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The Potential for Applicator-Worker Exposure to Pesticides in Greenhouse Operations ACIE C. WALDRON North Central Region Pesticide Impact Assessment Program, Department of Entomology, Ohio State University, Columbus, OH 43210 Airborne and surface foliar measurements of pesticide residues following high and low volume spray and fog applications to greenhouses showed that the potential hazard to workers is initially much greater than from similar outdoor operations. Airborne residues dissipated within a 2-4 hour period when the greenhouse was vented and/or there was considerable air movement, but were evident for several hours in unvented greenhouses. Climatic-atmospheric conditions directly affected the persistence of pesticide residues. Although airborne residue dissipation from high volume application was faster than that from low volume, the former may involve the greatest hazard because such applications are made during the daytime when workers may be present in other locations in the greenhouse in contrast to low volume applications made at night in closed greenhouses after workers have vacated the premises. Surface foliar pesticide residues are also of concern to the greenhouse worker. Vegetable and flower crop production i n greenhouses are beset with unique situations and problems i n pest c o n t r o l . The confined, enclosed area makes any registered pesticide applied as a fumigant, or that may v o l a t i l i z e after surface a p p l i c a t i o n , p o t e n t i a l l y very effective against pests. On the other hand, the health hazard associated with airborne pesticides i s considerably greater indoors than similar operations outdoors. Pesticide l e v e l s in the ambient out-ofdoor a i r are usually in the nanograms-per-cubic meter range, but indoor l e v e l s may be i n the microgram to milligram-per-cubic meter range and may persist for a longer period of time. Many greenhouse operations are labor-intensive and require frequent worker exposure to the greenhouse atmosphere and the treated plant f o l i a g e . Pesticides may be applied to greenhouse crops throughout the year, generally on a 3-day schedule. High volume (HV) applications are usually made with other workers present i n adjacent areas of the greenhouse. Low volume (LV) applications are usually i n

0097-6156/85/0273-0311$06.00/0 © 1985 A m e r i c a n C h e m i c a l Society

Honeycutt et al.; Dermal Exposure Related to Pesticide Use ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

DERMAL EXPOSURE RELATED TO PESTICIDE USE

312

the evening or early night when only the applicator i s present. Factors which affect worker exposure to pesticides include the type of a c t i v i t y , pesticide p a r t i c l e s i z e , formulation, climatic condit i o n s , duration of exposure and attitude of the worker i n r e l a t i o n to avoiding conditions conducive to exposure. Protective clothing of some kind plus respirators or gas masks are usually worn by the applicator during treatment, but the degree of protection offered may be l i m i t e d , depending on the type of equipment used to apply the pesticide. Thus, pesticide use i n greenhouses may present a p a r t i cular problem for applicator and worker exposure to pesticide r e s i dues, both i n the a i r and on treated f o l i a g e . Research on pesticide exposure experienced by applicators and workers i n greenhouses i s very l i m i t e d , and consequently, was noted as a data gap i n the Rebuttable Presumption Against Registration (RPAR) process of reviewing pesticide registrations early i n the Pesticide Impact Assessment Program (PIAP). Multiyear studies on pesticide/greenhouse relationships for the North Central Region Pesticide Impact Assessment Program (NCRPIAP) were i n i t i a t e d by Drs. Richard K. Lindquist, Harvey R. Krueger and Charles C. Powell, J r . at the Ohio A g r i c u l t u r a l Research and Development Center (OARDC) i n 1979 (1) and by Dr. Delbert D. Hemphill at the University of Missouri in 1980 (2). The major objectives of the research were (a) to develop procedures for sampling and measuring pesticide residues i n the greenhouse atmosphere; (b) to measure airborne and surface r e s i due of selected pesticides in greenhouses at intervals after a p p l i cation to determine the exposure potential to applicators and workers; (c) to determine the effects of time, temperature, l i g h t i n t e n s i t y , and a i r movement on the atmospheric concentration of pesticides; and (d) to develop procedures to reduce human hazards associated with greenhouse pesticide applications. This paper cons t i t u t e s a b r i e f summarization of public information data currently held i n PIAP f i l e s . Procedures I n i t i a l efforts i n greenhouse-pesticide-exposure research were to develop procedures for measuring the v o l a t i l i t y and hence airborne concentration of pesticides i n the greenhouse atmosphere over a period of time. This was followed by analysis for surface residues on foliage and s t r u c t u r a l surfaces and f i n a l l y determining the degree of protection provided to the applicator and worker through the wearing of appropriate protective clothing and devices. Studies were conducted i n both commercially and university operated greenhouses u t i l i z i n g both the grower and technical personnel as applicators. HV applications were made using standard power spraying equipment (1) and the knapsack sprayer (2). LV applications were made with thermal pulse j e t foggers, mechanical aerosol generators and spinning disc (controlled droplet) equipment as related to the a v a i l a b i l i t y and the type of formulation (1). The p a r t i c u l a r s on the various application procedures for pesticide fogs, f o l i a r sprays and granules are i n c l u d ed i n the research publications and reports by the p r i n c i p a l i n v e s t i gators (1,2). Greenhouse crops i n the studies conducted by Lindquist included tomatoes, chrysanthemums and roses while Hemphill used leaf lettuce. Such crops are quite labor intensive requiring workers to spend considerable time i n the greenhouse and, consequently, provide


