Effects of Soil and Aging on the Dermal Bioavailability of Hydrocarbons and Metals in Soil

The potential health risk from exposure to chemically contaminated soil can be assessed from bioavailability studies. The aims of this research were: (a) to determine the dermal bioavailability of contaminants in soil for representatives of hydrocarbon classes of chemicals, namely, volatiles (toluene) and polycyclic aromatic hydrocarbons [benzo(a)pyrene] as well as for heavy metals (arsenic, mercury, and nickel, respectively, as arsenic acid, mercuric chloride, and nickel chloride); and (b)to examine the effects of soil matrix and chemical sequestration in soil with time (“aging”) on their bioavailability. In vitro flow-through diffusion cell studies were performed utilizing dermatomed male pig skin and radioactive chemicals to measure dermal penetration. The volatility of toluene reduced the amount of the chemical available for dermal penetration. With soil contact, the penetration of toluene was 16-fold to 21-fold less than toluene without soil. Benzo(a)pyrene penetration was decreased faster in soil with a higher clay content than one with more organic carbon. The soil matrix as well as aging in soil lowered the dermal penetration of the metal compounds by 95-98%. This study provided evidence that the bioavailability from dermal exposure to the chemicals examined can be significantly reduced by soil matrix and aging in soil