The Toxicological and Epidemiological Effects of Pesticide

23

Downloaded by UNIV OF MASSACHUSETTS AMHERST on May 30, 2018 | https://pubs.acs.org Publication Date: July 17, 1986 | doi: 10.1021/bk-1986-0315.ch023

The Toxicological and Epidemiological Effects of Pesticide Contamination in California Ground Water Peter E. Berteau and David P. Spath California State Department of Health Services, Berkeley, CA 94704

The contamination of California groundwater by pesticides is a problem which is becoming more evident as monitoring programs are being implemented. In a recent study, 54 pesticides were detected in 2,893 wells in the State. Among the most pervasive toxic pesticide chemicals found have been 1,2-dibromo-3chloropropane (DBCP), ethylene dibromide (EDB) and 1,2-dichloropropane (1,2-D). DBCP alone has resulted in the closure of about 1,000 drinking water wells. Toxicological evidence from animal studies indicate that these substances are carcinogenic and in one epidemiological study there was an excess of stomach cancer in census tracts with high DBCP content. An acutely toxic chemical, aldicarb, has also been detected in a number of wells in the State. Adverse reproductive effects and neurotoxicity occur with several of these pesticides. Because o f the importance o f a g r i c u l t u r e to the C a l i f o r n i a e c o n o m y , w i d e s p r e a d use of p e s t i c i d e s has o c c u r r e d d u r i n g the p a s t f o u r decades. While t h i s use has l e d t o c o n c e r n s a b o u t p o i s o n i n g s o f f a r m w o r k e r s , q u e s t i o n s o f r e s i d u e s i n food and the e s t a b l i s h m e n t o f s a f e l e v e l s , i t has o n l y r e c e n t l y been r e c o g n i z e d t h a t h a z a r d s from t h e u s e o f p e s t i c i d e s may o c c u r from s o u r c e s o t h e r than o c c u p a t i o n o r food s u p p l y . Now i t i s e m e r g i n g t h a t t h e c o n t a m i n a t i o n o f g r o u n d w a t e r i n C a l i f o r n i a by p e s t i c i d e s and i n d u s t r i a l c h e m i c a l s i s a problem o f p r e v i o u s l y u n f o r e s e e n p r o p o r t i o n s . In t h i s c o n n e c t i o n , i t m u s t be r e c o g n i z e d t h a t a b o u t 43% o f the s t a t e o f C a l i f o r n i a o r a b o u t 10 m i l l 1 on p e o p l e r e l y on g r o u n d w a t e r f o r t h e i r water supplies. In T a b l e I an Idea o f the scope o f the p r o b l e m o f p e s t i c i d e c o n t a m i n a t i o n 1n groundwater i s g i v e n by l i s t i n g some o f the p e s t i c i d e c h e m i c a l s which a r e b e i n g most commonly e n c o u n t e r e d . It is only a p a r t i a l l i s t b u t r e p r e s e n t s the most commonly o c c u r r i n g c h e m i c a l s , i n p a r t i c u l a r those a r i s i n g from a g r i c u l t u r a l u s e , and the ones which a r e c o n s i d e r e d i n t h i s s e c t i o n . 0097-6156/ 86/ 0315-0423S06.00/ 0 © 1986 American Chemical Society

Garner et al.; Evaluation of Pesticides in Ground Water ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

424 Table

E V A L U A T I O N O F P E S T I C I D E S IN G R O U N D W A T E R

I.

Major P e s t i c i d e s

Encountered i n C a l i f o r n i a

S o i l Fumigants (Nematocides) l,2-Dibromo-3-chloropropane E t h y l e n e d i b r o m i d e (EDB) 1,2-Dichloropropane (1,2-D)

Groundwater

(DBCP)


Insecticides A l d i c a r b (Temik) Herbicides Atrazine Simazine Fungicides P e n t a c h l o r o p h e n o l (PCP) D i t h i o c a r b a m a t e s ( e . g . , Maneb, Z i r a m ,

Thiram)

I n 1 9 8 4 t h e C a l i f o r n i a S t a t e Water Resources C o n t r o l Board (SWRCB) r e p o r t e d t h a t d u r i n g t h e p a s t 12 y e a r s p e s t i c i d e contaminants h a v e b e e n f o u n d i n 2,893 w e l l s ( 1 , 2 ) . A l t h o u g h 54 d i f f e r e n t p e s t i c i d e s have been d e t e c t e d i n these weTls a b o u t 85% o f t h e c o n t a m i n a t i o n has been caused by l , 2 - d i b r o m o - 3 - c h l o r o p r o p a n e (DBCP), a s o i l f u m i g a n t t h a t was banned seven y e a r s ago b u t t h a t is s t i l l b e i n g d e t e c t e d i n i n c r e a s i n g amounts i n w e l l s . F i g u r e 1 shows a map o f C a l i f o r n i a g i v i n g the l o c a t i o n s o f the m o s t a b u n d a n t l y o c c u r r i n g p e s t i c i d e s which a r e b e i n g found i n groundwater. Of c o u r s e , the c o n t a m i n a t i o n i s not l i m i t e d to a g r i c u l t u r a l c h e m i c a l s such as p e s t i c i d e s ; i n d u s t r i a l c h e m i c a l s have c o n t r i b u t e d a l m o s t e q u a l l y to o v e r a l l g r o u n d w a t e r contamination, however, i t 1s p o l l u t i o n by p e s t i c i d e s which we a r e concerned w i t h here. Most o f t h i s c o n t a m i n a t i o n a r i s e s from the use o f p e s t i c i d e s i n a g r i c u l t u r e b u t some p e s t i c i d e c o n t a m i n a t i o n o f g r o u n d w a t e r has a r i s e n i n the same manner as from i n d u s t r i a l c h e m i c a l s , namely from c a r e l e s s use and poor housekeeping 1n i n d u s t r i a l p l a n t s . The c o n t a m i n a t i o n by p e n t a c h l o r o p h e n o l ( P C P ) 1s thought to a r i s e from the use o f t h i s chemical f o r t r e a t i n g p o l e s 1n m a n u f a c t u r i n g p l a n t s . T h e p r e s e n c e o f p e s t i c i d e s and o t h e r c h e m i c a l s i n groundwater has d e s t r o y e d the l o n g h e l d b e l i e f t h a t g r o u n d w a t e r i s Immune t o chemical p o l l u t i o n because s o i l would f i l t e r o u t or break down the chemicals. A l t h o u g h the c o n t a m i n a t i o n has p r o b a b l y been p r e s e n t f o r years, l a b o r a t o r y t e c h n i q u e s and equipment to d e t e c t low l e v e l s o f the complex c h e m i c a l s have o n l y been d e v e l o p e d i n r e c e n t years. S t a t e p r o g r a m s s p e c i f i c a l l y d e s i g n e d to p r o t e c t water from t o x i c s u b s t a n c e s began l e s s than 10 y e a r s a g o . Types o f P e s t i c i d e s which Contaminate

