Dermal exposure sampling techniques

Hsu, I.P., C.E. Camann, E. Schattenberg m, B. Wheeler, K. Villalobos, S. Quarderer and R.G. Lewis (1990). New dermal exposure sampling technique, in Total Exposure Assessment Methodology A New Horizon, Pubhcation VIP-16, Air and Waste Management Association, Pittsburgh, PA, USA, pp. 489-497. 

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

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... 

Measuring clothing or dermal exposure A cloth pad sampling technique may be used to determine the amount of pesticide... 

Patches are essentially spot or grab samples (typically 25 cm ) of the skin, whereby dermal exposure is assessed by extrapolating the patch loading level to the surface of the entire body. Given that only a small area of exposed skin is covered by the patches used, the uncertainties in calculating true exposure are likely to be high. Furthermore, the exposure pattern may vary with time, with activities, and both within and between individuals, days and shifts. However, several field studies have shown that this technique is a useful tool in the identification and evaluation of dermal exposures to a range of workplace contaminants and in the assessment of the effectiveness of personal protective equipment (Fenske et al. 1990). 

In designing a sampling strategy for dermal exposure, the sampling must at least be representative that is, all skin surfaces with potential exposure need to be identified and monitored using a validated technique. The sampling duration should take into account the exposure time and the requirements of the technique used. Furthermore, all controls used to minimise skin exposure, such as gloves, should be identified and evaluated with reference to their theoretical protection values, actual use time and frequency of use. 

Unresolved Issues Include how many samples of each are required and how can one relate dose to absorption, excretion to AAChE, or (of academic Interest) dose to excretion. The difficulty in correlating dermal dose and excretion (2,26,27) is related in part to the differences mentioned earlier between measuring dose with pads-and-gloves and washing the skin (2,18). The correlation difficulty is most severe with the skin wash technique because it measures the dose that isn t absorbed. Depending upon the time-history of exposure and the kinetics of absorption, it should be equally expected that dermal dose by washing and urinary excretion will even... 

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