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Pesticide

WALDRON

Exposure

in Greenhouse

Operations

313

a maximum potential for exposure to airborne and surface pesticide residues. Hemphill applied wettable powder formulations of carbaryl, captan and f o l p e t , whereas Lindquist evaluated various formulations of aldicarb, dichlorvos, benomyl, c h l o r o t h a l o n i l , permethrin, methomyl, oxamyl and triadimeform at some time during the study. Greenhouse a i r was sampled by drawing the a i r through sequential samplers calibrated to measure a i r volume f i l t e r e d per unit of time; i . e . 1.8 cubic meters per hour for Hemphill's research and 4 cubic feet per hour f o r L i n d q u i s t s . The a i r was drawn through 0.5 inch diameter c o l l e c t i o n tubes containing 20 cubic centimeters of p u r i f i e d amberlite and glass wool plugs (Lindquist). Hemphill used samplers containing activated charcoal with glass f i b e r f i l t e r s and glass f i b e r f i l t e r s with polyurethane foam plugs. Samplers were capable of providing hourly samples over the 24 hour period although the length of time for c o l l e c t i o n and the i n t e r v a l between sampling was altered according to the individual design of the p a r t i c u l a r study. The greenhouse environment, which included the variables of temperature, r e l a t i v e humidity, l i g h t i n t e n s i t y , a i r movement and v e n t i l a t i o n , was recorded for the sampling i n t e r v a l s . After the c o l l e c t i o n of samples the residues were extracted with acetone or hexane-acetone and analyzed by gas chromatography using suitable detection systems. In calculating respiratory exposure Hemphill used the formula: „ A i r concentration χ 1.8 M /hr Exposure = ^r-: — χ 100% 70 kg in which the a i r concentration i s the residue determined i n the c o l l e c t i o n column per unit of time, 1.8 M /hr i s the average v e n t i l a t i o n rate, 70 kg i s the weight of an average man and the absorption factor i s assumed to be 100%. Lindquist calculated inhalation expo sure potential by determining the pesticide residue collected i n the column per hour and multiplying by a factor of 7.5 which i s the r a t i o of the average human a i r intake of 30 cubic feet per hour to the a i r flow through the samplers of 4 cubic feet per hour. Surface pesticide residues were determined by Lindquist, et a l , by the strategic placement of glass plates throughout the greenhouse and the subsequent measurement of residue collected thereon follow ing the pesticide application. Residue measurements from glass plates were preferred over analysis of foliage because of the ease i n conducting several experiments over a period of time i n replacing the plates rather than waiting for the pesticide to completely dissipate from the treated f o l i a g e . Also measurement of residue from the upper and under surfaces of the glass plate provide a means of determining the plant coverage from d i f f e r e n t application methods. Glass s l i d e s coated with magnesium oxide provided a means of determining pesticide droplet deposition from LV application, but was not p r a c t i c a l for use with HV because the spray washed the coating from the s l i d e s . The measurement of dermal exposure to applicators and greenhouse workers was conducted by attaching gauze pads to the inside and out side surfaces of the clothing, extracting the pesticide residue from the pads and determining concentrations by gas chromatography. Green house workers were not required to wear special clothing - only that normally worn for the work involved. Results and Discussion f

