The U.S. Environmental Protection Agency's standards that govern using treated sewage sludge on soil are based on outdated science, says a new report from the National Academies' National Research Council (NRC).
The agency should update its standards using improved methods for assessing health risks, and should further study whether treated sewage sludge causes health problems for workers who apply it to land and for residents who live nearby, added the committee that wrote the report. More rigorous enforcement of the standards is needed as well.
"There is a serious lack of health-related information about populations exposed to treated sewage sludge," said committee chair Thomas A. Burke, professor, department of health policy and management, Johns Hopkins University Bloomberg School of Public Health, Baltimore. "To ensure public health protection, EPA should investigate allegations of adverse health effects and update the science behind its chemical and pathogen standards."
Although it called for further study of on the effect of biosolids land application, the report found that there is "no documented scientific evidence that the Part 503 rule has failed to protect public health." Industry groups focused on that finding when commenting on the report.
According to Bob Hite, chairman of the National Biosolids Partnership, "We believe the NAS biosolids report adds to a collection of studies that show there is no scientific evidence that biosolids regulations have failed to protect public health, and reflects a general agreement concerning a need to continue with scientific research on biosolids."
About 5.6 million tons of sewage sludge are used or disposed of each year in the United States, and 60 percent of that is used for land application.
Methods for assessing the health risks posed by exposure to chemicals have evolved substantially since the 1993 biosolids rule was established. In addition, EPA used an unreliable 1988 survey to identify hazardous chemicals in sewage sludge when it set the standards, and other chemicals have since been found to be of potential concern, according to the NRC report.
A new survey and revised risk assessments are needed, the committee said. The revised risk assessments also should reflect the potential for regional variations in climate, water flow, and biosolids characteristics, and should be designed to protect individuals against realistic maximum exposures.
The committee agreed with EPA's general approach for regulating pathogens, which requires the level of disease-causing microorganisms to be reduced through treatment of sewage sludge and restrictions on use of land immediately after biosolids are applied. However, the agency should use new pathogen-detection technology to ensure that treatments are reliable. Microbial risk assessments that include the possibility of secondary transmission of disease, such as through person-to-person contact or through food, air, or water, also should be developed. As is the case with chemicals, a new national survey of pathogens in sewage sludge should be carried out.
To assure the public that biosolids regulations are being followed, EPA should increase its efforts to ensure that companies producing biosolids meet the regulatory requirements to remove or neutralize chemicals and pathogens. EPA also needs to ensure that biosolids are applied in accordance with special management practices. In certain cases, biosolids can be applied with the understanding that the land cannot be used for a specified period to allow pathogens to fall below detectable levels. However, EPA has not been verifying if pathogens are dying off, whether the land is being used for agriculture or grazing, or whether public access is adequately restricted. Field data are needed in these cases, the committee said.
EPA also should conduct studies of the potential health risks, or lack thereof, to workers and residential populations exposed to biosolids. The report cites anecdotal reports linking biosolids to adverse health effects, ranging from mild allergic reactions to more severe chronic conditions, along with public concern about those reports.
The committee also cited a lack of population studies on individuals exposed to biosolids, such as farmers and nearby residents. Studies on workers exposed to raw sewage are not an adequate substitute for studies of populations exposed to biosolids in the environment, the committee concluded. More funding and staff are needed to support EPA's regulation of biosolids. Some of these resources should go toward the needed research.
The study was sponsored by the U.S. Environmental Protection Agency. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. It is a private, nonprofit institution that provides science and technology advice under a congressional charter. A committee roster follows.
The report Biosolids Applied to Land: Advancing Standards and Practices is available on the Internet at http://www.nap.edu. Copies will be available for purchase from the National Academy Press, Tel: 800-624-6242.
