Lawmakers Ask GAO to Review EPA's Microplastics Work After Monitoring Rule Leaves Them Out

Twenty-four members of Congress have asked the Government Accountability Office (GAO) to review the Environmental Protection Agency's work on micro- and nanoplastics. The September 28, 2026 letter was led by Representatives Raja Krishnamoorthi (D-IL), Janelle Bynum (D-OR) and Bonnie Watson Coleman (D-NJ), and was also signed by Senator Jeff Merkley (D-OR).

The lawmakers write that "even as the EPA's FY2023-FY2026 research plan approaches its conclusion, 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."

Why now: microplastics left off UCMR 6

In April 2026, EPA added microplastics to the draft of its sixth Contaminant Candidate List (CCL 6), the list of contaminants that may need future drinking-water regulation. But EPA's proposed sixth Unregulated Contaminant Monitoring Rule (UCMR 6), published in July 2026, did not include microplastics among the 30 contaminants public water systems would be required to monitor.

That was despite a petition from the governors of seven states nominating microplastics for UCMR 6. In the proposed rule, EPA said no validated drinking-water analytical method for microplastics is available yet and that developing one before the statutory deadline was infeasible. The letter argues EPA did not explain why microplastics are a lower public-health priority than the 30 contaminants it did include, and notes that in 2024 EPA said it was "in the early stages of developing a microplastics method."

What the lawmakers want GAO to look at

• What micro- and nanoplastics work EPA has done since fiscal year 2023, including research, method development, monitoring, risk assessment, removal technologies, grants and policy, with timelines and funding.
• How far EPA has gotten on the microplastics goals in its FY2023–2026 water research plan and its 2024 National Strategy to Prevent Plastic Pollution, including validated methods for measuring micro- and nanoplastics.
• What statutory, financial, workforce, technological or infrastructure limits affect EPA's ability to research and regulate microplastics.

What it means for readers

This is a request for an accounting, not a new rule. It does not set a drinking-water standard or require any water system to test for microplastics, and GAO has not issued any findings from it. EPA's final UCMR 6 will decide what the next national monitoring cycle covers. Until a validated method is in place, most people have little public data on microplastics in their own tap water.

A note on scope: this post summarises a congressional letter and EPA's proposed rule. It is not medical advice or a health-risk finding.

Sources

• Letter from Rep. Raja Krishnamoorthi et al. to Acting Comptroller General Orice W. Brown, U.S. GAO (Sep 28, 2026). Read the letter (PDF)
• U.S. EPA, "Revisions To Establish the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems," proposed rule, Federal Register (Jul 1, 2026). Read the proposed rule

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