The Environmental Protection Agency's Use of ... - ACS Publications

Chapter 25

Downloaded by NORTH CAROLINA STATE UNIV on December 27, 2017 | http://pubs.acs.org Publication Date: December 23, 1988 | doi: 10.1021/bk-1988-0382.ch025

The Environmental Protection Agency's Use of Biological Monitoring Data for the Special Review of Alachlor Curt Lunchick, Gary Burin, Joseph C. Reinert, and Karen E. Warkentien Office of Pesticide Programs, Hazard Evaluation Division (TS-769C), Exposure Assessment Branch, Environmental Protection Agency, Washington, DC 20460

In conducting the Special Review of the herbicide alachlor, the U.S. Environmental Protection Agency (EPA) evaluated biological monitoring studies conducted by the Monsanto Chemical Company, the registrant of alachlor. The biological monitoring studies allowed the Agency to estimate the internal dosage of alachlor received by workers during mixing/ loading and ground boom application of alachlor from enclosed tractor cabs. The Monsanto study contained only four replicates per formulation, used Monsanto employees, and only used enclosed application vehicles. Because internal dosage estimates from bio logical monitoring data are chemical-specific and, therefore, not amenable to the use of surrogate data, the Agency evaluated patch exposure studies to ensure representation of a wider range of potential exposure s i t u ations. A Monsanto patch exposure study i n which alachlor was applied similarly to the biological monitoring studies and six expo sure studies from the published literature provided approximately 100 exposure r e p l i cates employing a variety of commonly used application equipment. The exposure studies established a two orders of magnitude range of exposure to which the Monsanto exposure estimates were at the low end. This range was transferred to the biological monitoring dosage establishing a dosage range of 0.0054 to 0.54 ug/kg body weight (bwt)/lb active ingredient (ai) when open pour mixing/loading occurs and a range of 0.0034 to 0.34 ug/kg bwt/lb a i when a mechanical transfer loading system is used. This chapter not subject to U.S. copyright Published 1989 American Chemical Society

Wang et al.; Biological Monitoring for Pesticide Exposure ACS Symposium Series; American Chemical Society: Washington, DC, 1988.


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BIOLOGICAL MONITORING FOR PESTICIDE EXPOSURE I n t h e U n i t e d S t a t e s , t h e O f f i c e o f P e s t i c i d e Programs (OPP) o f EPA h a s t h e r e s p o n s i b i l i t y o f r e g u l a t i n g t h e use o f p e s t i c i d e s under t h e 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 (FIFRA). Under FIFRA, p e s t i c i d e r e g i s t r a n t s have t h e r e s p o n s i b i l i t y o f p r o v i d i n g t h e h e a l t h and s a f e t y d a t a n e c e s s a r y t o s u p p o r t t h e r e g i s t r a t i o n o f t h e i r p r o d u c t s . The Agency, i n t u r n , i s charged w i t h e v a l u a t i n g t h e s e d a t a and d e t e r m i n i n g t h a t t h e r e g i s t e r e d uses o f t h e p r o d u c t s do not p r o d u c e an u n r e a s o n a b l e a d v e r s e e f f e c t on t h e environment. To a s s i s t t h e r e g i s t r a n t s i n p r o v i d i n g d a t a on t h e exposure t o i n d i v i d u a l s h a n d l i n g p e s t i c i d e s , t h e Agency has p u b l i s h e d t h e P e s t i c i d e Assessment G u i d e l i n e s , S u b d i v i s i o n U: A p p l i c a t o r Exposure M o n i t o r i n g . S u b d i v i s i o n U i s intended t o a i d r e g i s t r a n t s i n conducting f i e l d s t u d i e s t h a t estimate the l e v e l o f exposure t o i n d i v i d u a l s who a r e o c c u p a t i o n a l l y exposed t o p e s t i c i d e s d u r i n g a p p l i c a t i o n and r e l a t e d a c t i v i t i e s , such as m i x i n g , l o a d i n g , and f l a g g i n g . H i s t o r i c a l l y , OPP has recommended t h a t a p p l i c a t o r e x p o s u r e s t u d i e s be c a r r i e d o u t u s i n g p a s s i v e d o s i m e t r y . T h i s t e c h n i q u e measures t h e amount o f c h e m i c a l i m p i n g i n g on t h e s u r f a c e o f t h e s k i n o r t h e amount o f c h e m i c a l a v a i l a b l e f o r i n h a l a t i o n as d e t e r m i n e d through t h e use o f a p p r o p r i a t e t r a p p i n g d e v i c e s . P a t c h e s o f v a r i o u s c o n s t r u c t i o n a r e used t o t r a p r e s i d u e s w h i c h c o u l d r e s u l t i n d e r m a l exposure t o v a r i o u s body p a r t s . P o t e n t i a l i n h a l a t i o n e x p o s u r e i s g e n e r a l l y measured u s i n g a p e r s o n a l s a m p l i n g pump w i t h an i n t a k e p l a c e d c l o s e t o t h e w o r k e r ' s b r e a t h i n g zone. A n o t h e r t y p e o f m o n i t o r i n g t h a t may be used t o e s t i m a t e human i n t e r n a l dosage t o p e s t i c i d e s i s b i o l o g i c a l m o n i t o r i n g . T h i s method e s t i m a t e s t h e l e v e l o f i n t e r n a l dosage f r o m e i t h e r a measurement o f body b u r d e n i n s e l e c t e d t i s s u e s o r f l u i d s , o r from t h e amount o f p e s t i c i d e o r m e t a b o l i t e e x c r e t e d from t h e body. Most s t u d i e s u s i n g b i o l o g i c a l m o n i t o r i n g methods have i n v o l v e d t h e c o l l e c t i o n o f b l o o d , urine, or both. P r i o r to designing a b i o l o g i c a l monitoring s t u d y , t h e p h a r m a c o k i n e t i c s ( i n c l u d i n g m e t a b o l i s m and e x c r e t i o n ) o f t h e p e s t i c i d e must be known s o t h a t t h e a p p r o p r i a t e t i s s u e o r f l u i d , as w e l l as t i m e p e r i o d s f o r m o n i t o r i n g , can be chosen. W i t h o u t t h i s i n f o r m a t i o n , e x t r a p o l a t i o n back t o dose i s not p o s s i b l e . E s t i m a t i n g o c c u p a t i o n a l exposure by p a s s i v e dosimetry o r b i o l o g i c a l m o n i t o r i n g o f f e r s d i s t i n c t advantages and d i s advantages (see T a b l e I ) . A major advantage o f b i o l o g i c a l m o n i t o r i n g i s t h a t , when t h e p h a r m a c o k i n e t i c s o f a p e s t i c i d e a r e u n d e r s t o o d s u f f i c i e n t l y , t h e a c t u a l a b s o r b e d dose may be c a l c u l a t e d . W i t h p a s s i v e d o s i m e t r y , o n l y t h e amount o f chemical p o t e n t i a l l y a v a i l a b l e f o r absorption or i n h a l a t i o n i s measured. T h i s amount o f c h e m i c a l i s t h e e x p o s u r e . U n l i k e b i o l o g i c a l monitoring, passive dosimetry requires independent e s t i m a t e s o f d e r m a l and l u n g a b s o r p t i o n t o



