ATTACHMENT F Evaluation of PCB Dermal Absorption Factor Used in HHRA

In the Human Health Risk Assessment (HHRA) for the Housatonic River, EPA has used an absorption factor of 14 percent to evaluate dermal exposure to PCBs. This dermal absorption factor is based on a study by Wester et al. (1993) of PCB absorption from the soil into the skin of Rhesus monkeys. As discussed below, that study used soil with a large particle size and very low organic carbon content, which are not typical of floodplain soils, including those in the Housatonic River floodplain, and also used PCB mixtures different from the predominant mixture found at this site. Theoretical considerations and empirical data suggest that the dermal absorption factor estimated by Wester et al. (1993) almost certainly overstates absorption of PCBs from soils and sediments at this site. Indeed, a more recent dermal absorption study by Mayes et al. (2002), employing the same general protocol as Wester et al. (1993) but using soil with a more typical particle size and organic carbon content, as well as Aroclor 1260 (the predominant PCB mixture at this site), reported dermal absorption of around 4 percent. Although both studies have limitations, GE believes that the Mayes et al. (2002) results are more representative of site-specific soils at this site and thus should be used as the basis for the dermal absorption factor in the HHRA.