### 30526 8 

## ADMINISTRATIV E RECOR D
BASELIN E HUMA N HEALT H RIS K ASSESSMEN T F O R TH E CALIFORNI A GULC H SUPERFUN D SIT E PART C EVALUATIO N O F WORKE R SCENARI O

APRI L 199 5
Prepare d for : U.S

. Environmenta l Protectio n Agenc y Regio n Vff l On e Denve r Plac e 99 9 18t h Street

, Suit e 50 0 Denver

, Colorad o 80202-240 5 E P A Wor k Assignmen t No

. Documen t Control No

. 4800-32-009 0 Prepare d by : R OY F

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, INC

. 21 5 Unio n Boulevard

, Suit e 55 0 Lakewood

, Colorad o 80228-162 2

### Forewor d This documen t i s a portio n o f on e o f thre e part s o f th e baseline huma n healt h ris k assessmen t
a t th e Californi a Gulch Superfun d Site

. Althoug h thi s part (Par t C ) wa s prepare d firs t (prio r t o th e completio n o f Part s A an d B)

, th e tex t make s referenc e t o th e planne d content s o f Part s A

an d B s o tha t Par t C ma y b e combine d wit h thes e section s withou t furthe r editin g afte r the y ar e completed

. Thi s assessmen t ha s bee n performe d followin g extensiv e consultatio n wit h EP A Headquarter s offices
, regiona l offices
, an d th e Agency' s Technica l Revie w Workgrou p fo r Lead

. This assessmen t represent s Regio n VIIF s bes t estimat e o f ris k base d o n exposur e parameter s specifi c t o the Californi a Gulc h site

. Us e o f thes e parameter s a t othe r site s withou t carefu l consideratio n o f site-specifi c informatio n i s discouraged

.

Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48J2_9 0TABL E O F CONTENT S Sectio n Titl

e Forwar d

............................................ . i i 1. 0 Introductio n
.......................................... . 1 1. 1 Sit e Descriptio n and Histor y
............................ . 1 1. 2 Fina l Huma n Healt h Ris k Assessmen t

...................... .

1 

### 1. 3 Approac h t o Par t C o f th e Ris k Assessmen t

................... .

2 2. 0 Lea d Evaluatio n
........................................ . 3 2. 1 Overvie w
....................................... . 3 2. 2 Populatio n o f Principl e Concer n
.......................... . 4 2. 3 Targe t Bloo d Lea d Level s i n Pregnan t Wome n
................. .

5 2. 4 Measured Bloo d Lea d Value s i n Wome n h i Leadvill e
............. .

5 2. 5 Predicte d Bloo d Lea d Level s i n Pregnan t Wome n
............... .

6 2.5. 1 Basi c Equation
................................ . 7 2.5. 2 Inpu t Parameter s

............................... . 7 2.5. 3 Result s

................................... . 1 3 2. 6 Calculatio n o f Workplac e Soi l Actio n Level s for Lea d

........... .

1 3 2.6. 1 Overvie w
.................................. . 1 3 2.6. 2 Basi c Equatio n
............................... . 1 5 2.6. 3 Uncertaint y PDF s

............................. . 1 6 2.6. 4 Result s

................................... . 2 0 2.6. 5 Compariso n o f Actio n Level s wit h Measure d Concentration s

... . 2 0 2.6. 6 Sensitivit y Analysi s

............................ . 2 0 2. 7 Weight-Of-Evidenc e

Evaluatio n
......................... .

2 0 3. 0 Arseni c Evaluatio n
..................................... . 2 4 3. 1 Predicte d Arseni c Risk s h i Leadvill e Worker s

................ .

2 4 3.1. 1 Basi c Equation s

.............................. . 2 4 3.1. 2 Inpu t Parameter s

.............................. . 2 4 3.1. 3 Result s

................................... . 2 7 3. 2 Calculatio n o f Workplac e Soi l Actio n Leve l fo r Arseni c
.......... .

2 9 3.2. 1 Basi c Equatio n
............................... . 2 9 3.2. 2 Uncertaint y PDF s

............................. . 3 0 3.2. 3 Result s

................................... . 3 1 3.2. 4 Compariso n wit h Sit e Concentration s

................. .

3 4 4. 0 Discussio n an d Conclusion s

................................ . 3 6 5. 0 Reference s

.......................................... . 3 7 Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48_32_9 0LIS T O F TABLE S 

### Tabl e Titl

e 1 Summar

y o f Variabilit y Distributio n Function s Fo r Estimatio n o f Lea d Exposur e i n Worker s 2 Summar

y o f Uncertaint y Distributio n Function s Fo r Estimatio n o f Lea d Soi l Actio n Leve l
3 Summar

y o f Variabilit y Distributio n Function s Fo r Estimatio n o f Arseni c Exposur e i n Worker s 4 Summar

y o f Uncertaint y Distributio n Function s Fo r Estimatio n o f Arseni c Soi l Actio n Leve l LIS T O F FIGURE S Figur e Titl

e 1 Uncertaint

y i n Soi l Actio n Leve l fo r Lea d 2 Lea d Isoconcentratio n Ma p 3 Uncertaint

y i n Soi l Actio n Leve l fo r Arseni c 4 Arseni

c Isoconcentratio n Ma p APPENDI X A
— ESTIMATIO N O F LEA D BKS F APPENDI X B

— SENSITIVIT Y ANALYSI S O F BOWER S MODE L

Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48_32_9 0EVALUATIO N O F WORKE R SCENARI O

1. 0 INTRODUCTIO

N

1 . 1 SIT E DESCRIPTIO N AN D HISTOR Y The Californi a Gulc h Superfun d Sit e i s locate d i n and aroun d the communit y o f Leadville

, Colorado

, abou t 10 0 mile s southwest o f Denver

. Leadvill e wa s th e sit e o f extensiv e mining , millin g an d smeltin g operation s beginnin g abou t 1860

. Mos t o f th e operation s ha d cease d b y abou t 1900 , although severa l facilitie s continued operation s int o th e 1920 s (Wester n Zinc ) an d th e 1960 s (A V Smelter ) (Wals h 1993)

. Nearl y al l o f th e mine s withi n th e sit e boundarie s ar e presentl y inactiv e an d al l o f th e mill s an d smelter s hav e bee n demolished

. Par t A o f thi s repor t present s a mor e detaile d histor y o f th e minin g and refinin g operations h i Leadville

, alon g wit h detaile d sit e maps

. Th e sit e wa s place d on th e Nationa l Priorities Lis t (NPL ) i n 198 3 mainl y becaus e o f concer n ove r th e impact o f min e drainage o n surfac e water s h i th e Californi a Gulc h an d th e Arkansa s River

. Subsequen t sit e investigations reveale d th e presenc e o f a numbe r o f heav y metal s i n soil s i n an d aroun d th e curren t residentia l an d commercia l area s o f Leadville

, an d a preliminar y ris k assessmen t (WESTO N 1991 ) indicate d tha t contaminan t level s wer e hig h enoug h t o b e o f potentia l huma n healt h concern
. Lea d an d arseni c wer e identifie d a s bein g th e primar y chemical s o f potentia l huma n healt h concern
. 1 . 2 FINA L HUMA N HEALT H RIS K ASSESSMEN T Sinc e th e tun e th e sit e wa s place d o n th e NPL

, th e U.S

. Environmenta l Protectio n Agenc y (EPA ) and a numbe r o f Potentiall y Responsibl e Partie s (PRPs ) hav e performe d a variet y o f studies t o defin e th e natur e an d exten t o f contaminatio n a t th e sit e an d t o hel p evaluat e th e leve l

o f ris k whic h sit e contaminant s pos e t o humans

. Base d o n thes e data
, th e EP A i s preparin g a Fina l Baselin e Huma n Healt h Ris k Assessmen t fo r th e site

. This comprehensive ris k assessmen t wil l consist o f thre e mai n parts , a s follows :
• Par t A i s t o evaluat e th e risk s whic h lea d h i th e environmen t pose s t o curren t an d futur e resident s o f the communit y
• Par t B i s t o evaluat e th e risk s whic h metal s other tha n lea d pos e t o curren t an d futur e resident s o f th e communit y • Par t C i s t o evaluat e th e risk s whic h environmenta l contaminatio n pose s t o curren t
o r futur e worker s h i th e commercia l an d busines s distric t o f th e community, an d t o peopl e wh o engage h i recreationa l activities (hunting

, hiking
, bik e riding
, picnicking
, etc. ) h i area s h i an d aroun d th e community

. Baselin e Huma n Healt h Ris k Assessment fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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### Thi s documen t i s on e portio n o f Par t C o f th e ris k assessment , coverin g population s expose d t o environmenta l contaminant s i n th e workplace

. 1. 3 APPROAC H T O PAR T C O F TH E RIS K ASSESSMEN T I n respons e t o concern s raise d b y Leadvill e official s an d busines s leaders ove r potentia l liabilitie s associate d wit h developmen t o f businesse s withi n th e Superfun d site , EP A committe d t o performin g a n "expedited " ris k evaluatio n t o determine
, a s quickl y a s possible
, i f environmenta l contaminatio n wa s o f concer n a t an y location s presentl y zone d fo r commercia l an d industria l purposes , an d i f so , t o defin e wher e remedia l action s wer e an d wer e no t needed

. Similarly

, i n orde r t o addres s potentia l concern s regardin g th e developmen t o f a propose d bik e pat h aroun d th e community, EP A committe d t o performin g a n expedite d evaluatio n o f potentia l risk s associate d wit h recreationa l lan d use

. I n order t o perfor m thes e ris k assessment s o n a n accelerate d schedule
, EP A incorporate d th e followin g assumption s an d approache s int o th e standar d ris k assessmen t procedures : 1

. Th e assessment s focu s onl y o n lea d an d arsenic

. Eve n thoug h othe r metal s occu r a t elevate d concentration s h i th e environmen t aroun d Leadvill e (e.g.

, se e WESTO N 1991)

, experienc e a t othe r sites , a s wel l a s th e result s o f preliminar y calculation s a t thi s site , indicat e tha t lea d an d arseni c ar e th e "ris k drivers"

. Thus

, focusin g o n thes e tw o chemical s i s no t likel y t o underestimat e risk

. 2

. Th e assessment s focu s onl y o n exposur e t o soi l an d dust
, an d onl y b y th e ingestio n pathway

. Exposur e t o othe r medi a (e.g.

, wast e piles
, sediments
, surfac e water , etc. ) an d exposur e t o soil/dus t vi a other pathway s (e.g.

, dermal
, inhalatio n o f particulates ) ar e considere d t o b e o f mino r concer n fo r workers

. 3

. Rathe r tha n calculatin g ris k a t al l specifi c propertie s an d locations wher e commercia l lan d us e i s possible
, calculation s wer e performe d for bot h lead an d arseni c t o identif y concentration s ("actio n levels" ) i n soi l whic h wer e o f potentia l
concern , an d these concentration s wer e compared t o finding s o f remedia l investigations o f soi l concentratio n value s i n orde r t o identif y location s wher e thes e value s migh t b e exceeded

. The specifi c method s use d fo r calculatin g actio n level s fo r lea d an d arseni c h i soi l ar e detaile d below
, alon g wit h the result s o f the evaluation s fo r commercia l lan d us e scenarios

.

Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48_32_9 02. 0

LEA D EVALUATIO

N

2. 1 OVERVIE W Th e healt h risk s whic h lea d pose s t o a specifie d populatio n can ofte n b e investigate d i n tw o differen t ways : • Direc t measuremen t o f bloo d lea d value s h i member s o f th e populatio n o f concer n • Measuremen

t o f lea d h i environmenta l media
, an d calculatio n o f th e rang e o f risk s thos e level s o f lea d coul d pos e t o individual s o r population s A s discusse d below
, eac h o f thes e approaches ha s som e advantage s an d som e limitations
, an d th e bes t assessmen t o f lea d risk s incorporates th e result s o f bot h type s o f approaches

. Bloo d Lea d Monitorin g On e wa y t o investigat e th e huma n healt h risk s fro m lea d i n th e environmen t i s t o measur e th e concentratio n o f lea d i n th e bloo d (PbB ) h i randomly-selecte d member s o f th e populatio n o f
concern
. Th e healt h risk s associate d wit h thes e measure d Pb B value s ca n b e evaluate d b y compariso n t e curren t guideline s fo r acceptabl e values

. Bloo d lea d studie s tha t als o includ e reliabl e environmenta l an d demographic s dat a ca n provid e valuabl e insight s int o th e medi a an d exposur e pathways tha t ar e th e primar y source s o f concer n h i a population

. However

, ther e ar e som e limitation s t o th e us e o f bloo d lea d measurement s a s th e onl y inde x o f lea d risk

. First

, car e mus t b e take n t o ensur e tha t a sufficien t numbe r o f peopl e ar e studied
, an d tha t thes e peopl e are a representativ e sub-se t o f th e populatio n o f concern
. Second

, bloo d lea d value s h i a n individua l ma y var y a s a functio n o f tune , s o a singl e measuremen t ma y no t b e representativ e o f th e long-ter m averag e valu e h i tha t individual

. Third

, i t i s expecte d tha t bloo d lea d value s wil l diffe r betwee n individuals
, eve n whe n the y ar e expose d unde r th e sam e environmenta l conditions

. Thus

, a n acceptabl e bloo d leve l measure d i n on e individua l (e.g.

, a worke r a t a commercia l establishment ) doe s no t necessaril y mea n tha t som e other individua l (e.g.

, som e othe r worke r wh o migh t b e expose d a t th e sam e locatio n h i th e future ) migh t no t hav e a highe r (an d possibl y unacceptable ) bloo d lea d level

. Fourth

, population-base d studie s ar e no t well-suite d t o detectin g th e occurrenc e o f occasiona l sub-location s wher e ris k i s elevated
, eve n i f averag e risk s ar e acceptable

. Finally

, bloo d lea d measurement s reflec t exposures and risk s unde r curren t sit e conditions
, whic h ma y no t alway s b e representativ e o f pas t o r futur e sit e conditions

. Fo r thes e reasons, result s fro m bloo d lea d studies ma y no t provid e a complet e descriptio n o f th e rang e o f risk s whic h migh t exis t h i a population

. Predictiv e Approac h Becaus e o f th e limitation s h i th e direc t measuremen t approach
, i t i s valuabl e t o emplo y a predictiv e a s wel l a s a n empirica l metho d fo r evaluatio n o f lea d risk

. Thes e model s ca n the n b e use d t o asses s th e risk s fro m lea d unde r condition s whic h canno t b e measure d (e.g.

, risk s t o Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48_32_9 0hypothetica l

futur e peopl e i n a n are a wher e ther e ar e n o curren t exposures)

, t o identif y whic h exposur e pathways ar e likel y t o b e contributin g th e larges t ris k t o a population
, an d t o evaluat e th e likel y efficac y o f variou s remedia l alternatives

. A numbe r o f predictiv e lea d exposur e model s exist

. For example
, th e EP A ha s develope d an integrate d exposure , uptak e and biokineti c (IEUBK ) mode l t o asses s the risk s o f environmenta l exposur e h i residentia l children

. I n addition
, model s hav e als o bee n develope d b y Bower s et.a l (1994)

, O'Flahert y (1993)

, Legge t (1993 ) an d th e Stat e o f Californi a (CEP A 1992 ) t o asses s th e effect s o f lea d exposur e h i olde r childre n an d adults

. I n general
, thes e model s requir e (a s site

specifi c input ) informatio n o n th e level s o f lea d h i variou s environmenta l media
, an d o n th e amoun t o f thes e medi a contacte d b y th e populatio n o f concern
. Fro m thi s input , th e model s calculat e th e expecte d level s o f bloo d lea d h i th e expose d population

. However

, al l predictiv e model s ar e subjec t t o a numbe r o f limitations

. First

, ther e i s inheren t difficult y h i providin g th e mode l wit h reliabl e estimate s o f huma n exposur e t o lead-contaminate d media

. For example
, exposur e t o soi l and dust i s difficul t t o quantif y becaus e sinc e huma n intak e o f thes e medi a ar e likel y t o b e highl y variable
, an d i t i s ver y difficul t t o derive accurat e measurement s o f actua l intak e rates

. Second

, i t i s ofte n difficul t t o obtai n reliabl e estimates o f ke y pharmacokineti c parameter s h i human s (e.g.

, absorptio n fraction
, distributio n an d clearanc e rates)

, sinc e direc t experiment s i n human s i s not acceptable

. Finally

, the absorption
, distributio n an d clearanc e o f lea d h i th e huma n bod y i s a n extremel y complicate d process , an d an y mathematical mode l intende d t o simulat e th e actua l processe s i s likel y t o b e a n over
simplification

. Thus

, mode l calculations an d prediction s ar e usuall y rathe r uncertain

. Weight-of-Evidenc e Evaluatio n A s th e discussion s abov e mak e clear
, ther e ar e advantages an d limitation s t o bot h th e direct bloo d measuremen t approac h an d th e UB K modelin g approach

. Therefore

, th e mos t appropriat e mean s fo r evaluatin g risk s fro m lea d i s t o conside r the result s o f bot h analyses
, takin g int o accoun t th e uncertaintie s an d limitations o f each

. Fina l conclusion s regardin g curren t an d futur e ris k shoul d thu s b e base d o n a balance d assessmen t o f informatio n fro m al l sources

. 2. 2 POPULATIO N

O F PRINCIPL E CONCER N Usually

, lea d ris k assessment s focu s on youn g children
, sinc e youn g childre n ten d t o hav e highe r lea d exposure s tha n olde r childre n o r adults
, becaus e youn g childre n ten d t o absor b mor e lea d tha n d o adults
, an d becaus e youn g childre n are mor e susceptibl e t o th e advers e effect s o f lea d
o n th e nervou s system

. Par t A o f thi s ris k assessmen t provide s a mor e thoroug h descriptio n o f th e advers e effect s o f lea d h i children
, an d present s a n evaluatio n o f th e risk s whic h lead ma y pos e t o childre n wh o liv e h i Leadville

. Thi s part o f th e ris k assessmen t focuse s o n lea d risk s t o worker s (assumed t o b e adults)

. Withi n thi s population
, th e subpopulatio n mos t likel y t o b e o f concer n ar e pregnan t women
. Thi s i s becaus e pregnant wome n ma y ten d t o absor b mor e lea d tha n non-pregnan t wome n o r men , an d becaus e th e fetu s o f th e pregnant wome n i s likel y t o b e especiall y susceptibl e t o th e advers e
Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48_32_9 0effect

s o f lead

. Therefore

, pregnant wome n an d wome n o f child-bearin g ag e ar e selecte d a s th e sub-populatio n o f principl e concern
. 2. 3 TARGE T BLOO D LEA D LEVEL S I N PREGNAN T WOME N Th e EP A ha s no t ye t issue d forma l guidanc e o n th e bloo d lea d level tha t i s considere d appropriat e fo r protectin g th e healt h o f pregnan t wome n o r other adults

. However

, EP A recommend s tha t ther e shoul d b e n o mor e tha n a 5 % likelihoo d tha t a youn g chil d shoul d hav e a Pb B valu e greate r tha n 1 0 ug/d L (EP A 1991b)

. Sinc e th e expose d worke r an d recreationa l population s a t thi s sit e ar e assume d t o includ e pregnant women , an d becaus e th e fetu s i s expose d t o lea d level s nearl y equa l t o thos e o f th e mother
, th e healt h criterion selecte d fo r use i n thi s evaluatio n i s tha t ther e shoul d b e n o mor e tha n a 5 % chanc e tha t th e fetu s o f a pregnan t woma n woul d hav e a Pb B abov e 1 0 ug/dL

. Thi s healt h goa l i s equivalen t t o specifyin g tha t th e 95t h percentil e o f th e Pb B distributio n h i fetuse s doe s no t excee d 1 0 ug/dL : PbB^feta l < 1 0 ug/d L Th e relationshi p between feta l an d materna l bloo d lea d concentratio n ha s bee n investigate d h i
a numbe r o f studies

. Goye r (1990 ) reviewe d a numbe r o f thes e studies
, an d conclude d tha t ther e wa s n o significan t placental/feta l barrie r fo r lead
, wit h feta l bloo d lead value s bein g equa l t o o r jus t slightl y les s tha n materna l bloo d lea d values

. The mea n rati o o f feta l Pb B t o materna l Pb B i n thre e recen t studie s cite d b y Goye r wa s 0.90

. Base d o n this
, th e 95t h percentil e Pb B h i th e mothe r i s then : PbB^materna l = 10/0.9 0 = 11. 1 ug/dL

. Tha t is , ther e shoul d b e n o mor e tha n a 5 % chanc e tha t a pregnan t wome n wil l hav e a bloo d lea d valu e abov e 11. 1 ug/dL

. I t i s importan t t o not e tha t th e choic e o f 1 0 ug/d L a s th e uppe r 95t h percentil e limi t for th e fetu s doe s no t impl y tha t exposure s abov e thi s definitel y caus e unacceptabl e healt h effect s an d tha t level s belo w mi s ar e definitel y withou t risk

. Rather

, ther e i s a grade d increas e i n th e severit y o f advers e effect s a s bloo d lea d level s increase

. Typically

, frank clinica l effect s ar e no t observe d i n childre n a t bloo d lea d level s less tha n 60-8 0 ug/dL

, an d effect s tha t occu r a t bloo d level s o f abou t 1 0 ug/d L ar e subtl e an d ar e generall y observabl e onl y h i well-designe d populatio n studies

. Therefore

, ther e ar e difference s h i opinio n betwee n healt h professional s a s t o wha t bloo d lea d level shoul d b e treate d a s th e acceptabl e limit

. Th e choic e o f a healt h limi t o f 1 0 ug/d L b y EP A i s base d o n a consensu s amon g agenc y scientist s tha t effect s whic h begi n t o appea r a t thi s exposur e level are sufficientl y undesirabl e t o warran t avoidanc e (EP A 1991b)

. 2. 4 MEASURE D BLOO D LEA D VALUES I N WOME N I N LEADVILLE Dat a o n bloo d lea d level s i n 17 3 adult s h i Leadvill e wer e collecte d h i 199 1 b y Dr

. Rober t Bornschei n o f th e Universit y o f Cincinnati

. Withi n thi s grou p wer e 12 7 wome n o f child-bearin g ag e (assumed t o b e ag e 1 6 t o 4 5 years)

, 2 9 o f who m wer e pregnant an d 2 3 o f who m wer e
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. epa\48_32_9 0nursin

g a t th e tim e o f th e survey

. A summar y o f th e bloo d lea d value s observe d i n thes e wome n 

### i s presente d below

. Paramete r Numbe r o f peopl e Measure d Pb B Value s Mea n Standar d deviatio n Geometri c mea n (GM ) Geom

