Fluorescent tracers, dermal exposure

Fenske, R.A. (1988) Correlation of fluorescent tracer measurements of dermal exposure and urinary metabolite excretion during occupational exposure to malathion, Am. Ind. Hygiene Assoc. /., 49 438-444. 

Estimation of Respiratory Exposure 23 Estimation of Dermal Exposure 23 Surrogate Skin Techniques 23 Chemical Removal Techniques 25 Fluorescent Tracer Techniques 27 Estimation of Exposure to Children in the Home 27 Biological Monitoring 28... 

Dermal exposure sampling methods fall into three general categories surrogate skin techniques, chemical removal techniques and fluorescent tracer techniques (Fenske, 1993a). 

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. 

Fenske, R.A. (1988). Visual Scoring System for Fluorescent Tracer Evaluation of Dermal Exposure to Pesticides, Bull. Environ. Contam. Toxicol, 41, 727-736. 

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. 

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

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. 

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

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. 

The impetus for this study came from a realization that the traditional patch technique ( ) was inherently limited in its ability to accurately measure dermal exposure, and from the great potential which a fluorescent tracer methodology appeared to hold. The ability to visualize exposure immediately provides valuable qualitative information regarding the exposure process. When combined with a video image processing system which quantifies fluorescence, the possibility of carefully characterizing dermal exposure seemed well worth the effort involved. 

As methods of exposure estimation, neither the fluorescent tracer technique nor the patch technique have been validated. Nevertheless, it would be encouraging if a comparison of estimates by the two methods yielded roughly equivalent results. The only body region which can be reasonably compared is the head, as the patch method assumes no clothing penetration, and no hand wash was conducted in this study. Furthermore, four of the six workers must be excluded, as they wore face shields. Thus, the only comparison available is the head and neck exposure of workers 1 and 2. These data are presented in Table IX. Following the protocol outlined by Durham and Wolfe ( ) and Davis ( ), the amount of diazinon recovered from the dermal monitor on the chests of the two workers is employed to calculate exposure to the face and front of neck. A similar patch on the back allows calculation of exposure to the back of the neck. 

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. 

Questions arise as to the necessity of monitoring protected areas if only 23.3 percent of the total dermal exposure occurs in these areas. A qualitative study of worker exposure using fluorescent tracers led to the conclusion that "results depend critically on knowing where to place the pads" (11). This study also demonstrated that the principal exposure was to the face, hands, and neck. 

Dermal exposure can be quantified directly and non-invasively by measuring deposition of fluorescent materials. A fluorescent tracer is added to the sub-... 

The use of fluorescent compounds can be coupled with video-imaging analysis to produce exposure estimates over virtually the entire body (Fenske and Bim-baum, 1997). This approach requires pre- and post-exposure images of skin surfaces under long-wavelength ultraviolet illumination, development of a standard curve relating dermal fluorescence to skin-deposited tracer, and chemical residue sampling to quantify the relationship between the tracer and the chemical substance of interest as they are deposited on the skin. 

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