Tracers dermal exposure assessment

Fenske, R.A., J.T. LeffingweU and R.C. Spear (1985). Evaluation of Fluorescent Tracer Methodology for Dermal Exposure Assessment, in Dermal Exposure Related To Pesticide Use, R.C. Honeycutt, G. Zweig and N.N. Ragsdale (Eds), ACS Symposium Series 273, American Chemical Society, Washington, DC, USA, pp. 377-393. 

Evaluation of Fluorescent Tracer Methodology for Dermal Exposure Assessment... 

Fenske, R.A., Wong, S.M., Leffingwell, J.T., and Spear, R.C. (1986b) A video imaging technique for assessing dermal exposure. II. Fluorescent tracer testing, Am. Ind. Hygiene Assoc.., 47 771-775. 

Fluorescent tracer techniques hold the promise of improved accuracy in assessing dermal exposures, as they require no assumptions regarding the distribution of exposure across skin surfaces. However, this approach also has several limitations. First, it requires introduction of the tracer compound into the agricultural spray mix. Secondly, there must be demonstration of a correspondence between pesticide deposition and deposition of the fluorescent compound for the production, such that the fluorescence can indeed be considered a tracer of chemical deposition. Thirdly, range-finding and quality assurance studies may be needed to ensure the accuracy of tracer measurements. Fourthly, when protective clothing is worn by workers, the relative penetration of the pesticide and tracer needs to be characterized. All of these limitations make fluorescent tracer methods technically challenging. 

The feasibility of employing fluorescent tracers and video imaging analysis to quantify dermal exposure to pesticide applicators has been demonstrated under realistic field conditions. Six workers loaded a tracer with the organophosphate pesticide, diazinon, into air blast sprayers, and conducted normal dormant spraying in pear orchards. They were examined prior to and immediately after the application. UV-A illumination produced fluorescence on the skin surface, and the pattern of exposure was digitized with a video imaging system. Quantifiable levels of tracer were detected beneath cotton coveralls on five workers. The distribution of exposure over the body surface varied widely due to differences in protective clothing use, work practices and environmental conditions. This assessment method produced exposure values at variance with those calculated by the traditional patch technique. 

Unfortunately the Ideal situation does not exist and there are many difficulties which must be overcome before accurate risk assessments can be conducted. For pesticide applicators, the dermal route has been shown to be the most Important one. However, the methods used to measure the amount of pesticide landing on the skin are not very reliable and many studies conducted In the past did not try to estimate hand exposure. This omission Is a serious one because it has been shown that a very large percentage of the total dermal exposure Is to the hands. New methods using fluorescent tracer techniques are promising and will undoubtedly lead to more quantitative estimates of contact exposure. 

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. 

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