A c t u a l dose may b e m e a s u r e d . Unnecessary t o a d j u s t f o r value o f garment/protective c l o t h i n g . E f f e c t s o f comp l a c e n c y f a c t o r overcome.

a

a

Advantages Routes and a r e a s o f exposure a r e known. Routine experimental design and e x e c u t i o n . P a r t i c i p a n t under s u p e r v i s i o n of i n v e s t i g a t o r . G e n e r i c d a t a b a s e s may b e created.

C o n s i d e r e d most i m p o r t a n t .

Biological monitoring

Passive dosimetry

P h a r m a c o k i n e t i c s must b e known. Routes o f exposure cannot b e distinguished. D i f f i c u l t t o ensure p a r t i c i p a n t cooperation. P o t e n t i a l p r o b l e m s when u s i n g invasive techniques.

3

a

Disadvantages Dermal and r e s p i r a t o r y a b s o r p t i o n must be e s t i m a t e d . E x t r a p o l a t i o n from p a t c h t o body s u r f a c e a r e a must be made. Not a l l exposure s c e n a r i o s a r e amenable.

T a b l e I . THE PERCEIVED ADVANTAGES AND DISADVANTAGES OF ESTIMATING OCCUPATIONAL EXPOSURE WITH PASSIVE DOSIMETRY AND BIOLOGICAL MONITORING