. Std.Dev

. (GSD ) Maximum Calculate d 95t h Percentil e Pb B A l

l Wome n Ag e 16-4 5 12 7
2. 7 ug/d L 1. 3 ug/d L 2. 4 ug/d L 1. 8 7. 1 ug/d L 6. 3 ug/d L N o t pregnan t
o r nursin g 7 5
2. 8 ug/d L 1. 3 ug/d L 2. 5 ug/d L 1. 7 6. 8 ug/d L 6. 1 ug/d L Pregnan t Wome n 2 9
2. 3 ug/d L 1. 3 ug/d L 1. 9 ug/d L 2. 1 7. 1 ug/d L 6. 4 ug/d L Nursin g Wome n 2 3
3. 1 ug/d L 1. 0 ug/d L 2. 9 ug/d L 1. 5 5. 3 ug/d L 5. 4 ug/d L Compariso n o f thes e dat a wit h the healt h goa l describe d abov e i n Sectio n 2. 3 (95t h percentil e Pb B = 1 1 ug/dL ) indicat e that
, a t th e populatio n level
, curren t wome n resident s o f Leadville

, includin g pregnan t an d nursin g women , ar e unlikel y t o b e expose d t o sufficien t level s o f lead t o b e o f concern
. Despit e th e indicatio n tha t curren t exposure s ar e belo w a level o f concern , ther e ar e limitation s t o thes e dat a an d th e result s shoul d b e interprete d wit h som e caution

. First

, ther e wer e a relativel y smal l numbe r o f wome n surveyed
, s o confidenc e i n th e populatio n statistic s (GM

, GSD

, 95t h percentile ) i s onl y moderate

. Fo r example
, th e 9 5 % confidenc e interva l fo r th e mea n bloo d lead i n pregnan t wome n i s approximatel y 1. 5 t o 3. 3 ug/dL

. Second

, informatio n i s no t availabl e o n whic h (i f any ) o f thes e wome n wer e expose d i n th e workplace
, s o i t i s difficul t t o utiliz e thes e observation s t o dra w direc t conclusion s regardin g th e acceptabilit y o f exposure s i n the workplace

. Third

, a s note d abov e (se e Sectio n 2.1)

, bloo d lea d dat a o f thi s sor t onl y indicat e exposures unde r curren t conditions
, an d ma y no t revea l risk s whic h coul d aris e i n th e future

. 2. 5 PREDICTE D BLOO D LEA D LEVEL S I N PREGNAN T WOME N Ther e ar e severa l mathematical model s whic h hav e bee n propose d fo r evaluatin g lea d exposur e i n adults
, includin g those develope d b y Bower s et al

. (1994)

, O'Flahert y (1993)

, Legge t (1993)

, an d th e Stat e o f Californi a (CEP A 1992)

. O f these
, th e mode l o f Bower s e t al

. i s mos t nearl y consistent wit h th e approac h employe d b y th e EP A i n th e IEUB K model fo r children
, an d i s als o ver y simpl e t o apply

. Fo r thes e reasons , thi s metho d wa s use d (wit h som e modifications ) fo r calculatin g th e concentratio n o f lea d i n soi l whic h woul d b e o f potentia l concer n t o adult s engage d i n recreationa l activities a t thi s site

.

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Basi c Equatio n Th e Bower s mode l predict s th e bloo d lea d level h i a n adul t expose d t o lea d h i a specifie d occupationa l settin g b y summin g th e "baseline " bloo d lea d level (PbB
0 ) (that whic h woul d occu r h i th e absenc e o f an y occupationa l exposures ) wit h th e incremen t h i bloo d lea d tha t i s expecte d
a s a resul t o f occupationa l exposur e t o soi l o r dust

. Th e latte r i s estimate d b y multiplyin g th e absorbe d dos e o f lea d fro m occupationa l soil/dus t exposure s b y a "biokineti c slop e factor " (BKSF)

. Thus

, th e basi c equatio n is : Pb B = PbB
0 + BKSF*[C

S *IR S *EF S *AF

S + C d *IR d *EF d *AF J (1 ) where : Pb B = Blood lea d leve l (ug/dL ) i n a populatio n o f adult s expose d t o lead

contaminated soi l o r dus t vi a occupational activitie s PbB
0 = "Baseline " bloo d lea d leve l h i adult s no t expose d t o lead-contaminate d soi l vi a occupationa l activities , bu t includin g other backgroun d exposures , includin g residentia l exposur e BKS F = Biokineti c slop e facto r (ug/d L increas e i n bloo d lea d pe r ug/da y lea d absorbed ) C = Arithmeti c mea n concentratio n (ug/g ) o f lea d i n soi l (C

s ) or dus t (C d )

, averaged ove r th e workplac e locatio n wher e exposur e occur s I R = Mea n dail y intak e rat e o f soi l (IRj ) o r dus t (IRj ) durin g occupationa l activitie s h i area s o f contaminatio n (g/day ) E F = Exposur e frequenc y (days/yr ) t o soi l (EF S ) o r dus t (EF d ) durin g occupationa l h i area s o f contaminatio n A F = Absolut e absorptio n fractio n (bioavailability ) o f lea d h i soi l (AF S ) o r dus t

2.5. 2 Inpu t Parameter s Mos t o f th e parameter s h i thi s mode l ar e no t constants , bu t var y fro m perso n t o perso n o r fro m plac e t o place

. Thus

, t o us e thi s mode l t o predic t the distributio n o f bloo d lea d value s tha t woul d b e observe d h i a populatio n o f wome n h i th e workplace
, i t i s necessar y t o describ e th e rang e an d relativ e likelihoo d o f value s fo r eac h parameter

. This i s don e h i th e for m o f Probabilit y Distributio n Function s (PDFs)

. Onc e PDF s ar e define d fo r eac h parameter , commerciall y availabl e softwar e system s ca n b e use d t o combin e th e input s an d predic t th e distributio n o f likel y bloo d lea d value s h i wome n workers

. Th e tex t belo w discusse s wha t i s know n abou t eac h parameter , an d th e PD F selecte d t o represent each

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. epa\48_32_9 0Backgroun

d Bloo d Lea d Leve l (PbB
9 ) A s discusse d above
, i t i s assume d th e subpopulatio n o f worker s o f greates t potentia l concer n for risk s fro m lea d ar e wome n o f child-bearin g age
. Tw o source s o f dat a ar e availabl e tha t coul d b e usefu l i n characterizin g PbB
0 fo r thi s subpopulation

. Firs t ar e the site-specifi c dat a collecte d durin g th e stud y performe d h i Leadvill e b y th e Universit y o f Cincinnat i i n 199 1 (Bornschei n 1994)

. A s note d above
, thi s stud y collecte d dat a fro m 12 6 wome n between th e age s o f 1 6 an d 45 , includin g a sub-se t o f 2 9 pregnan t women
. Th e G M value s fo r thes e tw o groups wer e 2. 4 ug/d L an d 1. 9 ug/dL

, respectively
, wit h GS D value s o f 1. 8 an d 2.1 , respectively

. A secon d sourc e o f informatio n o n baselin e bloo d lea d level s i s availabl e fro m th e NHANE S II I stud y (Brod y et al

. 1994)

. Th e geometri c mea n Pb B value s (ug/dL ) reporte d for wome n age d 20-4 9 wa s 1. 7 fo r whites
, 2. 0 fo r Hispanics

, an d 2. 2 fo r blacks
, eac h wit h GS D value s clos e t o 2.0

. Becaus e Leadvill e i s primaril y a mixture o f white s an d Hispanics

, thes e dat a sugges t tha t
a G M valu e o f abou t 1. 9 migh t b e expecte d fo r wome n i n Leadville

. Compariso n o f thi s valu e wit h thos e fro m th e Bornschei n stud y suggest s tha t wome n i n Leadvill e hav e bloo d lea d value s tha t ar e simila r t o nationa l averages , althoug h th e valu e o f 2. 4 ug/d L fo r wome n ag e 16-4 5 i s consisten t wit h th e vie w tha t level s i n Leadvill e wome n migh t b e abou t 0.4-0. 6 ug/d L highe r tha n th e nationa l average
. (I f so, thi s differenc e i s no t larg e enoug h t o b e o f toxicologica l significanc e i n th e averag e case)

. Base d o n th e combine d site-specifi c dat a o n bloo d lea d distribution s h i pregnan t wome n an d
wome n ag e 16-45 , an d supporte d b y th e dat a fro m th e nationa l survey , th e PD F selecte d t o mode l th e valu e o f PbB
0 i s a s follows : PbB
0 = LOGNORMAL(1.8,2.0

) BKS F Th e biokineti c slop e facto r propose d b y Bower s e t al

. i s 0.37 5 ug/d L pe r ug/da y absorbed

. Thi s valu e i s estimate d fro m a n observe d slop e o f 0.0 6 ug/d L increas e h i bloo d lea d o f adul t me n pe r ug/ L o f lea d i n firs t dra w water

. Calculatio n o f th e BKS F fro m th e Pococ k dat a require s a numbe r o f assumption s regardin g ho w muc h tota l wate r wa s Digested

, ho w muc h o f thi s wa s firs t dra w an d ho w muc h wa s draw n afte r th e pipe s wer e flushed
, th e decreas e i n lea d concentratio n whe n th e pipe s wer e flushed
, an d th e amoun t o f lea d absorbed fro m th e ingeste d water

. Appendi x A present s a n analysi s o f th e rang e o f possibl e BKS F value s whic h migh t b e derive d fro m th e Pococ k study
, dependin g o n th e inpu t assumptions

. Base d o n thi s analysis
, EP A believe s th e Pococ k stud y dat a ar e consisten t wit h a BKS F o f abou t 0. 4 ug/d L pe r ug/da y absorbed

. A simila r valu e o f 0.44 4 ca n b e derive d fro m th e dat a o f Rabinowit z e t al

. (1974)

, althoug h thi s stud y i s base d o n onl y tw o mal e individuals
, s o th e resultin g valu e ma y no t b e highl y representative

. Calculation s performe d usin g th e pharmacokineti c mode l develope d b y O'Flahert y (1993 ) sho w tha t BKS F i s no t a constant , bu t depend s on age, sex , and lea d bod y burden

. Estimate d value s rang e fro m 0.2 5 t o 0.5 3 fo r a 2 5 t o 3 5 year-ol d woman , assumin g a n absorptio n fractio n o f 0.0 8 (Gradien t 1995)

. Base d o n thi s information
, th e PD F selecte d t o mode l th e value o f BKS F i s a s follows :
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F = UNIFORM(0.25,0.50

) I t shoul d b e note d tha t thi s rang e o f BKS F value s i s stil l base d mainl y on dat a fro m adul t males

. However

, dat a fro m th e NHANE S i n surve y revea l tha t th e bloo d leve l o f men tend s t o b e higher tha n fo r wome n (Brod y e t al

. 1994)

. Thi s suggest s tha t either me n ten d t o hav e higher exposure s t o lead
, o r tha t th e BKS F fo r wome n i s lower tha n fo r men
. I t i s no t know n whic h
o f thes e i s true , bu t i f th e exposure s ar e though t t o b e similar
, the n us e o f a BKS F base d o n adul t male s ma y ten d t o b e conservative whe n applie d t o women
. C

. an d C

. Dat a ar e availabl e fro m a numbe r o f studie s o n th e distributio n o f lea d value s h i soil s i n th e communit y o f Leadville

. Thes e dat a revea l tha t averag e lea d concentration s var y a s a functio n o f locatio n withi n th e community , tendin g t o b e highes t h i th e easter n section s o f tow n wher e mos t o f th e histori c mining-relate d activitie s occurred

. However

, fo r th e purpose s o f simulatin g th e expecte d distributio n o f bloo d lea d value s h i curren t wome n residents
, th e mos t appropriat e dat a ar e fo r th e communit y a s a whole

