27 Evaluation of Fluorescent Tracer Methodology for Dermal Exposure Assessment 1
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2
RICHARD A. FENSKE , JOHN T. LEFFINGWELL , and ROBERT C. SPEAR Downloaded via UNIV OF CALIFORNIA SANTA BARBARA on July 10, 2018 at 05:03:25 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
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Department of Environmental Science, Cook College, Rutgers University, New Brunswick, ΝJ 08903 Department of Biomedical and Environmental Health Sciences, University of California, Berkeley, CA 94720
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The feasibility o f employing f l u o r e s c e n t t r a c e r s and video imaging a n a l y s i s to quan tify dermal exposure to p e s t i c i d e a p p l i c a t o r s has been demonstrated under realistic field conditions. S i x workers loaded a t r a c e r w i t h the organophosphate pesticide, diazinon, i n t o a i r b l a s t s p r a y e r s , and conducted normal dormant s p r a y i n g in pear orchards. They were examined p r i o r to and immediately a f t e r the a p p l i c a t i o n . UV-A illumination produced fluorescence on the skin surface, and the p a t t e r n of exposure was digitized w i t h a video imaging system. Q u a n t i f i a b l e l e v e l s of t r a c e r were detected beneath cotton c o v e r a l l s on five workers. The distribution of exposure over the body surface v a r i e d widely due to d i f f e r e n c e s i n p r o t e c t i v e c l o t h i n g use, work p r a c t i c e s and environmental c o n d i t i o n s . This assessment method produced exposure values at v a r i a n c e w i t h those c a l c u l a t e d by the traditional patch technique. T h e n e e d t o q u a n t i t a t i v e l y e v a l u a t e d e r m a l e x p o s u r e among pesticide a p p l i c a t o r s has been r e c o g n i z e d s i n c e a t l e a s t 1954 (1). The work o u t l i n e d here represents a new approach to t h i s problem and p r o v i d e s suggestions for further research i n this f i e l d of exposure assessment. The tracing o f d e r m a l d e p o s i t i o n among applicators by means of f l u o r e s c e n t compounds was f i r s t u n d e r t a k e n in 1979 (2). Since t h a t time an instrument capable of measuring fluorescence directly on t h e s k i n has been developed and t e s t e d . The d e t a i l s o f t h e instrumental design and t h e n a t u r e o f the f l u o r e s c e n t compound em ployed as a t r a c e r have been d i s c u s s e d elsewhere (3)· This paper r e p o r t s the r e s u l t s o f i n i t i a l f i e l d investi g a t i o n s w i t h the method. 0097-6156/85/0273-0377$06.00/0 © 1985 American Chemical Society
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
378
DERMAL EXPOSURE RELATED TO PESTICIDE USE
The c o n c e p t u a l b a s i s o f t h i s t e c h n i q u e i s s t r a i g h t forward. A n o n - t o x i c f l u o r e s c e n t compound i s i n t r o d u c e d into a spray apparatus i n p r o p o r t i o n t o the pesticide being applied. Workers a r e asked t o conduct spray operations normally. Any c o n t a m i n a t i o n from m i x i n g and l o a d i n g , e q u i p m e n t a d j u s t m e n t o r s p r a y i n g i s e v i d e n c e d by t h e d e p o s i t i o n o f t r a c e r on t h e s k i n . Immediately following the spraying episode, t h e worker i s examined under long wave u l t r a - v i o l e t l i g h t i n o r d e r t o v i s u a l i z e t h e p a t t e r n of exposure on t h e body surface. The V i d e o Imaging Technique f o r Assessing Exposure, o r VITAE system, emp l o y s a t e l e v i s i o n camera i n t e r f a c e d w i t h a microcomputer to detect and q u a n t i f y f l u o r e s c e n c e on the skin. A standard curve relating l i g h t i n t e n s i t y t o amount of t r a c e r i s used t o determine t o t a l t r a c e r exposure. The ratio o f t r a c e r t o p e s t i c i d e i s e s t a b l i s h e d on t h e b a s i s of f i e l d s a m p l i n g , and t o t a l p e s t i c i d e e x p o s u r e r e p o r t e d . The i m p e t u s f o r t h i s s t u d y came f r o m a realization that t h e t r a d i t i o n a l p a t c h t e c h n i q u e (4) w a s inherently limited i n i t s a b i l i t y t o a c c u r a t e l y measure dermal exposure, and from t h e g r e a t p o t e n t i a l which a fluorescent t r a c e r methodology appeared t o h o l d . The a b i l i t y t o v i s u a l i z e exposure immediately provides v a l u a b l e q u a l i t a tive i n f o r m a t i o n regarding the exposure process. When combined w i t h a v i d e o image p r o c e s s i n g system which quant i f i e s fluorescence, the p o s s i b i l i t y of c a r e f u l l y characterizing dermal e x p o s u r e seemed w e l l w o r t h the effort involved. A t t h e o u t s e t i t was c l e a r t h a t t h e d e v e l o p m e n t o f a computer-based instrument and t h e use o f a surrogate compound ( t r a c e r ) w o u l d make t h e m e t h o d much more c o m p l e x than the t r a d i t i o n a l approach. Thus, the study has extended over s e v e r a l y e a r s , involving both laboratory and field tests. Appropriate fluorescent tracers were first screened, and their chemical and environmental c h a r a c t e r i s t i c s s t u d i e d . S i m u l t a n e o u s l y , t h e v i d e o image p r o c e s s i n g s y s t e m was d e s i g n e d a n d t e s t e d . S o f t w a r e was then developed t o run the system, and e v a l u a t i o n and quantification procedures established. Finally, the system was taken into the f i e l d to study applicators conducting routine spraying operations. Field
Study
Conditions
The f l u o r e s c e n t t r a c e r t e c h n i q u e was e m p l o y e d i n a n a p p l i c a t o r e x p o s u r e s t u d y i n L a k e C o u n t y , CA, i n J a n u a r y o f 1983. The f i e l d t r i a l was b a s e d a t t h e o f f i c e s o f t h e County Agricultural Commissioner and t h e U n i v e r s i t y of California Extension Service, approximately 200 miles north o f San F r a n c i s c o . The a g r i c u l t u r a l r e g i o n surrounding C l e a r L a k e was c h o s e n d u e t o t h e l i k e l i h o o d of r e c r u i t i n g owners o f s m a l l pear o r c h a r d s as s u b j e c t s . The study involved s i x applicators, and included a i r sampling, a modified v e r s i o n o f the dermal patch t e c h n i q u e , and t h e use o f a t r a c e r d u r i n g t h e s p r a y i n g o f
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
27.
Fluorescent
FENSKE ET AL.
Tracer
379
Methodology
the organophosphate, diazinon [0,0-diethyl 0-(2-isopropyl-6-methyl-4-pyrimidinyl) phosphorothioate]. Field conditions w e r e s t a n d a r d i z e d as much as p o s s i b l e f o r t h e six subjects, and a r e s u m m a r i z e d i n T a b l e I .
