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 toxic per- and polyfluoroalkyl substances (PFAS) chemicals in biosolids.
The EPA announced findings that claim there may be human health risks associated with exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) with all three methods of using or disposing of solids — land application of biosolids, surface disposal in landfills or incineration. Once finalized, the assessment aims to 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 risk assessment focuses on a specific and narrow population of people that 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 for people relying primarily on those sites’ products.
The preliminary findings of the draft risk assessment indicate that there can be human health risks exceeding EPA’s acceptable thresholds for some scenarios where the farmer applied biosolids containing 1 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.
EPA’s analysis does not suggest that the general food supply is impacted by the use of biosolids that contain PFOA or PFOS. The U.S. Department of Agriculture and Food and Drug Administration are monitoring for PFAS in the food supply broadly and have taken protective actions to address impacted products from domestic and imported sources, according to the EPA. Based on the best available data, biosolids account for less than 1% of the fertilized acreage of productive agricultural land in the United States per year. The EPA says it recognizes that certain hot spots and specific farming operations may have higher levels of PFOA or PFOS if contaminated biosolids were applied, and that further collaboration with impacted operations and other federal agencies will be important to fully understand risks and support impacted farmers.
The EPA’s draft risk assessment document, Draft Sewage Sludge Risk Assessment for Perfluorooctanoic Acid and Perfluorooctane Sulfonic Acid, will be available for public comment for 60 days following announcement in the Federal Register. Also read about other recent EPA actions to help address PFAS in Biosolids.
