Biosolids are treated waste solids generated from sewage sludge that have been processed so that they can be applied to land as a fertilizer. Advocates of biosolid use point to its ability to enrich soil without the use of synthetic fertilizers.
Biosolids have long been regulated by the Environmental Protection Agency (EPA) and state regulatory authorities due to concerns of odor, attraction of vermin, and potential contaminants. However, as concern surrounding PFAS contamination has emerged, the regulatory landscape has become increasingly fragmented and uncertain.
At the federal level, the EPA issued a Draft Risk Assessment for PFOA and PFOS in biosolids in January 2025, prior to the Trump administration taking office. This Draft Risk Assessment received over 25,000 public comments and is being re-evaluated by EPA. If a final version is published, it will likely inform federal regulatory action.
It is difficult to predict the future of federal regulation of PFAS in biosolids. In the meantime, states are stepping in to create a patchwork of regulation across the country.
Some states are developing outright bans on the application of biosolids. Maine is at the far end of this spectrum, banning land application of biosolids entirely. Connecticut prohibits use of biosolids that contain PFAS. Michigan has established numeric thresholds, banning application of biosolids that exceed a certain concentration of PFAS and restricting their use at slightly lower concentrations.
Other states—such as California, Washington, and Vermont—have established sampling and reporting requirements. Some states have not established rules but have indicated that they retain the authority to require testing for PFAS on a case-by-case basis. Still others are evaluating whether to regulate PFAS in biosolids.
States are also using a variety of mechanisms to implement their testing and reporting requirements. Washington’s state legislature passed legislation directing the Washington State Department of Ecology to develop guidance. Other vehicles for imposing these requirements are through permits themselves (either for publicly owned treatment works or for biosolids generators) or by embedding the requirements in regulations.
Both in form and substance, states are taking a variety of approaches to monitoring and limiting PFAS in biosolids applied to land across the country. More states will likely follow, and federal regulation may be forthcoming.
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