Dermal absorption of environmental contaminants from soil and sediment: a critical review

Risk assessment of hazardous wastes sites may require characterization of the dermal availability of chemical contaminants in soil and/or sediment. Current U.S. Environmental Protection Agency guidance for assessment of dermal exposures to contaminants in water and soil was finalized in 2004 as a supplement (Part E) to the Risk Assessment Guidance for Superfund (RAGS). The soil protocol presented in RAGS Part E is less sophisticated than the water protocol and is supported by less empirical data. Investigations of dermal absorption of soil and sediment-borne contaminants that have been conducted to date include in vitro and in vivo experiments using both human and surrogate skin. A review of that literature was conducted with attention to relevant criteria including consideration of layering effects, degree of chemical saturation of soil, appropriateness of particle size distribution employed, soil-chemical contact time, and continuity of soil-skin contact (in in vivo studies). Most studies published to date are deficient by virtue of execution or reporting on one or more of the selected criteria. In addition the lack of methodological standardization evident in the literature hinders systematic evaluation of results. Since additional experimental work is needed, general agreement on acceptable approaches would be useful. Recommendations for good practice are presented.