On April 2, 2026, EPA Administrator Lee Zeldin and U.S. Department of Health and Human Services Secretary Robert F. Kennedy Jr. announced that the EPA has proposed to include microplastics as a priority contaminant group in its draft Sixth Contaminant Candidate List (“CCL 6”) under the Safe Drinking Water Act (“SDWA”). This 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. How quickly that regulatory pathway develops will depend significantly on a separate, still-pending decision: whether the EPA includes microplastics in the Sixth Unregulated Contaminant Monitoring Rule (“UCMR 6”).
The announcement is notable against the backdrop of the Trump administration’s broader deregulatory agenda. The administration has simultaneously moved to promote domestic fossil fuel production—fossil fuels being the petrochemical feedstock from which plastics are derived—and has directed federal agencies to return to plastic straws and end procurement of paper straws, see Executive Order 14208 (Feb. 10, 2025). Including microplastics in CCL 6, likely driven in part by the Make America Healthy Again movement’s focus on environmental contaminants in food and water, reflects a somewhat paradoxical federal posture: promoting conditions that may increase plastic production and waste while elevating microplastics—a direct byproduct of plastic degradation—as a priority drinking water concern.
What Including Microplastics in CCL 6 Means and Does Not Mean
As the EPA’s proposed rule makes clear, including microplastics in the CCL does not mean that microplastics will necessarily be regulated in the future. That said, including microplastics in the CCL means that the EPA believes that microplastics are known or anticipated to occur in public water systems and may require future regulation under the SDWA. 42 U.S.C. § 300g-1(b)(1)(B)(i)(I). Including microplastics in CCL 6 would have concrete consequences:
Research and data collection priorities. The EPA’s proposal states that CCL 6 will be used to prioritize research and data collection efforts, making it more likely that federal resources will flow towards the filling of significant gaps identified by the EPA, including: (1) methodological gaps, such as the need for standardized analytical methods for detecting and quantifying microplastics in drinking water; and (2) data gaps, such as which microplastic characteristics are most associated with potential adverse human health effects, how the occurrence of microplastics in mixtures may complicate detection and potential health risk attribution, and the sources of microplastics in drinking water. This could spur the development of a factual record necessary for the eventual regulation of microplastics in drinking water.
Regulatory determination obligation. The EPA must make regulatory determinations for at least five CCL contaminants every five years. 42 U.S.C. § 300g-1(b)(1)(B)(ii)(I). CCL listing therefore puts microplastics in the pool of contaminants that could ultimately be subject to a drinking water regulation. However, the EPA retains broad discretion in selecting which contaminants to evaluate each cycle and given the number of contaminants in the draft CCL 6 and prior CCLs, as well as the gaps identified above, microplastics could remain on the CCL for multiple cycles before the EPA has the requisite occurrence and toxicological data to support a regulatory determination.
UCMR prioritization. The EPA considers CCL contaminants when it selects UCMR candidates, making CCL listing a likely pathway to an eventual monitoring obligation (discussed further below).
Potential Inclusion of Microplastics in UCMR 6
The UCMR is the mechanism that requires public water systems to collect and report nationally representative occurrence data. Under the SDWA, the EPA must publish a new UCMR every five years listing no more than 30 unregulated contaminants for which public water systems must monitor. 42 U.S.C. § 300j-4(a)(2)(B)(i). The SDWA’s three-part test for regulation requires findings on adverse human health effects, occurrence in public water systems with a frequency and at levels of public health concern, and meaningful opportunity for health risk reduction, and expressly requires the EPA to consider UCMR data in that assessment. 42 U.S.C. § 300g-1(b)(1)(B)(ii)(II). Adding microplastics to UCMR 6—rather than a subsequent cycle—would accelerate development of the factual record needed to support regulation.
For context, PFOA and PFOS were added to CCL 3 in October 2009, included in UCMR 3 approximately two years later in May 2012, and it took approximately fifteen years from CCL listing to a final drinking water regulation in April 2024. This sequencing might suggest that microplastics would follow a similar path—with UCMR inclusion deferred to a subsequent cycle. Whether microplastics are included in UCMR 6 may depend on the following considerations:
The governors’ petition. In late 2025, seven governors petitioned the EPA under 42 U.S.C. § 300j-4(a)(2)(B)(ii) to include microplastics in UCMR 6. That provision directs the EPA to honor the petition unless inclusion “would prevent the listing of other contaminants of a higher public health concern.” The EPA could deny the petition on the basis that microplastics don’t make the top 30 contaminants for UCMR 6 because other contaminants are of a higher public health concern, although the EPA’s characterization of microplastics contamination in its CCL 6 announcement as “one of the most urgent and growing public health challenges facing Americans” suggests that the EPA may grant the petition.
Analytical methods. The absence of a standardized, EPA-approved method for detecting and quantifying microplastics in drinking water suitable for use by accredited laboratories is a practical consideration for UCMR 6 inclusion. The governors’ petition notes, however, that the EPA has been developing a spectroscopic analytical method for microplastics in drinking water, and that finalizing such methods before sampling begins would allow laboratories time to build the necessary capacity. California has also developed two standardized drinking water methods under its own monitoring program. California’s Phase 1 monitoring results—not yet publicly available—will represent the first large-scale standardized microplastics occurrence dataset in the country, potentially informing both federal method development and other state programs.
Ultimately, whether microplastics will be included in UCMR 6 is not yet known. EPA submitted the proposed rule to the White House Office of Management and Budget (“OMB”) for review on March 27, 2026. Under Executive Order 12866, OMB has up to 90 days to complete its review, after which the EPA would publish the proposed rule in the Federal Register for public comment—likely in the summer or fall of 2026.
Implications for Regulated Entities
Federal recognition of microplastics as a priority drinking water contaminant group—even at the CCL stage—begins building the evidentiary record that could lead to the eventual regulation of microplastics under the SDWA and other federal programs. CCL listing may also accelerate state regulatory activity. Key litigation risks to monitor:
Consumer fraud claims. Much of the microplastics litigation to date has involved consumer fraud claims—alleging that product representations are misleading or that manufacturers have made material omissions regarding the presence or risks of microplastics. Plaintiffs may cite the CCL 6 listing, and the factual record developed through subsequent regulatory proceedings, as evidence of the risks associated with microplastics exposure to support such claims—for example, as evidence that affirmative representations about product safety are misleading, or that failure to disclose the presence of microplastics constitutes a material omission.
State AG actions. State attorneys general are already pursuing claims against plastic manufacturers—primarily bottled beverage companies and fossil fuel companies— targeting the alleged public nuisance created by plastic pollution broadly, not cleanup of microplastics from drinking water specifically. As the federal and state regulatory record develops, those claims are likely to expand in scope.
Downstream cost recovery. Federal drinking water limits for microplastics remain unlikely in the near term given the data gaps the EPA has identified. If and when such limits are set—at the federal or state level—public water systems and others facing compliance costs may pursue claims against manufacturers under state common law theories such as nuisance, negligence, and product liability.
The CCL 6 comment period closes June 1, 2026 (docket EPA-HQ-OW-2022-0946).
Please don’t hesitate to reach out if you would like assistance submitting comments or have any other questions.