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MITAL RELEASE DDJC Tracy through dermal contact are approximately equal to ingestion, the estimated combined dose for both exposure routes is still less than the acceptable MRLs or RIDs. In general, uptake of metals or pesticides through skin is less than uptake through ingestion. Estimated Exposure Dose for Ingestion of Fish from the Stormwater Lagoon Lead, mercury, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, dieldrin, chlordane, and DDT and its derivatives were detected in lagoon sediment. With the exception of PAHs and dieldrin concentrations, which slightly exceeded ATSDR's conservative CREGs, contaminant concentrations were below ATSDR's comparison values for soil. Because even low sediment concentrations may be associated with elevated fish tissue levels, ATSDR estimated a contaminant concentrations in fish by multiplying the maximum sediment concentrations by a sediment to fish bioaccumulation factor(BAF). The BAF considers fish uptake from water, food, and sediment. Using the estimated fish tissue concentration, ATSDR then used the following equation to estimate exposure doses for ingestion of lagoon fish: Estimated exposure dose = COng, x IR x EF x ED BWxAT where: Conc. = Estimated concentration in fish (mg/kg) (maximum sediment concentration x compound's bioaccumulation factor [BAF]) IR = Ingestion rate: 0.0065 kg/day (approximately one 8-ounce meal per month), average consumption of fish and shellfish from estuarine and freshwater by the general U.S. population (EPA, 1989) EF = Exposure frequency, or the number of exposure events (7 days x 50 weeks or 350 days per year) ED = Exposure duration, or the duration over which exposure occurs: 30 years BW = Body weight (kg): 70 kg (154 pounds) AT = Average time or the time over which cumulative exposures are averaged (noncancer- 30 years, cancer-70 years x 365 days) C-6