Dermal Exposure to Pesticides - ACS Publications - American

25 Dermal Exposure to Pesticides The Environmental Protection Agency's Viewpoint

JOSEPH C. REINERT and DAVID J. SEVERN

Dermal Exposure Related to Pesticide Use Downloaded from pubs.acs.org by UNIV LAVAL on 07/11/16. For personal use only.

Office of Pesticide Programs, Hazard Evaluation Division, TS-769C, Exposure Assessment Branch, Environmental Protection Agency, Washington, DC 20460 An organizational overview of the risk assessment process in the EPA's Office of Pesticide Programs (OPP) is presented. A review of many field studies of agricultural worker exposure during pesticide application indicates that typically the principal route of exposure is through the skin. Procedures in OPP for estimating dermal exposure from "surro gate" studies are described. A predictive correla tion derived for estimating exposure during airblast application to orchards is presented, as are the results of new studies designed to monitor exposure during pesticide application to row crops using ground boom equipment. Methods for estimating dermal absorption and areas where more research is needed are discussed. Under the a e g i s o f t h e F e d e r a l I n s e c t i c i d e , F u n g i c i d e and R o d e n t i c i d e A c t ( F I F R A ) , t h e O f f i c e o f P e s t i c i d e Programs (OPP) o f t h e 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) r e g i s t e r s c h e m i c a l s f o r use as p e s t i c i d e s p r o v i d e d t h a t , among o t h e r c r i t e r i a , "when used i n a c c o r d a n c e w i t h widespread and ccmmonly r e c o g n i z e d p r a c t i c e , [they] w i l l not g e n e r a l l y cause unreasonable adverse e f f e c t s on the e n v i ronnent." P r o t e c t i o n of a g r i c u l t u r a l workers i n v o l v e d i n the a p p l i c a t i o n o f p e s t i c i d e s i s c o n s i d e r e d under t h e u m b r e l l a o f t h i s r i s k c r i t e r i o n , and t h e e s t i m a t i o n o f human exposure i s an i n t e g r a l p a r t o f O P P s r i s k assessment p r o c e d u r e s . An o r g a n i z a t i o n a l o v e r v i e w o f t h i s r i s k assessment p r o c e s s i s shown i n F i g u r e 1. P h y s i c a l s c i e n t i s t s i n t h e E x p o s u r e Assessment B r a n c h (ΕΑΒ) o f t h e H a z a r d E v a l u a t i o n D i v i s i o n (HED) have t h e r e s p o n s i b i l i t y o f e s t i m a t i n g a c t u a l worker e x p o s u r e , which i s t h e p r i n c i p a l t o p i c o f this talk. A g r i c u l t u r a l s c i e n t i s t s i n the S c i e n c e S u p p o r t B r a n c h (SSB) o f OPP s B e n e f i t s and Use D i v i s i o n (BUD) s u p p l y p e r t i n e n t use i n f o r m a t i o n a l o n g w i t h e s t i m a t e s of t h e f r e q u e n c y and d u r a t i o n o f e a c h a p p l i c a t i o n a c t i v i t y f o r which an exposure assessment i s prepared. T h i s f r e q u e n c y and d u r a t i o n i n f o r m a t i o n i s c r i t i c a l t o e s t i m a t e a n n u a l i z e d exposure, used f o r c h r o n i c r i s k assessments, most f r e q u e n t l y o n c o g e n i c a s s e s s m e n t s . The e s t i m a t e d exposure f o r the r e q u i r e d time i n t e r v a l ( d a i l y o r a n n u a l l y depending o n whether t h e assessment i s f o r an a c u t e o r c h r o n i c t o x i c o l o g i c a l c o n c e r n ) i s g i v e n t o H E D s T o x i c o l o g y B r a n c h (TB) where i t i s c o n s i d e r e d 1

1

1

T h i s chapter not subject to U . S . copyright. Published 1985, A m e r i c a n C h e m i c a l Society


DERMAL EXPOSURE RELATED TO PESTICIDE USE

HAZARD EVALUATION

EXPOSURE ASSESSMENT BRANCH

DIVISION

TOXICOLOGY BRANCH ESTIMATES DERMAL PENETRATION.

CALCULATES UNIT EXPOSURE FOR AGRICULTURAL WORKERS.

QUANTITATIVE

EVALUATES LABORATORY TOXICOLOGY DATA AND

SCIENCE SUPPORT BRANCH PROVIDES INFORMATION ON METHOD OF APPLICATION AND OTHER USE PARAMETERS. PROVIDES ESTIMATIONS FOR THE FREQUENCY AND DURA TK)N OF EXPOSURE UNDER ACTUAL USE CONDITIONS.

B E N E F I T S A N D U S E DIVISION

Figure Process

1.

Organizational

i n the O f f i c e

Overview o f the R i s k

of Pesticide

Programs.

Assessment


25.