F

3

Sequential sampling systems, with the absorbent materials indicated,



314

were e f f e c t i v e i n c o l l e c t i n g airborne pesticide residues from greenhouse atmospheres. However, as one would expect, the environmental conditions, the nature of the greenhouse, pesticide formulation, and methods of application are determinant factors i n the p o t e n t i a l for applicator/worker exposure. Airborne pesticide residues are the highest immediately a f t e r spraying, as expected, but dissipate rapidly with time. The rate of d i s s i p a t i o n i s enhanced greatly when the greenhouse i s vented to the outside atmosphere or there i s considerable a i r movement due to the design of the greenhouse. Lindquist found residues of dichlorvos applied as a thermal fog decreased from exposure concentrations of 200-400 ug/hr during the f i r s t one or two hour sampling period to approximately the 1-3 ug/hr range at 10 hours and then remained r e l a t i v e l y the same over the next 12 hours (Figure 1). Permethrin applied as a thermal fog showed the i n i t i a l sharp decline i n residue l e v e l during the 1 and 2 hour sampling periods and the rapid drop a f t e r opening the vents. Applications of permet h r i n made i n the evening to a closed greenhouse resulted i n f a i r l y persistent airborne residue l e v e l s a f t e r the f i r s t 2 hour i n t e r v a l and u n t i l the vents were opened i n the morning 8-10 hours after application. HV applications of permethrin dissipated much faster than LV applications, and for LV application the d i s s i p a t i o n rate for the pulse j e t applicator was several magnitudes slower than the mechanical aerosol generator. Typical d i s s i p a t i o n curves for dichlorvos and permethrin are shown i n Figure 1. The curves represent the means of residue measurement of from 3-5 d i f f e r e n t a p p l i cations of the p a r t i c u l a r p e s t i c i d e . Indications are that a p p l i cators and workers would be subject to s i g n i f i c a n t concentrations of airborne residues of these i n s e c t i c i d e s during the i n i t i a l hours after application u n t i l the greenhouse was e f f e c t i v e l y vented. Aldicarb granules applied to greenhouse chrysanthemums did not produce any airborne residue concentrations. Likewise, triadimeform applied by v o l a t i l i z a t i o n and low volume spray applications resulted in e s s e n t i a l l y non-detectable residues. The application of oxamyl resulted i n considerable fluctuation i n the amounts detected, but the airborne concentrations were very low throughout the sampling period. Consequently, further investigations with these pesticides were d i s continued. The results of Hemphill's research with carbaryl showed a r e l a t i v e l y rapid decline with a drop to non-quantitatively detectable levels 4 hours after application (Table I ) . The decline i n residue l e v e l s for captan and folpet was not s i g n i f i c a n t during the f i r s t 2 hour i n t e r v a l but reached non measurable l e v e l s 4 hours a f t e r a p p l i cation. Carbaryl and captan concentrations i n a i r were lower than the Threshold Limit Value (TLV) of 5 mg/M established by the American Conference of Governmental Industrial Hygienists i n 1974. There i s not an established TLV l e v e l f o r f o l p e t . The estimated r e s p i r a tory exposure for the three pesticides, based upon the assumption of 100 percent absorption, i s shown i n Table II for the 0 and 2 hour sampling periods. Comparison of the data with the no observable e f f e c t l e v e l (NOEL) f o r carbaryl of 0.06 mg/kg body weight and captan and folpet at 0.01 mg/kg established by the International Agency of Research on Cancer (IARC) committee of the World Health Organization (WHO) i n 1979, indicates that unprotected inhalation exposure, a l though very low based upon the l-Dr^ exceeded the NOEL for the f i r s t !t

n

3

two

hours

after spraying.


