Workers in the Agricultural Environment - American Chemical Society

8 Workers in the Agricultural Environment Dermal Exposure to Carbaryl

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Downloaded by UNIV OF AUCKLAND on December 26, 2017 | http://pubs.acs.org Publication Date: February 26, 1982 | doi: 10.1021/bk-1982-0182.ch008

JAY C. MAITLEN, C. RONALD SELL, and LESLIE M. McDONOUGH USDA, Yakima Agricultural Research Laboratory, Agricultural Research, Science and Education Administration, Yakima, WA 98902 STANFORD N. FERTIG USDA, Pesticides Impact Assessment Staff, Agricultural Research, Science and Education Administration, Beltsville, MD 20705 Abstract The hourly dermal exposure (HDE) of agricultural workers to carbaryl applied by air or ground equipment was highest for the aerial flagger (rarely used nowdays), next highest for the mixer-loader, followed by the applicator and the bystander. The exposure of the later three types of workers was limited mainly to the hands. The hand exposure of the mixer-loader was much greater when gloves were not worn; the hand exposure of the applicator occurred because it was necessary to adjust spray nozzles during the spray operation. The bystander received the hand exposure because of hand contact with the sprayed crop foliage. When an aerial flagger was used, the HDE values for the face were higher than for other parts of the body and were about half the total body HDE. The HDE on hands of thinners working in an apple orchard treated with carbaryl correlated with total extractable residues from apple leaves (r=0.99). The loss of residues of carbaryl on apple leaves was found to occur by 2 first-order processes: 87% of the residue was lost with a half-life of 8 days, and the rest with a half-life of 45 days.

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This paper reports the results of research only. Mention of a pesticide in this paper does not constitute a recommendation for use by the U.S. Department of Agriculture, nor does it imply registration under FIFRA as amended. Also, mention of a commercial product in this paper does not constitute a recommendation for use by the U. S. Department of Agriculture. This chapter not subject to U.S. copyright. Published 1982 American Chemical Society

Plimmer; Pesticide Residues and Exposure ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

PESTICIDE RESIDUES AND EXPOSURE


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Once DDT had proved effective as a means of controlling insect pests of several agriculture crops (1), organic insecticides became the major method of control. This stimulated extensive research on the synthesis of other potential organic pesticides to control economic pests on food and forage crops. Subsequently, research was directed toward the evaluation of residues of these pesticides in our food supply and their effects on man and animals. The knowledge gained from these studies made it possible to use pesticides effectively and in ways that were not harmful to consumers of the produce. However, in recent years it became apparent that there is insufficient information concerning the hazards to workers involved in the production of pesticides and to workers in the agricultural environment. Comer et al. (2) therefore evaluated the effect of exposure to carbaryl (1-naphthyl methylcarbamate) on formulating plant workers and on workers applying carbaryl to fruit orchards with a tractor-drawn air-blast sprayer. However, information was s t i l l needed on the persistence of carbaryl in apple orchards and on the resultant exposure of workers who re-enter treated orchards. Further, no studies had been done on other types of crops. The present study was undertaken to determine the exposure of agricultural workers to carbaryl as a function of type of formulation, application equipment, application method, and type of work performed (i.e., mixer-loader, applicator, flagman, bystander, and apple thinners). Methods and Materials Table 1 shows the number and types of workers and the various situations in which these workers were monitored for dermal exposure to carbaryl. Formulations of carbaryl that were evaluated included 80S, a wettable powder containing 80% active carbaryl; 50W, a wettable powder containing 50% active carbaryl; Sevimol® 4, a liquid suspension of carbaryl in molasses containing 40% active ingredient; and XLR, a water based flowable containing 4 lbs active carbaryl per gallon. Workers associated with the application of carbaryl (applicator, mixer-loader, bystander and aerial flagger) and re-entry workers (apple thinners) were monitored by a modification of the procedure of Durham and Wolfe (3). The workers were fitted with a disposable jacket (Safety and Supply Co., Seattle, WA) to which 10 χ 10 cm pads were attached with masking tape. One pad was attached as close to the neck as possible on each shoulder and on the chest and the back of each subject. One pad was also placed on each forearm midway between the elbow and wrist. The pads were constructed by backing an 8 ply gauze compress with two pieces of heavy filter paper and attaching these together in the center with a staple.