REINERT AND SEVERN

EPA's

Viewpoint

on Dermal

Exposure

359

a l o n g w i t h t h e r e s u l t s of t h e l a b o r a t o r y e f f e c t s s t u d i e s t o produce a q u a n t i t a t i v e r i s k assessment. T h i s r i s k assessment i s c o n s i d e r e d i n the r i s k / b e n e f i t a n a l y s i s r e q u i r e d f o r r e g u l a t o r y d e c i s i o n s under FIFRA. R i s k assessments a r e undertaken when s i g n i f i c a n t adverse e f f e c t s a r e found i n l a b o r a t o r y a n i m a l s t u d i e s . T r a d i t i o n a l l y most r i s k assessments have been done f o r p e s t i c i d e s under RPAR o r Rebutt a b l e Presumption A g a i n s t R e g i s t r a t i o n , now r e f e r r e d t o a s S p e c i a l Review. More r e c e n t l y q u a n t i t a t i v e r i s k assessments have been c a r r i e d out f o r p e s t i c i d e s i n t h e R e g i s t r a t i o n S t a n d a r d o r r e r e g i s t r a t i o n p r o c e s s o r under r e g u l a r r e g i s t r a t i o n r e v i e w a s w e l l . EAB has r e v i e w e d many f i e l d s t u d i e s o f p e s t i c i d e a p p l i c a t o r exposure, and t h e dermal r o u t e i s t y p i c a l l y t h e r o u t e of h i g h e s t p o t e n t i a l exposure. F o r many a g r i c u l t u r a l work a c t i v i t i e s , most o f t h e p o t e n t i a l dermal exposure o c c u r s t o the hands. I n some i n s t a n c e s , f i e l d s t u d i e s have been c a r r i e d out t o a s s e s s exposure f o r a p a r t i c u l a r p e s t i c i d e / a p p l i c a t i o n method/crop c o m b i n a t i o n f o r w h i c h an exposure assessment i s r e q u i r e d . T h i s p r i m a r y s t u d y i s e v a l u a t e d , and i f judged s c i e n t i f i c a l l y a c c e p t a b l e , would be used d i r e c t l y i n t h e exposure assessment. W h i l e i t would be h i g h l y d e s i r a b l e t o have t h e r e s u l t s o f such a s c i e n t i f i c a l l y v a l i d , s t a t i s t i c a l l y d e s i g n e d f i e l d exposure m o n i t o r i n g s t u d y f o r each a s s e s s ment we a r e r e q u e s t e d t o perform, t h i s i s t y p i c a l l y n o t t h e c a s e . We t h e r e f o r e r e l y on a v a i l a b l e s t u d i e s f o r o t h e r c h e m i c a l s , s o c a l l e d "surrogate s t u d i e s . " The p o l i c y f o r use o f s u r r o g a t e s t u d i e s has been p u b l i s h e d i n t h e F e d e r a l R e g i s t e r (June 25, 1980), and t h e p h i l o s o p h y and mechanics o f t h e use o f s u r r o g a t e d a t a have been d i s c u s s e d i n various p u b l i c f o r a (1,2). C o n s i d e r a t i o n s i n v o l v e d i n choosing whether a study i s approp r i a t e t o use as a s u r r o g a t e t o e s t i m a t e exposure a r e d e l i n e a t e d below: FACTORS IN CHOOSING APPROPRIATE SURROGATE STUDIES FOR EXPOSURE ASSESSMENTS 1. 2. 3. 4. 5. 6. 7.

S i m i l a r Method o f A p p l i c a t i o n S i m i l a r Use P a t t e r n S i m i l a r Type o f F o r m u l a t i o n ( f o r m i x e r - l o a d e r s ) S t u d y E v a l u a t e d by EAB Study i s N o n - p r o p r i e t a r y Exposure Measured During Each S e p a r a t e A p p l i c a t i o n A c t i v i t y S i m i l a r P r o t e c t i v e Methods

The key f a c t o r i s t h e method of a p p l i c a t i o n . O t h e r f a c t o r s i n c l u d e s i m i l a r i t y i n use p a t t e r n and type o f f o r m u l a t i o n ( e m u l s i f i a b l e c o n c e n t r a t e , w e t t a b l e powder, e t c . ) f o r m i x e r - l o a d e r s . I n a d d i t i o n , s t u d i e s used as s u r r o g a t e s must be reviewed and v a l i d a t e d i n t e r n a l l y , and t h e s t u d i e s must be n o n - p r o p r i e t a r y . One i m p o r t a n t f a c t o r t h a t f r e q u e n t l y causes d i f f i c u l t i e s i s t h a t a n o t h e r w i s e sound exposure s t u d y d i d not s e p a r a t e l y m o n i t o r exposure