WALDRON

Pesticide

Exposure

in Greenhouse

Operations

315

HOURS AFTER APPLICATION F i g u r e 1 . R e s i d u e s of t y p i c a l p e s t i c i d e s i n greenhouse a i r . (Means of 3 - 5 a p p l i c a t i o n s and samplings f o r each c h e m i c a l . ) Key: , dichlorvos (fog); , permethrin (fog—greenhouse c l o s e d o v e r n i g h t ) ; +-+-+, p e r m e t h r i n ( f o g — g r e e n h o u s e c l o s e d 1 ^ - 2 h o u r s ) ; and Δ — Δ — , methomyl ( s p r a y ) .



316

Table I.

Mean Concentration of Pesticide Chemicals i n a Greenhouse Atmosphere

Pesticide

Concentrât ion at Time Interval

Condition at Time Interval Temp (°C) 0 2 13.5 13.1 19.4 19.9 18.6 17.7

3

(Cone. ug/M ) 0 2 Hours = Carbaryl 53.0 38.3 Captan 18.7 13.3 Folpet 15.7 13.3 a b

24 b b b

4 b b b

Rel Hum (%) 0 2 58.0 58.8 49.5 52.6 71.5 69.3

Mean value for s i x experiments. Trace concentrations either too low to quantify based on minimum detectable l e v e l of 5 ug/M or non measurable. 3

Table I I .

Mean Estimated Respiratory Exposure for Three Pesticides

Pesticide

Estimated Exposure at Time Interval' 0 hrs 2 hrs 1

(mg/kg-hr" ) Carbaryl Captan Folpet a

1.36 4.81 4.04

χ 10~* χ 10, χ 10

9.82 3.4 3.4

χ 10~2 χ 10~, χ 10

Based on the assumption of 100% respiratory exposure over a 60 minute period.

The e f f e c t s of sunlight on the concentration of airborne car b a r y l , captan and folpet residues i n the greenhouse atmosphere i s shown i n Table I I I . The figures given are the mean of 3 r e p l i c a t e determinations by Hemphill. There were s i g n i f i c a n t differences i n residue concentrations between sunny and cloudy days for carbaryl and captan, but not for f o l p e t , with sunlight e f f e c t i n g a lower residue concentration. The e f f e c t s of temperature and r e l a t i v e humi d i t y on airborne concentrations were not r e a d i l y interprétable i n either Hemphill's or Lindquist's studies. However the effects of a i r movement were e a s i l y observable i n that methomyl residues were not detectable at the 12 hour i n t e r v a l i n a p l a s t i c bubble greenhouse with a i r movement of 150 ft/min i n contrast to measurable residues (Figure 1) that appeared to s l i g h t l y increase over a 12 to 48 hour time i n t e r v a l i n a glasshouse with a i r movement at 33 ft/min. (1). Surface residues from HV p e s t i c i d e applications measured at 20 designated locations i n the greenhouse were generally more uniformly distributed throughout the greenhouse than were those of LV a p p l i cation (Figure 2). This may have been p a r t i a l l y due to the procedures whereby HV applications were made by spraying while r e t r e a t ing out of the greenhouse and LV applications were made at night from


22.

WALDRON

Table I I I .