8.

MAITLEN ET A L .

Dermal Exposure

to

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85

Table I.--Operations i n which workers were monitored f o r dermal exposure t o c a r b a r y l .


Exp. Formulation Rate of no. a p p l i e d application

1. 2. 3.

4. 5. 6. 7.

8. 9.

80S 80S Sevimol-4

Ground a p p l i c a t i o n s 3 l b ΑΙ/acre 3 l b AI/acre 3 l b AI/acre

No. o f . Crop reps.treated

Workers ~j monitored-

7

c/ Aerial applicationsXLR 2 l b AI/acre XLR 1 l b AI/acre Sevimol-4 2 l b AI/acre 80S 2 l b AI/acre c/ Handgun a p p l i c a t i o n s 50W 4 l b AI/acre 50W 2 l b AI/acre

1 10 10

peas potatoes potatoes

Μ,Α,Β Μ,Α,Β Μ,Α,Β

1 1 4 7

corn corn corn corn

M,A,F M,A,F M,A,F M,A,F

1 1

apples apples

Μ,Α,Τ Μ,Α,Τ

à/

-

The mixing, l o a d i n g , and a p p l i c a t i o n o f one batch o f p e s t i c i d e was considered a r e p l i c a t i o n . The workers monitored were the mixer-loader (M); a p p l i c a t o r (A); a e r i a l f l a g g e r ( F ) , bystander (B) i . e . a f i e l d worker near ( w i t h i n 100 f e e t ) the t r a c t o r during a p p l i c a t i o n s ; and re-entry thinners (T).

c/ - The ground a p p l i c a t i o n was made w i t h a t r a c t o r equipped w i t h a r e a r mounted boom sprayer. The a e r i a l a p p l i c a t i o n s were made w i t h a h e l i c o p t e r equipped w i t h a boom. The hand-gun a p p l i c a t i o n s were made w i t h a commercial h i g h pressure hose-nozzle sprayer.



86

Then each pad was pre-extracted w i t h dichloromethane (DCM), d r i e d , and fastened along two edges t o a water r e p e l l e n t , 10 χ 13 cm piece of cardboard w i t h masking tape. The back of the cardboard was then marked w i t h a 6.5 cm square t o expedite trimming the pad a f t e r i t had been exposed. A f t e r an exposure, the pads were removed from the j a c k e t and trimmed to the premarked s i z e (42.25 cm ). Then the cardboard backing was d i s c a r d e d , and the small square remaining was folded and placed i n a small wide-mouth b o t t l e c o n t a i n i n g 50 ml of DCM. The b o t t l e was sealed w i t h a Teflon®-lined cap and stored i n a r e f r i g e r a t o r u n t i l we were ready to proceed w i t h e x t r a c t i o n of the residues. A b o t t l e s i z e was chosen so that the f o l d e d pad would be completely covered w i t h DCM. In a d d i t i o n , hand r i n s e samples were taken from each subject by p l a c i n g each hand i n a p l a s t i c bag, adding 150 ml of 95% e t h y l a l c o h o l , securing the bag t i g h t l y around the w r i s t , and shaking v i g o r o u s l y f o r 1 min. When the hands were removed, the bag was sealed and placed i n a wide-mouth h a l f - p i n t j a r f o r t r a n s p o r t i n g to the l a b o r a t o r y . I n the l a b o r a t o r y , the bags were opened and the a l c o h o l s o l u t i o n was decanted i n t o 200 ml b o t t l e s and stored i n a r e f r i g e r a t o r u n t i l p a r t i t i o n e x t r a c t i o n . For the study of the degradation of c a r b a r y l , 25 leaves were picked from each of the 3 apple trees i n each p l o t as follows: s t a r t i n g near the crown of the t r e e , 8 leaves were p i c k e d randomly down t o the d r i p l i n e and t h i s procedure was repeated a t 2 other p o s i t i o n s approximately 1/3 of the way around the t r e e . At the 3rd p o s i t i o n , 9 leaves were p i c k e d . The leaves from each t r e e were then composited i n t o one sample, so there were 3 r e p l i c a t e samples from each p l o t , and taken to the l a b o r a t o r y where they were immediately prepared f o r the e x t r a c t i o n . Leaf samples were taken a t i n t e r v a l s of 0, 1, 3, 7, 17, 24, 31, 38, and 52 days a f t e r the trees were sprayed w i t h a carbaryl.