360


during d i f f e r e n t a c t i v i t i e s . Even i f i n a c t u a l p r a c t i c e an i n d i v i d u a l would do b o t h t h e m i x i n g - l o a d i n g as w e l l a s t h e a p p l i c a t i o n , i t i s i m p o r t a n t t o know t h e p r o p o r t i o n o f exposure a s s o c i a t e d w i t h each a c t i v i t y . A r e g u l a t o r y o p t i o n s u c h a s wearing a f a c e s h i e l d , e.g., m i g h t be p r a c t i c a l f o r t h e r e l a t i v e l y s h o r t p e r i o d o f time r e q u i r e d f o r m i x i n g - l o a d i n g i b u t might n o t be a c c e p t a b l e f o r t h e l o n g h o u r s o f a p p l i c a t i o n i n some s i t u a t i o n s . A l s o , t h e magnitude o f p o t e n t i a l e x p o s u r e may be c o n s i d e r a b l y d i f f e r e n t f o r e a c h s e p arate a c t i v i t y , i n o r d e r t o p r o p e r l y e v a l u a t e exposure r e d u c t i o n o p t i o n s , t h e p o t e n t i a l exposure i n e a c h a c t i v i t y must be c a l c u l a b l e . I n e s t i m a t i n g e x p o s u r e f o r a p e s t i c i d e a p p l i c a t i o n from a s u r r o g a t e s t u d y , i t has been o u r e x p e r i e n c e t h a t t h e p r o p e r (and l o g i c a l ) c o n v e r s i o n f a c t o r s a r e amounts o f p e s t i c i d e a p p l i e d f o r a p p l i c a t o r s and t h e q u a n t i t y o f c h e m i c a l h a n d l e d by m i x e r l o a d e r s . U n f o r t u n a t e l y , t h e s e d a t a a r e n o t always r e a d i l y r e t r i e v a b l e from exposure m o n i t o r i n g r e p o r t s due t o t h e format u s e d f o r r e p o r t i n g the data o r the i n s u f f i c i e n c y o f experimental d e t a i l s . I n such i n s t a n c e s , o t h e r f a c t o r s (e.g., tank c o n c e n t r a t i o n f o r a p p l i c a t o r s o r t i m e i n v o l v e d i n m i x i n g - l o a d i n g ) must be u s e d . F o r c e r t a i n a p p l i c a t i o n methods, OPP does have a c o n s i d e r a b l e data base. E x t e n s i v e d a t a e x i s t f o r monitoring exposure t o a p p l i c a t o r s i n v o l v e d i n o r c h a r d s p r a y i n g u s i n g a i r b l a s t equipment. We (3) have r e v i e w e d t h e a v a i l a b l e d a t a , d i s c a r d e d s t u d i e s where exposure d u r i n g m i x i n g - l o a d i n g c o u l d n o t be s e g r e g a t e d from e x p o s u r e d u r i n g a p p l i c a t i o n , and i n an e x t e n s i o n o f t h e work o f D a v i s ( 4 ) , a t t e m p t e d t o examine t h e e x p o s u r e t o a p p l i c a t o r s i n o r d e r t o d e r i v e s t a t i s t i c a l l y v a l i d and u s e f u l p r e d i c t i v e c o r r e l a t i o n s . A s t a t i s t i c a l l y s i g n i f i c a n t c o r r e l a t i o n was found between a p p l i c a t i o n r a t e and dermal e x p o s u r e . A Spearman Rank c o r r e l a t i o n a n a l y s i s (a t e s t t o d e t e r m i n e i f an i n c r e a s e i n e x p o s u r e i s a s s o c i a t e d w i t h an i n c r e a s e in a p p l i c a t i o n rate) indicated a s t a t i s t i c a l l y s i g n i f i c a n t c o r r e l a tion. Such a s i g n i f i c a n t c o r r e l a t i o n was n o t found f o r a n o t h e r a p p l i c a t i o n parameter, tank c o n c e n t r a t i o n . A linear regression a n a l y s i s o f d e r m a l exposure and a p p l i c a t i o n r a t e a l s o i n d i c a t e d a s i g n i f i c a n t c o r r e l a t i o n a s i s shown i n F i g u r e 2. The a c t u a l d a t a p o i n t s shown a r e t h e mean v a l u e s o b s e r v e d i n e a c h s t u d y and a r e unweighted f o r t h e number o f r e p l i c a t e s i n t h a t s t u d y . Weighted v a l u e s were p r o p e r l y used t o g e n e r a t e t h e r e g r e s s i o n l i n e and t h e 95% c o n f i d e n c e l i m i t s shown w i t h d o t t e d l i n e s . T h e s e dermal exposure v a l u e s assume 3,000 cm^ f exposed s k i n , c o r r e s p o n d i n g t o an a p p l i c a t o r w e a r i n g l o n g p a n t s , a s h o r t - s l e e v e d open-necked s h i r t and no g l o v e s o r f a c i a l p r o t e c t i o n ( 5 ) . The c o r r e l a t i o n i s q u i t e r e m a r k a b l e (r=0.7) when you c o n s i d e r t h a t a l l o t h e r a p p l i c a t i o n , c l i m a t i c , and equipment f a c t o r s a r e c o n t a i n e d under t h i s u m b r e l l a of uncertainty. 0

