Determining the Impacts on Human Health Attributable to

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Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 30, 2018 | https://pubs.acs.org Publication Date: October 20, 1982 | doi: 10.1021/bk-1982-0204.ch003

Determining the Impacts on Human Health Attributable to Hazardous Waste Sites VERNON N. HOUK Center for Environmental Health, Centers for Disease Control, Atlanta, GA 30333

The Superfund Act and implementing E x e c u t i v e Order assign to the Department of H e a l t h and Human Services the responsibility for assessing the threat hazardous waste s i t e s pose to the h e a l t h of workers and the general p u b l i c . Our working definition for such a h e a l t h risk assessment i s the determination of probabilities of v a r i o u s adverse h e a l t h outcomes that r e s u l t or would r e s u l t from exposure to s p e c i f i e d hazards. To fulfill our l e g a l mandate, we intend first to determine the nature and q u a n t i t y of t o x i c m a t e r i a l s present at Superfund sites, the s i z e and p r o x i m i t y of potentially exposed human p o p u l a t i o n s , and the existence of likely pathways for s i g n i f i c a n t human exposure. I f all three f a c t o r s are present, a d d i t i o n a l study through v a r i o u s approaches, such as exposure documentation s t u d i e s , d i s e a s e - r e l a t e d epidemiologic s t u d i e s , or disease registries, will be considered.

I n December 1980, P r e s i d e n t C a r t e r s i g n e d i n t o l a w a b i l l known as t h e C o m p r e h e n s i v e E n v i r o n m e n t a l R e s p o n s e , Compensation and L i a b i l i t y A c t — m o r e commonly known as t h e S u p e r f u n d A c t . I t i s d e s i g n e d t o d e a l w i t h t h e b u r g e o n i n g p r o b l e m o f c l e a n i n g up o l d and abandoned h a z a r d o u s w a s t e s i t e s . The A c t imposes a t a x on t h e c h e m i c a l i n d u s t r y and t h e n a l l o c a t e s t h a t money, a l o n g w i t h a F e d e r a l and S t a t e c o n t r i b u t i o n , t o s i t e s n e e d i n g emergency r e s p o n s e o r l o n g - t e r m c l e a n u p ; a s s e s s m e n t o f h e a l t h e f f e c t s w h i c h may r e s u l t f r o m e x p o s u r e ; and e n f o r c e m e n t a c t i o n against p a r t i e s r e s p o n s i b l e f o r these s i t e s , i n c l u d i n g generat o r s , t r a n s p o r t e r s , and s i t e owners. O f f i c i a l s o f the E n v i r o n m e n t a l P r o t e c t i o n Agency (EPA) t e s t i f i e d b e f o r e C o n g r e s s t h a t EPA h a d i d e n t i f i e d o v e r 9,600 u n c o n t r o l l e d h a z a r d o u s w a s t e s i t e s , h a d made p r e l i m i n a r y a s s e s s m e n t s o f 6,100 o f t h e s e , and, b y J u l y 1981, h a d c o m p l e t e d 0097-615 6/82/0204-0021 $06.00/0 © 1982 American Chemical Society

Long and Schweitzer; Risk Assessment at Hazardous Waste Sites ACS Symposium Series; American Chemical Society: Washington, DC, 1982.


