Microplastics are on the Environmental Protection Agency’s list of potential drinking water concerns, but they are absent from the agency’s proposed nationwide testing rule. That gap has prompted Rep. Janelle Bynum of Oregon and 23 other House members to seek an independent review of EPA’s research and its ability to measure the particles in water.
Bynum joined Reps. Raja Krishnamoorthi of Illinois and Bonnie Watson Coleman of New Jersey in leading a September 28 request to the Government Accountability Office. The members asked GAO to examine EPA research, monitoring methods, risk assessments and policies concerning microplastics and nanoplastics since fiscal year 2023.
The request does not establish a drinking water standard, require utilities to collect samples or identify contamination in Oregon. It asks GAO, which conducts reviews for Congress, to account for the federal work completed so far and identify what remains unresolved. No findings from the requested review have been issued.
EPA placed microplastics on its draft sixth Contaminant Candidate List in April. That list identifies substances that may warrant future drinking water regulation. In July, the agency proposed its sixth Unregulated Contaminant Monitoring Rule, calling for public water systems to test for 30 specified chemicals between 2028 and 2030. Microplastics were not among them.
The difference has a practical effect. The candidate list can guide research and future regulatory decisions, but it does not require a water utility to test for a substance. The monitoring rule would collect results from public water systems across the country. Unless EPA changes the proposed rule, its next testing cycle will not produce a comparable nationwide set of microplastics results from those systems.
Under the proposal, all community water systems and qualifying systems serving places such as schools or workplaces with more than 10,000 people would participate. Systems serving 3,300 to 10,000 people would also test, along with a sample of smaller systems, if federal funding and laboratory capacity are sufficient. Each participating system would collect samples during a 12-month period between 2028 and 2030. Larger systems would pay their analytical costs, while EPA would cover those costs for participating systems serving 10,000 people or fewer.
In Southern Oregon, the federal proposal is relevant to public water providers of different sizes across Jackson and Josephine counties. As written, it would not require a participating provider to measure microplastics through that program. It also would not require testing at every private household well, which falls outside the public water system monitoring rule.
The omission leaves a question for residents who want to know whether microplastics are present in their own drinking water. It does not establish that water supplied in Grants Pass, Medford or any other Southern Oregon community contains unsafe levels. The congressional request, EPA proposal and Oregon state materials reviewed for this story do not provide verified microplastics measurements for those city supplies. A finding about a particular source would require samples from that source and a clear account of how they were analyzed.
Developing a dependable method is one of the issues behind the request to GAO. Microplastics include fragments and fibers made from different materials and ranging widely in size. Some are manufactured as small particles; others form when larger plastic products break down. Oregon Health Authority training materials have identified the lack of standard sampling and measurement methods as a barrier to comparing studies and assessing exposure. Identifying different types of plastic also requires specialized laboratory equipment.
EPA’s water research plan for fiscal years 2023 through 2026 included work on methods for studying microplastics and their possible effects on people and aquatic life. With that plan nearing its conclusion, the House members are seeking an accounting of what the agency accomplished, whether its methods can support reliable monitoring and what additional work is needed to assess risks.
Oregon’s Department of Environmental Quality identifies plastic fragments and fibers as concerns for drinking water, agriculture, air, wildlife and ecosystems. Its ongoing study of Oregon waste pathways examines materials including compost, landfill leachate and wastewater. The project may provide information about how plastics move through the environment, but it is not a statewide survey of treated tap water.
Questions about health effects also remain open. In a July science overview, GAO reported that microplastics have been found in the environment and human body and that some studies have associated exposure with health problems. The agency said scientists have not determined the extent to which the particles cause those problems. That earlier overview was a scientific briefing, not the review requested in September.
EPA announced a separate drinking water study this month to screen for a broad range of potential pollutants. The agency said the research could guide future decisions. The announcement did not add microplastics to the proposed list of substances that public water systems would be required to test.
EPA’s final monitoring rule will determine what data participating water systems collect in the next federal cycle. The requested GAO review, if undertaken, would give Congress a closer account of whether EPA’s microplastics research is ready to support broader testing. Until comparable testing is available, residents in Southern Oregon and elsewhere in the state have limited public data for judging whether the particles are present in their particular drinking water supply.