Pesticide dermal

Kissel, J.C. and R.A. Fenske (2000). Improved estimation of dermal pesticide dose to agricultural workers upon re-entry, Appl. Occup. Environ. Hyg., 15, 1-7. 

Zweig, G., J.T. Leffingwell and W.J. Popendorf (1985). The relationship between dermal pesticide exposure by fruit harvesters and dislodgeable foliar residues, J. Environ. Scl Health, B20, 27-59. 

I thank Dr. Ronald Baynes for his invaluable input and guidance in tutoring me on ihe fine points of experimentally assessing dermal pesticide absorption. 

W. J. Popendorf The Relationship Between Dermal Pesticide Exposure by Fruit Harvesters and Dislodgeable Foliar Residues,/. Environ. Sci. Tilth., 1985, B30, 27-59. 

This book provides an up-to-the-minute picture of the current status of research on measurement and risk assessment of dermal pesticide exposure for agricultural workers. The chapters also provide an insight into some newer areas (applications of mathematical models, use of fluorescent tracer materials, and extrapolation from a computer data base of generic pesticide exposure data) that will undoubtedly be receiving increased attention in the future. 

Encapsulated dia2innon sold as Knox-Out 2FM is a commercial encapsulated pesticide formulation said to have reduced dermal and oral toxicity as well as prolonged effectiveness. The capsules, prepared by interfacial polymeri2ation, are claimed to be highly effective against cockroaches with no objectionable odor and low insect repeUence. The capsules are beheved to function as a contact poison when insects walk on it and as a stomach poison when insects preen capsules stuck to their legs and ingest them (71). 

Encapsulated fonofos, a soil insecticide, was developed to coat seeds before they were planted (72). Encapsulation reduces oral toxicity 100-fold and dermal toxicity 10-fold while extending activity of the fonofos. Other encapsulated pesticides available include permethrin and parathion (69). Significantly, all commercial encapsulated pesticides are prepared by interfacial polymeri2ation. 

EH 74/3 Dermal exposure to non-agricultural pesticides exposure assessment document... 

Dermal exposure to methyl parathion is not likely to be a health concern to the general population, with the possible exception of individuals in the immediate vicinity of a field during application of the pesticide. Dermal exposure, however, is a major source of exposure for workers directly involved in the manufacture, application, and cleanup of the chemical, and for field workers. Laundry workers cleaning the clothing of such workers may also be exposed. 

Erythrocyte cholinesterase levels were monitored in two men exposed dermally to methyl parathion after entering a cotton field that had been sprayed with this pesticide (Nemec et al. 1968). The field was entered on two separate occasions twice within 2 hours after an ultra-low-volume spraying and a third time within 24 hours after spraying. Dermal methyl parathion residues 2 hours after spraying were 2-10 mg on the arms dermal residues 24 hours after spraying were 0.16-0.35 mg on the arms. The exposed individuals did not have signs of cholinergic toxicity, but erythrocyte cholinesterase levels after the third exposure were 60-65% of preexposure levels. 

Mice that were exposed dermally to residues of methyl parathion in emulsifiable concentrate on foliage, and were muzzled to prevent oral intake, developed inhibition of plasma cholinesterase and erythrocyte cholinesterase after two 10-hour exposures (Skinner and Kilgore 1982b). For the organophosphate pesticides tested in this study, cholinergic signs generally were seen in mice with cholinesterase inhibition >50% results for this end point were not broken down by pesticide. 

In a case-control study of pesticide factory workers in Brazil exposed to methyl parathion and formulating solvents, the incidence of chromosomal aberrations in lymphocytes was investigated (De Cassia Stocco et al. 1982). Though dichlorodiphenyltrichloroethane (DDT) was coformulated with methyl parathion, blood DDT levels in the methyl parathion-examined workers and "nonexposed" workers were not significantly different. These workers were presumably exposed to methyl parathion via both inhalation and dermal routes however, a dose level was not reported. The exposed workers showed blood cholinesterase depressions between 50 and 75%. However, the baseline blood cholinesterase levels in nonexposed workers were not reported. No increases in the percentage of lymphocytes with chromosome breaks were found in 15 of these workers who were exposed to methyl parathion from 1 week to up to 7 years as compared with controls. The controls consisted of 13 men who had not been occupationally exposed to any chemical and were of comparable age and socioeconomic level. This study is limited because of concomitant exposure to formulating solvents, the recent history of exposure for the workers was not reported, the selection of the control group was not described adequately, and the sample size was limited. 

