CASA Submits Public Comments On EPA’s Biosolids Draft Risk Assessment
On August 14, the U.S. Environmental Protection Agency’s (USEPA) public comment period on its pending Draft Sewage Sludge Risk Assessment Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS) (Draft Risk Assessment) ended. The Draft Risk Assessment outlines the Agency’s most up-to-date scientific understanding of the human health and environmental risks posed by the chemicals when present in sewage sludge (biosolids) and the sludge is land-applied or incinerated. Now that the public comment period has closed, USEPA will review and consider the submitted public comments. Per the federal rulemaking process, once USEPA completes its review of the public comments, it will publish a final risk assessment. The Agency has not indicated when or if a final risk assessment will be published. Prior to the August 14 deadline, CASA submitted two public comments to the Agency on the Draft Risk Assessment.

CASA March 28, 2025 Public Comment
CASA August 11, 2025 Public Comment

In the public comments, CASA emphasizes that due to the scientific methods and data used to develop the Draft Risk Assessment, it risks increasing uncertainty and confusion surrounding PFAS chemicals and their presence in sewage sludge. As a result, CASA explains, this will unnecessarily jeopardize public safety and the environment. Accompanying CASA’s first letter, an Expert Review from Research Scientists was also included to underscore points highlighted in comment letter. In the public comments, CASA recommends the Agency not finalize the current pending Draft Risk Assessment and instead reconduct the Risk Assessment to incorporate the risk management component, source recent research using typical biosolids and realistic land application scenarios, and address PFAS contamination in biosolids in a more realistic and practical approach. Below is an overview of CASA’s submitted comments, which can be read in full using the hyperlinks above.

Overview of CASA’s March 2025 Public Comment Letter

  • The Draft Risk Assessment fails to include essential risk management component. – USEPA released the Draft Risk Assessment without first conducting a risk assessment analysis, which is critical for accurately detailing the actual risk posed by biosolids in perspective compared to exposure risks from other PFOS and PFOA.
  • The Draft Risk Assessment fails to acknowledge limited biosolids management options. – The draft assessment fails to mention the practical reality of limited biosolids management options and the impacts this will impose on wastewater agencies.
  • The Draft Risk Assessment paints unrealistic scenario surrounding land application. – Examples used in the assessment are problematic based upon findings of peer-reviewed scientific research and need to be improved in any final risk assessment.

Overview of CASA’s August 2025 Public Comment Letter

  • Reference intake of pollutants. – The Draft Risk Assessment deviates from previous practice and establish protocols for development and use of adjusted reference intake of pollutants. As a result, calculations presented in the Draft are flawed and need to be corrected in any final assessment.
  • Reference Dose and Cancer Slope. – The Draft Risk Assessment’s reference dose and cancer slope drive the assessment’s overall ultra-conservative values and, are contradictory of international dose and slop values. This results in an unrealistic and non-credible risk assessment of biosolids land application outlined in the Draft Risk Assessment.
  • Technology advancement and resource recovery. – While the Agency acknowledges the scalability and cost challenges to deploying new technologies to respond to PFAS destruction, CASA recommends that the Agency conduct a risk-benefit analysis on the revised Draft Risk Assessment before it is finalized. The analysis should consider the loss of carbon, micro- and macro-nutrients, and climate mitigation benefits of biosolids land application in contrast with destruction and disposal technologies.