Evaluating perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) levels in U.S biosolids is a key part of a new Environmental Protection Agency (EPA) assessment that considers risk to human health from the “forever chemicals”.
The findings for the January 2025 draft risk assessment show that there may be human health risks associated with exposure to PFOA or PFOS for all three methods of using or disposing of what is often referred to as sewage sludge: land application of biosolids, surface disposal in landfills, or incineration.
In 2024, the EPA classified PFOA and PFOS as “likely to be carcinogenic” and linked to hepatic (liver), immunological, cardiovascular, and developmental effects, depending on exposure conditions; however, the agency has not regulated the chemicals in sewage sludge.
Once finalized, the risk assessment can help the agency determine whether regulating PFOA and PFOS in sewage sludge under the Clean Water Act is appropriate. The agency currently regulates certain heavy metals and pathogens in sewage sludge used as fertilizer, but not PFAS.
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The EPA’s draft risk assessment scientifically models hypothetical human health risks for people living on or near sites impacted by PFOA or PFOS, or for people relying primarily on those sites’ products, such as food crops, animal products or drinking water.
“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),” stated an EPA announcement accompanying the risk assessment.
The EPA’s modelled 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 modelling also found 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.
“The findings of the draft risk assessment underscore the importance of proactive federal and state policies to control and remove PFAS at their source,” the EPA announcement continued.
Public comments on the draft risk assessment can be made over the next two months.
In Canada, enforcement of an interim standard for PFAS in biosolids used as a commercial fertilizer product started in October 2024 to ensure they contain less than 50 ppb of PFOS as an indicator for PFAS chemicals.
According to the Canadian Food Inspection Agency (CFIA), 100% of all products inspected since that time have been compliant. A spokesperson for the agency told Environmental Science & Engineering Magazine that when a facility confirms they are selling biosolids for use as fertilizer, the CFIA requests a copy of their PFAS certificate of analysis to verify compliance. It must be no older than six months.
“On the domestic front, CFIA inspectors are actively engaged in contacting all wastewater treatment facilities in Canada to verify whether or not the biosolids they produce are used as commercial fertilizers in Canada (other possible endpoints include landfilling and incineration),” said a CFIA spokesperson.
PFOS has been manufactured globally for more than 50 years but never in Canada. PFOA is banned in both the U.S. and Canada, however, multiple historic and ongoing activities still result in PFOA, PFOS, and their precursors being released to wastewater treatment plants, according to the EPA.
Traditional wastewater treatment technology does not remove or destroy PFOA or PFOS, and these chemicals accumulate in the sewage sludge.
For more information, read this article from Environment and Climate Change Canada on PFAS in municipal wastewater treatment systems from ES&E Magazine’s February 2024 issue.