W h i l e we do n o t presume t o u n d e r s t a n d a l l t h e v a r i o u s f a c t o r s which c o n t r i b u t e t o d e t e r m i n i n g dermal exposure d u r i n g a i r b l a s t a p p l i c a t i o n , we c a n w i t h a c e r t a i n c o n f i d e n c e e s t i m a t e a p r e d i c t e d v a l u e a l o n g w i t h an a s s o c i a t e d range o f e x p e c t e d v a l u e s f o r t h i s a p p l i c a t i o n technique. W h i l e we p o s s e s s an e x t e n s i v e d a t a base o f l a b o r a t o r y a n i m a l s t u d i e s f o r o n c o g e n i c i t y (and o t h e r a c u t e and c h r o n i c h e a l t h e f f e c t s ) , t h e bottom l i n e o f an o v e r a l l r i s k assessment r e q u i r e s a c o m b i n a t i o n o f t o x i c o l o g y d a t a , e x p o s u r e

EPAs

REINERT AND SEVERN

Viewpoint

on Dermal

Exposure


80i Ν =23 r

70

"

0 7

ρ < 0.01

10

0

1

2

3

4

5

6

7

8

9

10

APPUCATION RATE (lb ai/A) —

F i g u r e 2. C o r r e l a t i o n o f Dermal Exposure and A p p l i c a t i o n R a t e f o r O r c h a r d S p r a y i n g U s i n g A i r b l a s t Equipment. The d a t a p o i n t s shown a r e t h e mean v a l u e s from t h e s t u d i e s . The r e g r e s s i o n l i n e and 95% c o n f i d e n c e l i m i t s ( d o t t e d l i n e s ) were g e n e r a t e d u s i n g means w e i g h t e d f o r t h e number o f r e p l i c a t e s i n each study* Exposure i s n o r m a l i z e d f o r 3 0 0 0 c m o f exposed s k i n a r e a . 2

f


362

d a t a , a n d a p r o c e d u r e f o r l i n k i n g t h e two, i . e . low d o s e e x t r a p o l a t i o n models f o r q u a n t i f y i n g o n c o g e n i c r i s k . Until the s t a t e o f t h e a r t i n t h i s e x t r a p o l a t i o n p r o c e d u r e beccmes more p r e c i s e , t h e present l e v e l o f s o p h i s t i c a t i o n i n p r e d i c t i n g exposure f o r a i r b l a s t a p p l i c a t i o n may b e a c c e p t a b l e . A n o t h e r method o f a p p l i c a t i o n f o r which a g r e a t d e a l o f d a t a i s a v a i l a b l e i s g r o u n d boon a p p l i c a t i o n t o row c r o p s . The r e s u l t s o f a s e r i e s o f s t u d i e s u s i n g v a r i o u s p e s t i c i d e s c a r r i e d o u t by t h e Agency a t numerous s i t e s around t h e c o u n t r y a r e summarized i n T a b l e I .


Table I.

DERMAL EXPOSURE TO APPLICATORS FOR GROUND BOOM APPLICATION TO ROW CROPS

Number o f Observations

Mean L e v e l (mg/hr)

Range o f V a l u e s (mg/hr)

T o t a l dermal exposure

15

24.4

1.0-130

Exposure t o hands

15

18.3

0.96-69

These r e s u l t s a r e c o n t a i n e d i n a d r a f t r e p o r t (6) which i s c u r r e n t l y undergoing peer review. The f i n a l r e p o r t s h o u l d be a v a i l a b l e by t h e end o f t h i s c a l e n d a r y e a r . A s c a n been seen, most o f t h e dermal e x p o s u r e i s t o t h e hands. The r e a s o n f o r t h i s i s u n c e r t a i n , b u t v e r y l i k e l y r e s u l t s f r c m t h e a p p l i c a t o r s hand c o n t a c t w i t h t h e equipment d u r i n g s p r a y i n g . A v e r a g e t o t a l e x p o s u r e i s 18.5 mg/hr. These d a t a were c o l l e c t e d u n d e r a v a r i e t y o f u s e and c l i m a t i c c o n d i t i o n s . A p p l i c a t o r e x p o s u r e t o h e r b i c i d e s , i n s e c t i c i d e s a n d f u n g i c i d e s was m o n i t o r e d u n d e r a c t u a l f i e l d c o n d i t i o n s d u r i n g a p p l i c a t i o n t o a v a r i e t y o f c r o p s w i t h v a r i o u s t y p e s o f boom rigs. A p p l i c a t i o n r a t e s ranged f r c m 0.23 t o 3.2 l b s a i / A . I n t h i s same s e r i e s o f ground boom s t u d i e s , e x p o s u r e t o m i x e r l o a d e r s was a l s o measured f o r two t y p e s o f f o r m u l a t i o n s . The l i q u i d f o r m u l a t i o n s ranged i n c o n c e n t r a t i o n f r c m 0.95 t o 5.6 l b s . a c t i v e i n g r e d i e n t p e r g a l l o n , a n d t h e w e t t a b l e powders s t u d i e d were e i t h e r 50 o r 80% a c t i v e i n g r e d i e n t by w e i g h t . The r e s u l t s a r e summarized i n T a b l e I I . Much g r e a t e r e x p o s u r e i s o b s e r v e d f o r l i q u i d f o r m u l a t i o n t h a n f o r t h e w e t t a b l e powders. T h e range o f exposure o b s e r v e d i s v e r y l a r g e f o r b o t h t y p e s o f f o r m u l a t i o n s , making t h e u s e f u l n e s s o f a mean v a l u e m a r g i n a l . T h i s l a r g e range i s e x p e c t e d s i n c e t h e i n d i v i d u a l s a r e h a n d l i n g t h e c o n c e n t r a t e d m a t e r i a l , and a s m a l l d i f f e r e n c e i n c a r e c a n l e a d t o a g r e a t d i f f e r e n c e i n exposure. Most o f t h e p o t e n t i a l dermal e x p o s u r e i s t o t h e hands ( t h e r e was d e r m a l e x p o s u r e t o a r e a s o t h e r t h a n t h e hands f o r t h e l i q u i d f o r m u l a t i o n s , but t h i s s m a l l e x p o s u r e does n o t a p p e a r when t h e r e s u l t s a r e rounded o f f t o two s i g n i f i c a n t f i g u r e s ) . The d a t a f o r ground bocm a p p l i c a t o r s and m i x e r - l o a d e r s were m a n i p u l a t e d i n v a r i o u s ways i n a t t e m p t s t o d e t e r m i n e whether u s e f u l p r e d i c t i v e c o r r e l a t i o n s o f e x p o s u r e w i t h u s e parameters c a n b e found. Some a p p a r e n t l y s t r o n g , s t a t i s t i c a l l y v a l i d c o r r e l a t i o n s were found. However, e v e n though c e r t a i n c o r r e l a t i o n s were s i g n i f -

