On July 1, 2026, the EPA issued its long-awaited proposed Sixth Unregulated Contaminant Monitoring Rule (“UCMR 6”). Despite two petitions urging their inclusion, the agency decided not to add microplastics to the list of contaminants that public water systems will be required to monitor during the 2028–2030 sample collection period.

The Petitions

The EPA’s proposal confirms that the agency received two separate requests to add microplastics to UCMR 6. In November 2024, Food and Water Watch and other organizations petitioned for inclusion. Then, on November 26, 2025, the Governors of New Jersey, Delaware, Illinois, Maryland, Michigan, Wisconsin, and Connecticut submitted a formal petition under Safe Drinking Water Act (“SDWA”) section 1445(a)(2)(B)(ii)—the provision that requires the EPA to include a contaminant recommended by seven or more governors unless doing so would prevent the listing of other contaminants of a higher public health concern.

Why EPA Said No—For Now

The EPA concluded that there is currently no validated EPA or consensus drinking water analytical method for microplastics with the quality control, accuracy, and precision that could be used for UCMR 6—and that developing one within the statutory timeframe (December 27, 2026) isn’t feasible. The EPA noted it will continue evaluating existing procedures and techniques (ASTM D8332-20 and D8333-20) to develop robust and validated methods, as well as adequate laboratory capacity, that would support national monitoring for microplastics in a future UCMR.

For Now—CCL 6

Rather than UCMR 6 inclusion, the EPA is treating its April 2026 addition of microplastics as a group on the draft Sixth Contaminant Candidate List (“CCL 6”) as a first step toward defining and better understanding potential public health risk from exposure via drinking water.

As we discussed when CCL 6 was announced, that listing would channel greater federal focus and resources toward understanding the potential human health impacts associated with microplastics in drinking water, and could serve as a predicate to eventual regulation—though any such regulation won’t come soon, and certainly not until microplastics are added to a UCMR.

In its UCMR 6 proposal, the EPA explains that the CCL 6 listing will allow it to prioritize research needed to define and better understand the characteristics of microplastics (i.e., size, type of plastic, shape, count, etc.) that are associated with potential public health risks, and that this research may inform the development of drinking water analytical methods that can be used to standardize data collection and analysis in the future. The agency says it will collaborate with other federal agencies to evaluate risks and exposures of microplastics to enable future monitoring for those microplastics that present potential health risks. It explains that this approach will also enable the EPA to list microplastics on a future UCMR when national monitoring is scientifically feasible through the availability of a validated drinking water analytical method.

What This Means Going Forward

For now, microplastics remain outside the formal UCMR pipeline, which will instead monitor 30 other contaminants during the 2028–2030 sample collection period. However, the EPA’s proposal leaves the door open to revisit microplastics in a future UCMR cycle once a validated analytical method exists.

Comments on the proposed rule (including on the EPA’s decision not to include microplastics) are due August 31, 2026, with public meetings scheduled for August 11 and 12, 2026.

Even if there is no monitoring obligation in this UCMR cycle, draft CCL 6 suggests that understanding microplastics will remain a federal priority, even within an administration that has otherwise moved to reduce regulatory burdens on industry.

Stakeholders should consider submitting comments that could influence the trajectory of microplastics under the SDWA.