On April 2, 2026, the U.S. Environmental Protection Agency (EPA) announced the release of a draft Sixth Contaminant Candidate List (CCL 6) under the Safe Drinking Water Act. For the first time, the agency has designated microplastics and pharmaceuticals as priority contaminant groups, alongside PFAS, disinfection byproducts, and numerous other chemicals and microbes.
While the action does not impose immediate regulatory requirements, it signals increased federal scrutiny of these contaminants and may have important implications for companies across multiple sectors.
Overview of the EPA’s Action
The CCL is a list of contaminants known or anticipated to occur in public water systems but are not currently subject to National Primary Drinking Water Regulations under the Safe Drinking Water Act.
The draft CCL 6 includes four chemical groups (microplastics, pharmaceuticals, disinfection byproducts, and unregulated PFAS), 75 chemicals, and nine microbes that may be present in public water systems.
The EPA defines pharmaceuticals as any substance defined as a drug under the Federal Food, Drug, and Cosmetic Act. It defines microplastics as plastic particles ranging in size from 5 millimeters, roughly the size of a pencil eraser, to 1 nanometer. Notably, the EPA’s designation of microplastics and pharmaceuticals marks the first time the agency has elevated these potential contaminants to the CCL.
The EPA has emphasized that inclusion on the CCL is intended to drive research, monitoring, and data collection, rather than impose immediate compliance obligations. The agency will use this information to determine whether future regulatory standards—such as maximum contaminant levels for drinking water—are warranted.
Next Steps
The EPA will consult with its independent Science Advisory Board and is accepting public comments until June 5, 2026. It expects to finalize the CCL by November 17, 2026.
Following publication, the EPA will determine whether to establish National Drinking Water Regulations for at least five listed contaminants if there is sufficient relevant data. Historically, relatively few contaminants included on prior CCLs have progressed to enforceable standards. For contaminants the EPA does not choose to regulate, it will continue to support research and fill information gaps.
Implications for Industry
Increased monitoring
Companies—particularly water utilities, manufacturers, and entities with wastewater discharges—should anticipate increased monitoring. The inclusion of microplastics and pharmaceuticals on the CCL may lead to expanded sampling, reporting, and analytical requirements through the EPA’s Unregulated Contaminant Monitoring Rule program or similar mechanisms.
Litigation risk
As seen with PFAS, regulatory attention can catalyze private litigation, including toxic tort claims and cost recovery suits by water providers. Plaintiffs may use identification of microplastics and pharmaceuticals as potential contaminants to provide additional grounds for these claims, even before enforceable standards.
Intersection with existing regulatory regimes
The EPA’s action also intersects with ongoing federal and state initiatives targeting PFAS and other potential contaminants. Companies should consider the cumulative impact of overlapping regulatory frameworks, particularly when operations involve complex chemical use or discharge profiles.
Opportunity for engagement
The public comment period provides an opportunity for stakeholders to shape the scope and priorities of the EPA’s efforts. Industry participants may wish to submit comments addressing feasibility, analytical challenges, cost considerations, and the current state of scientific evidence.
Key Takeaways
The EPA’s designation of microplastics and pharmaceuticals as priority drinking-water contaminants represents a continued shift in federal regulatory focus toward emerging contaminants. Although the action does not impose immediate compliance obligations, it signals a likely increase in regulatory and public attention, even for an administration that has historically prioritized deregulation.
Businesses that anticipate impacts should consider participating in the public comment process.
If you have any questions, or would like additional information, please contact one of the attorneys on our Environment, Land Use & Natural Resources team.
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