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estimate dosage. These absorption estimates are generallyvery d i f f i c u l t to derive and interpret using a v a i l a b l e data from i n vivo and i n v i t r o systems. In addition, when using passive dosimetry, some assumptions concerning the value of normal clothes or protective clothing i n intercepting residues must a l s o be used to attempt to estimate actual dose. The major advantage with passive dosimetry i s that the r e l a t i v e contributions of the inhalation and dermal routes and of the d i f f e r e n t body areas to t o t a l dermal exposure can be r e a d i l y established. This i s extremely important f o r evaluating and recommending exposure mitigation measures. For example, i f i t can be demonstrated that a substantial f r a c t i o n of t o t a l exposure for a work day occurs to the hands, forearms, and face during the ten minutes a farmer pours the concentrated solution of a p e s t i c i d e formulation into the mix tank, t o t a l r i s k may be minimized by requiring chemical-resistant gloves, a face s h i e l d , and/or a closed mixing system for t h i s short duration/high exposure period. A b i o l o g i c a l monitoring study, which provides a composite p i c t u r e of dosage, would not d i s t i n g u i s h the various routes of exposure. In addition, since b i o l o g i c a l monitoring i s t y p i c a l l y c a r r i e d out a f t e r a complete work day, the r e l a t i v e contributions of the d i f f e r e n t work a c t i v i t i e s to t o t a l i n t e r n a l dose could not be distinguished, assuming the individual had engaged i n more than one work a c t i v i t y . Registrants have extensive experience with carrying out passive dosimetry studies where the study p a r t i c i p a n t s are t y p i c a l l y under the supervision of the investigator during the e n t i r e monitoring period. This i s generally not the case i n b i o l o g i c a l monitoring studies, f o r example, when 24-hour urine voids are c o l l e c t e d . Many passive dosimetry techniques require extrapolation from the residues on the small surface area of the trapping devices to e n t i r e body surface areas, a process which introduces an error f a c t o r . C r u c i a l areas of exposure may a l s o be missed. I t should be recognized that not a l l exposure scenarios are amenable to passive dosimetry techniques. Examples include measuring exposure t o p e s t i c i d e s i n swimming pools, i n dishwashing detergents, or measuring dermal exposure to v o l a t i l e organic chemicals. On the other hand, there are p o t e n t i a l l e g a l and e t h i c a l problems associated with the use of invasive techniques i n f i e l d studies. B i o l o g i c a l monitoring may hold some promise f o r dealing with what has been c a l l e d the "complacency f a c t o r . " I t i s widely recognized that when workers are handling p e s t i c i d e s that are known to be h i g h l y acutely t o x i c , e.g., parathion, extra care i s exercised. I t i s thought that the r e s u l t s of passive dosimetry studies may not e n t i r e l y capture t h i s extra care, and therefore may overestimate exposure for these p e s t i c i d e s . For example, i f during the course of a routine work cycle a worker's c l o t h i n g becomes contaminated, t h i s i n d i v i d u a l i s l i k e l y to change clothes prompted by h i s



25. LUNCHICK ET AL.

Special Review ofAlachlor

awareness o f t h e h i g h l y t o x i c n a t u r e o f t h e p e s t i c i d e b e i n g h a n d l e d . C o n v e r s e l y , i f d u r i n g a work a c t i v i t y d e s i g n e d t o m o n i t o r e x p o s u r e , some p e s t i c i d e impinges on a t r a p p i n g d e v i c e , w h i c h i n p r i n c i p l e does n o t a l l o w p e n e t r a t i o n t o the c l o t h i n g , work i s l i k e l y t o c o n t i n u e u n i n t e r r u p t e d t o t h e c o n c l u s i o n o f the monitoring p e r i o d . A r e l a t e d advantage o f p a s s i v e d o s i m e t r y i s the a b i l i t y t o create l a r g e generic databases. In t h i s context, " s u r r o g a t e " o r " g e n e r i c " d a t a a r e d e f i n e d as exposure monitoring data c o l l e c t e d f o r other p e s t i c i d e chemicals a p p l i e d u s i n g comparable a p p l i c a t i o n methods and under s i m i l a r c o n d i t i o n s as f o r t h e p e s t i c i d e under assessment. The mechanics o f t h e use o f s u r r o g a t e d a t a have b e e n d i s c u s s e d i n p u b l i c f o r a and i n t h e p u b l i s h e d s c i e n t i f i c l i t e r a t u r e i n recent years [ 1 - 4 ] . A b a s i c assumption i n the c r e a t i o n o f g e n e r i c d a t a b a s e s i s t h a t i n many a p p l i c a t i o n s c e n a r i o s , t h e p h y s i c a l p a r a m e t e r s o f a p p l i c a t i o n , and not t h e c h e m i c a l p r o p e r t i e s o f t h e p e s t i c i d e , a r e most i m p o r t a n t i n d e t e r m i n i n g t h e l e v e l o f e x p o s u r e . N o t e t h a t , when u s i n g p a s s i v e d o s i m e t r y methods, what i s measured i s t h e amount o f c h e m i c a l i m p i n g i n g on the s k i n s u r f a c e , o r a v a i l a b l e f o r i n h a l a t i o n , n o t t h e a c t u a l dose r e c e i v e d . F a c t o r s such as d e r m a l and l u n g p e n e t r a t i o n i n f l u e n c e t h e l a t t e r , and a r e , o f c o u r s e , e x p e c t e d t o be h i g h l y chemical-dependent. A r e v i e w o f a l l a v a i l a b l e i n f o r m a t i o n on p e s t i c i d e exposure d u r i n g a p p l i c a t i o n a c t i v i t i e s s u p p o r t s the use o f s u r r o g a t e d a t a f o r exposure a s s e s s m e n t s . Alachlor