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a l m o s t 2,800 o n - s i t e i n s p e c t i o n s , i n c l u d i n g some s a m p l i n g o f s i t e c o n t e n t s and g r o u n d and s u r f a c e w a t e r . The C e n t e r s f o r D i s e a s e C o n t r o l (CDC), an agency o f t h e P u b l i c H e a l t h S e r v i c e , h a s been a s s i g n e d t h e r e s p o n s i b i l i t y f o r implementing the h e a l t h - r e l a t e d portions of Superfund f o r the D e p a r t m e n t o f H e a l t h and Human S e r v i c e s . A l t h o u g h CDC h a s t h e p r i n c i p a l r o l e i n m e a s u r i n g t h e i m p a c t o r p o t e n t i a l i m p a c t on human h e a l t h w h i c h may be r e l a t e d t o e x p o s u r e , t h e N a t i o n a l T o x i c o l o g y P r o g r a m and t h e N a t i o n a l L i b r a r y o f M e d i c i n e h a v e a c t i v e r o l e s i n p r o v i d i n g u p - t o - t h e - m i n u t e i n f o r m a t i o n about t h e known h e a l t h e f f e c t s o f c h e m i c a l s o r c h e m i c a l c o m b i n a t i o n s f o u n d i n Superfund s i t e s . S i m i l a r l y , CDC s N a t i o n a l I n s t i t u t e f o r O c c u p a t i o n a l S a f e t y and H e a l t h w i l l h e l p e n s u r e t h a t t h e h e a l t h o f emergency p e r s o n n e l and c l e a n u p w o r k e r s i s p r o t e c t e d when they respond i n Superfund a c t i o n s . The tremendous number o f o r p h a n e d w a s t e s i t e s i n t h i s c o u n t r y r e f l e c t s t h e growth o f the s y n t h e t i c o r g a n i c c h e m i c a l i n d u s t r y ( F i g u r e 1 ) . I n 1940, a p p r o x i m a t e l y one b i l l i o n pounds o f s y n t h e t i c o r g a n i c c h e m i c a l s were p r o d u c e d i n t h e U n i t e d States. By 1965, t h i s q u a n t i t y had i n c r e a s e d n e a r l y a h u n d r e d f o l d and i t now e x c e e d s 300 b i l l i o n pounds a y e a r . T h i s e x p o n e n t i a l growth o f the i n d u s t r y has a worrisome byp r o d u c t i n t h e m a s s i v e p r o b l e m o f t o x i c w a s t e d i s p o s a l . To d e t e r m i n e i f s u c h w a s t e s c a u s e h e a l t h damage i n e x p o s e d human p o p u l a t i o n s , we must c o n d u c t e p i d e m i o l o g i c i n v e s t i g a t i o n s o f r e l a t i o n s h i p s b e t w e e n t o x i c e x p o s u r e and p o s s i b l e a d v e r s e h e a l t h outcome, c l i n i c a l o r s u b c l i n i c a l . I n c o n d u c t i n g human h e a l t h s t u d i e s b e f o r e S u p e r f u n d was e n a c t e d , we f o u n d t h a t s u c h i n v e s t i g a t i o n s a r e c o n c e p t u a l l y s i m p l e and i n v o l v e s t r a i g h t f o r w a r d c o n c e p t s o f c a u s e and e f f e c t . I m p l e m e n t i n g t h e s e s t u d i e s , however, i s " e a s i e r s a i d t h a n done." Because o f the e x t r e m e l y d i v e r s e s i t u a t i o n s i n which hazardous m a t e r i a l s a r e i n v o l v e d , each study presents unique problems. Table I i l l u s t r a t e s the d i v e r s i t y , both i n waste m a t e r i a l s and e x p o s u r e s e t t i n g s , o f e i g h t r e c e n t t o x i c w a s t e situations. D i f f e r e n c e s , i n f a c t , c a n be q u i t e l a r g e , r a n g i n g f r o m t h e common d r u m - f i l l e d dump s i t e t o t h e w i d e s p r e a d d i s p e r s a l o f waste m a t e r i a l . Some g e n e r a l i z a t i o n s , however, c a n be made about t h e s e k i n d s o f s t u d i e s . E p i d e m i o l o g i c s t u d i e s u s u a l l y c o n s i s t o f three fundamental phases: ( 1 ) D e t e r m i n i n g what t o x i c m a t e r i a l s a r e p r e s e n t , (2) e s t a b l i s h i n g how human e x p o s u r e t o t h e s e t o x i c m a t e r i a l s m i g h t o c c u r , and ( 3 ) m e a s u r i n g a c t u a l o r p o t e n t i a l b i o l o g i c effects. S u b s t a n t i v e i n f o r m a t i o n i n e a c h o f t h e s e phases i s e s s e n t i a l f o r s u c c e s s f u l l y c o m p l e t i n g any e p i d e m i o l o g i c s t u d y . The f i r s t s t e p i n any t o x i c w a s t e s t u d y i s t o d e t e r m i n e what t o x i c m a t e r i a l s a r e p r e s e n t and i n what amounts. Since most t o x i c w a s t e s i t u a t i o n s i n v o l v e t h e dumping o f d i v e r s e m a t e r i a l s , p r o b l e m s o f e x p e n s i v e t e c h n i c a l m e t h o d o l o g y c a n be formidable. However, w i t h o u t an a d e q u a t e i n v e n t o r y o f t h e 1



Ηουκ

Impacts on Human Health

1915

1925

1935

1945 Year

1955

1965

1975

Figure 1. Historical growth of the synthetic organic chemical industry. (Repro duced from Ref. 15.)


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A T HAZARDOUS W A S T E

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TABLE I


R e c e n t S i t u a t i o n s I n v o l v i n g P o t e n t i a l Human Exposure t o P o t e n t i a l l y T o x i c Waste M a t e r i a l s Principal Routes of Potential Human E x p o s u r e

Location of S i t e

Toxic Materials

Physical Condition

L o v e C a n a l dump Niagara F a l l s , New Y o r k

Largely hydro carbon residues from p e s t i c i d e production

I n a c t i v e landf i l l i n resi d e n t i a l area

Direct, air b o r n e , and waterborne contacts

M e l v i n Wade dump, C h e s t e r , Pennsylvania

Diverse organic chemicals

Surface c o l l e c t i o n waste i n drums i n urban s e t t i n g

Direct contact, e x p l o s i o n , and fire

Woburn, Massachusetts

A r s e n i c com pounds , h e a v y metals, organic chemicals

Abandoned waste lagoon with multiple s u r f a c e dumps

D i r e c t and waterborne contacts

Triana, Alabama

DDT and r e l a t e d compounds

Industrial w a s t e dumped in a rural stream

Food c h a i n (fish)

Βloomington, Indiana

Polychlorinated biphenyls (PCB s)

Direct contact Industrial waste contamiand p o s s i b l y nating municifood c h a i n p a l sewage u s e d f o r garden manure

T r i s t a t e Mining District, Oklahoma, K a n s a s , and Missouri

Heavy m e t a l s , acidic aquifer

Mine t a i l i n g s and a c i d i c aquifer recharge

Montgomery County, Pennsylvania

Trichlorethylene

Industrial D i r e c t and waste contamiwaterborne nating aquifer; contacts underground s t o r a g e tank rupture

Pittston, Pennsylvania

Chlorinated s o l v e n t s , HCN, and h e a v y metals

M i l l i o n s of g a l l o n s of w a s t e dumped i n t o abandoned mine s h a f t s

f

A i r b o r n e and irreparably contaminated aquifer

Food c h a i n and waterborne exposure



3.

