Transfer of Polycyclic Aromatic Hydrocarbons From Urban Soils to Humans Via Dermal Absorption.

Polycyclic Aromatic Hydrocarbons (PAHs) are a group of carcinogenic organic pollutants. Urban soils may contain high concentrations of PAHs originated from automobile exhaust, industrial emissions, and creosote treated woods. In the context of gardening, dermal absorption could be a significant pathway of transferring soil PAHs to humans. The objective of this study was to evaluate potential for transfer of soil PAHs to humans via skin; specifically, the effect of soil matrix, the effect of soil moisture content, and the effect of aging of PAHs in soil on dermal transfer of PAHs. The treatments were soil contaminated with PAHs at two moisture contents (20 % and 40 % (v/v)), soil contaminated with PAHs+biosolids, control soil, control soil spiked with PAHs (0, 1, 3 and 12 days of incubation after spiking), and PAHs dissolved in methanol. The concentrations of the 16 priority PAHs were the same for all the treatments, except for the biosolids and the control soil treatments. We conducted two experiments: 1) an in-vitro steady fluid experiment to evaluate the potential for transfer of PAHs from soil to blood through skin, and 2) a fluorescent microscopy study to determine the penetration depths of PAHs in skin.  Only low (152-178 g mol^-1) and medium (202 g mol^-1) molecular weight PAHs in methanol transferred through skin. The PAHs in any of the contaminated soil treatments did not transfer through skin; however, fluorescence microscopy revealed that the PAHs in those treatments penetrated to a certain degree in the epidermis. In the PAHs spiked treatments at 0^th or 1^st or 3^rd day of spiking, several low molecular weight PAHs transferred through the skin. In contrast, spiked soil incubated for 12 days after spiking, did not show detectable levels of PAHs transferring through the skin. Soil matrix and aging of PAHs in soil restricted transfer of soil PAHs from soil to humans via skin.