Studies

I n November 1984, EPA i s s u e d t h e Guidance f o r t h e R e r e g i s t r a t i o n o f P e s t i c i d e P r o d u c t s C o n t a i n i n g A l a c h l o r as t h e A c t i v e Ingredient"! I n t h a t document, t h e Agency s t a t e d i t s d e t e r m i n a t i o n t h a t a l a c h l o r met one o f t h e r i s k c r i t e r i a ( o n c o g e n i c p o t e n t i a l ) used t o d e t e r m i n e whether i t causes u n r e a s o n a b l e a d v e r s e e f f e c t s [40 CFR 1 6 2 . 1 1 ( a ) ( 3 ) ( i i ) ( A ) ] . I n r e s p o n s e t o t h a t d e t e r m i n a t i o n , a S p e c i a l Review, i n w h i c h t h e r i s k s and b e n e f i t s o f c o n t i n u e d use o f a p e s t i c i d e a r e i n t e n s i v e l y examined, was i n i t i a t e d f o r a l a c h l o r i n December 1984. A l a c h l o r i s an a c e t a n i l i d e h e r b i c i d e t h a t has been p r o d u c e d i n t h e U n i t e d S t a t e s b y Monsanto C h e m i c a l Company s i n c e 1969. Almost a l l o f t h e a l a c h l o r used i n t h e U n i t e d S t a t e s i s a p p l i e d b y t r a c t o r - d r a w n ground boom s p r a y e r s . Monsanto s u b m i t t e d t h r e e b i o l o g i c a l m o n i t o r i n g s t u d i e s t o EPA t o s u p p o r t t h e c o n t i n u e d r e g i s t r a t i o n o f a l a c h l o r . I n a d d i t i o n , s u p p o r t i n g p h a r m a c o k i n e t i c s t u d i e s were e v a l u a t e d . These s t u d i e s i n d i c a t e d t h a t an a v e r a g e o f 87 p e r c e n t o f a l a c h l o r i n l a b o r a t o r y p r i m a t e s i s e x c r e t e d i n t h e u r i n e as m e t a b o l i t e s i n two c h e m i c a l c l a s s e s . U s i n g o n l y t h e s e d a t a , EPA was a b l e t o c a l c u l a t e t h e i n t e r n a l dosage o f a l a c h l o r , based on t h e t o t a l q u a n t i t y o f t h e two m e t a b o l i t e c l a s s e s , e x p r e s s e d as a l a c h l o r , measured i n t h e p a r t i c i p a n t ' s u r i n e . In the f i r s t o f the t h r e e s t u d i e s [ 5 ] , e i g h t a p p l i c a t o r s