HOUR

Impacts on

Human Health

25

c h e m i c a l s — t h e i r q u a l i t y and q u a n t i t y and t h e p h y s i c a l c o n d i t i o n s under which they are p r e s e n t — i t i s premature, i f not i m p o s s i b l e , t o d e s i g n adequate e p i d e m i o l o g i c s t u d i e s . I f o n l y low c o n c e n t r a t i o n s o r s m a l l amounts o f t o x i n s a r e p r e s e n t , t h e r e may not be s u f f i c i e n t r e a s o n t o p r o c e e d w i t h i n v e s t i g a t i o n s . The d e c i s i o n o f w h e t h e r t o p r o c e e d i s not a l w a y s s i m p l e , s i n c e p u b l i c c o n c e r n and p o l i t i c a l p r e s s u r e can be c o m p e l l i n g e v e n i n the absence o f a c o n f i r m e d t o x i c exposure. D e s p i t e such p r e s s u r e s , i t i s important to r e a l i z e t h a t c o n d u c t i n g even a simple survey o f h e a l t h e f f e c t s i s p e r i l o u s i f one l a c k s i n f o r m a t i o n about t o x i n s and e x p o s u r e , s i n c e few, i f any, m e a s u r a b l e h e a l t h e f f e c t s a r e s u f f i c i e n t l y s p e c i f i c f o r e x p o s u r e t o p a r t i c u l a r t o x i n s o r g r o u p s o f t o x i n s t o be s u r r o gates f o r d i r e c t l y measuring t o x i c exposure. A f t e r a s s e s s i n g t h e n a t u r e and q u a n t i t i e s o f t o x i n s p r e s e n t , one must e v a l u a t e t h e i r p o t e n t i a l f o r human e x p o s u r e . E v e n when m a t e r i a l s known t o be t o x i c a r e p r e s e n t , human e x p o s u r e may not h a v e o c c u r r e d o r may be o n l y r e m o t e l y p o s s i b l e . B e f o r e e x p o s u r e c a n be e v a l u a t e d , t h e means o f e x p o s u r e ( f o r e x a m p l e , d i r e c t c o n t a c t , c o n t a m i n a t e d w a t e r , o r c o n t a m i n a t e d a i r ) must be d e t e r m i n e d , and the s i z e o f human p o p u l a t i o n s p o t e n t i a l l y e x p o s e d and t h e i r d e g r e e o f p r o x i m i t y t o t h e t o x i c m a t e r i a l s must be defined. A n o t h e r r e a s o n one must c o n s i d e r the n a t u r e o f t h e c h e m i c a l s i n v o l v e d i s t h a t some c h e m i c a l s p a s s t h r o u g h t h e body q u i c k l y , whereas o t h e r s are s t o r e d i n t i s s u e . Exposure to c h e m i c a l s w h i c h p e r s i s t i n t i s s u e , s u c h as P o l y c h l o r i n a t e d B i p h e n y l s ( P C B ' s ) o r DDT, o f c o u r s e , p r o v i d e s much g r e a t e r o p p o r t u n i t y f o r p r o d u c t i v e epidemiologic study than exposure to t r a n s i e n t a g e n t s ( s u c h as t r i c h l o r o e t h y l e n e i n Montgomery C o u n t y ) . Many s t u d i e s a r e u n d e r t a k e n l o n g a f t e r a c t i v e e x p o s u r e has occurred. I n s u c h s t u d i e s , e x p o s u r e can be j u d g e d o b j e c t i v e l y by m e a s u r i n g l e v e l s of p e r s i s t e n t t o x i n s i n t i s s u e . The p r i m e o b j e c t i v e i n e p i d e m i o l o g i c s t u d i e s i s t o a s s o c i a t e p a r t i c u l a r e x p o s u r e s w i t h p o t e n t i a l h e a l t h e f f e c t s and t h u s t o d e f i n e c a u s e - e f f e c t r e l a t i o n s h i p s . S i n c e t h i s p r o c e s s i s an i n d i r e c t a s s e s s m e n t , i t i s h i g h l y d e p e n d e n t on t h e a c c u r a c y and s p e c i f i c i t y o f o b s e r v a t i o n s r e c o r d e d b o t h f o r e x p o s u r e and outcome. I t i s a more p o w e r f u l s t u d y i f d o s e - r e s p o n s e r e l a t i o n s h i p s c a n be shown, t h a t i s , i f i n c r e a s i n g l e v e l s o f e x p o s u r e are a s s o c i a t e d w i t h i n c r e a s i n g f r e q u e n c y of the h e a l t h e f f e c t s in individuals. To d e t e r m i n e t h i s c a u s e - e f f e c t r e l a t i o n s h i p , t h e e p i d e m i o l o g i s t must be aware o f f o u r d i f f i c u l t i e s w h i c h can l i m i t t h e power o f an e p i d e m i o l o g i c i n v e s t i g a t i o n ( T a b l e I I ) . The f i r s t i n v o l v e s t h e s i z e o f t h e p o p u l a t i o n needed f o r a s t u d y t o demons t r a t e a g i v e n h e a l t h e f f e c t w i t h a g i v e n d e g r e e o f power. This depends b o t h on t h e d e g r e e o f e x p o s u r e and on t h e e x p e c t e d b a s e l i n e frequency o f the p a r t i c u l a r h e a l t h e f f e c t . I f the