Groundwater

By f a r the most u b i q u i t o u s p o l l u t a n t s w h i c h a r e contaminating g r o u n d w a t e r a r e t h e s o i l f u m l g a n t s , p a r t i c u l a r l y DBCP, b u t a l s o ethylene dibromide (EDB) and 1 , 2 - d i c h l o r o p r o p a n e (1,2-D). Organophosphorus i n s e c t i c i d e s have n o t been found to any a p p r e c i a b l e e x t e n t i n groundwater p r o b a b l y because t h e y a r e u s u a l l y readily



BE RTE AU A N D

F i g u r e 1.

SPATH

Pesticide

Contamination

in California

P e s t i c i d e Contamination - C a l i f o r n i a

Ground

Water

Groundwaters.



426


broken down i n t o p h o s p h o r i c a c i d d i a l k y l e s t e r s and l o s e t h e i r t o x i c character. A r e l a t e d c l a s s o f compounds, the c a r b a m a t e s , w h i c h owe t h e i r t o x i c a c t i o n s to i n h i b i t i o n o f c h o l i n e s t e r a s e , are w i d e l y used in California. One o f t h e s e i n p a r t i c u l a r i s being found in g r o u n d w a t e r i n many p a r t s o f the c o u n t r y . T h i s i s the h i g h l y t o x i c oxime carbamate a l d i c a r b (Temik) w h i c h , i n C a l i f o r n i a , has been f o u n d a l o n g w i t h i t s s u l f o x i d e i n the extreme N o r t h e r n p a r t o f the s t a t e c l o s e to the Oregon b o r d e r . H e r b i c i d e s have a l s o been found i n water a l t h o u g h t h e i r o c c u r r e n c e i s more o f t e n seen i n s u r f a c e w a t e r s a r i s i n g from d i r e c t runo f f from a g r i c u l t u r a l use as i n r i c e growing. C e r t a i n o f the t r i a z i n e h e r b i c i d e s have been found i n w e l l s i n N o r t h e r n C a l i f o r n i a a n d i n t h e L o s Angeles B a s i n . F u n g i c i d e s have a l s o been found i n groundwater. T h e o c c u r r e n c e o f t h e wood p r e s e r v a t i v e pent a c h l o r o p h e n o l (PCP) has a l r e a d y been m e n t i o n e d . More r e c e n t l y the metal c o n t a i n i n g d i t h i o c a r b a m a t e s have been e n c o u n t e r e d . Many o f these a r e the heavy metal s a l t s o f e t h y l e n e - b i s - d i t h i o c a r b a m i c a c i d . P e s t i c i d e chemicals are r e l a t e d to s p e c i f i c toxic effects. W i t h the s o i l f u m i g a n t s , r e p r o d u c t i v e e f f e c t s and c a r c i n o g e n i c i t y a r e the main c o n c e r n . With the c a r b a m a t e s , such as a l d i c a r b , we a r e c o n c e r n e d w i t h an a c u t e t o x i c e f f e c t on the p e r i p h e r a l nervous system. With p e n t a c h l o r o p h e n o l high a c u t e t o x i c i t y and t h e potent i a l f o r c a r c i n o g e n i c i t y a r e the main c o n c e r n s . Soil

Fumigants

A s a l r e a d y m e n t i o n e d , t h r e e s o i l f u m i g a n t s , shown below, a l o n g w i t h t h e i r chemical s t r u c t u r e s , a r e p r e s e n t i n g p r o b a b l y the greatest p r o b l e m o f g r o u n d w a t e r c h e m i c a l c o n t a m i n a t i o n by p e s t i c i d e s i n California. Table

II.

Chemical

Structures

1,2-Dibromo-3-chioropropane

1,2-Dichloropropane

2

of Soil

Fumigants

(DBCP)

(1,2-D)

2

Ethylene dibromide

(EDB)

T h e s e t h r e e compounds a r e h a l o g e n a t e d as a r e most o f the i n d u s t r i a l groundwater p o l l u t a n t s . They are w e l l known a s being h e p a t o t o x i c a n d h a v e been demonstrated to cause c a n c e r i n one or



23.