. Statistic s availabl e fro m severa l majo r studie s ar e summarize d below

. Stud y Wals h 198 8 WESTO N 199 1 Bornschei n 199 4 CO M 199 4 Sampl

e Typ e Dept h = 0-6 " Dept h = 0-6 " Perimete r Bar e Are a Dept h = 0-6 " N 35 4 348 9 20 2 17 4 276 2 Mea n 189 0 232 0 152 0 151 0 190 0 S T D 3220 226 0 245 0 229 0 320 0 I n al l o f thes e studies
, th e dat a ar e observe d t o b e left-skewe d i n a n approximatel y lognorma l distribution

. Base d o n thes e studies
, th e variabilit y h i C

s wa s estimate d wit h th e followin g PDF : C

s = LOGNORMAL(2000,2500

) Onl y on e stud y (Bornschei n 1994 ) ha s investigate d th e distributio n o f lea d level s h i 24 3 interio r dus t sample s i n Leadville

. Thes e dat a wer e collecte d i n privat e residences
, bu t i t seem s reasonabl e t o assum e tha t level s h i commercia l establishment s ar e likel y t o b e similar

. Th e observe d mea n an d standar d deviatio n o f th e dus t value s wer e 85 0 pp m an d 70 0 ppm , respectively

. A s wa s th e cas e fo r soils
, th e dat a ar e observe d t o b e left-skewe d i n a n approximatel y lognorma l distribution

. Base d o n this
, the valu e o f C d wa s modele d as : C d = LOGNORMAL(850,700

)

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. epa\48_32_9 0J R

s _andJR d The parameter s IR j an d IR j ar e the averag e dail y intak e o f soi l an d dust durin g occupationa l exposures

. Such intak e i s believe d t o occu r mainl y a s a resul t o f soi l o r dus t adherenc e t o th e hands
, followe d b y hand-to-mout h contact

. I t i s expecte d tha t th e amoun t o f soi l an d dus t ingeste d b y worker s i s highl y variable
, dependin g o n parameter s suc h as : • Th e typ e o f business
, an d whether o r no t worker s a t th e busines s frequentl y com e int o direc t contac t wit h soil

. EP A refer s t o suc h businesse s a s "contact

intensive" , whil e occupation s suc h a s offic e worker
, teacher
, storekeeper
, etc. , ar e considere d "non-contac t intensive"

. • Th e amoun t o f soi l or dust availabl e for adherenc e t o th e hand

. For indoo r exposures , thi s i s probabl y relate d t o th e dus t "loading " o n surface s whic h
com e int o contac t wit h th e hands

. Fo r outdoo r exposure , i t i s probabl y relate d t o th e amoun t o f soi l tha t i s availabl e fo r direc t contac t (i.e.

, no t covere d wit h pavemen t o r vegetation)

. • Th e tendenc y o f soi l o r dus t t o adher e t o th e hand

. This

, i n turn , probabl y depend s o n th e particl e siz e an d moistur e conten t o f th e soi l o r dust
, an d possibl y th e amoun t o f moistur e o n th e han d a s wel l

• The frequenc y o f hand-t o mout h contac t b y worker s followin g contac t wit h contaminate d dus t o r soi l Base d o n informatio n provide d b y th e Leadvill e Chambe r o f Commerce

, mos t businesse s i n Leadvill e fal l int o th e "non-contac t intensive " category

. Thi s include s 6 5 retai l stores , 2 1 offic e buildings
, 2 2 restaurants , 1 3 motels/hotels

, an d 4 6 service-typ e businesses

. O f th e relativel y fe w "outdoo r businesses " (lumberyard

, ga s stations , yar d maintenance service , etc)

, man y hav e pave d parkin g o r workin g areas , an d ar e no t likel y t o involv e extensiv e an d repeate d contac t wit h soil

. Ther e ar e relativel y fe w studie s o n th e amoun t o f soi l an d dust ingestio n b y adults
, an d ther e ar e n o direc t measurement s o f soil/dus t ingestio n durin g non-contac t intensiv e occupationa l activities

. Thus

, ther e i s ver y hig h uncertaint y associate d wit h selectio n o f thes e parameters

. T o addres s thi s uncertainty , th e EP A (1993 ) ha s issue d draf t guidanc e on recommende d defaul t soi l an d dust intak e b y non-contac t intensive workers
, a s follows : Centra l tendenc y = 5 0 mg/da y Reasonabl e maximu m = 10 0 mg/da y Thes e recommendation s ar e adopte d fo r us e i n thi s assessment , an d ar e expresse d a s a PD F a s follows :

= TRIANGULAR(10,30,120

)

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. epa\48_32_9 0Thi s

PD F ha s a mea n o f approximatel y 5 0 mg/da y an d a 95t h percentil e o f approximatel y 10 0 mg/day

, consisten t wit h EP A recommendations

. E F

, an d EF d Ther e ar e n o site-specifi c dat a o n th e numbe r o f day s eac h yea r a worke r i s a t work
, bu t draf t EP A guidanc e (EP A 1993 ) recommend s a n assume d centra l tendenc y exposur e frequenc y a t th e workplac e o f 21 9 day s pe r yea r an d a n RM E valu e o f 25 0 day s pe r year
. Assumin g a lowe r boun d o f 20 0 days/yr

, th e tota l numbe r o f day s a t wor k i s modele d as : EFfct f = TRIANGULAR(200,219,250

) A s note d above
, mos t businesse s i n Leadvill e ar e no t soil-contac t intensive , s o mos t exposur e i s expecte d t o b e associate d wit h dus t ingestio n whil e indoor s a t th e workplace

. However

, som e worker s ma y spen d som e days
, o r part s o f som e day s outside

. Ther e ar e n o dat a o n th e amoun t o f tim e spent outdoor s b y worker s i n Leadville

, bu t becaus e ther e ar e ove r 15 0 days/yea r whe n th e groun d i s eithe r froze n o r snow-covered
, i t i s expecte d tha t th e maximu m numbe r o f wor k day s whe n soi l exposur e coul d occu r i s probabl y no t highe r tha n 10 0 days/yr

, wit h a n averag e valu e o f approximatel y 1 0 days/yr

. Base d o n thes e concepts , th e indoo r (dust ) an d outdoo r (soil ) exposur e frequencie s fo r worker s ar e modele d wit h th e followin g PDFs : E F S = TRIANGULAR(0,10,100

) E F d = EF
tota i - EF S A F T an d "Baseline " Absorptio n Fraction

. A numbe r o f studie s hav e bee n publishe d o n th e absorptio n o f lea d b y adults

. I n a stud y wit h 5 adul t mal e volunteers
, Rabinowit z et al

. (1980 ) foun d tha t th e absorptio n fractio n depende d o n whethe r th e lea d wa s ingeste d alon g wit h foo d o r wa s ingeste d 9 hour s afte r th e las t meal

. Fo r lea d ingeste d alon g wit h foo d (o r fo r lea d ingeste d i n the diet)

, the absorptio n fractio n wa s 8-10%

. Fo r lead ingeste d b y 9-h r faste d subjects
, the absorptio n fractio n wa s 30-37%

. (N o foo d wa s ingeste d b y thes e subject s unti l hou r 16)

. O'Flahert y (1993 ) reviewe d severa l report s (includin g Rabinowit z e t al

. 1980 ) an d conclude d tha t gastrointestina l absorptio n o f lea d i n adult s ingestin g mixe d diet s i s 4-11%
, wit h a mea n probabl y abou t 8-9%

. Clearl y th e choic e o f th e mos t appropriat e absorptio n fractio n depend s o n wha t i s assume d regardin g th e tim e o f lea d ingestio n i n relatio n t o th e tun e o f las t eating

. Fo r workers
, i t seem s reasonabl e t o assum e tha t mos t wil l arriv e a t wor k shortl y afte r havin g breakfast
, an d wil l als o ingest foo d a t lunc h time

. Likewise

, i t seem s reasonabl e t o expec t tha t mos t recreational visitors wil l hav e eate n withi n severa l hour s o f visitin g th e site

. Thus

, EP A consider s a valu e o f 10 % likel y t o b e representativ e th e absorptio n fractio n i n mos t people
, bu t individual s wh o d o no t ea t breakfas t o r lunch
, o r wh o otherwis e ar e expose d a numbe r o f hour s afte r th e las t meal
, migh t hav e a n absorptio n fractio n a s hig h a s 30%

. Base d o n this
, th e PD F selecte d t o mode l th e baselin e absorptio n fractio n (AF
0 ) i n worker s i s a s follows :
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. epa\48_32_9 0A F
0 = TRIANGULAR(0.04,0.10,0.30

) Effec t o f Pregnancy

. Severa l studie s hav e establishe d tha t calciu m absorptio n increase s abou t two-fol d i n wome n durin g pregnanc y (e.g.

, Heane y an d Skillma n 1971)

. Becaus e a t leas t som e lea d absorptio n fro m th e gastrointestina l trac t probabl y occur s vi a calciu m transpor t systems , i t i s quit e plausibl e tha t durin g pregnanc y th e absorptio n o f lea d als o increases, an d ther e ar e scattere d observation s fro m recen t studie s whic h provid e partia l suppor t fo r thi s conclusio n (Rothenber g e t al

. 1994 , Manto n an d Angl e 1995 , Frankli n e t al

. 1995)

. However

, bot h th e site-specifi c dat a an d dat a fro m othe r studies (e.g.

, Alexande r an d Delves

, 1981 ) sho w tha t bloo d lea d value s d o no t increas e two-fol d durin g pregnancy , an d ma y eve n decrease

. Thi s support s th e vie w tha t th e absorptio n fractio n fo r lea d doe s no t increas e (a t leas t no t a s muc h a s fo r calcium)

, o r tha t othe r change s i n distributio n an d clearanc e kinetic s occur
. Base d o n thi s information
, i t i s assume d tha t th e absorptio n fractio n durin g pregnanc y i s abou t 1.5-time s tha t i n non-pregnan t women : A F
0 (pregnancy ) = 1.5*AF
0 A s note d above
, becaus e observe d bloo d lea d value s d o no t usuall y increas e b y thi s larg e a facto r durin g pregnancy , inclusio n o f thi s adjustmen t withou t a compensator y adjustmen t i n th e BKS F ter m i s mor e likel y t o overestimat e tha n underestimat e bloo d lea d value s durin g pregnancy

. Adjustmen t fo r Unavailabilit y i n Mine Wastes

. Ther e ar e severa l studie s whic h provid e evidenc e tha t lea d i n soi l an d min e waste s ma y b e absorbed less-extensivel y tha n lea d i n foo d
o r water

. Thi s include s a stud y performe d b y th e EP A i n whic h absorptio n o f lea d fro m a composit e soi l sampl e fro m Leadvill e wa s measure d i n immatur e swine

. Base d o n preliminar y analyse s o f th e dat a fro m thi s stud y (EP A 1995)

, i t appear s tha t lea d i n th e Leadvill e soi l wa s absorbe d abou t 60-80 % a s muc h a s wa s a know n solubl e for m o f lea d (lea d acetate)

. Thus

, i t i s reasonabl e t o expec t tha t th e amoun t o f lea d absorbe d fro m ingeste d soi l woul d b e abou t 60

- 80 % o f th e "default " valu e fo r lea d absorptio n b y pregnan t women
. I n orde r t o b e consisten t wit h th e curren t assumptio n regardin g absorptio n o f lea d fro m soi l tha t i s use d i n th e IEUB K model (EP A 1994a)

