydepositio n pro cesses . Th e thir d approach , referre d t o as a "disaggregate " model , i s a hybri d o fth e firs ttw o i n whic h separat e empirica l relationship s betwee n bloo d lea d an d lea d intak e fro m lea d i n air , food , water , dust , soil , availabl e fro m experimenta l exposur e an d epidemiologica l studie s o fdifferen t populations , ar e applie d t o lea d concentratio n estimate s i n differen t media
. Th e natur e o fth e relationship s detecte d betwee n lea d concentration s i n bloo d an d variou s environmenta l media , an d th e merit s an d limitation s i n usin g empirica l relationship s t o represen tlea d exposur e throug h multipl e pathway s i n thes e latte rtw o approaches , wil l b e discusse d i n Sectio n V
. B
. Calculatin g Bloo d Lea d Distribution s Aroun d Predicte d Mean s Becaus e mos to fth e dat a inpu tt o thes e model s ar e generall yaverag e estimates , al l thre e model s estimat e PbB level s i n term s o fpopulatio n mean levels
. Th e distributio n o fPb B level s i n U.S
. childre n i s broa d becaus e ther e i s a distributio n o fexposure s thos e childre n face , a distributio n o f behavio rpattern s tha taffec tth e uptak e o ftha texposure , an d a distributio n o fbiologica l absorptio n an d excretio n rates . Fo rpurpose s o fsettin g a lea d NAAQS , i ti s necessar yt o determin e th e entir e bloo d lea d distributio n correspondin g t o a give n mean PbB fo rdifferen tpopulation s s o that , fo r example , percentage s o findividual s exceedin g PbB level s o fconcer n ca n b e ascertained
. Determinin g suc h distribution s i s a n attemp tt o accoun tfo r th e significan tbehaviora l an d biologica l variabilit ywithi n populations
. I ti s th e grou p o findividual s wit h th e potentiall ygreates tadvers e respons e t o an ygive n lea d exposur e tha tar e o fgreates tconcer n i n establishin g a primar ylea d NAAQS
. A s note d fo rothe rmetal s i n tissue s o fhuman populations , th e distributio n o fPb

B level s fo ran yrelativel yhomogeneou s populatio n closel yP.2 8 III- 3 follows. a lognorma l distributio n (CD , Sectio n 11.3.4)
. Alognorma l distributio n i s completel yspecifie d b yit s geometri cmea n an d geometri cstandar d deviation
. I ti s possible , therefore , t o calculat e percentile s o fa bloo d lea d distributio n (e.g. , media n o r9 9 percentile ) aroun d a mean Pb B leve l b yusin g th e geometri c standar d deviatio n (GSD) o ftha tpopulation' s bloo d lea d distribution
. Severa l epidemiologica l studie s hav e indicate d tha tth e lo g value s o fmeasure d individua l Pb

B level s i n a uniforml yexpose d populatio n ar e normall ydis - tribute d wit h a variation , includin g analytica l variation , rangin g betwee n 1. 3 an d 1.4 , whe n expresse d as a GS D (Teppe ran d Levin , 1975 ; Aza re t al. , 1975 ; Billic k

e tal. , 1979)
. Th e NHANE S I I stud yprovide s th e bes tavailabl e dat a o n nationwid e bloo d lea d level s i n term s o fqualit ycontro l an d sampl e size
. I n regressio n analyse s o fthes e data , Schwart z (1985a ) estimate d a GS D o f1.42 8 fo ryoun g childre n afte rremovin g th e varianc e i n Pb B level s attributabl e t o ai rlea d exposur e b yadjustin g every individual' s Pb

B leve l t o wha ti twoul d b e a tzer o ai rlead , whil e allowin g fo rvariation s i n backgroun d non-ai rlea d exposure . Afte rexcludin g fro m th e analysi s childre n wit h Pb B level s abov e 4 0 pg/dl , wh

o woul d no tb e expecte d t o be substantiall yaffecte d b ychange s i n th e lea d NAAQ

S (fo rexample , becaus e o fhighe rtha n averag e pic a activit y o rthos e expose d t o excessivel yhig h concentration s o flea d i n paint) , Schwart z (1985b ) reapplie d th e same techniqu e an d calculate d a GS D o f 1.419 . Thus , a GS

D withou tattributio n o fan ysourc e o flea d exposur e excep tgasolin e lea d an d industria l ai rlea d emission s ma ybe take n a

s a rounded-of fvalu e o fapproximatel y1.4 2 fo rth e NHANE S I I populatio n o f childre n (CD , p . 11-31)
. Give n tha tth e focu s o fthi s exposur e analysi s i s o n population s livin g nea rlea d poin tsource s where bloo d lea d variabilit yma ybe differen tcompare dP.2 9 

### III- 4 t o th e tota l mi xo fU.S
. children , a separat e assessmen to fbloo d lea d GSD' s fo rsuc h population s i s presente d here
. Publishe d statistic s o fPb B sample s nea rvariou s lea d poin tsource s hav e bee n assemble d an d analyze d i n Cohe n (1986 ) an d Marcu s (1988a)
. Th e GSD s calculate d fro m thes e point source/bloo d lea d survey s ar e liste d i n Tabl e 3-1 , alon g wit h th e NHANE S I I GS D fo rchildren
. T

o differen tdegrees , th e primar yorigi n o fnon-biologica l variatio n i n lea d exposur e fo rthes e poin tsourc e population s wa s th e smelter , especiall yi n th e Roel s an d Yanke l studie s conducte d whe n smelte remission s wer e considerabl yhigher
. I ti s possibl e tha tchildre n wit h exposur e t o a single , intens e sourc e o flea d ma yhav e relativel ylo wvariabilit y (essentiall yonl ydu e t o intrinsi cbiologi cvariability ) wit h a hig h mean bloo d lead
. Th e mos trecen tstud yindicate s a large rvarianc e a t relativel ylowe rexposur e level s nea rth e Montan a smelte rsurveye d i n 1983 , suggestin g tha tmultipl e origin s wit h separat e variabilit yma yb e presen t rathe rtha n a singl e predominan tsourc e o fvariabilit yi n lea d exposur e (Marcus , 1988a)
. Th e selectio n o fa GS D valu e t o mode l population s livin g nea rvariou s lea d poin tsource s i n th e futur e depend s o n assumption s regardin g varianc e i n exposur e i n th e future
. Perhap s th e mos trelevan tdat a ar e fro m th e 198 3 CD C E
. Helena , Montan a stud ysinc e the yreflec tth e mos tcontemporar y conditions
. I tca n b e expecte d tha teve n fo rthi s population , however , tota l lea d exposur e wil l hav e droppe d substantiall yby1990 . Thi s i s attributabl e t o recen tan d continuin g downward trend s i n lea d level s i n canne d foods , th e nationwid e ba n o n lea d solde ri n ne wconstructio n an d plumbin g repairs , th e lead-in-gasolin e phasedown , an d perhap s increasin g publi cawarenes s regardin g th e danger s o flea d exposur e an d effectiv e avoidanc e measures . Al l o fthes e change s shoul d resul ti n no tonl ylowe rmean baselin e PbB levels , bu tperhap sP.3 0 | : i 1 , 

### II1- 5
TABLE 3-1 . COMPARISO N O F ESTIMATE D GSD

s ACROS S SEVERA

LSTUDIE S Mean Pb B Estimate d Population/Referenc e (pg/dl ) GSD l NHANE S I I - tota l mi xo f16. 0 1.4 2 childre n 1- 5 year s ol d (Schwartz , 1986b ) 11-yea rold s livin g nea rBelgia n 21. 7 1.2 9 primar ylea d smelte r(Roel s e tal. , 1980 ) 1- 9 yea rold s livin ynea rIdah o 56. 5 1.3 2 primar ylea d smelte r(Yanke l e tal. , 1977 ) 1- 5 yea rolds , closes tt o 3 non-ferrou s 15. 6 1.3 9 smelter s i n U.S
. (Hartwel l e tal. , (median ) 

### 1983 ) 1- 5 yea rolds , livin g nea rMontan a 9. 4 1.5 3 primar ylea d smelte r(CDC , 1983 ) 1- 5 yea rold s livin yi n 3 Missour i 16. 2 1.5 7 smelte rtown s (Bake re tal. , 1977 )
!GS D calculation s describe d i n Cohe n (1986 ) an d i n Marcu s (1988a)
.P.3 1 

### III- 6
mor e importantly , i n fewe rhig h leve l exposur e situation s an d therefor e les s varianc e i n Pb

B levels
. Quantifyin g suc h a n effec tt o estimat e a futur e GS D valu e i s difficult
. I ti s likely , however , tha tfutur e reduction s i n baselin e "non-poin tsource " lea d exposure s wil l resul ti n a reductio n i n exposur e varianc e s o tha tth e bloo d lea d GS D wil l b e mor e reflectiv e o fintrinsi c biologi cvariance , suc h as tha tfoun d i n th e Roel s an d Yanke l studies
. Althoug h thes e latte rstudie s wer e conducte d durin g time s o fmuch highe rexposures , th e exposure s wer e dominate d byhig h smelte remission s an d soil/dus tcon tamination , resultin g i n relativel ylo wPb B variability
. Fo rpurpose s o f modelin g futur e exposure s amon g childre n livin g nea rdifferen tlea d poin t sources , a rang e o fGS D value s ca n b e considered : a lowe rboun d o fapproximatel y 1.3 0 derive d fro m th e Yanke l e tal
. an d Roel s e tal
. studie s an d a n uppe r boun d GS

D valu e o f1.5 3 derive d fro m th e 198 3 CD C stud yo fE
. Helena , Montan a children
. Th e midpoin to fthi s rang e i s 1.42 , whic h coincidentall y i s identica l t o th e NHANE S I I GS D estimate
. Unti l additiona l dat a ar e available , a rang e o f1.30-1.5 3 wil l therefor e b e assume d fo rchildre n livin g nea rlea d poin tsource s as a reasonabl e rang e o fGS D values , an d th e midpoin t o f1.4 2 wil l b e assume d as a reasonabl e bes testimate
. Sinc e bloo d lea d estimate s wil l als o b e mad e fo rpregnan twomen an d middle-age d men , GS D value s fo radul tbloo d lea d distribution s ar e needed
. Ther e i s littl e informatio n o n adul tbloo d lea d GSD s fro m poin tsourc e studies
. Th e mos tcomplet e dat a bas e i s clearl yfro m NHANE S II , whic h ha s bee n analyze d i n th e C D t o yiel d a rang e o fGS D values , dependin g o n rac e an d plac e o fresidence , betwee n 1.3 4 t o 1.3 9 fo radul twomen an d 1.3 7 t o 1.4 0 fo radul tmen (CD , Tabl e 11-9)
. Give n th e uncertaintie s i n extrapolatin g thes e range s t o adul tpopulation s livin g nea rpoin tsource s unde rfutur e exposur e scenarios , a midpoin tvalu e o f1.3 7 wil l b e chose n as a reasonabl eP.3 2
III- 7 estimat e fo r bot hadul t me n an d women . Analytica l variatio n whic hexist s i n an ymeasuremen t ha s a n impac t o n th e bia s and precisio n o f statistica l estimate s suc ha s th e GSD s derive d fro mth e studie s discusse d here . Fo r thi s reason , i t i s importan t t o recogniz e th e magnitud e o f analytica l variatio n i n bloo d lea d measurement s du e t o measuremen t variatio n (i.e. , betwee n measurement s ru n a t th e sam e time ) and variatio n create d b yanalyzin g bloo d sample s a t differen t time s (CD , p . 11-29) . Fo r example , correctin g th e GSD s fo r homogeneou s subpopulation s o f childre n (1.3 4 - 1.39 ) fo r th e overal l estimat e o f analytica l variatio n fo r th e NHANE S I I stud yyield s estimate d GSD s in th e rang e o f 1.2 9 t o 1.34 . Usin g GSD s correcte d i n suc ha way , althoug hprovidin g a mor e accurat e characterizatio n o f a give n bloo d lea d distribution , ma yno t b e appropriat e fo r thi s assessmen t becaus e th e healt heffect s studie s tha t wil l b e use d t o defin e dose-respons e relationship s di d no t correc t thei r Pb B measurement s fo r analytica l variance . Thes e studies , lik e NHANE S I I an d th e othe r poin t sourc e epidemiologica l surveys , generall yemploye d th e bes t availabl e measuremen t technique s and qualit ycontrol . Usin g "corrected " GSD s o n on e han d t o predic t th e distributio n o f children' s Pb B level s aroun d a mea n populatio n PbB , and the n matchin g thos e predicte d Pb B level s wit h"uncorrected " Pb B level s derive d fro m healt hstudie s i n orde r t o asses s th e risk s associate d wit htha t populatio n mea n PbB , woul d resul t in a somewha t biase d assessment . Therefore , th e rang e o f GSD s presente d abov e tha t ar e no t correcte d fo r analytica l varianc e wil l b e use d in furthe r calculations . Tabl e 3- 2 present s bloo d lea d distribution s associate d wit hexampl e populatio n mea n Pb B level s calculate d usin g th e GS D value s derive d above .P.3 3 

### II1- 8
Thes e distribution s wer e calculate d usin g th e formul a give n t o describ e a lognorma l distributio n (Yanke l e t al. , 1977) : Mg • GSD n

### = Dn where : M y= geometri c mea n Pb B GS D = geometri c standar d deviatio n n = th e numbe r o f standar d deviation s Dn = valu e o f PbB a t n standar d deviation s

TABL E 3-2 . ILLUSTRATIV E BLOO D LEAD DISTRIBUTION S ASSUMIN G DIFFEREN T MEA

NBLOO D LEAD S AND GEOMETRI C STANDAR D DEVIATION S

GS D 1.3 7

1.4 2 

### Geometri c

Mea n Pb B 4 5 6 7
4 5 6 7 90t h

6. 0 7. 5 9. 0 10. 5
6. 3 7. 8 9. 4 11. 0 

### Percenti l

95t h 6. 7 8. 4 10. 1 11. 7
7. 1 8. 9 1U. 7 12. 5 

### e 99t h

8. 3 10. 4 12. 5 14. 6
9. 0 11. 3 13. 6 15. 8 99.5t h

9. 0 11. 3 13. 5 15. 8
9. 9 12. 3 14. 8 17. 3P.3 4

,IV
. INTEGRATE D LEA D UPTAKE/BIOKINETI C MODE L Th e "uptake/biokinetic " modelin g approac h attempt s t o accoun tfo rth e following : a ) th e amoun to flea d i n th e bod ya t an yon e tim e i s th e produc t o fdynami cinteraction s o fpartiall yoffsettin g processe s o fabsorption , distribution , storage , mobilization , an d excretion ; b ) thes e processe s var y wit h th e rout e an d rat e o fexposure , a person' s age , nutritiona l an d healt h status , an d baselin e exposure ; c ) uptak e fro m al l source s b yal l absorptio n route s ca n b e separatel ymodeled , thu s providin g a n estimat e o fth e relativ e importanc e o fatmospheri clea d exposure , eithe rdirectl yo rindirectly , t o tota l bod yburden ; an d d ) pas tan d futur e trend s i n environmenta l lea d level s du e t o differen tcontro l effort s an d regulations
. Ther e hav e bee n severa l studie s measurin g th e intake , uptake , an d metabolis m o flea d i n adul tmal e volunteers , fro m whic h balanc e scheme s hav e bee n constructe d (Kehoe , 1961 ; Chamberlai n e tal. , 1978 , Rabinowit z e tal. , 1976 , 1977)
. B

ymakin g estimate s abou tlea d intake s an d variou s metaboli c factors , balanc e scheme s ca n b e constructe d fo rdifferen tgroup s wit h differen texposure s t o lea d t o asses s th e importanc e o fspecifi cexposur e factor s unde rvariabl e condition s (e.g. , alternativ e lea d NAAQS , phaseou t o flea d i n soldere d can s an d i n gasoline)
. Pre-schoo l ag e childre n (<

_6 year s old) , pregnan twomen (a s exposur e surrogate s fo rth e fetus) , an d adul tmen (40-5 9 year s o fage ) ar e specifie d i n th e C D as particularl y sensitiv e t o lead
. Ofthes e groups , childre n betwee n 2 an d 3 year s ol d experience , i n general , th e highes tbloo d lea d level s (Mahaffe ye tal. , 1982 ; Billic k

e tal. , 1979) , mos tlikel ydu e t o thei rgreate rhand-to-mout h activit yas wel l as t o variou s metaboli cprocesse s (Harle yan d Kneip , 1985)
. T

o predic texposur e impact s o falternativ e ai rlea d standards , mode l balanc e scheme s hav e bee n devise d fo rchildre n age d 0- 6 year s an d ar e discusse d below
.P.3 5 IV- 2 Alac k o fadequat e biokineti cdat a fo rpregnan tfemale s prevent s suc h modelin g fo rth e fetus
. I n addition , accurat e biokineti cmodelin g o fth e sensitiv e populatio n o fadul tmale s woul d requir e a tleas t4 0 year s o f cumulativ e exposur e inputs
. Suc h uptak e modelin g woul d b e difficul tgive n th e grea tvariabilit yi n exposur e historie s amon g U.S
. adult s an d th e paucit y o fdata
. Exposur e modelin g fo rpurpose s o fris k estimatio n fo rpregnan t female s an d adul tmales , discusse d i n Sectio n V.A. , wil l rel yo n applyin g air : bloo d lea d "disaggregated " relationship s t o estimate d baselin e "non-air " bloo d lea d levels
. Adiscussio n o flead' s absorption , excretion , retention , an d distributio n withi n th e bod yunde rdifferen texposur e an d physiologica l condition s i s necessar ybackgroun d t o th e uptake/biokineti cmodel , an d i s provide d i n Chapte r1 0 o fth e CD
. A s wil l b e furthe rdiscussed , applicatio n o fthi s o ran ylea d exposur e mode l mus trecogniz e th e limitation s o fth e availabl e dat a an d th e significan tvariability , amon g population s i n thei rbehavioral , exposure , an d physiologica l characteristics
. Fo rpresen tpurposes , th e childre n t o b e considere d i n th e mode l d o no tinclud e th e whol e U.S
. population ; the ycompris e group s wit h differen texposure s t o lead , som e o fthe m extreme , i n orde rt o illustrat e th e variation s i n lea d exposur e an d absorptio n aroun d lea d poin tsource s unde rdifferen tscenarios
. Sectio n IV. Apresent s methodologie s t o estimat e averag e dail ylea d uptak e fro m al l exposur e source s unde ralternativ e ai rlea d levels
. Sectio n IV. B present s methodologie s t o relat e thes e estimate s o flea d uptak e t o average , steady-stat e bloo d lea d levels
. Althoug h thi s approac h predict s hypothetica l outcome s an d th e absolut e numbers shoul d no tb e use d uncritically , th e mode l doe s striv e t o us e th e availabl e data , wit h al l it s limitations , t o th e fulles texten t possibl e t o provid e a usefu l too l i n eventuall ydistinguishin g th e healt h impact s o falternativ e lea d NAAQS
.P.3 6 IV- 3 A
. Estimate s o fLea d Uptak e Th e metho d employe d t o estimat e th e deyre e t o whic h eac h environmenta l sourc e o flea d contribute s t o a child' s tota l dail ylea d uptak e i s base d o n th e distributio n o fambien tai rlea d level s tha twoul d b e allowabl e o r expecte d unde reac h standar d considered , probabl e exposur e condition s wit h respec tt o othe rexposur e medi a suc h as foo d an d dust , an d averag e biologica l absorptio n rate s fo reac h exposur e route . Th e metho d consist s o fa four-ste p process : 1 ) definitio n o fambien tconcentration s o flea d fo rmajo rexposur e source s (i.e. , air , food , water , soil , dust) ; 2 ) determinatio n o fdail ylea d intak e accordin g t o th e relationship :

. I- i = C-

j •[Pbj- j wher e I-

j i s th e dail ylea d intak e fro m sourc e i , C- j i s th e ingestio n o r inhalatio n (i.e. , consumption ) pe rdayo feac h lea d sourc e i an d [Pb]- j i s th e concentratio n o flea d i n eac h sourc e i-j ; 3 ) calculatio n o fth e amoun to flea d absorbe d fro m eac h exposur e sourc e i : U i = I i ' A i wher e U-

j i s lea d uptak e fo reac h exposur e sourc e i , I- j i s th e dail ylea d intak e fro m eac h sourc e i , an d A- j i s th e percen tabsorptio n o flead , vi a th e appropriat e exposur e rout e fo rth e particula rsource ; an d 4 ) calculatio n o fth e tota l lea d uptak e fro m al l sources , U u : U u = E (I i •A ^ Th e wa ydail ylea d uptak e woul d b e calculate d i s illustrate d i n Tabl e 4- 1 fo r2-yea rol d childre n livin ynea r(withi n 2- 5 km ) a lea d poin tsource . Detail s o fth e mode l parameter s an d th e line-by-lin e estimates , alon ywit hTABLE 4-1 . ESTIMATE D 199 0 AVERAGE LEA D INTAKE AND UPTAK E I N 2-YEA R OL

D CHILDRE N UNDE R AVERAGE AI R LEA

D LEVELS 1 0.2 5 pg/m 3 0. 5 pg/m 3 0.7 5 pg/m 3 1. 0 pg/m 3 1.2 5 pg/m 3 1. 5 pg/m 3 0.2 5 0. 5 0.7 5 1. 0 1.2 5 1. 5 1 . Outdoo rai rlea d (pg/m 3 ) _.. - 2 . Indoo rai rlea d (pg/m 3 ) .0 8 0.1 5 0.2 3 0. 3 0.3 8 0.4 5 3 . Tim e spen toutdoor s (hours/day ) 2- 4 2- 4 2- 4 2- 4 2- 4 2- 4 4 . Tim e weighte d averag e (pg/m 3 ) .09-.1 1 .18-.2 1 .27-.3 2 .36-.4 2 .45-.5 4 .b4-.6 3 5 . Volum e o fai rrespire d (m 3 /day ) 4- 5 4- 5 4- 5 4- 5 4- 5 4- 5 6 . Lea d Intak e fro m ai r(pg/day ) 0.4-0. 6 0.7-1. 1 1.1-1. 6 1.4-2. 1 1.8-2. 7 2.2-3. 2 7 . % deposition/absorptio n i n luny s 4 2 42 4 2 42 4 2 4 2 8 . Tota l lea d uptak e fro m lung s 0.2-0. 3 0.3-0. 5 0.5-0. 7 0.6-0. 9 0.8-1. 1 0.9-1. 3 (py/day ) 9 . Dietar yLea d Consumptio n (py/day ) a ) fro m solde ro rothe rmetal s b ) atmospheri clea d c ) natura l lead , indirec t atmos pheric , undetermine d source s 10 . % absorptio n i n yu t 1 1 . Dietar ylea d uptak e (py/day ) 12 . Stree tdust/soi l lea d (pg/g ) 13 . Indoo rdus tlea d (pg/g ) 14 . Tim e weighte d averag e (pg/g ) 15 . Amoun to fdir tingeste d (g/day ) 16 . Lea d intak e fro m dir t(pg/day ) 17 . %dir tlea d absorptio n i n gu t 18 . Lea d uptak e fro m dir t(pg/day ) 19 . Tota l lea d uptak e fro m lun g an d yu t(pg/day ) Assumption s an d calculation s ar e describe d i n Appendi xAbyro wnumber
. Refer s t o childre n livin ynea ron e o rmor e lea d poin tsource s an d unaffecte d bylea d pain tchildre n livin g i n typica l urba n o rrura l environment s remot e fro m lea d poin t source s ca n b e modele d usin yth e sam e uptak e calculation s an d substitutin g paramete rvalue s wher e difference s are.note d i n Appendi xA
. 

### 4. 0 1. 2 3. 6 42-5 3 3.7-4. 7 160-24 0 250-36 0 220-34 0 .08-.13 5 17.6-45. 9 

### 2 5 4.4-11. 5 8.3-16. 5 

### 4. 0

1. 2 3. 6 42-5 3 3.7-4. 7 250-47 0 440-67 0 377-63 7 .08-.13 5 30.1-86. 0 

### 2 5 7.5-21. 5 11.5-26. 7 

### 4. 0

1. 2 3. 6 42-5 3 3.7-4. 7 325-72 0 615-101 0 518-96 2 .08-.13 5 41.5-129. 8 

### 2 5 10.4-32. 5 14.6-37. 9 

### 4. 0

1. 2 3. 6 42-5 3 3.7-4. 7 405-97 5 785-135 5 658-129 2 .08-.13 5 52.7-174. 3 

### 2 5 13.2-43. 6 17.5-49. 2 

### 4. 0

1. 2 3. 6 42-5 3 3.7-4. 7 500-120 5 950-170 0 800-161 8 .08-.13 5 64.0-218. 4 

### 2 5 16.0-54. 6 20.5-60. 4 

### 4. 0

1. 2 3. 6 42-5 3 3.7-4. 7 570-149 0 1120-205 0 937-195 7 .08-.13 5 74.9-264. 2 

### 2 5 18.7-66. 0 23.3-72. 0 M

< | -P -P.3 8 IV- 5 limitation s o fth e availabl e dat a base , ar e discusse d i n Appendi xA
. Fo r comparativ e purposes , childre n livin g i n area s generall yunaffecte d b y stationar ylea d emission s ca n als o b e modele d usin g mos to fth e sam e paramete r values ; exception s (indoor/outdoo rparticle d penetratio n rates , respirator y depositio n rates ) ar e note d i n Appendi xA
. Dus tan d soi l lea d level s associate d wit h give n ai rlea d concentration s woul d diffe rsubstantiall y betwee n poin tan d non-poin tsourc e areas ; thi s to o i s briefl ydiscusse d i n Appendi xA
. Th e followin g point s ar e importan tt o conside rwit h regar d t o th e uptak e calculation s i n th e table : 1 ) th e calculation s d o no trepresen t population-wid e exposur e scenario s unde ralternativ e standards , onl yexposur e fo r th e specifie d ai rlea d concentrations
. Ambien tlea d level s aroun d a poin t sourc e meetin g a give n lea d NAAQ S var ydependin g o n distance , topography , win d spee d an d direction , plan toperatin g parameters , emission s controls , particl e size s an d depositio n rates , etc . Ai rqualit ydispersio n modelin g tha taccount s fo rthes e factor s wil l b e use d i n th e actua l cas e stud yanalyse s t o assig n ai rlea d concentration s unde ralternativ e standard s t o differen t "receptor " point s wher e peopl e liv e aroun d th e lea d poin tsources ; 2 ) th e estimate s i n th e tabl e appl yt o 2-yea rol d childre n t o illustrat e th e perio d o fmaximu m exposure . Bloo d lea d level s estimate d byth e biokineti cmode l (discusse d below ) accoun tfo rcumulativ e exposur e throughou tchildhood , no tjus ta singl e year. . I ti s necessary , therefore , t o mak e age-specifi c exposur e estimate s tha treflec tchange s i n behavio ran d metabolis m as a chil d ages . Age-specifi cexposur e estimate s ar e als o discusse d i n detai l i n Appendi xA ; an d 3 ) th e genera l type s o fexposur e environment s considere d her e d o no tinclud e olde rhome s wit h lead-base d pain thazards
. Suc h condition s ar e discusse d a tth e en d o fAppendi xAt o illustrat e th e severit yo flead-pain t hazard s compare d t o othe rexposures .P.3 9 IV- 6 B
. Uptak e an d Bloo d Lea d Concentratio n To estimat e bloo d lea d (PbB ) level s unde rdifferen texposur e scenarios , severa l differen tkind s o fstudie s ca n b e use d t o deriv e a relationshi p betwee n absorbe d lea d (o rlea d uptake ) an d bloo d lead
. Availabl e studie s includ e populatio n survey s i n whic h th e bloo d lea d concentratio n o f individual s o rgroup s i s correlate d wit h measure d lea d concentration s i n air , food , water , soil , o rdust ; experiment s i n whic h volunteer s ar e expose d t o controlle d ai rlea d concentration s an d thei rPbB level s measured ; an d lea d balanc e studies , o findividual s wit h measure d lea d intakes
. Th e mos t relevan texperimenta l studie s includin g thos e o n adult s fo rcomparativ e purposes , ar e discusse d her e alon g wit h description s o fth e analyse s use d t o deriv e uptake/Pb B relationships
. Relationshi p betwee n bloo d lea d an d environmenta l lea d concentration s fro m populatio n survey s ar e discusse d as par to fth e aggregat e an d disaggregat e model s i n Sectio n V
. 1 . Dietar yLea d Ingestio n Studie s i n Infant s Studie s tha thav e measure d dietar ylea d intak e concurrentl ywit h Pb B level s amon g infant s an d toddler s ar e compare d i n th e criteri a documen t (CD , Tabl e 11-49)
. Althoug h precis e estimate s o fdietar ylea d consumptio n ca n no tb e made , thes e studie s (U.K
. Centra l Directorate , 1982 ; Lace y e tal. , 1985 ; Sherloc k e tal. , 1982 ; Ryu e tal. , 1983 ) hav e severa l advantages : 1 ) carefu l contro l an d analysi s o fdietar yintake ; 2 ) minima l lea d exposur e t o source s othe rtha n th e die ta s th e stud ypopulatio n (infants ) i s relativel y immobile ; an d 3 ) intake/bloo d lea d relationship s ca n b e use d t o estimat e th e impac to ftota l lea d exposur e (i.e. , fro m al l sources ) o n bloo d lea d becaus e trace rstudie s (Chamberlai n e tal. , 1978 ; Rabinowit z e t al. , 1976 ) sho wn o difference s i n th e distributio n o flea d t o tissue s whethe rtake n u p fro m lun g o rgut .P.4 0 IV- 7
Bot h th e U.K
. Centra l Directorat e an d th e Sherloc k e tal
. studie s involve d infant s wit h relativel yhig h PbB level s an d hig h intakes
. I ti s wel l documente d tha tth e relationshi p betwee n Pb B an d lea d uptak e fro m an y sourc e i s approximatel ylinea ra tlo wintak e level s bu t"flatten s out " a t hig h intak e level s (CD , Section s 11. 2 an d 11.3)
. Becaus e th e Pb B level s ( < 2 0 py/dl ) an d lea d intake s o fth e Ryu infant s ar e mor e relevant , th e criteri a documen tconclude s tha tth e slop e fro m thi s stud y(0.1 6 py/d l pe r py/day ) i s th e bes tavailabl e estimat e (CD , p . 11-129)
. Sinc e lea d uptake/Pb B relationship s ar e o finterest , thi s slop e (0.16 ) wil l b e combine d wit h th e rang e o fgastrointestina l absorptio n rate s (42-53% ) cite d fo rinfant s i n th e C D t o illustrat e th e rang e o fuptake/Pb B relationship s a tth e en d o fthi s section
. Abaselin e PbB o f4 pg/d l wil l b e assumed , base d o n recen tstudie s o fPb B level s an d lea d intak e i n Bosto n an d Cincinnat i infants'(Rabinowit z e tal. , 1985 ; Succo p e tal. , 1987)
. 2 . Dietar yIntak e Studie s i n Adult s Th e relationshi p betwee n bloo d lea d an d foo d and/o rwate rlea d level s ha s bee n examine d fo radult s i n bot h experimenta l studie s i n whic h controlle d dietar ysupplement s wer e administere d t o volunteers , an d duplicat e die t studies
. Again , severa l studie s indicat e non-linea rbloo d lea d response s a t hig h exposure s bu ta linea rrelationshi p a trelativel ylo wintak e level s ( < 10 0 py/day , o r< 30 py/d l PbB)
. Tw o studie s identifie d i n Tabl e 11-4 9 an d 11-5 0 o fth e C D appea rmos t usefu l i n estimatin ya dietar ylead/bloo d lea d relationshi p chiefl ybecaus e o fthei rsampl e size s an d contro l ove rconfoundin yfactors : Sherloc k e tal
. (1982) , a duplicat e die tstud yo f3 1 mother s (an d thei rchildren ) fro m Ayr , Scotland ; an d Cool s e tal
. (1976 ) i n whic h 1 1 subject s an d 1 0 control s wer e studie d fo rbloo d lea d respons e t o ora l dosage s o flea d acetate .P.4 1 IV- 8 Th e latte rstud ywa s a n extensio n o fth e Stui k (1974 ) experiment , result s o fwhic h wil l no tb e use d her e becaus e response s wer e no tfollowe d lon g enoug h fo rbloo d lea d t o equilibrate
. Th e weighte d mean o fth e slope s reporte d i n th e C

