The U.S. Environmental Protection Agency’s (EPA) Science Advisory Board (SAB) Biosolids Panel had it first meeting on April 5th to kick off its review of EPA’s “Approach to Biosolids Chemical Risk Assessment and Biosolids Tool.”  Details of the meeting are available here.  This Biosolids Panel is charged with providing feedback to EPA on a proposed framework for biosolids risk assessment.

There are over 700 chemicals that have been detected in biosolids based on sewage sludge and literature surveys (see past NEBRA news article on the subject: EPA Publishes Curated List — NEBRA (nebiosolids.org)). With so many chemicals to evaluate, EPA has proposed the following three-step process:

STEP 1. Prioritize the risk assessment of chemical pollutants found in biosolids using the EPA’s Public Information Curation and Synthesis (PICS) process. This approach was developed to meet EPA’s requirement to determine if chemical substances present an unreasonable risk of injury to human health and the environment under Toxic Substances Control Act (TSCA) and is being customized to target the Biosolids program needs.

STEP 2. Use BioSolidsTool (BST) to conduct screening-level risk assessments on chemicals prioritized in Step 1.

STEP 3. Conduct refined risk assessments for chemicals that pose the greatest risk as identified in Step 2.

EPA’s Richard Judson, PhD, presented details on the PICS process (Step 1) and Dr. David Tobias, EPA’s Lead Risk Assessor, and head of the Biosolids Program, presented details on screening level and refined risk assessments (Step 2 and Step 3). Their presentations, a white paper on the approach, the BST, and charge questions are available on the meeting website as well.

A few key takeaways:

  • PICS process assesses what is in the scientific domain and is available – reviewing US EPA, CalEPA, and European peer reviewed toxicity values.

  • Screening level risk assessment uses conservative model scenarios (similar to Massachusetts Department of Environmental Protection’s Massachusetts Contingency Plan (MCP) lookup tables).

  • Refined risk assessment will use a probabilistic approach (similar to MassDEP’s MCP Method 3 Risk Assessment).

Prior to the April 5th meeting, some were voicing concern about the EPA’s approach to risk assessment for biosolids, like the National Association of Clean Water Agencies (NACWA) which represents wastewater utilities.  According to Inside EPA, NACWA is worried about the appropriateness of the framework itself “in light of existing significant data gaps and gaps that may emerge during the risk assessment process.” NACWA expressed concerns about applying the proposed framework to PFAS, microplastics and other contaminants of emerging concern. Most importantly, NACWA is asking the panel to look at background levels of contaminants as part of the framework.

The EPA’s draft framework has been under development for several years. It is being used already to assess the risks from PFOA and PFOS.

SAB panelists had to submit their preliminary comments April 12th and will meet again, in person on May 2nd and 3rd. Those meetings are expected to be public.

The SAB Biosolids panel is just the first step in the process of regulating PFAS and other CECs in biosolids.  Once the review is completed, the EPA will start the actual risk assessment process for contaminants in biosolids. Following the results of the risk assessment work, EPA will begin the process of developing limits and/or requirements for best management practices which is still years away. In the meantime, NEBRA and others will be watching the process and taking every opportunity to engage in the discussions.