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Problem Formulation for Human Health Risk Assessments of Pathogens in Land-Applied Biosolids

In 2002, the National Research Council (NRC) released a report entitled: "Biosolids Applied to Land: Advancing Standards and Practices" which was a review of EPA’s regulation "The Standards for the Use or Disposal of Sewage Sludge" (otherwise known as the "Part 503 Rule" found in Title 40 of the Code of Federal Regulations published in 1993). In 2003, EPA released a final action plan for setting new priorities for the biosolids program which included the Agency’s response to the NRC report called "Standards for the Use or Disposal of Sewage Sludge; Final Agency Response to the National Research Council Report on Biosolids Applied to Land and the Results of EPA’s Review of Existing Sewage Sludge Regulations" (68 FR 75531). The problem formulation document available here on this web site represents one of many responses to the NRC 2002 report since that time.

Millions of tons of treated sewage sludge or “biosolids” are applied annually to farms, forests, rangelands, mine lands and other types of land in the United States. Biosolids are defined by the U.S. Environmental Protection Agency (EPA) as “the primarily organic solid product yielded by municipal wastewater treatment processes that can be beneficially recycled” (e.g., as an amendment to soil). Concerns about the potential human health effects from land applied biosolids can be addressed through a risk assessment. This report focuses on the systematic planning step (a “problem formulation,” which defines the major factors to be considered) in risk assessments of pathogens in land applied biosolids. The report follows the common problem formulation steps of hazard identification, conceptual model development and the development of an analysis plan. A study of peer-reviewed literature on pathogens in biosolids (including likely stressors, pathways and health responses of concern; available risk assessment data, tools and methodologies; and gaps in knowledge and research needs) forms the basis of the report. It is intended to assist anyone involved in risk assessments or the management of pathogens in biosolids (e.g., at a local level or on a case-by-case basis) and researchers advancing the science in this topic area.

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