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BIOLOGICAL MONITORING FOR PESTICIDE EXPOSURE were s t u d i e d b y Monsanto, f o u r u s i n g t h e L a s s o EC f o r m u l a t i o n and f o u r w i t h t h e L a s s o MT f o r m u l a t i o n . The a l a c h l o r was incorporated i n t o corn f i e l d s a t 4 l b a i per acre ( l b a i / A ) . The s u b j e c t s were Monsanto employees who wore g o g g l e s and e l b o w - l e n g t h r u b b e r g l o v e s d u r i n g m i x i n g and l o a d i n g , and b o o t s , t r o u s e r s , l o n g - s l e e v e d s h i r t , and a cap d u r i n g the e n t i r e o p e r a t i o n . The m i x i n g and l o a d i n g i n v o l v e d open p o u r i n g from t h e p e s t i c i d e c o n t a i n e r s . The a p p l i c a t i o n was conducted from e n c l o s e d cab t r a c t o r s and 20 a c r e s were t r e a t e d b y each s t u d y p a r t i c i p a n t . U r i n e was c o l l e c t e d p r i o r t o use o f a l a c h l o r and f o r f i v e days t h e r e a f t e r . The mean i n t e r n a l dosage f o r L a s s o EC was e s t i m a t e d t o be 0.0066 ug/kg bwt/lb a i . The second s t u d y [ 6 ] m o n i t o r e d t h e i n t e r n a l dosage r e c e i v e d d u r i n g m i x i n g , l o a d i n g , and a p p l y i n g L a s s o M i c r o Tech and L a s s o WDG. Four r e p l i c a t e s were monitored f o r each f o r m u l a t i o n and a l l s t u d y p a r t i c i p a n t s were Monsanto ©nployees. As i n t h e f i r s t s t u d y , t h e a l a c h l o r was i n c o r p o r a t e d i n t o c o r n f i e l d s a t 4 l b a i / A . Each i n d i v i d u a l t r e a t e d 20 a c r e s and a p p l i e d t h e a l a c h l o r from e n c l o s e d t r a c t o r cabs. The s t u d y p a r t i c i p a n t s wore l o n g - s l e e v e d s h i r t s and l o n g p a n t s a t a l l t i m e s and wore g o g g l e s , r u b b e r g l o v e s , and rubber o v e r s h o e s d u r i n g t h e m i x i n g and l o a d i n g . U r i n e was c o l l e c t e d p r i o r t o use o f a l a c h l o r and f o r f i v e days t h e r e a f t e r . The mean i n t e r n a l dosage o f a l a c h l o r was e s t i m a t e d t o be 0.0038 ug/kg b w t / l b a i f o r L a s s o M i c r o - T e c h and 0.0059 ug/kg b w t / l b a i f o r L a s s o WDG. The t h i r d s t u d y [ 7 ] m o n i t o r e d t h e i n t e r n a l dosage o f a l a c h l o r r e c e i v e d when a c l o s e d l o a d i n g system was employed d u r i n g m i x i n g and l o a d i n g and an e n c l o s e d t r a c t o r cab was u s e d t o i n c o r p o r a t e a l a c h l o r a t 4 l b a i / A . L a s s o EC was t h e f o r m u l a t i o n used and t h e f o u r s t u d y p a r t i c i p a n t s were Mons a n t o employees. The L a s s o EC was t r a n s f e r r e d from a 100g a l l o n b u l k tank t o t h e s p r a y t a n k s u s i n g a S c i e n c o pump. The workers wore l o n g - s l e e v e d s h i r t s , l o n g p a n t s , g o g g l e s , r u b b e r g l o v e s , and rubber overshoes d u r i n g t h e m i x i n g and l o a d i n g r o u t i n e . A l a c h l o r was i n c o r p o r a t e d i n t o c o r n f i e l d s a t 4 l b a i / A . E a c h p a r t i c i p a n t t r e a t e d 20 a c r e s from an e n c l o s e d t r a c t o r cab w h i l e w e a r i n g l o n g - s l e e v e d s h i r t s and l o n g p a n t s . U r i n e was c o l l e c t e d p r i o r t o u s i n g a l a c h l o r and f o r f i v e days a f t e r use. The Agency e s t i m a t e d t h e i n t e r n a l dosage o f a l a c h l o r t o be 0.0034 ug/kg b w t / l b a i . I t should be n o t e d t h a t most o f t h e u r i n e samples c o n t a i n e d n o n d e t e c t a b l e l e v e l s o f a l a c h l o r m e t a b o l i t e s and t h e Agency's dosage e s t i m a t e p r e d o m i n a n t l y r e f l e c t s 50 p e r c e n t o f t h e d e t e c t i o n l i m i t o f t h e a n a l y t i c a l method. The Monsanto dosage e s t i mate, w h i c h was l e s s t h a n t h e Agency's, r e f l e c t e d Monsanto's use o f "0" f o r samples c o n t a i n i n g n o n d e t e c t a b l e l e v e l s o f alachlor metabolites. S e v e r a l f a c t o r s p r e v e n t e d EPA from e s t i m a t i n g t h e r i s k t o u s e r s o f a l a c h l o r based s o l e l y on t h e s e b i o l o g i c a l m o n i t o r i n g s t u d i e s . The s t u d i e s were conducted w i t h o n l y f o u r r e p l i cates per f o r m u l a t i o n . S u b d i v i s i o n U of the P e s t i c i d e