Table
Field
Trial
Application Parameter
1
2
3
4
5
6
Tank
loadings
3
4
4
4
2
1
sprayed
3.75
4
4
4
2
1
500
500
500
500
500
500
400
500
500
500
500
500
20
20
20
20
10
1200
1200
1200
1200
600
300
152
130
102
129
73
48
Acres
I.
Worker
Tank s i z e (gallons) Gallons sprayed per acre Total diazinon sprayed (lbs) Total tracer sprayed (gms) Spraying time (minutes)
The major manner :
A p p l i c a t i o n Parameters
v a r i a b l e s were c o n t r o l l e d
in
the
5
following
Equipment: A l l subjects employed tractor-powered air blast sprayers. A l l of the s p r a y e r s were c a l i b r a t e d to produce a h i g h v o l u m e a p p l i c a t i o n o f e i t h e r 400 o r 500 g a l l o n s per a c r e . Activity: The subjects were owner-operators and conducted both t h e i r own m i x i n g / l o a d i n g and spraying. The m o n i t o r i n g p r o t o c o l d i d n o t d i s t i n g u i s h b e t w e e n t h e s e two activities. The p e s t i c i d e and t r a c e r were added sequentially to the spray tank, with the worker i n s t r u c t e d t o t r e a t b o t h c o m p o u n d s i n t h e same m a n n e r . Pesticide: S u b j e c t s were each s u p p l i e d w i t h f o u r 5 lb. bags o f 50% w e t t a b l e powder f o r m u l a t i o n diazinon. The spray s c h e d u l e recommended by t h e U n i v e r s i t y o f C a l i f o r nia R e s e a r c h E n t o m o l o g i s t f o r p e a r p s y l l a and San Jose s c a l e was 5 l b s . p e r a c r e , a n d was f o l l o w e d b y a l l s u b jects except W o r k e r #1. E i g h t g a l l o n s of dormant o i l were a l s o a p p l i e d to each a c r e . Fluorescent Tracer : The F l u o r e s c e n t W h i t e n i n g A g e n t , 4methyl-7-diethylaminocoumarin, was e m p l o y e d a s a t r a c e r . T h i s compound i s commonly u s e d i n c o m m e r c i a l p r o d u c t s and h a s u n d e r g o n e t o x i c i t y t e s t i n g (1) (j>) . A 300 gm b a g of tracer was a d d e d w i t h e a c h 5 l b . bag o f d i a z i n o n 50% WP Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
DERMAL EXPOSURE RELATED TO PESTICIDE USE
380
( 1 1 3 4 gms a c t i v e i n g r e d i e n t ) , r e s u l t i n g i n a t r a c e r t a n k c o n c e n t r a t i o n o f 1 5 8 ppm, a n d a r a t i o o f 3 . 8 : 1 , pesticide: t r a c e r. Spray Period: S u b j e c t s w e r e a s k e d t o c o n d u c t f o u r comp l e t e spray cycles ( i . e . , four tank l o a d i n g s and sprayings). W o r k e r s #5 a n d #6 s p r a y e d f o r a s h o r t e r t i m e d u e to changes i n weather, a n d W o r k e r #1 made only three loadings due t o h i s d e c i s i o n t o spray h i g h e r concentrations. S p r a y t i m e s ranged from 40-152 m i n u t e s . Protective Clothing: The p e r s o n a l p r o t e c t i o n employed during t h e f i e l d t r i a l i s summarized i n Table I I . Resp i r a t o r s were used by a l l s u b j e c t s . Long s l e e v e cotton c o v e r a l l s and s h o r t s l e e v e c o t t o n T - s h i r t s were i s s u e d t o each s u b j e c t and were worn throughout t h e spray period. In some cases e x t r a s h i r t s and work pants were worn beneath t h i s c l o t h i n g . Weather: Most o f t h e s u b j e c t s took a very cautious a t t i t u d e toward wind c o n d i t i o n s . S p r a y i n g was n o t c o n d u c t e d u n l e s s t h e d a y was c a l m , and even then one o f t h e workers chose t o spray i n o n l y one d i r e c t i o n t o avoid drift. I n c r e a s i n g wind and t h e t h r e a t o f r a i n c u t s h o r t t h e s p r a y p e r i o d o f s u b j e c t s #5 a n d #6 o n t h e l a s t d a y o f the study. Materials
and Methods:
Environmental
Sampling
Environmental s a m p l i n g f o r t h e f i e l d t r i a l was g u i d e d b y three aims: 1) e s t a b l i s h m e n t o f e s t i m a t e s o f e x p o s u r e which allow comparison with other f i e l d s t u d i e s ; 2) d e termination o f l e v e l s o f p e s t i c i d e and t r a c e r i n the environment o f t h e worker; a n d 3) e v a l u a t i o n of the environmental stability of thetracer. The first a i m was a c c o m p l i s h e d by collecting p e r s o n a l a i r samples and employing a modified v e r s i o n o f the t r a d i t i o n a l patch technique. The second a i m r e q u i r e d a t t a c h i n g gauze monitors t o t h e spray r i g i n t h e v i c i n i t y of t h e worker. The f i n a l a i m i n v o l v e d spiking gauze m o n i t o r s w i t h known q u a n t i t i e s o f t h e t r a c e r a n d e x p o s i n g them to sunlight during the spraying episode. This c h a r a c t e r i z a t i o n of t h eenvironment o f t h eworker allowed estimation o f exposure independent o f t h e video imaging analysis, and provided information necessary f o rthe i n t e r p r e t a t i o n o f t h eVITAE system r e s u l t s . Air Sampling: P e r s o n a l a i r samples were c o l l e c t e d i n t h e b r e a t h i n g zone o f t h e worker f o r t h e e n t i r e s p r a y p e r i o d . A G i l i a n b a t t e r y p o w e r e d pump a t t a c h e d t o t h e b e l t was c o n n e c t e d t o a n o p e n - f a c e d 37mm c a s s e t t e w i t h a M i l l i p o r e filter, and t h e c a s s e t t e c l i p p e d t o t h e l a p e l of the coveralls. T h e pumps w e r e c a l i b r a t e d p r i o r t o a n d i m mediately after use.
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
27.
FENSKE ET AL.
Table
Fluorescent
I I .
