Pesticide dermal exposure

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. 

Dermal Exposure Of the three major routes of exposure, the dermal (skin) route constitutes nearly 90% of chemical exposure, particularly of pesticides. Dermal exposure is common whenever chemicals are mixed or handled. Certain types of dry materials, (e.g., pesticide dusts, wet or dry powders, granules, liquid pesticides) enter the body through quick skin absorption. Many factors influence the rate of dermal exposure of a chemical these may be as follows ... 

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

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. 

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. 

Most of the hterature reviewed concerning the health effects of endosulfan in humans described case reports of occupational exposure and accidental or intentional ingestion of endosulfan. The cases of occupational exposure to endosulfan concerned exposures of acute-to-intermediate durations, and the cases of oral exposure were exclusively acute-duration exposure situations. The predominant route of exposure in the occupational case reports is believed to be inhalation, but the possibility of some degree of dermal exposure cannot be ruled out. The information on human exposure is limited because the possibility of concurrent exposure to other pesticides or other toxic substances cannot be excluded. In addition, the precise duration and level of exposure to endosulfan generally cannot be quantified from the information presented in these reports. 

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. ... 

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). 

Means and standard deviations for these distributions were normalized to daily breathing rates (m3/day), and an acceptable range was defined. It was assumed that the "day" represents the duration of time within a working day that chlorpyrifos may be handled by an individual (0.25 to 6.0 hr). It was also assumed that exposures would be negligible for the remainder of the working day following application or other contact. Both the dermal and inhalation exposures were assumed to follow lognormal distributions, which is consistent with common practice for exposure data distributions (for example, in the Pesticide Handlers Exposure Database, PHED). 

Chester, G., Loftus, N.J., Woollen, B.H., and Anema, B.P. (1990b) The effectiveness of protective clothing in reducing dermal exposure to, and absorption of, the herbicide fluazifop-P-butyl by mixer-loader-applicators using tractor sprayers, in Book of Abstracts, Seventh International Congress of Pesticide Chemistry, Vol. Ill, Freshe, H. and Kesseler-Smith, E., Eds., Conway, Hamburg. 

Fenske, R.A. (1988) Comparative assessment of protective clothing performance by measurement of dermal exposure during pesticide applications, Appl. Ind. Hygiene, 3 207-213. 

Franklin, C. (1985) Occupational exposure to pesticides and its role in risk assessment procedures used in Canada, in Dermal Exposure Related to Pesticide Use, Honeycutt, R., Zweig, G., and Ragsdale, N.N., Eds., ACS Symposium Series No. 273, American Chemical Society, Washington, D.C. 

Re-entry exposure can be considered to be the result of a chain of processes ending with the transfer of pesticide residues to the worker. Popendorf (1985) assumed a linear relationship between dermal exposure (DE) and the amount of residue available to transfer from the foliage to the worker. This is called the dislodgeable foliar residue (DFR) ... 

Dermal exposure during repeated re-entry is assumed to differ from the first re-entry only because of dissipation of the pesticide (Popendorf, 1985). However, there are indications from previous studies in the cultivation of... 

Dermal exposure was performed using pre-washed cotton gloves covering the hands and forearms (stretch-cotton, 200 g/m2 surface (one-sided) 370 cm2 J. van der Wee BV Riel, The Netherlands). A pair of gloves was used for a maximum period of one hour in order to prevent breakthrough of the pesticide(s). Anew pair was provided after each hour of harvesting, or earlier... 

The first pesticide exposure study was reported by Griffiths et al. (1951). Parathion was trapped on respirator filter discs during application to citrus trees. Batchelor and Walker (1954) expanded exposure monitoring to include the estimation of potential dermal exposure using pads attached to workers clothing. Durham and Wolfe (1962), in their classic review of worker exposure methodologies, also provided some experimental validation for the best available methods. 

---