25. LUNCHICK ET AL.


Assessment G u i d e l i n e s recommends t h a t 15 r e p l i c a t e s o f e a c h work t u n c t i o n be m o n i t o r e d . The study p a r t i c i p a n t s i n a l l t h r e e Monsanto s t u d i e s were employees o f M o n s a n t o . EPA p r e f e r s t h a t p a r t i c i p a n t s i n exposure s t u d i e s be experienced i n d i v i d u a l s who a r e b e i n g m o n i t o r e d w h i l e p e r f o r m i n g t h e i r n o r m a l work f u n c t i o n s t o more a c c u r a t e l y a s s e s s worker exposure. As p r e v i o u s l y discussed, the l a c k o f c o n t r o l over study p a r t i c i p a n t s i n c o l l e c t i n g urine voids i s a perceived d i s a d v a n t a g e o f b i o l o g i c a l m o n i t o r i n g . Monsanto b e l i e v e d t h e b e n e f i t s o f b e t t e r c o n t r o l o v e r u r i n e c o l l e c t i o n outweighed the b e n e f i t s o f u s i n g a c t u a l farmers and, t h e r e f o r e , e l e c t e d t o use i t s own employees t o m a i n t a i n c o n t r o l o v e r u r i n e collection. F i n a l l y , a l l r e p l i c a t i o n s i n v o l v e d the use o f e n c l o s e d t r a c t o r cabs d u r i n g s p r a y i n g . Enclosed t r a c t o r c a b s , when p r o p e r l y u s e d , p r o v i d e a n e f f i c i e n t p h y s i c a l b a r r i e r between t h e a p p l i c a t o r and t h e p e s t i c i d e s p r a y w h i c h w i l l reduce contact w i t h the p e s t i c i d e . Because t h e u s e o f e n c l o s e d t r a c t o r cabs i s n o t a r e q u i r e m e n t f o r t h e u s e o f a l a c h l o r , EPA c o n c l u d e d t h a t t h e dosage o f a l a c h l o r r e c e i v e d b y i n d i v i d u a l s on t r a c t o r s w i t h o u t c a b e n c l o s u r e s would b e g r e a t e r than that r e c e i v e d b y the i n d i v i d u a l s i n the three s u b m i t t e d Monsanto s t u d i e s . The c o n c e r n s s t a t e d above l e a d EPA t o c o n c l u d e t h a t t h e dosages e s t i m a t e d from t h e Monsanto b i o l o g i c a l m o n i t o r i n g s t u d i e s w o u l d n o t a c c u r a t e l y r e f l e c t t h e r a n g e o f dosages r e c e i v e d by a l l u s e r s o f a l a c h l o r i n the U n i t e d S t a t e s . A l a r g e range would b e e x p e c t e d b e c a u s e o f d i f f e r e n c e s i n s p r a y equipment, i n d i v i d u a l work h a b i t s , and v a r i a t i o n s i n e n v i ronmental c o n d i t i o n s a t the time o f a l a c h l o r use. In order t o e s t i m a t e the range o f exposure l i k e l y t o o c c u r d u r i n g t h e ground boom a p p l i c a t i o n o f a l a c h l o r , EPA e v a l u a t e d a Monsanto a p p l i c a t o r e x p o s u r e s t u d y and o t h e r e x p o s u r e s t u d i e s a v a i l a b l e i n t h e p u b l i s h e d l i t e r a t u r e w h i c h employed p a s s i v e dosimetry. EPA e v a l u a t e d a t o t a l o f s i x s t u d i e s [ 8 - 1 3 ] a v a i l a b l e i n the p u b l i s h e d l i t e r a t u r e that contained s u f f i c i e n t informa t i o n t o c o n d u c t an e x p o s u r e assessment f o r ground boom a p p l i c a t o r exposure. The s i x s t u d i e s c o n t a i n e d 101 r e p l i cates. The e x p o s u r e e s t i m a t e s were c a l c u l a t e d assuming t h a t t h e a p p l i c a t o r wore "normal" work a t t i r e c o n s i s t i n g o f l o n g p a n t s and a s h i r t . Because o f v a r i a t i o n s i n how t h e d a t a were r e p o r t e d and i n placement o f t h e p a t c h e s , t h e u s e o f a l o n g - s l e e v e d o r s h o r t - s l e e v e d s h i r t and t h e d e g r e e o f p r o t e c t i o n afforded by the s h i r t v a r i e d . T a b l e I I p r o v i d e s the mean e x p o s u r e s w i t h s p e c i f i c c l o t h i n g a s s u m p t i o n s u s e d f o r each study. In a d d i t i o n t o the s i x p u b l i s h e d s t u d i e s that were r e v i e w e d , a s e v e n t h s t u d y t h a t was c o n d u c t e d b y Monsanto w i t h a l a c h l o r was a l s o e v a l u a t e d [ 1 4 ] . In a l l c a s e s , the e x p o s u r e e s t i m a t e s were n o r m a l i z e d t o a n a p p l i c a t i o n r a t e o f 1.0 l b a i / a c r e t o p e r m i t c o m p a r i s o n o f e x p o s u r e w i t h o u t t h e a p p l i c a t i o n r a t e as v a r i a b l e . The e x p o s u r e e s t i m a t e s f o r t h e s e v e n g r o u n d boom a p p l i c a t o r s t u d i e s v a r i e d o v e r a range o f g r e a t e r t h a n two o r d e r s


333

Wang et al.; Biological Monitoring for Pesticide Exposure ACS Symposium Series; American Chemical Society: Washington, DC, 1988. 40.0

72.0

9.4

18

12

21

20

23

7

2

Abbott

Dubelman

Maitlen

Staiff

Wojeck

Wolfe

Monsanto

P o t e n t i a l dermal exposure reduced b y 80%

Short-sleeved s h i r t , long pants, 100% p r o t e c t i o n

Long-sleeved s h i r t , long pants, 100% p r o t e c t i o n



L o n g - s l e e v e d s h i r t , 50% p r o t e c t i o n Long p a n t s , 100% p r o t e c t i o n

Long-sleeved s h i r t , long pants, 50% p r o t e c t i o n

Clothing Assumptions

A l l e x p o s u r e e s t i m a t e s a r e b a s e d on a n a p p l i c a t i o n r a t e o f 1.0 l b a i / A .

