Chapter 2
Ways To Reduce Applicator Exposure to Pesticides J. E. Cowell, S. Dubelman, A. J. Klein, and K. Ohta
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Life Sciences Research Center, Environmental Science Department, Technology Division, Monsanto Agricultural Company, Chesterfield, MO 63198 Measurement of applicator exposure to pesticides has allowed scientists the opportunity to evaluate approaches to the reduction of exposure. Both passive dosimetry and b i o l o g i c a l monitoring applicator exposure studies have been performed by our department on various pesticides. In these studies, four general areas have been identified which have an effect upon reduction of worker exposure. These four areas encompass: worker apparel, product packaging, application equipment and personal hygiene. Worker clothing and rubber gloves have been found effective i n reducing personal exposure. Small container size and closed transfer systems have been found to be important in mixer/loader exposure reduction, while tractors with closed cabs have led to reduction i n application exposure. F i n a l l y , important factors i n the reduction of applicator exposure have been found to be the workers' level of instruction for use of the pesticides and the workers' individual personal hygiene practices. Scientists have been interested i n the measurement of worker exposure to pesticides since the 1950s. In 1962, Durham and Wolfe reviewed, i n d e t a i l , the methods available for measurement of the exposure of workers to pesticides.(I) In 1985, a f a i r l y comprehensive review of the l i t e r a t u r e from 1951-1984 was conducted by Turnbull (2). Basically there are two approaches used to measure exposure, and these approaches have not changed radically throughout the years. The f i r s t approach, pioneered by Durham and Wolfe measures the external deposition or the amount of pesticide with which the worker's body comes into contact. This approach i s u t i l i z e d primarily when l i t t l e information on the pharmacokinetics (absorption, metabolism and excretion) of the chemical i s available. The second approach i s the monitoring of the worker's body fluids (usually urine or blood) for levels of the pesticide or metabolites or for changes i n enzyme a c t i v i t y . 0097-6156/89/0382-0028$06.00/0 ° 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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2.
COWELL ET AL.
Ways To Reduce Applicator Exposure
T h i s has been c a l l e d b i o l o g i c a l m o n i t o r i n g . I f the pharmacokinet i c s o f a c h e m i c a l are known, t h e n as the World H e a l t h O r g a n i z a t i o n s t a t e s i n t h e i r 1982 p r o t o c o l , " B i o l o g i c a l m o n i t o r i n g p r o v i d e s a q u a n t i t a t i v e measure of the absorbed p e s t i c i d e r e s u l t i n g from exposure v i a a l l r o u t e s " ( 3 ) . Both approaches are v a l u a b l e i n t h a t each p r o v i d e s i n f o r m a t i o n t h a t the o t h e r does n o t . S i n c e most o f the exposure t o p e s t i c i d e i s from the dermal r o u t e , the Durham and Wolfe " p a t c h t e c h n i q u e " can e s t i m a t e the q u a n t i t y o f p e s t i c i d e t h a t comes i n t o c o n t a c t w i t h the s k i n . I t a l s o p r o v i d e s some i n f o r m a t i o n on the exposure a t s p e c i f i c s i t e s . T h i s has p r o v e n advantageous i n d e m o n s t r a t i n g avenues f o r exposure r e d u c t i o n ( 4 ) . The " b i o l o g i c a l m o n i t o r i n g t e c h n i q u e " a u t o m a t i c a l l y accounts f o r i n h a l a t i o n , o r a l exposure, c l o t h i n g p r o t e c t i o n and percutaneous a b s o r p t i o n w h i c h a l l have t o be assumed o r e s t i m a t e d v i a a d d i t i o n a l e x p e r i ments w i t h the p a t c h t e c h n i q u e ( 5 ) . W i t h s u f f i c i e n t pharmacokin e t i c d a t a , b i o l o g i c a l m o n i t o r i n g can p r o v i d e a q u a n t i t a t i v e measure o f the t o t a l body dose w h i c h p r e s e n t s the whole p i c t u r e o f the a p p l i c a t o r ' s exposure. T h i s c a p a b i l i t y proves v e r y advantageous i n making r i s k assessments. A l t h o u g h some f e e l t h a t the two t e c h n i q u e s cannot be p e r formed c o n c u r r e n t l y ( 6 ) , o t h e r s i n c l u d i n g m y s e l f f e e l t h a t the t e c h n i q u e s are c o m p a t i b l e ( 7 - 9 ) . With p r o p e r p a t c h placement and c o o r d i n a t e d hand washes, the t e c h n i q u e s can be combined t o g i v e the g r e a t e s t amount o f i n f o r m a t i o n from a s i n g l e s t u d y . Consider the f o l l o w i n g p o i n t s : 1. The patches are a t t a c h e d t o the o u t e r c l o t h i n g . Thus any n o r m a l l y exposed s k i n such as f a c e , hands o r neck would not be o b s t r u c t e d from p o t e n t i a l dermal d e p o s i t i o n o r p e n e t r a t i o n . 