D fo rth e Sherloc k

an d Cool s studie s i s 0.03 2 pg/d l increas e i n bloo d lea d pe rpg/da yintake , whic h i s a facto ro f5- 6 time s lowe rtha n th e comparabl e slop e estimate d fo rinfant s a tlo wexposur e levels
. Agastrointestina l absorptio n facto ro f0.15 , cite d i n th e C D fo r adults , wil l b e applie d t o thi s intak e slop e t o deriv e a bloo d lead/uptak e relationship
. Abaselin e PbB leve l o f4 pg/d l wil l b e assume d fo radult s base d o n projection s describe d i n Appendi xC
. Th e sam e patter n o fnon-linea r absorptio n see n i n childre n wil l b e assume d an d a slop e o f.00 8 pg/d l pe r pg/da ywil l b e use d fo rlevel s abov e 5 0 py/da yi n adults
. 3 . Applicatio n o fChamberlai n an d Hear d Analysi s o fAdul tExposur e Dat a A n attemp tt o relat e bloo d lea d an d absorbe d lea d wa s mad e byChamberlai n an d Hear d (1981 ) usin g epidaniologica l an d c.linica l dat a o n adul tmen (William s e tal. , 1969 ; Kehoe , 1961 ; Nordman , 1975 ; Zurl o an d Griffini , 1973. ; Fuga s an d Saric , 1979)
. Tota l dietar yan d airborn e lea d uptak e was estimate d usin g calculation s simila rt o thos e presente d i n th e integrate d lea d uptak e mode l i n Sectio n IV.A
. Th e followin g assumption s give n i n Chamberlai n e tal. , (1978 ) wer e used : a ) a fraction , 0.55 , o fth e uptak e become s attache d t o re d bloo d cells ; b ) th e biologica l half-lif e o flea d i n bloo d i s 1 8 days ; c ) a factor , 1.3 , i s t o b e allowe d fo rlong-ter m resorptio n an d re-entr yint o bloo d o fsom e o fth e lea d whic h i s store d i n bone ; an d d ) th e mass o fbloo d i s 540 0 grams . Wit h thes e assumptions , Chamberlai n an d Hear d calculate d th e followin g relationship : APb B = 0.5 5 x1 8 x1. 3 = 0.3 4 pg/d l pe rpg/da y AUptak e 54 x0.69 3P.4 2 IV- 9 Thi- s relationshi p i s comparabl e t o tha t derive d fro mth e Cool s and Sherloc k studie s afte r gastrointestina l absorptio n i s accounte d for . Give n uncertaintie s abou t som e o f th e studie s analyze d b yChamberlai n an d Hear d regardin g exposur e level s an d qualit ycontrol , and becaus e o f th e exposur e levels , thi s slop e i s presente d her e onl yfo r comparativ e purpose s an d wil l no t b e use d further . 4 . Lea d Balanc e Studies : Compartmenta l Model s T o demonstrat e a causa l relationshi p betwee n lea d i n th e bod yand a biologica l change , i t woul d b e idea l t o kno wth e amoun t o f lea d presen t a t th e sit e an d tim e o f th e effect . Fo r instance , i f lea d i s suspecte d t o induc e neuropsychologica l changes , a measur e o f th e lea d leve l presen t i n nerv e cell s whe n th e chang e occurre d woul d b e desirable . Livin g tissue s ca n rarel yb e sampled , an d dat a obtaine d a t necrops ycanno t revea l th e variation s i n exposur e throughou t th e individual' s life . Fo r analytica l simplicity , thes e tissue s ca n b e groupe d togethe r o n th e basi s o f lea d distributio n characteristic s an d bod yburden s o f lea d represente d a s a limite d numbe r o f distinct , homogenous , an d well-mixe d pool s o r physiologica l compartment s wit hsimila r kineti c properties . Mathematica l biokineti c model s hav e bee n fitte d t o dat a obtaine d i n long-ter mbalanc e studie s and t o lea d isotop e trace r experiment s tha t estimat e th e rate s o f inpu t to , transfe r between , and excretio n fro mth e differen t compartment s (Rabinowit z e t al. , 1976 , 1977 ; Batschele t e t al. , 1979 ; Bernard , 1977 ; Mallo n 1983 ; Harle yand Kneip , 1985 ; Marcus , 1985a,b,c) . Difference s in th e predictiv e lea d model s hav e bee n discusse d b yBernar d (1977) , Batschele t e t al . (1979 ) and Hammon d e t al . (1981) . Model s ar e shown schematicall yi n th e C D (Figure s 10- 3 an d 10-4) .__________P.4 3 IV-1 0 Th e choic e o fpool s o rleve l o faggregatio n i n a mode l depend s o n th e availabl e experimenta l data , th e appropriat e tim e scale , an d th e pre dictiv e use s o fth e analysis , an d i s a compromis e betwee n accurac yan d complexity
. Fo rexample , bloo d ca n b e broke n dow n int o plasm a an d erythrocyte s an d the n furthe rint o plasm a protein-boun d lead , diffusibl e lead , extracellula r flui d lead , an d erythrocyt e proteins
. Sof ttissue s ca n b e broke n dow n int o brai n (hippocampus , medulla , etc.) , kidneys , liver , hair , an d s o on . Th e har d tissu e pool s ca n b e separate d int o compact(cortical ) an d cancellou s (trabecular ) bones , an d teeth ; withi n eac h o fthese , separat e component s ma yb e neede d t o mode l distinc tdiffusio n tim e scale s (Marcus , 1985a,c)
. Becaus e th e skeleta l syste m i n youn g childre n i s rapidl ydevelopin g an d i s bot h larg e an d kineticall yactive , i ti s especiall yimportan tt o mode l bon e lea d i n children
. Unti l suc h refinement s ar e furthe rtested , a relativel y simpl e 3- 5 poo l mode l shoul d provid e a framewor k fo rpredictin g lea d distribution s i n children
. Thes e model s ar e helpfu l i n predictin g tota l bod yburde n o requilibriu m level s o flea d ove rtim e i n an yo fth e presume d kineti ccompartment s unde r differen texposur e conditions
. Th e basi cassumptio n o fth e model s i s tha t th e mass o flea d i n eac h o fth e compartment s change s accordin g t o a syste m o fcouple d first-orde rlinea rdifferentia l equation s wit h constan tfractiona l transfe rrates . Suc h model s predic ttha twhe n th e lea d intak e chanye s fro m on e constan tleve l t o another , ther e i s a directl yproportiona l chany e i n th e mass o flea d i n eac h compartmen tan d th e attainmen to fa ne wequilibrium
. Th e rate s an d magnitude s o fthes e change s ar e dependen tupo n th e rate s o f lea d flu xi n th e tissue s an d ca n theoreticall yb e calculate d fro m a compartmenta l mode l o fth e appropriat e parameters . Suppor tfo ra firs torde rkineti cmode l fo rlea d metabolis m i s demonstrate d bycalculations , usin g firs torde rmodel sP.4 4 IV-1 1
o fsof ttissu e an d bon e concentration s o flead , an d othe relement s (calciu m strontium , radium) , tha tfi thuman measurement s as wel l as b yusin g mor e comple xmodel s (Johnso n an d Myers , 1981 ; Mallon , 1983)
. Afour-compartmen tbiokineti cmode l o flea d metabolis m ha s bee n develope d fro m dat a obtaine d i n controlle d singl e dos e an d chroni clea d exposure s o f infan t( 9 months ) an d juvenil e (2 2 months ) baboon s (Mallon , 1983 ; Knei p e t al. , 1983)
. Dynami cbloo d measurement s an d stead ystat e bloo d an d orga n lea d measurement s wer e accuratel yfitte d t o predic tconcentration s o flea d i n blood , liver , an d kidney , an d bon e (th e fou rcompartment s i n whic h 95% o ftota l bod ylea d i s contained ) (Hear d an d Chamberlain , 1984)
. Huma n metabolis m an d growt h pattern s wer e applie d i n a compute rsimulatio n o fth e mode l tha twa

s the n successfull yvalidate d usin g human autops ydata
. Th e mode l parameter s wer e revise d usin g measure d metaboli cdat a fo r eac h orga n (e.g. , bon e turnove rrates ) fo rchildre n an d wer e use d t o simulat e lea d orga n burden s an d concentration s i n childre n wit h constan t lea d exposure s fro m birt h (Harle yan d Kneip , 1985)
. Althoug h complet e mode l validatio n i s no tpossible , th e revise d mode l i s consisten twit h experi menta l dat a o n bloo d lea d accumulatio n followin g dietar ylea d uptak e amon g infant s (Ziegle re tal. , 1978) , an d skeleta l lea d accumulatio n followin g controlle d exposure s i n adult s (Hear d an d Chamberlain , 1984)
. Thus , give n th e availabl e dat a thi s mode l appear s t o provid e th e bes testimate s o fPbB level s i n childre n wit h continuou s lea d uptak e ove rtime
. Tabl e 4- 2 present s PbB level s predicte d byth e mode l fo rmal e childre n unde rdifferen texposures , o rlea d uptak e levels
. N o difference s wer e foun d betwee n th e sexe s excep ta tolde rages , an d predicte d PbB level s wer e highes tamony2- 3 yea rolds , consisten twit h result s o fNHANE S I I an d th e Ne wYor k Cit yscreenin g progra m (Billic k e tal. , 1979)
. Thes e result s wil lP.4 5



### IV-1 2

TABL E 4-2 . PREDICTE D EQUILIBRATE D BLOO D LEAD LEVEL S (py/dl ) OVE R TIM E AMON GCHILDRE N WIT H CONSTAN T LEAD UPTAKES 3



### Lead Uptak e (pg/day ) Ag e 1 2 3 4 5 6 7 8 9 1 0 1 0

3. 0 4. 0 3. 7 3. 6 3. 5 3. 5 3. 3 2. 5 2. 3 2. 6 2 0

5. 9 8. 1 7. 3 7. 3 7. 0 6. 9 6. 5 5. 0 4. 6 5. 2 30

8. 9 12. 1 11. 0 10. 9 10. 5 10. 4 9. 8 7. 4 6. 9 7. 8 4 0

11. 9 16. 2 14. 6 14. 5 14. 0 13. 8 13. 0 9. 9 9. 3 10. 4 5 0

14. 8 20. 2 18. 3 18. 1 17. 5 17. 3 16. 3 12. 4 11. 6 13. 0 6 0

17. 8 24. 2 22. 0 21. 8 21. 0 20. 7 19. 5 14. 9 13. 9 15. 6 70

2U. 8 28. 3 25. 6 25. 4 24. 5 24. 2 22. 8 17. 4 16. 2 18. 2 8 0

23. 8 32. 3 29. 3 29. 0 28. 0 27. 6 26. 0 19. 9 18. 5 20. 8

a Fro m Harle yan d Knei p (1985)
.P.4 6 IV-1 3 6 e applie d t o estimate s o fth e integrate d lea d uptak e mode l t o estimat e children' s Pb

B level s unde ralternativ e ai rlea d levels
. I ti s importan t t o not e tha tthi s equilibriu m bloo d lea d mode l i s linea ri n tota l lea d uptak e a teac h age . Thi s i s a necessar yconsequenc e o fth e linea rpharmacokineti cmode l assume d byHarle yan d Knei p (CD , Appendi x11-A)
. Th e uptake/biokineti cmode l i s thu s logicall yconsisten twit h aggregat e an d disaggregat e linea rtotal-uptak e model s discusse d i n th e followin g sections
. Figur e 4- 1 compare s th e relationship s betwee n lea d uptak e an d bloo d lea d derive d fro m th e variou s (1983 ) studie s o n infant s an d adults
. Despit e th e divers e natur e o fth e populations , stud ydesigns , an d methodologies , ther e i s a fai rdegre e o fconsistenc yi n th e relationships
. Eac h stud y foun d tha ta linea rfunctio n provide d as goo d a fit , i fno tbetter , tha n othe rnon-linea rform s a tth e relativel ylo wexposur e level s investigated
. Som e experimenta l an d epidemiologica l evidenc e suggest s however , tha tth e relationshi p betwee n lea d concentration s i n tissue s an d cumulativ e lea d intak e i s onl yapproximatel ylinea ra tlo wlevel s o fintake , an d tha t successiv e increment s i n intak e o rexposur e resul t i n progressivel ysmalle r contribution s t o bloo d lea d concentration s (Aza re tal. , 1975 ; Moore , 1977 ; Gross , 1981 ; Sherloc k e tal. , 1982)
. Th e curve s draw n i n Figur e 4- 1 fo rinfant s an d adult s d o i n fac tinclud e smalle rslope s fo r lea d uptak e value s abov e 5 0 pg/day
. Thi s curvilinea rrelationshi p ma yb e du e t o increase d rena l clearanc e wit h highe rbloo d lea d (Gross , 1981) , distributiona l non-linearitie s du e t o difference s i n lea d bindin g site s i n differen ttissue s (Hammond e tal. , 1981 ; Marcus , 1985b ; Manton , 1985) , and/o rt o a sizeabl e poo l o fmobil e lea d i n bon e maintaine d mor e o rles s independentl yo fuptak e (Rabinowit z e tal. , 1977 ; Chamberlain , 1983)
. I t appear s however , tha tnon e o fth e mechanism s introduc e significan tnon-linearitie s

## BLOO D LEA D (ug/dl )

3 5 3 0 h 2 5 2 0 h 1 5 - 1 0 5 - 0 1 0 2 0 3 0 4 0 5 0 LEAD UPTAK E (ug/day ) 6 0 7 0 RYU- A
RYU- B SHERLOCK/COOL S
HARLE Y AN

D KNEI P < i



## BO

FIGURE 4-1 , SUMMAR Y O F RELATIONSHIP S BETWEE NDAILY LEA D UPTAKE AN

D BLOOD LEA

D FO R DIFFEREN

T AGE GROUPS , DERIVE D h*KUM : a ) RY UE T AL . (1983 ) STUD Y O F INFANT S - - TWO CURVE S REFLEC T RANGE OF G I LEA D ABSORPTIONKATE S (0.4 2 - 0.53) ; b ) SHERLOC K E T AL . (1982 ) AN D COOL S E T AL . (1976 ) STUDIE S O NADULTS ; AN

D c ) HARLE Y AN

D KNEI P (198b ) BIUKINETI C MODE L WIT H ESTIMATE S FO

R 2-YEA R OL D CHILDRE NILLUSTRATED .

^ 1P.4 8 IV-1 5
a tbloo d lea d level s belo w30 pg/d l (Marcus , 1984 , 1985a,c ; Chamberlain , 1983 ) an d tha ta linea rmathematica l mode l i s vali d fo rrelativel ylo wt o moderat e lea d exposure s (CD , p . 10-31 , Appdx
. 11A-2)
. A s discusse d above , a tlevel s abov e 30-4 0 pg/dl , bloo d lea d ma yb e a n inadequat e inde xfo rtissu e lea d burden s i n man ychildre n (Piomell i e tal. , 1984 ) an d linea rmodel s are likel yt o los e thei rpredictiv e power . Fo rthi s reason , th e relationship s depicte d i n Fiyur e 4- 1 ar e truncate d a t30 py/dl
. T o estimat e PbB level s abov e 30 pg/dl , whic h i s no wabov e th e Pb

B leve l o fhealth-relate d concer n fo rchildren , us e o fnon-linea r model s discusse d i n th e criteri a documen twoul d b e require d (CD , Appendi x11.B)
. Th e compartmenta l biokineti cmode l o flea d metabolis m develope d byMallo n (1983 ) an d Knei p e tal
. (1983) , an d revise d fo rchildre n byHarle yan d Knei p (1985) , relie d o n a broa d arra yo fexperimenta l an d observationa l measurement s o fmammalia n metabolis m an d growt h patterns , an d has bee n successfull y validate d usin g availabl e human experimenta l an d autops ydata
. A s i s th e cas e fo ran ymathematica l model , ther e are inheren tlimitation s an d associate d uncertainties
. Becaus e thi s mode l i s base d o n th e mos tcomprehensiv e dat a availabl e an d ha s bee n develope d specificall yt o predic torga n lea d concen tration s ove rtim e i n youn ychildre n wit h continuou s lea d uptake , i t appear s tha tth e output s o fth e Harle yan d Knei p (1985 ) biokineti cmode l ar e th e mos tappropriat e t o predic tPb B level s i n childre n usin yth e inteyrate d lea d uptak e estimat e methodologie s presente d i n Sectio n IV. Aan d Appendi xA
. Pb B level s calculate d fro m th e conjunctio n o fth e inteyrate d lea d uptak e an d biokineti cmodel s wil l b e presente d i n th e staf fpape r(alon g wit h estimate s usin g othe rmodelin g approache s tha tar e discusse d later ) i n orde rt o estimat e potentia l healt h impact s unde ralternativ e ai rlea d levels
. Methodologie s t o calculat e children' s an d adul tbloo d lea d level s dat a unde ralternativ e standard s usin g othe rdat a an d othe rmodelin g approache s wil l b e discusse d i n Sectio n V
.P.4 9

V
. STATISTICA LRELATIONSHIP S BETWEE N BLOO D LEA D AN D AIRBORN E LEAD : US E I N DISAGGREGAT

E AN D AGGREGAT

E MODEL S Thi s sectio n addresse s tw o othe rmethod s o fdeterminin g th e contributio n o fai rlea d t o tota l exposur e an d th e potentia l healt h impact s associate d wit h alternativ e ai rlea d levels
. Th e previou s sectio n examine d th e re lationship s betwee n bloo d lea d i n childre n an d estimate d level s o flea d uptak e fro m th e air , housedust , outdoo rsoi l an d dust , an d diet
. Th e tw o approache s presente d her e develo p a direc trelationshi p betwee n ai rlea d an d bloo d lea d fro m variou s experimenta l an d communit yo repidemiologica l studies : 1 ) a disaggregat e mode l i n whic h tota l exposur e t o ai rlea d i s assesse d byseparatel yanalyzin g th e relationshi p betwee n bloo d lea d an d inhale d ai rlead , versu s th e associate d change s i n bloo d lea d as a resul t o fexposur e t o lea d tha thas deposite d ont o soil , dust , food , an d water ; an d 2 ) a n aggregat e mode l i n whic h a singl e variable , ai rlead , serve s as a n inde xfo rlea d exposur e throug h othe rmedi a affecte d byintegrate d atmospheri clea d deposition
. Experimenta l studie s includ e thos e i n whic h adul tvolunteer s hav e bee n expose d t o controlle d level s o flaborator ygenerate d lea d aerosols
. Becaus e intak e o fai rlea d throuy h th e die tan d dus twa s probabl yminima l fo rth e adul tsubject s i n thes e experiments , thes e studie s underestimat e th e dose-respons e relationship s tha twoul d b e see n amon ychildre n wit h chanye s i n ai rlea d (Anyl e e tal. , 1985)
. Epidemiologica l (i.e. , community ) studie s provid e correlation s betwee n ai rlea d an d bloo d lea d i n differen t population s o fchildre n an d adult s unde rvaryin ycondition s o flead , fro m curren to rpreviou s atmospheri cfallou tan d othe rsources , an d yiel d dose respons e estimate s a tmor e relevan tlevels
.P.5 0 V- 2 Becaus e o fth e simultaneou s presenc e o flea d i n multipl e medi a wit h differen ttim e profiles , th e assessmen tan d us e o fthes e studie s i s no talway s direct
. A s i n an yattemp tt o mode l lea d exposure , possibl e confoundin g variable s tha tinfluenc e Pb B level s bu twhic h ar e no trelate d t o ai rlea d measurement s (e.g. , lea d i n paint , canne d foo d an d plumbing , socioeconomi cstatus , parenta l care , housin yan d pla yconditions , calciu m intake ) canno talway s b e disentangled
. Contro l fo rconfounder s ca n b e achieve d bycomparin g population s tha tdiffe ronl yi n thei rexposur e t o airborne-derive d lead , althoug h identifyin g suc h group s ha s bee n difficult
. Anothe rpossibilit yi s t o perfor m a multivariat e statistica l analysi s i n whic h adjustment s ar e mad e fo rsom e o ral l o fth e confounder s befor e calculatin g th e bloo d lead/ai rlea d relationship
. Thi s require s informatio n o n th e valu e o feac h confounde rfo reac h individual , whic h i s als o difficul tt o .estimate
. I n th e cas e o flead , severa l confounder s ten d t o wor k i n th e sam e directio n a

s ai rlead , e.g. , elevate d exposur e an d unfavorabl e socia l condition s ofte n ar e bot h concentrate d i n centra l cities
. Consequently , whe n statistica l adjustmen ti s incomplete , th e relationshi p betwee n ai r lea d an d bloo d lea d wil l likel yb e inflated
. Adjustmen tfo ra confoundin g variabl e ma yresul ti n al l o fth e share d varianc e betwee n confounde ran d exposur e variabl e attribute d t o th e confounder ; thi s ca n inevitabl ylea d t o underestimatio n o fth e "true " impac to fth e exposur e variabl e (Rutter , 1983)
. I n characterizin yyoo d studie s o fai rlead/bloo d lea d relationships , severa l reviewer s (e.g. , Hammon d e tal. , 1981 ; Brunekreef , 1984) , as wel l as th e CD , discus s ke yfactor s tha tshoul d b e considered
. Thes e includ e a well-define d stud ypopulation , a goo d measur e o findividua l exposure , measuremen to fbloo d lea d wit h adequat e qualit ycontrol , a statistica l analysi s mode l tha ti s biologicall yplausibl e an d consisten twit h th e data ,P.5 1 V- 3
an d contro l o rmeasuremen to fimportan tcovariate s (CD , p . 11-63)
. Th e studie s identifie d i n th e CD , an d highlighte d here, addres s thes e factor s sufficientl yt o establis h meaningfu l relationships
. A
. Disayyreyat e Mode l 1 . A i rLead/Bloo d Lea d Relationship s i n Adult s Becaus e th e relationshi p betwee n bloo d lea d an d environmenta l exposur e i s nonlinea racros s th e rang e o fpotentia l exposure , bu tapproximatel ylinea r a tlowe rlevel s (CD , p . 11-65) , th e focu s her e i s o n studie s o fadult s with ou texcessiv e occupationa l o rpersona l exposure . Longitudina l studie s i n whic h change s i n bloo d lea d wer e measure d i n adul tvolunteer s expose d t o controlle d level s o flaborator ygenerate d aerosols , i n som e case s wit h isotopi clea d tracer , ar e summarize d i n Tabl e 11-4 0 o fth e CD
. Dat a fro m th e mos trelevan tstudie s hav e bee n reanalyze d i n th e C D t o yiel d bloo d lea d ai rlea d ."slopes " (3) , wher e 3 measure s th e chang e i n bloo d lea d expecte d fo ra uni tchang e i n ai rlead
. A s note d i n th e CD , th e blood , lea d inhalatio n slop e estimate s var y appreciabl yfro m on e subjec tt o anothe ri n th e experimenta l studies , an d fro m on e stud yt o another
. Th e weighte d slop e an d standar d erro restimate s fro m th e Griffi n stud y(1.7 5 +_0.35 ) wer e combine d wit h thos e calculate d similarl yfo rth e Rabinowit z stud y(2.1 4 +_0.47) , an d th e Keho e stud y (1.2 5 +^0.35) , yieldin g a poole d weighte d slop e estimat e o f1.6 4 +

_0.2 2 (CD , pp . 11-9 9 t o 11-102)
. Excludin g th e subject s i n th e Keho e stud yexpose d t o ver yhig h ai rlea d level s (u p t o 3 6 pg/m 3 ) , result s i n a n averag e slop e o f approximatel y1. 9 pg/d l pe rpg/m 3

. Severa l deficiencie s i n th e individua l studie s ar e discusse d i n th e C D suc h a

s uncontrolle d o runmeasure d ai rlea d exposure s outsid e th eP.5 2 V- 4 chambers o rdifficultie s i n determinin g non-inhalatio n bloo d lea d baselin e level s (CD , p . 11-101)
. Furthermore , thes e experimenta l inhalatio n studie s ma yunderestimat e th e overal l impac to fairborn e lea d (vi a depositio n an d incorporatio n ove rtim e int o soils , dusts , water , foo d chain)
. Thi s i s much les s o fa problem , however , i n predictin g change s i n adul tlea d exposur e i n th e future , compare d t o children
. Fo rexample , althouy h smal l increase s i n adul tbloo d lea d level s hav e bee n observe d i n area s o fhiy h lea d contaminatio n (Barltro p e tal. , 1975 ; Gallache re tal. , 1984 ; Rabinowit z e tal. , 1985) , adult s d o no tinges tsignifican tamount s o fdir tan d certainl y d o no tabsor b ingeste d lea d a tth e sam e rat e a s children
. Th e cross-sectiona l relationshi p betwee n bloo d lea d an d ai rlea d i n adult s has bee n examine d i n severa l populatio n studies
. Aza re tal
. (1975 ) studie d fiv e group s o fmen (ca b driver s an d offic e workers ) wh o carrie d pers.ona l ai rlea d monitor s an d whos e non-ai rlea d exposure s (water , smoking ) wer e als o measure d ove ra 24-hou rperiod
. Severa l alternativ e geometri c mean regression s hav e bee n calculated , includin g linea ran d non-linea r model s assumin g differen tnon-ai rcontribution s t o bloo d lead , an d estimation s o fth e effec to fendogenou s lea d store d i n th e skeleto n usin yay e as a surroyat e measur e o fcumulativ e exposure . Non e o fth e fitte d model s ar e siynificantl ydifferen tstatisticall y(CD , p . 11-81 ) wit h a poole d slop e estimat e o f1.3 2 ^0.3 8 (CD , p . 11-105)
. Althouy h th e othe rpopulatio n studie s typicall yuse d les s accurat e measure s o findividua l exposure s (e.g. , Teppe ran d Levin , 1975 ; Nordman , 1975 ; Johnso n e tal. , 1975) , th e rang e o fslop e estimate s (1.0-2.0 ) i s comparabl e t o th e Aza re tal
. an d experimenta l inhalatio n result s (Snee , 1981 ; se e CD , p . 11-98)
.P.5 3 V- 5 Althoug h th e studie s differe d i n co-variable s measured , populations , exposur e conditions , etc. , th e mos treliabl e an d relevan tstudie s consistentl y yiel d inhalatio n slop e value s typicall yi n th e rang e o f1.3-2. 0 pg/d l pe r pg/m 3 , wit h a weiyhte d slop e o f1.4 . Th e abov e slop e estimate s ar e derive d fro m studie s i n whic h exposur e t o ai rlea d wa s assesse d ove rdays , weeks , o rmonth s an d ar e base d o n th e assumptio n tha ta n equilibriu m leve l o f bloo d lea d i s achieve d withi n a fe wmonth s afte rexposur e beyins
. Thi s i s onl yapproximatel ytrue , sinc e som e o fth e absorbe d lea d tha taccumulate s i n th e skeleto n deposit s i n th e sponyytrabecula rbone s (e.y. , rib , vertebrae ) wher e i tma

yb e resorbe d int o th e bloo d stream . A n additiona l facto r therefore , shoul d b e allowe d fo rpossibl e re-entr yo flea d int o th e bloo d transferre d fro m bon e o rothe rlong-ter m storag e (Chamberlain , 1983)
. Base d o n isotopi crati o an d radiolabe l trace rstudie s o n adults , Chamberlai n e ta l
. (1978 ) estimate d thi s facto rt o b e 1.3 . I ti s likel yt o b e lowe ri n childre n becaus e o fth e rapi d growth , hig h rat e o fturnove ran d smalle r reservoi ro flea d i n thei rskeleta l systems . Whil e n o adjustmen tfo rbon e resorptio n wil l b e mad e fo rchildren' s slopes , i t appear s reasonabl e t o appl ythi s facto rt o th e bloo d lead/ai rlea d inhalatio n slop e o f1. 4 derive d abov e fo radults , yieldin g a slop e estimat e o fabou t1.8 . 2 . Estimatin g Futur e Adul tBloo d Lea d Average s Tw o adul tpopulation s requir e separat e exposur e prediction s fo rth e over a l l ris k

analysis : middle-age d males , 40-5 9 year s o faye ; an d preynan twomen , as exposur e surrogate s fo rfetuse s (se e CD , Section s 13.7. 2 an d 13.7.3)
. Olde rwomen ma

yals o b e a tincrease d ris k du e t o mobilizatio n o fbon e lea d afte rmenopaus e whic h ca n exacerbat e osteoporosi s (Silbergel d an d Schwartz , 1987)
. Unlik e children , wh o receiv e much o fthei rlea d fro m ingestio n o f lea d contaminate d soil s an d dusts , especiall ythos e livin g nea rpoin t sources , th e bul k

o fnon-occupationa l adul tlea d exposur e typicall yca n b eP.5 4 V- 6 attribute d t o die t(e.g. , canne d food s an d drinkin g wate rcontaminate d by lea d solder , depositio n o fatmospheri clea d ont o crop s an d othe rvegetation ) (se e CD , Tabl e 7)
. Further , women o fchild-bearin g ay e an d middle-aye d men hav e cumulativ e store s o flead , primaril yi n thei rbones , s o tha tth e short-ter m change s i n lea d exposur e tha twil l b e assume d fo r1990-9 6 unde r alternativ e lea d NAAQ S (th e timefram e fo rwhic h cas e stud yexposur e analyse s wil l b e made ) wil l hav e relativel ysmalle rimpact s o n tota l bod yburde n an d bloo d lea d tha n i n children
. Althoug h futur e change s i n industria l lea d emission s woul d no taffec tPb B level s amon g adul tpopulation s livin g nea r poin tsource s t o th e exten tas the ywoul d children , eve n smal l change s ca n b e important , especiall ygive n th e sensitivit yo fth e fetu s t o lead
. Give n a backgroun d o r"baseline " bloo d lea d estimat e representin g non-ai r lea d adul texposures , an d a n averag e disaggregate d bloo d lead : ai rlea d relationship , th e followin g simpl e equatio n ca n b e use d t o predic toloo d lea d mean s fo rdifferen tadul tpopulation s i n ou rcas e studies : x" = y 0 + 1.8 A wher e x= mean bloo d lea d (py/dl ) y 0 = non-ai rbackgroun d bloo d lea d (pg/dl) , an d A= averag e ai rlea d (pg/m 3 ) Estimate s o fnon-ai r"background " bloo d lea d leve l contribution s fo rdifferen t adul tpopulation s tha twil l b e use d i n th e 1990-9 6 cas e studie s ar e derive d i n Appendi xC
. Issue s involve d i n estimatin g feta l PbB level s are als o discusse d there
. 3 . Ai rLead/Bloo d Lea d Relationship s i n Childre n Thre e populatio n studie s o fchildre n livin g nea rlea d poin tsource s i n whic h covariate s wer e controlle d (e.g. , age , sex , dus texposure ) wer e extensivel yanalyze d i n th e C D fo rth e mos tusefu l an d relevan testimate s o fP.5 5 V- 7
inhalatio n slopes : Angl e an d Mclntire , 197 9 ( 3 = 1.9 2 +_0.60) ; Roel s e tal. , 1980( 3 = 2.4 6 +_0.58) ; an d Yanke l e tal , 1977/Walte re tal , 198 0 ( 3 = 1.6 3 ^0.084)
. Th e media n slop e o fth e thre e studie s i s 1.9 7 (CD , p . 11-189) ; it s applicatio n fo rus e i n th e disaggregat e mode l i s discusse d below
. 4 . Estimatin g Children' s Bloo d Lea d Level s Usin g Disaggregat e Mode l Th e relationshi p betwee n bloo d lea d an d direc t inhalatio n o fairborn e lea d provide s informatio n usefu l fo rchange s i n ai rlea d o n a tim e scal e o f onl ysevera l month s (CD , p . 11-189)
. Ove rtime , suspende d lea d i s deposite d an d incorporate d int o soil , dust , an d water , an d enter s th e foo d chain
. Sinc e prio ran d curren tatmospheri cfallou tdirectl ymodif yth e dail y burde n o fingeste d lead , larye rchanye s i n bloo d lea d woul d b e predicte d i f th e associate d change s i n th e surfac e depositio n o flea d wer e accounte d for , rathe rtha n simpl yinhale d ai rlea d (Anyl e e tal. , 1984)
. T o accoun tfo r th e simultaneou s presenc e o flea d i n multipl e environmenta l media, , th e C D ha s analyze d th e separat e mathematica l relationship s betwee n bloo d lea d an d dietary , soil , an d dus tlead , describe d i n detai l i n Chapte r11.4 . Usin y representativ e value s fo rlea d concentration s i n thes e media , thes e relationship s wer e applie d i n a furthe ranalysi s presente d i n th e C D (CD , Tabl e 13-6 ) as a wa yt o estimat e proportiona l input s t o tota l bloo d lea d level s i n U.S
. children
. Asimila rdisaggregat e mode l wa s develope d b yAngl e an d Mclntir e (1979 ) an d Angl e e tal
. (1984 ) i n formin g a n integrate d lea d exposur e functio n fro m measurement s o flea d i n air , soil , an d hous e dus tan d relatin g tha tt o PbB level s o fchildre n livin g i n variou s area s o f Omaha
. Th e disaggregat e mode l develope d i n th e CD , intende d t o represen t th e the n "curren t(i.e. , 1983-84 ) exposur e picture, " i s adopte d here i n Tabl e 5- 1 fo rdifferen tai rlea d level s an d backgroun d level s o flea d i nP.5 6 