RISK ASSESSMENT A T HAZARDOUS W A S T E SITES

TABLE I I E p i d e m i o l o g i c Issues Fundamental t o E v a l u a t i n g P o t e n t i a l T o x i c Waste H e a l t h E f f e c t s Epidemiologic

Issues

Impact on E p i d e m i o l o g i c

Study

Expected b a s e l i n e frequency of s p e c i f i c h e a l t h e f f e c t s

R e l a t i v e l y low expected f r e quency r e q u i r e s l a r g e p o p u l a t i o n f o r study, e s p e c i a l l y to detect small increases i n risk.

Latency

Long l a t e n c y may r e q u i r e p e r i odic or continuous long-term population followup.

period

Multiple causative factors (clinical nonspecificity)

Since p a r t i c u l a r health e f f e c t s are not o f t e n s p e c i f i c f o r p a r t i c u l a r t o x i c exposures, d a t a must b e c o l l e c t e d and evaluated.

A l t e r a t i o n of r o u t i n e l y c o l l e c t e d exposure and/or outcome i n f o r m a t i o n t o coincide

D i m i n i s h e s p r e c i s i o n o f exposure/outcome r e l a t i o n s h i p .



3.

HOUK

Impacts on

Human Health

27

h e a l t h outcome t o be measured i s r a r e , t h e p o p u l a t i o n t o be s t u d i e d needs t o be l a r g e . The s e c o n d d i f f i c u l t y i s t h a t o f l o n g o r v a r i a b l e l a t e n c y , t h e p e r i o d b e t w e e n e x p o s u r e and m e a s u r a b l e e f f e c t . At lower l e v e l s o f t o x i c e x p o s u r e , outcomes s u c h as c a n c e r may not o c c u r u n t i l years l a t e r . T h i s means t h a t t h e s t u d y d e s i g n must i n c l u d e long-term h e a l t h followup. The u s u a l r e c o m m e n d a t i o n i s t o e s t a b l i s h an e x p o s u r e r e g i s t r y , w i t h a 20- t o 2 5 - y e a r s t u d y . The a l t e r n a t i v e i s t o s t u d y c u r r e n t c a n c e r i n a p o p u l a t i o n known t o have been e x p o s e d o v e r a span o f y e a r s . Neither alternative i s e a s y s i n c e r e g i s t r i e s a r e e x p e n s i v e and c o m p l i c a t e d l o g i s t i c a l l y by t h e m o b i l i t y o f t h e U.S. population. The t h i r d d i f f i c u l t y i s t h a t o f c o m p e t i n g c a u s e s o r , expressed d i f f e r e n t l y , the c l i n i c a l n o n s p e c i f i c i t y o f the h e a l t h e f f e c t s under study. To t h e e p i d e m i o l o g i s t , t h i s means a d j u s t i n g f o r many p o t e n t i a l c o n f o u n d i n g f a c t o r s i n a s t u d y . The s t u d y d e s i g n must i n c l u d e c o l l e c t i n g d a t a on o t h e r e x p o s u r e s t h a t might a l s o cause the h e a l t h e f f e c t . I n p r a c t i c a l terms, t h i s means c o l l e c t i n g d a t a on p a s t o c c u p a t i o n a l e x p o s u r e s , p e r s o n a l e x p o s u r e s , s u c h as c i g a r e t t e s m o k i n g o r t h e use o f a l c o h o l o r d r u g s , and p e r s o n a l c h a r a c t e r i s t i c s , s u c h as s e x , r a c e , age, and s o c i o e c o n o m i c s t a t u s , w h i c h may p r e d i c t l e v e l s o f r i s k f o r s p e c i f i c d i s e a s e s t a t e s . The more v a r i a b l e s a s t u d y addresses, o f c o u r s e , t h e more c o m p l e x i t s e v e n t u a l a n a l y s i s and the g r e a t e r t h e s i z e o f the p o p u l a t i o n needed f o r a d e q u a t e l y assessing health effects. The f o u r t h d i f f i c u l t y — o n e o f t e n e n c o u n t e r e d — i s t h a t a h e a l t h outcome r o u t i n e l y m e a s u r e d by p o l i t i c a l b o u n d a r i e s ( c a n c e r m o r t a l i t y , f o r i n s t a n c e ) has t o be r e s h a p e d t o e n v i r o n m e n t a l b o u n d a r i e s , s u c h as t h o s e imposed by an a q u i f e r o r w i n d p a t t e r n , to i n c l u d e the p o p u l a t i o n under study. U n l e s s the e x p o s u r e o r outcome b o r d e r s a r e d e f i n e d by p r o p e r l y e x t r a p o l a t i n g o r i n t e r p o l a t i n g them t o c o i n c i d e g e o g r a p h i c a l l y , any cause-and-effeet relationship i s useless. S e v e r a l methods the e p i d e m i o l o g i s t has f o r i n v e s t i g a t i n g r e l a t i o n s h i p s v a r y g r e a t l y i n c o s t , t i m e and e n e r g y expended, and a n a l y t i c and i n t e r p r e t i v e v a l u e . The d e s c r i p t i v e s t u d y i s s i m p l y , as t h e name i m p l i e s , a s e r i e s o f r a t e s , r a t i o s , and p r o p o r t i o n s which h e l p d e s c r i b e e i t h e r the exposure or the outcome i n d e t a i l . The c a s e - c o n t r o l s t u d y i s r e l a t i v e l y e a s y t o c a r r y o u t , and new a n a l y t i c t e c h n i q u e s have a l r e a d y i n c r e a s e d i t s interpretive value. An e x p o s u r e s t u d y , a l t h o u g h not s t r i c t l y i n the r e a l m o f e p i d e m i o l o g y , documents e x p o s u r e i n v a r i o u s substrata of a population. The f o l l o w i n g t h r e e a c c o u n t s o f w a s t e - s i t e i n v e s t i g a t i o n s demonstrate f o u r major approaches to a s s e s s i n g h e a l t h e f f e c t s at hazardous waste s i t e s : (1) D e s c r i p t i v e s t u d i e s , ( 2 ) c a s e - c o n t r o l s t u d i e s , ( 3 ) s t u d i e s , and (4) c o h o r t s t u d i e s .


