Lawmakers Ask GAO to Review EPA’s Microplastics Research and Regulatory Efforts

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Following EPA’s decision not to list microplastics in the proposed Sixth Unregulated Contaminant Monitoring Rule (UCMR 6), two dozen Democratic lawmakers are asking the Government Accountability Office (GAO) to review the Agency’s efforts to assess human exposure to micro- and nanoplastics and their associated risks.

“Congress lacks a clear assessment of what the EPA has accomplished in its work on microplastics and what work remains necessary to support reliable monitoring, risk assessment and potential regulatory action,” the letter, dated September 28, 2026, states.

The letter cites EPA plans to evaluate and address microplastic pollution, including EPA’s Safe and Sustainable Water Resources (SSWR) Strategic Research Action Plan for fiscal years 2023-2026 and its 2024 National Strategy to Prevent Plastic Pollution. According to the letter, those initiatives outlined plans to assess the effects of microplastics on human health and aquatic life, develop government-wide definitions, and standardize methods for quantifying microplastics. However, the lawmakers note uncertainty over the extent to which EPA has achieved these objectives.

The letter also challenges EPA’s exclusion of microplastics from the proposed UCMR 6, which the Agency justified by the lack of a validated analytical method for quantifying microplastics. The lawmakers note that EPA reported two years ago that it was in the early stages of developing such a method.

“Notably, the EPA has not scientifically justified, or even stated, that microplastics are less of a public health threat than any of the 30 other contaminants they included on the draft UCMR,” which is required by law, it adds.

The letter is led by Reps. Janelle Bynum (D-OR), Raja Krishnamoorthi (D-IL), and Watson Coleman (D-NJ). Sen. Merkley (D-OR) is the only senator among the signatories.

Questions for GAO

The letter outlines three questions for GAO to investigate.

First, it asks what microplastic- and nanoplastic-related activities the EPA has undertaken since fiscal year 2023. The request covers research, analytical method development, monitoring, risk assessment, pollution prevention, development and evaluation of capture and removal technologies, grant programs, and regulatory and other policy activities.

Second, it asks the extent to which EPA implemented the microplastics-related goals, outputs, and actions identified in the SSWR plan and 2024 National Strategy to Prevent Plastic Pollution. Specifically, the letter asks GAO to examine:

  • EPA’s progress towards developing government-wide definitions and validated, fit-for-purpose methods for collecting, extracting, identifying, quantifying, and characterizing microplastics and nanoplastics;
  • Research conducted or supported by EPA on the prevalence, sources, pathways, fate, and concentrations of microplastics and nanoplastics, and resulting findings;
  • EPA research on the toxicity of micro- and nanoplastics in human and aquatic life and resulting findings;
  • Methods, models, and tools developed or investigated by EPA to evaluate the effects of microplastics and nanoplastics on human health and aquatic resources and resulting findings;
  • EPA’s progress in developing testing, demonstrating, deploying, or funding management practices and technologies to prevent, capture, or remove microplastics and nanoplastics from the environment. This includes interventions to support these technologies and evaluations on the use of relevant water programs to address plastic pollution in waterways and oceans;
  • EPA’s implementation of policy and program opportunities identified in the national strategy, including evaluating the use of Clean Water Act (CWA) authorities and providing technical assistance to incorporate plastic pollution prevention, capture, and removal measures into relevant management plans.

Third, it asks what statutory, financial, workforce, technological, or infrastructure constraints affect EPA’s ability to advance its work of researching and regulating microplastics.

More information on EPA’s microplastics research can be found on EPA’s website.