### V- 8
TABL E 5-1 . DISAGGREGAT E MODE L OF CONTRIBUTION S FRO MVARIOU S MEDI A TO 199 0 MEDIA

NBLOOD LEA

D LEVEL S (pg/dl ) OF U.S . CHILDRE N ( 2 YEAR S O

F AGE) : BACKGROUN

D LEVEL S AN

D INCREMENTA

L CONTRIBUTION S FRO

MAIR 1 '

Sourc e Backgroun d - nonai r foo d an d water ^ Dust 3 Subtota l Background-A i r Foo d an d Wate r Ingeste d Dus t(wit h P b deposite d fro m air) ^ Inhale d air 6 Tota l 0.2 5 1. 2 0. 1 1. 6 0. 2 1. 0 0. 5 3. 0 0. 5

1. 2 0. 1 1. 6 0. 2 1. 7 1. 0 4. 2 Ai rLea d

0.7 6 1. 2 0. 1 1. 6 0. 2 2. 5 1. 5 5. 5 (pg/m 3 )

1. 0 1. 2 0. 1 1. 6 0. 2 3. 2 2. 0 6. 9 1.2 b

1. 2 0. 1 1. 6 0. 2 4. 0 2. 5 8. 0 1. 5

1. 2 0. 1 1. 6 0. 2 4. 7 3. 0 9. 2 Adapte d fro

mTabl e 13- 6 o f CD . ^Estimate d dietaryintak e o f non-ai r P bi n 199 0 (fro

mCohen , 1988 ; Appendi xA ) 7. 6 pg/da

yx0.1 6 pg/d l pe r pg/da y(fro mRy u e t al. , 1983) . 3 Fro mCD , Chapte r 7 , 1/1 0 dus t no t atmospheric . Using Anyl e e t al . (1984 ) "lo warea " fo r soi l an d hous e dus t level s an d median regressio n coefficient s fro mStark e t al . (1982) : (1/10 ) x(9 7 pg/ g x0.0022 ) + (32 4 pg/ yx0.0018) . ^A s i n 2 above , bu t usin g 1. 2 pg/da

yfo r dietaryintak e o f atmospheri c lead . Derived fo r componen t o f backyroun d P bi n foo

d fro mpas t depositio n fro mai r _ont o soi l an

d int o othe r medi a leadin yint o human foo

d chain . ^Regressio n equation s o f Stark e t al . (1982 ) use d alon ywit hlevel s o f soi l dus t an

d hous e dus t predicte d b yreyressio n analyse s o f collecte d poin t sourc e environmenta l data , describe d i n Appendi xB . Fo r example , th e mea n soi l an d hous e dus t lea

d concentration s associated wit h1. 0 py/m 3 i n ai r ar e approximatel y63 0 pp man d 1U3 5 ppm , respectively . Th e effec t o

n blood lea

d woul d be : (63 0 x0.0022 ) + (103 5 x0.0018 ) = 3. 2 pg/d l pe r pg/m 3
. 6 Usin g th e median inhalatio n slop e o f 1.9 7 pg/d l pe r pg/m 3 fro mth e CD , p . 11-189 .P.5 7 

### V- 9 food , .water , dust , an d soil , expecte d i n 1990 . Th e estimate s ar e mea n PbB level s fo r2-yea rol d children ; comparabl e analyse s fo rothe raye s o f childre n ca n b e don e usin yth e aye-specifi cestimate s o fdietar ylea d intak e presente d i n Appendi xA
. Calculation s an d assumption s use d i n derivin yth e estimate s ar e summarize d i n footnote s t o th e tabl e an d ar e simila rt o thos e describe d i n Tabl e 13- 6 o fth e CD
. Th e followin g change s wer e mad e fo rth e presen tanalysis : 1 ) Estimate d level s o fdietar ylea d intak e fo rchildre n i n 199 0 wer e substitute d fo rth e estimate s fo r1983-8 4 use d i n th e CD
. Th e 199 0 pro jections , describe d i n Appendi xA , ar e base d o n th e Multipl e Sourc e Foo d Mode l develope d i n th e C D an d use s mor e recen tdat a o n th e downward trend s i n foo d an d water ; 2 ) Soi l an d housedus tlea d concentration s associate d wit h differen t ai rlea d level s ar e estimate d base d o n th e long-ter m relationship s derive d fro m reyressio n analyse s o fdat a collecte d fro m concurren tmeasurement s o f air , soil , and/o rdus tlea d concentration s a tabou t45 lea d poin tsourc e location s (se e Tabl e A-4)
. Thes e sam e relationship s ar e bein yuse d t o estimat e surfac e soi l an d indoo rdus tlea d level s i n th e uptak e biokineti c model
. I n contrast , soi l an d dus tlea d concentration s unde rdifferen tai r lea d level s wer e estimate d i n Tabl e 13- 6 o fth e C D byinterpolatio n o fdat a fro m th e Angl e e tal
. (1984 ) study
. Thi s stud yi s bu ton e o fman ydat a set s include d i n th e aforementione d regressio n analysi s describe d i n Appendi xB
. 3 ) Th e soi l an d dust/bloo d lea d regressio n coefficient s use d t o comput e soi l an d housedus tcontribution s t o bloo d lea d ar e fro m th e C D analysi s o fth e Star k

e tal
. (1982 ) stud yand
. ar e describe d i n th e C D as th e mos t reasonabl e media n estimate s (pp
. 11-151 , 11-191)
. Th e coefficient s use d i nP.5 8 V-1 0 Tabl e 13- 6 o fth e C D ar e fro m th e Angl e e tal
. (1984 ) stud yan d represen t uppe rboun d values
. I tmus tb e emphasize d tha tth e bloo d lea d estimate s presente d i n Tabl e 5- 1 represen tpopulatio n mean Pb B level s an d ar e illustrativ e only
. I n orde rt o asses s healt h risk s associate d wit h suc h ai rlea d exposures , i twoul d b e necessar yt o calculat e Pb B distribution s aroun d thes e mean levels , as discusse d earlie ri n Sectio n III.B
. Sinc e completio n o fth e 198 6 CD , severa l finding s hav e becom e availabl e tha tsupplemen tpreviou s conclusions
. Unpublishe d analysi s byJohnso n an d Wijnber g (1988 ) o fth e 198 3 stud yo fyoun g childre n livin g nea rth e Eas t Helen a smelte r(CDC , 1983 ) estimat e slope s fo rbot h bloo d lead-soi l lea d an d bloo d lead-dus tlea d o fapproximatel y1. 4 pg/d l pe r100 0 ppm . Thi s analysi s adopte d modelin g use d byEP Ai n th e C

D t o fi tothe rsimila rstudie s an d adjuste d fo rnumerou s covariate s includin g children' s age , ai rlead , dus tand/o rsoi l lea d dependin g o n analysis , poo rqualit ylea d painte d housing , smoking , an d secondar yoccupationa l exposure .
•A s indicate d i n man

yo fth e studies , th e dus tlea d slop e i s simila rt o th e soi l lea d slope , suggestin g tha tsoi l ma ycontribut e bot h directl yan d indirectl yt o blood
. Suc h hypothese s regardin g cause-effec tresponse s o f bloo d lea d t o earlie rexposure s hav e bee n explore d i n recen tlongitudina l studie s o n bloo d lea d an d developmenta l indicator s i n Cincinnat i (Bornschei n e tal. , 1985 , 1986 ) an d Bosto n (Rabinowit z e t al. , 1985 ; Bellinge re t al. , 1987 ) children
. Th e Cincinnat i dat a se twa s analyze d bystructura l equatio n method s (Bentler , 1980 ) fo rrelationship s betwee n exterio rsurfac e scrapings , dus tlead , an d bloo d lead
. Unfortunately , th e result s ar e expresse d as a linea requatio n i n logarithm s o fth e environmenta l variables , an d th e standardize d regressio n coefficient s ar e no t directl yinterpretabl e asP.5 9 V-l l overal l slope s fo rsoi l o rdus tlea d give n th e publishe d informatio n (Born schei n e tal. , 1986)
. Th e analyse s o fth e Bosto n dat a use d a somewhatdifferen ttechnique- - randor n effect s model s fo rlongitudina l dat a (Ware , 1985)
. Unfortunately , soi l lea d dat a wer e no tsample d longitudinally
. Ther e wer e repea t measuranent s fo rblood , dust , air , wate rlead
. Th e 18-mont h bloo d lea d regressio n mode l reporte d byRabinowit z e tal
. (1985 ) use d th e logarith m o fth e yar d soi l lea d measuremen tas a predictor , s o tha tth e reporte d slop e i s no tdirectl ycomparabl e t o thos e cite d i n th e CD
. However , th e slope s a t severa l concentration s ar e simila rt o thos e cite d i n th e CD : 8 pg/d l pe r 100 0 ppm soi l lea d whe n soi l lea d = 10 0 ppm , 1. 6 pg/d l pe r100 0 ppm soi l lea d whe n soi l lea d = 50 0 ppm , an d 0. 8 pg/d l pe r100 0 ppm whe n soi l lea d = 100 0 ppm . 5 . Plausibilit yo fDisaggregate d Slopes : Compariso n wit h Uptake /

Biokineti cMode l Th e disaggregate d air , soil , an d dus tlea d "slopes " use d Were are plausibl yconsisten twit h th e uptake/biokineti cmode l parameters . To sho w this , w e us e th e well-know n relationshi p (e.g. , Rabinowit z e tal. , 1976 ) betwee n bloo d lea d increments , dPbB , an d lea d intak e increments , dPbl ; dPb B = dPb l * (mea n residenc e tim e i n bloo d pool) / (volum e o f distributio n i n bloo d pool ) Fo ra two-yea rol d child , th e Harley-Knei p mode l predict s a mean residenc e tim e i n th e bloo d poo l o fabou t8 days , i.e. , a bloo d lea d hal flif e o f8

* 0.69 3 = 5. 6 days , consisten twit h Duggan' s (1983 ) estimat e o f4- 6 days
. Th e bloo d lea d poo l i s much large rtha n th e bloo d lea d volume , includin g accessibl e part s o fth e sof ttissues , bon e an d bon e marrow , an d extracellula rfluid
. Rabinowit z e tal
. (1976 ) estimate s tha tth e volum e o fthi s poo l i n adul tvolunteer s wa s 7 6 - 10 8 dl , almos ttwic e th e adul tP.6 0
V-1 2 bloo d volume . Sinc e th e bloo d volum e i n infant s (abou t 12 % o f bodyweight ) i s proportionatel ygreate r tha n i n adult s (abou t 8 % o f bodyweight) , w e wil l assum e th e bloo d volum e i n 1- 6 yea r ol d childre n i s abou t 10 % o f bodyweiyht , adjuste d fo r whol e bloo d densit yo f 1.0 6 kg/1 . Thus , th e volum e o f distri
butio n i n a 1 0 k g chil d (abou t 2 year s old ) i s take n a s about : 2 * 0.1 0 * 1 0 kg/(1.0 6 kg/1 ) = 2 1 = 2 0 dl . I n Tabl e 4.1 , th e tota l amoun to fdir tconsumed , C , i s take n as abou t 0. 1 g/day , o fwhic h a fractio n a = 0.2 5 i s absorbed
. Th e leade d dir ti s partitione d a

s som e fractio n p o fsoi l an d 1 - p o finterio rhous e dust
. Thus : dPb l = c* a * ( p * Pb S + ( 1 - p ) * PbD) Assumin g p = 0. 5 i.e
. equa l soi l an d dus taccess , dPb B = (0. 1 g/d ) * (0.25 ) * (0. 5 Pb S + 0. 5 * PbD) * 8d/2 0 d l

= 0.00 5 Pb

S +0.00 5 Pb

D Thu s th e soi l lea d vs . bloo d lea d an d th e dus tlea d vs . bloo d lea d slope s ar e bot h predicte d t o b e abou t0.00 5 pg/d l pe rppm . Avariet yo ffactor s ma yb e responsibl e fo rth e somewhatsmalle r empirica l slop e estimates , typicall yabou t0.00 2 (se e above)
. Eve n thoug h th e individua l househol d Pb S an d Pb

D level s ar e availabl e i n som e studies , thes e ar e no tnecessaril yth e exac texposur e covariates , bu tonl yindirec tsurrogat e measure s o fdir tlea d exposure . I ti s wel l know n tha texposur e measuremen t"error " tend s t o flatte n o rattenuat e regressio n slope s i n dose-respons e studie s (e.g. , Pickles , 1982 ; Fuller , 1987 ; Brunekree fe tal. , 1987)
. Ofcourse , specificatio n o fth e constant s (e.g. , a < 0.2 5 o rC < 10 0 mg/d ) coul d als o reduc e th e predicte d slopes
. Th e agreemen ti s nonetheles s impressive
. Th e ai rlea d slop e i s similarl ycalculated
. Fro m Tabl e 4.1 , th e poin t sourc e uptak e a t1. 0 pg/m 3 i s 0. 6 - 0. 9 pg/d , thu sP.6 1 V-1 3 PbB = (0. 6 - 0.9 ) * Pb A* 8d/2 0 d l

= (0.2 4 - 0.36 ) Pb

A Th e estimate d direc tinhalatio n slop e o f0.2 4 - 0.3 6 i s much smalle r tha n has bee n cite d fo rempirica l disaggregat e studies
. Thes e discrepancie s hav e bee n previousl ynote d i n Marcu s (1988b ) i n a n analysi s o fEas tHelen a data
. Th e difference s betwee n th e uptake/biokineti cmode l apparen t Pb D slop e an d th e disaggregat e regressio n slop e (0.0034 1 vs . 0.00151) , apparen tPb

S slope s (0.0019 9 vs . 0.00102) , an d apparen tPb Aslope s (0.6 3 vs . 1.08 ) wer e i n th e sam e direction
. I ti s possibl e tha tth e empirica l multipl e regressio n studie s hav e misallocate d th e varianc e i n log(PbB) , attributin g to o littl e effec tt o soi l an d dus tinyestion
. W e canno tdecid e whethe rthes e ar e artifact s o fth e multipl e reyressio n mode l o ro fth e uptake/biokineti csimulatio n model
. Nevertheless , th e slop e value s use d i n th e disayyregat e mode l ar e i n genera l consisten twit h th e uptake/biokineti c model
. B
. Aggregat e Mode l 1 . Ai rLead/Bloo d Lea d Relationshi p I n th e disaggregat e modelin g approach , "inhalation " slope s ar e derive d b ystatisticall yadjustin g bloo d lead/ai rlea d slope s b ywhateve rindirec t ai rexposur e variable s (e.g. , hous e dus tlead ) tha twer e measure d i n th e individua l epidemiologica l studies , an d the n combinin g separat e slope s availabl e fo rothe rexposur e medi a (e.g. , dust , food , water ) t o arriv e a ta n inteyrate d lea d exposur e function
. Wit h th e exceptio n o f Angl e an d Mclntir e (1979) , th e communit ystudie s fro m whic h inhalatio n slope s hav e bee n derive d hav e no tsimultaneousl ymeasure d lea d i n mor e tha n tw o o rthre e medi a an d consequently , th e integrate d lea d exposur e functio n i s necessaril ybase d o n dat a fro m multipl e studie s involvin g differen t populations , exposur e conditions , measuremen ttechniques , etc . An alternativ eP.6 2
V-1 4 metho d o fcalculatin g th e effec to fchange s i n ai rlea d o n children' s bloo d lea d i s t o analyz e individua l communit ystudie s i n whic h reliabl e "unadjusted " bloo d lead/ai rlea d relationship s ca n b e derive d suc h tha tth e impac to f bot h direc t(inhaled ) an d indirec t(vi a dust , soil , etc. ) contribution s o f ai rlea d ar e combined , o raggregated , i n on e variabl e (i.e. , ai rlead)
. To onl yus e a n "adjusted " bloo d lead/ai rlea d slop e (i.e. , inhalatio n slope ) woul d resul ti n a n underestimatio n o fth e impac to fatmospheri c lea d o n children' s tota l exposur e sinc e ai rlea d levels , i n general , ar e causall yrelate d t o othe rimportan texposur e variable s suc h as han d an d househol d dus tlea d (Brunekreef , 1984)
. Th e populatio n studie s wit h identifiabl e ai rmonitorin g method s an d reliabl e bloo d lea d dat a ar e summarize d i n Tabl e 5-2 . Non e o fth e studie s include d adul tpopulations
. Sinc e adult s d o no ttypicall yinges tmuch deposite d lea d anyway , th e aggregat e modelin g approac h wil l b e limite d t o youn g children
. A s i s th e cas e fo rth e dat a i n eac h o fth e experimenta l studies , differen tstatistica l analyse s o fthes e studie s hav e resulte d i n a rang e o fpossibl e value s fo rth e bloo d lead/ai rlea d relationshi p (3)
. Unadjuste d (i.e. , aggregate ) relationship s ar e presente d i n additio n t o adjuste d (i.e. , disaggregate ) relationship s derive d fro m regressio n analyses , th e latte rwhic h refe rt o th e bloo d lead/ai rlea d relationship s du e t o direc tinhalatio n exposure . I n Tabl e 5-3 , th e calculate d 3 value s liste d i n Tabl e 5- 2 fo reac h stud y ar e presente d accordin g t o th e bloo d lea d levels , ages , an d typ e o flocatio n o fth e investigate d children
. Relativel ywid e range s o f3 value s ar e observe d fo rindustria l an d urba n area s a tlo wan d hig h PbB level s an d fo r al l age s o fchildren
. Th e apparen ttren d toward s smalle rslope s wit h increasin y Pb B level s i s consisten twit h finding s withi n som e studie s (Angl e an dTABL E 5-2 . SUMMAR YO F EPIDEMIOLOGICA L STUDIE S O N LEAD-EXPOSE DCHILDRE N

Stud y Population 3 Ai r Lead 0 (ug/m 3 ) BloodLead (uq/dl ) Statistica l Mode l (Analyst ) Covariate s Measure d BloodLead / Ai pLeadSlop e Roel s et al. , 1976,1978,198 0

Yanke l e t al. , 1977 ; Walte r et al. , 198 U <lkm : 10-1 5 yr s n=21 4

2.5km : 10-1 3 yr s n=16 8 Urban : 10-1 4 yr s n=5 5 Rural : 10-1 3 yr s n=22 3 Living nea r "lea

dsmelte r (Antwerp , Belgium ) 1- 9 yr s n=114 9 (1974 ) 1-1 0 yr s n=78 1 (1975 ) living a t varying distance s fro

m lea d smelte r (Kellogg ) 2.68-4.0 6 0.54-1.0 0 0.45-0.5 6 0.29-0.3 7 ( 9 mont havgs ; lo w volum e sampler) 0 0-1.6km : 18. 0 1.6-4km : 14. 0 4-10k m : 6. 7 10-24km : 3. 1 24-32km : 1. 5

- 75km : 1. 2 (monthl y avgs. ) 24.6-30. 1

13.3-21. 1 10.4-12. 7 9.0-10. 7

65. 9 47. 7 33. 8 32. 2 27. 5 21. 2 21. 2 Multipl e regressions : Roel s e t al. , 198 0 ( 8 groupmeans ) C O(14 8 subjects ) Age , drinkin g water , income 5. 3 plu s handdus t P badjustmen t 0.UU 7 -plu s han

ddus t P badjustmen t 2.4 6
Multipl e regressions : Yanke l e t al . (1977 ) Sne e (1982b ) Sne e (1982a ) C U(linear ) CU(non-linear ) Walte r e t al . (1980 ) Groupcomparison s (Brunekreef , 1984 ) Age , drinkin g water , paint , SES , hous e dus t -plu s soi l & dus t P b occupatio nadjustmen t -plu s soi l Pb , occupation , cleanliness , pic a adjustmen t -same a s abov e -same a s abov e -same a s abov e No adjustmen t fo r soi l o r dus t P b A t l. Uuy/rn^ , iy7 4 dat a 1.1b 1.1 3 l.U / 1.5 2 1.1b 1.2b 2.4-3. 3 dependin g ond

y Angl e an

d1-1 8 yr s n=83 1 Mclntire , living inindustria l 197 9 urban , suburban

area s o f Omaha industrial : 0;37-1.6 6 24. 8 urban : 0.32-1.4 4 22. 0 suburban : 0.22-0.7 3 18. 0 (annua l avgs . 1970 - 1977 ) Regressio nAnalyses : Angl e an

dMclntir e (1979 ) (6-18yr . olds ) C U(Tabl e 11-33 ) (1-1 8 yr . olds ) C0-(Tabl e 11-33 ) Brunkreef , 1984 ; (al l children ) (1- 5 yr. olds ) (6-1 8 yr . olds ) Age , drinkiny water , food -plu s soi l & hous e dus t Pbadjustmen t -same a s abov e -sam e a s abov e N o adjustmen t fo r soi l o r dus t lea

d 1. 4

U. b 1.9 2 4.4 U U.b b 2.6 3 2.1 U <

c 1 1 — > O l

Brunekree f et al. , 1981 ; Zielhui s et al. , 197 9 1976:2- 3 yr s n=108

1977:1- 7 yr s n=690 1978:1- 3 yr s n=95 livin g <2k

m an d 2-5km fro m secondar

ysmelte r (Arnheim ) 0.5-2.5(0.4km ) 0.4-1.6(0.4km ) 0.28-0.51(<lkm ) ( 2 mont havg. ) 11.8(2-5km)-19.7(.4-lkm ) 14.6(l-2km)-18.2(.4-lkm ) 16.1(.4-lkm ) Groupcompariso n (Brunekreef , 1984 ) Multipl e regressio n (Brunekreef , 1984 ) Age , parenta l educatio n an dexposure , drinkiny water , food , ag e o f home , mouthiny behavior/handdirt , hous e dus t

- plu s adjustmen t for parenta l ..educatio

n 4. 0 (1976 ) 3. 6 (1977 ) 3. 6 (1976 ) Landriga n1972:1-1 8 yr s n=25 9 (exposed ) et al. , 1975 ; 1977:1-1 8 yr s n=49 9 (control ) Mors e e t al . 1-1 8 yr s n=14 0 (exposed ) 197 7 livin g nea r primary smelte r (El Paso ) <.8k m .8-1.6k

m 6.0 d <.8k

m .8-1.6k

m 10. 0 5. 5 3.Ud ( 4 mont havg. ) 41. 4 3 1

17.7 e z u Groupcompariso n (Brunekreef , 1984 ) Age , drinkiny water , mil k consumption , parenta l income , home pain t statu s 2. 6 (1972 ) i.l (197/ )TABL E 5-2 . SUMMAR YO F EPIDEMIOLOGICA L STUDIE S O N LEAD-EXPOSE DCHILDRE N (continued )
Stud y Population 3 Ai r Lead 0 (ug/m 3 ) BloodLea d (uy/dl ) Statistica l Mode l (Analyst ) Covariate s Measure d bloodLead / Ai r Leadblop e Billic ke t al. , U- 6 yr s n=178,53 3 1979 , 1980 ; living i nNYC Nathanso n4 Nudleman , 198 0 0.8-2. 5 (quarterl y

averages , 1970-1974 ) 20-3 3 Regressio nanalysi s (Brunekreef , 1984 ) Season , location , plu s adjustmen t fo r ag e S rac e 2. 9

Brunekree f e t al. . 198 3 4- 6 yr s n=19 5

living incity

cente r or insuburba nare a (Rotterdam ) .2 5 cit y .1 3 suburba n (6-mont havg. , lo w volume sampler 0 ) 13. 1 8. 2 Grou pmea ncomparison s Regressio nanalysi s (Brunekreef , 1984 ) Regressio nanalysi s (Brunekree f e t al. , 1983 , 1984 ) Age , drinkin g water , hous e paint , SES , parenta l exposure , locatio n -plu s adjustmen t fo r P b depositio noutdoors , ag e o f home , mil kconsumption , numbe r o f rooms , handdirt , mouthing behavior , pet s 24. 5 18. b 3.U-8. 5

a Refer s t o ag e o f childre nsampledan dsampl e size s (n) . °Represent s averag e level s measure deithe r a t variou s location s specifie di n"population " colum no r at variou s distance s fro

m specifie dpoin t sources . c Ai r leadlevel s sampledb y lo w volum e method s likel y

underestimate dlevel s tha t woul dhav e bee nmeasure db y hi-vol um e sampler s use dinothe r studies , especiall y nea r smelte r wher e large r leadparticle s predominate . Thi s coul dre sul t ininflate dblood/ai r leadratios . i •— • c * •^Estimate

db y interpolatio no f ai r qualit y dat a presented . e Base do

nonl y 3 sample s - blood/ai r lea dslop e fo r 197 7 base do nreductio no f ai r an dbloo dleada t 0.8-1.6k m fro m source .Typ e o fLocatio n (Study )

Bloo d Lea d (ug/dl) / Ag e (years ) Urba n Nea rPoin tSource(s ) <25/l- 7 8.5 a » b (Brunekree fe tal. , 1983 ) 3.6-4.0 a(Zielhui s e tal. , 1979 ; Brunekree f 

### e t al. , 1981 ) <2b/l-1 8 0. 6 (Angl e an d 0.66 a(Brunekreef , 198 4

1.4 aMclntire ; -2.63 afro m Angl e an d 

### 1.9 2 1979 , CD

) 2.10 a

### an

dMclntire- , 1979 ) 4_ ! 