28

RISK ASSESSMENT A T HAZARDOUS W A S T E


Woburn, M a s s a c h u s e t t s Control Studies

SITES

- A n E x a m p l e o f D e s c r i p t i v e and C a s e -

D u r i n g t h e summer o f 1979, r e s i d e n t s i n t h i s e a s t e r n M a s s a c h u s e t t s town became c o n c e r n e d an a p p a r e n t c l u s t e r o f s i x l e u k e m i a c a s e s , d i a g n o s e d s i n c e 1969 i n c h i l d r e n o f f a m i l i e s l i v i n g i n a 6-block area i n the southeastern p o r t i o n o f t h e town (1970 t o t a l p o p u l a t i o n : 3 7 , 0 6 7 ) . The c l u s t e r was r e p o r t e d t o t h e M a s s a c h u s e t t s D e p a r t m e n t o f P u b l i c H e a l t h (MDPH) a n d t o t h e C e n t e r s f o r D i s e a s e C o n t r o l (CDC) b o t h by l o c a l c i t i z e n s and a B o s t o n p h y s i c i a n . C o n c e r n was a l s o e x p r e s s e d r e g a r d i n g o t h e r cancers, e s p e c i a l l y kidney cancer. An a s s e s s m e n t o f t o w n - s p e c i f i c c a n c e r m o r t a l i t y r a t e s made i n d e p e n d e n t l y by MDPH a t a b o u t t h e same t i m e f o r t h e 1969-1978 d e c a d e i n M a s s a c h u s e t t s showed s t a t i s t i c a l l y s i g n i f i c a n t e l e v a t i o n s i n Woburn f o r a l l c a n c e r s , as w e l l as f o r s e v e r a l s p e c i f i c k i n d s o f c a n c e r . The c o n c e r n about e x c e s s c a n c e r s f o c u s e d on p o s s i b l e c a u s e s r e l a t e d t o t o x i c w a s t e d i s p o s a l s i t e s i n t h e town. From t h e m i d - 1 9 t h c e n t u r y u n t i l t h e 1 9 2 0 s , Woburn h a d b e e n a m a j o r c e n t e r f i r s t f o r c o m m e r c i a l t a n n i n g o f h i d e s and l a t e r f o r chemical production o f lead a r s e n i c a l p e s t i c i d e s . Efforts i n t h e 1970 s t o d e v e l o p an i n d u s t r i a l p a r k i n t h e n o r t h e a s t e r n p a r t o f t h e town u n c o v e r e d s e v e r a l o l d abandoned w a s t e d i s p o s a l s i t e s containing hides or chemicals r e l a t e d to p r i o r i n d u s t r i a l activities. Among t h e t o x i c c h e m i c a l s f o u n d i n e x c e s s i v e amounts were a r s e n i c , l e a d , chromium, and cadmium. C o n c e r n about l e a c h i n g of waste chemicals i n t o d r i n k i n g water l e d t o e x t e n s i v e t e s t i n g o f w e l l s w h i c h s u p p l y t h e town's w a t e r . Two o f 11 s u c h w e l l s showed e x c e s s i v e l e v e l s o f v a r i o u s o r g a n i c c h e m i c a l s ( t r i c h l o r o e t h y l e n e , f o r example). These two w e l l s h a d s u p p l i e d w a t e r , p r i n c i p a l l y t o t h e e a s t e r n h a l f o f t h e town, s i n c e t h e m i d 1960 s and were l o c a t e d a s h o r t d i s t a n c e t o t h e n o r t h o f t h e leukemia c l u s t e r neighborhood. Because o f t h e demonstrated c h e m i c a l l e v e l s , t h e w e l l s were c l o s e d i n 1979. To e x p l o r e t h e p o s s i b l e c a u s e o f r e p o r t e d c a n c e r e x c e s s e s , and p a r t i c u l a r l y t o examine t h e p o s s i b l e r e l a t i o n s h i p between t h e town's t o x i c w a s t e s i t u a t i o n and t h e c h i l d h o o d l e u k e m i a c a s e c o n c e n t r a t i o n , MDPH and CDC, i n 1980, c o n d u c t e d a j o i n t s t u d y . I n c i d e n c e p a t t e r n s f o r s e l e c t e d t y p e s o f c a n c e r were s t u d i e d by u s i n g d a t a c o l l e c t e d from l o c a l and r e g i o n a l h o s p i t a l s o u r c e s . I n c r e a s e d f r e q u e n c i e s f o r c h i l d h o o d l e u k e m i a and f o r k i d n e y c a n c e r were c o n f i r m e d , w i t h t h e c h i l d h o o d l e u k e m i a e x c e s s b e i n g l o c a t e d i n one p a r t i c u l a r c e n s u s t r a c t . S h i f t i n g e p i d e m i o l o g i c g e a r s t o c a s e - c o n t r o l methods, i n v e s t i g a t o r s then obtained a d d i t i o n a l data r e g a r d i n g a wide range o f p o s s i b l e e n v i r o n m e n t a l causes through d e t a i l e d i n t e r views w i t h p a t i e n t s o r r e l a t i v e s o f p a t i e n t s . F o r a l l 12 c h i l d hood l e u k e m i a c a s e s i n t h e town, t h i s p r o c e s s i n c l u d e d i n t e r v i e w s w i t h two a g e - and s e x - m a t c h e d c o n t r o l s drawn from s c h o o l e n r o l l ment l i s t s — o n e f r o m t h e m a t c h e d c a s e n e i g h b o r h o o d , t h e o t h e r f