Tracer
Personal
Protection During
P r o t e c t i v e G e a r w o r n by #2 #1
Body Part
baseball cap none
Head Face Hands Torso
(issued) (issued) Legs (issued) Feet Respiratory
rubber gloves thermal under wear coverall T-shirt thermal coverall rubber boots MSA dual cartridge
baseball cap eye glasses rubber gloves shirt + T-shirt coverall T-shirt jeans coverall rubber boots Pesticide dual cartridge
P r o t e c t i v e G e a r w o r n by #5 #4
Body Part Head Face Hands Torso
(issued) (issued) Legs (issued) Feet Respiratory
381
Methodology
Spray
Worker #3 hard hat face shield rubber gloves shirt + vest coverall T-shirt jeans coverall rubber boots MSA dual cartridge
Worker #6
plastic helmet face shield vinyl gloves none
hard h a t
hard hat
face shield polyeth gloves none
face shield rubber gloves shirt
coverall T-shirt none coverall plastic boots Pesticide dual cartridge
coverall T-shirt jeans coverall rubber boots Pesticide dual cartridge
T-shirt coverall T-shirt jeans coverall leather boots Pesticide dual cartridge
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
382
DERMAL EXPOSURE RELATED TO PESTICIDE USE
Personal Sampling: The dermal monitor employed is a modification of the t r a d i t i o n a l method of Durham and W o l f e (4), a n d was d e v e l o p e d a t t h e U n i v e r s i t y o f C a l i f ornia, Berkeley. The monitor c o n s i s t s of a solvente x t r a c t e d 1 2 - p l y s u r g i c a l g a u z e p a d ( 3 " χ 3")# b a c k e d by p o l y e t h y l e n e , and p l a c e d i n a p a p e r e n v e l o p e . The e n v e l o p e d e s i g n i n c l u d e s a 6 cm d i a m e t e r c i r c l e c u t o u t . Thus, t h e e x p o s e d g a u z e s a m p l i n g s u r f a c e i s 2 8 . 2 7 s q cm. When stapled t o g e t h e r t h i s a s s e m b l a g e becomes a s t u r d y unit, easily a t t a c h e d and removed f r o m a w o r k e r ' s c l o t h i n g or skin. Following a p r o t o c o l s i m i l a r to F r a n k l i n , et a l (2), and D a v i e s , e t a l (6), f o u r dermal m o n i t o r s were p l a c e d on e a c h w o r k e r , two on t h e o u t s i d e o f t h e c o v e r a l l , and two on the T - s h i r t beneath the c o v e r a l l in order to measure t h e amount o f p e s t i c i d e and tracer penetrating the outer garment. A l l o u t e r m o n i t o r s w e r e p l a c e d on t h e l e f t b r e a s t and r i g h t s h o u l d e r b l a d e ; a l l inner monitors w e r e p l a c e d on t h e r i g h t b r e a s t and l e f t s h o u l d e r b l a d e . Rig Samples : Three m o n i t o r s were a t t a c h e d to the top of the spray r i g ( i . e . , p a r a l l e l t o t h e g r o u n d ) a t t h e end n e a r e s t t h e t r a c t o r , a p p r o x i m a t e l y 150 cm f r o m t h e w o r k e r and 150 cm f r o m t h e t a n k opening for loading. This distance appeared s u f f i c i e n t to avoid contamination dur i n g m i x i n g and l o a d i n g . These s a m p l e s i n d i c a t e t h e l e v e l of p e s t i c i d e i n the environment of the worker, and pro vide a f u r t h e r measurement of the r a t i o of p e s t i c i d e to t r a c e r i n the a e r o s o l . Sun Samples: The f l u o r e s c e n t t r a c e r u s e d i n t h i s s t u d y can degrade when e x p o s e d t o d i r e c t s u n l i g h t (_3) . The e x t e n t o f t h i s d e g r a d a t i o n was m e a s u r e d b y p l a c i n g moni tors in the f i e l d . S i x monitors f o r each worker were spiked w i t h a m e a s u r e d amount o f t r a c e r i n acetonitrile just prior to each spray p e r i o d , and a l l o w e d to dry. Three of the m o n i t o r s were then p l a c e d i n d i r e c t s u n l i g h t i n an a r e a a d j a c e n t t o t h e s p r a y i n g , b u t w h e r e no expo sure to the spray would occur. The o t h e r t h r e e m o n i t o r s were n o t e x p o s e d t o s u n l i g h t and s e r v e d as c o n t r o l s . The time of s u n e x p o s u r e was n o t e d f o r t h e s p r a y p e r i o d of each worker. Field Blanks: Two f i e l d blanks f o r each worker were taken to the w o r k s i t e to monitor p o t e n t i a l sample con tamination. They were exposed i n the a r e a where samples w e r e p r e p a r e d and c o l l e c t e d , and t h e n h a n d l e d , s t o r e d and a n a l y z e d i n a manner i d e n t i c a l t o t h e o t h e r e n v i r o n m e n t a l samples. A l l values r e p o r t e d i n t h i s s t u d y have been adjusted for background l e v e l s of d i a z i n o n and tracer recovered from these samples. Analysis : A l l samples were p l a c e d lection, t r a n s p o r t e d f r o z e n to the i n a deep f r e e z e to await a n a l y s i s .
on d r y i c e upon col l a b o r a t o r y and p l a c e d The a i r and e n v i r o n -
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
27.
FENSKE ET AL.
Fluorescent
Tracer
Methodology
383
mental s a m p l e s were e x t r a c t e d and a n a l y z e d a c c o r d i n g to the procedures d e t a i l e d p r e v i o u s l y (3). Samples were p l a c e d i n 1 2 5 m l N a l g e n e b o t t l e s w i t h 30 m l acetonitrile (Baker " r e s i - a n a l y z e d " g r a d e ) and e x t r a c t e d on an o s c i l l a t i n g s h a k e r t a b l e f o r 90 m i n u t e s . The e x t r a c t i o n e f f i ciencies o f d i a z i n o n and t h e t r a c e r were 93% and 101%, respectively. D i a z i n o n s a m p l e s w e r e a n a l y z e d w i t h a T r a c o r 222 Gas Chromatograph equipped with a flame photometric d e t e c t o r i n t h e p h o s p h o r o u s mode. The d i a z i n o n s t a n d a r d e m p l o y e d was o b t a i n e d f r o m E P A , R e s e a r c h T r i a n g l e P a r k . The limit o f d e t e c t i o n o f t h e i n s t r u m e n t was 0.3 n g w i t h a maximum i n j e c t i o n v o l u m e o f 10 u l . S i n c e a l l e n v i r o n m e n t a l sam ples were extracted i n 30 m l o f s o l v e n t a n d were not c o n c e n t r a t e d , t h e s e n s i t i v i t y p e r s a m p l e was 900 ng. The e n v i r o n m e n t a l samples were a n a l y z e d f o r tracer w i t h a T u r n e r 430 S p e c t r o f l u o r o m e t e r a t f i x e d wavelengths ( e x c i t a t i o n = 356 nm; e m i s s i o n = 420 n m ) . Standards were interspersed with samples, and t h e amount of tracer present calculated by means o f a s t a n d a r d curve. The limit of d e t e c t i o n of the instrument f o r this compound was < 5 ppb, a l l o w i n g d e t e c t i o n o f l e v e l s a s l o w a s 150 ng p e r s a m p l e . Materials
and
Methods : Video
Imaging A n a l y s i s
Evaluation o f t r a c e r on t h e s k i n s u r f a c e was conducted with the VITAE system, following a protocol s i m i l a r to that described e l s e w h e r e (3). The system quantifies f l u o r e s c e n c e i n t e n s i t y i n the f o l l o w i n g manner: a tele vision camera scans the s u r f a c e a r e a of a body part 30 times per second. A video d i g i t i z e r i n the computer takes one of these scans, c o n v e r t s the analog camera output t o d i g i t a l v a l u e s o n t h e b a s i s o f a 16 l e v e l g r e y scale, a n d d i s p l a y s t h e i m a g e o n a TV m o n i t o r . The d a t a is then stored on d i s k and is available for later analysis. The l i g h t i n g s y s t e m e m p l o y e d c o n s i s t e d o f BLB bulbs (black l i g h t s ) with f i l t e r s . T h e i n t e n s i t y o f UV-A light to which s u b j e c t s w e r e e x p o s e d was e v a l u a t e d prior to e x a m i n a t i o n w i t h a UVX R a d i o m e t e r (UV P r o d u c t s ) . With a l i g h t - t o - s u b j e c t d i s t a n c e o f 90 cm, t h e m a x i m u m l o n g w a v e UV i l l u m i n a t i o n was 210 u w a t t s / s q cm. The r e l a t i v e s t a n dard deviation o f 49 r e a d i n g s t a k e n i n a 70 cm χ 70 cm r e g i o n was 4%. B o t h p r e - and p o s t - e x p o s u r e images were taken of a l l body r e g i o n s above the w a i s t f o r each sub ject, resulting i n a t o t a l o f 30 p a i r s o f v i d e o images per subject (Table I I I ) . The l e g s and t h e i n s i d e s of the u p p e r arms were o m i t t e d i n t h i s t r i a l due t o diffi culties in subject positioning. The camera-to-subject distance was v a r i e d b e t w e e n 70 a n d 80 cm, and a t times t h e c a m e r a was m o v e d up o r d o w n t o a c c o m m o d a t e t h e loca tion of the body p a r t . A f i x e d a p e r t u r e of f/1.4 was employed throughout the study. A s t a n d a r d t a r g e t was r e a d a t 1 0 5 cm ( f / 1 . 4 ) prior to and immediately f o l l o w i n g each examination period. Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
DERMAL EXPOSURE RELATED TO PESTICIDE USE
384 Table
I I I .