BE RTE AU A N D SPATH

Pesticide

Contamination

in California

Ground

Water

All

more s p e c i e s o f a n i m a l . Two o f t h e s e , DBCP and EDB, a r e b r o m i n a t e d c o m p o u n d s a n d these a r e the more p o t e n t animal c a r c i n o g e n s , 1,2-D b e i n g o n l y weakly c a r c i n o g e n i c . Most s o i l f u m i g a n t s a r e injected i n t o the s o i l up t o a f o o t i n depth and some o f the chemical i s c a r r i e d downward i n t o w a t e r - b e a r i n g s t r a t a ( a q u i f e r s ) by i r r i g a t i o n and r a i n w a t e r . DBCP h a s b e e n the most p e r v a s i v e o f these s o i l f u m i g a n t s because o f i t s p a s t e x t e n s i v e use s t a r t i n g in the late 1950's. N e a r l y one m i l l i o n pounds per y e a r were b e i n g used by the time DBCP was banned i n 1977. I n t e r e s t i n g l y , more o f t h i s c h e m i c a l i s s h o w i n g up now than when i t f i r s t began to be d e t e c t e d i n w e l l s i n 1979. M i l l i o n s of d o l l a r s have a l r e a d y b e e n s p e n t to drill w a t e r - w e l l s i n t o d e e p e r , u n t a i n t e d a q u i f e r s i n F r e s n o county i n the C e n t r a l V a l l e y where most o f the DBCP c o n t a m i n a t i o n h a s occurred. H o w e v e r , as o f November, 1984, 1,473 w e l l s had been r e n d e r e d unusea b l e f o r d r i n k i n g o r c o o k i n g because they exceeded the a c t i o n level o f 1 ppb e s t a b l i s h e d by the s t a t e o f C a l i f o r n i a ( 3 ) . (An a c t i o n l e v e l i s a concentration a t which the C a l i f o r n i a department of H e a l t h S e r v i c e s recommends, t h a t f o r h e a l t h p r o t e c t i o n , the water n o t be used f o r d r i n k i n g o r c o o k i n g ) . I f DBCP has a h a l f l i f e in s o i l s o f more than 100 y e a r s , as some o f the l i t e r a t u r e i n d i c a t e s , (£) i t s p e r s i s t e n c e i s going to be a p r o b l e m . The t o x i c o l o g i c a l e f f e c t s o f DBCP were i n v e s t i g a t e d i n r a t s i n the l a t e 1950's n o t long a f t e r i t became c o m m e r c i a l l y a v a i l a b l e {5). At that time, the t e s t i n g requirements f o r r e g i s t r a t i o n of pest i c i d e s were v e r y much more l i m i t e d than they a r e today and a d v e r s e f i n d i n g s were o f t e n d i s r e g a r d e d . The study i n c l u d e d s t a n d a r d s k i n and eye i r r i t a t i o n s t u d i e s a s w e l l as r e p e a t e d v a p o r inhalation s t u d i e s on r a t s , r a b b i t s and guinea p i g s . The i n h a l a t i o n exposure c o n c e n t r a t i o n s were 0 ( c o n t r o l ) , 5, 10, 20 and 40 ppm f o r t h e rat. Exposure times were 7 hours a day, 5 days a week f o r a t o t a l o f 50 e x p o s u r e s (10 w e e k s ) . T h e m o s t s i g n i f i c a n t f i n d i n g was t h a t a t the l o w e s t l e v e l , 5 ppm, there was a s p e c i f i c h i s t o l o g i c a l a l t e r a t i o n i n the t e s t e s in the male r a t . I t was r e p o r t e d t h a t t e s t i c u l a r w e i g h t was reduced to 50% o f normal i n h a l f the r a t s a l t h o u g h t h i s r e d u c t i o n was n o t statistically s i g n i f i c a n t because o f the l a r g e i n t e r n a l v a r i a t i o n w i t h i n the g r o u p . Changes were a l s o r e p o r t e d i n k i d n e y , l i v e r and b r o n c h i o l e s a n d w e i g h t g a i n was s i g n i f i c a n t l y r e d u c e d . At higher c o n c e n t r a t i o n s the e f f e c t i n the t e s t e s o f r a t s was particularly severe, resulting i n atrophy, degenerative changes, r e d u c t i o n of s p e r m a t o g e n s i s and the development o f abnormal sperm. Less extens i v e s t u d i e s were done w i t h r a b b i t s and guinea p i g s b u t d e c r e a s e d t e s t i c u l a r w e i g h t was r e p o r t e d i n both these s p e c i e s a t t h e only c o n c e n t r a t i o n a d m i n i s t e r e d , 12 ppm. A 90-day f e e d i n g study was a l s o c o n d u c t e d w i t h r a t s a t dose l e v e l s r a n g i n g from 5 to 1,350 ppm. No m e n t i o n was made o f any t e s t i c u l a r e f f e c t i n t h i s study and 150 ppm was judged to be a n o - e f f e c t l e v e l . I t i s n o t known i f t h e testes were examined. In g e n e r a l t h i s s t u d y , r e p o r t e d i n 1961, i s w e l l c o n d u c t e d a n d t h e d a t a a r e s t i l l u s e f u l f o r the s p e c i f i c purposes o f r i s k a s s e s s ment t o d a y . The e f f e c t on the t e s t e s a t t h e l o w e s t inhalation e x p o s u r e i s mentioned s e v e r a l times and the a u t h o r s recommended an exposure l e v e l below 1 ppm i f p r o l o n g e d exposure i s l i k e l y . No e f f o r t was made to r e p e a t the exposure study a t lower l e v e l s i n o r d e r



