On January 14, 2025 the U.S. Environmental Protection Agency released the Draft Sewage Sludge Risk Assessment for PFOA and PFOS for public comment. BC’s top experts in emerging regulations for biosolids and emerging contaminants share their top 10 conclusions for the water and wastewater industry to help tackle what’s emerging.
1.The draft risk assessment is not a regulation or a rule. There are no enforceable screening levels or limits recommended. EPA states that the risk assessment likely will form the basis of new regulations in the coming years. Other factors, such as economic impacts and feasibility of treatment, may also inform regulations.
2. The risks estimated only apply to highly exposed populations living on or near impacted sites, not the general population.
3. While the draft risk assessment identified high-risk food products (primarily milk, fish and drinking water), these findings do not apply to the food supply at large. In a webinar conducted on January 15, 2025, EPA noted that FDA has been monitoring the general food supply for PFAS with no significant detections.
4. The draft risk assessment assumes concentrations of two of the more prevalent PFAS (PFOS and PFOA) of one part per billion (ppb). Few biosolids, including those from wastewater treatment plants without significant industrial impacts, would currently consistently have concentrations below this level. In fact, the PFAS concentrations modelled are lower than PFAS concentrations seen both in background (e.g. non-impacted) soils as well as other commonly used soil amendments (e.g. food waste compost, yard waste composts, and some fertilizers).
5. With the assumptions used in the risk assessment, most human health risks exceed EPA’s acceptable thresholds in farm scenarios. The associated risk-based concentrations derived using EPA’s inputs would in some cases be below 1 part per trillion in source biosolids. It is not inconceivable that agencies could use the lowest risk-based concentrations to establish thresholds to protect the most impacted populations.
6. The transport and exposure modeling used in this risk assessment are very complex and results are difficult to predict accurately. As reflected in current research, the fate and transport of PFAS in the environment is highly dependent on site-specific factors including biosolids type, soil characteristics, climate, and others.
7. The findings indicated that all biosolids management scenarios considered (land application, landfill, and incineration) pose some risk – there is no ideal management scenario identified by EPA for PFAS in biosolids.
8. Landfilling was modeled as groundwater impacts from a sludge monofill—i.e., landfill only receiving municipal sludge. The more common practice nationally of disposing of sludge in a municipal solid waste (MSW) landfill was not quantitatively assessed. EPA modeling found potential human health impacts only at monofills without modern liners.
9. The EPA stressed the importance that source control can play in reducing the amount of PFAS in the environment.
10. Risk and the underlying concepts of the risk assessment are not intuitive and can be challenging to communicate.
If your utility would like to talk about how to adapt to what’s emerging by further discussing the methods and findings of EPA’s Draft Sewage Sludge Risk Assessment for PFOA and PFOS, please contact BC’s solids and PFAS experts using the form below.