### _U ) <25/10-1 5 - 2.4 6 (C D fro m Roel s e tal
. 1976 ) 5.3 a(Roel s e t al
. 198U ) « 5.9-9.8 a » b (Brunekreef , 198 4 fro m Roel s

e tal. , 1976 , 1978 , 1980 ) >25/0- 9 2. 9 (Billic k e tal. , 1979 , 1980 ; 1.07-1.5 2 (Yanke l e tal. , 1977 ; Walte re tal. , Nathanso n an d Nudleman , 1980 ) 1980 ; Snee , 1982b ; CD) 2.4-3.3 a(Brunekreef , 198 4 fro m Yanke l e tal. ,

1977 ) >25/l-1 8 - 2.6-3.7 a(Landriga n e tal
. 1975 ; Mors e e tal. , 1977 ) 4.6 a(Brunekreef , 198 4 fro m Roel s e tal. , 1976 ,

. 1978 , 1980 ) ^Slope s ar e i n unit s o fp g lead/d l bloo d pe rp g lead/n P air
. a "Aggregate " slope s derive d fro m grou p comparison s o rmultipl e regressio n analyse s tha twer e unadjuste d fo rsoi l o r dus tlead , thereb yattemptin g t o accoun tfo rinfluenc e o fdeposite d atmospheri clea d throug h thes e exposur e routes . Remainin g slope s represen trelationship s betwee n bloo d lea d an d ai rlea d du e solel yt o direc tinhalatio n whic h hav e bee n calculate d byadjustin g fo rth e influenc e o fsoi l and/o rdus tlead
. b Us e o flow-volum e particulat e sampler s likel yunderestimate d ai rlea d exposures , an d overestimate d th e 3 value , especiall ynea rpoin tsourc e wher e larg e particle s predominate
. < iP.6 6 V-1 8 Mclntire , 1979 ; Roel s e tal. , 1980 ) an d othe robservation s o fcurvilinea r bloo d lead/exposur e relationship s (Aza re tal. , 1975 ; Moor e e tal. , 1977 ; Gross , 1981 ; Sherloc k e tal. , 1982 ; Hammon d e tal. , 1981)
. A s discussed , th e C

D determine d tha tth e disaggregat e inhalatio n slope s derive d fro m th e studie s b yAngl e an d Mclntire , Roel s e tal. , an d Yanke l e tal
. ar e th e mos treliabl e give n thei roveral l quality
. I ti s importan tt o not e severa l additiona l studie s an d analyse s tha tma yprovid e equall yrelevan tan d usefu l informatio n fo rpurpose s o festimatin g a n aggregat e bloo d lead/ai rlea d slope
. Table s 5- 2 an d 5- 3 identif ysurvey s beside s thos e o fAngl e an d Mclntir e an d Roel s e tal
. whic h studie d childre n (0-1 0 yrs ) whos e bloo d lea d level s wer e belo w2 5 pg/dl
. Thes e studie s (Brunekree fe tal. , 1983 ; Zielhui s e tal
. 1979 ; Brunekree fe tal. , 1981 ) reporte d well-define d stud ypopulations , employe d availabl e qualit ycontro l procedure s fo rbloo d lea d analysis , an d measure d o rcontrolle d fo rimportan t covariate s (se e Tabl e 5-2)
. Severa l specifi ccomments shoul d b e mad e regardin g thes e studies : 1 . Th e serie s o fstudie s reporte d byZielhui s e tal
. (1979 ) an d Brunekree fe tal
. (1981 ) include d man yenvironmenta l measurement s (lea d i n ambien tan d indoo rair , lea d i n dustfal l indoor s an d outdoors , soil , streetdust , floordust , tapwater , an d dustines s o fhomes ) an d regressio n analyse s t o determin e th e impac to fdifferen tvariable s o n PbB level s (i.e. , th e abov e environmenta l indice s as wel l as distanc e fro m th e smelter , parenta l education , ay e o fth e child , mouthin g activity , cleanlines s o fth e child)
. Venou s bloo d lea d sample s wer e analyze d bystandar d technique s an d althoug h informatio n o n interlaborator ycomparison s i s no tgive n i n th e origina l study , qualit ycontro l participatio n i s reporte d byon e o fth e investigator s i n a subsequen trevie w(Brunekreef , 1984)
. Ai rlea d wa sP.6 7 V-1 9
measure d a ttw o site s i n 1976 , an d i n 1977 , 0. 2 an d 0. 4 k m fro m th e smelter
. Th e level s i n Tabl e 5- 2 wer e take n fro m Brunekree f(1984 ) an d represen t thos e measure d a t0. 4 k m fro m th e smelter
. Ai rlea d wa s measure d a t6 site s continuousl yfo r2 month s i n 1978 . Brunekree f(1984 ) estimate s 3 = 4. 0 fo r197 6 byassumin g a differenc e o f2. 0 pg/m ^ i n averag e a i rlea d exposur e level s betwee n th e 2- 3 yea rol d childre n wit h th e highes t an d lowes tPbB levels
. Afte radjustmen tfo rparenta l education , th e bloo d lea d differenc e o fabou t8 ug/d l decrease d t o 7. 2 ug/dl , resultin g i n a slightl ylowe r3 estimat e (3.6)
. Fo r1977 , a differenc e o f1. 0 ug/n P wa s assume d fo rai rlea d exposur e level s betwee n smelte ran d contro l childre n age d 2- 3 year s wh o had PbB level s o f18. 2 an d 14. 6 ug/dl , respectively , agai n resultin g i n a 3 o f3.6 . I n 1978 , onl ychildre n livin g betwee n U. 4 an d 1. 0 k m o fth e smelte rwer e sample d an d ai rlevel s di d no tcorrelat e wit h bloo d lea d withi n thi s population
. Thus , n o direc testimat e o f3 ca n b e derived , althoug h soi l lea d an d indoo ran d outdoo rdus tlead , an d therefore , accumulate d lea d deposition , accounte d fo ra significan tfractio n o fth e varianc e i n PbB level s (Brunekree fe tal. , 1981)
. 2 . Th e mor e recen tstud ybyBrunekree fe tal
. (1983 ) o n Dutc h cit yan d suburba n childre n measure d venou s bloo d (whic h wa s analyze d as par to f th e Europea n Communitylaborator yqualit ycontro l program ) an d man y environmenta l an d socia l variable s an d potentia l confounder s (lea d i n drinkin g water , soil , stree tan d playgroun d dust , han d dust , indoo rdust , mouthin g behavior , dietar yintakes , parenta l educatio n an d occupation , ag e o fhome , etc)
. Th e ver yhig h 3 valu e (8.5 ) derive d byBrunekree f(1984 ) eve n afte radjustmen ti n a multipl e regressio n analysi s fo rsi xo ftn e confounders , ma

yb e relate d t o a n underestimatio n o fambien tai rlea d level s du e t o th e fac ttha tlo wvolum e Britis h Smok e ai rmonitor s wer eP.6 8 V-2 0 employed , i n contras tt o th e hi-vo l sampler s use d i n mos tothe rstudies
. Th e exten to finflatio n i n th e estimate d slop e as a resul to fan yunderestimate d ai rlea d leve l i s uncertain
. Brunekree f(1984 ) note s howeve rtha teve n i f thi s bia s i s accounte d for , th e differenc e i n urba n an d suburba n ai rlea d level s wa

s probabl yno tlarge rtha n 0. 2 ug/m-^
. Th e contras ti n lea d depositio n betwee n th e area s wa s significan t(i.e. , 64 3 vs . 22 0 mg/m^/day) , indicatin g tha tongoin g lea d pollutio n accounte d fo ra goo d dea l o fth e difference s i n PbB levels , althoug h variation s i n historica l emission s ca n no tb e entirel yrule d out . Th e relativel ylo wPb B level s i n thi s stud y ( « 8-1 3 ug/dl ) coul d b e anothe rpartia l explanatio n o fth e hig h 3 estimates , yive n tha tothe rstudie s use d t o deriv e 3 include d childre n wit h PbB level s o n averag e close rto , an d above , 3 0 ug/dl , a twhic h poin tth e bloo d lead/lea d intak e relationshi p i s estimate d t o leve l off ; belo w3 0 ug/dl , thi s relationshi p appear s t o b e approximatel ylinea r(CD , p . 11-104)
. I n additio n t o thes e studies , th e availabl e statistica l aggregat e analyse s o n th e criteri a document' s thre e "ke yinhalatio n slope " studie s o n childre n requir e brie fdiscussion
. 3 . Th e thre e inhalatio n 3 value s (0.6 , 1.92 , an d 4.40 ) attribute d t o regressio n analyse s performe d byAngl e an d Mclntir e (1979 ) (CD , Tabl e 11-39 ) al l include d adjustment s fo rsoi l an d hous e dus tlead
. A n unadjuste d regressio n analysi s foun d a 3 o f1. 4 fo r6-1 8 yea rold s (Angl e an d Mclntire , 1979)
. Unadjuste d coefficient s o f0.6 6 (al l children) , -2.6 3 (1- 5 y rolds ) an d 2.1 0 (6-1 8 yea rolds ) wer e obtaine d b yBrunekree f(1984)
. Th e surprisin g 3 fo rth e 1- 5 yea rold s coul d b e du e t o th e fac ttha tthi s ag e grou p wa s onl y sample d durin g on e year , wherea s samplin g o folde rchildre n wa s performe d ove r6 years . Brunekreef' s reanalysi s illustrate s tw o points : 1 ) an yslop eP.6 9 V-2 1 derive d fo ral l childre n i n th e stud y(1-1 8 yrs ) likel yi s deflate d by includin g th e discrepan tresult s o fth e 1- 5 yea rolds ; an d 2 ) byadjustin g fo rfactor s tha tcovar ywit h ai rlea d (soi l an d hous e dus tlead ) i n th e analysis , th e slop e fo rai rlea d decrease d three-fol d fro m 2.1 0 t o 0.6 9 i n th e 6-1 8 yea rolds
. 4 . Th e inhalatio n 3 valu e o f2.4 6 fro m Roel s e tal
. (1976 ) wa s estimate d i n th e C

D byadjustin g fo rdus tlea d level s measure d o n th e children' s hands
. A

n unadjuste d regressio n analysi s byth e author s o fth e combine d dat a (197 6 throug h 1980 ) yielde d a 3 valu e o f5. 3 (Roel s e tal. , 1980)
. Brunekree f(1984 ) segregate d th e dat a an d compare d group s wit h larg e difference s i n exposur e (i.e. , < 1 k m fro m smelte rvs . urban/rural ; 3 " 5.9 ) group s wit h smal l difference s i n exposur e a thig h exposur e level s (i.e. , < 1 k m vs . 2. 5 k m fro m smelter ; 3 " 4.6 ) an d group s wit h smal l difference s i n exposure s a tlo wlevel s (i.e. , 2. 5 k m fro m smelter/urba n vs . urban/rural ; 3= 13.7)
. Th e hig h estimat e a tth e lowe rexposur e leve l i s influence d bytw o extrem e values ; removin g the m leave s a slop e o fapproximatel y9.8 . A s i n th e Brunekree fe tal
. (1983 ) study , th e us e o flow-volum e sampler s ma yhav e underestimate d ai rlea d exposures , an d overestimate d th e 3 value , especiall y fo rthos e childre n nea rth e smelte rwher e larg e particle s predominate
. Th e slop e ma

yb e underestimate d fo ryoun g children , however , sinc e thi s stud y onl ysample d childre n olde rtha n 1 0 year s o fage . Give n thes e differen t factor s an d analyses , i ti s difficul tt o estimat e a singl e aggreyat e slop e fro m Roel s e tal
. (1976 , 1980)
. I ti s clea rtha ta rany e o fpossibl e slope s fo rthi s stud yha s bee n calculate d tha tare dependen to n exposur e level s an d adjustment s fo rdus tlead , an d whic h ar e al l yreate rtha n th e slop e fo rinhale d ai rlea d alon e (2.46 ) cite d i n th e criteri a document
.P.7 0 V-2 2 5 . Analyse s o fth e Yanke l e tal
. (1977 ) dat a adjuste d fo rsoil'lead , cleanliness , dust , education , and/o rpic a hav e yielde d inhalatio n 3 estimate s rangin g betwee n 1.0 1 an d 1.5 3 a ta n ai rlea d leve l o f1.. 0 pg/m 3 (Yanke l e t al. , 1977 ; Snee , 1982 ; Walte re tal. , 1980 ; CD , Tabl e 11-39)
. Brunekree f (1984 ) estimate d 3 value s betwee n 2. 4 an d 3. 3 dependin g o n ag e afte rcomparin g th e highes tan d lowes texpose d children' s unadjuste d PbB level s base d o n th e 197 4 data
. Th e remainin g slope s liste d i n Tabl e 5- 3 ar e base d o n dat a fro m childre n whos e Pb

B levels , as som e i n Yanke l e tal
. (1977) , exceede d 2 5 pg/dl
. A s discusse d i n th e CD , th e relationshi p betwee n lea d uptak e an d PbB level s abov e abou t3 0 pg/d l appear s t o b e non-linea r(CD , p . 10-31)
. Becaus e PbB level s abov e 25-3 0 pg/d l excee d thos e wher e health-relate d concern s ar e triggere d (se e CD , Chapte r13) , thes e slope s ar e les s relevan tt o th e presen treview
. I n summary , th e analyse s usin g th e aggregat e approac h assum e th e sam e sourc e fo rmos tlea d i n air , soil , an d housedust , an d tha tadjustmen t o f PbB level s fo rsoi l o rdus tlea d tha tyield s a n inhalatio n slop e under estimate s th e "true " impac to fatmospheri clea d o n PbB levels
. Arang e o f value s ca n b e estimate d fro m a ) additional , an d apparentl yrelevant , studie s no tuse d t o deriv e inhalatio n slope s i n th e C D (i.e. , Zielhui s e tal. , 1979 ; Brunekree fe tal. , 1981 , 1983 ) an d b ) aggregat e analyse s tha tinclud e bot h direc t(inhalation ) an d indirec t(vi a soil , dust , etc. ) ai rlea d contribution s i n th e ke y"inhalatio n slope " studie s cite d i n th e criteri a document
. Althoug h fa rfro m conclusive , thes e studie s an d analyse s sugges t a rang e o fpossibl e bloo d lead/ai rlea d aggregat e slope s i n th e rang e o f2 t o 1 0 fo ryoung , moderatel yexpose d childre n wit h th e mos treliabl e slope s fallin g betwee n 3 an d 5 (CD , p . 11-104)
.V-2 3

2 . Predictin g Children' s Bloo d Lea d Level s Usin g Aggregat e Mode l To predic tPbB level s associate d wit h alternativ e ai rlea d level s usin g tnes e aggreyat e slopes , i ti s necessar yt o estimat e th e contributio n t o tota l lea d exposur e fro m emissio n source s no t subjec t t o contro l by implementin ya n ai rqualit ystandard , fo rexample , lead-soldere d foo d cans , lea d plumbing , an d lead-base d paint
. I tshoul d b e note d tha tbyusin g measure d lea d concentration s i n dus tfro m a wid e rang e o flocation s an d conditions , th e integrate d uptak e mode l discusse d i n th e previou s sectio n implicitl yinclude s averag e contribution s t o tota l exposur e fro m lead-base d paint , bu texclude s fro m th e analysi s hig h leve l exposure s associate d wit h deteriorate d lead-base d painte d housing
. Severa l difficultie s aris e i n attemptin g t o explicitl yestimat e exposure s fro m non-ai rsource s o flead : 1 ) Wit h th e exceptio n o fnon-ai rlea d i n diet , fe wstudie s provid e detaile d informatio n o n th e relativ e contributio n o fvariou s source s t o children' s Pb

B level s i n th e U.S
. Estimate s mus tb e mad e D yinferenc e fro m earlie rsurve ydata ; an d 2 ) Becaus e non-ai rcontribution s t o PbB level s probabl yvar ywidel y i n spac e an d tim e amon g children , a singl e estimat e fo rth e averag e cas e ma yresul ti n a lea d NAAQ S tha ti s no tprotectiv e fo ral l children
. [Thi s ca n b e expected , fo rexample , fo rchildre n wh o regularl yinges tlead-base d paint. ] Conversely , th e ai rstandar d wil l b e overprotectiv e i n area s wher e lea d fro m non-ai rsource s i s belo wth e average . I n settin g th e 197 8 lea d NAAQS , th e Agenc yestimate d tha tnon-ai r source s o flea d contribute d o n average , 1 2 pg/d l t o children' s Pb B levels
. Sinc e then , significan treduction s i n Pb B level s hav e occurred , attributabl e no tonl yt o decline s i n atmospheri clea d emission s bu tt o th e gradua lP.7 2 V-2 4 conversio n b ymanufacturer s t o non-lea d soldere d cans , i n som e cases'reductio n i n th e numbe ro fold , lead-painte d homes , cleane rworkin g conditions , as wel l as effort s byparent s an d publi chealt h agencie s t o minimiz e children' s lea d exposure . Furthe rdecline s i n lea d exposur e ca n b e expecte d by199 0 as thes e trend s continu e an d lea d exposur e fro m drinkin g wate rdrops , du e no tonl yt o increase d awarenes s as a resul to fwidespread , mandate d publi cnotifications , bu tt o th e 198 6 Saf e Drinkin g Wate rAc tbannin g th e us e o flea d solde ran d pipe s i n ne

wconstructio n an d plumbin g repairs , an d t o reduction s i n wate r corrosivit ybypubli cwate rsupplier s as complianc e wit h th e revise d nationa l wate rregulation s fo rlea d begins
. Th e mos trecent , an d well-conducted , nationwid e surve yo fchildren' s PbB level s wa s th e Secon d Nationa l Healt h an d Nutritio n Evaluatio n Surve y(NHANES II ) o f197 6 t o 1980 . Appendi xC describe s analyse s tha ta ) start s wit h th e averag e PbB leve l fo rchildre n fro m 1978 , th e midpoin to fth e NHANE S I I survey , an d b ) estimate s a 199 0 PbB averag e by adjustin g th e 197 8 valu e t o accoun tfo rth e importan tchanges , summarize d below , i n lea d exposur e tha thav e recentl yoccurre d an d tha t ca n b e expecte d t o continue : 1 . Use o flea d i n gasolin e ha s decline d byabou t9 0 percen tsinc e 1978 ; thi s tren d wil l continu e u p throug h 1990-9 2 as complianc e wit h th e lea d i n gasolin e standar d i s complete d an d as th e flee to flead-burnin g car s shrinks
. A

s observe d durin g th e NHANE S I I surve yperio d (se e CD , Sectio n 11.3.6) , th e continue d dramati cdeclin e i n gasolin e lea d emission s i s predicte d t o paralle l a majo rshif ti n Pb B levels
. 2 . Asignifican treductio n i n dietar ylea d intak e ha s occurre d sinc e th e lat e 1970's , an d thi s tren d wil l continu e as atmospheri clea d emission s an d deposition , th e us e o flead-soldere d cans , an d lea d level s i n drinkin g wate ral l continu e t o decline
.P.7 3 V-2 5 » Th e derive d rany e o fmean Pb B level s fo rchildre n expecte d i n lyy u (3. 0 - 4. 7 py/dl ) reflect s chanye s tha thav e occurre d sinc e 1978 , an d tha t ar e expecte d t o continue , i n yasolin e lea d emission s an d depositio n an d canne d foo d technology
. Anyothe rchange s tha tar e mor e difficul tt o quantif yar e als o probabl yo flesse rimportanc e fo rth e bul k o fth e population , fo r example , an ychange s i n lead-painte d housin g ha s no tbee n significan to n an yscale
. Thi s rang e o f199 0 "baseline " averag e estimate s represent s th e mean PbB level s tha twoul d b e expecte d i n 199 0 i n U.S
. childre n no texpose d t o atmospheri clea d fro m lea d poin tsource s directl yo rindirectly , base d o n th e dat a an d assumption s presente d above
. Anothe rmetho d t o estimat e children' s mean "non-air " Pb B i s t o us e availabl e dat a o n typica l backgroun d level s o flea d i n food , water , dust , an d soi l ingeste d byU.S
. childre n an d th e relationshi p betwee n lea d take n u p throug h thes e medi a an d children' s Pb B levels
. Tabl e 13- 6 o f th e criteri a documen tuse s suc h dat a i n calculatin g a mean Pb B o f4.4 2 pg/d l t o b e expecte d a ta n ai rlea d leve l o fzero . Althoug h thi s valu e wa s calculate d base d o n 1983-8 4 FU Adat a o n lea d i n food , i ti s interestin g tha t i ti s withi n th e rang e describe d above
. Thi s rang e ca n b e use d i n th e aggregat e mode l approac h t o estimat e range s o fmean bloo d lea d level s unde r alternativ e ai rlea d exposure s i n th e followin g equation : mean Pb B = (3. 0 - 4. 7 pg/dl ) + ( 3 - 5 pg/d l pe rpg/m 3 ) Ai rP b I tmus tb e emphasize d tha tthes e estimate s fo rnon-ai rcontribution s t o averag e Pb

B level s represen taverag e values
. Man ychildre n ma

yb e a tris k fo rsignificantl yhighe rlea d exposure s tha tcanno tb e prevente d D yatmospheri c emissio n controls
. I n particular , thes e includ e childre n wh o liv e i n deteriorate d o rrecentl yresurface d lead-painte d housin g wh o deliberatel yo r inadvertentl yinges tpain tdus tthroug h norma l mouthin g activities , childre nP.7 4 

### V-2 6 expose d t o hiy h drinkin g wate rlea d level s fro m erodin g lea d pipe s o r solder s i n distributio n systems , childre n o fparent s wh o wor k i n lead-relate d industrie s and ar e exposed t o lea d dus ttha ti s subsequentl ycarrie d hom e o n clothing , o rchildre n livin g nea rlea d smelter s and othe rpoin t source s where historica l accumulation s o flea d ar e excessive
. I ti s importan ttha t othe rregulator yagencie s and publi chealt h programs , includin yothe rEP A components , responsibl e fo rminimizin g children' s lea d exposure s fro m non ai rsources , o rfro m historica l accumulation s o fatmospheri clea d deposition , maintai n o rincrease , where necessary , thei refforts
.P.7 5

V I
. VALIDATIO N O

F INTEGRATE D LEA

D UPTAKE/BIOKINETI C EXPOSUR E MODE L Whil e al l thre e modelin g approache s identifie d i n Sectio n II I ar e usefu l i n assessin g th e relativ e protectio n afforde d bydifferen t lea d NAAQS , th e aggregat e an d disaggregat e bloo d lead-ai rlea d model s ar e intende d t o b e "equilibrium " models
. However , w e kno wtha tther e i s a grea t dea l o fvariatio n i n pas tan d presen texposure s t o lea d fro m variou s source s an d pathways
. Ofth e three , th e uptake/biokineti cmode l ca n bes t estimat e th e change s ove rtim e o fbloo d lea d t o change s i n environmenta l lea d i n rapidl ydevelopin g youn g children
. Agenera l descriptio n o fth e mode l i s provide d i n Sectio n I Van d Appendi xA
. Averag e dail yuptak e fo ryoun g childre n i s calculate d unde r condition s specifie d i n term s o fambien tai rlea d levels , soi l an d dus t lea d level s tha tcorrespon d t o bot h historica l an d curren tatmospheri clea d emissions , an d dietar ylea d level s fro m bot h wate ran d food
. Additiona l exposure s t o pain tlea d o rsecondar yoccupationa l source s (e.g. , dus t tracke d int o homes byworkers ) ca n b e added
. Bloo d lea d (PbB ) level s i n population s o fyoun g children , wh o ar e th e mos texpose d an d highl y susceptibl e t o lead , ar e estimate d ove rtim e base d o n tota l dail ylea d uptak e usin g a biokineti ccompartmenta l model
. Parameter s suc h as indoo rai rlea d exposure , tim e spen tindoor s vs . outdoors , absorptio n rate s throug h th e lun g o rgastrointestina l tract , an d amoun to fdir tchildre n tha ttypicall yinges tthroug h hand-to-mout h activity , ar e estimate d fro m availabl e dat a i n th e literature , as summarize d i n Appendi xA
. I n thi s chapter , result s o fsevera l validatio n exercise s wher e predicte d an d observe d bloo d lead s wer e compare d ar e presented
. Th e mos tdetaile d analysi s wa

s performe d wit h dat a gathere d aroun d a smelte ri n Eas tHelena ,P.7 6 VI- 2 Montana
. Tw

o type s o fvalidatio n effort s wer e undertake n wit h thi s dat a set : 1 ) i n th e firs teffort , th e bes tdat a regardin g suc h mode l parameter s as observe d air , soil , an d dus tlea d exposur e estimate s wer e used ; 2 ) i n th e secon d validatio n effort , predicte d level s o fair , soi l an d dus tlevel s wer e use d t o estimat e PbB levels
. Th e latte rwor k wa s undertake n t o determin e ho wwel l th e mode l behave d whe n actua l measurement s o fnecessar yinpu tdat a ar e no tavailable
. Thi s was necessar ys o tha tth e reliabilit yo fth e mode l coul d b e assesse d fo rpolic yanalysi s purpose s whe n les s tha n ful l informatio n i s availabl e t o us e wit h th e model
. Also , presente d i n thi s sectio n ar e validatio n exercise s usin g observe d bloo d lea d estimate s i n location s othe r tha n Eas tHelena
. Whil e les s effor twa s undertake n i n thes e exercises , the ynonetheles s provid e additiona l informatio n o n th e reliabilit yo fth e mode l an d provid e insigh tregardin g th e sensitivit yo fth e mode l result s t o uncertaintie s i n th e inpu tdata
. Give n th e man yuncertaintie s i n th e inpu tdat a an d th e biologica l variabilit ytha tcanno tb e incorporated , th e result s o fth e validatio n exercise s presente d belo wreveal , tha tth e lea d uptake/biokineti cmode l perfor m quit e wel l i n predictin g mean bloo d lea d concentration s i n childre n livin g nea rpoin tsource s o flead
. A
. Validatio n Usin g 198 3 Eas tHelen a Dat a Th e dat a se tconsidere d firs ti s base d o n a 198 3 stud yi n whic h th e Montan a Departmen to fHealt h an d Environmenta l Science s (MDHES ) an d th e Center s fo rDiseas e Contro l (CDC) , i n cooperatio n wit h EPA , measure d bloo d lea d level s i n approximatel y40 0 childre n age s 1- 5 livin g aroun d th e ASARC

O lea d smelte ri n Eas tHelena
. Th e lea d conten to fsoi l an d dust s aroun d an d i n individua l home s wa s measured
. Airborn e lea d wa s measure d befor e an d durin g th e surve ya t8 sites
. Thre e stud yarea s wer e designate d accordin g t o thei rdistance s fro m th e smelter : Are a 1 , withi nP.7 7 VI- 3 1 mile - o fth e smelter ; Are a 2 , 1-2.2 5 mile s fro m th e smelter ; Are a 3 , mor e tha n 5 mile s fro m th e smelter
. Th e validatio n exercise s include d childre n fro m Area s 1 an d 2 only
. I n orde rt o estimat e 198 3 PbB level s i n th e Eas tHelen a childre n s o the ycoul d b e matche d agains tth e measure d Pb B levels , exposur e profile s wer e generate d extendin g as fa rbac k as 1978 , dependin g o n th e children' s ag e i n 198 3 an d thei rresidentia l location
. Afive-yea rdescriptio n o f monthl yambien tai rlea d concentration s throughou tth e stud yare a wa s generate d i n tw o ways : (1 ) us e o fth e Industria l Sourc e Complex-Long-Ter m (ISC-LT ) dispersio n mode l base d o n ai rlea d concentrations , sourc e samplin g dat a o fsmelte remissions , an d loca l meteorologica l data , an d accounte d fo r dr yatmospheri cdeposition
. Are a an d year-specifi cestimate s o fbackgroun d lea d contribution s (i.e. , mobil e sources , re-entraine d soil , loca l mino r poin tsources ) wer e als o include d t o accoun tfo rtota l ambien t exposure ; an d (2)-empirica l smoot h interpolatio n o fobserve d concentration s (Marcus , 1988c)
. Onl yon e site , abou t1/4 mil e fro m th e smelter , provide d sufficientl y complet e ai rqualit ydat a ove rth e perio d 1978-198 3 tha tcoul d b e considere d representativ e o fpopulatio n exposur e i n th e vicinit yo fth e monito r althoug h ai rlea d dat a wer e availabl e fro m monitor s i n te n othe rlocation s aroun d Eas tHelena
. Estimate s o fsoi l an d dus tlea d concentration s wer e als o obtaine d usin g tw o methodologies
. I n th e firs tcase , home-specifi cobserve d value s fo r soi l an d dus tlea d wer e used
. I n th e secon d case , soi l an d dus tlea d estimate s wer e mad e usin g model s develope d byMcLamb (1988 ) an d Marcu s (1988c ) tha tdescrib e soi l an d dus tlea d as a functio n o fambien tlead
. (Fo ra descriptio n o fthes e models , se e Appendi xB)
. Th e latte rapproac h wa s deemed necessar yt o determin e ho wwel l th e mode l predict s whe n ful lP.7 8 VI- 4 informatio n o n mode l input s i s no tavailable
. (Thi s i s indee d th e usua l ' situatio n whe n th e mode l i s use d t o asses s th e impact s o falternativ e regulator yprogram s o n mean bloo d lead s o fa populatio n o fchildren. ) Age-specifi cexposur e parameter s use d as inpu tto ' th e uptak e mode l ar e describe d i n Appendi xA
. Estimate s o fdietar ylea d intak e fo rdifferen t ag e group s betwee n 197 8 an d 1983 , liste d i n Tabl e A-2 , wer e calculate d throug h applicatio n o fth e Multipl e Sourc e Food Mode l develope d i n Chapte r7 o fth e CD
. Th e latte rmode l use s year-specifi cFD Adat a o n foo d lea d conten t (i.e. , marke tbaske tsurveys ) an d age-specifi cdat a o n dietar ypattern s throughou tchildhoo d an d ha s sinc e bee n validate d usin g recen t1984-8 5 dat a (Flege l e tal. , 1988)
. Th e contributio n o fdrinkin g wate rt o dietar y lea d exposur e wa

s estimate d fo ra n averag e ta p wate rlea d concentratio n o f1 2 pg/1 , whic h wa s th e leve l reporte d fo rth e Stat e o fMontan a i n 1983 . Th e criteri a fo rvalidatio n nee d t o b e carefull ydefined
. Ther e i s a grea t dea l o findividua l variabilit yi n PbB levels , eve n wit h availabl e estimate s o flea d concentration s i n exposur e pathway s suc h as air , dust , an d soil
. Th e variabilit yi s attributabl e t o individua l biologica l variation , t o unknow n factor s mediatin g exposur e suc h as frequenc yo fhand-mout h contact , an d t o othe runattribute d source s o flead
. Eve n wit h goo d environmenta l data , th e fractio n o fvarianc e i n th e logarith m o fbloo d lea d tha ti s accounte d fo rb ya n optima l tota l uptak e regressio n mode l (multipl e R 2 ) rarel yexceed s 30% . Fo rth e Eas tHelen a data , R 2 = 0.2 8 i n th e bes tfittin g model s (Johnso n an d Wijnberg , 1988)
. Thus , i tdoe s no tsee m fruitfu l t o us e th e individua l predicte d PbB level s as a criterio n fo rmode l validation
. W e use d th e mor e realisti cgoa l o fmatchin g th e geometri cmean PbB fo rchildre n i n a larg e neighborhoo d tha twa s moderatel yhomogeneou s wit h respec tt o exposure .P.7 9 VI- 5 A,mor e globa l validatio n involve s comparin g th e cumulativ e distributio n functio n o fobserve d Pb B wit h tha to fth e individua l Pb B estimate s fro m th e uptake/biokineti cmodel
. Thes e comparison s fro m th e differen tvalidatio n run s ar e presente d i n Tabl e 6- 1 an d i n Figure s 6- 1 an d 6-2 . Th e simulation s wer e al l ru n a ttw o levels , on e wit h al l parameter s se tt o th e lowe rbound s fo ruptak e parameter s i n Appendi xA , an d th e secon d wit h al l parameter s se tt o th e uppe rboun d level s i n Appendi xA
. Th e midpoin to fth e all-lowe ran d all-uppe rboun d PbB estimates , i.e. , th e simpl e mean wa

s foun d t o b e th e bes tpredictor
. I n mode l ru n A , onl yobserve d value s fo rair , soi l an d dus tinpu t dat a wer e used
. Thi s dat a se twa s limite d t o th e 2 8 observation s nea rth e smelte rwher e a n ambien tmonito rwa s withi n a fewblock s o fth e homes
. Th e secon d mode l ru n include s observation s o n 29 9 children
. Thi s expande d dat a se twa

s obtaine d byusin g dispersio n modelin g technique s t o estimat e bloc k specifi cambien texposur e estimates. * Comparison s betwee n run s Aan d B illustrat e tha taccurat e Pb B reduction s resul tfro m usin g eithe robserve d o restimate d ambien tai rdata
. Ru n C , lik e ru n B , ha s 29 9 observations
. However , i n th e latte rmode l run , observe d measure s o fhousehold-specifi c soi l an d dus tlea d ar e replace d wit h estimate s obtaine d fro m equation s tha texplai n soi l an d dus tlea d level s as function s o fambien tlea d (se e Appendi xB)
. Also , whil e mode l ru n C use s dispersio n mode l estimate s o fambien tconcentrations , as doe s mode l ru n B , th e sourc e o fmeteorologica l
1 Asimila rvalidatio n exercis e wa s conducte d previousl ywher e averag e PbB level s predicte d byth e uptake/biokineti cmode l fo rdifferen tcensu s tract s wer e compare d t o measure d Pb B level s i n 1- 5 yea rold s livin g nea r tw o secondar ylea d smelter s an d i n a referenc e area , i n Dallas
. Result s wer e usefu l i n indicatin g tha tgreate rrefinemen ti n th e spatia l scal e woul d b e necessar yi n accuratel ymodelin g hig h exposur e situations
. Fo rth e Eas tHelen a analysis , an d i n subsequen tcase-stud ymodeling , th e highes tdegre e o fspatia l refinemen tpossibl e (i.e. , cit yblock s o r bloc k groups ) i s used
.