2. I n many s t u d i e s (10-14), normal c l o t h i n g has approached 100% p r o t e c t i o n from dermal d e p o s i t i o n and t h e r e f o r e i n these c a s e s , patches would have no d e l e t e r i o u s impact upon b i o l o g i c a l monitoring. 3. About 10 t o 12 patches a t 100 square c e n t i m e t e r s p e r p a t c h are used on the a p p l i c a t o r . These patches amount t o o n l y 1000 t o 1200 square c e n t i m e t e r s o f body s u r f a c e area w h i c h i s o n l y a p p r o x i m a t e l y 6% of the average t o t a l body s u r f a c e a r e a . 4. Thus the w o r s t case would be t h a t the b i o l o g i c a l monit o r i n g i s 6% too low. However i n h a l a t i o n and o r a l exposure would be u n a f f e c t e d , thus a 1.06 c o r r e c t i o n f a c t o r may be i n a p p r o p r i a t e . 5. Hand washes w i t h a l c o h o l i c / a q u e o u s s o l u t i o n s remove the p e s t i c i d e d e p o s i t e d on the hands (I) (15-18). Soap and warm water r i n s e s have a l s o been used. I t has been s t a t e d t h a t hand washes may not be a c c u r a t e s i n c e they do not account f o r the c h e m i c a l a l r e a d y absorbed (19) . The t e c h n i q u e o f hand washing i s n o t i n c o m p a t i b l e w i t h the conduct of a 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 s i n c e these hand washes j u s t s i m u l a t e the normal p e r s o n a l hygiene p r a c t i c e of the a p p l i c a t o r washing h i s hands a f t e r he f i n i s h e s working. Measurement 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 by b o t h types o f s t u d i e s has been used t o e v a l u a t e approaches t o the r e d u c t i o n of exposure (20-22). Data developed by our department i n many d i f f e r e n t s t u d i e s employing the p a t c h o r b i o l o g i c a l m o n i t o r i n g t e c h n i q u e s o r a t times b o t h , w i l l be used t o d e s c r i b e avenues
Wang et al.; Biological Monitoring for Pesticide Exposure ACS Symposium Series; American Chemical Society: Washington, DC, 1988.
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30
BIOLOGICAL MONITORING FOR PESTICIDE EXPOSURE
f o r exposure r e d u c t i o n . These i n d i v i d u a l s t u d i e s w i l l n o t be d e s c r i b e d i n t h e i r e n t i r e t y as some s t u d i e s have a l r e a d y been p u b l i s h e d , o t h e r s i n c l u d i n g methodology a r e d e s c r i b e d i n a companion paper i n t h i s symposium ( 3 5 ) , and y e t o t h e r s a r e t o be published. Four g e n e r a l areas have been i d e n t i f i e d f o r r e d u c t i o n o f worker exposure: 1. Worker A p p a r e l 2. P r o d u c t P a c k a g i n g 3. A p p l i c a t i o n Equipment 4. P e r s o n a l Hygiene I n t h e worker a p p a r e l a r e a , c l o t h i n g i t s e l f reduces exposure (23). S e v e r a l s t u d i e s have been performed u t i l i z i n g p a t c h e s on the o u t s i d e and i n s i d e o f c l o t h i n g a p p r o p r i a t e l y o f f s e t so as t o not i n t e r f e r e w i t h p e n e t r a t i o n o f normal c l o t h i n g . C o r r e c t i o n f a c t o r s o b t a i n e d by d i v i d i n g t h e o u t s i d e p a t c h r e s i d u e by t h e i n s i d e p a t c h r e s i d u e , when found, have t y p i c a l l y been i n t h e 215 to 530 f o l d range (24-25). A M i n o l t a videocamera has been used i n o u r s t u d i e s s i n c e 1983 and one p o s i t i v e e f f e c t o f t h i s v i d e o t a p i n g o f m i x e r / l o a d e r and a p p l i c a t i o n experiments has been t h e i d e n t i f i c a t i o n o f sources o f c o n t a m i n a t i o n . F o r i n s t a n c e , i n one study f o u r experiments t h a t c o n s i s t e d o f 2 i n d i v i d u a l s p e r f o r m i n g 2 r e p l i c a t e s o f m i x i n g / l o a d i n g and a p p l y i n g c h e m i c a l t o a 0.5 a c r e r i c e paddy each by a d i f f e r e n t mode, were viewed on tape and i t was observed t h a t some o f t h e i n s i d e p a t c h e s may have been contaminated upon removal from t h e a p p l i c a t o r ( 2 5 ) . D u r i n g r e p l i c a t e experiments t h e n e x t day w i t h t h e same i n d i v i d u a l s and c o n d i t i o n s , t h e i n s i d e p a t c h e s were c a r e f u l l y removed w i t h s o l v e n t r i n s e d f o r c e p s and t h e r e s u l t s o f these two s e t s o f e x p e r i m e n t a l a n a l y s e s can be seen i n T a b l e I :
Table I .
I n s i d e P a t c h A n a l y s e s (micrograms/square Backpack Spray - I n d i v i d u a l Number 1
centimeter)
DAY 2
DAY 1 Rep
1.
0.0134
Rep
1.