, a relativ e bioavailabilit y o f 60 % wa s assume d for thes e calculations

. Dat a ar e no t availabl e o n ho w RB A migh t var y fro m locatio n t o locatio n acros s th e site , bu t speciatio n studie s indicat e tha t ther e are difference s i n th e relativ e abundanc e o f differen t form s o f lea d i n differen t locations

. I n th e absenc e o f data
, i t i s assume d tha t RBA coul d var y fro m abou t 30 % t o 80%
, an d i s modele d a s follows : RB A = TRIANGULAR(0.3,0.6,0.8

) Th e ne t absorptio n fractio n fo r lea d h i soi l o r dus t i s give n by : A F S d (pregnancy ) = AF
0 (pregnancy)*RB A

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. epa\48_3 2 9 0Summar

y o f Input s Tabl e 1 list s th e PDF s selecte d t o mode l th e variabilit y i n eac h o f th e input s neede d t o estimat e bloo d lea d level s i n th e populatio n o f pregnan t wome n wh o wor k i n Leadville

. 2.5. 3 Result s Mont e Carl o simulation s wer e performe d (5000 iteration s pe r simulation ) usin g th e PDF s abov e t o describ e th e variabilit y i n bloo d lea d value s predicte d i n wome n h i Leadvill e a s a resul t o f workplac e exposur e t o environmenta l lead

. Th e result s ar e summarize d below

.
Parameter Geometri c Mean Averag e 95t h Percentil e G S D Calculate d

Value s fo r Pregnan t Worker s 3. 3 3. 9 8. 7 1. 8 Measure d

Value s Wome n (16-45 ) 2. 4 2. 9 6. 3 1. 8 Pregnan

t Wome n 1. 9 2. 3 6. 4 2. 1 A s shown
, the predicte d population-base d bloo d lea d distributio n fo r pregnan t worker s i n Leadvill e i s withi n th e health-base d goa l describe d h i Sectio n 2. 1 (95t h percentil e < 1 1 ug/dL)

, supportin g th e conclusio n tha t curren t environmenta l exposur e level s i n Leadvill e ar e no t likel y t o b e o f concer n t o pregnan t women
. Compariso n o f th e calculate d value s wit h th e value s reporte d b y Bornschei n revea l tha t th e calculate d value s are highe r tha n th e measure d values

. Thi s observatio n i s consisten t wit h tw o interpretation s (whic h ar e no t mutuall y exclusive) : • Th e wome n wh o participate d i n th e stud y wer e no t expose d i n th e workplac e
• On e o r mor e o f th e PDF s selecte d fo r us e i n th e simulation s ten d t o overestimat e curren t exposur e level s i n th e workplac e

2 . 6 CALCULATIO

N O F WORKPLAC E SOI L ACTIO N LEVEL S FO R LEA D

2.6. 1 Overvie w Eve n thoug h bot h th e measure d an d th e predicte d bloo d lea d distribution s i n th e populatio n o f

wome n i n Leadvill e indicat e tha t th e risk s o f unacceptabl e exposur e t o lea d ar e low
, i t i s stil l
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. epa\48_32_9 0TABL

E 1

. SUMMAR Y O F VARIABILIT Y DISTRIBUTIO N FUNCTION S F O R ESTIMATIO N O F LEA D EXPOSUR E I N WORKER S
Mode l Inpu t Baseline bloo d lea d Biokineti c slop e facto r Concentratio n i n soi l Concentratio n i n dust Ingestio n rat e o f soi l an d dus t a t workplac e Exposur e frequenc y a t wor k Exposur e frequenc y outdoor s Exposur e frequenc y indoor s Absorptio n fractio n fro m foo d an d wate r durin g pregnanc y Relativ e bioavailabilit y o f lea d i n soi l Abbr

. PbB
0 BKS F



## c s 

## c d 

## iRs d

F F E r tota l E F S E F d A F pre g RB A Unit s ug/d L ug/d L pe r ug/ d mg/k g mg/k g mg/da y days/y r days/y r days/y r

—

~"

~ Distributio n Shap e Lognormal Unifor m Lognorma l Lognorma l Triangula r Triangula r Triangula r Calculate d a s EF ^ - EF S Triangula r Triangula r Parameter

s o f Distributio n G M = 1. 8 GS D = 2. 0 Mi n = 0.2 5 Ma x = 0.5 0 Mea n = 200 0 S T D = 250 0 Mea n = 85 0 ST D = 70 0 Mi n = 1 0 Mod e = 3 0 Ma x = 12 0 Mi n = 20 0 Mod e = 21 9 Ma x = 25 0 Mi n = 0 Mod e = 1 0 Ma x = 10 0

— Mi n = 0.0 6 Mod e = 0.1 5 Ma x = 0.4 5 Mi n = 0. 3 Mod e = 0. 6 Ma x = 0. 8

Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48_32_9 0possibl

e tha t ther e ar e sub-location s withi n th e communit y wher e th e concentration s o f lead ar e sufficientl y hig h t o pos e a ris k t o individual s expose d a t thos e locations
, no w o r i n th e future

. I f suc h location s exist , the y migh t no t hav e bee n detecte d b y eithe r th e measuremen t o f bloo d lea d o r th e calculatio n o f predicte d value s i f a ) n o wome n ar e currentl y expose d a t thos e areas , b ) wome n ar e exposed
, bu t th e area s ar e relativel y smal l compare d t o communit y a s a whole
, o r c ) if
, b y chance
, n o wome n wit h highe r tha n averag e intake s o f soi l o r dus t wer e expose d h i thes e areas

. On e wa y t o estimat e th e maximu m soi l concentratio n a t som e specifie d workplac e o r recreationa l
are a tha t i s no t o f concer n t o pregnant worker s o r recreationa l visitor s i s t o fin d th e soi l concentratio n tha t give s a 95t h percentil e Pb B valu e o f 1 1 ug/dL

. Th e step s needed t o achiev e thi s solutio n ar e discusse d below

. 2.6. 2 Basi c Equatio n Recal l tha t th e basi c equatio n use d t o predic t bloo d lea d i n a n expose d individua l is : P b B = PbB
0 + BKSF*[C

S *IR S *EF S *AF

S + C/IR/EF/AF J (1

) Becaus e thi s equatio n contain s term s fo r bot h soi l an d dus t exposure , i t canno t b e solve d fo r th e soi l ter m (C

s ) unless th e dus t ter m (C<, ) i s define d a s a dependen t variabl e whos e valu e ca n b e predicte d fro m the valu e o f soil

. Assumin g tha t soi l comprises som e (bu t not all ) o f the mas s o f indoo r dust
, th e concentratio n o f lea d h i dus t ca n b e describe d usin g a n equatio n o f th e followin g form : C d = D
0 + Ksd*C

s where : D
0 = Concentratio n o f lea d i n dust tha t i s no t du e t o contaminatio n fro m soi l a t th e workplac e Ks d = Mass fractio n o f dus t tha t come s fro m outdoo r soi l a t the workplac e Substitutin g thi s expressio n int o th e basi c equatio n abov e an d solvin g fo r th e valu e o f C

s whic h correspond s t o som e specifie d targe t bloo d lead valu e yields : C

s = ( a - c*D
0)/( b + c*Ksd ) where :

a = (PbB^e t - PbB
0 )/BKS F b = IR S *EF S *AF

S c = IR d *EF d *AF

d

Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfim d Sit e — Par t C

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Uncertaint y PDF s Th e desire d valu e fo r eac h o f th e inpu t parameter s abov e i s th e tru e mean
. I f thes e tru e mean s wer e known
, the n th e equatio n woul d yiel d a singl e numeri c valu e (the action level ) tha t i s equa l t o th e soi l lea d concentratio n correspondin g t o a 5 % chanc e tha t an y woma n expose d a t tha t workplac e woul d hav e a bloo d lea d valu e abov e 1 1 ug/dL

. However

, ther e i s substantia l uncertaint y i n th e tru e mea n fo r mos t o f thes e variables

. Therefore

, eac h inpu t paramete r wa s describe d b y a PD F whic h describe s uncertaint y abou t th e tru e mean , an d thes e PDF s wer e use d i n a Mont e Carl o simulatio n t o estimat e th e plausibl e rang e o f th e tru e actio n level

. I t i s importan t t o distinguis h thi s analysi s o f uncertaint y aroun d the tru e actio n leve l fro m the analysi s o f variabilit y i n communit y bloo d lea d level s presente d abov e i n Sectio n 2.5

. Targe t Bloo d Lea d Leve l A s discusse d earlier
, EP A ha s chose n 11. 1 ug/d L a s the uppe r 95t h percentil e o f the acceptabl e bloo d lea d distributio n i n expose d women
. This valu e ca n b e use d t o estimat e th e geometri c mea n o f th e bloo d lea d distributio n i f th e GS D i s known
, usin g th e followin g equation: : PbB G M targe t = 11.1/GSD; 164 5 (3 ) Th e GSD

, i n thi s equation i s intende d t o describ e th e individua l variabilit y between differen t peopl e i n th e amoun t o f environmenta l medi a whic h the y ingest , i n th e fractio n o f th e lea d whic h the y absor b fro m thos e media
, an d i n th e incremen t whic h tha t absorbed lead cause s o n thei r averag e Pb B value

. Normally

, value s o f GSD ; ar e estimate d fro m observe d distribution s o f Pb B value s i n a population

. The observe d GS D fro m the populatio n i s referre d t o a s GSD P . A t thi s site , th e measure d GSD p valu e h i wome n ag e 18-4 0 wa s 1. 7 ( N = 66)

, an d i n pregnan t wome n wa s 2. 1 ( N = 29)

. T h e relationshi p betwee n GSD p an d GSD ( i s usuall y difficul t t o resolve

. Conceptually

, a GSD p valu e reflect s variabilit y o f tw o mai n types : 1 ) variabilit y hi individua l activit y pattern s and toxicokineti c factors
, an d 2 ) variabilit y h i th e concentration s o f lea d i n environmenta l media

. Th e firs t componen t i s equa l t o GSDj

. Thus

, empirica l GSD p s represent a n uppe r boun d o n th e valu e o f GSD
t . EP A ha s describe d a genera l metho d fo r estimatin g GSD

S fro m a dat a se t b y stratifyin g the populatio n int o group s wit h similar environmenta l exposur e level s (EP A 1994a)

. This stratificatio n tend s t o reduc e th e contributio n du e t o environmenta l variation , an d th e valu e o f GSD p wil l ten d t o approac h GSDi

. Th e result s o f thi s approac h usin g th e site-specifi c dat a fo r wome n o f child-bearin g age a t thi s sit e yield s th e followin g results :

Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Super-fun d Sit e — Par t C

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. epa\48_32_9 0Are

a A B C D E F G H N

8 7 2 1 1 2 3 2 4 2 G S D 2. 0 1. 5 1. 8 1. 5 1. 5 1. 4 1. 4 1. 2 Interpretin g thes e sub-populatio n GSD

p value s a s GSD ; value s i s complicate d because exposure s i n sub-area s ma y no t reall y b e unifor m (thi s i s o f specia l likelihoo d i n Leadville)

, an d becaus e th e valu e tend s t o becom e statisticall y unstabl e a s th e numbe r o f peopl e i n th e subpopulatio n become s small

. Nevertheless

, th e analysi s b y subarea s generall y support s th e conclusio n tha t th e GSD
t i s probabl y lowe r tha n th e population-base d valu e o f 1.7

. Base d o n thes e considerations
, th e PD F selecte d t o describ e th e rang e o f possibl e tru e mea n value s fo r GSD S is : GSD ; = TRIANGULAR(1.4,1.6,1.8