Although the extent of absorption was not measured, the above evidence suggests that absorption in humans occurs rapidly following dermal exposure to commercial pesticide formulations of methyl parathion. 

Figure 3-5 graphically depicts the information that currently exists on the health effects of methyl parathion in humans and animals by various routes of exposure. The available literature reviewed concerning the health effects of methyl parathion in humans described case reports of longer-term studies of pesticide workers and case reports of accidental or intentional ingestion of methyl parathion. The occupational exposure is believed to be via the dermal and inhalation routes. The information on human exposure is limited in that the possibility of concurrent exposure to other pesticides or other toxic substances cannot be quantified. 

Wolff MS, McCoimell R, Cedillo L, et al. 1992. Dermal levels of methyl-parathion, organochlorine pesticides, and acetylcholinesterase among formulators. Bull Environ Contam Toxicol 48 671-678. 

The only study located regarding immunological effects in humans after dermal exposure to endosulfan was an account of the results of patch tests on the backs of 14 farm workers with work-related dermatitis and 8 controls who were not exposed to pesticides (Schuman and Dobson 1985). Skin sensitization was not observed in any of the subjects following a 48-hour, closed-patch exposure to an unspecified amount of 0.1 % endosulfan in petrolatum. 

The most important routes of exposure to endosulfan for the general population are ingestion of food and the use of tobacco products with endosulfan residues remaining after treatment. Farmers, pesticide applicators, and individuals living in the vicinity of hazardous waste disposal sites contaminated with endosulfan may receive additional exposure through dermal contact and inhalation. 

In occupational settings, exposure to endosulfan is mainly via the dermal and inhalation routes. Although workers involved in the manufacture and formulation of pesticide products containing endosulfan are potentially exposed to high concentrations of the compound, actual exposure is probably limited by the use of engineering controls and personal protection equipment. The highest documented dermal and inhalation exposures have been reported for agricultural workers involved in the spray... 

EPA. 1990a. Endosulfan Review of four toxicology studies and three dermal absorption studies. Memorandum. Washington, DC U.S. Environmental Protection Agency, Office of Pesticides and Toxic Substances. Document no. 007937. 

Applicators, mixers, loaders, and others who mix, spray, or apply pesticides to crops face potential dermal and/or inhalation exposure when handling bulk quantities of the formulated active ingredients. Although the exposure periods are short and occur only a few times annually, an estimate of this exposure can be obtained by quantifying the excreted polar urinary metabolites. Atrazine is the most studied triazine for potential human exposure purposes, and, therefore, most of the reported methods address the determination of atrazine or atrazine and its metabolites in urine. To a lesser extent, methods are also reported for the analysis of atrazine in blood plasma and serum. 

Farm worker exposure to pesticides has been studied extensively over the past 30 years.This scientitic discipline has evolved from the days when respiratory exposure of farm workers was measured using gauze dosimeters placed inside respirators to collect airborne pesticide residues to very sophisticated air sampling devices and remarkable dosimeter devices to measure dermal exposure to farm workers. ... 

Among the first dermal dosimeters used in exposure research were 4 x 4-in cellulose or gauze patches which were pinned to the outer and inner surfaces of clothing or vests which farm workers would wear during the application or re-entry phase of the smdy. These patches were easy to manufacture and when pinned to the shirt or pants of the worker made for an easily used dosimeter pad. The major advantage to the use of the patch to estimate worker exposure was this method s ability to differentiate the relative contributions of pesticide residues to different parts of the worker s body. This sampling technique in turn could lead to recommendations (i.e., the use of... 

The purpose of this article is to present a detailed description of the current field methods for collection of samples while measuring exposure of pesticides to farm workers. These current field methods encompass detailed descriptions of the methods for measuring respiratory and also dermal exposure for workers who handle the pesticide products directly (mixer-loaders and applicators) and for re-entry workers who are exposed to pesticide dislodgeable residues when re-entering treated crops. 

Both inner and outer whole-body dosimeters are common tools to measure successfully dermal exposure to pesticide workers and are employed in a variety of ways in mixer-loader/applicator or re-entry studies. 

W.J. Popendorf, Advances in the unified field model for reentry hazards, in Dermal Exposure Related to Pesticide Use Discussion of Risk Assessment, ed. R.C. Honeycutt, G. Zweig, and N.N. Ragsdale, ACS Symposium Series 273, American Chemical Society, Washington, DC, pp. 323-340 (1985). 

---