1

1


3.

Ηουκ



f r o m a n o t h e r p a r t o f t h e town. No c a u s a l f a c t o r s were f o u n d from t h e s e i n t e r v i e w d a t a f o r e i t h e r k i d n e y c a n c e r o r l e u k e m i a . F o r l e u k e m i a i n p a r t i c u l a r , no c l e a r - c u t d i f f e r e n c e s were s e e n i n r e s p o n s e s p r o v i d e d by c a s e and c o n t r o l f a m i l i e s . The l i m i t a t i o n s o f t h e s e o b s e r v a t i o n s c a n be d e s c r i b e d i n terms o f t h e g e n e r a l p r o b l e m s a s s o c i a t e d w i t h s u c h t o x i c w a s t e studies. The h e a l t h outcome o f c o n c e r n ( c a n c e r , s p e c i f i c a l l y c h i l d h o o d leukemia) i s a r e l a t i v e l y r a r e disease. The t o x i c chemical exposure of p a r t i c u l a r persons h a v i n g these d i s e a s e s c o u l d n o t be d i r e c t l y documented, s i n c e t h e o r g a n i c c h e m i c a l s f o u n d i n w e l l w a t e r were t r a n s i e n t . T h e r e f o r e , no means were a v a i l a b l e f o r l i n k i n g p a r t i c u l a r leukemia cases to p a r t i c u l a r t o x i c s u b s t a n c e s . F o r t h e p r e s e n t , t h e n , we a r e l e f t w i t h an a p p a r e n t l e u k e m i a c a s e c l u s t e r and no good e v i d e n c e f o r a s s o c i a t i n g cases w i t h the s t r i k i n g e n v i r o n m e n t a l t o x i c waste p r o b l e m s c l e a r l y p r e s e n t i n t h e town. T r i a n a , Alabama - An E x a m p l e o f a C r o s s - s e c t i o n a l