428


to determine a n o - e f f e c t l e v e l a s would be r e q u i r e d t o d a y . More i m p o r t a n t , however, the study was i g n o r e d f o r a b o u t 15 y e a r s u n t i l the appearance o f the w e l l p u b l i c i z e d r e p o r t o f s t e r i l i t y i n male workers a t a DBCP m a n u f a c t u r i n g p l a n t i n L a t h r o p , C a l i f o r n i a ( 6 K S i n c e t h a t t i m e , e x t e n s i v e t o x i c o l o g i c a l and e p i d e m i o l o g i c a l s t u d i e s have been conducted w i t h DBCP. These i n c l u d e three s t u d i e s on h u m a n s . One was a s t u d y on p l a n t w o r k e r s . O f 25 n o n v a s e c t o m i z e d men, i n those who had been exposed to DBCP f o r t h r e e y e a r s , sperm c o u n t s w e r e d r a s t i c a l l y r e d u c e d i n 11 men (< 1 million/ml) a n d n i n e o f these had no d e t e c t a b l e sperm c e l l s . Of those who had o n l y a s h o r t d u r a t i o n o f e x p o s u r e , sperm c o u n t s w e r e normal (> 40 m i l l i o n / m l ) (7). In a n o t h e r s t u d y , an i n c r e a s e i n sperm c e l l s c o n t a i n i n g two Y chromosomes was noted (8). The third human study was an e p i d e m i o l o g i c a l study i n v o l v i n g s u b j e c t s exposed t o w e l l - w a t e r c o n t a i n i n g DBCP and w i l l be d i s c u s s e d l a t e r . Since t h e 1 9 6 1 s t u d y , DBCP has been t e s t e d i n s t a n d a r d l o n g term r a t and mouse b i o a s s a y s . These s t u d i e s a r e r e v i e w e d i n the monograph on DBCP i s s u e d by the I n t e r n a t i o n a l Agency f o r Research on Cancer ( 9 h In the s t u d i e s c o n d u c t e d f o r t h e N a t i o n a l Cancer Institute, DBCP was h i g h l y c a r c i n o g e n i c a t the l o w e s t doses a d m i n i s t e r e d ( a b o u t 10 mg/kg/day f o r mice and 15 mg/kg/day f o r r a t s ) . Tumors in b o t h s p e c i e s r e s u l t e d in early m o r t a l i t y . Tumors i n g e n e r a l were squamous c e l l c a r c i n o m a s o f t h e f o r e s t o m a c h w h i c h m e t a s t a s i z e d i n t o t h e a b d o m i n a l v i s c e r a and l u n g s . Testicular a t r o p h y was a l s o noted i n the r a t s i n these s t u d i e s . A high inc i d e n c e o f adenocarcinomas o f the mammary g l a n d was seen 1n female r a t s exposed to both the low and high dose l e v e l s ( 1 0 ) . In s t u d i e s conducted a t the same l a b o r a t o r y T u t sponsored by the Dow Chemical Company ( 1 1 ) , DBCP was I n c o r p o r a t e d i n t o t h e diet o f r a t s and m i c e . D i e t a r y " T e v e l s were a d j u s t e d so t h a t both s p e c i e s r e c e i v e d 0 ( c o n t r o l ) , 0 . 3 , 1.0 and 3.0 m g / k g / d a y . T h e r e w e r e 60 r a t s p e r g r o u p which r e c e i v e d the t r e a t e d d i e t f o r 2 y e a r s and 50 mice per group which r e c e i v e d the d i e t f o r 1 1/2 y e a r s . In the r a t s a t u m o r l g e n i c e f f e c t was s e e n i n the k i d n e y s and n o n - g l a n d u l a r r e g i o n o f the stomach w i t h the g r e a t e s t i n c i d e n c e o f n e o p l a s i a b e i n g o b s e r v e d i n t h e high dose group o f r a t s , w i t h fewer tumors a t the mid-dose l e v e l and o n l y r a r e l e s i o n s a t t h e l o w - d o s e l e v e l . In m i c e , a d o s e r e l a t e d i n c r e a s e i n the i n c i d e n c e o f stomach n o d u l e s was noted In a l l treated animals s a c r i f i c e d at termination. H i s t o l o g i c a l e x a m i n a t i o n o f c o n t r o l and high dose groups r e v e a l e d a h i g h i n c i d e n c e o f t r e a t m e n t r e l a t e d n e o p l a s i a (squamous c e l l p a p i l lomas and c a r c i n o m a s ) i n the n o n - g l a n d u l a r r e g i o n o f the stomach. In an i n i t i a t i o n - p r o m o t i o n s k i n b i o a s s a y conducted a t New Y o r k U n i v e r s i t y Medical C e n t e r ( 1 2 ) , 69.0 mg o f DBCP was a p p l i e d to the s k i n o f female m i c e , followeoHBy r e p e a t e d a p p l i c a t i o n o f phorbol m y r i s t a t e a c e t a t e t h r e e times weekly f o r 499 d a y s . The most s i g n i f i c a n t f i n d i n g f r o m t h i s s t u d y was t h e o c c u r r e n c e o f lung p a p i l l o m a s and squamous c e l l carcinomas o f the forestomach i n d i c a t i n g t h a t the o c c u r r e n c e o f stomach tumors i n the o r a l s t u d i e s may be s y s t e m i c and n o t merely r e l a t e d to an I r r i t a n t e f f e c t a t the s i t e o f application. B a s e d u p o n t h e s e d a t a accumulated from animal s t u d i e s , the E n v i r o n m e n t a l P r o t e c t i o n A g e n c y ' s C a r c i n o g e n Assessment Group ( C A G )



23.