) Baseline Bloo d Lea d (PbB

n ) A s discusse d above
, sit e specifi c dat a identif y a geometri c bloo d lead valu e o f 2. 5 fo r wome n o f child-bearin g ag e an d 1. 8 fo r pregnan t wome n i n Leadvill e (Bornschei n 1994)

. Compariso n o f thes e value s wit h th e nationa l mea n o f abou t 2. 0 fo r wome n ag e 20-4 0 suggest s tha t wome n h i Leadvill e ma y hav e bloo d lea d value s tha t ar e perhap s abou t 0.5-0. 6 ug/d L highe r tha n th e nationa l average
. I f so , thi s i s mos t likel y du e t o th e higher-than-average

exposur e t o lea d h i th e hom e o r h i th e genera l community

. T o th e exten t tha t th e measure d G M bloo d lea d value doe s includ e contribution s fro m th e environmen t tha t wil l b e addresse d a s par t o f th e residentia l ris k assessment , i t i s no t appropriat e t o includ e thi s contributio n h i th e derivatio n o f th e PR G fo r recreationa l areas

. I n essence, thi s woul d requir e thes e area s t o mee t a mor e stringen t goa l t o accoun t fo r th e exposure s occurrin g h i othe r areas

. Base d o n thes e considerations
, th e PD F selecte d t o describ e th e rang e o f plausibl e value s for th e tru e G M PbB
0 is : PbB
0 = TRIANGULAR(1.7,2.0,2.5

) Soil/Dus t Relationshi p (D n an d Ksd ) Th e norma l EP A defaul t assumptio n i s tha t th e concentratio n o f contaminant s i n indoo r dus t ar e equa l t o thos e h i outdoo r soi l (EP A 1989 , 1994a)

. However

, thi s assumptio n ha s prove d t o b e overl y conservativ e a t mos t minin g sites

. A t Leadville

, th e Universit y o f Cincinnat i obtaine d
Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulch Superfun d Sit e — Par t C

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. epa\48_32_9 0paire d

measurement s o f lea d concentration s i n soi l an d dus t a t abou t 20 0 location s (Bornschei n 1994)

. Base d o n simpl e mass-fractio n considerations
, th e contributio n o f soi l t o dus t ca n b e describe d b y a n equation o f th e form : C d = D
0 + K^C

, where : D
0 = Concentratio n o f lea d i n dus t du e t o source s othe r tha n yar d soi l

= Mas s fractio n o f yar d soi l i n indoo r dus t Findin g th e best-fi t value s fo r thes e tw o parameter s (D
0 , K ^ i s complicate d b y th e effec t o f measuremen t error , whic h tend s t o obscur e an y relationship s whic h d o exist

. A s discusse d i n Par t A o f thi s ris k assessment , one approac h tha t i s fairl y insensitiv e t o th e effect s o f
measuremen t erro r i s t o estimat e D
0 a s th e mea n dust concentratio n i n location s wher e th e concentratio n h i outdoo r soi l i s lo w (e.g.

, les s tha n 30 0 ppm)

, an d t o estimat e K ^ as : 

### .IP-".

where : D = Averag e concentratio n o f lea d i n dust S = Averag e concentratio n o f lea d i n soi l Base d o n thi s analysis
, th e estimate d value s are : D O = 50 0 pp m

= 0.2 6 Becaus e D
0 reflect s the contributio n o f source s outsid e the boundarie s o f a propert y t o contaminatio n o f dust a t tha t property , EP A doe s no t conside r i t appropriat e t o includ e thi s ter m whe n calculatin g a n actio n level

. I n essence, thi s woul d penaliz e a propert y an d requir e a mor e stringent clean-u p tha n i f adjacen t area s wer e not contaminated

. Therefore

, fo r the purpose s o f thi s calculation
, D
0 i s se t t o zero
. Becaus e o f th e relativel y hig h uncertaint y i n th e calculate d valu e fo r K^

, thi s paramete r wa s describe d wit h th e followin g PDF :

= TRIANGULAR(0.2,0.25,0.6

) Othe r Parameter s Al l o f th e othe r parameter s neede d t o calculat e th e nomina l actio n level for lead i n workplac e soi l ar e th e tru e mean s fro m th e variabilit y distribution s discusse d i n Sectio n 2. 5 above

. Professiona l judgemen t wa s use d t o select PDF s tha t describ e th e rang e o f plausibl e value s fo r th e true s means , a s summarize d h i Tabl e 2

. Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfiux l Sit e — Par t C

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. epa\48_32_9 0TABL

E 2

. SUMMAR Y O F UNCERTAINT Y DISTRIBUTIO N FUNCTION S F O R ESTIMATIO N O F LEA D SOI L ACTIO N LEVE L Mode l Inpu t Individua l geometri c standar d deviatio n Baseline bloo d lea d Biokineti c slop e facto r Ingestio n rat e o f soi l an d dus t Exposur e frequenc y a t wor k Exposur e frequenc y outdoor s Exposur e frequenc y indoor s Absorptio n fractio n fro m foo d an d wate r durin g pregnanc y Relativ e bioavailabilit y o f lea d i n soi l Mas s fractio n o f yar d soi l i n dus t Abbr

.

GSD ; PbB
0 BKS F IRs d
EF ^ E F S E F d A F pre g RB A K s d Unit s

— ug/d L ug/d L pe r ug/ d mg/da y days/y r days/y r days/y r

—

—

— Distributio n Shap e Triangula r Triangula r Unifor m Unifor m Unifor m Triangula r Calculate d a s EFtota i " EF S Triangula r Unifor m Triangula r Parameter

s o f Distributio n Mi n = 1. 4 Mod e = 1. 6 Ma x = 1. 8 Mi n = 1. 7 Mod e = 2. 0 Ma x = 2. 5 Mi n = 0. 3 Ma x = 0. 5 Mi n = 1 0 Ma x = 9 0 Mi n = 21 0 Ma x = 23 0 Mi n = 5 Mod e = 1 0 Ma x = 2 0

— Mi n = 0. 1 Mod e = 0.1 5 Ma x = 0. 4 Mi n = 0. 4 Ma x = 0. 8 Mi n = 0. 2 Mod e = 0.2 5 Ma x = 0. 6

Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e - Par t C

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Result s Th e result s o f a Mont e Carl o simulatio n o f th e uncertaint y aroun d th e actio n leve l ar e show n i n Figur e 1

. A s seen , th e plausibl e rang e o f actio n level s coul d conceivabl y rang e fro m a s lo w a s 2,20 0 ppm (th e 5t h percentile ) t o a s hig h a s 19,10 0 ppm (the 95t h percentile)

. Centra l tendenc y value s includ e 6,10 0 ppm (the geometri c mean ) and 7,70 0 ppm (the arithmeti c mean)

. 2.6. 5 Compariso n o f Actio n Level s wit h Measure d Concentration s Numerou s studie s hav e bee n performe d t o collec t dat a o n lea d level s h i soi l i n an d aroun d Leadville

. Figur e 2 i s a ma p take n fro m CD M (1994)

, whic h show s lead level s i n surficia l soil s (0- 1 inch ) h i an d aroun d Leadville

. Thes e result s ar e simila r t o thos e describe d i n WESTO N (1994 ) (e.g.

, se e Figur e 5- 4 h i tha t report)

, whic h show s lea d level s h i th e 0- 6 inc h laye r o f soi l h i an d aroun d Leadville

. Inspectio n o f thes e map s reveal s tha t averag e lead level s ar e mostl y belo w th e central-tendenc y rang e o f plausibl e action level s (6100-770 0 ppm ) fo r mos t area s zone d for commercia l lan d use , excep t possibl y for som e area s locate d h i th e histori c minin g are a eas t o f tow n an d h i th e vicinit y o f th e forme r A V Smelte r locate d southwes t o f town

. Not e tha t i t i s averag e lea d level s ove r a n are a whic h shoul d b e compare d t o th e soi l actio n level

. Tha t is , occasiona l measurement s or smal l "hot-spots " o f concentration s abov e th e actio n leve l d o no t necessaril y constitut e evidenc e tha t a n are a i s unsafe

. 2.6. 6 Sensitivit y Analysi s Appendi x B present s a sensitivit y analysi s o f th e Bower s mode l a s i t i s use d t o calculat e a n actio n leve l fo r lead

. I n brief
, the mos t importan t parameters , judge d hi term s o f ho w muc h the calculate d valu e ma y var y a s a functio n o f th e rang e o f plausibl e inpu t values
, ar e th e targe t bloo d lead level
, th e soil/dus t ingestio n rate, th e absorptio n fractio n fro m foo d an d water , an d th e mas s fractio n o f soi l h i indoor dust

. Th e sensitivit y t o thes e parameter s i s du e mainl y t o th e larg e uncertaint y (credibl e range ) aroun d thes e parameters

. 2 . 7 WEIGHT-OF-EVEDENCE

EVALUATIO

N Thre e type s o f informatio n are availabl e t o evaluat e th e risk s t o wome n o f exposur e t o environmenta l lea d contaminatio n h i th e workplace

. 1 ) Direc t Bloo d Lea d Measurement s h i Wome n Direc t bloo d lea d measurement s o f wome n h i Leadvill e indicat e that
, unde r curren t conditions
, ther e i s a lo w probabilit y tha t o f a woma n wil l hav e a bloo d lea d leve l highe r tha n th e goa l se t b y EPA

. Base d o n th e expectatio n tha t a numbe r o f thes e wome n d o work
, thi s observatio n support s th e vie w tha t curren t workplac e exposure s t o lea d ar e no t o f concern
. However

, direct measuremen t technique s migh t no t detec t th e occurrenc e o f a fe w specifi c locations wher e risk s ar e high
, an d thes e dat a ma y no t reflec t risk s whic h coul d occu r i n th e future

.
Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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Baselin e Huma n Healt h Ris k Assessmen t fo r th e Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48_32_9 0 Apri l 199 5 Page-2 2 I T SHAL L NO T B E RELEASE D O R DISCLOSE D I N2 ) Predicte d Bloo d Lea d Distributio n i n Workin g Women Us e o f a mathematica l mode l t o predic t th e rang e o f bloo d lea d value s tha t coul d occu r i n workin g women , no w o r i n th e future
, als o support s th e vie w tha t ther e i s a lo w probabilit y that
, a t th e populatio n level
, wome n woul d b e expose d t o sufficien t environmenta l lead h i th e workplac e t o excee d EPA' s health-base d goal

. However

, th e prediction s o f thi s mode l ar e considere d t o b e uncertain , bot h becaus e th e basi c model ma y b e a n oversimplificatio n o f lea d exposur e an d pharmacokinetics h i pregnan t women , an d becaus e o f substantia l uncertaint y i n man y o f the inpu t parameters

. I n addition
, thi s population-base d approac h doe s not identif y the rang e o f risk s whic h migh t occu r a t specifi c workplaces

. 3 ) Calculate d Actio n Level s Eve n i f ther e i s lo w ris k a t th e populatio n level
, i t ma y stil l b e possibl e fo r location s t o exis t wher e risk s t o individual s a t thos e location s coul d b e o f concern
. Calculation s o f th e concentratio n o f lea d hi soi l tha t i s likel y t o ensur e EPA' s bloo d lea d goa l i s not exceede d indicates tha t concentration s h i th e rang e o f 610 0 t o 770 0 pp m ar e likel y t o b e protectiv e wit h
a reasonabl e degre e o f confidence

. Revie w o f availabl e dat a o n lea d concentration s h i soi l sugges t tha t ther e ar e fe w curren t workplace s wher e th e mea n concentration s ar e likel y t o excee d thi s rang e o f actio n levels
, althoug h ther e ar e som e location s zone d fo r possibl e futur e commercia l developmen t wher e thi s rang e o f actio n level s migh t b e exceeded

. A s note d above
, ther e i s substantia l uncertaint y i n th e us e o f a mathematica l model t o calculat e actio n levels

. Weight-o f Evidenc e Evaluatio n Althoug h al l thre e o f thes e line s o f analysi s hav e significan t limitation s an d uncertainties , al l thre e yiel d generall y consisten t results
, an d al l suppor t th e conclusio n tha t curren t workplac e exposure s t o environmenta l lea d ar e unlikel y t o b e o f significan t concer n t o workin g women
. Futur e workplac e exposure s migh t b e o f concer n h i area s wher e soi l concentration s substantiall y excee d th e rang e o f plausibl e actio n level s fo r lead

.