Pesticide

Exposure

in Greenhouse

Operations

317

The Effect of Sunlight on Airborne Residues of Pesticides in

the

Greenhouse

J

Pesticide

Mean Concentration of Residues (ug/M ) Bright Cloudy 0 hrs 2 hrs 0 hrs 2 hrs

Carbaryl Captan Folpet

32.39 11.78 11.12

a b c

7 3

20.61 8.83 6.87

6 1

- h 25.52 19.63°

5 5

d

9 5

' h 17.67 19.63°

The means of three measurements. Significant differences at the 5% l e v e l from measurements under sunny conditions. No s i g n i f i c a n t differences from measurements under sunny condit ions.

a single point at the end of the greenhouse. Although permethrin applications were made at the same rate,surface residues varied according to application method. LV application with a microgen applicator on three d i f f e r e n t dates resulted i n the highest average deposition but also the greatest v a r i a t i o n i n range, whereas the HV application averaged about 1/2 that of the microgen but was approximately 9-10 fold greater than the residue from the LV application with a puisfog. The average residue deposition with the^microgen for each of three applications was 95, 237 and 327 ng/cm , but with extremes of 17-288, 44-417 and 35-812 ng/cm , respectively; for the HV application 177, 167, 151 ng/cm with extremes of 148-258, 92-245 and 43-341 ng/cm , respectively; and for the pulsfog 17.5, 28.8 and 20.4 ng/cm with extremes of 4-97, 6-64 and 8-81 ng/cm , respectively. In most cases the majority of the residue values for the HV and the pulsfog applications were clustered f a i r l y close to the average. However, because comparative applications were not made on the same day nor under the same temperature and r e l a t i v e humidity, a v a l i d comparison and evaluation of the data i s impractical at present other than the indication of potential exposure to workers from surface residues following pesticide application. Pesticide formulation and v o l a t i l i t y of the chemical greatly affects the r a t i o of airborne to surface residues. Wettable powder formulation of permethrin resulted i n an airborne concentration of 0.39 ug/1 during the f i r s t 2 hours after application, whereas the emulsifiable concentrate of the same pesticide resulted i n a concent r a t i o n of 2.82 ug/1. The surface deposition of benomyl averaged approximately 750 ng/cm from a HV application and 632 from an LV application (Figure 2) and airborne residues were not measurable 1 hour a f t e r application. Approximately 33 percent of the benomyl deposition from the HV application was on the under surface of the glass plate, whereas only 1 percent from the LV application was so deposited. Data r e l a t i v e to the effect of greenhouse structure on airborne and surface pesticide residues and the reduction of the exposure potential due to the use of protective clothing and equipment and 2

2

2

2

2

2



206 9 220 830 860

184 16 133 650 840

149 20 101 900 860

196 17 160 450 230

156 18 204 1160 930

257 25 205 510 1030

183 21 392 850 1200

164 15 285 480 770

15 294^ 830 360

186 66 319 510 450

135 17 311 520 900

166 15 328 840 610

161 30 220 790 240

102* 39 309^ 640 240

149 19 58 960 540

173 14 273 920 700

131 30 91 830 560

120 20 119 850 420

206* 23 b

860 370

d

e

140" 13 297^ 690 530 b

d

e

ί

b

d

e

b

d

e

^ a b c d e

Greenhouse width = 22.5 fëet = = = = «

^·

Average of HV a p p l i c a t i o n of permethrin from 3 dates. Average of LV pulsfog a p p l i c a t i o n of permethrin from 3 dates. Average of LV microgen a p p l i c a t i o n of permethrin from 3 dates. HV a p p l i c a t i o n of benomyl. LV pulsfog a p p l i c a t i o n of benomyl.

a,b,c,d,e notes apply to a l l numbers h o r i z o n t a l l y across the f i g u r e .

2 F i g u r e 2. P e s t i c i d e s u r f a c e r e s i d u e s (ng/cm ) measured a t 20 d e s i g n a t e d l o c a t i o n s i n t h e greenhouse a f t e r HV and LV a p p l i c a t i o n s o f p e r m e t h r i n o r benomyl.


22.

