A Step Toward Federal Regulation of Microplastics?: EPA’s Draft Contaminant Candidate List 6

On April 2, 2026, the U.S. Environmental Protection Agency (EPA) announced that it is including microplastics on its draft Contaminant Candidate List 6 (CCL 6). The CCL is the front end of EPA’s Safe Drinking Water Act (SDWA) process for identifying contaminants that may merit additional study, monitoring, and potentially regulation. EPA publishes the list every five years. Microplastics — tiny plastic fragments ranging in size from 5 millimeters or smaller, which often result from the breakdown of larger plastic products — have been widely detected in the environment and increasingly gained attention for their potential to accumulate in human beings and wildlife. By including microplastics on the draft CCL, EPA has identified them as “contaminants . . . known or anticipated to occur in public water systems” that “may require regulation” under SDWA and indicated its intent to prioritize them for further research and data collection efforts. The draft CCL 6 will now undergo a 60-day period of public comment. EPA has indicated that it expects to finalize the list by November 17, 2026. If it is ultimately approved, the inclusion of microplastics on the CCL could be a significant step toward eventual regulation of these particles, which, despite their widespread detection, have been largely unregulated to date.

EPA is considering additional pathways beyond the CCL for the regulation of microplastics. Last summer, it was reported that EPA was considering a November 2024 petition from 175 environmental groups calling for microplastics to be included on EPA’s Sixth Unregulated Contaminant Monitoring Rule (UCMR 6). And in late 2025, the governors of New Jersey, Delaware, Illinois, Maryland, Wisconsin, Michigan, and Connecticut submitted a joint petition likewise urging EPA to include microplastics on the UCMR. EPA uses the UCMR to collect data on contaminants suspected to be present in drinking water, but which do not yet have health-based standards under the Safe Drinking Water Act. UCMR 6 will identify the contaminants to be monitored in drinking water sources during the 2027–2031 cycle. EPA’s proposed UCMR 6 remains under White House review, but EPA has not yet confirmed whether microplastics will be included in UCMR 6, which is expected to be finalized by the end of 2026. 

For companies that manufacture, use, or otherwise place plastic-containing products into commerce, the beginning of microplastics regulation at the federal level may not be far off. With research and data collection likely to increase — coupled with continued calls for action from state and environmental groups — an expansion of both regulation and litigation concerning the presence of microplastics in drinking water, the environment, and even the human body seems certain to follow.

© Arnold & Porter Kaye Scholer LLP 2026 All Rights Reserved. This Blog post is intended to be a general summary of the law and does not constitute legal advice. You should consult with counsel to determine applicable legal requirements in a specific fact situation.