Application of sewage sludge to non-agricultural ecosystems: Assessment of contaminant risks to wildlife

This report is part of a larger study evaluating nutrient and contaminant impacts associated with the land application of biosolids in four non-agricultural ecosystems: Pacific Northwest forests, semi-arid rangelands, eastern deciduous forests, and southeasternpine plantations. Because contaminants in biosolids may be taken up by biota and transferred through the food web, they may present a risk to wildlife. Biosolids application scenarios that reflect actual practices in each ecosystem were developed. Concentrations of contaminants in biosolids were obtained from the US EPA`s 1988 National Sewage Sludge Survey. Soil-biota uptake factors for contaminants in sludge were developed from contaminant studies performed in each ecosystem type. Where ecosystem-specific data were unavailable, more generalized factors were used. Endpoints were selected that reflected species expected to be present in each ecosystem. Four trophic groups were considered: herbivores (e.g., deer) vermivores (earthworm-consumers; e.g., shrews), insectivores (e.g., songbirds), and carnivores (e.g., fox). Contaminant concentrations in wildlife foods were estimated using the uptake factors. These estimates were then incorporated into models to estimate the contaminant exposure for endpoints in each trophic group in each ecosystem. Exposure estimates were then compared to NOAELs and LOAELs to determine the nature and magnitude of risks that biosolids may present to wildlife.