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ARSENI C EVALUATIO N N o site-specifi c dat a ar e availabl e o n th e leve l o f arseni c exposur e fo r citizen s o f Leadville

. I n th e absenc e o f reliabl e biomarker s o f exposure , th e leve l o f exposur e an d ris k t o worker s mus t b e predicte d fro m measure d level s o f arseni c i n the environment

. The followin g section s describ e th e estimate d rang e o f risk s fro m arseni c whic h migh t occu r i n workers
, an d th e rang e o f soi l concentration s tha t ar e plausibl e action level s fo r individua l workplaces

. 3 . 1 PREDICTE D ARSENI C RISK S I N LEADVILL E WORKER S

3.1. 1 Basi c Equation s Th e basi c equation s recommende d b y EP A (1989 ) t o predic t th e ris k fro m arseni c i n soi l an d dus t ar e a s follows : Noncance r Ris k H I = (C^cHIF^RBA

, + C^cHIF/RBA^/oRf

D (4

) Cance r Ris k Ris k = (C^lffiF^RBA

, + C/lHIF

d *RBA

d )*oS F (5 ) where : cHI F = chroni c huma n intak e facto r fo r soi l o r dust

= (IR/BW)*(EF/365

) 1HI F = lifetim e averag e huma n intak e facto r fo r soi l o r dust

= (IR/BW)*(EF/365)*(ED/AT ) oRf D = Ora l referenc e dos e fo r arseni c oS F = Ora l slop e facto r fo r arseni c 3.1.2 Inpu t Parameter s A s wa s discusse d previously
, exposur e parameter s var y widel y fro m perso n t o perso n an d fro m plac e t o place
, s o i t i s expecte d tha t ther e i s a wid e rang e o f dose s an d risk s tha t coul d occu r i n th e populatio n o f worker s i n Leadville

. Therefore

, a Mont e Carl o simulatio n o f variability
, simila r t o tha t describe d i n Sectio n 2. 5 above
, wa s use d t o estimat e thi s rang e o f risks

. Th e PDF s chose n t o represen t th e variabilit y h i eac h inpu t paramete r ar e describe d below

.

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. epa\48_32_9 0C

, an d Q Dat a ar e availabl e fro m a numbe r o f studie s o n th e distributio n o f arseni c value s i n soil s i n th e communit y o f Leadville

. Thes e dat a revea l tha t averag e arseni c concentration s var y a s a functio n o f locatio n withi n th e community , tendin g t o b e highes t i n th e easter n section s o f tow n wher e mos t o f th e histori c mining-relate d activitie s occurred
, an d southwes t o f tow n nea r th e locatio n o f th e A V smelter

. However

, fo r th e purpose s o f simulatin g th e expecte d distributio n o f exposure s i n worker s (no w o r i n th e future)

, th e mos t appropriat e dat a ar e fo r th e communit y a s a whole

. Statistic s availabl e fro m severa l majo r studie s are summarize d below

. Stud y Wals h 198 8 WESTO N 199 1 Bornschei n 199 4 CO M 199 4 Sampl

e Typ e Dept h = 0-6 " Dept h = 0-6 " Perimete r Bar e Are a Dept h = 0-6 " N 59 9 12 1 1 4 2 8 382 6 Mea n 5 1 14 0 6 1 6 8 8 3 S T D 8 1 18 1 15 3 5 3 19 1 I n al l o f thes e studies
, th e dat a ar e observe d t o b e left-skewe d i n a n approximatel y lognorma l distribution

. Base d o n these studies
, a representativ e valu e fo r th e mea n i s judge d t o b e abou t 7 0 pp m an d a representativ e valu e fo r th e standar d deviatio n i s judge d t o b e abou t 15 0 ppm

. Thus

, variabilit y i n C

s wa s estimate d wit h th e followin g PDF : C

s = LOGNORMAL(70,150

) Onl y on e stud y (Bornschei n 1994 ) ha s investigate d th e distributio n o f arseni c level s i n interior dus t sample s i n Leadville

. Thes e dat a wer e collecte d i n 24 1 privat e residences
, bu t i t seem s reasonabl e t o assum e tha t level s i n commercia l establishment s ar e likel y t o b e similar

. Th e observe d mea n an d standar d deviatio n o f th e dus t value s wer e 3 2 pp m an d 2 3 ppm , respectively

. A s wa s th e cas e fo r soils
, th e dat a ar e observe d t o b e left-skewe d i n a n approximatel y lognorma l distribution

. Base d o n this
, th e valu e o f C d wa s modele d as : C d = LOGNORMAL(32,23

)

Th e PDF s selecte d fo r evaluatin g soi l an d dust intak e h i th e workplac e ar e th e sam e a s use d i n Sectio n 2. 5 fo r lead

. EF

. ED

. an d A T Th e PDF s selecte d t o mode l variabilit y i n exposur e frequenc y t o soi l an d dust h i th e workplac e ar e th e sam e a s describe d i n Sectio n 2. 5 fo r lead

. Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulch Superfun d Sit e — Par t C

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. epa\4 8 32_9 0Standar d

guidanc e (EP A 1991a ) indicate s tha t th e RM E exposur e duratio n fo r worker s i s 2 5 years

. Draf t guidanc e (EP A 1993 ) suggest s tha t th e defaul t fo r centra l tendenc y exposur e duratio n i s 5 years , althoug h n o supportin g rationa l for thi s valu e i s provided

. Assumin g tha t th e minimu m duratio n o f workplac e exposur e t o environmenta l arseni c tha t i s o f potentia l toxicologica l concer n i s tw o years , variabilit y i n exposur e duratio n wa s modele d as : E D = TRIANGULAR(2,5,25

) Averagin g tim e fo r cance r risk s wa s 7 0 year s (treate d a s a constant)

, an d averagin g tun e fo r noncance r wa s equa l t o th e exposur e duratio n (EP A 199la)

. Bod y Weigh t (BW ) Dat a o n th e distributio n o f bod y weight s i n male s an d female s ha s bee n summarize d an d analyze d b y Brainar d an d Burmaste r (1992)

. Th e dat a are wel l fi t b y lognorma l distributions
, wit h th e followin g parameters : Populatio n Male s Female s Mea

n o f ln(BW ) (Ibs ) 5.1 4 4.9 5 STDo f m(BW ) (Ibs ) 0.1 7 0.2 1 Thes e PDF s wer e converte d t o unit s o f k g ( 1 I b = 0.45 4 kg)

, an d th e tw o separat e PDF s wer e combine d int o on e b y samplin g fro m eac h wit h a relativ e frequenc y o f 0.5 , an d fittin g th e resultin g dat a t o a lognorma l distribution

. Th e resultin g PD F ha s a G M o f 7 0 k g an d a GS D

o f 1.24

. Base d o n this
, th e PD F fo r B W i s a s follows : B W = LOGNORMAL2(70,1.24

) EBA

, EP A Region VII I guidanc e recommend s a defaul t relativ e bioavailabilit y facto r fo r arseni c i n soi l
o f 0. 8 (EP A 1993)

. Ther e hav e not yet bee n an y studie s o f arseni c absorptio n fro m soil s fro m the Californi a Gulc h site , bu t ther e hav e bee n tw o studie s o f arseni c absorptio n fro m soil s collecte d i n Anaconda

, Montan a (Johnso n e t al

. 1991, Freema n e t al

. 1994)

. Thes e studie s ar e subjec t t o som e limitation s an d uncertainties , bu t th e dat a sugges t tha t i n animal s (rabbit s an d monkeys)

, arseni c absorptio n fro m th e soi l use d h i thes e studies i s abou t 20 % o f tha t fo r solubl e sodium arsenate

. EP A doe s no t fee l i t i s appropriat e t o extrapolat e dat a fro m sit e t o sit e an d fro m sampl e t o sampl e withou t carefu l assessmen t o f the similarit y (o r lac k thereof ) i n geochemica l characteristic s o f th e soils
, bu t thes e dat a d o sugges t tha t bioavailabilit y o f arseni c ma y var y

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. epa\48_32_9 0fro m

locatio n t o location

. I n the absenc e o f an y site-specifi c data
, the possibl e rang e o f arseni c bioavailabilit y i n soil s a t th e Californi a Gulch sit e wer e modele d a s follows : RB A = UNIFORM(0.2,0.8

) I t shoul d b e emphasize d tha t thi s PD F i s base d o n professiona l judgemen t only
, an d migh t lea d t o either a n overestimat e o r a n underestimat e o f th e tru e rang e o f RB A fo r arseni c i n sit e soils

. oRf D an d oS F Th e ora l referenc e dos e an d ora l cance r slop e factor s use d ar e thos e recommende d b y th e EP A (IRI S 1994) : oRf D = 3E-0 4 mg/kg- d o S F = 1.75E+0 0 (mg/kg-d)' 1 Althoug h i t i s likel y tha t ther e i s variabilit y i n th e susceptibilit y t o arseni c betwee n individuals
, thes e term s wer e modele d a s constants

. Uncertaintie s an d controversie s regardin g thes e toxicit y value s ar e discusse d i n Par t B o f thi s ris k assessment

. Summar y o f Variabilit y PDF s Tabl e 3 list s th e PDF s selecte d t o evaluat e th e rang e o f arseni c risk s tha t coul d b e experience d b y worker s i n Leadville

. 3.1. 3 Result s Mont e Carl o simulation s wer e performe d (500 0 iteration s pe r simulation ) usin g th e PDF s abov e t o describ e th e variabilit y i n noncance r an d cance r ris k level s i n worker s associate d wit h exposur e t o arseni c i n soi l o r dust a t th e workplace

. Th e result s ar e summarize d below

. Variabilit y Parameter Media n Mean 95t h Percentil e Ris

k Estimat e Hazar d Inde x 2E-0 2 3E-0 2 8E-0 2 Cancer Ris k IE-0 6 2E-0 6 7E-0 6 A s shown
, th e predicte d population-base d distributio n o f risk s fro m arseni c i s belo w th e norma l health-base d criterio n bot h fo r noncance r an d cance r effects

. However

, thi s doe s not necessaril y prov e tha t ther e ar e n o specifi c sublocation s withi n th e sit e wher e arseni c concentration s i n soi l
an d dust migh t b e hig h enoug h t o b e o f potentia l concer n t o worker s a t thos e sublocations

. Th e followin g sectio n evaluate s th e rang e o f arseni c concentration s whic h migh t b e o f concer n t o Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epa\48_32_9 0TABL

E 3

. SUMMAR Y O F VARIABILIT Y DISTRIBUTIO N FUNCTION S F O R ESTIMATIO N O F ARSENI C EXPOSUR E I N WORKER S
Mode l Inpu t Concentratio n i n soi l Concentratio n i n dus t Ingestio n rat e o f soil/dus t a t workplac e Exposur e frequenc y a t wor k Exposur e frequenc y t o soi l outdoor s Exposur e frequenc y t o dust indoor s Exposur e duratio n a t workplac e Bod y weigh t Averagin g tim e Arseni c relativ e bioavailabilit y Abbr

.