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E x t r a c t i o n and Cleanup Procedures. Before the pads were e x t r a c t e d , the b o t t l e s c o n t a i n i n g the exposed pads i n DCM were removed from the r e f r i g e r a t o r and allowed t o warm t o room temperature. Then they were shaken f o r 1 min and the contents decanted i n t o a 125 ml Erlenmyer f l a s k . The pad was e x t r a c t e d 2 more times by shaking f o r 1 min w i t h f r e s h 25 ml p o r t i o n s of DCM and the combined e x t r a c t s r e f r i g e r a t e d u n t i l a n a l y s i s . F o r q u a n t i t a t i v e e x t r a c t i o n , i t was necessary that the pads be held i n the DCM f o r a t l e a s t one day before e x t r a c t i o n . Likewise, the hand r i n s e samples i n e t h y l a l c o h o l were removed from the r e f r i g e r a t o r and allowed to warm t o room temperature. Then a 100 ml a l i q u o t o f the s o l u t i o n was t r a n s f e r r e d t o a 500 ml separatory f u n n e l , and 200 ml of water and 1.0 ml of concentrated phosphoric a c i d were added. The r e s u l t a n t s o l u t i o n was e x t r a c t e d 4 times w i t h 50 ml each of


8.

MAITLEN ET A L .

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Exposure

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87

Carbaryl

DCM. The DCM e x t r a c t s were d r i e d by f i l t e r i n g through a funnel plugged w i t h a small amount of c o t t o n o v e r l a i d w i t h anhydrous sodium s u l f a t e i n t o a 250 ml Erlenmyer f l a s k . After a l l 4 e x t r a c t i o n s had been f i l t e r e d , the f i l t e r i n g funnel and i t s contents were r i n s e d w i t h two 10 ml p o r t i o n s of DCM, and the r e s u l t a n t s o l u t i o n was placed i n a r e f r i g e r a t o r and h e l d u n t i l analysis. For e x t r a c t i o n of the apple l e a v e s , d i s c s were punched from the 25 leaves w i t h a cork borer to produce 190 cm of l e a f surface area per sample. Residues of c a r b a r y l were then e x t r a c t e d by p l a c i n g the 25 d i s c s i n a 250 ml Erlenmyer f l a s k w i t h 100 ml of DCM and shaking on a w r i s t - a c t i o n shaker f o r 15 min. Next the s o l u t i o n was f i l t e r e d through a g l a s s f i b e r f i l t e r , and an 80 ml a l i q u o t of e x t r a c t was t r a n s f e r r e d t o a 125 ml Erlenmyer f l a s k and evaporated i n a 40-45°C water bath w i t h the a i d of a gentle stream of dry f i l t e r e d a i r . The dry residue i n the f l a s k was cleaned up by a c o a g u l a t i o n procedure t h a t i n v o l v e d adding 4.0 ml of methyl a l c o h o l and 1.0 g of Hyflosuper-Cel® and warming the s l u r r y i n a water bath w i t h intermittent stirring f o r 10 min. A 20 ml p o r t i o n of c o a g u l a t i n g s o l u t i o n (2.0 ml of phosphoric a c i d and 1.5 g of ammonium c h l o r i d e i n 1 l i t e r of water) was added, and the sample was r e f r i g e r a t e d f o r 30 min. Samples were removed from the r e f r i g e r a t o r one a t a time and f i l t e r e d through a Whatman g l a s s f i b e r f i l t e r paper i n t o a 250 ml separatory f u n n e l , and the sample f l a s k was r i n s e d i n t o the f i l t e r i n g funnel w i t h three 10 ml p o r t i o n s of a mixture of 10% methyl a l c o h o l i n water ( v / v ) . This procedure was f o l l o w e d by three 10 ml r i n s e s of the f i l t e r i n g funnel and i t s contents w i t h the methyl alcohol-water mixture. The s o l u t i o n i n the separatory funnel was e x t r a c t e d w i t h one 50 ml p o r t i o n and two 25 ml p o r t i o n s of DCM by shaking f o r 30 sec and then f i l t e r i n g through a funnel plugged w i t h a s m a l l amount of cotton o v e r l a i d w i t h anhydrous sodium s u l f a t e . A f t e r the e x t r a c t s were f i l t e r e d , the f i l t e r i n g funnel and i t s contents were r i n s e d w i t h two 10-ml p o r t i o n s of DCM, and the s o l u t i o n s were stored i n a r e f r i g e r a t o r u n t i l a n a l y s i s . Gas chromatographic determination of c a r b a r y l residues (as the mesylate d e r i v a t i v e ) from exposure pads, hand r i n s e s , and apple l e a f e x t r a c t s showed t h a t some samples r e q u i r e d an a d d i t i o n a l cleanup to remove i n t e r f e r i n g compounds. This was accomplished by evaporating the s o l u t i o n to dryness i n the 40-45°C water bath, adding 15 ml of hexane and 2.0 g of Florisil® (PR grade), and shaking on a w r i s t - a c t i o n shaker f o r 5 min. The s o l u t i o n was decanted through a funnel plugged w i t h c o t t o n and o v e r l a i d w i t h anhydrous sodium s u l f a t e . The f l a s k was i n v e r t e d and suspended over the funnel u n t i l the entrapped m a t e r i a l i n the f l a s k had d r i e d . A sharp tap on the f l a s k d i s l o d g e d the remaining m a t e r i a l i n the f l a s k i n t o the f u n n e l . The sample f l a s k was r i n s e d 3 times w i t h 10 ml each of hexane,


