40 CFR Part 503 was developed as a comprehensive risk-based rule to protect the public health and the environment from reasonably anticipated adverse effects of pollutants that may be present in biosolids (sewage sludge). This guide provides an understanding of the multi-pathway risk assessment that was used for evaluating and setting limits to manage pollutants in biosolids. 

• A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule (PDF)(158 pp, 21 MB, September 1995, EPA 832-B-93-005)