Body Part
Body P a r t s f o r V i d e o # Images Recorded
H a n d s (1) F o r e a r m (2) U p p e r A r m (2)
4 8 6
Head
4
(1)
Upper Torso
(1)
4
Lower Torso
(1)
4
Imaging A n a l y s i s
Anatomical
Boundaries
up t o t h e w r i s t s w r i s t s t o t h e elbow elbow t o t h e shoulder ( e x c l u d e s i n s i d e s o f arms) i n c l u d e s neck s i d e s and back neck t o b r e a s t ( i n c l u d e s f r o n t o f neck) breast to waist
T h i s measurement s e r v e d as an i n d i c a t o r o f t h e s t a b i l i t y of t h e system t h r o u g h o u t t h e s i x d a y f i e l d t r i a l . Readings o f these t a r g e t s a r e expressed as i n t e g r a t e d i n t e n s i t y , or counts. T h e t w e l v e r e a d i n g s r a n g e d f r o m 6709 t o 7414 counts, w i t h a mean v a l u e o f 6986 counts, and a s t a n d a r d d e v i a t i o n o f 157 (RSD = 2 . 2 5 % ) . This low v a r i ability c a n be c o n s i d e r e d n e g l i g i b l e f o r purposes of exposure quantification. R e d u c t i o n a n d a n a l y s i s o f t h e v i d e o i m a g i n g d a t a was conducted i n the laboratory following the field trial. The steps i n v o l v e d i n t h e c a l c u l a t i o n o f exposure from video images have been d e t a i l e d elsewhere {3), and a r e summarized here. A v a r i a b l e background r e f l e c t a n c e from t h e s k i n i s commonly o b s e r v e d w i t h t h i s system. Images of t h e v a r i o u s body p a r t s must be r e c o r d e d p r i o r t o t h e worker's exposure t o provide b a s e l i n e data. Thus, t h e area o f i n t e r e s t f o r q u a n t i f i c a t i o n on t h e A f t e r image (post-exposure) i s o u t l i n e d and superimposed onto the Before image, and background variability eliminated. Images a r e then corrected f o r lens distortions and changes i n d i s t a n c e , and a d j u s t e d f o r t h e nonplanar c h a r a c t e r i s i t i c s o f t h e v a r i o u s body p a r t s . A standard curve developed i n the l a b o r a t o r y serves as t h e b a s i s f o r t r a n s f o r m i n g a d j u s t e d l i g h t i n t e n s i t y t o amount o f t r a c e r on t h e s k i n s u r f a c e . R a t i o s o f p e s t i c i d e t o t r a c e r based on evironmental samples a l l o w c a l c u l a t i o n o f pesticide exposure. Laboratory s t u d i e s have demonstrated that p e s t i c i d e s a n d t r a c e r compounds p e n e t r a t e c o t t o n c o v e r a l l f a b r i c a t d i f f e r e n t r a t e s (3). Thus, an e m p i r i c a l penet r a t i o n f a c t o r o f 3.4:1 ( p e s t i c i d e t o t r a c e r ) i s e m p l o y e d in the final calculation o f exposure f o r protected regions. Results
and D i s c u s s i o n :
Environmental
Sampling
Air Samples: A i r s a m p l i n g d a t a p r o v i d e d t h e most d i r e c t means o f comparing l e v e l s of p e s t i c i d e i n t h e workplace from this study with those i n previous ones. The sampling d e v i c e s employed a r e very c l o s e t o s t a n d a r d , and Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
27.
FENSKE ET AL.
Fluorescent
Tracer
385
Methodology
the procedures f o r determining p o t e n t i a l exposure explic i t and g e n e r a l l y u n i f o r m . The r e s u l t s f r o m a i r samples in this study are presented i n Table IV. Four of the workers had s i m i l a r potential respiratory exposure, ranging from 8.6 t o 30 ug/cu meter. The sample of worker #6 h a d no detectable level of pesticide, p r e s u m a b l y due t o h i s s p r a y i n g o n l y one t a n k . The p o t e n tial e x p o s u r e o f w o r k e r #1 was n e a r l y a n o r d e r o f m a g n i tude greater than the other s u b j e c t s . A l l s u b j e c t s wore d u a l c a r t r i d g e , half-mask r e s p i r a t o r s d u r i n g s p r a y i n g , so l i t t l e i f any r e s p i r a t o r y exposure a c t u a l l y o c c u r r e d .
Table
IV.
A i rSampling
Results
Worker #
Time Spraying hrs
diazinon Concentration ug/cu meter
Potential Resp Exposure ug/hr
1 2 3 4 5
83 141 102 129 73
202.11 30.39 8.55 23.37 14.99
351.7 52.9 14.9 40.7 26.1
* Assumes a t i d a l volume o f 1740 l i t e r s A l l w o r k e r s wore r e s p i r a t o r s .
per hour.