2


88



and the r i n s e s were poured i n t o the f i l t e r i n g f u n n e l . When these s o l u t i o n s had passed through the f i l t e r i n g f u n n e l , the f u n n e l and i t s contents were r i n s e d 3 times w i t h 10 ml each of hexane. The c o l l e c t i o n f l a s k was then changed, and the c a r b a r y l mesylate was e l u t e d from the F l o r i s i l w i t h four 10 ml p o r t i o n s of a mixture of hexane and DCM (1:1). The s o l u t i o n was evaporated to dryness i n the water bath and made up to a volume s u f f i c i e n t f o r gas chromatographic a n a l y s i s . A n a l y t i c a l Procedures. The e x t r a c t s from exposure pads, hand r i n s e s , and apple leaves were evaporated to dryness i n the 40-45°C water b a t h , and the c a r b a r y l r e s i d u e s were determined by the procedure of M a i t l e n and McDonough ( 4 ) . In t h i s procedure, the residues were hydrolyzed w i t h methanolic potassium hydroxide to 1-naphthol which was then converted to the mesylate d e r i v a t i v e by r e a c t i o n w i t h methanesulfonyl c h l o r i d e . The c a r b a r y l mesylate was q u a n t i t a t e d w i t h a Hewlett Packard Model 5840A gas chromatograph (GLC) equipped w i t h a flame photometric d e t e c t o r operated i n the s u l f u r mode. The GLC column was a 122 cm χ 4.0 mm I.D. g l a s s column packed w i t h Chromosorb G (HP) coated w i t h 5% OV 101. The column was operated a t a temperature of 205°C w i t h a n i t r o g e n f l o w rate of 60 ml/min. The t o t a l h o u r l y dermal exposures (HDE) were c a l c u l a t e d from the r e s i d u e s on exposure pads by the equation of Durham and Wolfe (3) as f o l l o w s : 150A T o t a l HDE where : A Β C D Ε t

= = = = = =

+

HOB

+

650(C)

+

1210(D)

(mg/h) =

+

Ε

?