Study

T r i a n a , w i t h a p o p u l a t i o n o f 600, i s l o c a t e d a t t h e c o n f l u e n c e o f I n d i a n C r e e k and t h e T e n n e s s e e R i v e r . From 1947 u n t i l 1971 DDT was m a n u f a c t u r e d i n a p l a n t 10 k i l o m e t e r s f r o m Triana. S e v e r a l t h o u s a n d t o n s o f DDT i n d u s t r i a l w a s t e accumu l a t e d i n the sediments of a t r i b u t a r y o f I n d i a n Creek. Locally c a u g h t f i s h have had t o t a l DDT r e s i d u a l l e v e l s up t o 100 t i m e s t h e t o l e r a n c e o f 5 p a r t s p e r m i l l i o n (ppm) s e t by t h e Food and Drug A d m i n i s t r a t i o n . The h i g h l e v e l s o f DDT r e s i d u e s i n t h e 12 p e r s o n s s u r v e y e d w e r e s u s p e c t e d o f r e s u l t i n g f r o m t h e i r c o n s u m i n g f i s h w h i c h had a c c u m u l a t e d DDT f r o m s e d i m e n t s . The t a s k a t hand was t o measure r e s i d e n t s ' e x p o s u r e t o DDT and r e l a t e i t , i f p o s s i b l e , to h e a l t h e f f e c t s i n the p o p u l a t i o n — a n example o f a c r o s s - s e c t i o n a l s t u d y . Of t h e 518 p e r s o n s p a r t i c i p a t i n g i n t h e s t u d y , i n c l u d i n g 44 c o m m e r c i a l f i s h e r m e n and t h e i r f a m i l i e s , 96.3 p e r c e n t gave b l o o d specimens. The mean serum DDT l e v e l (76.2 p a r t s p e r b i l l i o n ( p p b ) ) o f 499 p e r s o n s l i v i n g downstream f r o m t h e DDT m a n u f a c t u r i n g p l a n t was about f o u r t i m e s t h e n a t i o n a l mean (16.7 p p b ) . The number o f p a r t i c i p a n t s w i t h h i g h serum l e v e l s o f DDT was s m a l l , and t h e r e f o r e no sound c o n c l u s i o n s c o u l d be drawn from the s t u d y , r e g a r d l e s s of the time i n v o l v e d . On t h e o t h e r h a n d , t h e p o p u l a t i o n was l a r g e enough f o r t h e s t u d y t o i n c r e a s e u n d e r s t a n d i n g on s e v e r a l p o i n t s — n a m e l y , t h a t DDT a p p e a r s t o a c c u m u l a t e w i t h age, t h a t t h e l i v e r i s a f f e c t e d , and t h a t serum t r i g l y c e r i d e s and c h o l e s t e r o l l e v e l s a r e r e l a t e d t o DDT l e v e l . F u r t h e r , i n t h e c i t i z e n s o f T r i a n a , l e v e l s o f PCB's i n serum were f o u n d t o c o r r e l a t e p o s i t i v e l y w i t h b l o o d p r e s s u r e c e r t a i n l i v e r f u n c t i o n t e s t s , and c h o l e s t e r o l , i n d e p e n d e n t l y o f age and s e x .


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HAZARDOUS W A S T E SITES


B u c k s and Montgomery C o u n t y , P e n n s y l v a n i a - An E x a m p l e o f a P o t e n t i a l Cohort Study I n May 1979, t h e P e n n s y l v a n i a D e p a r t m e n t o f H e a l t h r e p o r t e d t h a t s e v e r a l p u b l i c and p r i v a t e w a t e r s u p p l i e s i n Montgomery C o u n t y , P e n n s y l v a n i a ( p o p u l a t i o n 627,600) were c o n t a m i n a t e d w i t h t r i c h l o r o e t h y l e n e (TCE). TCE was f o u n d i n 70 o f 100 w e l l - w a t e r s u p p l i e s i n Rahns, P e n n s y l v a n i a . Ten o f t h e s e p o s i t i v e s a m p l e s showed l e v e l s o f TCE i n e x c e s s o f 500 ppb, and 5 s a m p l e s showed TCE i n e x c e s s o f 1,000 ppb. The s u s p e c t e d s o u r c e o f c o n t a m i n a t i o n was a s t e e l w i r e and r o d m i l l t h a t u s e d t h i s compound as a d e g r e a s i n g agent. I m p r o p e r d i s p o s a l r e s u l t e d i n s p i l l s on p l a n t p r o p e r t y , w h i c h l e a c h e d i n t o n e a r b y l a g o o n s and w e l l w a t e r s u p p l i e s . A t a n o t h e r t u b e company, a p i p e f e e d i n g a l a r g e s t o r a g e t a n k o f TCE r u p t u r e d and s p i l l e d o v e r 2,000 g a l l o n s o f TCE i n t o a s t o r m sewer, r e s u l t i n g i n f u r t h e r c o n t a m i n a t i o n o f s u r f a c e and g r o u n d w a t e r . A p p a r e n t l y , h u n d r e d s o f p e o p l e were b e i n g e x p o s e d t o TCE through t h e i r d r i n k i n g water. No a c u t e i l l n e s s had been r e p o r t e d t o be r e l a t e d t o t h e c o n t a m i n a t e d w e l l w a t e r , b u t C o n g r e s s i o n a l r e q u e s t s and a h i g h d e g r e e o f c o n c e r n f r o m c i t i z e n s and l o c a l o f f i c i a l s led to f u r t h e r study. Seven ( 6 % ) o f 117 r e s i d e n t s s c r e e n e d f o r t r i c h l o r o metabol i t e s had d e t e c t a b l e l e v e l s o f t r i c h l o r o e t h a n o l and t r i c h l o r o a c e t i c a c i d i n t h e i r u r i n e . The a p p r o a c h u s e d i n t h i s i n v e s t i g a t i o n was t o s p e c i f i c a l l y compare d e a t h s f r o m l i v e r c a n c e r i n Montgomery C o u n t y w i t h s u c h d e a t h s i n u n e x p o s e d p o p u l a t i o n s w i t h i n t h e same c o u n t y as t h e p r i m a r y c o m p a r i s o n g r o u p and w i t h p o p u l a t i o n s r e p r e s e n t e d by S t a t e and n a t i o n a l d a t a as a l t e r n a t e comparison groups. To a c e r t a i n d e g r e e , t h i s s i t u a t i o n l e n d s i t s e l f t o a p r o s p e c t i v e c o h o r t s t u d y . Had t h i s e p i d e m i o l o g i c t o o l b e e n e m p l o y e d , a d i s c r e t e p o p u l a t i o n o f e x p o s e d , and p e r h a p s u n e x p o s e d , i n d i v i d u a l s w o u l d have been r e g i s t e r e d , w i t h a p p r o p r i a t e i d e n t i f i e r s , and a s s i g n e d a p a r t i c u l a r e x p o s u r e level. T h i s p o p u l a t i o n w o u l d t h e n be a c t i v e l y f o l l o w e d f o r a minimum o f 15 t o 20 y e a r s , and v i t a l s t a t u s and any d e s i g n a t e d a d v e r s e h e a l t h outcomes w o u l d be r e c o r d e d and compared w i t h t h e S t a t e o r n a t i o n a l r a t e s f o r t h e same e v e n t . Obviously, a very l o n g t i m e i s r e q u i r e d and f o l l o w u p i s v e r y e x p e n s i v e . However, i n f o r m a t i o n o b t a i n e d f r o m a p r o s p e c t i v e c o h o r t s t u d y w h i c h i s w e l l d e s i g n e d and m e t i c u l o u s l y c o n d u c t e d c a r r i e s tremendous w e i g h t when one i s b a l a n c i n g i n f o r m a t i o n f r o m l e s s powerful i n v e s t i g a t i v e t o o l s . These p r o s p e c t i v e c o h o r t s t u d i e s must be w e l l t h o u g h t o u t , and t h e r e s h o u l d be a r e a s o n a b l e p o s s i b i l i t y f o r f u n d i n g through the l i f e of the study. An a l t e r n a t i v e t o t h e p r o s p e c t i v e c o h o r t s t u d y i s t h e r e t r o s p e c t i v e cohort study, i n which a defined population w i t h a p a s t e x p o s u r e has an e x i s t i n g m e a s u r a b l e h e a l t h outcome. The p a s t e x p o s u r e needs t o be w e l l documented so t h a t a g i v e n l e v e l o f e x p o s u r e c a n be a s s i g n e d t o e a c h i n d i v i d u a l i n t h e p o p u l a t i o n .