25.

REINERT AND SEVERN

Table I I .

EPA's

Viewpoint

on Dermal

Exposure

363

DERMAL EXPOSURE TO MIXER-LOADERS FOR TWO TYPES OF FORMULATIONS

Type o f Formulation

Number o f Observations

Mean L e v e l (mg/hr)

Range o f V a l u e s (mg/hr)


WETTABLE POWDER T o t a l dermal

11

510

39 - 3,000

11

500

36 - 3 0 0 0

exposure Hand exposure

r

LIQUID FORMULATION T o t a l dermal

6

7 800

27 - 32,000

6

7,800

26 - 32,000

r

exposure Hand e x p o s u r e

i c a n t , we b e l i e v e t h e i r meaning a n d u s e f u l n e s s i s t e n u o u s . The r e a s o n f o r t h i s i s i l l u s t r a t e d i n t h e example shown i n F i g u r e 3. T h i s g r a p h shows t h e r e s u l t s o f a l i n e a r r e g r e s s i o n a n a l y s i s o f f o r e a r m v e r s u s hand e x p o s u r e f o r a l l m i x e r - l o a d e r s . This correlat i o n was a t t e m p t e d i n hopes o f f i n d i n g a b e t t e r method f o r d e t e r m i n i n g hand exposure, which, a s d i s c u s s e d i n t h i s symposium, i s p a r t i c u l a r l y troublesome e x p e r i m e n t a l l y . The r e l a t i o n s h i p i s a p p a r e n t l y s i g n i f i c a n t a t t h e 0.01 l e v e l ( r = 0.82). However, i f one d a t a p o i n t ( p o i n t a ) i s removed f r o m t h e d a t a s e t , t h e r e i s no s i g n i f i c a n t c o r r e l a t i o n ( r = 0.18). Because o f t h e s m a l l sample s i z e used i n a l l regression analyses, a l l apparently strong c o r r e l a t i o n s o b s e r v e d were l i k e w i s e dominated by a s i n g l e d a t a p o i n t . T h i s was n o t t h e c a s e f o r t h e a i r b l a s t c o r r e l a t i o n where t h e d a t a s e t was much l a r g e r , a n d removal o f any s i n g l e p o i n t d i d n o t have a d r a m a t i c e f f e c t on the c o r r e l a t i o n . We t h e r e f o r e f e e l a t t h e p r e s e n t t i m e t h a t i t i s more a p p r o p r i a t e t o r e p o r t j u s t t h e mean and t h e range f o r ground boom a p p l i c a t o r e x p o s u r e , r a t h e r t h a n u s e a d e r i v e d predictive correlation. F o r many o t h e r a p p l i c a t i o n s c e n a r i o s , s u c h a s backpack s p r a y i n g and a e r i a l a p p l i c a t i o n o f o i l - b a s e d u l t r a low volume f o r m u l a t i o n s , e x t e n s i v e exposure m o n i t o r i n g s t u d i e s a r e u n a v a i l a b l e . I n such c a s e s , we f r e q u e n t l y must r e l y o n a s m a l l number o f p u b l i s h e d studies as surrogates. EAB m a i n t a i n s and p e r i o d i c a l l y u p d a t e s a n exposure b i b l i o g r a p h y t h a t c o n t a i n s a l l n o n - p r o p r i e t a r y exposure s t u d i e s o f which we a r e aware. A p r e s e n t g o a l i s t o i d e n t i f y and computerize a l l s t u d i e s which c o n t a i n d i r e c t exposure d a t a . This project requires a great deal of quality control. The s c i e n t i f i c a c c e p t a b i l i t y o f the s t u d i e s which are used i n c r e a t i n g the data b a s e must be d e t e r m i n e d by c o n s i s t e n t s t a n d a r d s which have been agreed t o by a l l u s e r s o f t h e d a t a b a s e . From t h i s d a t a b a s e we



Figure 3. Loaders. Correlation of Forearm and Hand Exposure f o r Mixer-

25.

