The U.S. Environmental Protection Agency released on January 14 a draft risk assessment, or scientific evaluation, of the potential human health risks associated with the presence of toxic per- and polyfluoroalkyl substances (PFAS) chemicals in biosolids, also known as sewage sludge.
The findings for the draft risk assessment show there may be human health risks associated with exposure to PFOA or PFOS with all three methods of using or disposing of sewage sludge — land application of biosolids, surface disposal in landfills, or incineration.
Once finalized, the assessment will help the EPA and its partners understand the public health impact of forever chemicals in biosolids and inform any potential future actions to help reduce the risk of exposure.
“This draft assessment provides important information to help inform future actions by federal and state agencies as well as steps that wastewater systems, farmers and other stakeholders can take to protect people from PFAS exposure, while ensuring American industry keeps feeding and fueling our nation,” said EPA Acting Administrator Jane Nishida.
Groundwater is mentioned 388 times in the report. An entire appendix is devoted to groundwater modeling for the risk assessment. Once the notice is published in the Federal Register, comments on the draft risk assessment will be accepted for 60 days.
The draft report highlights significant impacts of PFOA and PFOS (on groundwater, primarily through their persistence, bioaccumulation, and potential for leaching.
Other key points:
Leaching into groundwater: The report mentions that surface disposal of sewage sludge containing PFOA or PFOS as particularly concerning for unlined or clay-lined disposal sites, where leachate can more easily infiltrate into groundwater supplies.
Detection in groundwater: PFOA and PFOS have been consistently detected in groundwater near areas where contaminated sewage sludge was applied or disposed of. Even low concentrations in sewage sludge (1 ppb for PFOA and 4-5 ppb for PFOS) can exceed the EPA's acceptable human health risk thresholds for groundwater contamination.
Risk scenarios: Modeling scenarios indicate that individuals relying on groundwater near contaminated sites have a potential for adverse health impacts. Risk factors include the concentration of contaminants, the design and management of disposal sites, and local hydrogeologic conditions.
Health implications: Drinking water with these chemicals is a direct risk to human health, with concerns of developmental, immune, and other systemic health effects.
Highlighted in the report is a focus on stricter management and monitoring of sewage sludge disposal practices contributing to risks of groundwater contamination from PFOA and PFOS.
Groundwater modeling used in farming and reclamation scenarios was also applied to understand how PFOA and PFOS move through groundwater to neighboring groundwater wells.
The EPA’s National Primary Drinking Water Regulation for PFAS (April 26, 2024; 89 FR 32532) estimates that 6 to 10 percent of all public drinking water systems in the United States contain detectable amounts of PFOA and PFOS but the prevalence of PFOA and PFOS contamination in private groundwater wells is not known.
The EPA’s draft risk assessment document, Draft Sewage Sludge Risk Assessment for Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS), will be available for public comment for 60 days following announcement in the Federal Register. Click here to learn more about the draft risk assessment and how to comment on it. Also read about other recent EPA actions to help address PFAS in Biosolids.