In February 1993, the U.S. Environmental Protection Agency (EPA) published the Standards for the Use or Disposal of Sewage Sludge (40 CFR Part 503). This regulation lists management practices and pollutant limits that protect public health and the environment from the reasonably anticipated adverse effects of pollutants in municipal biosolids (formerly referred to as 'sewage sludge') when the biosolids are land-applied, placed on a surface disposal site, or fired in a biosolids incinerator. The Part 503 rule published in February 1993 is known as the Round One biosolids regulation. Section 405 of the Clean Water Act (CWA) requires EPA to publish a Round Two biosolids regulation, which will contain limits for pollutants not regulated in Round One. Pollutants considered but not regulated under Round One were again considered under Round Two for potential regulation. Subsequently, EPA conducted preliminary exposure analyses in a Comprehensive Hazard Identification exercise to determine which of the 31 pollutants should be on the final pollutant list for potential regulation under Round Two (U.S. EPA, 1996). Based on the results of those analyses, three groups of pollutants were placed on the pollutant list for Round Two: polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs). This document describes the risk assessment conducted to determine the concentrations of polychlorinated-p-dioxins, dibenzofurans, and coplanar polychlorinated biphenyls that can be present in biosolids and remain 'protective' (below a specified level of risk) of human health. This risk-based concentration limit was generated by evaluating cancer risks for individuals (receptors) who may be exposed to these constituents if biosolids are applied to agricultural fields.