REINERT AND SEVERN

EPA's

Viewpoint

on Dermal

Exposure

365

c o u l d c a l l u p a l l d a t a a v a i l a b l e f o r , a s a n example, a e r i a l a p plication of herbicides. Such a n automated s y s t e m would have obvious b e n e f i t s . Some e x p o s u r e s t u d i e s which meet t h e c r i t e r i a above a n d which have been used b y EAB a r e shown below:


GROUND RIG DRIVER W ô l f e e t a l , 1967 (7) S t a i f f e t a l , 1975 (8) A t t a l l a h e t a l , 1982 (9) Dubelman e t a l , 1982 (10)

MIXER/LOADER WP J e g i e r , 1964 (11) E v e r h a r t and H o l t , 1982 (19) EC

AERIAL J e g i e r , 1964 (11) Lavy e t a l , 1980 (12) P e o p l e s e t a l , 1981 (13) A t t a l l a h e t a l , 1982 (9)

P e o p l e s e t a l , 1981 (13) A t t a l l a h e t a l , 1982 (9) Dubelman e t a l , 1982 (10) DUST W o l f e and Durham, 1967 ( 2 0 )

HAND SPRAYING W o l f e e t a l , 1967 ( 7 ) Vfolfe e t a l , 1974 (14) Maddy e t a l , 1979 (15) Lavy e t a l , 1980 (12) INDOOR HOUSE

SEED TREATMENT

W o l f e e t a l , 1959 (16) F l e t c h e r e t a l , 1959 (17) Haag a n d Pruggmayer, 1981 (18)

S t e v e n s and D a v i s ,

1980 (21)

T h i s l i s t i s n o t i n t e n d e d t o be a l l - i n c l u s i v e : other scient i f i c a l l y v a l i d studies are available. The agency i s i n t h e p r o c e s s o f w r i t i n g g u i d e l i n e s f o r c o n d u c t i n g f i e l d m o n i t o r i n g s t u d i e s f o r a g r i c u l t u r a l worker e x p o s u r e . These g u i d e l i n e s w i l l a i d p e s t i c i d e r e g i s t r a n t s and o t h e r s i n c o n d u c t i n g a c c e p t a b l e f i e l d s t u d i e s . Two i s s u e s which w i l l r e q u i r e e x t e n s i v e d i s c u s s i o n and p o l i c y r e s o l u t i o n a r e l i k e l y t o be t h e number o f r e p l i c a t e s and/or number o f s i t e s r e q u i r e d and t h e "when r e q u i r e d " s e c t i o n o f t h e g u i d e l i n e s . T h i s l a t t e r a r e a w i l l l i k e l y b e based o n b o t h t o x i c o l o g i c a l f a c t o r s and a c o n s i d e r a t i o n o f t h e adequacy o f t h e s u r r o g a t e e x p o s u r e d a t a b a s e . In c o n c l u s i o n , t h e u s e o f s u r r o g a t e d a t a f o r e x p o s u r e a s s e s s ments w i l l most c e r t a i n l y c o n t i n u e . The r e s o u r c e s r e q u i r e d t o c a r r y o u t f i e l d s t u d i e s f o r e v e r y c r o p / a p p l i c a t i o n method/ p e s t i c i d e c o m b i n a t i o n would be overwhelming. EAB s g o a l i s t o d e r i v e r e l i a b l e and u s e f u l c o r r e l a t i o n s which w i l l o b v i a t e t h e need f o r r e q u i r i n g such extensive s t u d i e s . The p r e c e e d i n g d i s c u s s i o n e s t i m a t e s t h e amount o f p e s t i c i d e impinging on the s k i n s u r f a c e . E s t i m a t i n g a c t u a l dose from patch 1

366


d a t a r e q u i r e s an e s t i m a t i o n of d e r m a l p e n e t r a t i o n . W h i l e f o r m a l l y a r e s p o n s i b i l i t y o f TB, HED I w i l l summarize t h e p r o c e d u r e s employed t o e s t i m a t e t h e f r a c t i o n of p e s t i c i d e r e a c h i n g t h e s k i n s u r f a c e w h i c h w i l l a c t u a l l y e n t e r t h e b i o l o g i c a l system. These p r o c e d u r e s a r e as f o l l o w s : f


PROCEDURES FOR ESTIMATING DERMAL PENETRATION 1. 2. 3. 4.