3.

HOUK


31

T h i s , o f c o u r s e , r e q u i r e s a c c u r a t e and a c c e s s i b l e e x p o s u r e r e c o r d s w h i c h c a n be r e a d i l y c o u p l e d t o t h e p o p u l a t i o n b e i n g viewed r e t r o s p e c t i v e l y . Thus, we have t h r e e s i t u a t i o n s i n w h i c h f o u r d i f f e r e n t e p i d e m i o l o g i c a p p r o a c h e s c o u l d be u s e d t o i n v e s t i g a t e h e a l t h e f f e c t s a s s o c i a t e d w i t h h a z a r d o u s w a s t e s i t e s o r any e n v i r o n mental contamination. I n summary, w i t h t h e i n c r e a s i n g p u b l i c c o n c e r n about t o x i c w a s t e s g r o w i n g o u t o f s u c h i n c i d e n t s as L o v e C a n a l , i t i s incumbent upon t h e F e d e r a l Government t o t r y t o answer t h e public's question: "How i s my h e a l t h , and t h a t o f my f a m i l y , a f f e c t e d by e x p o s u r e t o t o x i c w a s t e s ? " I f I c a n l e a v e y o u w i t h o n l y one message, i t i s t h a t t h i s q u e s t i o n i s e x t r e m e l y d i f f i c u l t t o answer. As I have shown t h e e p i d e m i o l o g i s t o r t h e i n v e s t i g a t o r c a n t a k e any one o r s e v e r a l o f v a r i o u s a p p r o a c h e s t o t h e s t u d y o f p o s s i b l e h e a l t h e f f e c t s from exposure t o t o x i c substances a t a g i v e n dump s i t e o r c h e m i c a l s p i l l . Each approach has i t s s t r e n g t h s and w e a k n e s s e s . S i m i l a r l y , e a c h dump s i t e o r s p i l l has i t s p e c u l a r i t i e s . We a r e i n t h e p r o c e s s o f m a t c h i n g what i s known about t h e p r i o r i t y s i t e s t o be c l e a n e d up u n d e r t h e S u p e r f u n d l a w w i t h t h e b e s t a p p r o a c h t o l e a r n i n g about t h e p o s s i b l e h e a l t h e f f e c t s on exposed people l i v i n g around those sites. Once we have s o r t e d o u t t h e s i t e s most l i k e l y t o g i v e us a n s w e r s about h e a l t h e f f e c t s and have d e s i g n e d t h e b e s t r e s e a r c h s t r a t e g y f o r s t u d y i n g e a c h s i t e , we c a n b e g i n o u r work i n t h e field. T h i s work p r o m i s e s t o be d i f f i c u l t and c o m p l e x , b u t we hope i t w i l l r e s o l v e t h e s e p u b l i c h e a l t h c o n c e r n s . Literature 1.

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RECEIVED July 16,

1982.


Determining the Impacts on Human Health Attributable to

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