0.15

0.40

0.70

0.93

Mean Exposure (mg/hr)

Number o f Replicates

Study Author

T a b l e I I . DERMAL EXPOSURE DURING GROUND BOOM APPLICATION



25. LUNCHICK ET AL.


o f magnitude from 0.15 mg/hr i n t h e Monsanto s t u d y t o 72 mg/hr i n t h e Wojeck s t u d y . T h i s v a r i a b i l i t y was n o t unexp e c t e d and r e s u l t e d from d i f f e r e n c e s i n equipment, weather, i n d i v i d u a l work h a b i t s , and s t u d y m e t h o d o l o g i e s . The Mons a n t o and Dubelman s t u d i e s i n v o l v e d a p p l i c a t i o n from e n c l o s e d t r a c t o r c a b s . The A b b o t t s t u d y u s e ! e n c l o s e d t r a c t o r cabs w i t h t h e r e a r window open. Open t r a c t o r s , e n c l o s e d t r a c t o r c a b s , h i g h c l e a r a n c e t r a c t o r s , and booms w i t h s h i e l d e d n o z z l e s were a l l used i n t h e Wojeck s t u d y . M a i t l e n , S t a i f f , and W o l f e d i d n o t d e s c r i b e t h e t r a c t o r s used; however, S t a i f f d i d s t a t e t h a t low p r e s s u r e s p r a y e r s were p a r t i a l l y r e s p o n s i b l e f o r t h e low exposure p o t e n t i a l o b s e r v e d i n t h a t s t u d y . EPA a l s o e s t i m a t e d t h e exposure r e c e i v e d d u r i n g m i x i n g / l o a d i n g when t h e p e s t i c i d e i s poured from t h e p e s t i c i d e c o n t a i n e r . The A b b o t t [ 8 ] and Monsanto [ 1 4 ] s t u d i e s p r o v i d e ! a t o t a l o f 20 r e p l i c a t e s i n w h i c h m i x e r / l o a d e r exposure c o u l d be e x p r e s s e d i n terms o f t h e amount o f a i h a n d l e d . The mean d e r m a l exposure f o r t h e 18 A b b o t t r e p l i c a t e s was 0.93 mg/lb a i . The two Monsanto r e p l i c a t e s had an e s t i m a t e d exposure o f 0.077 mg/lb a i . A l l e s t i m a t e s assumed t h a t t h e m i x e r / l o a d e r s wore p r o t e c t i v e g l o v e s . Conclusions I n e v a l u a t i n g t h e exposure d a t a from t h e p u b l i s h e d l i t e r a t u r e , EPA c o n c l u d e d t h a t d e r m a l exposure c o u l d v a r y o v e r a p p r o x i m a t e l y one o r d e r o f magnitude d u r i n g m i x i n g / l o a d i n g and o v e r two o r d e r s o f magnitude d u r i n g ground boom a p p l i c a t i o n . Based on t h e s e ranges, i t was assumed t h a t t h e combined exposure f o r m i x i n g / l o a d i n g and a p p l i c a t i o n would r e a s o n a b l y be e x p e c t e d t o v a r y o v e r two o r d e r s o f magnitude. The Monsanto p a s s i v e d o s i m e t r y s t u d y [ 1 4 ] p r o v i d e d t h e l o w e s t e s t i m a t e s f o r b o t h m i x e r / l o a d e r and ground boom a p p l i c a t o r exposures. Because t h e Monsanto b i o l o g i c a l m o n i t o r i n g s t u d i e s were conducted i n a s i m i l a r manner t o the Monsanto p a t c h s t u d y , EPA c o n c l u d e d t h a t t h e dosage e s t i m a t e s d e r i v e d from t h e b i o l o g i c a l m o n i t o r i n g s t u d i e s r e p r e s e n t e d t h e l o w e s t p o i n t o f a range o f dosages l i k e l y t o o c c u r d u r i n g t h e use o f a l a c h l o r . I t was f u r t h e r assumed t h a t t h e range o f dosage r e c e i v e d d u r i n g m i x i n g / l o a d i n g and ground boom a p p l i c a t i o n would a l s o v a r y o v e r two o r d e r s o f magnitude d e p e n d i n g on equipment used, c o n d i t i o n s o f t h e p r o t e c t i v e c l o t h i n g , weather c o n d i t i o n s , and i n d i v i d u a l work h a b i t s . As p r e v i o u s l y d i s c u s s e d , EPA c o n c l u d e d t h a t t h e dosages r e c e i v e d i n t h e Monsanto b i o l o g i c a l m o n i t o r i n g s t u d i e s d u r i n g open p o u r m i x i n g / l o a d i n g and e n c l o s e d cab ground boom a p p l i c a t i o n were 0.0066 ug/kg b w t / l b a i f o r L a s s o EC, 0.0038 ug/kg b w t / l b a i f o r L a s s o M i c r o - T e c h , and 0.0059 ug/kg b w t / l b a i f o r L a s s o WDG. EPA f u r t h e r c o n c l u d e d t h a t t h e d i f f e r e n t f o r m u l a t i o n s had no a p p r e c i a b l e e f f e c t on t h e dosage r e c e i v e d . T h e r e f o r e , t h e mean dosage o f t h e L a s s o EC, L a s s o M i c r o - T e c h , and L a s s o WDG f o r m u l a t i o n s was c a l c u l a t e d t o be 0.0054 ug/kg b w t / l b a i f o r t h e Monsanto s t u d y p a r t i c i p a n t s .