Assume 100% Dermal P e n e t r a t i o n Compare B i o l o g i c a l E n d p o i n t s by O r a l and Dermal Routes E s t i m a t e on t h e B a s i s of P h y s i c o c h e m i c a l P r o p e r t i e s R e q u i r e Study t o A s s e s s Dermal P e n e t r a t i o n

O b v i o u s l y i f one assumes t h a t 100% o f t h e p e s t i c i d e r e a c h i n g t h e s u r f a c e o f the s k i n p e n e t r a t e s i n t o the body, and t h e r e i s an adequate m a r g i n of s a f e t y o r t h e p o t e n t i a l c h r o n i c r i s k s a r e a c c e p t a b l e , no f u r t h e r m a c h i n a t i o n s a r e n e c e s s a r y . One can a l s o compare, when d a t a a r e a v a i l a b l e ( 2 2 ) , b i o l o g i c a l e f f e c t s ( u s u a l l y LD 50's ) f o r p e s t i c i d e s a d m i n i s t e r e d by dermal and o r a l r o u t e s t o e s t i m a t e dermal p e n e t r a t i o n . A d i f f i c u l t y w i t h t h i s approach i s t h a t due t o d i f f e r i n g route-dependent r e l a t i v e m e t a b o l i s m , an "apparent" dermal p e n e t r a t i o n of g r e a t e r t h a n 100% can be c a l c u l a t e d i n some c a s e s . T h e r e f o r e c a r e must be e x e r c i s e d when u s i n g t h i s approach. I t i s a l s o p o s s i b l e t o e s t i m a t e dermal p e n e t r a t i o n on the b a s i s of the physicochemical p r o p e r t i e s of the p e s t i c i d e , w i t h a c e r t a i n l i p o p h i l i c i t y r e q u i r e d f o r s i g n i f i c a n t dermal p e n e t r a t i o n . F i n a l l y , on a case-by-case b a s i s , ΊΒ w i l l r e q u i r e a d e r m a l p e n e t r a t i o n study. TB has d i s t r i b u t e d o u t s i d e t h e agency a d r a f t p r o t o c o l f o r what i t c o n s i d e r s an a c c e p t a b l e dermal p e n e t r a t i o n s t u d y . The s t u d y i s d e t a i l e d and e x p e n s i v e , b u t has produced u s e f u l r e s u l t s i n the l i m i t e d number c a s e s where i t has been used i n c l o s e c o n s u l t a t i o n w i t h TB. The d e t a i l s a r e d e l i n e a t e d below: HIGHLIGHTS OF A DRAFT PROTOCOL A DERMAL PENETRATION STUDY 1. 2. 3. 4. 5.

FOR

I n v i v o Rat Study. Four Doses w i t h 20 A n i m a l s p e r Dose Radiolabeled Chemical w i t h F i e l d Solvent Mass B a l a n c e R e q u i r e d C o n t a c t Dr. R o b e r t Z e n d z i a n (703-557-1511) f o r P r o t o c o l and C o n s u l t a t i o n

The i n v i v o r a t s t u d y r e q u i r e s 20 a n i m a l s a t each o f f o u r doses. The d o s e s a r e chosen t o c o v e r t h e range o f e x p o s u r e s l i k e l y t o be e n c o u n t e r e d i n t h e f i e l d . The s t u d y r e q u i r e s t h e use o f r a d i o l a b e l e d c h e m i c a l and an a p p r o p r i a t e f i e l d s o l v e n t . A mass b a l a n c e i s r e q u i r e d t o a c c o u n t f o r d e p o s i t e d p e s t i c i d e w h i c h may have been l o s t frcm t h e s k i n s u r f a c e by a r o u t e o t h e r t h a n dermal p e n e t r a t i o n . The s t u d y i s e x p e n s i v e and s h o u l d n o t be initiated w i t h o u t c o n s u l t a t i o n w i t h Dr. R o b e r t Z e n d z i a n of TB.

25.

REINERT AND SEVERN

EPA's

Viewpoint

on Dermal

Exposure

367

Sane o f t h e c u r r e n t r e s e a r c h needs i n OPP i n r e g a r d t o a s s e s s i n g t h e p o t e n t i a l dermal exposure o f a g r i c u l t u r a l workers t o p e s t i c i d e s , and r e g u l a t o r y s t e p s t h a t c a n be t a k e n t o m i t i g a t e t h i s p o t e n t i a l r o u t e o f exposure a r e l i s t e d b e l o w :


RESEARCH NEEDS 1. 2. 3. 4. 5.

