A Novel “By Difference” Method for Assessing Dermal Absorption of Polycyclic Aromatic Hydrocarbons from Soil at Federal Contaminated Sites

Abstract

A highly precautionary cost-effective method for estimating dermal absorption using data from 24-h skin soap washes from in vitro dermal absorption tests in Bronaugh flow-through diffusion cells with human skin is reported. Skin was dosed with 16 U.S. Environmental Protection (EPA) priority polycyclic aromatic hydrocarbons (PAH) applied in mixture each at 2 μg/ml (ppm) in acetone without soil. Concurrent tests were conducted with an unspiked aqueous suspension of PAH-contaminated soil obtained from a Canadian federal contaminated site. Percentage dermal absorption was estimated “by difference” from the applied dose and that detected by high-performance liquid chromatography (HPLC) in 24-h skin soap washes. The dermal absorption for 11 PAH ranged from 71 to 88.3% without and with soil, respectively. Lower absorption was found for 5 PAH in soil, in the range of 26.4 to 60.8%. Data could not be corrected for evaporative loss due to inconsistent data from Tenax adsorbent. Corroboratory gas chromatography/mass spectroscopy (GC/MS) tests are needed. Previously published in vitro data from the authors' laboratory supported use of the “by difference” method.

Acknowledgments

We thank Dr. Gloria Rockwell and Dr. Murray Allen with the Ottawa Hospital for kind provision of human skin. This project was approved by research ethics boards at both Ottawa Hospital and Health Canada. We thank Health Canada, Contaminated Sites Division, for internal project funding. We also thank Nanqin Li (Environment and Occupational Toxicology Division) and Jiping Zhu (Exposure and Biomonitoring Division [EBD], Health Canada) for fruitful discussions on PAH volatility and Raymond Poon (Hazard Identification Division) and Jiping Zhu for internal review. Finally we thank David Moir (Chief, EBD) for expert advice on HPLC analysis.