In a p r e v i o u s a p p l i c a t o r s t u d y (2), a range o f 20110 u g / c u m e t e r was o b s e r v e d . The e x p o s u r e r a n g e o f 8.6202 u g / c u m e t e r i n t h i s s t u d y i s b r o a d e r , but of similar magnitude. Data from W o l f e e t a_l ( 7 - 8 ) i n d i c a t e an exposure range o f 6-167 u g / c u m e t e r , quite similar to levels recorded i n this study. Based on a i r s a m p l i n g , then, exposures appear t o be w i t h i n a normal range f o r mixer/loader/applicators employing a i r blast spraying equipment. Sun Samples : The c o m p a r i s o n o f e x p o s e d s p i k e d samples w i t h c o n t r o l s a l l o w s d e t e r m i n a t i o n o f t h e amount o f tracer lost during a t y p i c a l spray episode, and c a l c u l a t i o n of a c o r r e c t i o n f a c t o r f o r t h e e n v i r o n m e n t a l samples of each worker. V a r i a b i l i t y among t h r e e r e p l i c a t e s a m p l e s w a s l o w , w i t h r e l a t i v e s t a n d a r d d e v i a t i o n s l e s s t h a n 5%. S i n c e s u n l i g h t i n t e n s i t y and o t h e r e n v i r o n m e n t a l factors v a r i e d c o n s i d e r a b l y from day t o day and worker t o w o r k e r , it was n o t p o s s i b l e t o c a l c u l a t e a r a t e o f d e g r a d a t i o n . The l o s s o f t r a c e r r a n g e d f r o m 7% t o 2 2 % , w i t h approximately 10-15% l o s t i n two h o u r s . These r e s u l t s were q u i t e s i m i l a r to those observed i n c o n t r o l l e d studies of t r a c e r s t a b i l i t y (3). The p e r c e n t l o s s d u r i n g t h e s p r a y episode i s employed t o c o r r e c t f o r l o s s from t h e r i g and p e r s o n a l samples of each worker.
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
386
DERMAL EXPOSURE RELATED TO PESTICIDE USE
Rig Samples: Samples a t t a c h e d t o t h e spray r i g during the application p r o v i d e an i n d i c a t i o n of the aerosol c o n c e n t r a t i o n o f t h e two compounds i n t h e v i c i n i t y o f t h e worker. R e s u l t s a r e p r e s e n t e d i n T a b l e V. Mean p e s t i cide l e v e l s r a n g e f r o m 1.3 t o 4 5 . 2 3 u g / s q cm, a n d m e a n t r a c e r l e v e l s f r o m 0.49 t o 1 7 . 3 4 u g / s q cm. Analysis of
Table
V.
Exposure L e v e l s based on R i g Samples ( a l l v a l u e s i n m i c r o g r a m s / s q cm)
worker
mean diazinon
std dev
1 2 3 4 5 6
6.28 45.20 1.29 44.70 19.28 1.86
0.3 1.7 0.3 1.7 2.6 0.3
Note:
mean tracer 0.97 17.34 0.22 9.70 3.36 0.49
std dev
Ratio d:t
0.1 2.2 0.05 1.7 0.4 0.1
6.5 2.6 5.9 4.6 5.7 3.8
Ν = 3 i n a l lc a s e s
these v a l u e s by l i n e a r r e g r e s s i o n r e v e a l s a h i g h l ys i g ( r = 0.92, nificant c o r r e l a t i o n of t r a c e r and p e s t i c i d e ρ < .00001, η = 1 8 ) . The r e l a t i v e l y h i g h l e v e l s o f t r a cer recovered from t h e samples o f Worker #2 tend to reduce the linearity of this relationship. I f h i s data i s omitted from t h e a n a l y s i s t h e c o r r e l a t i o n i s improved (r = 0.984, ρ < .000001, η = 1 5 ) . T h e s e same r e l a t i o n ships a r e a l s o e v i d e n t from t h e r a t i o s o f p e s t i c i d e to t r a c e r shown i n t h e t a b l e . The r a n g e o f r a t i o s i s 2.61 t o 6.47. I f W o r k e r #2 i s e x c l u d e d , however, t h e range narrows markedly (3.80-6.47). I t i s n o t a p p a r e n t why t h e concentration of tracer on t h e s p r a y r i g m o n i t o r s of Worker #2 w a s e l e v a t e d r e l a t i v e t o t h e o t h e r subjects. I t i s p o s s i b l e t h a t t h e samples r e c e i v e d d i s p r o p o r t i o n a t e t r a c e r exposure d u r i n g mixing and l o a d i n g . I t s h o u l d be noted from Table V t h a t four o f t h e s i xc a l c u l a t e d s t a n dard r a t i o s a r e h i g h e r t h a n t h e 3.8:1 r a t i o o f t h e two compounds when introduced into the spray tank. These r e s u l t s i n d i c a t e a lower water s o l u b i l i t y f o r t h e t r a c e r than f o r t h e w e t t a b l e powder f o r m u l a t i o n of diazinon. This finding was c o r r o b o r a t e d by h i g h r a t i o s found i n samples o f t h e tank mix taken p r i o r t o s p r a y i n g . The ratio o f p e s t i c i d e t o t r a c e r i s an essential calibration factor f o r t h e VITAE system's exposure assessment. The r a t i o s d e r i v e d from t h e r i g samples a r e mean values o f three samples, and a r e thus t h e most statistically reliable indicators of the aerosol ratio among t h e m e a s u r e m e n t s t a k e n . In this study, therefore, these r a t i o s a r e employed t o t r a n s f o r m t r a c e r t o p e s t i cide. F u r t h e r i n v e s t i g a t i o n w i l l be n e c e s s a r y t o d e t e r m i n e how b e s t t o d e f i n e t h e s e v a l u e s .
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
27.
FENSKE ET AL.
Fluorescent
Tracer
387
Methodology
Personal Samples: D a t a f r o m t h e g a u z e p a t c h e s on t h e outside of the coveralls, and on t h e T - s h i r t i m m e d i a t e l y beneath the coveralls are presented i n Table VI with values e x p r e s s e d a s m i c r o g r a m s p e r s q cm o f g a u z e moni tor. Consistent with t h e data from t h e r i g samples, Workers #2, #4, a n d #5 s h o w r e l a t i v e l y h i g h l e v e l s of t r a c e r a n d p e s t i c i d e , w h i l e W o r k e r s #3, a n d #6 r e v e a l l o w levels. Worker #1 i s a n o m a l o u s , i n that h i s personal samples are relatively high, whereas t h e r i g samples p o i n t toward a moderate exposure.