### TABL E 6-1 . COMPARISO NO F INTEGRATE D LEAD UPTAKE/BIOKINETI C MODE L PREDICTION S T O 198 3 MEASUREMENT S INEAS T HELENA Mode l Ru n Population 3 P b Ai rQualit y Dust/Soi l Lea d Predicte d vs . Measure d Averag e Bloo d Lead b an d GSD C A 2 8 childre n livin g i n

are a 1 aroun d singl e ai rmonito rwit h vali d dat a Measure d a tmonito r approx . 1/

4 mil e fro m smelte r Measure d i n an d outsid e individua l home s 16. 3 vs . 16. 5 pg/dl * 1.4 2 vs . 1.4 9
8 9 Are a 1 an d 21 0 Are a 2 Childre n

8 9 Are a 1 an d 21 0 Are a 2 Childre n Contributio n fro m smelte renissio n estimate d bydis - persio n mode l (loca l meteorolog ydata ) loca l backgroun d P

b level s (e.g., ' aut o anissions , fugitiv e dusts ) estimate d fro m 198 2 sourc e apportionmen tstud y Sam e as fo rRu n B excep ttha td i s persio n modelin g use d meteorologica l dat a fro m a nearb y a i rpor t Measure d i n an d outsid e individua l home s

Estimate d fro m generalize d air : soil/dus t P

b relationship s fro m regressio n analyse s o favailabl e dat a i n literatur e 9. 3 vs . 9. 3 pg/dl * 1.6 1 vs . 1.5 9

i cr\ 9. 5 vs . 9. 3 pg/dl * 1.6 7 vs . 1.6 9

Note : Dietar yP

b exposur e estimate d fo ral l mode l run s base d o n year-specifi canalyse s o f1980' s FD Afoo d concentratio n dat a an d foo d consumptio n dat a fro m Penninyto n (1983 , 1986) , an d U.S.D.A
. Nationwid e Foo d Consumptio n Survey , 1977-78 . a Area s as define d i n th e tex t b Geometri cmean s c Geometri cStandar d Deviatio n *A1 1 difference s statisticall yinsignificant ; t-test s o fdifference s o fmean s assumin g lognorma l bloo d lea d distributio n an d non-equa l variances
. lea d

o o oPM
VI- 7

10 0 9 0 -

U J 8 0 7 0 6 0 | 5 0 C C U J Q . 4 0 3 0 2 0 1 0 

## " I 1 L-.-4- * I

O - MODE L ESTIMAT E

•- OBSERVE D



### I

_ L J
_ 10 20 30 40

BLOO D LEAD CONCENTFIATION , ng/d l 5 0 6 0



### FIGUR E 6-1 . COMPARISO N O F DISTRIBUTION

OF MEASURE DBLOO DLEA DLEVEL S IN CHILDREN , 1- 5 YEAR S O F AGE , LIVINGWITHI N 2.2 5 MILE S OF E . HELEN A LEADSMELTE RVS . LEVEL S PREDICTE DB YUPTAKE/BIOKINETI C MODEL . MEASURE D SOI L AN DDUS T LEADLEVEL S WER E INCLUDE DI N ESTIMATINGUPTAK E LEVELS . (RU N B )P.8 2 '•» •" •I Wf VI- 8

U J 100 9 0 - 8 0 - 7 0 6 0 I - | .5 0 C C ' U J Q . 4 0 3 0 2 0 1 0 - _ » » m » * * ~ ~ ' '

O - MODE L ESTIMAT E

•- OBSERVE D

_ L 1 0 2 0 3 0 4 0

BLOO D LEA D CONCENTRATION , Hg/d l 5 0 60

FIGUR E 6-2 . COMPARISO N OF DISTRIBUTIO N OF MEASURED BLOO D LEAD LEVELS I N CHILDREN , 1- 5 YEAR S OF AGE , LIVIN G WITHI N 2.2 5 MILE S O F E . HELEN A LEAD SMELTE R VS . LEVELS PREDICTE D B YUPTAKE/RIOKINETI C MODEL . ESTIMATE D SOI L AN D DUS

TLEA D LEVELS FRO

M GENERALIZE D RELATIONSHIP S WER E INCLUDE D I N ESTIMATIN G UPTAK E LEVELS . (RU N C )P.8 3 

### VI- 9 dat a i s different : Ru n B use s loca l meteorologica l data , an d ru n C use s airpor tdata
. Thi s differenc e allow s run s B an d C result s t o b e compare d t o asses s ho

wsensitiv e bloo d lea d estimate s ar e t o les s location-specifi c meteorologica l data
. I n conclusion , generall ysatisfactor yresult s wer e obtaine d fo r predictin ygeometri cmeans . Mode l ru n Aca n b e considere d a "pure " validatio n ru n tha tuse s th e bes tinpu tdat a availabl e t o predic t mea n bloo d lead s whic h ca n b e compare d t o mea n observe d bloo d leads
. Mode l run s B an d C wer e necessar yvalidation s sinc e exac tpopulatio n locations , loca l meteorology , an d soi l an d dus tlea d dat a wil l rarel yb e availabl e fo rpoin t sourc e area s wher e th e mode l wil l b e use d fo rpolic y analysis
. Therefore , Ru n C ca n b e considere d a "generalize d methodology " fo r"export " o rapplicatio n t o othe rstud yareas . Althoug h th e difference s betwee n observe d an d predicte d mea n PbB level s ar e no t statisticall ysignificant , pos tho ccalibratio n o fth e mode l t o remov e an ydifference s wa

s considere d (Marcu s an d Holtzman , 1988)
. Bot h linea r an d nonlinea rmodel s wer e examine d an d i twa s foun d tha tcalibrate d model s (includin g age-dependen tones ) improve d predictiv e abilit yo fth e mode l onl ymarginally
. On e alternativ e i s t o simpl ysubtrac tth e differenc e betwee n observe d an d predicte d PbB level s i n th e generalize d methodolog y Ru n C ( =0. 2 pg/dl ) o rus e a multiplicativ e facto r(th e latte rprobabl y more appropriat e give n th e lognormalit yo fth e Pb B distribution)
. Suc h a calibratio n base d o n th e result s o fa single , albei tlarg e an d detailed , validatio n ma

yb e inappropriate , especiall yconsiderin g th e uncertaintie s inheren ti n suc h modelin g exercise s (e.g. , a "positive " calibratio n ma y b e neede d i n a differen tlocation)
. Give n thes e uncertainties , n o pos t ho ccalibratio n o fcas e stud yexposur e estimate s i s currentl ybein g propose d althouy h suc h a n adjustmen tcoul d easil yb e accommodate d i fP.8 4 VI-1 0
decide d upon . Severa l sensitivit yrun s wer e mad e i n orde rt o "fine-tune " variou s parameter s fo rwhic h dat a ar e incomplet e suc h as age-specifi cdir t consumptio n rate s an d gu tabsorptio n rate s fo ringeste d lead
. Fo rexample , i n estimatin g th e rat e bywhic h ingeste d lea d i s absorbed , th e criteri a documen tidentifie s man yfactor s tha thav e t o b e considered , amon g the m person' s age , physiologica l status , mediu m fo rth e lea d (e.g. , foo d vs . pain to r"dirt") , coinciden tingestio n o fothe relement s i n foo d (e.g. , calcium ) whic h compet e wit h lea d fo rintestina l absorptio n sites , an d th e non-linea rrelationshi p betwee n lea d intak e an d bloo d lea d (du e fo rexampl e t o a saturabl e gu tabsorptio n pathway)
. Difference s ma yals o b e attributabl e t o physica l o rchemica l difference s i n bioavailabilit yo fdepositio n fro m smelte ranissions , o rt o th e highe rrat e o fintak e i n thes e area s compare d t o typica l situations
. I n fact , ther e ar e reason s t o believ e tha tsuc h difference s mus texis t i n Eas tHelena
. Th e lead-bearin g particle s tha tar e deposite d nea rth e smelte rare

probabl ylarge rparticle s fro m fugitiv e emission s (e.g. , erosio n fro m tailing s piles , loadin g operations ) wherea s th e mor e distan tdeposit s ar e predominantl ysmalle rparticle s fro m stac k emissions
. Ye tanothe r facto ri s tha tparent s o fchildre n wh o live d close rt o th e smelte r(e.g. , Are a 1 ) ma

yhav e bee n mor e sensitize d t o lea d exposur e an d thu s tende d t o contro l acces s t o leade d soi l an d dus tmor e tha n parent s i n Are a 2)
. T o tes tthis , w

e ra n th e mode l wit h 20% gu tabsorptio n o fdir t lea d i n Are a 1 an d 30 % absorptio n i n Are a 2 . Tw o additiona l run s wer e mad e i n whic h th e sam e absorptio n factor , eithe r25

% o r30% , wa

s use d fo rbot h areas . Area-specifi cresult s o fth e 20 % (Are a 1 ) /

30 % (Are a 2 ) mode l wer e no tsignificantl ydifferen tfro m th eP.8 5 VI-1 1
observe d geometri cmeans . Likewise , usin g a 25 % absorptio n facto rfo rbot h area s yielde d n o significan tdifferenc e betwee n predicte d an d observe d geometri cmean s fo rth e overal l stud yarea . Result s usin g th e 3U % rat e cite d I n th e C

D base d o n indirec tchemica l an d anima l experiment s wer e no ta s concordant
. Becaus e o fth e programmin g complexitie s tha twoul d b e introduce d i fdua l absorptio n rate s wer e use d i n al l othe rapplication s o fth e model , a 25% absorptio n rat e i s chose n fo rgenera l us e sinc e i t yielde d adequat e overal l results
. A s indicate d i n Sectio n III , th e mode l shoul d b e regarde d as vali d fo r estimatin g mean response s an d i tdoe s appea rtha twit h th e correc trang e o f soi l an d dus tlea d inputs , th e mode l adequatel ypredict s th e geometri cmean o fth e observe d distribution
. Estimatio n o fth e hiyhe rpercentile s o fth e Pb B distributio n require s application , t o th e yeometri cmean , o fa GS U from , fo rexample , NHANE

S I I o rexposur e survey s aroun d differen tpoin tsources . B
. Applicatio n o fUptake/Biokineti cMode l t o Othe rDat a Set s Ther e ar e othe rpublishe d dat a t o tes tth e uptake/biokineti c mode l a tothe rU.S
. location s an d times
. One dat a se twa s collecte d i n Omaha , Nebraska , fro m 197 1 t o 197 7 (Angl e an d Mclntire , 1979 ; Angl e e tal. , 1984)
. Anothe rdat a se twa s collecte d throughou tSilve rValley , Idaho , i n 1974-197 5 an d i s describe d i n Yanke l e tal
. (1977) , an d Walte re tal
. (1980 ) wit h additiona l informatio n give n i n th e CD
. 1 . Omah

a Dat a Th e Omah

a stud ymeasure d bloo d lead s i n 24 2 childre n age s 1- 5 year s an d 83 2 childre n age s 6-1 8 years . Th e childre n wer e a t3 locations , denote d C (commercia l are a nea ra smal l batter yplant) , M (mixe d residential commercial) , an d S (suburban)
. Ai rlead , soi l lead , an d hous e dus tlea dP.8 6 VI-1 2

measure d i n eac h are a ar e incorporate d int o th e mode l t o estimat e averag e dail ylea d uptak e levels
. Thes e dat a ar e les s satisfactor yfo r testin g th e mode l tha n th e Eas tHelen a dat a becaus e th e soi l an d dus t lea d measurement s ar e no tspecifi ct o eac h househol d wher e bloo d lead s wer e taken
. Furthermore , th e stud ywa s no t designe d fo rcontrolle d geographi ccomparison s give n th e significan tdemographi cdifferenc e betwee n area s i n SES , housing , an d racia l composition
. Age-specifi c dietar ylea d intake s wer e estimate d base d o n 1970' s dat a fro m th e FD Aan d Jeline k (1982 ) as re-analyze d i n th e CD
. I n Tabl e 6-2 , th e observe d geometri cmean bloo d lea d level s fo r1- 5 yea rold s ar e compare d t o predicte d mean Pb B level s fo r2-yea rold s i n th e suburba n an d mixe d area s (bloo d lea d dat a fo r1- 5 yea rold s wer e no treporte d fo rth e commercia l area)
. Th e mode l appear s adequat e fo rth e suburba n site , whil e averag e bloo d lea d estimate d fro m reporte d soil , dust , an d ai rlea d concentration s i s significantl yunderpredicte d fo rth e "mixed " site
. Ther e ar e severa l factor s tha tma yexplai n th e contras ti n PbB level s betwee n th e area s despit e th e apparen tsimilaritie s i n environmenta l lea d levels , fo rexample : 1 ) Ai rlea d level s i n th e mixe d are a wer e apparentl ymuch highe rtha n th e suburba n sit e i n year s prio rt o 197 2 whe n soil , dust , an d bloo d lea d measurement s wer e take n (e.g. , 1.4 4 pg/m 3 i n mixe d vs . 0.7 3 pg/m 3 i n suburba n i n 197U)
. Thus , th e highe rbloo d lead s i n th e mixe d are a ma y reflec thighe rhistorica l exposure ; 2 ) Th e populatio n i n th e mixe d are a wa s predominatel yblac k wit h a larg e percentag e o fsubstandar d housin g compare d t o th e suburba n are a whic h wa s predominatel ywhite
. Bloo d lea d level s ar e highl ydependen to n demoyrapni cvariable s suc h as SES , race , housin yconditions , parenta l car e an d nutrition , al l o fwhic h wer e likel yTABLE 6-2 . CHILDREN' S BLOO D LEA D LEVEL S MEASURE

D I N OMAHA

, 1971-197 7 VS
. INTEGRATE D UPTAKE/BIOKINETI C MODE LPREDICTION S
Averag e Ai rLea d (pg/m 3 ) Averag e Soi l Lea d (ppm ) Averag e Hous e Dus tLead (ppm ) Observe d Mean PbB (pg/dl ) 1- 5 yr . old s Predicte d Mean * PbB (pg/dl ) 2 yr . old s "Mixed " Sit e 0.2 6 21 3 65 3 25. 6 20. 2 Suburba n Sit e 

### 0.3 7 11 0 56 7 

### 14. 6 15. 1 Estimate d Dietar yLea d Uptak e (pg/day ) fo r bot h site s durin g earl y1970' s (se e text ) 0- 1 yr . old s 1- 2 yr . old s 2- 3 yr . old s 

### 16. 3 - 

### 20. 6

20. 2 - 

### 25. 6 16. 6 - 

### 22. 1 

### < M I

^Predicte d mean PbB represent s midpoin to flowe ran d uppe rboun d mean s estimate d bymode lP.8 8
VI-1 4 t o hav e had systanati cinteractiv e influence s i n th e Omah a stud yareas ; 3 ) Othe runmeasure d variable s ma yhav e differe d betwee n th e area s suc h as drinkin g wate rlevel s (olde rhome s i n mixe d are a ma

yhav e had lea d plumbing) , pain tlead , frequenc yo fcanne d food s i n diets ; 4 ) Possibl e measuremen t erro rrelate d t o th e fac ttha tmos thousedus tsample s wer e collecte d fro m vacuu m cleane rbags
. Ther e ma yhav e bee n difference s betwee n area s i n floo rsurface s (carpe tvs . wood ) o rfrequenc yo fvacuuming , fo rexample
. 2 . Silve rValle yDat a Th e Silve rValle ystud yo f197 4 an d 197 5 covere d 86 0 childre n age s 1- 9 year s livin g nea rth e lea d smelte ri n Kellogg , Idah o an d surroundin g regions
. PbB level s wer e quit e hig n fo rchildre n neares tth e smelter
. Househol d dustiness , soi l lead , an d estimate d o robserve d ai rlea d concentration s wer e obtaine d fo r9 zone s aroun d th e smelte ran d use d t o calculat e dail y lea d uptak e levels
. A s fo rth e Omah

a comparison , dietar ylea d intake s wer e calculate d fro m 1970' s dat a analyze d i n th e criteri a document
. Th e geometri cmean value s byzon e ar e show n i n Tabl e 6-3 , alon g wit h predicte d mean Pb B usin g th e uptake/biokineti cmodel. - Result s ar e generall yadequat e fo rth e mor e distan tarea s wit h lowe rexposur e levels
. Thi s i s th e intende d rang e o fapplicabilit yo fth e model
. I ti s no tsurprisin g tha t bloo d lead s are

overpredicte d i n area s I an d I I locate d closes tt o th e smelter
. Th e Harle yan d Knei p compartmenta l model' s presumptio n o flinea r kinetic s i n lea d absorption , excretion , an d accumulation , whil e appropriat e a trelativel ylo wt o moderat e exposure s i s no tapplicabl e fo rsuc h extra ordinaril ynig h exposur e level s a s observe d i n thes e tw o areas . Some adjustmen tfo rth e non-linea rpattern s o flea d uptak e woul d b e necessar yi n orde rt o reliabl ymode l Pb B level s i n locale s wit h suc h extremel yhig hTABL E 6-3 . CHILDREN' S BLOOD LEA D LEVEL S MEASURE D I NSILVE R VALLEY , MONTAN A1974-197 5 VS . INTEGRATE D UPTAKE/BIOKINETI C MODE L PREDICTIONS

Averag e Ai r Lea

d (pg/m 3 ) Averag e Soi l Lea

d (ppm ) Averag e Hous e Dus t Lea d (ppm ) Observe d Pb

B (pg/dl ) 2-yr . old s Predicte d Mean PbB * (py/dl ) 2-yr . old s 

### Are a 

## I _ 16. 8 7,47 0 11.7U 0 

### II

_ 14. 2 3,30 0 10,30 U 

### II I

6. 6 1,25 0 2,40 0 

### IV

_ 3. 0 1,40 0 3,3U 0 

# y _ 0. 7 0 2,30 0 3,40 0 

## yj

_ 0. 5 33 7 1,80 0 

### VI I

0. 5 70 0 3,90 0 72 88. 5 

### 5 1

74. 1 36

28. 4 

### 3 6

33. 7 35

34. 6 2 6

22. 3 35

35. 8 Estimate d Dietar yLea d Uptak e (pg/day ) fo r al l site s durin g earl y1970' s (se e text ) 0- 1 yr . old s 1- 2 yr . old s 2- 3 yr . old s 

### 16. 3 - 20. 6

20. 2 - 25. 6 16. 6 - 22. 1 < M I r — U l

*Predicte d mean Pb

B represent s midpoin to flowe ran d uppe rboun d mean s estimate d bymodel
.P.9 0 

### VI-1 6 air , soil , and/o rdus tlea d concentrations
. 3 . Othe rDat a Unpublishe d analyse s byPhillip s an d Vornber g e tal
. (1986 ) fo r population s livin g nea ra larg e industria l lea d sourc e i n Herculaneum , Missouri , an d hav e similarl yprovide d fairl ygoo d validatio n fo rth e uptake/biokineti cmodel , especiall ywhe n measure d soi l an d dus tlea d value s wer e available
. C
. Conclusion s Th e abov e discussio n illustrate d severa l validatio n exercise s tha t wer e undertake n t o refin e dat a input s an d t o asses s th e reliabilit yo fth e bloo d lea d uptake/biokineti cmodel
. Th e Eas tHelen a analysi s wa s byfa rth e mos tintensiv e effort
. Th e result s o fth e analysi s indicate d tha t th e model , usin yth e bes tavailabl e an d location-specifi cinpu tdata , predicte d overal l mean s essentiall yidentica l t o th e observe d bloo d leads
. Whe n usin yles s location-specifi cinpu tdat a (tha ti s generall yavailabl e fo rpolic yanalyses) , th e mode l predict s mean Pb B level s withi n 2 percen to fobserved
. Othe r validatio n efforts , thoug h undertake n wit h les s effort , o fdat a fro m Omah a an d Silve rValle yals o suppor tth e hypothesi s tha tth e uptake/biokineti c mode l i s reasonabl e fo restimatin g bloo d lead s whe n actua l observation s ar e no tavailable
. Othe rindependen tvalidatio n effort s byTR C hav e als o provide d genera l suppor tfo rth e efficac yo fth e mode l
.P.9 1

VII
. CONCLUSIONS AND APPLICATION S O F LEA D EXPOSUR

E MODELING Becaus e o fth e pervasivenes s o flea d i n th e environment , a lary e numbe r an d variet yo fexposur e situation s requir e som e understandin g no tonl yi n term s o fpresen trisk s bu tfo rpredictin g hazard s unde rfutur e regulatory / abatemen talternatives
. Mor e tha n perhap s an yothe renvironmenta l con taminant , a wealt h o finformatio n has accumulate d no tonl yo n lea d toxicit y bu to n lea d exposur e as well
. Thi s repor thas attempte d t o utiliz e th e mos t reliabl e o ftha tinformatio n t o develo p multi-medi a exposur e methodoloyie s t o asses s risk s associate d wit h alternativ e lea d NAAQ S an d whic h ca n b e applicabl e t o othe rlea d exposur e scenarios
. Fo rexample , bloo d lea d level s i n childre n expose d t o differen tdrinkin g wate rconcentration s hav e bee n estimate d i n EPA' s recen trevie wo fth e lea d i n drinkin g wate rregulatio n byadoptin g bot h th e disaggregat e an d th e uptake/biokineti cmodelin g approaches
. Eac h o fth e thre e approache s describe d her e ha s bot h advantage s an d uncertainties
. Th e aggregat e model , fo rexample , allow s fo ra straight forwar d conversio n o fai rlea d concentratio n change s t o th e rang e o fexpecte d impact s o n children' s bloo d lea d level s throug h direc tan d indirec tsources . However , projectin g i n thi s approac h wha tcontributio n non-ai rsource s o f lea d wil l mak

e t o futur e PbB level s require s fairl ygoo d dat a o n curren t exposure s as wel l as trend s i n differen texposur e sources . Also , sinc e soi l lea d change s relativel yslowl yi n respons e t o decrease s i n ai rlead , th e chang e i n bloo d lea d calculate d fro m th e aggregat e mode l ma yno tb e achieve d fo ra ver ylon g time
. Th e disaggregat e model , wit h rapi d chang e i n dus t lea d an d slowe rchang e i n soi l lead , ma yb e a more accurat e predicto r o fnear-ter m effect s o fai rlea d change s o n bloo d lea d levels
. Th e uptake / biokineti cmodel , as wit h th e othe rapproaches , als o mus trel yo n incomplet eP.9 2 

### VII- 2 dat a i n som e case s an d becaus e o fit s assumption s o flinea rabsorptib n an d biokinetics , i s limite d t o predictin g relativel ylo wleve l exposure s (i.e. , < 25-3 0 pg/dl)
. Th e model' s mathematica l assumption s an d numerica l parameters , however , combin e plausibl e biologica l hypotheses , anima l experimenta l data , an d result s o fobservationa l studies
. Further , i tallow s explici tprojection s o ffutur e lea d concentration s i n variou s medi a an d i n tur n estimation s o f th e impact s o fthes e differen tchange s o n differen tag e group s o fchildren
. I ti s thi s flexibilit ytha tmake s th e integrate d uptake/biokineti cmode l adaptabl e fo ra wid e rang e o fpredictiv e exposur e assessment s an d whyi t was th e focu s o fth e validatio n exercise s describe d i n Sectio n VI
. Result s o fth e differen tvalidation s indicat e goo d concordanc e betwee n observe d an d predicte d averag e PbB level s i n childre n livin g nea rlea d poin t sources . Th e mode l ca n als o b e a usefu l too l i n estimatin g PbB level s i n childre n livin ywit h differen tlea d hazards , suc h a s heavil ycontaminate d soil s fro m historica l depositio n nea rmajo rurba n roadway s o rclose d smelter s o rmines
. Ongoin g regulator yeffort s bydifferen tcomponent s o fEP At o contro l concentration s o flea d i n air , wate ran d soi l hav e create d a significan t nee d t o mode l bloo d lea d concentration s tha tdelineate s specifi croute s o f lea d exposure . A tpresent , onl yth e uptake/biokineti cmode l provide s suc h specificity
. Furthermore , suc h a mode l mus tb e capabl e o fsimulatin g bloo d lea d level s unde rfutur e as wel l as historicall yknow n exposur e regimes
. (Th e validatio n effort s describe d i n th e previou s sectio n use d historica l dat a t o tes tan d improv e th e predictiv e abilit yo fth e model. ) I n fact , a n earlie rbu tsimila rversio n o fth e uptake/biokineti cmode l ha s bee n applie d t o assessment s o fBosto n soi l contaminatio n (Bec k an d Tsai , 1987) , exposure s aroun d th e Herculaneum , Missour i smelte r(Phillip s an d Vornber ye tal. , 1986 ) an d historica l contaminatio n o fsoil s nea rth e Bunke rHil l smelte ri nP.9 3 

### VII- 3 Kellogg , Idah o an d as par to fEPA' s Integrate d Environmenta l Managemen t Progra m i n thei reffort s t o develo p an d appl ymethodologie s t o establis h publi chealt h an d environmenta l priorities
. Th e uptake/biokineti cmode l i s stil l bein g assesse d an d validatio n test s wil l continu e as ne wdat a ar e available
. I n particular , adjustment s o fdir tingestio n rat e an d dir tlea d absorptio n ma yb e desireabl e i n calibratin g th e air , dust , an d soi l lea d slope s relativ e t o observe d regressio n models
. Th e empirica l multipl e regressio n method s use d i n th e disaggregat e model s ma

yals o nee d refinement , e.g. , byus e o fstructura l equatio n analyse s tha texten d th e statistica l method s use d byth e Cincinnat i Lea d Progra m Projec t(Clar k

e tal. , 1987)
.P.9 4

APPENDIXA
. ESTIMATE S O F LEA D UPTAK E Fo reac h o fth e numbere d line s i n Tabl e 4- 1 i n th e integrate d lea d uptake / biokineti cmodel , th e assumption s an d estimate s use d i n calculatin g averag e lea d uptak e fo rchildre n fro m th e variou s exposur e pathway s ar e discusse d i n th e correspondingl ynumbere d paragraph s below
. Tabl e 4- 1 onl yillustrate s calculation s fo r2-yea rol d children ; i n orde rt o estimat e exposure s throughou tchildhood , age-specifi cexposur e parameter s ar e necessar yi n severa l cases . Thes e ar e als o describe d below
. 1 . Outdoo rai rlead : I n th e case-stud yexposur e analyse s o falternative , futur e regulator yscenarios , ambien tai rlea d concentration s wil l b e assigne d t o population s livin g i n differen tlocations , o r"recepto rpoints. " Location s wil l b e define d as bloc k grou p centroid s - i.e. , subdivisio n o fcensu s tracts . Ai rlea d level s wil l b e yenerate d aroun d individua l lea d poin tsource s throug h us e o fth e Industria l Sourc e Complex-Long-Ter m (ISC^-LT ) dispersio n model , base d o n site-specifi coperatin g parameters , emission s (bot h stac k an d fugitive) , an d meteorologica l data
. Backgroun d lea d concentration s fro m mobil e sources , re-entraine d soil , an d local , mino rpoin tsource s wil l als o b e included
. Th e ai rlea d concentration s specifie d i n Tabl e 4- 1 d o no trepresen texposur e scenario s fo ralternativ e lea d NAAQ S bu tstartin g point s t o illustrat e ho w dail ylea d uptak e estimate s ar e made
. 2 . Indoo rai rlead : Th e penetratio n o fatmospheri clea d int o residentia l structure s depend s o n th e siz e o fth e lea d particles , meteorologica l conditions , an d th e permeabilit yo fth e windows , doors , an d wall s o fth e home
. Arang e o findoor/outdoo rratio s has bee n foun d (0.3-0.8 ) fo rdifferen tcitie s an d structure s (CD , Tabl e 7-6)
. Nea rpoin tsource s wher e larg e airborn e particle s ar e mor e prevalen tan d infiltratio n int o home s i s low , th e rati o appear s t o b e close rt o 0. 3 (Cohe n an d Cohen , 1980)
.P.9 5 A- 2 3 . Tim e spen toutdoors : Th e amoun to ftim e spen tbetwee n indoo ran d outdoo renvironment s varie s amon g youn g childre n dependin g o n thei rstag e o fdevelopmen t(i.e. , infant , toddler , pre-school) , season , geographica l location , an d famil ybehavior
. Arang e o f2- 4 hour s pe rda yspen toutdoor s (an d therefor e 20-2 2 hour s spen tindoors ) i s considere d a reasonabl e averag e fo ra 2-yea rold
. Th e followin g age-specifi cestimate d range s fo rhour s spen t outdoor s wer e derive d fro m informa l surveyin g o fparents : ag e (years) : 0- 1 1- 2 2- 3 3- 7 tim e spen t ~L173 tt 2^5 outdoor s (hrs/day) : 4 . Tim e weighte d ai rlea d concentration s fo reac h leve l i s estimate d by : [(outdoo rconcentratio n xtim e spen toutdoors ) + (indoo rconcentratio n xtim e spen tindoors) ] * 2 4 hours
. 5 . Th e volum e o fai rbreathe d eac h dayi s dependen to n age , bod y size , lun g capacity , altitude , an d activit yo fth e child
. Fo rinstance , ventilator yvolum e ca n increas e three-fol d durin g strenuou s exercis e (Cotes , 1979)
. Phale n e tal
. (1985 ) determine d averag e ventilatio n rate s fo rmale s an d female s fro m birt h throug h ag e 1 8 fro m graphica l fit s o f publishe d tabulate d dat a (Altma n an d Dittmer , 1971 , 1972)
. Fo rexample , a two-yea rol d a t"lo wactivity " i s estimate d t o hav e a minut e ventilatio n rat e o f2.7 5 liters/minute , whic h correspond s t o a n averag e dail yrat e o f approximatel y4 m 3 /da ywhil e a three-yea rol d i s estimate d t o hav e a dail y rat e o f4. 3 m 3 /day
. Othe restimate s tha tappea ri n th e literatur e ar e 4. 7 m 3 /da y(ICRP , 1975 ) an d 4 t o 6 m 3 /da y(Nutritio n Foundation , 1982 ) fo r activ e one-yea rolds , an d 4. 7 m 3/da yfo ra three-yea rol d (Nutritio n Foundation , 1982)
. Thes e value s combine d wit h thos e determine d byPhale nP.9 6 A- 3
e tal'. , an d scalin g factor s base d o n bod ysiz e ar e use d t o construc ttn e followin g range s fo raverag e aye-specifi cdail yventilatio n rates . Aye (years) : 0- 1 1- 2 2- 3 3- 4 4- 6 5- 6 6- 7 Ventilatio n Rat e (m 3 /day) : 2- 3 3- 5 4- 5 4- 5 5- 7 5- 7 6- 8 6 . Th e rany e o ftota l lea d intak e byinhalatio n fo reac h ai rlea d leve l i s compute d bymultiplyin ybot h th e estimate d uppe ran d lowe rboun d time-weighte d averag e concentration s o fai rlea d byuppe ran d lowe rboun d estimate s o fth e volum e o fai rrespire d pe rday
. 7 . Respirator ydepositio n an d absorption : Onl ya portio n o finhale d lea d i s deposite d i n th e lung s an d subsequentl yabsorbe d int o th e bloodstream
. Th e depositio n efficienc yo flea d particle s depend s primaril yo n thei rsiz e an d th e physiolog yan d rat e o fbreathin g o fth e individual
. Availabl e dat a o n lea d particl e siz e distributions , particl e depositio n pattern s i n th e lung , an d respirator yabsorptio n o flea d particle s wer e use d t o estimat e depositio n efficiencie s o fairborn e lea d particle s i n youn ychildre n (Cohen , 1987)
. Arespirator ydeposition/absorptio n rat e o f2 b t o 45 % i s calculate d fo ryoun ychildre n livin yi n non-poin tsourc e areas , whil e a rat e o f42 % i s calculate d fo rthos e livin ynea rpoin tsources . 8 . Tota l lea d uptak e fro m th e ai ri s th e produc to ftota l intak e an d th e lun g deposition/absorptio n factor
. 9 . Averag e dietar ylea d consumption : Give n th e wid e spatia l an d tempora l distributio n o ffoo d i n thi s country , i tappear s reasonabl e t o assum e tha t eve n peopl e livin g nea rindustria l lea d source s receiv e roughl ytypica l lea d level s fro m thei rdiet
. Anyvariabilit ydu e t o loca l contaminatio n o f garde n crop s o rkitchen s nea rpoin tsource s ca n b e factore d i n separately
.P.9 7
A- 4 A s note d i n Sectio n II.D. , th e Multipl e Sourc e Food Mode l develope d i n th e C D ha s bee n validate d an d update d usin g th e mos trecen tfoo d dat a fro m 198 4 an d 198 5 (Flege l e tal. , 1988)
. Furthe rdecline s i n dietar ylea d intak e ar e expecte d as a resul to fcontinuin g reduction s o flea d i n canne d foods , gasolin e anissions , an d lea d i n drinkin g water . Cohe n (1988) , use s availabl e dat a o n thes e downward trend s an d informatio n fro m th e Multipl e Sourc e Food Mode l o n foo d consumptio n patterns , lea d conten to fvariou s foods , an d source-specifi ccontribution s t o projec t1990-9 6 dietar ylea d intak e estimate s fo rdifferen tag e group s o fchildren
. Th e age-specifi cestimate s fro m Tabl e 5 o fCohe n (1988 ) show n below , as Tabl e A- l wil l b e incorporate d int o th e integrate d uptak e mode l t o predic t1990-9 6 Pb B level s amon g children
. Simila rdietar ylea d intak e estimate s wer e mad e fo r1978-8 3 fo rpurpose s o f validatin g th e uptake/biokineti cmode l (Se e Sectio n VI)
. Thes e ar e show n i n Tabl e A-2
. 10 . Gu tabsorptio n o fdietar ylead : Onl ya portio n o fingeste d lea d i s absorbe d int o th e bloodstrea m fro m th e gastrointestina l (GI ) tract , o rgut , an d i s dependen tupo n th e compositio n o fth e die tan d physiologica l statu s o fth e individual
. Base d o n measurements , mainl yamon g infants , o f lea d i n th e die tan d excreta , a gu tabsorptio n rat e fo ringeste d dietar y lea d betwee n 42-53 % ha s bee n calculate d (Alexande re tal. , 1973 ; Ziegle r e tal. , 1978)
. Correspondin g rate s betwee n 7 an d 15 % hav e bee n estimate d fro m adul tstudie s (Kehoe , 1961 ; Chamberlai n e tal. , 1978 ; Rabinowit z e tal. , 1980)
. Followin g th e approac h use d byHarle yan d Knei p (1985) , thes e rate s wer e assume d fo rinfant s an d adult s an d smoothe d t o yiel d value s fo rintermediat e ages , as follows :P.9 8 A- 5
TABLE A-l
. AGE-SPECIFI C ESTIMATE S O F TOTA LDIETAR