Pesticide

Contamination

in California

Ground

Water

429

p e r f o r m e d a r i s k assessment f o r l i f e t i m e exposure to DBCP i n d r i n k i n g water ( 1 3 ) . A t a c o n c e n t r a t i o n o f 0.005 ppb the r i s k o f excess c a n c e r c a s e s would be 1.1 i n 1 m i l l i o n ; a t 0.05 ppb, 11 i n 1 m i l l i o n and a t 1.0 ppb, 220 i n 1 m i l l i o n . Based on the a v a i l a b l e evidence on the c a r c i n o g e n i c i t y , s e n s i t i v i t y o f a n a l y t i c a l methods, i m p a c t on water d e l i v e r y c a p a b i l i t i e s , and a d d i t i o n a l f a c t o r s the California D e p a r t m e n t o f H e a l t h S e r v i c e s adopted an a c t i o n l e v e l o f 1 ppb f o r c o n t a m i n a t i o n o f d o m e s t i c d r i n k i n g water by DBCP ( 2 ) . T h i s policy r e c o m m e n d s t h a t c o n t a m i n a t i o n o f water s u p p l i e s a t t h i s l e v e l or above i n d i c a t e s t h a t the water s h o u l d n o t be u s e d . A s t u d y c o n d u c t e d by t h e C a l 1 f o r n i a Department o f H e a l t h S e r v i c e s i s the o n l y known a c t u a l e p i d e m i o l o g i c a l study that has b e e n c o n d u c t e d on p e o p l e exposed to water c o n t a m i n a t e d w i t h p e s t i c i d e s (14). P o p u l a t i o n groups i n an area o f C e n t r a l C a l i f o r n i a , F r e s n o c o u n t y , w h e r e w e l l s had been c o n t a m i n a t e d w i t h DBCP were studied f o r cancer m o r t a l i t y . The v a r i o u s census t r a c t s under s t u d y w e r e d i v i d e d i n t o low ( 0 . 0 - 0 . 0 5 p p b ) , medium ( 0 . 0 5 - 1 ppb) and h i g h (> 1 ppb) l e v e l s o f DBCP i n the d r i n k i n g w a t e r . The c o h o r t s were examined f o r those c a n c e r s seen i n a n i m a l s which a r e a s s o c i a t e d w i t h I n g e s t i o n o f DBCP, namely c a n c e r s o f the stomach, e s o p h a g u s , 11 v e r , k i d n e y and female b r e a s t . I n c i d e n c e s o f lymphoid leukemia were a l s o I n c l u d e d because o f a n e c d o t a l r e p o r t s o f t h i s k i n d o f c a n c e r i n the exposed p o p u l a t i o n . The r e s u l t s o f the s t u d i e s r e v e a l e d a s t a t i s t i c a l t r e n d (JD < 0.005) i n male stomach c a n c e r deaths w i t h i n c r e a s i n g DBCP c o n c e n t r a t i o n s 1n d r i n k i n g water by census t r a c t . A weaker t r e n d was seen w i t h kidney c a n c e r 1n females (£ < 0.01) and l y m p h o i d leukemia i n males (p < 0 . 0 1 ) . The r e s u l t s o f t h i s e p i d e m i o l o g i c a l s t u d y , m u s t be regarded with c a u t i o n . One p l a u s i b l e e x p l a n a t i o n i s t h a t DBCP does t r u l y i n c r e a s e the r a t e o f stomach c a n c e r and o t h e r c a n c e r s . However, o t h e r v a r i a b l e s may be r e s p o n s i b l e . The census t r a c t s c o n t a i n i n g h i g h l e v e l s o f DBCP w e r e m o r e r u r a l , m o r e H i s p a n i c a n d o f lower socioeconomic s t a t u s t h a n w e r e t h e l o w DBCP t r a c t s . Low s o c i o e c o n o m i c s t a t u s has been a s s o c i a t e d w i t h gastrointestinal c a n c e r s b u t n o t lymphoid l e u k e m i a . Mexican-American e t h n i c i t y may be a r i s k f a c t o r i n stomach c a n c e r s . Other common r i s k f a c t o r s such a s s m o k i n g and a l c o h o l consumption s h o u l d be c o n s i d e r e d . In a d d i t i o n , p e r s o n s l i v i n g i n r u r a l a r e a s may have more exposure to o t h e r p e s t i c i d e s some o f which a r e c a r c i n o g e n i c . Another i m p o r t a n t s o i l f u m l g a n t i s e t h y l e n e d i b r o m i d e (EDB) and t h e u s e o f t h i s c h e m i c a l was s u s p e n d e d i n s e v e r a l c o u n t i e s 1n C e n t r a l C a l i f o r n i a when contaminated d o m e s t i c w e l l s were e n c o u n t e r e d i n the San J o a q u i n V a l l e y . L a t e r i t was banned n a t i o n a l l y by EPA a s a s o i l fumigant. L e v e l s i n C a l i f o r n i a w a t e r - w e l l s ranged from 70 t o 4800 p p t ( 1 5 , 1 8 ) . S t u d i e s i n a n i m a l s I n d i c a t e t h a t i s has a similar toxicôlogical profile to DBCP. The C a l i f o r n i a State Department o f H e a l t h S e r v i c e s has recommended t h a t p e r s o n s w i t h EDBc o n t a m i n a t e d w e l l s s w i t c h to o t h e r d r i n k i n g w a t e r s u p p l i e s . The a v a i l a b l e I n f o r m a t i o n on the t o x i c o l o g y o f EDB has been e x t e n s i v e l y summarized b o t h by the I n t e r n a t i o n a l Agency f o r R e s e a r c h on C a n c e r ( 1 6 ) a n d m o r e r e c e n t l y by t h e 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 ΑάΤτΠ n i s t r a t i on (0SHA) as a n o t i c e o f proposed r u l e making f o r an o c cupational workplace exposure c r i t e r i o n (17) and by a l s o the C a l i f o r n i a Department o f H e a l t h S e r v i c e s a s a basTi" o f r e c o m m e n d i n g