Table
E x p o s u r e L e v e l s based on P e r s o n a l ( a l l v a l u e s i n m i c r o g r a m s / s q cm) chest Τ
work #
outer D*
chest T*
inner D
1 2 3 4 5 6
12.45 11.94 1.36 11.39 4.23 .53
6.83 7.20 .19 1.70 .49 .07
1.10
.21 .24
.01
.28
— —
— —
— — —
m i s s i n g v a l u e s were l e s s values D = diazinon, Τ = tracer
Note: *
VI.
outer D
back Τ
.99 3.40 .88 6.30 1.93 .54
.68 .62 .13 .54 .17 .08
than
2 times
Samples
inner D
back Τ
.04 .04
—
.12 05
— field
— blank
I n a c c o r d w i t h many p r e v i o u s f i e l d o b s e r v a t i o n s , t h e patches placed on t h e c h e s t o f f i v e o f t h e s i x w o r k e r s are m a r k e d l y h i g h e r than t h o s e on t h e b a c k . Such dif ferential e x p o s u r e c a n be t e n t a t i v e l y a t t r i b u t e d t o two factors: c o n t a m i n a t i o n o f t h e samples d u r i n g m i x i n g and loading, and the forward motion o f the worker during s p r a y o p e r a t i o n s c a u s i n g g r e a t e r d e p o s i t i o n on t h e front of t h e body. The levels beneath t h e c o v e r a l l s were t o o low t o q u a n t i f y i n most c a s e s . Four workers appear t o have had penetration o f low l e v e l s o f p e s t i c i d e or t r a c e r . Only W o r k e r #1, w h o s e o u t e r c h e s t p a t c h i s a l s o h i g h , a p p e a r s to have been s i g n i f i c a n t l y exposed beneath t h e coveralls based on t h e s e d a t a (i.e., p e s t i c i d e exposure > 1 ug/sq cm) . The p e r s o n a l s a m p l e s o n t h e c h e s t a n d b a c k a l l o w an estimate of pesticide e x p o s u r e based on the standard technique o f e x t r a p o l a t i n g from p a t c h t o t o t a l body r e gion. The s t a n d a r d method o n l y considers unprotected regions o f t h e body t o be exposed. In this case, only the head and neck o f t h e workers a r e u n p r o t e c t e d , and i n f o u r o f s i xcases face s h i e l d s were worn. Thus, beyond a comparison o f h e a d a n d n e c k e x p o s u r e f o r w o r k e r s #1 a n d #2, i t i s n o t c l e a r how t h e p a t c h t e c h n i q u e could be applied i n this study. Later i n t h i s paper the patch data will be e m p l o y e d t o make t h i s comparison. These Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
388
DERMAL EXPOSURE RELATED TO PESTICIDE USE
e x p o s u r e v a l u e s w i l l t h e n be compared w i t h from t h e video imaging a n a l y s i s . Results
and D i s c u s s i o n :
Video
Imaging
those
derived
Analysis
The Before and A f t e r v i d e o images f o r each worker were analyzed by t h e VITAE system t o determine t h e e x t e n t of exposure. Results a r epresented i n Table V I I . Workers # 3 , # 4 , # 5 , a n d #6 e x h i b i t o n l y m i n o r e x p o s u r e . I t should be r e c a l l e d t h a t a l l o f these w o r k e r s wore f a c e shields throughout t h e study period, and two sprayed f o r r e l a tively short periods.
Diazinon Exposure* Table VII. ( a l l values in micrograms) Body Parts**
1
2
W o r k e r No. 4 3
5
6
Hands LF Arm RF A r m LU A r m RU A r m Torso Head
551.6 1014.3 1536.6 329.8 400.2 631.3 995.7
118.1 61.2 0 11.6 56.2 94.5 146.2
212.3 0 0 0 0 0 0
99.8 0 127.0 0 0 0 35.9
0 0 0 0 130.6 0 115.0
0 55.8 0 0 0 0 0
TOTAL
5459.2
487.8
212.3
262.7
245.6
55.8
F l u o r e s c e n t t r a c e r exposure values have been a d j u s t e d by r a t i o o f d i a z i n o n to t r a c e r f r o m T a b l e V. ** R e g i o n s p r o t e c t e d b y c o v e r a l l s h a v e a l s o b e e n a d j u s t e d by a c l o t h i n g p e n e t r a t i o n f a c t o r o f 3.4. F o r W o r k e r s #1 a n d #2 t h e p e n e t r a t i o n f a c t o r h a s b e e n a p p l i e d t o t h e c h e s t b u t n o t t o t h e neck which r e mained unprotected.
*
T h e h a n d e x p o s u r e o f W o r k e r #3 i s u n d o u b t e d l y d u e t o his unique p r a c t i c e o f mixing and l o a d i n g w i t h gloves on, but s p r a y i n g w i t h no g l o v e s . His cautious practice of spraying i n o n l y one d i r e c t i o n t o a v o i d d r i f t appears t o have eliminated exposure t o the aerosol itself. The detection o f e x p o s u r e t o t h e f o r e a r m s o f w o r k e r s #4 a n d #6 c o r r o b o r a t e s v i s u a l o b s e r v a t i o n s . I t was n o t e d d u r i n g examination that a ring of diffuse fluorescence extended completely around t h e forearms, approximately 1 0 cm a b o v e the w r i s t s . Discussion with these workers revealed that the exposure ocurred j u s t a t t h e t o p o f t h e rubber gloves which they a l l employed. Since the coverall sleeves a r e n o t s e c u r e d i n a n y w a y , i t a p p e a r s t h a t t h i s e x p o s u r e may be d u e t o movement o f t h e g l o v e s a n d c o v e r a l l s a t this j u n c t i o n , rather than t h e r e s u l t o f c l o t h i n g p e n e t r a t i o n . The c a u s e o f t h e u p p e r a r m e x p o s u r e o f w o r k e r #5 i s n o t e v i d e n t , b u t may h a v e r e s u l t e d f r o m c o n t a c t w i t h c o n t a m i nated equipment. Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
27.
FENSKE ET AL.