335

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336

EPA c o n c l u d e d t h a t 0.0054 ug/kg b w t / l b a i r e p r e s e n t e d t h e l o w end o f t h e range o f l i k e l y a l a c h l o r dosages and t h a t t h e range o f l i k e l y i n t e r n a l dosage would be 0.0054 t o 0.54 u g / k g b w t / l b a i f o r open pour m i x i n g / l o a d i n g and g r o u n d boom a p p l i c a t i o n . Based on t h e dosage e s t i m a t e o f 0.0034 ug/kg b w t / l b a i from t h e Monsanto b i o l o g i c a l m o n i t o r i n g s t u d y employing c l o s e d l o a d i n g systems and e n c l o s e d t r a c t o r cabs, EPA c o n c l u d e d t h a t t h e i n t e r n a l dosage o f a l a c h l o r r e c e i v e d u s i n g c l o s e ! l o a d i n g systems and ground boom a p p l i c a t i o n would range from 0.0034 t o 0.34 u g / k g / l b a i . T h i s c l o s e d l o a d i n g dosage may b e a n o v e r e s t i m a t e o f a c t u a l dosage, b e c a u s e i t r e f l e c t s t h e use o f 50 p e r c e n t o f t h e d e t e c t i o n l i m i t f o r t h e n o n d e t e c t a b l e u r i n e samples. The Agency's r e v i e w o f m i x e r / l o a d e r exposure d a t a i n d i c a t e s t h a t c l o s e d l o a d i n g systems p r o d u c e more t h a n a t w o - f o l d r e d u c t i o n i n t o t a l exposure. N o n t e c h n i c a l Summary S u b d i v i s i o n U o f t h e P e s t i c i d e Assessment G u i d e l i n e s p e r m i t s t h e use o f e i t h e r p a s s i v e d o s i m e t r y s t u d i e s t o e s t i m a t e worker exposure t o p e s t i c i d e s o r b i o l o g i c a l m o n i t o r i n g s t u d i e s t o e s t i m a t e i n t e r n a l dosage o f a p e s t i c i d e i n workers. D u r i n g t h e S p e c i a l Review o f A l a c h l o r , Monsanto s u b mitted three b i o l o g i c a l monitoring s t u d i e s which permitted EPA t o e s t i m a t e t h e dosage o f a l a c h l o r r e c e i v e d d u r i n g m i x i n g / l o a d i n g and ground boom a p p l i c a t i o n o f a l a c h l o r . EPA d i d n o t b e l i e v e t h a t t h e e s t i m a t e s from t h e s t u d y would p r e d i c t t h e a c t u a l range o f dosage r e c e i v e d d u r i n g use o f a l a c h l o r b y U.S. farmers b e c a u s e o f t h e l i m i t e d number o f r e p l i c a t e s , u s e o f Monsanto employees, and u s e o f o n l y e n c l o s e d t r a c t o r cabs. EPA e v a l u a t e d p a s s i v e d o s i m e t r y s t u d i e s i n w h i c h a l a c h l o r and o t h e r p e s t i c i d e s were a p p l i e d b y ground boom t o e s t a b l i s h a range o f e x p o s u r e s l i k e l y t o o c c u r d u r i n g a l a c h l o r use. T h i s range was t r a n s f e r r e d t o t h e b i o l o g i c a l m o n i t o r i n g s t u d y dosage e s t i m a t e s t o e s t a b l i s h a range o f i n t e r n a l dosage l i k e l y t o o c c u r d u r i n g a l a c h l o r u s e . This range o f i n t e r n a l dosage was u s e ! i n EPA's r i s k assessment f o r o c c u p a t i o n a l r i s k from a l a c h l o r u s e .

Literature Cited 1.

Severn, D . J . In Genetic Toxicology. An Agricultural Perspective; Fleck, R.A.; Hollaender, A . , Eds.; Plenum: New York, 1982; pp 235-242.

2.

Hackathorn, D.R.; Eberhart, D.C. In Dermal Exposure Related to Pesticide Use - Discussion of Risk Assess ment; Honeycutt, R.C.; Zweig, G . ; Ragsdale, N . N . , Eds.; American Chemical Society: Washington, DC, 1985; pp 341-355.



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3.

Honeycutt, R.C. In Dermal Exposure Related to Pesticide Use - Discussion of Risk Assessment; Honeycutt, R.C.; Zweig, G.; Ragsdale, N.N., Eds.; American Chemical Society: Washington, DC, 1985; pp 369-375.

4.

Reinert, J.C.; Severn, D.J. In Dermal Exposure Related to Pesticide Use - Discussion of Risk Assessment; Honeycutt, R.C.; Zweig, G.; Ragsdale, N.N., Eds.; American Chemical Society: Washington, DC, 1985; pp 357-368.

5.

Klein, J.J., et a l . Urinary Excretion of Alachlor Residue Following Normal Application of Lasso or Lasso Micro-Tech Herbicide Under Commercial Conditions in Indiana; Report No. MSL-4207; Monsanto Chemical Company, 1984.

6.

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