## c s 

## c d 

## iRs d E F

, E F S E F d E D
B W A T RB A Unit s mg/k g mg/k g mg/da y days/y r days/y r days/y r year s
k g year s

— Distributio n Shap e Lognormal Lognormal Triangula r Triangula r Triangula r Calculate d a s EF ^ - EF S Triangula r Lognorma l Noncancer : A T = E D Cancer : A T = 7 0 Unifor m Parameter

s o f Distributio n Mea n = 7 0 ST D = 15 0 Mea n = 3 2 S T D = 2 3 Mi n = 1 0 Mod e = 3 0 Ma x = 12 0 Mi n = 20 0 Mod e = 21 9 Ma x = 25 0 Mi n = 0 Mod e = 1 0 Ma x = 10 0

— Mi n = 2 Mod e = 5 Ma x = 2 5 G M = 7 0 GS D = 1.2 4

- - Mi n = 0. 2 Ma x = 0. 8

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. epa\48_32_9 0individual

s a t a workplace

. 3 . 2 CALCULATIO

N O F WORKPLAC E SOI L ACTIO N LEVE L FO R ARSENI C

3.2. 1 Basi c Equatio n Recal l tha t th e basi c equation s use d t o predic t noncance r an d cance r risk s h i a n individua l expose d t o arseni c i n soi l an d dus t are : Noncance r Ris k H I = (C

s *cHIF

s *RBA

s + C/cfflF^RBA^/oRf

D (4

) Cance r Ris k Ris k = (C S *1HIF

S *RBA

S + C d *lHIF

d *RBA

d )*oS F (5

) Becaus e thes e equation s contai n term s fo r bot h soi l an d dus t exposure , the y canno t b e solve d fo r th e soi l ter m (C

s ) unles s th e dus t ter m (C^ ) i s define d a s a dependen t variabl e whos e value ca n b e predicte d fro m th e valu e o f soil

. Assumin g tha t soi l comprises som e (bu t no t all ) o f th e mas s o f indoo r dust
, th e concentratio n o f lea d h i dus t ca n b e describe d usin g a n equatio n o f th e followin g form : C d = D
0 + Ksd*C

s Settin g th e valu e o f D
0 t o zer o (fo r th e reason s discusse d previously)

, an d substitutin g thi s expressio n int o th e basi c equation s above
, th e equation s fo r calculatin g th e noncance r an d cance r action level s fo r arseni c ar e a s follows : A L

n c = m^*oRffl/(cfflF.*RBA
1 + K s d *cHIF

d ) (6

) A L C = Risk iarget /((lHIF

s *RBA

s + K s d *lfflF d )*oSF ) (6

) Th e overal l actio n leve l for soi l i s the n th e mor e stringent (lower ) o f thes e tw o values : Typically

, th e health-base d goal s fo r thes e calculation s ar e tha t a perso n at th e uppe r portio n o f th e dos e distributio n (i.e.

, th e RM E individual ) shoul d hav e a Hazar d Inde x whic h doe s no t
excee d 1E+0 0 an d a n exces s cance r ris k whic h doe s no t excee d IE-04

. Screenin g leve l calculation s sho w tha t fo r arsenic , base d o n thes e healt h goals
, i t i s cance r ris k whic h yield s th e mor e stringen t actio n level

. Therefore

, onl y th e equatio n fo r th e cancer-base d actio n leve l i s evaluate d below

.

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### 3.2. 2

Uncertaint y PDF s Th e objec t o f th e actio n leve l calculatio n i s t o estimat e a concentratio n tha t wil l b e protectiv e eve n fo r a perso n a t th e uppe r en d o f th e exposur e distribution

. Therefore

, severa l o f th e input s int o th e equatio n abov e are intende d t o b e value s appropriat e for th e RM E individual

. I f th e tru e value s o f thes e RM E parameter s wer e known
, the n th e equatio n woul d yiel d a singl e numeri c valu e (the actio n level ) tha t i s equa l t o th e soi l arseni c concentratio n tha t ensure s th e heath-base d goal s ar e me t fo r RM E individuals

. However

, ther e i s substantial uncertaint y h i th e tru e valu e fo r mos t o f thes e variables

. Therefore

, eac h inpu t paramete r wa s describe d b y a PD F whic h describe s uncertaint y abou t th e intende d value
, an d thes e PDF s wer e use d h i a Mont e Carl o simulatio n t o estimat e th e plausibl e rang e o f th e actio n level

. RM E IR

. an d IR

, Draf t EP A guidanc e specifie s tha t th e RM E soi l an d dus t intak e b y worker s shoul d b e 10 0 mg/day

. Becaus e thi s estimat e i s base d o n relativel y littl e data
, i t i s considere d t o b e highl y uncertain

. Base d o n professiona l judgement
, uncertaint y abou t thi s paramete r wa s modele d as : RM E IR,,

, = UNIFORM(50,200

) Exposur e Frequenc y The sam e uncertaint y PDF s fo r workplac e exposur e frequenc y t o soi l and dus t tha t wer e use d t o evaluat e th e actio n leve l fo r lea d wer e als o use d t o evaluat e uncertaint y h i th e action leve l fo r arsenic. RM E Exposur e Duration EP A guidanc e specifie s tha t th e RM E exposur e duratio n fo r worker s shoul d b e 2 5 years , bu t doe s no t provid e an y informatio n o n th e confidenc e h i tha t value

. Base d o n professiona l judgement
, uncertaint y abou t thi s paramete r wa s modele d a s follows : RM E E D = UNIFORM(20,30 ) Averagin g Tun e Averagin g tim e wa s assume d t o b e 7 0 years , an d thi s wa s treate d a s a constan t rathe r tha n a n uncertai n variable

. Thi s i s becaus e applicatio n o f th e cance r slop e facto r fo r arseni c i s base d
o n th e assumptio n o f a 70-yea r lifetime

. Mean Bod y Weigh t Dat a o n adul t bod y weight s ar e derive d fro m measurement s h i a ver y larg e numbe r o f people
, s o ther e i s ver y littl e uncertaint y h i th e tru e mea n value

. Becaus e o f this
, th e valu e fo r bod y weigh t wa s simpl y treate d a s a constan t (7 0 kg)

. Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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. epaW8_32_9 0RM

E Relativ e Bioavailabilit v Ther e ar e presentl y n o measurement s o f arseni c relativ e bioavailabilit y h i site-specifi c soil s o r dusts
, s o i t i s difficul t t o evaluat e th e uncertaint y aroun d th e defaul t RM E valu e o f 0.8

. Base d
o n professiona l judgement
, the followin g PD F wa s used : RM E RB A = UNIFORM(0.7,0.9

) Soil/Dus t Relationsh i Dat a o n th e relationshi p betwee n arseni c concentratio n level s h i dus t an d soi l (C

s , C d ) ar e availabl e fro m th e environmenta l dat a se t collecte d b y th e Universit y o f Cincinnat i i n 1991

. Emplo y in g th e sam e analysi s approac h a s described h i Par t B an d h i Sectio n 2.6. 3 (above)

, th e value s estimate d fo r D
0 an d K. d are a s follows : Paramete r Numbe r o f paire d sample s Mean o f dus t (D ) Mean o f soi l (S ) Estimate d D
0 a Calculate d Kj * Soi l

Typ e Perimete r 1 4 5 1 6 1 2 9 0.3 6 Bar e Are a 2 8 3 3 6 8 1 8 0.2 2

a Mea n o f dust sample s wher e soi l arseni c i s lo w ( < 1 0 ppm ) b Calculate d a s ( D

- D
0 )/(S ) Becaus e thes e calculation s ar e base d o n a rathe r smal l dat a set , th e result s ar e considere d t o b e rathe r uncertain

. Therefore

, th e uncertaint y aroun d th e mea n valu e o f Ks d wa s modele d as : K,,

, = UNIFORM(0.2,0.6

) A s note d above
, th e valu e o f D
0 i s se t a t zer o fo r th e purpose s o f estimatin g a n actio n level

. Summar y o f Uncertaint y PDF s Tabl e 4 summarize s the PDF s selecte d t o describ e the uncertaint y aroun d the input s needed t o calculat e a n actio n leve l fo r worker s expose d t o arseni c h i soi l an d dust

. 3.2. 3 Result s Th e result s o f a Mont e Carl o simulatio n o f th e uncertaint y aroun d th e actio n leve l ar e show n i n Figur e 3 , A s seen , th e plausibl e rang e o f actio n level s coul d conceivabl y rang e fro m a s low a s Baseline Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e - Par t C

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. epa\48_3 2 9 0TABL

E 4

. SUMMAR Y O F UNCERTAINT Y DISTRIBUTIO N FUNCTION S F O R ESTIMATIO N O F ARSENI C SOI L ACTIO N LEVE L
Mode l Inpu t RM E ingestio n rat e o f soil/dus t RM E exposur e frequenc y a t wor k Exposur e frequenc y t o soi l outdoor s Exposur e frequenc y t o dus t indoor s RM E exposur e duratio n a t workplac e Bod y weigh t Averagin g tim e Mass fractio n o f soi l i n dust RM E relativ e bioavailabilit y Abbr

. IRs a E F
t E F S E F d E D
B W A T K s d RB A Unit s mg/da y days/y r days/y r days/y r year s
k g year s

—

— Distributio n Shap e Unifor m Unifor m Triangula r Calculate d as : F F
- F F • c/

r tota l J

-'- r s Unifor m Constan t Constant Unifor m Unifor m Parameter

s o f Distributio n Mi n = 5 0 Ma x = 15 0 Mi n = 24 0 Ma x = 26 0 Mi n = 5 Mod e = 1 0 Ma x = 2 0

- - Mi n = 2 0 Ma x = 30
7 0 7 0 Mi n = 0. 2 Ma x = 0. 6 Mi n = 0. 7 Ma x = 0. 9

Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulc h Superfun d Sit e — Par t C

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pp m (th e 5t h percentile ) t o a s hig h a s 130 0 pp m (th e 95t h percentile)

. Centra l tendenc y value s includ e 61 0 pp m (th e geometri c mean ) an d 69 0 pp m (th e arithmeti c mean)

. 3.2. 4 Compariso n wit h Sit e Concentration s Dat a o n arseni c level s measure d i n surficia l soi l (0- 1 inch ) i n an d aroun d Leadvill e ar e show n h i Figur e 4 (CD M 1994)

. Inspectio n o f thi s ma p reveal s tha t averag e arseni c level s ar e no t expecte d t o excee d abou t 5 0 pp m h i th e mai n busines s sectio n o f Leadville

, an d tha t expecte d

mea n level s d o no t appea r t o excee d th e soi l actio n leve l fo r worker s anywher e a t th e sit e excep t possibl y fo r the are a nea r the forme r A V Smelte r locate d southwes t o f town

. A s before
, i t i s importan t t o understan d tha t i t i s averag e arseni c level ove r a n are a whic h shoul d b e compare d t o th e soi l actio n level

. Tha t is , occasiona l measurement s o r smal l "hot

spots " o f concentration s abov e th e action leve l d o no t necessaril y constitut e evidenc e tha t a n are a i s unsafe

.

Baselin e Huma n Healt h Ris k Assessmen t fo r th e Apri l 199 5 Californi a Gulch Superrun d Sit e — Par t C

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