YLEA D INTAKE (pg/day ) FO R 1990-199 6
Ag e (years ) 

### < 1 

### 1 2 3 4 5 6 Metalli c



### 2. 6 3. 0 4. 0 4. 0 4. 0 4. 1 4. 2 Atmospheri c



### 0. 8 1. 1 1. 2 1. 2 1. 1 1. 2 1. 3 Othe r



### 3. 3 3. 8 3. 6 3. 7 3. 8 4. 0 4. 3 Tota l



### 6. 7 7. 9 8. 8 8. 9 8. 9 9. 3 9. 8
Source : Cohe n (1988 )

TABLE A-2
. TOTA

LDIETAR

YLEA D INTAKE (pg/day ) FO R 1978-198 3 FO

R FIV E AG

E GROUP S O F CHILDREN 3 

### Age(years ) 197 8 197 9 198 0 198 1 198 2 198 3 

### 1- 2 2- 3 3- 4 4- 5 5- 6 45. 8

52. 9 52. 7 52. 7 55. 6 41. 2

48. 0 47. 8 47. 8 50. 3 31. 4

36. 9 36. 9 36. 9 38. 7 28. 8

33. 8 33. 7 33. 8 35. 5 26. 0

30. 6 30. 6 30. 7 32. 2 19. 3

24. 1 23. 0 22. 0 23. 2

a Fro m Sledg e (1986 ) - - calculate d usin g year-specifi cFD Adat a o n foo d lea d conten tan d Multipl e Sourc e Food Modelin g methodolog ydescribe d i n Chapte r7 o fCD
. Assumes averag e drinkin g wate rlea d concentratio n a tth e ta p o f1 2 pg/1
. Used i n validatio n exercise s describe d i n Sectio n VI
.P.9 9
A- 6 Age : 0- 1 1- 2 2- 3 3- 4 4- 5 5- 6 6- 7 Averag e G I 42-5 3 42-5 3 30-4 0 30-4 0 30-4 0 30-4 0 18-2 4 . Absorptio n Rat e (%) : Thes e rate s d o no treflec tth e wid e degre e o finter-subjec tvariabilit y observe d i n th e studie s no rothe rfactor s tha tinfluenc e absorptio n i n children
. (Suc h variabilit ywil l b e accounte d fo ri n calculatin g populatio n distribution s o fPb B level s aroun d estimate d averag e Pb B level s usin y empirically-derive d geometri cstandar d deviations)
. Fo rexample , absorptio n rate s 2 t o 4 time s highe rwer e observe d i n adult s followin g fastin g period s o f4 t o 1 6 hour s (Blake , 1976 ; Chamberlai n e tal. , 1978 , Hear d an d Chamberlain , 1982 ; Rabinowit z e tal. , 1980)
. Suc h increase s ca n b e expecte d amon g childre n wh o ski p meals , a particula rproble m amon g lowe rincom e group s (Ko h an d Caples , 1977)
. Regula reatin g pattern s d o no tinsur e minimize d dietar ylea d absorption , however
. Base d o n severa l anima l studies , clinica l investigations , an d epidemiologica l surveys , childre n wit h diet s deficien ti n calcium , iron , phosphate , zinc , copper , vitami n D , protein , lipids , o rlactos e ca n b e expecte d t o absor b an d retai n lea d t o a greate rdegre e (CD , Tabl e 10-4)
. Thi s phenomeno n ma

ypartiall yexplai n th e enhance d neurotoxicit yo f lea d i n animal s wit h nutritiona l deficit s (Mahaffe yan d Michaelson , 1980)
. Th e importanc e o fnutritiona l interaction s wit h lea d absorptio n an d possibl y toxicit yi s particularl ysignifican tfo ryoun g childre n becaus e o fthei rlarg e fluxe s i n relativ e nutrien tstatus . Althouy h nutritiona l deficiencie s ar e mor e pronounce d amon g lowe rincom e children , the yexis ti n childre n o fal l socio-economi cstrat a (CD , p . 10-41)
. 1 1 . Dail ydietar ylea d uptak e i s obtaine d bymultiplyin g row s 1 0 an d 9 .P. 1 A- 7 12 . an d 13 . Dust/soi l concentrations : A s discusse d i n Sectio n II , th e accumulatio n o flea d i n stree tan d househol d dust s an d soil s appear s t o b e directl yrelate d t o th e volum e o ftraffic , an d inversel yrelate d t o distanc e fro m neighborhoo d street s an d roads , distanc e fro m lea d base d painte d an d bric k house s an d buildings , an d distanc e fro m lea d poin tsources . Predictin g a relationshi p betwee n differen tai rlea d level s an d dus tan d soi l lea d level s ove rtim e woul d requir e th e inclusio n o fman ycomple xvariable s suc h as depositio n rates , chemica l an d physica l characteristic s o fth e lea d particle s an d soils , topographi can d meteorologica l conditions , frequenc yo fstree t washing s an d precipitation , backgroun d dus tconcentrations , an d informatio n o n transpor to fdus tan d soi l int o home s an d buildings
. Give n curren tdata , ther e woul d b e a n extremel ylarg e amoun to funcertaint ysurroundin g an yon e o fthes e variable s fo rdifferen tlocations
. I n orde rt o predic toutdoo ran d indoo rdus tconcentration s unde ralternativ e ai rlea d concentrations , relianc e i s place d o n availabl e studie s tha tinclud e measurement s o fbot h ai rlevel s an d dus tand/o rsurfac e soi l concentration s (se e Tabl e A-3)
. Becaus e o fhistorica l accumulation s o frelativel ylarg e lea d particle s nea rprimar yan d secondar ylea d smelter s an d othe rpoin tsources , outdoo r soi l an d dus tlea d concentrations , an d consequentl ypotentia l exposures , ar e significantl ygreate ri n thes e areas , regardles s o fongoin g emissio n controls
. Thi s i s th e mai n reaso n wh yseparat e exposur e estimate s fo rindividual s livin g nea rpoin tsource s unde ralternativ e ai rlea d level s ar e required
. Dat a collecte d nea rlea d poin tsource s wher e anission s wer e comparabl e t o curren tsituation s ar e use d t o develo p outdoo rsoil/dus tlea d level s fo r poin tsource s meetin g differen tai rlea d concentration s (se e Appendi xB)
. Severa l o fth e studie s fo rwhic h dat a ar e no tuse d t o develo p relationship s requir e comment : a ) Barltro p e tal
. (1975 ) surveye d a rura l distric ti nP. 2 A- 8 TABL E A-3 . SUMMAR Y O F ENVIRONMENTA L LEAD MEASUREMENT S FRO MVARIOU S LOCATION S Averag e Ai r Lead (pg/m 3 ) Averag e Surfac e

Soil/Outdoo r Dus t Lead 3 (U9/9 ) Averag e Housedus t Lead (pg/g ) Location/Referenc e 0.2 0 0.4 0 0.2 9 0.6 1 0.2 8 0.3 4 1. 6 - 2. 0 1. 5 4 3

33 6 41 6 91 2 51 8 4,88 1 1,20 0 42 5 1 1 1 70 19 0

- 56 5 ,80 3 ,00 0

- Variou s Site s i n U.K
.

(DOE , 1983 ) Tw o Englis h town s (Barltro p e tal. , 1974 ) Derbyshire , U.K
. (lea d minin g area ) (Barltro p e tal. , 1975 ) Hartfor d (Lepowe tal. , 1975 ) Belo welevate d Londo n roadwa y (Barltro p an d Strehlow , 1976 ) 0.7 3 0.7 6 1.1 1 1.2 5 1.7 6 23 0

45 2 31 8 38 6 62 1 Throughou t Chicag o suburb s wit h majo r roadway s (Janse n e t al. , 1977 )

0.2 2 0.0 4 0.3 2 0.4 6
0.3 0 0.4 5 0. 8 3.6 7 8 0

9 1 59 1 26 0
11 4 11 2 46 6 2,56 0 21 5 162 28 0 47 0 "Post-control" 0 (1973-ly76 )

measurement s i n Omah a neighborhoods : suburba n mixe d (batter yplan ti n resi dentia l neighborhood ) commerc i a l (Angl e an

d Mclntire , 1979 ; Angle , 1985 ) "Post-control" 0 measurement s (1976 ) i n rura l area , Brussels , an d nea r lea d smelter , Belgiu m (Roel s e t al. , 1980 ) 0.4 1
0.8 2 3.0 1

- 2.0 C 69 0

24 0 92 4 2,41 6 1,21 4 69 8 25 3 (stree tdust ) (soil )

(<1. 6 km) (1. 6 - 3. 2 km ) (>3. 2 km ) 1,23 9

71 3 1,55 0 Nea rArnhei m secondar ylea d

smelter , Hollan d (Brunkree fe t al. , 1981 ; Dieme l e tal. , 1981 ) Nea rToront o secondar ylea d smelter s an d i n cit y(Robert s e tal. , 1974 ) Variou s distance s fro m a lead-zin c smelte ri n Britis h Columbi a (Schmit t e tal. , 1979 )P. 3

TABLE A
• Averag e Ai rLead (ug/m 3 )
0.1 3 0.2 0 0.3 0 0.3 1 0.1 4 0.1 8 0.0 9 0.2 6 0.0 9 0.1 1 0.1 9 0.2 6 0.3 6 0.5 6 0.1 3 0.2 8

1. 3 2.7 ° 0. 5 0. 5 0. 7 3. 0 6. 6 14. 2 16. 8 0. 3 0. 8 1. 9 2. 9 3. 6 - 3 . SUMMAR YO F Averag e Surfa c Soil/Outdoo r Dus tLead 3 (ug/g )
35 24 3 82 9 82 1 75 11 5 29 4 42 4 5 8 6 5 77 95 532 11 7 32 6 33 1

42 7 948^ 33 7 70 0 2,30 0 1,40 0 1,25 0 3,30 0 7,47 0 20 0 15 8 30 7 1,34 5 1,54 9 A- y 1 '

ENVIRONMENTA

LLEA D MEASUREMENT

S FRO M VARIOUS LOCATION S (Continued ) e Averag e Housedus t

Lead (ug/g )
24 1 40 9 38 6 44 1 23 5 164 21 0 39 8 7 5 6 0 6 5 11 6 26 3 20 1 19 8 43 8
1,47 9 8,623 d 1,80 0 3,90 0 3,40 0 3,30 0 2,40 0 10,30 0 11,70 0 50 1 39 8 89 1 1,58 5 2,28 4
a Surfac e soi l measurement s represen tto p 0 - 2. 5 cm . °"Post-control " control s a tth e control " refer s refer s t o th e p Location/Referenc e Distanc e rang e (km ) fro m zin co rcoppe rsmelter s in : (3. 5 - 24.0 ) (1. 3 - 3.7 ) Bartlesville , OK ; (0. 8 - 4.3 ) (0. 8 - 1.5 ) (10. 0 - 26.0 ) ( 3. 5 - 21.0 ) Anaconda , MT ; ( 2. 0 - 11.0 ) ( 2. 0 - 3.5 ) ( 3. 4 - 68.0 ) ( 1. 0 - 6.4 ) Ajo , AZ ; ( 0. 5 - 2.3 ) ( 0. 5 - . 1.3 ) (11. 0 - 26.0 ) ( 5. 4 - 14.5 ) Palmerton , P A ( 3. 3 - 9.9 ) ( 0. 3 - 2.8 ) (Hartwel l e tal. , 1983 ) Nea rE l Pas o primar ylea d smelte r "Post-control" 0 "Pre-control " (Landriga n e tal. , 1975 ; Mors e e tal. , 1979 ) Nea rSilve rValley , Idaho , primar ylea d smelter ; Pre-control ° (Yanke l e t al. , 1977 ; Idah o Dept
. Healt h an d Welfare , 1977 )

Nea rE
. Helen a primar ylea d smelte r (CDC , 1983 )

erio d o ftim e followin g th e applicatio n o rincreas e i n emissio n lea d poin tsource(s ) involve d i n th e t o th e perio d c Annua l mean concentratio n rep o dfior-Mnot - r- i r

annua l moa n nf ai r1 o ftim e befor e th e app ' rte d as a n approximat e oar ) 1 owo l c moacuroi i w i particula rstudy
. Conversely , "pre icatio n o rincreas e i n emissio n controls
. valu e L h i n £*

k m nf cmolto r e Geometri cmean o fdus tan d soi l lea d level s withi n 6. 4 k m o fsmelte rP. 4 A-1 0 Englan d wit h minima l ai rpollution , bu twit h hig h natura l soi l lea d level s a s wel l a s bein g contaminate d bynearl y190 0 year s o fminin g activity
. Thus , lea d depositio n o n soi l surface s had probabl ybee n lo wfo rsom e time , i n contras tt o th e othe rstudie s i n whic h surfac e contaminatio n wa s ongoin g o r had bee n recentl yreduced ; b ) Eigh to fth e te n home s sample d byLepo

we tal
. (1975 ) wer e buil tprio rt o 194 0 an d apparentl yhad significan tsource s o f leade d pain ttha thad bee n "corrected " fo rpreviou s t o th e study
. I n addition , som e o fth e home

s wer e locate d clos e t o heavil ytrafficke d roadways , wher e stree tleve l ai rconcentration s range d betwee n 2. 2 an d 7. 7 pg/m 3 , thu s lendin g uncertaint yt o a dust/ai rrelationshi p fro m thi s stud ybase d o n annua l averag e ai rlea d level s measure d a tcentrall ylocate d monitor s distan tfro m th e dus tsamplin g sites ; c ) Th e smelte rstudie d byYanke l e t al
. (1977 ) operate d fo rsevera l year s wit h severel ylimite d ai rpollutio n contro l capacit ydu e t o a baghous e fir e i n 1973 . Th e ver yhig h soi l an d dus tlea d concentration s measure d nea rth e smelte rwoul d no tb e expecte d toda ywit h normall ycontrolle d emissions ; d ) Th e hig h indoo rdus tlea d level s measure d byBrunekree fe tal
. (1981 ) an d Dieme l e tal
. (1981 ) nea rth e Belgia n smelte r wer e probabl ydue , i n part , t o extremel yhig h lea d conten t(u p t o 40% by weight ) i n peelin g pain ti n ol d house s (buil t aroun d 1900 ; th e childre n i n thes e house s wer e exclude d fro m analysi s o fbloo d lea d levels) ; e ) Th e relativel yhig h soi l an d dus tlea d level s i n relatio n t o concurren tai rlea d concentratio n measure d nea rth e Bartlesvill e smelte rbyHartwel l e tal
. (1983 ) wa s probabl ydu e t o a drasti creductio n o ftota l suspende d particulat e emissions , fro m 160 0 tons/yea rt o 1 5 tons/year , jus tprio rt o th e onse to fth e study
. Wit h thes e exceptions , th e studie s liste d i n Tabl e A- 3 appea rt o hav e sample d a broa d spectru m o fhome s (e.g. , bot h lo wan d middl e class , ol d an d modern , wit h an d withou tleade d paint--thos e wit h hig h pain tlea d level s wer eP. 5 A-l l excluded ) an d neighborhood s tha tca n b e considere d fairl yrepresentativ e o f curren tU.S
. condition s i n urba n an d poin tsourc e areas . Althoug h fa rfro m conclusive , th e availabl e dat a fro m poin tsourc e studie s sugges tth e long-ter m equilibriu m relationship s betwee n ai rlea d an d soil/dus tlea d concentration s show n i n Tabl e A-4
. Appendi xB contain s a descriptio n o fth e derivatio n o f thes e equations
. Short-ter m (severa l months ) departure s fro m lon g ru n equilibriu m level s o fsoi l an d dus tlea d (fro m impositio n o fne walternativ e lea d NAAQS , fo rexample ) ar e als o estimate d i n Appendi xB
. Th e short-ter m relationship s ar e show n i n Tabl e A-5
. I n general , a chang e i n ambien tlea d wil l i n th e shor tterm , onl yinduc e direc tchange s i n dus tlead
. I n th e lon g term , th e relationship s i n Tabl e A- 4 ar e appropriate
. Unfortunately , insufficien t longitudina l dat a exist s t o explicitl yestimat e th e tempora l relationshi p betwee n ambient , soil , an d dus tlead
. 14 . I ti s estimate d tha ta youn g chil d typicall ysleep s abou t1 2 hour s a day(Pope , 1986b) , leavin g approximatel y1 2 wakin g hour s i n whic h h e o rsh e i s capabl e o fingestin g dirt
. Th e tim e weighte d concentratio n o flea d i n dus tan d soi l tha ta chil d i s expose d t o i s thu s compute d by : [(outdoo r soil/dus tlea d concentratio n xtim e spen toutdoors ) + (indoo rdus tlea d concentratio n xtim e spen tindoors) ] * 1 2 hours
. 15 . Amoun to fdir tingested : Han d t o mout h activit y(e.g. , thum b suckin g an d finge rlicking ) an d immatur e dietar yhabit s (i.e. , th e retrieva l an d subsequen tconsumptio n o ffoo d fro m dust ysurface s o rsoil) , whic h ar e norma l behavoria l characteristic s o fchildre n u p t o fiv e year s o fag e (Lin-Fu , 1972) , mak e soi l an d dus tmajo rsource s o fingeste d lea d fo r childre n (Charne ye tal. , 1983)
. Goo d informatio n o n th e amoun to fdir t aP. 6 A-1 2

Tabl e A-4
. LONG-TER M RELATIONSHIPS BETWEE N DUST , SOI LANU AMBIEN TLEA U

Soi l Lea d = 50. 1 + 579. 0 (Ambien tLead ) Dus tLead = 57. 6 + 972. 0 (Ambien tLead )

Tabl e A-5
. ESTIMATIN G SHORT-TERM 1 RESPONSE S I N EQUILIBRIU M SOI LAN D OUS T LEA D LEVEL S FRO M CHANGE

S I N AMBIEN

TLEA D Chang e i n Dus tLea d = 582. 0 (Chang e i n Ambien tLead ) Chang e i n Soi l Lea d = N o Chang e

1 Duratio n o fsevera l month s o rless
.P. 7 A-1 3 chil d eat s i n th e norma l cours e o fa da yi s neede d for.a n assessmen to f healt h risk s associate d wit h toxi cmaterial s i n th e environment
. Base d o n a smal l numbe ro fdirec tmeasurements , Da ye tal
. (1975 ) estimate d tha t unde raverag e urba n condition s (an d afte r3 0 minute s o fnorma l playgroun d activity) , 5 t o 50 m g o fdir ttransferre d fro m a child' s hand s t o a typica l "stick ysweet" , an d estimate d tha ta dail yintak e o f2-2 0 sweet s woul d resul t i n a dir tintak e o f10-100 0 mg . Lepo we tal. , (1974 ) measure d a mean o f 1 0 p g o fdir to n th e hand s o f2 2 youn g childre n whic h woul d b e ingeste d wit h eac h episod e o fhand-to-mout h activity
. Thes e author s estimate d tha ta chil d put s it s han d int o it s mout h te n time s pe rdaywhic h woul d resul ti n th e ingestio n o f10 0 m g (0. 1 g ) o fdus tan d soi l pe rday
. A n averag e estimat e o f10 0 m

g o fdir tingeste d dail ybyyoun g childre n ha s bee n use d i n severa l document s (Dril l e tal. , 1979 ; NAS , 1980 ; CD , Tabl e 7-23 ) t o represen ta probabl e valu e fo ra "typical " child
. Recently , Binde re tal
. (1986 ) an d Clausin g e tal
. (1987)
. estimate d children' s intak e o fsoi l bymeasurin g relativel ynon-absorbe d element s wit h hig h concentration s i n soi l as tracers . Level s o faluminum , titanium , an d eithe rsilico n o raci d insolubl e residu e wer e determine d i n soi l an d children' s fece s an d mass balanc e calculation s wer e mad e t o estimat e soi l ingestion
. I n bot h studies , soi l ingestio n estimate s base d o n titaniu m wer e highl yvariabl e an d i n man ycases , a n orde ro fmagnitud e greate rtha n result s usin g th e othe rtracers . Thi s suggest s a n additiona l sourc e o f titaniu m no taccounte d fo ri n th e studie s (e.g. , paint , toothpaste , talc , laborator ycontamination ) an d tha tth e titanium-based , outlyin g estimat e shoul d b e give n les s weight
. Fo r5 9 children , age s 1 throug h 3 years , Binde re tal
. estimate d mean dail ysoi l ingestio n base d o n aluminu m an d silico n t o b e 18 1 an d 184P. 8 A-1 4 mg/da yrespectively ; geometri cmean s fo rth e tw o element s wer e 12 8 an d 13 0 mg/day
. Th e mean estimat e base d o n titaniu m wa s 183 4 mg/day
. Ofth e variou s factor s an d assumption s use d i n thi s stud ytha tcoul d hav e contribute d t o a n inaccurat e estimat e o fsoi l ingestio n (e.g. , assumptio n tha tth e trace r elemen tabsorptio n i s negligible , an d tha t ther e i s introductio n o rlos s o ftrace relemen tdurin g processing) , th e assumptio n wit h th e mos tsignifican t potentia l impac ti s tha tdietar yintak e o fth e trace relement s i s negligible
. Binde re tal
. an d Sedman (1987 ) cit e evidenc e tha tthes e element s d o i n fac t occu ri n th e diet
. Th e stud ydesig n use d byClausin g e t al
. provide s a n indirec tcontro l fo rsuc h dietar yintake ; 1 8 nurser yschoo l childre n an d 6 hospitalize d children , withou tsoi l contact , age s 2-4 , wer e sampled
. Th e averag e o festimate d soi l ingestion s base d o n al l 3 tracer s wa s 10 5 mg/da y fo rth e nurser yschoo l childre n an d 4 9 mg/da yfo rhospitalize d childre n whic h was . significantl ydifferen tdespit e th e smal l numbe ro fsamples
. I fa s th e author s assumed , al l o fth e "soi l ingestion " byhospitalize d childre n i s backgroun d du e t o dietar yan d othe rnon-soi l sources , correctio n o fth e nurser yschoo l averag e fo rthi s backgroun d woul d resul ti n a n estimate d averag e soi l ingestio n rat e o f5 6 mg/day
. I fth e sam e backgroun d i s subtracte d fro m th e Binde re tal
. estimate s t o adjus tfo rdietar ysource s o f trace relements , soi l ingestio n rate s o fapproximatel y80-13 5 mg/da yresult
. Fo rchildre n i n th e 1- 4 yea rol d ag e grou p studie d byBinde ran d Clausing , a rang e o fsoi l ingestio n betwee n 8 0 an d 13 5 mg/da ywil l b e assumed
. A s note d byBinder , Clausing , Sedman,
. an d colleagues , considerabl e uncertaint ysurroun d thes e estimate s give n fo rexample , th e smal l numbe r o fsubject s studie d an d th e lac k o fcomplet e dat a o n dietar yintake s an d gu tabsorption
. Nevertheless , th e rang e o fth e estimate s i s narro wdespit e bein g derive d fro m separat e dat a set s an d doe s sugges ttha tthe yreasonabl yP. 9 A-1 5 reflec taverag e soi l ingestio n fo rthi s ag e group . Give n tha tchildre n ea ta combinatio n o fsoi l an d dust , an d tha tth e studie s di d no tdistinguis h betwee n thos e tw o media , th e estimate s woul d b e inaccurat e i fconcentration s o fsilico n an d aluminu m wer e differen ti n hous e dus tan d soil
. Unti l furthe r dat a ar e available , i twil l b e assume d tha tsoi l ingestio n estimate s fro m thes e studie s reflec ttota l "dirt " consumptio n rates . I n orde rt o us e th e abov e estimate s t o determin e dir tingestio n rate s fo rothe rage s o fchildren , dat a o n age-relate d change s i n bloo d lea d (Yanke l e tal. , 1977 ; Annes tan d Mahaffey , 1984 ; Billick , 1982 ; Quah e tal. , 1982 ) an d th e prevalenc e o fmouthin g behavio r(M i H i ca n e tal. , 1962 ; Barltrop , 1966 ) wer e use d bySedman (1987)
. Relativ e age-relate d change s i n soi l ingestio n calculate d bySedman wer e applie d t o th e rang e derive d abov e fo rth e 1- 4 yea rol d age-grou p t o yiel d th e followin g estimates : Ag e (years ) 0- 1 1- 2 2- 3 3- 4 4- 5 5- 6 6- 7 Dir tIngestio n 0-8 6 80-13 5 80-13 5 80-13 5 70-10 0 60-9 0 55-8 5 (mg/day ) Th e lowe rboun d o fzer o fo rth e younges tag e grou p wa s chose n becaus e contac t wit h dirt ysurface s i s limite d fo rth e firs t6 month s o rs o unti l crawlin g begins
. I n informa l discussion s wit h clinician s an d othe rresearchers , includin g thos e wh o ar e involve d i n ongoin g studie s o fsoi l ingestio n i n children , ther e wa

s genera l agreemen ttha tthes e estimate d range s ar e reasonabl e average s give n th e availabl e dat a an d associate d uncertainties
. Furthe rresearc h o n thi s issu e tha tinclude s specifi cexaminatio n o ftrace r elemen tmetabolis m an d dietar yintake , an d hous e dus tingestion , ha s bee n stimulate d byth e Binde ran d Clausin g studies
. Preliminar yresult s fro m thi s ongoin g researc h tha tca n hopefull yclarif yth e estimate s presente d her e ar e expecte d sometim e i n earl y1990 .P.1 0 A-1 6 Th e abov e range s representin g averag e exposur e estimate s ar e derive d fro m studie s tha tdi d no tinclud e childre n wit h pica
. Dir t ingestio n rate s fo rman ychildre n ca n b e much higher
. Fo rexample , amon g youn g childre n hospitalize d fo rasymptomati clea d poisonin g an d expose d t o thre e pla y environment s whic h differe d i n thei rstimulu s complexit y(e.g. , numbe ran d typ e o ftoys , availabilit yo fplaymate) , significantl ymor e mouthin g behavio r occurre d i n th e impoverishe d pla ysettin g (Madde n e tal. , 1980)
. I n particular , childre n wit h pic a wh o displa ypattern s o frepetitiv e hand-to-mout h activity , o rwh o deliberatel yinges tpaint , plaster , pape ran d othe rnon-foo d item s includin g dirt , ma yb e expose d t o considerabl e amount s o flea d compare d t o childre n wh o onl yinadvertantl yinges tforeig n substances
. Pic a occur s t o som e degre e i n a substantia l percentag e o fyoun g children
. Dat a fro m NHANE S II.indicat e tha tth e percen to fchildre n wit h a histor yo fpic a i s significantl yhighe rfo rthos e 6 month s throug h 3 year s ol d (11.0% ) tha n fo rthos e 4 throug h 5 year s ol d (3.2% ) an d fo rchildre n livin g i n household s wit h annua l famil yincome s < $10,00 0 (11.9% ) tha n fo rthos e i n household s wit h income s > $10,00 0 (6.0% ) (Mahaffe yan d Annest , 1985)
. Estimate s fo r pic a prevalenc e rates , base d o n mor e limite d samples , rang e as hig h as approximatel y1 0 t o 30% i n childre n 1 t o b year s ol d t o 35-50 % i n thos e 1 t o 3 year s ol d (Millica n e tal. , 1962 ; Barltrop , 1966)
. Childre n exhibitin g pic a fo rpain tar e o fmajo rconcer n becaus e o fth e hig h level s o flea d i n som e paints , wit h olde rpainte d surface s containin g lea d i n concentration s greate rtha n 1 percen t(10,00 0 ppm)
. [Th e allowabl e lea d conten to fpain t wa s se ti n 197 8 byth e Consume rProduc tSafet yCommissio n a t0.0 6 percen t lea d (60 0 ppm)]
. Pic a fo rpain ti s believe d t o occu ri n episodes , possibl y 2 t o 3 time s pe rwee k (NAS , 1972)
. I tha s bee n estimate d tha ta chil d ca n consum e somewha

tgreate rtha n 1 gra m withi n a 2 4 t o 3 6 hou rperiod , wit hP.1 1 A-1 7
case s reporte d o fu p t o 2 0 gram s withi n th e sam e tim e perio d (Sachs , 1976 ) an d tha tchildre n wit h pic a fo rpain tma yconsum e 1 t o 3 gram s pe rwee k (NAS , 1972)
. Althoug h direc tdat a o n pic a childre n ar e no tye tavailable , a reasonabl e "wors tcase " estimat e o f1 gram/da yfo rsoi l ingestio n i n youn g childre n ha s bee n suggeste d (White , 1987)
. Estimate s o fdail ylea d uptak e unde ralternativ e ai rlea d level s ar e presente d i n Tabl e 4- 1 onl yfo rchildre n withou tpica
. I n orde rt o calculat e th e contributio n o flea d i n pain tt o th e tota l lea d exposur e o fchildre n wit h pica , a worst-cas e estimat e o f1 gra m o fpain tchip s consume d pe rda y coul d b e used
. Futur e reduction s i n airborn e lea d emission s ar e no tlikel y t o significantl yalte rpic a exposur e t o lea d ove rth e nex tfe wyear s an d othe rregulator yalternative s t o protec tthes e childre n mus tb e considered
. 16 . Lead intak e fro m dus tan d soi l i s compute d b ymultiplyin g th e tim e weighte d concentratio n o findoo ran d outdoo rsoil/dus tconcentration s byth e estimate d dir tingestio n rate s liste d above
. 17 . Gu tabsorptio n o fdirt : Anima l experiment s indicat e tha tlea d o fvariabl e chanica l form s i n soi l o rdus ti s as availabl e fo rabsorptio n as foo d lea d (Dacr e an d Te rHaar , 1977 ) an d i n vitr o studie s demonstrat e tha tth e acidit yo fth e human stomac h i s adequat e t o extensivel ysolubiliz e lea d assimilate d fro m soi l an d dus t(Daye tal. , 1979 ; Harrison , 1979 ; Dugga n an d Williams , 1977)
. Base d o n thes e dat a an d th e fac ttha tingestio n o fsuc h material s occur s othe rtha n a tmealtimes , allowin g fo rpotentiall yenhance d absorption , th e C