Residues on chest pad (pg/cm ) Residues on back pad (pg/cm ) Sum of residues on shoulder pads (pg/cm ) Sum of r e s i d u e s on forearm pads (pg/cm ) Sum of residues from hand r i n s e s (pg) The number of hours of exposure 2

2

2

2

The constants i n the numerator of the equation approximate s u r f a c e area ( i n cm ) of the f r o n t V of the neck, back of neck, f a c e , forearms and hands, r e s p e c t i v e l y . The e f f i c i e n c y of the e x t r a c t i o n and cleanup procedures was determined by f o r t i f y i n g c o n t r o l samples of exposure pads, hand r i n s e s , and apple leaves w i t h known amounts of pure c a r b a r y l before extraction and determining the percent recovered. Exposure pads f o r t i f i e d w i t h c a r b a r y l over a range of 50 to 400 Mg/pad had an average recovery of 88.6% (range 72 to 119%). Hand r i n s e s prepared w i t h c a r b a r y l over a range of 100 to 400 pg/sample had an average recovery of 90.6% (range 73 the the

2


8.

MAITLEN ET AL.

Dermal Exposure

to

Carbaryl

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to 121%). Apple l e a f samples f o r t i f i e d w i t h c a r b a r y l over a range of 50 t o 200 pg/sample had an average recovery o f 83.7% (range 68.0 t o 104.0%).


R e s u l t s and D i s c u s s i o n Mixer-loaders. The mixer-loader operation was not inherently different f o r ground, aerial, or handgun applications. Several f a c t o r s a f f e c t e d the h o u r l y dermal exposure (HDE) t o these workers (Table I I ) . These i n c l u d e d (1) the f o r m u l a t i o n used, (2) whether or not the worker wore gloves, and (3) the method o f removing the powdered i n s e c t i c i d e from i t s container p r i o r t o mixing. The powdered formulations (80S and 50W) produced higher t o t a l HDE than d i d the l i q u i d formulations (Sevimol-4 and XLR). When gloves were worn, mixer-loaders r e c e i v e d a t o t a l HDE of 43.3 mg/h from powdered and 3.0 mg/h from the l i q u i d formulations (average values of a l l 8 experiments). The higher HDE t o the mixer-loader handling the powdered f o r m u l a t i o n versus the l i q u i d f o r m u l a t i o n and wearing gloves was a r e s u l t of the greater residues on the forearms (31 vs 1 mg). When gloves were not worn, the powdered formulations produced an average t o t a l HDE of 107 mg/h compared t o 40 mg/h f o r l i q u i d f o r m u l a t i o n s . These r e s u l t s not only demonstrated t h a t there was a d i f f e r e n c e i n exposure r a t e s due t o f o r m u l a t i o n s , but t h a t exposures were g r e a t l y reduced by wearing gloves. An average of 76% of the t o t a l HDE t o a l l mixer-loaders was found on the hands, suggesting t h a t gloves are the most important item of p r o t e c t i v e c l o t h i n g . Experiments 2 and 3 were designed t o determine the value of wearing gloves. Workers wearing gloves r e c e i v e d t o t a l HDE's of 43.3 and 3.41 mg/h from 80S and Sevimol-4, r e s p e c t i v e l y ; when gloves were not worn the t o t a l HDEs were 247 and 40 mg/h, r e s p e c t i v e l y . The techniques the mixer-loader used t o handle powdered formulations a l s o a f f e c t e d the exposure l e v e l . In experiments 2 and 9 the worker (without gloves) scooped the f o r m u l a t i o n from the c o n t a i n e r , whereas i n experiments 1, 7 and 8 the worker (without gloves) poured the f o r m u l a t i o n from the c o n t a i n e r . These precedures produced average t o t a l HDE's of 176 and 38 mg/h, r e s p e c t i v e l y . Applicators. The workers involved i n the ground a p p l i c a t i o n s of c a r b a r y l r e c e i v e d c o n s i d e r a b l y l e s s exposure than the mixer-loaders. Most of the exposure was t o the hands and was a t t r i b u t e d t o a d j u s t i n g the nozzles on the spray equipment. Thus, f o r the ground a p p l i c a t i o n of the 80S f o r m u l a t i o n , the t o t a l HDE was 1.6 mg/h and the HDE t o the hands was 1.5 mg/h. F o r a s i m i l a r a p p l i c a t i o n of Sevimol-4, the t o t a l HDE was 2.8 mg/h and the HDE t o the hands was 2.7


90


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Workers in the Agricultural Environment - American Chemical Society

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