EVALUATION OF PESTICIDES IN GROUND WATER


430

an a m b i e n t a i r s t a n d a r d ( 1 8 ) . In both mice and r a t s g i v e n EDB by gavage, doses a s low a s 60 mg7kg/day f o r mice and 40 m g / k g / d a y f o r r a t s r e s u l t e d i n squamous c e l l carcinomas o f the f o r e s t o m a c h which began to appear e a r l y i n the s t u d i e s . The female r a t s a l s o had s i g n i f i c a n t increases i n hepatocellular carcinomas. Both sexes o f mice had s t a t i s i c a l l y s i g n i f i c a n t i n c r e a s e s i n a l v e o l a r / b r o n c h i o l a r adenomas and t h e r e were s i g n i f i c a n t i n c r e a s e s i n hemangiosarcomas i n the male r a t s . S i m i l a r i n c i d e n c e s o f c a n c e r were seen w i t h r a t s and mice i n inhalation studies. T e s t i c u l a r d e g e n e r a t i o n was a l s o seen i n the male a n i m a l s i n these s t u d i e s . EDB w a s a l s o shown t o be mutagenic i n s e v e r a l i n v i v o and i n v i t r o s y s t e m s . No e p i d e m i o l o g i c a l s t u d i e s a r e r e p o r t e d on p e r s o n s e x p o s e d t o d r i n k i n g water c o n t a i n i n g EDB. In one p u b l i s h e d e p i d e m i o l o g i c a l r e p o r t i n v o l v i n g 161 workers o c c u p a t i o n a l l y exposed t o EDB i t was c o n c l u d e d t h a t t h e s t u d y c a n n e i t h e r r u l e o u t nor e s t a b l i s h EDB as a human c a r c i n o g e n because o f the small s i z e o f the p o p u l a t i o n s t u d i e d . R i s k assessments conducted on the b a s i s o f animal s t u d i e s e s t i m a t e a l i f e t i m e e x c e s s c a n c e r r i s k from i n h a l a t i o n exposure to EDB t o r a n g e f r o m 0 . 0 6 to 67 p e r 1000 f o r 0 . 1 ppm and 160 t o 1000 p e r 1000 f o r 20 ppm depending upon the r i s k a s s e s s m e n t models used ( 1 7 , 18). One s u b s t i t u t e f o r DBCP i s 1 , 2 - d i c h l o r o p r o p a n e ( 1 , 2 - D ) . This c o m p o u n d h a s b e e n f o u n d i n s e v e r a l w e l l s i n the extreme N o r t h e r n p a r t o f C a l i f o r n i a a n d a l s o i n an a r e a b e t w e e n F r e s n o a n d Bakersfield. In p a r t i c u l a r , 1,2-D has been found i n a r e a s where the water table i s shallow. U s u a l l y the c o n c e n t r a t i o n s a r e a r o u n d 0 . 1 t o 5 p p b b u t l e v e l s a s high a s 30 ppb have been e n c o u n t e r e d ( 1 9 ) . S t u d i e s sponsored by the N a t i o n a l T o x i c o l o g y Program have I n d i c a t e d possible c a r c i n o g e n i c a c t i v i t y 1n l a b o r a t o r y a n i m a l s ( 2 0 ) . The m a n u f a c t u r e r o f 1,2-D has v o l u n t a r i l y withdrawn D-D, the f o r m u l a t i o n t h a t c o n t a i n s 1,2-D, from s a l e i n C a l i f o r n i a . —

Insecticides T h e o n l y p r i m a r i l y i n s e c t i c i d a l chemical a r i s i n g from a g r i c u l t u r a l use which has b e e n e n c o u n t e r e d i n C a l i f o r n i a groundwater is aldicarb. L e v e l s o f 6 to 26 ppb have been r e p o r t e d i n some w e l l s i n N o r t h e r n c o u n t i e s o f the s t a t e ( 2 1 ) . The presence o f a l d i c a r b i s a p r o b l e m i n many o t h e r p a r t s o f t h e c o u n t r y a n d i t s f a t e i n groundwater i s d i s c u s s e d i n the s e c t i o n o f t h i s s y m p o s i u m dealing w i t h f i e l d monitoring. The chemical s t r u c t u r e o f a l d i c a r b 1s shown below.

CH

CH

Ο

I

II

-S-C-CH=N-0-C-NHCH £H

3

Aldicarb T h e t o x i c o l o g y o f t h i s compound has been summarized by the N a t i o n a l Academy o f S c i e n c e s / N a t i o n a l R e s e a r c h C o u n c i l ( 2 2 ) a n d by t h e W o r l d H e a l t h O r g a n i z a t i o n E x p e r t Group on P e s t i c ï c l ê R e s i d u e s (23). The main concern a b o u t t h i s compound i s i t s very h i g h acute


23.

Pesticide


Contamination

in California

Ground

Water

431

toxicity. I t i s a p o t e n t c h o l i n e s te r a s e i n h i b i t o r w i t h an LD50 to the r a t o f l e s s than 1 mg/kg. However, the compound h a s n o t b e e n r e p o r t e d t o d i s p l a y a n y a d v e r s e l o n g term e f f e c t s a t s u b - l e t h a l doses. I t i s n o t c a r c i n o g e n i c , t e r a t o g e n i c , nor does i t d i s p l a y any a d v e r s e e f f e c t s on r e p r o d u c t i o n i n a t h r e e - g e n e r a t i o n f e e d i n g s t u d y . Based on s t u d i e s conducted w i t h r a t s a n d d o g s , the World Health O r g a n i z a t i o n e s t a b l i s h e d an a c c e p t a b l e d a i l y i n t a k e (ADI) o f 0.005 mg/kg f o r a l d i c a r b ( 2 3 ) . T h e N a t i o n a l A c a d e m y o f S c i e n c e / N a t i o n a l Research C o u n c i l (NAS/NRC) g i v e s a suggested no a d v e r s e response l e v e l (SNARL) for aldicarb i n d r i n k i n g water o f 7 ppb ( 2 2 ) . The USA 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) has recommended a~ïïealth a d v i s o r y l e v e l of 10 p p b . The C a l i f o r n i a Department o f H e a l t h S e r v i c e s has adopted E P A ' s l i m i t a s an a c t i o n l e v e l ( 2 4 ) .