D estimate s tha t30 % o fth e lea d ingeste d i n dus tan d soi l i s absorbe d i n a chil d (CD , p . 10-10)
. A s discusse d i n th e CD , th e relationshi p betwee n bloo d lea d an d lea d intak e i s curvilinea racros s a broa d rang e o fbloo d lea d value s suc h tha t th e relativ e chang e i n bloo d lea d become s smalle ras "baseline " bloo d lea d o rP.1 2 A-1 8 lea d intak e increase s (CD , p . 10-53 , sectio n 11.4.3)
. I n th e lowe r"rang e o fexposures , ther e i s n o significan tdifferenc e betwee n curvilinea ran d linea r relationship s (CD , p . 11-99 , p . 11-134)
. Anumbe ro fbiologica l factor s ma y explai n th e curvilinea rrelationship s suc h as a n increasin g fractio n o fbloo d lea d as circulatin g lea d rises , wit h greate rmovemen to fplasm a lea d t o tissues , includin g bone , an d increase d lea d excretion
. Anothe rplausibl e basi s i s gradua l saturatio n o flea d transpor tprotein s i n th e G I trac tas lea d intak e rise s (CD , p . 10-13)
. I n fact , improve d fit s o fth e uptake / biokineti c mode l estimate s t o measure d bloo d lea d dat a fro m E
. Helen a resulte d whe n G I absorptio n rate s i n childre n wer e differentiate d base d o n proximit y t o th e smelte rwhic h i s a surrogat e fo rlea d intak e level
. Th e bes tfit s resulte d whe n a G I absorptio n rat e o f0.3 , equivalen tt o th e averag e rat e cite d i n th e C

D fo rchildren , wa

s assume d fo rchildre n livin g beyon d a one mil e radiu s fro m th e smelter , an d a rat e o f0. 2 wa s assume d fo rchildre n livin g withi n on e mile
. Aclos e fi tbetwee n observe d an d predicte d bloo d lea d level s als o resulte d whe n a n averag e rat e o f25% was use d fo rth e entir e are a (withi n 2.2 5 miles ) o fth e smelter
. I ti s o finteres tt o not e tha ta G I absorptio n facto ro f0.1 7 ha s bee n estimate d fo rpain t chi p ingestio n i n childre n (CD , p . 10-10)
. Fo rchildre n abov e 6 year s old , a slightl ylowe rvalu e i s neede d t o reflec tth e fac ttha tG I absorptio n efficienc ygenerall yi s much lowe ri n adults
. Fo rchildre n age s 6- 7 year s o fage , a G I facto ro f0.1 5 an d 0. 2 wil l b e assume d depending , as discusse d abov e fo ryounge rchildren , o n thei rproximit yt o a lea d poin tsource . An invers e relationshi p wa s foun d betwee n particl e siz e an d gastro intestina l absorptio n o flead , especiall yi n th e rang e o f1-10 0 pm , suc h tha ta 6 p

m dietar ylea d particl e wa s absorbe d fiv e time s a s efficientl y as a 197 p

m particl e (Barltro p an d Meek , 1975)
. Ther e i s littl e informatio nP.1 3 A-1 9 t o asses s whethe rth e conversio n i n th e physica l for m o fatmospheri clead containin g particle s onc e insid e th e comple xgeochemica l matri xo fsoi l o r a s dus twoul d affec tthei rbioavailabilit yand , consequently , toxicity
. Thus , atmospheri clea d particle s tha thav e deposite d wil l b e considere d t o hav e absorptio n rate s i fingested , independen t o fparticl e size
. 18 . Tota l lea d uptak e fro m dus tan d soi l i s obtaine d bymultiplyin g row s 1 6 an d 17 . 19 . Tota l lea d uptak e i s th e su m o frow s 8 , 11 , an d 18 . Pain tLea d Exposur e Estimate s No attemp tha s bee n mad e t o separat e lea d pain thazard s fro m generalize d condition s i n estimatin g soi l an d dus tlea d concentration s associate d wit h differen tai rlea d levels
. Th e majo rreason s ar e tha t1 ) an ychange s i n th e lea d NAAQ

S wil l hav e minima l effect s o n childre n expose d t o dust s an d soil s contaminate d byth e flaking , peeling , weatherin g o r"powdering " o f lead-base d pain tan d 2 ) dat a ar e no tavailabl e t o adequatel yestimat e lea d concentration s resultin g fro m lea d pain tcontaminatio n give n thei rhig h variabilit ydependin g o n man yfactor s includin g housin g age , exten t o f deterioration , layer s o fpaint , famil ybehaviors , an d climate
. Fo rpurpose s o fsimpl yillustratin g th e magnitud e o frisk s associate d wit h lead-pain t hazard s i n relatio n t o generalize d exposure s aroun d poin tsource s o ri n othe rareas , on e se to faverag e estimate s o flea d level s i n dust s an d soil s i n an d aroun d home s wit h lea d paint , presente d i n th e CD , ca n b e used
. Base d o n studie s o fHard ye tal
. (1971 ) an d Te rHaa ran d Arono w(1974) , th e C D state s tha tsoi l lea d an d househol d dus tlea d concentration s aroun d an d i n lead-painte d home s ca n b e expecte d t o averag e 200 0 ppm (p
. 7-62)
. I fthi s soi l an d dus tlea d leve l i s entere d int o th e exposur e profil e fo r childre n i n Tabl e 4-1 , assumin g a n ai rlea d leve l o f0. 5 pg/m 3 , fo rexample ,P.1 4 A-2 0
an d a gu tabsorptio n rat e o f0.1 7 cite d i n th e C D fo rpain tchip s (CD , p . 10-10) , range s o ftota l lea d uptak e woul d increas e fro m 11.5-26. 7 pg/da y t o 31.2-51. 1 pg/day
. Eve n thi s larg e differenc e markedl yunderestimate s leade d pain texposur e fo rman ychildre n sinc e childre n wh o ea tflakin g pain to rgna

wlead-painte d woodwor k ar e no taccounte d for
. Assumin g pic a behavio r( 1 gram/da yingeste d rate , se e #1 5 above ) i n lead-painte d housin g condition s wit h soi l an d dus tlea d level s o f200 0 ppm , th e dail ylea d uptak e estimate s cite d abov e increas e t o approximatel y35 0 pg/day
.P.1 5



### APPENDI XB . ESTIMATIO NO F TH E RELATIONSHIP S BETWEE NSOIL , DUS T AN D AMBIEN T LEAD Ake yassumptio n i n regulatio n o fatmospheri clea d concentration s (PbA) i s tha tchange s i n Pb Awil l b e followe d bycorrespondin g change s i n soi l lea d concentratio n (PbS ) an d interio rhous e dus tlea d concentratio n (PbD ) i n th e sam e vicinity
. Sinc e ingestio n o fsoi l an d dus tlea d durin g norma l hand-mout h activit yi s believe d t o b e th e majo rsourc e o flea d uptak e i n ver yyoun g childre n (an d wors e whe n pic a i s present ) i t i s importan tt o mak

e a quantitativ e estimat e o fth e magnitud e o fth e effect s o n thes e proximat e cause s o fchildhoo d lea d exposur e du e t o change s i n PbA
. 1 . Mathematica l Model s fo rSoi l an d Dus tLea d vs . Ai rLea d Th e relationship s depen d o n man yfactors , includin g tim e (t ) an d physica l o rchemica l propertie s o fth e atmospheri clea d particulate s suc h as particl e siz e an d surfac e wate rsolubilit yo fth e particulat e lea d matrix
. W

e le txdenot e a generi cse to fparticl e properties
. Th e fractio n o fairborn e particle s deposite d o n soil , pe rday , denote d DF(x,t) , i s i n genera l a functio n o fxan d t . S o i s th e fractiona l rat e o fremova l o fsurfac e soi l lead , denote d RF(x,t) , byburial , runoff , resuspension , cleanin g an d othe ractivities , an d th e influ xrat e (pg/ g pe rda ysurfac e Pb S fro m non-ai rsources ) denote d IF(x,t)
. Finally , i n orde rt o calculat e th e P b concentratio n i n th e atmospheri cparticulates , w e als o nee d th e atmospheri cparticulat e matte rconcentratio n i n particl e clas s xa ttim e t , denote d PM(x,t)
. Aforma l mode l fo rcombinin g thes e quantitie s i s describe d next . Aplausibl e mathematica l mode l fo rth e rat e o fchang e o fPbS(x,t ) ca n b e expresse d bya differentia l equatio n Rat e o fchang e = non-ai rinflu x+ atmospheri cdepositio n - soi l remova lP.1 6
B- 2 or , symbolically , dPbS(x,t)/d t= IF(x.t ) + [PbA(x,t)/PM(x,t) ] DF(x,t )

- PbS(x,t ) RF(x,t ) (Equatio n 1.1 ) An equilibriu m mode l ma yb e obtaine d bysettin g dPbS/d t= 0 an d solvin g th e resultin g equatio n (suppressin g dependenc e o n t) , PbS(x ) = AQ(X ) + Ai(x ) PbA(x ) (Equatio n 1.2 ) wher e A 0 (x ) = IF(x ) / RF(x ) (Equatio n 1.3 ) Ai(x ) = DF(x ) /

[RF(x ) PM(x) ] (Equatio n 1.4 ) Not e tha tthi s implie s tha twhe n ther e i s mor e unleade d dus ti n th e ai r (large rPM(x)) , the n th e soi l lea d vs . ai rlea d slop e A ^ i s lower
. Likewise , a non-equilibriu m mode l ca n b e derive d fro m equatio n 1.1 . I n th e cas e whe n al l o fth e parameter s ar e independen to ftime , w e hav e a relativel ysimpl e solutio n i n term s o fa n exponentia l approac h t o th e equilibriu m concentratio n PbS(x ) i n Equatio n 1.2 , PbS(x.t ) = PbS(x,0 ) exp(-RF(x)t ) + 

### ( 1 - exp(-RF(x)t ) PbS(x ) (Equatio n 1.5 ) I n th e cas e wher e th e parameter s ca n verywit htime , th e exponentia l solutio n i s muc hmor e complicated , PbS(x,t ) = PbS(x,0 ) ex p [ - 6 RF(x,U ) du ] + h [IF(x,u ) + PbA(x,u ) DF(x,u ) / PM(x,u) ] ex p ( - 6 RF(x,v ) dv ) d u (Equatio n 1.6 ) Ther e ma

yb e substantia l variatio n i n th e apparen tsoi l lead-ai rlea d "slope " wher e Pb

S nas no thad sufficien ttim e t o reac h near-equilibrium , sayt< 3/RF(x)
. Thu s th e soi l lea d remova l tim e scal e l/RF(x ) i s a critica l parameter .P.1 7 B- 3 Anothe rconsequenc e o fthi s mode l i s tha tparticl e propertie s (x ) ma yb e a facto ri n producin g a n apparentl ynonlinea rrelationshi p betwee n tota l soi l lea d concentratio n Pb S Pb S = E xPbS(x ) an d tota l ai rlea d concentratio n Pb A Pb A= Z xPbA(x)
. Fro m equatio n 1.2 , th e equilibriu m relatio n i s Pb S = £ xAQ(X ) + Z xAi(x ) PbA(x ) (Equatio n 1.7 ) Thi s produce s a n exactl ylinea rrelationshi p Pb S = a y+ a xPb A(Equatio n 1.8 ) whe n Ai(x ) = DF(x ) / [RF(x ) PM(x) J = a i (Equatio n 1.9 ) a 0 = E x IF(x ) /

RF(x ) Th e assumptio n tha tAi(x ) i s a constan ta teac h site , i.e. , doe s no tdepen d o n particl e propertie s x , i s plausibl e bu tuntested
. Empirically , th e relationshi p betwee n Pb S an d Pb

Ai s nearl ylinea ra tlo wlevel s o fPbA , bu tma yb e somewhatnonlinea ra thighe rPb A(McLamb , 1988 ; Marcu s 1988b ) I ti s mor e plausibl e tha tPbS(x ) i s linea rwit h th e averag e concentratio n o flea d i n th e particles , as i n Equatio n 1. 4 s o tha ta linea rrelatio n betwee n Pb

S an d Pb

Ais , a tbest , a n approximation , unles s al l particle s ar e i n a singl e xclass
. Simila rbu tmor e comple xcalculation s ma yb e use d t o deriv e a linea r Pb D vs . Pb

Arelationship
. 2 . Revie wo fDat a i n Th e Literatur e Anumbe ro fdat a set s wer e examine d tha tcoul d b e use d t o asses s th e rat e a twhic h soi l lea d (PbS ) and/o rhous e dus tlea d (PbD ) concentration s chang e ove rtim e a s a consequenc e o fchange s i n ai rlea d concentratio n (PbA)
.P.1 8 B- 4 Mos to fth e reporte d studie s ar e o fmargina l value
. W e wil l firs t describ e th e dat a set s w

e foun d les s useful
. Th e Omah

a studie s byAngl e e tal
. (1984 ) contai n usefu l annua l data , bu tth e spatia l an d tempora l averagin g i s a ta ver ybroa d scal e an d much detai l i s lost
. Th e lea d dustfal l dat a (PbDF , mg/cm^) wa s availabl e fo rmos to fth e year s i n whic h Pb Aaverage s ar e given , bu tPb D an d Pb

S wer e onl ymeasure d a t37 location s i n 1972 . Th e dat a ar e show n i n Tabl e B-l
. N o relatio n betwee n PbDF an d Pb Ai s evident
. Th e Roel s e tal
. (1978 , 1980 ) dat a als o measure d Pb Afo ra numbe ro f years , bu tPb

D onl yfo r1976 , s o i s no tusefu l fo rshowin g Pb D changes
. Th e E l Pas o smelte rdat a (Mors e e tal. , 1979 ; Landriga n e tal. , 1975 ; Landriga n an d Baker , 1981 ) measure d PbA , PbD , an d Pb S a tsevera l location s i n 197 2 an d 1977 . I n 197 2 man yo fth e mos theavil ylead-burdene d childre n live d i n th e Smeltertow n neighborhoo d adjacen tt o th e smelter
. B y197 7 almos tal l childre n ha d bee n evacuate d t o safe rneighborhoods
. I n th e intervenin g fiv e year s th e mean annua l ai rlea d level s (PbA ) had decline d fro m 10. 0 t o 5. 5 pg/m 3 a t0. 4 k m fro m th e smelter
. Th e dus t sample s i n 197 2 wer e collecte d i n Smeltertow n an d othe rlocations , wit h exceptionall yhig h geometri cmean Pb D valu e o f22,19 1 ppm i n th e rin g 0 t o 1. 6 k

m fro m th e smelter
. Th e 197 7 mea n Pb D was onl y1,47 9 ppm i n thi s ring , an d 1,46 1 pp

m i n th e rin g 0. 8 t o 1. 6 k m fro m th e smelter
. Likewise , th e 197 2 soi l lea d mean wa s 1,79 1 ppm i n th e 0 - 1. 6 k m ring , an d 42 7 ppm i n 1977 . Th e declin e i n E l Pas o Pb S an d Pb

D i s proportionatel ymuch greate r fro m 197 2 t o 197 7 tha n th e declin e i n PbA
. Severa l factor s ma ypla ya rol e here
. Th e firs ti s tha tth e extensiv e publicit ygive n t o lea d as a healt h hazar d probabl ycause d much mor e extensiv e individua l attentio n t oP.1 9 

### B- 5
TABL E B- l ENVIRONMENTA

L LEA D CONCENTRATION S I

N OMAHA , NEBRASK

A(ANGL E E T AL. , 1984 )

Are a Yea r Pb APbDF Pb D Pb S 197 0 197 2 197 3 197 4 197 6 197 7 197 0 197 2 197 3 197 4 197 6 197 7 197 0 197 2 197 3 197 4 197 6 197 7 1.6 6

0.3 7 0.4 6 0.0 4 0.1 3 0.7 8 1.4 4 0.3 2 0.3 2

- 0.1 6 0.6 2 0.7 3 U.2 6 0.2 2 0.0 4

-

- -

- 

### 2 6 1 7 

### 5 3 4

_

- 

### 1 1 

### 6 1 8

_

- 

### 7 3

-

- 47 9 26 2

30 0 33 9

21 1 8 1P.2 0 B- 6 househol d cleanlines s an d t o contro l o farea s i n whic h childre n coul d b e expose d t o leade d soi l (Landrigan , persona l communication , Apri l 5 , 1988)
. Secondly , w

e d o no tkno

wi fth e sam e location s wer e sample d i n 197 2 an d 1977 . Interio rhousehol d dus tcollectio n woul d hav e bee n negligibl e i n Smeltertow n i n 197 7 as onl ythre e childre n live d there
. Finally , th e ai r lea d level s relevan tt o th e highes tPb D i n 197 2 ma

yhav e bee n much large r tha n 10. 0 pg/rn 3 i n 1972 . Landriga n e tal
. (1975 ) reporte d a mean Pb Ao f9 2 pg/m 3 a tth e ai rmonito rcloses tt o th e smelter
. APb D delin e fro m 22,19 1 t o 1,47 9 ppm (15-fold ) i s bette rexplaine d bya Pb Adeclin e fro m 92 t o 5. 5 pg/m 3 (17-fold)
. Acces s t o unpublishe d dat a ma yclarif ythis
. Th e NE Asourc e apportionmen tstud y(Coope re tal. , 1981 ) obtaine d a numbe ro flow-vol , high-vol , an d dichotomou s sample rTS P sample s a t location s i n th e vicinit yo fth e Kellogg , Idaho , smelte rdurin g 1980 , whe n th e smelte rwa s stil l i n operation
. Sample s wer e als o obtaine d o f "aerosolizabl e dust. " Thes e dat a ar e no tdirectl ycomparabl e t o Pb S values
. Th e sample s o fsoi l an d roa d dus twer e sieved , aerosolized , an d sample s wit h a dichotomou s sampler
. Thi s fin e surfac e soi l fractio n probabl yi s mor e relevan tt o th e exterio rdust s tha tadher e t o a child' s finger s an d ar e eate n (Dugga n an d Inskip , 1985)
. Sinc e a numbe ro f sample s wer e obtaine d afte rth e are a had bee n covere d byfin e volcani c as h fro m th e eruptio n o fMt
. St
. Helen s o n Ma y18 , 1980 , "Soi l sample s wer e collecte d afte rscrapin g awa yth e overburde n o fas h whic h probabl y als o remove d th e norma l aerosolizabl e dus tlayer
. Specia l car e wa s exercise d t o ensur e tha tth e as h di d no tcontaminat e th e underlyin g soi l whe n sampled
. Th e to p on e o rtw o centimeter s o fsoi l wer e collecte d by scrapin g wit h a spatula... " (Coppe re tal. , 1981 , pp . 114-115)
. Thi s stud yappear s t o b e o fmargina l relevanc e fo rstudyin g tim e trends
.P.2 1 B- 7 3 . Estimatin g Soi l an d Dus tLea d Level s Fro m Ambien tLea d Level s Th e assumptio n i n mos tanalyse s o fdat a aroun d existin g lea d poin t source s i s tha tth e environmenta l lea d emission s hav e bee n nearl y constan tfo ra sufficientl ylon g tim e tha tlea d level s i n soi l an d dus t ar e nearl yi n dynami cequilibrium
. Thus , fo rsom e parameter s ao , &\, bQ , t>l , t>2 , c 0 » c l » w e nav e th e followin g linea rrelation s fo rpredicte d geometri cmeans : G.M
. Pb S = a o + a i Pb

A(Equatio n 3.1 ) G.M
. Pb D = b o + b i Pb

A+ b2 Pb

S (Equatio n 3.2 ) G.M
. Pb D = c 0 + c i Pb

A(Equatio n 3.3 ) Becaus e thes e are

prediction s fo rgeometri cmean s an d ar e fitte d afte ra lo g transformation , w e kno wtha tc

^ f (b\ + a\ b2)
. Not e tha tc ^ > b ^ sinc e i tinclude s th e indirec tPb A-- > Pb

S -- > Pb

D pathway
. Th e value s show n i n Tabl e B- 2 wer e obtaine d fro m tw o dat a sets . SPT Arefer s t o th e 45 communit yaverage s fro m differen t lea d poin t source s reporte d i n Tabl e A-3
. E H i s base d o n a sampl e o fhousehold s wit h youn ychildre n obtaine d i n 198 3 i n Eas tHelena , Montana , byth e Center s fo rDiseas e Contro l an d th e Montan a Departmen to fHealt h an d Environmenta l Science s (CDC , 1983)
. Th e dat a o n tim e scale s fo rsoi l an d dus tlea d change s i s inconclusive
. Ou ropinio n i s tha tlea d i n undisturbe d soi l matri xpersist s fo ra n extremel ylon g time , bu ttha tsoi l lea d concentration s i n disturbe d (especiall yurban ) environment s wil l change , o n average , ove rperiod s o f a fe wyear s t o reflec tchange s i n surfac e deposition
. Interio rdus tlea d concentration s wil l likel ychang e ove ra perio d o fweek s t o month s i n respons e t o ai rlea d changes , dependin g o n interior-exterio racces s an d interio rrecirculatio n o rremova l o fdust
. Thu s th e followin g strateg y i s recommended
.P.2 2 

### B- 8
TABL E B- 2 LINEA R MODE L PARAMETE R ESTIMATE S FO R AIR : SOI L AN D DUS T LEA

D RELATIONSHIPS *

Dat a Se t SPT AEH
Paramete r ao

3 1 

### ° 0 ° 1 ° 2

^ 0

*Fro m(Marcus , 1988c ) G.M . PbS = ao + a i Pb A G.M . Pb D = bo + bi Pb

A+ b 2 PbS G.M . Pb D = C Q + c i Pb

A 50. 1

579. 0 33. 2 582. 0 0.51 4 57. 6 972. 0 88. 1 206. 0 184. 0 267. 0 0.89 4 220. 0 551. UB- 9

Th' e estimatio n o fchange s i n Pb S an d Pb

D fro m a chang e i n Pb A(brough t abou tfro m a hypothetica l chang e i n th e P b NAAQS ) ca n b e estimate d unde r tw o situations--short-ten n an d long-term
. I n th e long-term , equation s t o us e i n predictin g equilibriu m level s o fPb S an d Pb

D followin g a chang e i n Pb Aar e illustrate d b yequation s 3- 1 an d 3- 3 above
. Eac h predict s soi l o rdus tlea d dependen tonl yo n ai rlead , whic h wil l generall yb e th e onl y informatio n availabl e i n applie d polic yanalyses
. Whe n available , Pb

S i n combinatio n wit h Pb Ashoul d prov e fa rmor e predictiv e o fPb D tha n Pb

A alone , sinc e th e indirec tpathwa yfro m Pb At o Pb D throug h Pb

S i s probabl y a mor e importan tdus tlea d sourc e (Rabinowit z e tal. , 1985)
. Th e short-ter m change s i n Pb S an d PbA , however , requir e furthe r consideration
. I n tim e period s measure d i n term s o fsevera l months , w e woul d expec tt o se e littl e o rn o chang e i n Pb S fro m a chang e i n PbA
. Therefore , Pb

S woul d remai n constan ti n th e short-term
. I n contrast , dus tlead , bein g a soilin g phemonena , woul d b e expecte d t o chang e i n th e short-ter m a s a resul to fchangin g ambien tlea d concentrations
. Ther e are , however , tw o component s comprisin g th e leve l o fPbD
. Ther e i s direc tdepositio n fro m th e atmospher e an d secondar ydepositio n cause d by suc h factor s as reentrainmen t fro m th e soil
. Therefore , th e coefficient , b i , i n Equatio n 3. 2 mus tb e use d t o predic tshort-ter m change s i n Pb D (fro m equilibriu m levels ) fro m a chang e i n PbA
. Th e mode l i s intende d t o b e use d a tman ysites
. Ofth e tw o dat a set s tha twer e analyzed , th e SBT Adat a se ti s preferabl e becaus e i t include s site-to-sit e difference s i n soi l an d dus tslopes
. Slope s fro m an yparticula rlocatio n suc h as Eas tHelen a reflec t loca l climate , soi l type , accessibilit yo flea d soi l an d ai rt o th e interio ro fth e house , an d housecleanin g practice s relate d t o awarenes s o flea d hazards
. Thus ,P.2 4
B-1 0
a mode l base d o n th e E H dat a se tma

yno tb e as transportabl e t o othe r site s an d th e relationship s expresse d i n Appendi xAar e base d o n th e S8T A analyses
. 4 . Conclusion s W e hav e show n tha tth e relatio n betwee n soi l lead , dus tlead , an d ai rlea d i s expecte d t o var yove rtime , eve n unde rnear-equilibriu m conditions
. Th e variou s slope s ca n b e expecte d t o depen d o n site-specifi c propertie s suc h as th e depositio n rate , remova l rate , tota l airborn e suspende d particulat e concentration , an d non-ai rlea d influ xrat e fo r lead-contaminate d surfac e soils
. Ther e ar e almos tn o dat a tha tca n b e use d t o provid e estimate s o fcritica l kineti cparameter s suc h as soi l o r dus tlea d remova l o rturnove rrates . W e thu s sugges tcalculatin g th e expecte d change s i n Pb S an d Pb

D fro m equilibriu m relationships
. I n th e shor tter m ( a fe wmonths ) w e expec t littl e o rn o chang e i n surfac e soi l Pb , bu talmos tcomplet e equilibratio n o fth e Pb

A(only ) componen to fPb D an d n o chang e i n th e Pb S componen to fPbD , I n th e long-ter m (e.g. , te n year s afte ra Pb Achange ) w

e ca n us e th e full yequilibrate d Pb D vs . Pb

Aslop e tha tinclude s th e indirec tPb A-- > Pb S — > Pb

D pathway
.P.2 5



### APPENDI XC . ESTIMATIN G199 0 BASELIN E BLOO D LEAD AVERAGE S 1 . Introductio n I n estimatin g PbB level s expecte d unde ralternativ e lea d NAAQS , bot h th e disaggregat e mode l fo radult s an d fetuse s an d th e aggregat e mode l fo r youn g childre n requir e estimate s o fth e contribution s t o bloo d lea d fro m source s tha twil l b e unaffecte d bychange s i n atmospheri clea d relate d t o chang e i n th e lea d NAAQS
. Thes e source s include , fo rexample , solde ri n canne d food s an d plumbin g an d historica l depositio n o fgasolin e lead
. Bloo d lea d contribution s fro m non-ai rsource s o flea d ar e explicitl y accounte d fo ri n th e disaggregat e mode l fo rchildren , an d i n th e integrate d uptake/biokineti cmodel
. Thi s sectio n describe s methodolog yfor , an d result s of , estimatin g averag e bloo d lea d contribution s fro m non-ai rsources , o r "baseline " bloo d lea d level s fo rchildre n an d different , adul tpopulation s livin g i n 1990 . 199 0 i s th e startin g yea rfo rth e variou s exposur e analyse s tha twil l b e conducte d as par to fth e lea d NAAQ S review
. 2 . Approac h Ideally , w

e woul d kno

wcurren tPbB level s i n pregnan t women , middle age d men , an d youn g childre n livin g nea rpoin tsources . Know n bloo d lea d distribution s coul d the n b e adjuste d t o accoun tfo rth e continuin g downward trend s i n food , water , an d ai rlea d concentrations , describe d i n Sectio n II , i n orde rt o estimat e baselin e 199 0 bloo d lea d distributions
. Becaus e ther e hav e bee n n o recen tsystemati csurvey s o fPb B level s i n th e U.S. , baselin e bloo d lea d estimate s wil l hav e t o b e base d o n earlie rdata
. Th e mos trecent , an d well-conducted , nationwid e surve yo fPbB level s wa s th e Secon d Nationa l Healt h an d Nutritio n Evaluatio n Surve y(NHANES II ) o f197 6 t o 1980 . Sinc e then , lea d concentration s i n differen tmedi a hav e droppe d substantiall yan d hav e apparently , an d predictably , bee n accompanie dP.2 6 C- 2 b ysignifican treduction s i n lea d exposure . Th e approac h take n her e wil l be : 1 ) star twit h averag e PbB level s fro m 1978 , th e midpoin to fth e NHANE S I I survey ; an d 2 ) estimat e 199 0 bloo d lea d average s byadjustin g th e 197 8 value s fo rchange s i n gasolin e emissions , an d foo d an d wate rlea d concentrations , tha thav e recentl yoccurre d an d tha tca n b e expecte d t o continue
. Th e issu e o ffeta l lea d exposur e wil l b e addresse d separately
. 3 . 197 8 Bloo d Lea d Dat a Tabl e C- 1 list s mean PbB level s fo rselecte d populatio n subyroup s measure d as par to fNHANE S I I i n 1978 , base d o n dat a provide d t o OAQP S byJoe l Schwart z o fEPA' s Offic e o fPolicy , Plannin g an d Evaluation
. Thes e level s wil l serv e as startin g point s fo radjustment s t o accoun tfo r th e exposur e source s i n flux , describe d above
.

