DERMAL DOSE. Although dermal contact is not expected to represent a significant route of exposure, a simple calculation of potential dose may be performed for construction workers who could potentially contact contaminated groundwater during excavation or trenching activities. The amount of a chemical that a person may absorb due to dermal contact with contaminated environmental media depends on the following factors: o Chemical concentration in water, o Quantity of media in contact with skin, o Skin surface area contacted, o Frequency of exposure o Duration of exposure, and o Bioavailability of the chemical. The following equation identifies the relevant factors in the calculation of dose through the dermal route of exposure: Dermal Dose = Chemical x (10(-3) mg/ug) x (Area) x ET x DAR ------------------------------------------- WT Where: Dermal Dose = Dose received by dermal absorption of contaminants in water (mg/kg) [Water) = Concentration of chemical in water (ug/g, or ppm x 10(-6) 286 Area = Average exposed skin surface area (cm(2))[an average total body skin surface area is 17,535 cm(2) (Snydxx, xx al., 1975)] ET = Exposure time (minutes) DAR = Dermal absorption rate (ug/cm(2)-min) WT = Average human body weight (70 kg) Table 4-6 identifies the maximum detected concentrations of chemicals in shallow groundwater from the site (Levixx-Xxxxxx, 0089a, and McLaren 1989). Ideally, the potential dose from dermal contact with each of these compounds based on a typical concentration in the shallow ground water would be evaluated. However, the needed values relative to uptake rates and acceptable levels of exposure or cancer potency are available for only a few of the compounds. Therefore, an alternative is to examine representative compounds and infer the potential health impacts from exposure to multiple compounds. For the purposes of this assessment, ethylbenzene, a non-carcinogenic compound which was detected in the highest concentration of all the compounds present, and benzene, a carcinogenic chemical will be evaluated.
