EPA Studies Toxic Chemicals in Poop Fertilizer Spread on Farms
Published Date: 1/15/2025
Notice
Summary
The EPA just dropped a draft report about the risks of two chemicals, PFOA and PFOS, found in sewage sludge used on farms and forests. This affects farmers, nearby communities, and anyone who eats local food or drinks local water. You’ve got until March 17, 2025, to share your thoughts before the EPA decides on possible new rules that could change how sludge is handled—and maybe impact costs down the road.
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Analyzed Economic Effects
6 provisions identified: 2 benefits, 4 costs, 0 mixed.
Land‑applied sludge can exceed safety thresholds
The EPA's draft risk assessment found that when sewage sludge contains 1 part per billion (ppb) of PFOA or PFOS, some land‑application scenarios (for farms or reclamation) produce modeled human health risks above the agency's acceptable thresholds. The draft shows examples where modeled cancer risks from drinking contaminated milk can exceed 1 in 1,000 and non‑cancer hazard quotients (HQs) for eating fish can reach up to 45 under the modeled conditions.
Surface disposal can contaminate drinking water
The EPA modeled drinking‑water risks near surface disposal sites and found exceedances for unlined and clay‑lined sites. For unlined sites, risks exceeded EPA thresholds when sewage sludge contained 1 ppb of PFOA (cancer risk >1 in 1,000 and HQs up to 12); for clay‑lined sites similar exceedances occurred and HQs were up to 9. Composite‑lined sites did not show exceedances in the draft modeling.
Common application rates produced risk exceedances
The draft assessment modeled a single application at 50 dry metric tons (dmt) per hectare (reclamation scenario) and 40 annual applications at 10 dmt per hectare (median U.S. application rate for pasture and food crop scenarios) with sludge at 1 ppb of PFOA/PFOS, and found those modeled scenarios produced risk exceedances for multiple exposure pathways (drinking water, milk, beef, eggs, some fruits and vegetables).
Monitoring and pretreatment can cut sludge PFAS by 98%
The EPA recommends that states, Tribes, and wastewater treatment plants (WWTPs) monitor sewage sludge for PFAS, identify industrial discharges, and implement industrial pretreatment requirements where appropriate. The notice says some state programs achieved a 98 percent reduction in PFOS concentrations in sewage sludge through pretreatment.
EPA may propose rules and studies to limit PFAS
After considering public comments, the EPA says it will finalize the risk assessment and, if risks above acceptable thresholds are indicated, expects to propose a regulation under Clean Water Act section 405 to manage PFOA and/or PFOS in sewage sludge. The EPA also plans a new National Sewage Sludge Survey and a POTW Influent PFAS Study and is evaluating revisions to Effluent Limitations Guidelines for Organic Chemicals, Metal Finishing, and Landfills.
Incineration risks are uncertain and not quantified
The draft assessment did not provide quantitative risk estimates for sewage sludge incineration because of data gaps about how well incinerators destroy PFOA and PFOS and the health effects of products of incomplete combustion. The EPA notes incinerators may not reach temperatures and residence times needed to fully destroy these chemicals.
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