Dermal exposure applicators

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. 

Three animal studies were located regarding distribution of endosulfan in animals following dermal exposure (Dikshith et al. 1988 Hoechst 1986 Nicholson and Cooper 1977). Endosulfan was detected in the brain (0.73 ppm), liver (3.78 ppm), and rumen contents (0.10 ppm) of calves that died after dermal exposure to a dust formulation of endosulfan (Nicholson and Cooper 1977). Following a single dermal application of aqueous suspensions of 0.1, 0.83, and 10.13 mg/kg C-endosulfan to male Sprague-Dawley rats, low concentrations of endosulfan (ng/g levels) appeared in the blood and tissues (other than skin at and around the application site) after 1 hour (Hoechst 1986). The concentrations of endosulfan in the blood and tissues increased with the time of exposure and were proportional to the dose applied. The liver and kidney appeared to sequester radiolabel relative to the concentrations of radiolabel in the blood or fat. Endosulfan levels were approximately 10 times higher in the liver and kidney than in the fat, blood, and brain throughout the study (Hoechst 1986). 

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. 

D.R. Hackathorn and D.C. Eberhart, Database proposal for use in predicting mixer-loader/applicator exposure, 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. 341-355 (1985). 

Methods for reducing peak absorption of americium after inhalation or oral exposure have not been described. Topical applications of saline containing DTP A, tartaric acid, or citric acid (e.g., Schubert s solution) have been used to remove americium from the skin and wounds after accidental dermal exposures (Breitenstein 1983). These agents form stable, water soluble complexes with americium. 

Organophosphate Ester Hydraulic Fluids. Organophosphate ester hydraulic fluids are used in applications that require a degree of fire resistance such as in aircraft. EPA (1992b) has noted that aircraft mechanics may have dermal exposures of 1,300-3,900 mg/day and that 2,200 aircraft workers are routinely exposed to tributyl phosphate, while another 43,000 mechanics may be exposed at various times. Estimates of worker exposure in other industries were not found in the available literature. General population and military personnel exposure to organophosphate ester hydraulic fluids is likely to be much lower than exposure to mineral oil hydraulic fluids because these fluids have more specialized uses. 

In order to evaluate "within-worker" variances of dermal exposure and its distribution over the body, whole-body monitoring during three applications and concomitant re-entry was performed for high-volume (HV) applicators (n = 4) and harvesters of carnations (n = 6). 

The variances of potential dermal exposure are presented in Table 1. Very large "within-worker" variances of potential exposure of the hands resulted in insignificant differences between workers. For harvesters, a similar result was obtained for potential exposure of the body parts. For both applicators and harvesters, significant "between-worker" differences of total potential exposure were observed. 

Figure 1 Distribution of the potential dermal exposure of applicators (N = 3, n = 9) to propoxur and of harvesters (N = 6, n = 18).

For applicators, hand exposure was approximately 15% of the total potential dermal exposure. 

The design of a study by Davies et al. (1982) for mixers and applicators was similar to that of Nigg and Stamper (1983). "Between-days" variances of exposure were not given. Mean urinary metabolite concentrations were used to show reduction of internal exposure by protective clothing. The design of the study by van Rooij et al. (1993) was similar to our study (i.e., "within-worker" comparisons of internal exposure). Because no potential dermal exposure was assessed in this study, "within-worker" variances of potential exposure are not known. 

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. 

Research has shown a clear relation between the amount of dislodgeable residues on the crop and the level of dermal exposure (van Hemmen, 1995). The maximum amount of dislodgeable residues is found immediately after application and depends on ... 

It is therefore advisable to group the various crop habitats and maintenance activities into "re-entry scenarios" and to determine whether standard values for the initial DFR shortly after the first application and generic transfer factors for the level of dermal exposure for each scenario can be developed. Investigations to this end have been carried out over the last two decades, primarily in the U.S. The generic transfer factors for a number of... 

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. 

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