TABLE C-1
. SELECTE D 197 8 BLOO D LEA D LEVEL S FRO M NHANE S I I Populatio n (Age ) Geometri cMean Bloo d Lea d Leve l (pg/dl ) Childre n 14. 9 (0. 5 - 5 years ) Female s 10. 8 (15-4 4 years ) Whit e Male s 15. 4 (40-5 9 years ) Blac k Male s 17. 7 (40-5 9 years )P.2 7 C- 3 Blac k middle-age d me

n hav e no tbee n identifie d i n th e C D as a separat e sensitiv e group . Whit e middle-age d me n hav e bee n th e focu s o fth e tw o ke y populatio n studie s o n lead-relate d bloo d pressur e effect s (Britis h Regiona l Hear tStud yan d U.S
. NHANE S II ) i n orde rt o avoi d th e effect s o f confoundin g variable s an d becaus e o fles s extensiv e dat a fo rnon-whites
. Give n thei rhig h ris k o fcardiovascula rdisease , i ti s likel ytha t a similar , bu tpossibl yles s apparent , bloo d lead/bloo d pressur e relationshi p exist s i n blac k

male s an d therefore , bloo d lea d change s fo rthi s grou p wil l als o b e estimated
. 4 . Adjustmen tfo rGasolin e Lea d Phasedow n Th e stron g correlatio n betwee n gasolin e lea d consumptio n decline s an d th e downward tren d i n NHANE S I I PbB level s betwee n 197 6 an d 198 0 ha s bee n describe d i n th e 198 5 Regulator yImpac tAnalysi s fo rth e fina l rul e o n lea d i n gasolin e (EPA , 1985 ) an d th e C D (Sectio n 11.3.6)
. Simila rresult s wer e foun d wit h U.S
. childhoo d lead-screenin g dat a (Schwart z e tal. , 1984 ) an d i n a n Italia n isotop e experimen twher e fairl yrapi d change s i n gasolin e lea d produce d larg e change s i n adul tan d children' s bloo d lea d (Facchetti , 1985 ; CD , p . 11-87)
. Gasolin e lea d accounte d fo ra n estimate d 6 0 percen to fth e lea d i n th e averag e American' s bloo d i n th e secon d hal fo fth e 1970's , an d explaine d short-ter m seasona l increase s i n Pb B level s fro m winte rt o summe ras wel l as th e long-ter m drop
. Further , th e accelerate d rat e o fdeclin e i n yasolin e lea d afte r197 8 was parallele d bya n accelerate d declin e i n PbB levels
. Additiona l suppor tfo ra causa l associatio n betwee n gasolin e lea d an d bloo d lea d i s see n i n a ) th e bloo d lea d trend , whic h wa s consisten t throughou tth e entir e distribution , an d no tonl ythroug h truncatio n o fth e hig h bloo d lea d level s (CD , p . 11-185) ; b ) one-mont h lagge d gasolin e lea d sale s bein g th eP.2 8 C- 4 mos tsignifican tpredicto ro fbloo d lead , whic h matche s th e on e mont h half lif e o flea d i n bloo d (EPA , 1985 ; p . 3-24 ) an d i s consisten twit h result s o f Rabinowit z an d Needlema n (1982 , 1983 ) wh o foun d tha tmonthl ychange s i n gasolin e lea d exposur e wer e th e probabl e caus e o ftrend s i n umbilica l cor d PbB level s i n Bosto n birth s (CU , p . 11-39) ; an d c ) th e gasoline/bloo d lea d relationshi p bein g stabl e acros s demographi can d geographi cboundarie s an d betwee n th e firs t an d secon d halve s o fth e NHANE S I I survey , whe n gasolin e lea d level s wer e roughl y50 % lower
. Regressio n coefficient s estimate d fro m th e NHANE S I I analysi s afte r controllin g fo rage , race , sex , regio n o fth e country , season , income , degre e o furbanization , an d accountin g fo rlaborator yerror , change s i n dietar ylea d (includin g canne d food ) an d lead-painte d housin g an d othe r time-trends , hav e bee n use d t o predic tchange s i n bloo d lea d du e t o th e gasolin e lea d phasedow n (Annes te tal. , 1983 ; Schwart z e tal. , 1984)
. Th e phasedow n wil l hav e continuin g effect s a t leas tu p t o 1990-9 2 an d earlie rprojection s regardin g bloo d lea d change s ca n b e extende d usin g thes e regressio n coefficients
. Joe l Schwart z o fEPA' s Offic e o fPolic y Analysi s provide d th e coefficient s t o OAQP S (persona l communicatio n t o Jef fCohen , Ma

y9 , 1988) , derive d fro m regressin g natural-lo g bloo d lea d value s o n gasolin e value s sinc e th e dat a bes tfitte d a loy-norma l distrioution
. Simila ranalysi s b

yth e Center s fo rDiseas e Contro l an d tn e Nationa l Cente rfo rHealt h Statistic s ha s bee n describe d oyAnnes te tal
. (1983)
. Th e coefficient s wer e derive d fro m a perio d whe n gasolin e lea d consumptio n droppe d significantl yan d sinc e then , th e tren d ha s continue d t o a n eve n greate rextent . A s note d earlier , adult s hav e larg e store s o f skeleta l lea d accumlate d ove rtime s o fhighe rlea d exposures . Som e o f thi s lea d i s mobil e an d ca n b e resorbe d fro m bone s int o th e bloodstrea m afte rreduction s i n exposur e (Rabinowit z e tal. , 1977)
. Th e exten to fP.2 9 C- 5 suc h bon e lea d resorptio n an d th e amoun to ftim e fo rre-establishin g ne w steady-stat e PbB level s i n respons e t o decline s i n gasolin e lea d emission s sinc e NHANE

S I I i s difficul tt o quantify
. Th e onl yavailabl e direc tdat a o n bon e lea d resorptio n com e fro m excessivel yexpose d peopl e wh o ma yno t hav e th e sam e biokineti crate s a s thos e wit h lowe rexposures . Similarly , othe rstudie s usin g isotopi clea d tracer s ma yno tb e relevan tsinc e isotopi cexchang e rate s ma ydiffe rfro m bon e lea d resorptio n rates . Nevertheless , worker s expose d fo rperiod s u p t o 1 0 year s (O'Flahert ye t al. , 1982 ; Hryhorczu k e tal. , 1985 ) an d 2 0 year s (Ahlyre n e tal. , 1987 ) i n th e lea d industry , wit h Pb B level s as hiy h as 70 pg/d l (an d norma l rena l function ) had bloo d lea d half-live s betwee n 2 0 an d 70 0 day s an d showe d significan tbloo d lea d reduction s a s quickl ya

s 3 month s t o 2 years . Ever yindicatio n fro m th e NHANE S I I bloo d lead/gasolin e lea d analysi s (e.g. , shor ttim e lags , seasona l parallels) , an d othe rstudie s (e.g. , Facchett i e tal. , 1985 ) indicat e tha tnon-occupationall yexpose d adul tbloo d lea d level s respon d quickl y(e.g. , a s quickl ya

s on e month ) t o fluctuation s i n gasolin e lead
. Give n th e fac ttha tby1990 , th e curren t phas e o fth e gasolin e phasedow n regulatio n (i.e. , 0.1 0 grain s o flead/leade d gallon—curren tlevel s ar e slightl ylower ; D
. Kortum , EPA' s Offic e o fMobil e Sources , persona l communication ) wil l hav e bee n i n ful l effec tfo rabou t3 years , whateve rchange s predicte d base d o n th e 1976-198 0 NHANE S result s ca n reasonabl yb e applie d t o estimatin g "baseline " 199 0 bloo d lea d levels
. Tabl e C- 2 summarize s calculation s usin g th e regressio n coefficient s fro m NHANE

S I I alon g wit h gasolin e lea d t o estimat e change s i n averag e bloo d lea d expecte d fro m change s i n recen tan d futur e gasolin e lea d usage . Th e regressio n coefficient s wer e simila rfo rth e differen tpopulatio n groups . A s observe d i n th e NHANE S I I analysis , th e continue d dramati cdeclin e i nP.3 0

C- 6 TABL E C-2 . PREDICTE D CHANGE S INAVERAG E BLOO D LEAD LEVEL S

ASSOCIATE D WIT H GASOLIN E LEA D TREND
Childre n Wome n Whit e Me n Blac k Me n (0.5- 5 years ) (15-4 4 years ) (40-5 9 years ) (40-5 9 years ) 197 8 Geometri c Mea n PbB (pg/dl ) 14. 9 10. 8 15. 4 17. 7 Regressio n Coefficien t (lo g PbB change/10 0 ton s gasolin e P

b change) 3 .122 0 . . .155 8 .121 6 .121 6 Reductio n i n Gasolin e P b Consumption , 1977-7 8 t o 199 0 (tons/day) 0 43 5 43 5 43 5 43 5 Predicte d Reductio n i n Gas/Lea d Contributio n t o 199 0 Mean PbB (pg/dl ) -8. 6 -5. 5 -9. 1 -10. 5
Calculate d b

yJoe l Schwartz
. °Estimate s liste d below , o fgasolin e lea d usag e provide d b yJoh n Holle y an d Dave Kortu m o fEPA' s Offic e o fMobil e Sources , Fiel d Operation s an d Suppor tDivision ; 1990-9 2 projection s base d o n Turne rMaso n an d Company , 198 7 repor to n petroleu m industr ymarketing : 1977-7 8 198 8 •199 0 1992 c Tons/da y43 8 4. 8 2. 9 1. 4
c Despit e furthe rdeclin e i n 199 2 i n gas-lea d consumption , n o additiona l reductio n i n bloo d lea d level s predicte d bymodel
.P.3 1 C- 7 gasolin e lea d emission s i s predicte d t o paralle l a majo rshif t i n PbB levels
. Thi s declin e wil l b e use d alon g wit h adjustment s expecte d becaus e o fothe rlea d exposur e trend s t o estimat e averag e 199 0 baselin e bloo d lead
. 5 . Adjustmen tfo rDietar yLea d Reduction s Asignifican treductio n i n dietar ylea d intak e nas occurre d sinc e tn e lat e 1970's , an d thi s tren d wil l continu e as atmospheri clea d emission s an d deposition , th e us e o flead-soldere d cans , an d lea d level s i n drinkin g wate ral l continu e t o decline
. Sourc e contribution s t o childre n an d adul t diet s ar e estimate d i n Chapte r7 o fth e CD , a s describe d i n Sectio n II. D o fthi s paper . Age-specifi cestimate s o fdietar ylea d intak e i n childre n fo r1978 - 198 5 base d o n tha tinformatio n ar e detaile d i n Sledg e (1986 ) an d projection s o ffutur e lea d intakes , incorporatin g mor e recen tdat a i n Flege l (1988 ) hav e bee n estimate d fo rchildre n i n 199 0 (Cohen , 1988)
. Estimate d difference s i n dietar ylea d intak e betwee n 197 8 an d 199 0 ar e shown.i n Tabl e C-3
. Th e 1982 - 8 5 value s ar e take n directl yfro m Flegel.e t al
. (1988) , wh o showe d tha t earlie rprediction s usin g th e modelin g approac h develope d i n th e C D wer e validate d b yactua l dat a sinc e mad e availabl e b yFDA
. Th e 197 8 estimate s are •backwar d extrapolation s o fth e 1982-9 5 dat a usin g th e calculation s i n Sledg e (1986)
. Among children , onl y2-yea rold s ar e considere d fo rsimplicit y sinc e othe rchildre n woul d hav e roughl yth e sam e proportiona l decreas e i n dietar ylea d ove rthi s tim e period
. Likewise , th e 1978-198 5 extrapolation s fo radult s wer e calculate d b yassumin g th e sam e proportiona l decline s tha t occurre d i n 6-yea rolds ' dietar ylea d intake , give n tha tth e source s o flea d intak e among olde rchildre n are th e sam e a

s fo radult s (confirme d byRob Elia s o fEPA' s Environmenta l Criteri a an d Assessmen tOffice ; persona l communicatio n t o Jef fCohen , Marc h 9 , 1988)
. Th e dietar yintak e estimate s fo r1982 , base d o n th e C D analysis , wer e adjuste d fo rth e change s tha thav e occurre d an d tha tar e expecte d t o continue ,P.3 2 C- 8 TABL E C-3 . TREND S I NDIETAR

Y LEA D INTAKE (pg/day) : TOTA L INTAKE (AN

D ATMOSPHERI C CONTRIBUTIONS )

1978 3 1982 d198 3 198 4 198 5 1990 e 2 yea r old 52. 9 30. 6 21. 6 21. 7 13. 1 8. 8 childre n (27.0) ° (1.2) f Adul t Female s 65. 6 37. 9 27. 2 27. 6 14. 5 0. 2 (26.3) C (4.3) C Adul t Male s 91. 5 55. 2 36. 3 42. 5 19. 8 14. 1 (39.0) C (6.1) C

a 197 8 value s ar e extrapolation s base d o n estimate s i n Sledg e (1986) , assumin g a mean lea d i n drinkin g wate ro f1 2 pg/L
. °Atmospheri ccontributio n t o 197 8 dietar ylea d i n childre n fro m Sledg e (1986 ) base d o n Multipl e Sourc e Foo d Mode l develope d i n CD , Chapte r7 . c Atmospheri ccontribution s t o 197 8 an d 199 0 adul tdiet s derive d b ytakin g proportiona l contribution s t o 1982-198 5 diets , as provide d i n Flege l e t a l
. (1988)
. d 1982-8 5 value s ar e fro m Flege l e tal
. (1988)
. Exceptio n i s 198 2 valu e fo rchildre n whic h i s derive d i n Cohe n (1988 ) assumin g a mean ta p wate r lea d leve l o f1 2 pg/L
. e 199 0 projections , describe d i n Cohe n (1988 ) derive d byadjustin g 198 2 value s base d o n followin g assumptions : 1 ) switchove rt o lead-fre e can s wil l continu e such-tha t b y1989 , lea d level s i n canne d food s wil l b e 10 % o f198 2 values ; 2 ) averag e lea d leve l i n drinkin g wate rwil l dro p fro m 1 2 pg/ Lt o 8 pg/ Lby199 0 du e a ) t o nationwid e ba n o n lea d solde ran d lea d pipe s an d fitting s i n ne wconstructio n an d repairs , b ) publi c notificatio n requirement s unde r198 6 SDWA , c ) gradua l replacemen to fol d lea d pipe s i n severa l larg e cities , an d d ) revise d nationa l standar d fo r lea d i n drinkin g water . ^Atmospheri ccontributio n t o 199 0 children' s die tderive d i n Cohe n (1988 ) bymultivariat e regressio n analysi s usin g C D Multipl e Sourc e Foo d Model , FD Adata , an d projecte d gasolin e an d ambien tai rlea d data
.P.3 3 C- 9 du e t o th e phaseou to flead-soldere d cans , reduction s o flea d i n drinkin g water , an d reduction s i n atmospheri clea d depositio n ont o crop s an d othe r vegetation , t o yiel d 199 0 dietar yestimates
. Again , th e sam e proportiona l chang e i n dietar ylea d intak e fo ra 6-yea rold , estimate d betwee n 1982 - 8 5 an d 1990 , ca n b e assume d fo radult s sinc e th e source s o fdietar ylea d i n bot h diet s are

th e same . Par to fth e reductio n i n dietar ylea d intake s i s attributabl e t o reduce d depositio n o fatmospheri clea d particles , an d althoug h th e NHANE S I I regressio n coefficient s use d t o adjus tPbB level s fo rth e gasolin e phasedow n represente d tota l exposure , the yprobabl ydi d no t captur e much o fth e latte rpathwa ysinc e i ttake s som e tim e (a tleas tmor e tha n a month ) fo rchange s i n gasolin e lea d usag e t o b e reflecte d i n differen t foods
. Th e gasolin e lead/bloo d lea d coefficient s woul d likel yhav e bee n highe rhad a longe rtimefram e bee n analyzed
. Give n th e uncertaintie s o fprecisel yho wmuch dietar ylea d exposur e i s i n fac tcapture d byth e gasolin e lead/bloo d lea d coefficient,. a rang e o fassumption s wil l b e made
. A s a lowe rbound , w

e wil l assum e tha tth e adjustmen tdescribe d previousl yfo rgasolin e lea d reductions , base d o n 197 6 t o 198 0 data , wil l accoun tfo rreduction s i n atmospheri clea d contribution s t o dietar ylea d intake
. I n othe rwords , th e entir e reductio n i n dietar yintak e estimate d fro m 197 8 t o 199 0 (52. 9 pg/da y- 8. 8 pg/da y= 44. 1 pg/da yfo rchildren , fo rexample ) woul d b e considere d i n additio n t o th e adjustmen tfo rgasolin e lea d reductions
. Alternatively , th e contributio n o fatmospheri clea d depositio n wil l b e "factore d out " o fth e estimate s o f dietar ylea d intak e fo r197 8 an d 199 0 t o accoun tfo rreduction s i n gasolin e lea d usage . Atmospheri ccontribution s t o children' s dietar ylea d intake , fo rexample , ar e estimate d t o hav e bee n 27. 0 pg/da yi n 197 8 (Sledge ,P.3 4 

### C-1 0 1986 ) an d t o b e 1. 2 pg/da yi n 199 0 (Cohen , 1988)
. Factorin g ou tatmospheri c lea d depositio n fro m th e dietar ylea d intake s cite d abov e yield s 52.9 - 27. 0 = 26. 9 pg/da yfo r197 8 an d 8.8-1. 2 = 7. 6 pg/da yfo r1990 . Th e rang e o fdietar ylea d intak e reduction s estimate d betwee n 197 6 an d 199 0 fo r childre n i s therefor e comprise d o ftw o values--25.9-7. 6 = 18. 3 py/day , an d 52.9-8. 8 = 44. 1 pg/day
. Correspondin g range s fo radul tfemale s an d adul e male s ar e 33.4-55. 4 pg/da yan d 44.5-77. 4 pg/day , respectively
. T o estimat e th e impac to n bloo d lea d level s tha tchange s i n dietar y lea d hav e had , an d wil l continu e t o hav e by1990 , dose-respons e relationship s betwee n PbB level s an d lea d level s i n foo d and/o rwate rca n b e used
. Studie s relatin g bloo d lea d t o dietar yintake , measure d b yduplicat e diet s o r feca l lea d determinations , ar e summarize d i n th e C D an d th e mos trelevan t coefficient s relatin g dietar ylead , o r"slopes " ar e cite d i n Sectio n IV.B. l an d IV.B. 2 o fthi s report . Mos tavailabl e studie s are eithe ro n infant s o radults ; onl yon e mode l has bee n develope d specificall yfro m dat a o n youn g childre n bu ttha ti s base d o n a stud yi n whic h onl ykitche n wate rlea d concentrations , an d ho tdietar ylea d levels , wer e measure d (Laxe n e tal. , 1987)
. Slopes , i n unit s o fpg/d l PbB pe rp g dietar yP b intake/day , rang e fro m abou t.0 2 fro m adul tstudie s t o abou tU.U6 0 (U.K
. Centra l Directorate , 1982 ; Sherloc k e tal. , 1982 ) an d U.1 6 (Ry u e tal. , 1983 ) fro m infan tstudies
. Lea d intak e i n th e Ryu e tal
. stud ywa s lo w an d therefor e th e derive d slope , whic h assume s a linea rrelationship , i s probabl ya n overestimat e fo rth e change s i n dietar yexposur e level s bein g considere d here
. Lace ye tat. , (1985 ) provid e dat a t o relat e wate rlea d concentratio n t o bloo d lead
. Theysuggeste d a linea rrelationshi p betwee n bloo d lea d an d wate rlea d wit h a slop e o f0.06 2 pg/d l pe rpg/L
. Reanalysi s o fP.3 5
C-1 1 thes e dat a indicate d tha ta piecewis e linea rrelationshi p fi tas wel l a s non-linea rmodels , wit h a slop e o f0.2 5 pg/d l pe rpg/ Lfo rwate rlea d concentration s belo w2 0 ppm an d a lowe rslop e o f0.04 6 fo rwate rlea d abov e 2 0 ppm (Holtzma n an d Marcus , 1988)
. Drinkin g wate rlea d level s o n a weigh tbasi s i n thi s stud ycorrelate d ver ywel l wit h tota l dietar ylea d concentration , whic h i s no tunexpecte d sinc e 8/ 9 o fth e mass o fth e infan t diet s wa

s ta p water . Becaus e o fthi s clos e correlation , Lace ye tal
. use d wate rlea d concentratio n as a surrogat e fo rtota l dietar ylea d concentration
. Thus , th e relationshi p i n Lace ye tal
. wa s derive d t o predic tth e contributio n o ftota l die tt o bloo d lead
. Result s o fth e Lace ye t al
. analyse s ca n b e use d t o predic tchange s i n bloo d lea d b yconvertin g dietar ylea d intak e value s (i n pg/day ) t o concentration s i n term s o f pg/kg , o rppb , as follows : Dietar yLea d Intak e (pg/day ) xslop e (pg/dl ) Tota l Dietar yIntak e (Kg/day ) (pg/Kg ) where : reductio n i n dietar ylea d intak e betwee n 197 8 an d 199 0 i s i n th e

rang e o f18. 3 t o 44. 1 pg/day ; tota l dietar yintak e fo ra 2-yea rol d chil d i s estimate d a t1.50 2 kg/da y(C D , Tabl e 7-15) ; an d slop e fro m th e Lace ye tal
. stud yi s estimate d a t0.2 5 fo rlea d level s belo w2 0 pp b an d 0.04 6 fo rlevel s abov e 2 0 ppb
. Tabl e C- 4 present s result s o fth e abov e calculation s fo rchildren , alon g wit h adjustment s fo r197 8 adul tPb B level s derive d fro m multiplyin g th e slope s discusse d i n Sectio n IV.B. 2 byestimate d reduction s i n dietar y lea d intakes
. Thes e adjustment s wil l b e combine d wit h thes e mad e previousl y fo rth e gasolin e lea d phasedow n t o yiel d 199 0 averag e baselin e PbB levels
.P.3 6 C-1 2
TABL E C-4 . ADJUSTMENT S T O 197 8 MEA

NBLOOD LEA

D LEVEL S FO

R UIETAR

Y LEA D REDUCTION S Rang e o f D

i fference s Betwee n 197 8 an

d 199 0 Estimate d Dietar

yLea d Intak e (pg/day) a Pb B Reductio n Estimate d B y199 0 Du e t o Dietar y Lea d Reductio n (-py/d l ) D Childre n 18.3-44. 1 1.4-3. U Adul tFemale s 33.4-55. 4 

### 1.1-1. 8 Middle-age d Me

n 44.5-77. 4 1.4-2. 6

a Fro m Tabl e C-3
. Range s reflec tuncertaint yas t o ho wmuch o fth e adjustmen t fo rgasolin e lea d reductions , usin g NHANE S Il-derive d coefficients , capture s change s i n atmospheri ccontribution s t o dietar ylea d intake
. °Slop e value s use d t o conver tdietar ylea d intak e t o averag e bloo d lea d change s ar e fro m reanalysi s byHoltzma n an d Marcus , 198 8 o fLace ye tal
. (1985 ) fo rchildre n (se e text) ; an d 0.03 2 pg/d l pe rp g Pb/da yfo radult s (Sherloc k

e tal. , 1982 ; Cool s e tal. , 1976 ; se e Sectio n IV.8.2)
.P.3 7 C-1 3 6 . Adjustmen tt o Children' s Pb B fo rReduction s i n Materna l Exposur e Sinc e lea d exposur e has been , an d wil l continu e t o be , reduce d fo r women sinc e th e 1970's , Pb B level s i n childre n bor n sinc e the n ca n b e expecte d t o b e lowe ra s a result
. Ove rth e cours e o fth e NHANE S I I survey , much o fth e reductio n i n gasolin e lea d emission s wa s probabl y reflecte d i n lowere d maternal , as wel l as newbor n Pb B levels
. Thus , i t ca n b e assume d tha tth e adjustmen tt o children' s Pb B alread ydescribe d fo rgasolin e lea d change s sufficientl yinclude d an ygasoline-attributabl e reduction s materna l lea d exposure . Reductio n i n materna l PbB attributabl e t o change s i n PbB dietar y lea d intake , however , i s no treflecte d i n adjustment s mad e previously
. On e metho d t o accoun tfo rthi s i s byusin g a kineti cmode l fi tt o bloo d lea d dat a collecte d longitudinall yfro m youn g childre n fro m birt h t o 2 7 month s (Succo p e tal. , 1987)
. Thi s mode l provide s a rat e o fbloo d lea d chang e whic h ca n b e applie d t o th e amoun to fnewbor n bloo d lea d affecte d byreduction s i n materna l dietar ylea d intak e estimate d betwee n 197 8 an d 19.90 . A

s wil l b e show n i n Sectio n C. 8 below , th e rati o betwee n newbor n PbB t o materna l PbB i s o n averag e aroun d 0.8 . Thus , th e followin g equatio n i s derive d t o accoun tfo rth e propagatio n o fPb B reduction s i n women , du e t o dietar ychange s (1. 1 - 1. 8 pg/dl) , t o 2-yea rolds : [(1. 1 - 1. 8 pg/dl ) x0.8 ] * e" a t= dPbB m where : th e rat e constan t« = 0.07 2 (Succo p e tal. , 1987 ) t= 2 4 month s d PbBr p = Pb B reductio n i n 2-yea rold s expecte d i n 199 0 du e t o reduction s i n materna l dietar ylea d intake
.P.3 8
C-1 4 Th e resultin g rang e fo rdPbB m i s 0. 2 - 0. 3 pg/d l a tag e 2 . Thi s adjustmen twil l b e combine d wit h th e other s fo r2 yea rol d childre n t o yiel d a n expecte d backgroun d mean Pb B fo r1990 . 7 . Adjustmen tfo rImplementatio n o fth e Lea d NAAQ S Th e midpoin to fth e NHANE S I I survey , 1978 , wa s th e yea rth e curren t lea d NAAQ

S wa s promulgated
. Sinc e the n ai rlea d level s hav e droppe d dramaticall ythroughou tth e country , mainl ydu e t o th e gasolin e phasedown , bu tals o becaus e o fimplementatio n o fth e ai rstandard , especiall yi n area s dominate d byindustria l poin tsourc e emissions
. Sinc e th e bul k o f th e NHANE

S I I sampl e live d i n urba n o rrura l areas , fairl yremot e fro m majo rlea d poin tsources , i twil l b e assume d tha tcorrectin g fo rth e gasolin e lea d phasedow n wil l captur e mos to fth e reductio n i n ai rlea d exposure s tha tha s occurre d sinc e implementatio n o fth e standard
. 8 . Additiv e Adjustment s t o 197 8 Bloo d Lea d Leve l Average s Tabl e C- 5 summarize s th e derivatio n o fmean PbB level s estimate d fo r fou rsubpopulation s i n 1990 . Thes e average s reflec t change s tha thav e occurre d sinc e 1978 , an d tha tar e expecte d t o continue , i n gasolin e lea d emission s an d deposition , canne d foo d technology , an d corrosio n contro l fo rlea d i n drinkin g water . An yothe rchange s no tquantifie d wer e probabl y o flesse rimportanc e fo rth e bul k o fth e NHANE

S I I populatio n (e.g. , reduction s i n industria l poin tsourc e emissions)
. Th e 199 0 baselin e average s ca n subsequentl yb e use d t o mode l exposur e change s expecte d unde ralternativ e lea d NAAQ S betwee n 199 0 an d 199 6 usin g th e disaggregat e mode l fo radult s an d th e aggregat e mode l fo rchildren
. Th e methodologie s fo rthes e model s ar e discusse d i n Sectio n V
.P.3 9 C-1 5 Tabl e C-5 . DERIVATIO NOF 199 0 "BASELINE " AVERAGE BLOOD LEA D LEVEL S Childre n Wome n Whit e Me n Blac k Me n ( 2 years ) (15-4 5 years ) (40-5 9 years ) 197 8 NHANE S I I 14. 9 10. 8 15. 4 17. 7 Averag e (pg/dl) * Adjustmen t fo r 8. 6 5. 5 9. 1 10. 5 Gasolin e P

b Phasedow

n (-pg/dl ) Adjustmen t fo r 1. 4 - 3. 0 1. 1 - 1. 8 1. 4 - 2. 5 1. 4 - 2. 5 Dietar yLea d Reduction s (-pg/dl ) Adjustmen t fo r 0. 2 - 0. 3 Reduction s i n Materna l Exposure s (
- Pg/dl ) Estimate d 3. 0 - 4. 7 3. 5 - 4. 2 3. 8 - 4. 9 4. 7 - 5. 8 199 0 Averag e (pg/dl ) 

### 1 ^Geometri cMean Level sP.4 0
C-1 6 8 . Estimatin g Feta l Exposure s Differen tindice s o fprenata l an d neonata l lea d exposur e hav e bee n foun d i n longitudina l studie s t o correlat e wit h delay s i n earl ymenta l an d physica l development
. Lea d readil ycrosse s th e placent a an d accumulate s i n feta l tissue s throughou tdevelopment
. Th e dynamic s o flea d exchang e durin g pregnanc yar e comple xan d poorl yunderstoo d (se e C D Addendum)
. Ideally , seria l measurement s o fmaterna l lead , o ri fpossible , embryoni clead , woul d hav e bee n take n i n th e studie s an d biokineti cmodel s woul d exis ttha tca n estimat e actua l feta l exposures . I n th e absenc e o feither , th e questio n i s whethe requilibrate d PbB level s i n pregnan twomen , as wil l b e estimate d i n th e disaggregat e modelin g describe d i n Sectio n V , ar e adequat e surrogate s fo rcritica l feta l lea d exposure , o ri s ther e a bette rindex
. Umbilica l cor d bloo d lead , fo rexample , whic h ha s bee n a ke yeffect s predicto ri n severa l studies , coul d b e estimate d byadjustin g materna l PbB • prediction s an d applie d t o availabl e dose-respons e relationship s t o asses s risks
. Tabl e C- 6 list s availabl e dat a o n paire d mother/chil d PbB concen tration s alon g wit h ratio s betwee n averag e materna l an d cor d Pb B levels
. Th e consistentl yhig h ratio s (mea n o f0.8 0 o r0.82 , dependin g o n th e inclusio n o fon e stud ywit h outlyin g results ) indicate s tha tth e matur e fetu s absorb s a sizabl e fractio n o fcirculatin g materna l lead
. Cor d bloo d lead , however , ma yno taccuratel yreflec tindividua l circumstance s o rpas texposur e levels
. I n a tleas tsom e pregnancies , ther e coul d b e greate rtha n norma l transfe ro f lea d fro m mothe rt o th e fetus
. I n addition , integrate d exposur e level s durin g th e cours e o fpregnanc yma yno tb e accuratel yindexe d bybloo d lea d level s a t deliver yo rbysingl e measurement s durin g pregnancy . Averag e materna l PbB level s ca n fluctuat e considerabl ydurin g pregnanc y(C D Addendum , p . A-45) , whil e th e equilibriu m betwee n bloo d an d sof t an d skeleta l tissue s i n th eP.4 1 C-1 7 Tabl e C-6 . MATERNAL : CHIL D BLOOD LEA D CONCENTRATION S AN D RATIO S

Study/Locatio n Numbe r o f Mean Blood Lea d (pg/dl ) Rati o o f Subject s Materna l Cor d Newbor n Cord : Materna l Pb B Barltrop (1968)/U.K . Harri s an

d Holley 

### 2 9 

### 13. 9 10. 8 (1972)/U.S
. Haas (1972)/German y Zetterlun d e tal
. (1977J/ 4 area s i n Swede n A B C D Clar k (1977)/Zambi a

- Contro l

- Min e Hubermon t e tal
. (1978) / Belgiu m Buche te tal
. (1978) / Belgiu m Dragovi c(1980) / Yugoslavi a -Smelte r -Contro l Alexande ran d Delve s (1981)/U.K
. Moor e e tal
. (1982) / U.K
. Winnek e e tal
. (1985) / FR G Ernhar te tal
. (1986) / U.S
. 2 4 29 4

2 1 173 103 37 3 1 12 2 70 47 4
102 45 16 5 23 6 11 4 11 8 13. 2

16. 9

6. 1 9. 2 8. 4 9. 4 14. 7 41. 2 12. 0 10. 4
32. 6 18. 6 12. 2 14. 0 9. 3 6. 5 12. 3

14. 9

4. 4 8. 0 7. 3 6. 8 11. 8 37. 0 10. 1 8. 3
28. 3 17. 3

- 12. 0 8. 2 5. 9 

### 11. 0 0.7 8 

### 0.9 3 0.8 8

0.7 2 0.8 7 0.8 7 U.7 2 

### 0.8 0 0.9 0 0.8 4 0.8 0


### 0.8 7 0.9 3

10. 0 0.8 6

0.8 8 0.9 1 McMichae l e tal
. (1986) / Australi a Por t Pori e 51 9 Othe r 17 2 10. 8 7. 7 10. 1

6. 2 11. 2

7. 5 0.9 4

0.8 1P.4 2


### C-1 8 Tabl e C-6 . MATERNAL : CHIL D BLOO D LEAD CONCENTRATION S AND RATIO S (Continued ) Roel s an d Lauweyr s (1987) / Belgiu m 47 4
Dietric h e tal
. (1987) / 30 5 U.S
. 

### 10. 1
8. 0 8. 4

6. 3 

### 4.6
-

5. 9 0.8 3



### 0.7 9 Bellinge re tal
. (1986) / U.S
. 

## 21 6 6. 5 6.2
- 7. 7 Milma n e t al . (1988) / Denmar k 4 8 3 6 2 0 0.5 7 Fahi m e tal
. U.S
. Regio n I Regio n I I (1976) / 24 0 177 13. 1

14. 3 4. 3

4. 6 Weighte d Mean : 0.8 2 0.3 3 0.3 2 Weighte d Mean : 0.8 0P.4 3 C-1 9 mothe ri s displaced , an d lea d i s transferre d t o th e placent a an d feta l tissues ; Alexande ran d Delve s (1981 ) foun d a n almos t20% dro p i n materna l PbB level s fro m 8 weeks unti l delivery
. Mobilizatio n o fbon e lea d store s durin g pregnanc yan d lactatio n ma yb e mor e substantia l i n som e women , an d iro n an d calciu m deficiency , bot h commo n i n pregnancy , enhance s gastro intestina l absorptio n o flea d (Rom , 1976)
. Whil e ther e ar e significan tuncertaintie s associate d wit h predictin g Pb B level s amon g pregnan twomen unde ralternativ e regulator yscenarios , ther e ar e dat a sufficien tt o a tleas tenabl e identificatio n an d boundin g o fth e uncertainties
. Attemptin g prediction s o factua l feta l lea d exposur e i s highl yuncertai n an d th e chanc e o funderpredictin g exposure s i s great . Therefore , fo rpurpose s o fassessin g risk s associate d wit h feta l lea d exposures , Pb

B leve l estimate s generate d fo rpregnan tmother s wil l b e use d a s surrogate s wit h n o furthe radjustment
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