logical study would be an evaluation of health effects in a cohort of biosolids appliers. These workers should be characterized by duration and level of exposure, and given appropriate follow-up. Because complete epidemiological studies are expensive and require extensive data analysis, priority should be given to studies that can address serious or widespread problems and help reduce uncertainty.

Chemical and Pathogen Standards

EPA’s 1993 chemical and pathogen standards for biosolids were based on the scientific and technical information available at that time and the expectation that the prescribed biosolids-management practices specified in the Part 503 rule would be effective in preventing harmful exposure to biosolids constituents. To assure the public that the standards are protective of human health, it is important that EPA demonstrate that its chemical limits and pathogen-reduction requirements are supported by current scientific data and risk-assessment methods. Management practices (e.g., 10-meter setback from water bodies) are designed to control the potential risks; therefore, it is important to verify the effectiveness of the practices. In addition, EPA must demonstrate that the Part 503 rule is being enforced.

Findings: The committee found that no substantial reassessment has been done to determine whether the chemical or pathogen standards promulgated in 1993 are supported by current scientific data and risk-assessment methods. In addition, EPA does not have an adequate program to ensure compliance with the biosolids regulations and has not documented the effectiveness of its prescribed management practices. Although there is no documented scientific evidence that the Part 503 rule has failed to protect public health, there is a need to address scientific and management questions and uncertainties that challenge EPA’s biosolids standards.

Recommendations: EPA should expand its biosolids oversight activities to include procedures for (1) assessing the reliability of the biosolids treatment processes, (2) monitoring compliance with the chemical and pathogen standards, (3) conducting environmental hazard surveillance, and (4) studying human exposure and health. The committee recommends that Figure S-1 be used by EPA as a framework for establishing such a program. The central part of the figure presents the general process by which biosolids are produced and used for land application. Depicted on the left side of the figure are opportunities for conducting environmental hazard surveillance. At these



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