Microplastics Regulation: EPA Declines to Act, California Moves Forward
EPA and California took opposite approaches to microplastics regulation within weeks of each other. On July 1, 2026, EPA proposed to omit microplastics from the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6). Two weeks earlier on June 18, California’s Department of Toxic Substances Control (DTSC) finalized a regulation adding microplastics to the state’s Safer Consumer Products (SCP) Candidate Chemicals List.
What EPA Proposed
In the proposed UCMR 6, EPA proposed not to include microplastics despite a petition from the governors of seven states—New Jersey, Delaware, Illinois, Maryland, Michigan, Wisconsin, and Connecticut. That petition matters because the Safe Drinking Water Act section 1445(a)(2)(B)(ii) directs that the administrator “shall include” a contaminant recommended by seven or more governors, unless listing it would prevent listing other contaminants of higher public health concern.
EPA’s basis for declining is analytical feasibility. The agency states there is no validated EPA or consensus drinking water method with the necessary accuracy and precision to measure microplastics for UCMR 6, and that developing one before the statutory deadline of December 27, 2026, is not feasible. EPA points out that the governors’ petition itself acknowledges the absence of such a method. Because monitoring is the entire purpose of the UCMR, EPA argues, requiring systems to test for something no approved method can quantify would yield no usable data while displacing contaminants that can be measured. Instead, EPA has placed microplastics on the draft Contaminant Candidate List 6 as a first step, and says it will keep evaluating existing consensus practices toward a future method.
It is worth watching whether EPA’s feasibility rationale squarely fits the statutory exception, which is written in terms of “higher public health concern” rather than measurability. This is a proposed rule open for comment through August 31, 2026, so the final reasoning—and outcome—could change.
What California Did
DTSC’s action runs the other way. The Office of Administrative Law approved the regulation on June 18, 2026, with an effective date of October 1, 2026; it amends Title 22 to add microplastics—defined as plastics under 5 millimeters in their longest dimension, whether intentionally manufactured or generated by the fragmentation of larger plastics—to the Candidate Chemicals List. As discussed in a previous post, listing does not itself regulate anything; it is a predicate that lets DTSC evaluate products that contain or generate microplastics and potentially designate them priority products through a later rulemaking. Listing requires only a hazard trait and consideration of adverse impacts, exposures, and information availability, not a validated quantification method. As part of its research on microplastics, DTSC published a background document in November 2025 identifying products that could be designated as priority products.
According to DTSC’s Final Statement of Reasons, the agency declined to explicitly define “plastics” in the regulation “because ‘plastics’ has an ordinary English meaning.” Manufacturers should be aware that DTSC considers biobased and biodegradable polymeric substances within its jurisdiction; DTSC states that
All microplastics, including biodegradable ones, exhibit at least one hazard trait under the Safer Consumer Products Regulations, namely the particle size and fiber dimension hazard trait. Therefore, it is appropriate for DTSC to designate the entire class of microplastics as a Candidate Chemical.
In response to comments that microplastics are more than one chemical and therefore cannot be added to the Candidate Chemicals List through a single rulemaking for a categorical definition, the agency asserted that “there is nothing in the statutes or regulatory history that even implies categorical identities are unauthorized,” noting that list already contains categorical listings, such as PFAS.
The statement of reasons adds that any subsequent priority products proposal for microplastics “will involve an evaluation of potential exposures and significant or widespread adverse impacts associated with those specific products, as well as a formal rulemaking process with opportunity for public input.” A challenge to the rule is expected.
