Marley Shoaf

Project title: Dermal Exposure to Sediment: Field Measurement of Sediment Loadings and Unresolved Issues in Exposure Assessment

Degree: MS | Program: Environmental Health (EH) | Project type: Thesis/Dissertation
Completed in: 2004


The National Sediment Quality Survey identified over 10,000 sampling stations at which sediment quality was categorized as presenting probable risk of adverse effects on human health or aquatic organisms (U.S. EPA, 1997a,b, c; U.S. EPA, 2001a). Contaminated sediments were found in all 50 states. Human exposure to contaminants in sediments could potentially occur via dermal contact during various recreational and occupational activities. An informal survey of the U.S. Environmental Protection Agency (EPA) regional offices was conducted to determine whether dermal sediment contact h as been identified as an exposure pathway of concern in the context of evaluation Superfund and Resource Conservation and Recovery Act (RCRA) sites. Multiple site assessments incorporating a dermal exposure pathway were found. Locations of contaminated sites included tidal estuaries, wetlands, marshes, rivers, creeks, lakes and ponds. Activities associated with potential sediment contact considered in the assessment included fishing, shell fishing/collecting, wading, boating, hunting, trespassing, playing, pier maintenance and construction work.

EPA's supplemental guide to dermal risk assessment states that the adherence factor is the most uncertain sediment exposure parameter (U.S. EPA, 2001b). Currently, data describing sediment (as opposed to terrestrial soil) adherence to skin are limited to a single scenario involving adult gatherers of reeds (n=4) from tide flats (Kissel et al., 1996a). A second scenario involving children playing at a lakeshore could also be viewed as relevant to sediment exposure. Lack of sediment-specific adherence factors leads to the use of adherence factors derived from terrestrial soil activities in sediment contact scenarios. This practice contributes additional uncertainty since the generally higher moisture content of sediment would be expected to lead to higher skin loads (Kissel et al., 1996b).
This study was conducted to supplement available sediment adherence data. Specifically, the purpose was to determine the amount of sediment that can adhere to skin during recreational shellfishing activities. The study involved pre- and post-activity collection of sediment from multiple body parts of adult volunteers engaged in recreational clam digging. All activities were conducted in an uncontaminated tidal estuary near Narragansett, Rhode Island. Both the activity and the location were selected as relevant to Superfund/RCRA risk assessment based on the recommendations from EPA Regional Offices.

Taken from the beginning of thesis.