-

Herbicides The t r i a z i n e h e r b i c i d e s , a t r a z i n e and s i m a z i n e have r e c e n t l y been e n c o u n t e r e d i n g r o u n d w a t e r i n N o r t h e r n C a l i f o r n i a and i n the Los A n g e l e s B a s i n a t l e v e l s r a n g i n g f r o m 0 . 4 t o 2 . 0 ppb ( 2 5 . ) · The c h e m i c a l s t r u c t u r e s o f these two compounds a r e shown below: CI

Simazine

The t o x i c o l o g y o f these compounds has been s u m m a r i z e d by t h e National Academy o f S c i e n c e s / N a t i o n a l Research Council (26). A t r a z i n e i s s l i g h t l y t o x i c when g i v e n i n s i n g l e o r a l d o s e s t o rats and s i m a z i n e i s p r a c t i c a l l y n o n - t o x i c under the same c o n d i t i o n s . The compounds have been s u b m i t t e d to t e s t s f o r c a r c i n o g e n i c i t y to


EVALUATION OF PESTICIDES IN GROUND WATER

432

m i c e a t t h e h i g h e s t t o l e r a t e d doses and were determined n o t to be t u m o r i g e n i c under the c o n d i t i o n s o f the t e s t s . S i m a z i n e a t 50 a n d 100 ppb i n the r a t had no a d v e r s e e f f e c t s on r e p r o d u c t i o n o f r a t s o r t h e i r o f f s p r i n g o v e r three g e n e r a t i o n s . The NAS/NRC r e c o m m e n d s a n a c c e p t a b l e d a i l y i n t a k e o f 0.0215 mg/kg and 0.215 mg/kg f o r a t r a z i n e and s i m a z i n e r e s p e c t i v e l y . Recommended l e v e l s i n d r i n k i n g water a r e 7 . 5 ppb f o r a t r a z i n e and 75.25 ppb f o r s i m a z i n e .


Fungicides T h e o c c u r r e n c e o f the wood p r e s e r v a t i v e p e n t a c h l o r o p h e n o l ( P C P ) , i n groundwater 1s thought to a r i s e from the m a n u f a c t u r i n g p r o c e s s i n v o l v i n g treatment o f p o l e s . The chemical s t r u c t u r e 1s shown below OH CI

CI

P e n t a c h l o r o p h e n o l (PCP) PCP i s a h i g h l y t o x i c compound p r o d u c i n g a v a r i e t y o f t o x i c e f f e c t s , I n p a r t i c u l a r h i s t o p a t h o l o g l c a l changes i n the l i v e r . The compound contains impurities of chlorinated d i b e n z o d i o x l n s , but recently m a n u f a c t u r e d b a t c h e s do n o t have d e t e c t a b l e l e v e l s o f the h l q h l y toxic 2,3,7,8-tetrachlorodibenzo-p-dioxin. F o r c h e m i c a l l y p u r e PCP a no e f f e c t l e v e l o f 3 mg/kg7day was e s t i m a t e d i n the r a t . The NAS/NRC recommend an ADI o f 0.003 mg/kg and a suggested no a d v e r s e e f f e c t l e v e l i n d r i n k i n g w a t e r o f 21 ppb ( 2 7 ) . Another c l a s s o f f u n g i c i d e s r e c e n t l y e n c o u n t e r e d 1n groundwater a r e t h e e t h y l e n e - b 1 s - d i t h i o c a r b a m a t e s (EBDC's) ( 2 8 ) . These compounds a r e o f t e n s a l t s o f m e t a l s a n d t h e n a m e s a n d c h e m i c a l s t r u c t u r e s o f some o f them a r e shown:

CH

- NH - C - S-Na

CH.L

- NH - C -

CH

2

- NH - C - S,

II s Nabam

Maneb CH, S CH. Ethylenethiourea


23.

BE RTE AU AND SPATH

Pesticide

Contamination

in California

Ground

Water

433

The main t o x i c o l o g i c a l concern a b o u t t h i s c l a s s o f compounds i s t h e i r b r e a k d o w n to the g o i t r o g e n e t h y l e n e t h i o u r e a ( E T U ) , a p o t e n t animal c a r c i n o g e n ( 2 9 ) . T e s t i n g f o r ETU i n groundwater i s p r e s e n t l y being conducted.


Conclusions An a t t e m p t h a s b e e n made to g i v e an overview o f the s i g n i f i c a n t t o x i c o l o g i c a l and e p i d e m i o l o g i c a l e f f e c t s t h a t have b e e n reported f r o m those p e s t i c i d e s which a r e b e i n g e n c o u n t e r e d i n groundwater i n California. A l t h o u g h a r e l a t i v e l y l a r g e number o f p e s t i c i d e s have been r e p o r t e d , o n l y a few a r e o c c u r r i n g to such an e x t e n t t h a t t h e i r e f f e c t s w a r r a n t c o n s i d e r a t i o n from a t o x i c o l o g i c a l p o i n t o f v i e w . T h e f u m i g a n t s DBCP and EDB comprise by f a r the major p a r t o f the problem i n C a l i f o r n i a and i t i s p r o b a b l y the o c c u r r e n c e o f these two c o m p o u n d s t h a t r e p r e s e n t s the g r e a t e s t concern to human h e a l t h . Both a r e p o t e n t r e p r o d u c t i v e t o x i n s and the e v i d e n c e f o r t h e i r b e i n g c a r c i n o g e n i c i s overwhelming. The e p i d e m i o l o g i c a l study conducted i n Fresno county i n census t r a c t s c o n t a i n i n g a p p r e c i a b l e l e v e l s o f DBCP i s s u g g e s t i v e b u t more data need to be g e n e r a t e d b e f o r e i t can be c o n f i r m e d o r r e f u t e d t h a t DBCP i n w e l l - w a t e r has been r e s p o n s i b l e f o r i n c r e a s e d human c a n c e r d e a t h s .