Fluorescent
Tracer
Methodology
389
Exposure a t t h e base o f t h e neck o f Worker #4 w a s apparent during the examination. I t appeared as a high l i g h t i n t e n s i t y spot o f c i r c u l a r shape. The w o r k e r s u g gested d u r i n g d i s c u s s i o n t h a t t h e p l a s t i c helmet he wore d u r i n g a p p l i c a t i o n may h a v e c o l l e c t e d t h e a e r o s o l a n d a l lowed i t t o d r i p onto h i s back. W h i l e w o r k e r s #4 a n d #5 received exposure t o t h e head, only deposition to the sides of the face occurred. In fact, thepoint just i n front of the ear a t which the face s h i e l d s ended was clearly demarcated. Thus, t h e face s h i e l d s appear to have b e e n v e r y e f f e c t i v e i n r e d u c i n g a n d i n some cases e l i m i n a t i n g f a c i a l exposure. Quantifiable l e v e l s o f t r a c e r were d e t e c t e d on a l l b o d y p a r t s o f W o r k e r #1, a n d i n 25 o f 30 v i e w s . B a s e d on data i n Table V I I , the highest levels occurred on t h e forearms. I t i slikely, however, that exposure t o the head was g r e a t e r t h a n t h e s e f i g u r e s r e f l e c t . As noted previously, a f i x e d f / 1 . 4 a p e r t u r e was e m p l o y e d throughout the study. L a t e r a n a l y s i s o f t h e images revealed t h a t a s i g n i f i c a n t number o f p i x e l s f r o m t h e h e a d images were a s s i g n e d t h e maximum g r e y l e v e l o f 1 5 , indicating detector saturation. Considering the extremely high exposure which t h i s worker received t o t h e face, i ti s likely t h a t q u e n c h i n g a l s o came i n t o p l a y , contributing to an a r t i f i c i a l l y low value. These f a c t o r s d i d not appear t o o b t a i n f o r any o f t h e o t h e r images examined. Worker #2 e x h i b i t s the pattern of exposure which might have been p r e d i c t e d f o r a l l workers. The exposed region o f t h e head (no f a c e s h i e l d ) was h i g h e s t . The hands were a l s o h i g h , despite the use of gloves. However, elevated l e v e l s were a l s o d e t e c t e d beneath prot e c t i v e c l o t h i n g . S i n c e t h i s worker wore a f l a n n e l s h i r t and T-shirt i n addition to the T-shirt and c o v e r a l l s issued, i t was m o s t s u r p r i s i n g t o d e t e c t e x p o s u r e t o t h e chest. The v a l u e f o r t o r s o e x p o s u r e i n t h e t a b l e i n cludes both a p r o t e c t e d region (chest) and an exposed region (front of neck). Chest exposure alone accounted f o r 78 u g o f t h e 94 u g e x p o s u r e . The c a l c u l a t i o n o f e x p o s u r e b a s e d o n t h e p a t c h t e c h nique t r a d i t i o n a l l y employs t h e s i m p l i f y i n g assumption that c l o t h i n g p e n e t r a t i o n does n o t o c c u r , o r does n o t contribute s i g n i f i c a n t l y t o t o t a l exposure. Based on t h e f l u o r e s c e n t t r a c e r d a t a i t seems r e a s o n a b l e t o a r g u e t h a t this a s s u m p t i o n may b e i n a p p r o p r i a t e . Table VIII pres e n t s t h e p e r cent o f exposure o c c u r r i n g on both exposed and protected regions. Not s u r p r i s i n g l y , the patterns are h i g h l y v a r i a b l e as they a r e a f f e c t e d by both protective c l o t h i n g and work p r a c t i c e s . F o r t h e two workers w i t h e x p o s u r e t o n e a r l y a l l body r e g i o n s , p r o t e c t e d a r e a s accounted f o r 4 2 % (#2) a n d 7 1 % (#1) o f t o t a l exposure. In some c a s e s h a n d s may a c c o u n t f o r a l l e x p o s u r e ( # 3 ) , while i n o t h e r s t h e y may r e p r e s e n t a relatively small contribution. The c a l c u l a t i o n o f exposure by t h e p a t c h technique a l s o assumes t h a t d e p o s i t i o n o f p e s t i c i d e i s u n i f o r m over
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
390
DERMAL EXPOSURE RELATED TO PESTICIDE USE
Table
Region
Per
VIII.
1
Hands Head Coverall Protected
10 19 71
Cent of Exposure
2
3 24 33 42
100 0 0
to Body
W o r k e r No. 4 38 14 48
Regions
5
6
0 47 53
0 0 100
each body p a r t r e p r e s e n t e d by a p a t c h . It is evident from q u a l i t a t i v e e x a m i n a t i o n o f t h e w o r k e r s and recorded images that the d i s t r i b u t i o n of exposure over a given body r e g i o n ( e . g . , head, hands, forearm) i s not uniform. Such an e x p o s u r e p a t t e r n w o u l d c l e a r l y be an exception. T h e m o r e common p a t t e r n i s t h e a p p e a r a n c e o f a " h o t s p o t " a d j a c e n t t o a r e a s w i t h l i t t l e o r no e x p o s u r e . Thus, the e x t r a p o l a t i o n step i n standard exposure c a l c u l a t i o n s may underestimate exposure i f the p a t c h does not r e p r e s e n t a high exposure spot, but would o v e r e s t i m a t e exposure i f such a spot h i t the patch. Since the p a t t e r n s of exposure a r e h i g h l y v a r i a b l e and h a v e n o t been w e l l characterized, t h e r e d o e s n o t a p p e a r t o be any means o f d e t e r mining a priori where t o p l a c e a p a t c h t o s e r v e as a r e p r e s e n t a t i v e sample o f a body r e g i o n . As methods of exposure estimation, neither the f l u o r e s c e n t t r a c e r t e c h n i q u e nor the p a t c h t e c h n i q u e have been v a l i d a t e d . N e v e r t h e l e s s , i t w o u l d be e n c o u r a g i n g i f a comparison of e s t i m a t e s b y t h e two methods yielded roughly equivalent results. The o n l y b o d y r e g i o n which can be r e a s o n a b l y compared i s the head, as the patch m e t h o d a s s u m e s no c l o t h i n g p e n e t r a t i o n , a n d no h a n d w a s h was conducted i n t h i s study. Furthermore, four of the s i x w o r k e r s m u s t be e x c l u d e d , as t h e y wore f a c e s h i e l d s . Thus, t h e o n l y c o m p a r i s o n a v a i l a b l e i s t h e head and neck e x p o s u r e o f w o r k e r s #1 a n d #2. These data are presented i n Table IX. F o l l o w i n g t h e p r o t o c o l o u t l i n e d by Durham and Wolfe (£) a n d D a v i s (£) , t h e amount of diazinon recovered from t h e d e r m a l m o n i t o r on t h e c h e s t s o f the two w o r k e r s i s e m p l o y e d t o c a l c u l a t e e x p o s u r e t o t h e f a c e and f r o n t of neck. A s i m i l a r p a t c h on t h e b a c k allows c a l c u l a t i o n of exposure to the back of the neck. Exposure f o r t h e h e a d a n d n e c k o f w o r k e r #1 a p p e a r s to be 1 0 2 6 u g b y t h e t r a c e r m e t h o d . The e s t i m a t i o n of exposure for t h e s e same a r e a s d e r i v e d from the patch t e c h n i q u e i s 10,069 ug, o r 10 t i m e s g r e a t e r . The p a t c h estimate of 9 9 2 6 u g f o r w o r k e r #2 i s q u i t e similar to that of #1, w h i l e here the t r a c e r e s t i m a t e i s a much l o w e r 163 u g . The c u r r e n t l a c k o f any means o f o b t a i n i n g a " t r u e " v a l u e f o r exposure independent of t h e s e methods allows only i n f o r m e d s p e c u l a t i o n as t o w h i c h of these a p p r o a c h e s i s more c o r r e c t .
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
27.
FENSKE ET
AL.
Table
Work No.
1
2
Fluorescent
391
Methodology
IX. Dermal Exposure E s t i m a t i o n P a t c h and T r a c e r T e c h n i q u e s Surface Area s q cm
Body Part
Tracer
Face Back Neck F r o n t Neck
Face Back Neck F r o n t Neck
* Head r e g i o n f o r back of neck.
