Dermal absorption of the lipophile and potential carcinogen benzo[a]pyrene (BaP) in soils from contaminated sites was simulated in vitro using human skin exposed to 14C-BaP-spiked soil. This study is the first in a series of tests at Health Canada with several soil contaminants spanning a wide range of lipophilicity conducted with viable human skin. Breast skin was obtained fresh from a local hospital and dermatomed to a thickness of 0.4-0.5 mm. Teflon Bronaugh diffusion cells were perfused with HEPES buffered Hanks saline (pH 7.4) with 4% bovine serum albumin (BSA) and fractions were collected at 6-h intervals for up to 24 h exposure either to 14C-BaP applied in acetone or spiked in a commercial gardening soil. As skin depot 14C levels were still high at 24 h, the study was repeated for up to 42 h to examine skin depot bioavailability. Skin was washed with soapy water at 24 h in both the 24- and 42-h studies. Exposure to 14C-BaP both with and without soil was conducted in triplicate with skin specimens from at least 4 patients. In the 24-h exposure tests including the skin depot there was 15 and 56% absorption with and without soil, respectively. The lower total percent absorption from the spiked soil applied to skin resulted from lower depot absorption of 8% with and 45% without soil. Data for 42-h studies were similar and revealed no significant decrease in skin depot levels. Including the 42-h depots there was 16 and 50% absorption with and without soil, respectively, with respective depots of 7 and 39%. As there was no significant difference between the 24- and 42-h depots both with and without soil, the data suggest the depot for BaP was not bioavailable for at least the additional 18-h post soap wash exposure. The bioavailability of BaP is discussed in relation to previous in vitro and in vivo studies in perspective with dermal exposure to contaminated soils.

Dermal absorption of heavy metal soil contaminants was tested in vitro with chloride salts of radioactive nickel (Ni-63) and mercury (Hg-203). Aqueous soil suspensions, spiked with either Ni-63 or Hg-203, were applied to fresh viable human breast skin tissue in Bronaugh diffusion cells perfused with Hanks HEPES buffered (pH 7.4) receptor containing 4% bovine serum albumin (BSA). Receptor fractions were collected every 6 h for 24 h when skin was soap washed. Tests were conducted concurrently in triplicate with and without soil for each skin specimen. Mean percent dermal absorption including the skin depot for Ni-63 was 1 and 22.8% with and without soil, respectively, while for Hg-203, values of 46.6 and 78.3% were obtained. Excluding the skin depot and considering only absorption in receptor, there was 0.5 and 1.8% absorption of Ni-63 with and without soil, respectively, and 1.5 and 1.4% for Hg-203. The potential bioavailability of the skin depot is discussed in relation to dermal exposure to these metals in contaminated soil.

Dermal absorption of contaminants from soils at federal contaminated sites in Canada was investigated using one hydrophile, (14)C-ethylene glycol (EG), and one lipophile, (14)C-nonylphenol (NP). In vitro dermal absorption of EG and NP was examined in dermatomed (0.4-0.5 mm) human skin using Bronaugh Teflon flow-through cells with Hanks HEPES buffered (pH 7.4) receiver solution with 4% bovine serum albumin (BSA). Tests were conducted under occlusive conditions with and without a commercial gardening soil spiked with EG or NP applied to skin at a soil load of 5 mg/cm(2). With percent absorption in skin depot included, a total of 9.9 + or - 6.28% (n = 6) and 34.8 + or - 8.47% (n = 6) absorption of EG with and without soil, respectively, and 20.6 + or - 5.56% (n = 7) and 41.1 + or - 6.46% (n = 7) of NP, with and without soil, respectively, were obtained. For tests without soil a reverse pattern was observed with significantly lower percent absorption into the receiver than depot with the lipophile NP, but significantly higher percent absorption in receiver versus depot for the hydrophile EG. This pattern was different in tests with soil, and caution needs to be exercised when extrapolating data from in vitro tests conducted without soil in human health risk assessments at contaminated sites.