Literature Cited 1.

Groundwater Contamination by Pesticides. California State Water Resources Control Board, Publication No. 83-45 sp, 1983.

2.

Cohen, D.B., and Bowers, G.W. Water Quality and Pesticides: A California Risk Assessment Program (Vol. 1), State Water Resources Control Board, Toxic Substances Control Program, Sacramento, CA, November, 1984.

3.

Gaston, J.M. to Williams, M. Letter from Sanitary Engineering Branch, California Department of Health Services to Special Pesticides Review Division, U.S. Environmental Protection Agency, May 31, 1979.

4.

Burlinson, N . E . ; Lee, L.A.; Rosenblatt, D.H. Environ. Sci. Technol. 1982, 16, 627-632.

5.

Torkelson, T.R.; Sadek, S . E . ; Rowe, V . K . ; Kodama, J.F.; Anderson, H.H.; Loquvam, C.S.; Hine, C.H. Toxicol. Appl. Pharmacol. 1961, 3, 545-559.

6.

Emergency Temporary Standard for Occupational Exposure to 1,2Dibromo-3-chloropropane (DBCP); Hearing. Federal Register 1977, 42 (175), 45536-45543.

7.

Whorton, D.; Krauss, R.M.; Marshall, S.; Milby, T.H. Lancet 1977, ii, 1259-1261.

8.

Kapp, R.W.; Picciano, D.J.; Jacobson, C.B. Mutat. Res. 1979, 64, 47-51.


434 9.

EVALUATION OF PESTICIDES IN GROUND WATER Evaluation of the Carcinogenic Risk of Chemicals to Humans, Vol. 20. Some Halogenated Hydrocarbons. International Agency for Research on Cancer, Lyon, France, 1979, pp. 83-96.


10. Bioassay of Dibromochloropropane for Possible Carcinogenicity (Carcinogenesis Technical Report Series, No. 28), National Cancer Institute, 78-828, 1978. 11. Dibromochloropropane (DBCP): Final position document. Special Pesticides Review Division, Office of Pesticide Programs, U.S. Environmental Protection Agency, September, 1978. 12. Van Duuren, B.L.; Goldschmidt, B.M.; Loewengart, G.; Smith, A.C.; Melchionne, S.; Selman, I.; Roth, D. J. Natl. Cancer Inst. 1979, 63, 1433-1439. 13. Carcinogen Assessment Group (E.P.A.) review of risk assessment for DBCP in drinking water in a memo to Jeff Kempter, Special Pesticides Review Division, U.S. Environmental Protection Agency, June, 1979. 14. Jackson, R.J.; Greene, C.J.; Thomas, J.T.; Murphy, E.L.; Kaldor, J. Literature Review on the Toxicological Aspects of DBCP and An Epidemiological Comparison of Patterns of DBCP Drinking Water Contamination with Mortality Rates from Selected Cancers in Fresno County, 1970-1979. Unpublished report to the California Department of Food and Agriculture from the California Department of Health Services, June 1, 1982. 15. Smith, C.; Margetich, S.; Fredrickson, A.S. A Survey of Well-Water in Selected Counties of California for Contamination by EDB in 1983. Unpublished report from the California Department of Food and Agriculture, HS-1123, September 12, 1983. 16. Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol. 15. Some Fumigants, the Herbicides 2,4-D and 2,4,5-T, Chlorinated Dibenzodioxins and Miscellaneous Industrial Chemicals. International Agency for Research on Cancer, Lyon, France, 1977, pp. 195-209. 17. Occupational Exposure to Ethylene Dibromide; Notice of Proposed Rulemaking. Federal Register 1983, 48 (196) 45956-46003. 18. Health Effects of Ethylene Dibromide (EDB). Unpublished report prepared by the California Department of Health Services, April 15, 1984, 25 pp. 19. Organic Quality of Groundwater in the Fruitvale Area, Kern County. Unpublished report prepared by the Sanitary Engineering Branch, California Department of Health Services, January, 1984.


23.

Β E RTE AU AND SPATH

Pesticide Contamination in California Ground Wate

20. NTP Technical Report on the Carcinogenesis Bioassay of 1,2Dichloropropane (propylene dichloride) in F3441N rats and B6C3F1 mice. National Toxicology Program. Draft Report, February 28, 1983.


21. Klant, R.R. Unpublished information from the California Regional Water Quality Control Board, North Coast Region, June 17, 1983. 22. "Drinking Water and Health" Vol. 5. Toxicity of Selected Contaminants, Aldicarb. National Academy Press, 1983, pp. 1012. 23. Pesticide Residues in Food, Evaluations 1982. Report of the Joint Meeting of the FAO Panel of Experts on Pesticide Residues in Food and the Environment and the WHO Expert Group on Pesticide Residues, Rome, 1983, pp. 7-15. 24. Spath, D. to Rogers, P. Aldicarb "Action Level". Internal Memorandum from Sanitary Engineering Branch, California Department of Health Services, July 25, 1983. 25. Sturm, G., personal communication. Sanitary Engineering Branch, California Department of Health Services, September, 1984. 26. "Drinking Water and Health" Vol. 4. Organic Solutes, Triazines. National Academy of Sciences, 1977, pp. 533-537. 27. "Drinking Water and Health" Vol. 4. Organic Solutes, Pentachlorophenol. National Academy of Sciences, 1977, pp. 750753. 28. Bowen, C., personal communication, Sanitary Engineering Branch, California Department of Health Services, February, 1985. 29. "Drinking Water and Health" Vol. 4. Organic Solutes, Pesticides: Fungicides, Dithiocarbamates. National Academy of Sciences, 1977, pp. 650-657. RECEIVED March 25, 1986


The Toxicological and Epidemiological Effects of Pesticide

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