F u r t h e r F i e l d S t u d i e s f o r Many A p p l i c a t i o n S c e n a r i o s F u r t h e r P r e d i c t i v e C o r r e l a t i o n Development Improved Methods f o r M e a s u r i n g Hand Exposure More Dermal P e n e t r a t i o n D a t a More Data o f E f f i c i e n c y o f P r o t e c t i v e C l o t h i n g / D e v i c e s

A d d i t i o n a l f i e l d s t u d i e s a r e needed f o r many a p p l i c a t i o n s c e n a r i o s where d a t a a r e l i m i t e d . T h i s w i l l h o p e f u l l y r e s u l t i n t h e f u r t h e r development o f u s e f u l p r e d i c t i v e c o r r e l a t i o n s . Improved methodology i n the a r e a of e s t i m a t i n g hand exposure would be welcome. I h e d a t a base f o r e s t i m a t i n g d e r m a l p e n e t r a t i o n a l s o needs t o be expanded. F i n a l l y , a s D r . M o r a s k i i n d i c a t e d e a r l i e r i n h i s p r e s e n t a t i o n , we need t o know more about t h e e f f e c t i v e n e s s o f v a r i o u s items o f p r o t e c t i v e c l o t h i n g and p r o t e c t i v e d e v i c e s . The use o f p r o t e c t i v e c l o t h i n g has been one o f t h e c h i e f r e g u l a t o r y o p t i o n s used i n OPP i n many o f c u r r e c e n t d e l i b e r a t i o n s . N o n t e c h n i c a l Summary 1

The p r o c e d u r e s used i n t h e EPA s O f f i c e o f P e s t i c i d e Programs (OPP) t o e s t i m a t e p e s t i c i d e exposure t o a g r i c u l t u r a l workers a r e d e s c r i b e d . T y p i c a l l y , most o f exposure o c c u r s through t h e s k i n . The l e v e l o f e x p e c t e d exposure f o r two t y p e s o f commonly used p e s t i c i d e a p p l i c a t i o n equipment i s d i s c u s s e d . There i s a l s o a d i s c u s s i o n o f t h e r e s e a r c h needed t o e n a b l e OPP t o make more r e l i a b l e e s t i m a t e s o f a p p l i c a t o r exposure t o p e s t i c i d e s .

Literature Cited 1. 2. 3. 4. 5. 6. 7.

Severn, D . J . In "Genetic Toxicology. An Agricultural Perspec tive"; Fleck R.A. and Hollaender, Α., Eds.; Plenum: New York, 1982; pp. 235-242. "Use of Exposure Data for Risk Assessment," Environmental Protection Agency, 1980. Day, H.R. and Reinert, J.C., Manuscript in Preparation. Davis, J.E., unpublised data. Hays, W.J., "Toxicology of Pesticides"; William and Wilkins: Baltimore, 1975. "Applicator and Mixer/Loader Exposure to Pesticides During Ground Boom Spraying Operations," Environmental Protection Agency, 1984. Wolfe, H.R.; Durham W.F.; and Armstrong, J.F. Arch. Environ. Hlth. 1967, 14, 622-33.


368


8. Staiff, D.C; Comer, S.W.; Armstrong J.F.; Wolfe, H.R. Bull. Environ. Contam. Toxicol. 1975, 14, 334-40. 9. Atallah, Y.H., Cahill, W.P.; Whitacre, D.M. Arch. Environ. Contam. Toxicol. 1982, 11, 219-25. 10. Dubelman, S.; Lauer, R.; Arras, D.D.; Adams, S.A. J. Ag. Food Chem. 1982, 30, 528-32. 11. Jegier, A. Arch. Environ. Hlth. 1964, 8, 565-69. 12. Lavy T.L.; Shepard, J.S.; Mattice, J.D. J . Ag. Food Chem. 1980, 28, 626-30. 13. "Monitoring of Potential Exposure of Mixer-Loaders, Pilots, and Flaggers During Application of of Tributyl Phosphorothioate (DEF) and Tributyl Phosphorotrithioate (Folex) to Cotton Fields in the San Joaquin Valley of California in 1979," California Department of Food and Agriculture, 1979. 14. Wolfe, H.R.; Armstrong, J.F.; Durham, W.F. Mosquito News 1974, 34, 263-67. 15. "A Study in Southern California in July 1979 of the Potential Dermal and Inhalation Exposure of Applicators and Other Persons Who Might Later Enter or Occupy Areas Treated with Chlordane Used Against Subterranean Termites Under Houses," California Department of Food and Agriculture, 1979. 16. Wolfe, H.R., Walker, K.C.; Elliott, J.W. Bull. Wld. Hlth. Org. 1959, 20, 1-14. 17. Fletcher, T.E.; Press, J.M.; Wilson, D.B. Bull. Wld. Hlth. Org. 1959, 20, 15-25. 18. Haag, F.; Pruggmayer, D., unpublished data. 19. Everhart, L.P.; Holt, R.F. J. Ag. Food Chem. 1982, 30 20. Wolfe, H.R.; Durham, W.F.; Armstrong, J.F. Arch. Environ. Hlth. 1967, 14, 622-33. 21. Stevens, E.R.; Davis, J.E. Bull. Environ. Contam. Toxicol. 1980, in press. 22. Gaines, T.B. Tox. Appl. Pharm. 1969, 14, 515-34. RECEIVED September 24, 1984

Dermal Exposure to Pesticides - ACS Publications - American

Recommend Documents