EPA draft risk assessment advances understanding of PFOA and PFOS

The U.S. Environmental Protection Agency has released a draft risk assessment, or scientific evaluation, of the potential human health risks associated with the presence of per- and polyfluoroalkyl substances (PFAS) in biosolids, also known as sewage sludge.

The draft risk assessment's findings show that human health risks may be associated with exposure to the “forever chemicals” PFOA or PFOS in 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 reduce the risk of exposure.

“EPA under [former] President Biden’s leadership has taken unprecedented actions to advance research and science on PFAS and to protect people from these dangerous forever chemicals,” EPA Acting Administrator Jane Nishida says. “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.” 

This draft risk assessment focuses on a specific and narrow population of people that the EPA considers most likely to be exposed to PFOA or PFOS from the land application of biosolids or through consumption of products from land where biosolids were used as fertilizer. The draft risk assessment scientifically models hypothetical human health risks for people living on or near sites impacted by PFOA or PFOS or relying primarily on those sites’ products (e.g., food crops, animal products or drinking water). 

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The preliminary findings of the draft risk assessment indicate that there can be human health risks exceeding EPA’s acceptable thresholds, sometimes by several orders of magnitude, for some scenarios where the farmer applied biosolids containing 1 part per billion (ppb) of PFOA or PFOS (which is near the current detection limit for these PFAS in biosolids). These modeled scenarios include farms with one application of biosolids at a rate of 10 dry metric tons per hectare and 40 consecutive years of biosolids land application at this same rate.

The modeling in this assessment also finds human health risks exceeding the EPA’s acceptable thresholds in some scenarios where biosolids containing 1 ppb of PFOA or PFOS are placed in an unlined or clay-lined surface disposal unit. 

Once finalized, the EPA will use the risk assessment to help inform future risk management actions for PFOA and PFOS in sewage sludge. Due to significant data gaps, risk is not quantified for the incineration scenario.

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.