WALDRON

Pesticide

Exposure

personal safety practices been r e p o r t e d .

in Greenhouse

exercised

Operations

by greenhouse

workers has not

319

yet

Summary S t u d i e s conducted under t h e s p o n s o r s h i p o f t h e NCRPIAP i n Ohio and M i s s o u r i have p r o v i d e d s a t i s f a c t o r y methods f o r d e t e r m i n i n g a i r b o r n e and s u r f a c e p e s t i c i d e r e s i d u e s from greenhouse a p p l i c a t i o n s and have i n d i c a t e d t h e p o t e n t i a l exposure t o a p p l i c a t o r s and w o r k e r s . A l t h o u g h a i r b o r n e r e s i d u e s q u i c k l y d i s s i p a t e when the v e n t s a r e opened a t time i n t e r v a l s a f t e r the s p r a y i n g o p e r a t i o n , t h e i n i t i a l exposure t o t h e a p p l i c a t o r and t o any worker who e n t e r s the greenhouse soon a f t e r a p p l i c a t i o n i s e v i d e n t and r e q u i r e s p r o p e r a t t e n t i o n t o p e r s o n a l protection. P e s t i c i d e s a r e a p p l i e d as h i g h volume (HV) and low volume (LV) s p r a y s and fogs to greenhouse c r o p s t h r o u g h o u t t h e y e a r o f t e n on a 3-day s c h e d u l e . HV a p p l i c a t i o n s a r e u s u a l l y made w i t h o t h e r workers p r e s e n t i n a d j a c e n t a r e a s o f the g r e e n h o u s e , whereas LV a p p l i c a t i o n s a r e made d u r i n g the e v e n i n g when o n l y t h e a p p l i c a t o r is present. P r o t e c t i v e c l o t h i n g o f some k i n d , p l u s r e s p i r a t o r s o r gas masks, a r e u s u a l l y worn by the a p p l i c a t o r s d u r i n g t r e a t m e n t s , but t h e degree o f p r o t e c t i o n o f f e r e d may be l i m i t e d and depends upon the t y p e o f equipment used to a p p l y t h e p e s t i c i d e . T h e r e i s p o t e n t i a l f o r exposure from a l l a p p l i c a t i o n methods, but the a c t u a l amount o f exposure may v a r y t r e m e n d o u s l y . Low volume a p p l i c a t i o n s g e n e r a l l y r e s u l t i n h i g h e r r e s i d u e s t h a n h i g h volume. It c o u l d thus be c o n c l u d e d t h a t LV a p p l i c a t i o n s w i l l r e s u l t i n g r e a t e r worker exposure to the p e s t i c i d e . However, the o p p o s i t e may be t r u e and LV a p p l i c a t i o n s c o u l d be l e s s h a z a r d o u s b e c a u s e they a r e g e n e r a l l y made i n the e v e n i n g , r e q u i r e a r e l a t i v e l y s h o r t p e r i o d o f time w i t h no workers p r e s e n t , the a p p l i c a t o r moves away from the p e s t i c i d e a p p l i c a t i o n and out o f the a r e a and t h e greenhouse i s u s u a l l y v e n t e d i n the morning b e f o r e anyone e n t e r s . The a d d i t i o n a l d a t a t o s e p a r a t e a c t u a l worker exposure from p o t e n t i a l exposure s h o u l d be a v a l u a b l e c o n t r i b u t i o n t o the s t u d y .

Literature Cited 1.

2.

Lindquist, R.K., H.R. Krueger and C.C. Powell, Jr. "Measurement of Pesticide Concentrations in Air Inside Greenhouses" NCRPIAP Project #67 (30-NC-OH-O) FY-1979 and "Measurement of Airborne Concentrations and Dislodgeable Residues of Selected Pesticides in Greenhouse Crop Production" NCRPIAP Project #97 (52-NC-OH-O) FY-1980. The Ohio Agricultural Research and Development Center, The Ohio State University. Unpublished Final Research Reports submitted to the NCRPIAP Regional Office, Columbus, Ohio and to USDA-CSRS-S&E. Hemphill, D.D. "Concentrations of Selected Agricultural Chemicals in the Greenhouse Atmosphere" NCRPIAP Project #105 (48-NC-MO-O), FY-1980. University of Missouri. Unpublished Final Research Report submitted to the NCRPIAP Regional Office, Columbus, Ohio and to USDA-CSRS-S&E.

RECEIVED August 28, 1984


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