650 110 150
650 110 150
Patch Exposure u g / s q cm 12.45 0.99 12.45
Calculated Exposure ug/part
by
Tracer Exposure ug/part 996*
8092 109 1868
30
Total
10069
1026
11.94 3.40 11.94
7761 374 1791
146
Total
9926
163
tracer technique
includes
17
sides
and
Although the accuracy of the methods remains in question, one would expect each technique to provide reasonable comparative exposure estimates w i t h i n a study. Based on v i s u a l observations of the t r a c e r there is a clear d i f f e r e n c e between f a c i a l exposure t o t r a c e r for W o r k e r s #1 a n d #2. S u c h a d i f f e r e n c e i s c o r r o b o r a t e d by personal a i r sampling data, where these workers d i f f e r e d by n e a r l y an o r d e r o f m a g n i t u d e . A similar difference is r e f l e c t e d i n the t r a c e r exposure v a l u e s , w h i l e the patch technique m a k e s no d i s t i n c t i o n i n t h e e x p o s u r e o f these two subjects. Such comparisons are a t t h i s stage only s u g g e s t i v e , and w i l l r e q u i r e f u r t h e r i n v e s t i g a t i o n . Directions
for Future
Research
The f l u o r e s c e n t t r a c e r t e c h n i q u e a p p e a r s t o h o l d a p o t e n tial for p r o v i d i n g f a r more d e t a i l e d information concerning the magnitude and distribution of pesticide exposure than e x i s t i n g techniques. This i n i t i a l field trial also i l l u s t r a t e s many o f t h e c o m p l e x i t i e s o f the method. The q u a n t i t a t i v e r e l a t i o n s h i p o f t h e pesticide and tracer as t h e y a r e d e p o s i t e d on t h e skin surface n e e d s t o be d e t e r m i n e d w i t h a h i g h e r d e g r e e o f accuracy. A more careful d e t e r m i n a t i o n of the r a t i o of the two compounds i n an a e r o s o l , and o f t h e c h e m i c a l s ' a b i l i t y t o penetrate v a r i o u s types of f a b r i c i s clearly required. Further comparative studies employing the tracer and patch techniques would c l a r i f y the s t r e n g t h s and weakn e s s e s o f t h e s e two a p p r o a c h e s . Quantification of e x p o s u r e by means o f the VITAE system also requires refinement, p a r t i c u l a r l y i n regard to the c h a r a c t e r i z a t i o n of v a r i a b l e background l e v e l s in pre-exposure images. A s o l u t i o n t o t h i s p r o b l e m may l i e Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
392
D E R M A L
E X P O S U R E
R E L A T E D
T O
P E S T I C I D E
U S E
in an improved l i g h t i n g / d e t e c t o r / f i l t r a t i o n s y s t e m . In a d d i t i o n , t h e problems o f d e t e c t o r s a t u r a t i o n and quenching currently l i m i t the accuracy o f t h e method. In general, such overloading of the s k i n surface with f l u o r escent m a t e r i a l c a n be a v o i d e d by c o n t r o l l i n g t h e amount of tracer introduced into the spraying system. I t appears that r e l a t i v e l y high l e v e l s of t r a c e r are necessary to detect protective clothing penetration, while much l o w e r l e v e l s w o u l d be a d e q u a t e t o m o n i t o r d e p o s i t i o n on exposed skin surfaces. A series of range-finding studies under controlled conditions could lead t o an appropriate r e s o l u t i o n of t h i s problem. Leaving s u c h r e f i n e m e n t s a s i d e f o r a moment, i t i s c l e a r t h a t t h e t r a c e r t e c h n i q u e a s now p r a c t i c e d p r o v i d e s an i n v e s t i g a t o r with a powerful qualitative tool for c h a r a c t e r i z i n g dermal exposure, and f o r d e v e l o p i n g recommendations c o n c e r n i n g p r o t e c t i v e c l o t h i n g use and changes i n work p r a c t i c e s . F u r t h e r , the worker education potent i a l o f t h i s a p p r o a c h c a n n o t be o v e r s t a t e d . The v i s u a l ization of exposure allows workers t o p a r t i c i p a t e i n their own e v a l u a t i o n . I n many i n s t a n c e s t h e y come to recognize f o r the f i r s t time the nature of the hazard which they face i n t h e i r day t o day work, a n d we have seen marked changes i n behavior l i t e r a l l y o v e r n i g h t . As a s i m p l e a n d i n e x p e n s i v e means o f e v a l u a t i o n , i t i s h o p e d that t h i s a p p r o a c h w i l l be adopted i n t h e agricultural workplace despite the refinements required f o r q u a n t i t a tive analysis. Nontechnical
Summary
The u s e o f f l u o r e s c e n t compounds as t r a c e r s of dermal exposure among p e s t i c i d e a p p l i c a t o r s has been tested under normal working c o n d i t i o n s . Six applicators introduced a Fluorescent Whitening Agent i n t o their spray tanks with the organophosphate p e s t i c i d e , d i a z i n o n . They were e x a m i n e d u n d e r l o n g wave u l t r a - v i o l e t l i g h t (black light) after spraying to v i s u a l i z e the pattern of expos u r e on t h e s k i n s u r f a c e . The f l u o r e s c e n c e was quantified b y means of the Video Imaging Technique f o r A s s e s s i n g Exposure, o r VITAE system. This system employs a television camera as a d e t e c t o r , and d i g i t i z e s the v i d e o s i g n a l b y means o f a microcomputer. Quantifiable levels o f t r a c e r were d e t e c t e d beneath t h e c o t t o n c o v e r a l l s of f i v e workers. The d i s t r i b u t i o n o f e x p o s u r e o v e r the body s u r f a c e v a r i e d w i d e l y due to differences i n p r o t e c t i v e c l o t h i n g u s e , work p r a c t i c e s and e n v i r o n m e n t a l conditions. Quantification of exposure with this technique i s subject to further refinements. Qualitative assessment has proven very s u c c e s s f u l i n regard t o worker education and t h e e v a l u a t i o n o f p r o t e c t i v e c l o t h i n g performance.
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
27.
FENSKE ET AL.
Fluorescent
Tracer
Methodology
393
Acknowledgments This work was i n i t i a l l y f u n d e d by t h e C a l i f o r n i a State Department o f I n d u s t r i a l R e l a t i o n s (Contract N o . 4-6141), and was s u b s e q u e n t l y s u p p o r t e d by t h e N a t i o n a l I n s t i t u t e for O c c u p a t i o n a l S a f e t y a n d H e a l t h ( G r a n t N o . 1 R 0 1 OH 01234-01A1) and the E n v i r o n m e n t a l P r o t e c t i o n Agency ( C o o p e r a t i v e Agreement C R - 8 1 0 6 9 1 - 0 1 - 0 ) . The work c o u l d n o t have been completed w i t h o u t the e x c e l l e n t t e c h n i c a l sup p o r t p r o v i d e d b y S h a r o n Wong a n d W i l l i a m G i b b .
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RECEIVED September 24,
1984
Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.