Biosolids Applied to Land Advancing Standards and Practices (2002) / Chapter Skim
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The Part 503 rule established management practices for land application of sewage sludge, concentration limits and loading rates for chemicals, and treatment and use requirements
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Thus, the chemical limits for biosolids can be achieved easily. In contrast to the chemical standards, the pathogen standards are not risk-based concentration limits for individual pathogens but are technologically based requirements aimed at reducing the presence of pathogens and potential exposures to them by treatment or a combination of treatment and use restrictions.
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In responding to its charge, the committee searched for evidence on human health effects related to biosolids exposure, reviewed the risk assessments and technical data used by EPA to establish the chemical and pathogen standards, and reviewed the management practices of the Part 503 rule. The committee did not attempt to determine whether the approaches used by EPA to set the 1993 biosolids standards were appropriate at the time of their development, and the committee's findings and recommendations should not be construed as either criticism or approval of the standards issued at that time.
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new risk assessments should be conducted to update the scientific basis of the chemical limits, and (23 risk assessments should be used to supplement technological approaches to establishing regulatory criteria for pathogens in biosolids. · Conduct a new national survey of chemicals and pathogens in sewage sludge.
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Because of the anecdotal reports of adverse health effects, the public concerns, and the lack of epidemiolog~cal investigation, the committee concluded that EPA should conduct studies that examine exposure and potential health risks to worker and residential populations. Studies of wastewater treatment workers exposed to raw sewage sludge should not be used as substitutes for studies of populations exposed to biosolids.
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Therefore, although the land application of biosolids has occurred for many years with little, if any, systematic documented evidence of adverse effects, there is a need to gather epidemiological data and to investigate allegations of health incidents. EPA needs to study more rigorously the exposure and health risks, or the lack thereof, in worker and community populations exposed to biosolids.
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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 expectanon that the prescribed biosolids-management practices specified in the Part 503 rule would be effective in preventing harmful exposure to biosolids constituents.
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8 Biosoli~pplied~o~znd Advancing Standar~andIPractices Environmental Human Exposure Hazard Surveillance Raw Sewage Study Opportunities Slur dge Opportunities ~ t ~ , Quality Control ~ Processing 1 . Compliance Audits Compliance Audits Class A/B 1 Packaging and Transport Potential Exposure CIassA/B ~ 1_ I I Exposure I Land Application ~ Class A/B ; ~ I Exposure I 1 Environmental Transport Off-site contaminants I Exposure I 1 FIGURE S-1 Processing, transport, and land application of biosolids with options for hazard surveillance and studies of human exposures.
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There have been substantial improvements in conducting risk assessments since the Part 503 rule was promulgated, and guidance for using these improved methods to update and strengthen the scientific basis of the chemical and pathogen standards is provided below.
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Other important developments in risk assessment in recent years include improvements in measuring and predicting adverse health effects, advancements in measuring and predicting exposure, explicit treatment of uncertainty and variability, and improvements in describing and communicating risk. In developingits 1993 chemical standards, EPA selected chemicals, exposure conditions, and risk-assessment assumptions that were intended to be representative and conservative enough to be applicable to all regions of the United States and to all land-application sites, including agricultural fields, forests, and reclamation sites.
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Improvements in industrial wastewater pretreatment processes and changes in chemical uses have occurred over the past decade. Chemicals not included in the NSSS analyses have since been identified as potential concerns, and data gaps on toxicity and fate and transport characteristics that prevented risk assessment from being performed on some chemicals a decade ago might now be filled.
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Because the land-application standards are to be relevant nationally, it is important that the revised risk assessments reflect regional variations in climate, hydrology, and biosolids use and characteristics, and that standards are protective of populations reflecting reasonable estimates of maximum exposure. The chemical standards should be reevaluated and updated periodically to ensure that they are supported by the best available scientific data and methods.
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Class A biosolids have pathogen densities below specified detection limits, whereas Class B biosolids have pathogen densities above those limits. No risk assessments were conducted to establish the 1993 pathogen standards for these classes.
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As with the chemical standards, EPA based its 1993 pathogen standards on selected pathogens and exposure conditions that were expected to be representative and conservative enough to be applicable to all areas of the United States and all types of land applications. This includes the recognition that pathogen survival in soils can range from hours to years, depending on the specific pathogens, biosolids application methods and rates, initial patho.
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-- of ~rFindings: Given the variety of pathogens that have the potential to be present in biosolids, the committee supports EPA's approach to establishing pathogen reduction requirements and monitoring indicator organisms. However, the reliability of EPA's prescribed treatment techniques should be better documented using current pathogen detection technology, and more research on environmental persistence and dose-response relationships is needed to verify that current management controls for pathogens are adequate to maintain minimal exposure concentrations over an extended period of time.
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· EPA should foster development of standardized methods for measuring pathogens in biosolids and bioaerosols. · EPA should promote research that uses improved pathogen detection technology to better establish the reliability of its prescribed pathogen treatment processes and biosolids-use controls to achieve and maintain minimal exposure over time.
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