The US Environmental Protection Agency (EPA) on April 2, 2026 published the draft Sixth Contaminant Candidate List (CCL 6), which for the first time identifies both microplastics and pharmaceuticals as contaminant groups for potential future drinking water regulations under the Safe Drinking Water Act (SDWA). EPA also announced human health benchmarks for 374 pharmaceuticals and highlighted broader federal investment in microplastics research.
These EPA actions should be viewed in the context of Health Secretary Robert F. Kennedy Jr. announcing that the US Department of Health and Human Services will put $144 million into a new program focused on measuring microplastics in humans, evaluating potential health effects, and exploring ways to remove them from the body.
The publication of the CCL 6, which EPA is required to do every five years under the SDWA, is an initial, procedural step rather than a regulatory mandate. The draft CCL 6 does not itself establish new drinking water standards or require immediate action by water systems or industry. It can, however, lead to real consequences by acting as an initial screening step under the SDWA to identify substances for potential regulation. It is the start of a process that can shape future research priorities, monitoring requirements, and potential regulatory action.
For example, EPA included per- and polyfluoroalkyl substances (PFAS) as a broad class in the fifth CCL in 2022. By 2024, EPA finalized a rule setting legally enforceable Maximum Contaminant Levels (MCLs) for six PFAS (PFOA, PFOS, PFHxS, PFNA, HFPO-DA, and mixtures) and officially designated PFOA and PFOS as “hazardous substances” under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Microplastics and pharmaceuticals could follow a similar regulatory timeline now that these substances have been identified as contaminant groups in the draft CCL 6.
KEY TAKEAWAYS
- Microplastics and pharmaceuticals are now identified on the CCL 6 as priority drinking water contaminant groups, meaning they will be studied and monitored at a heightened level
- Draft CCL 6 also includes PFAS, disinfection byproducts, 75 individual chemicals, and nine microbes
- EPA often uses the CCL to choose substances for the Unregulated Contaminant Monitoring Rule (UCMR), which requires public water systems to monitor for these substances to gather occurrence data; it remains unclear whether EPA will include microplastics in the forthcoming UCMR, which would be a consequential step toward national occurrence data and possible future regulation
WHAT DRAFT CCL 6 COVERS
The CCL is EPA’s preliminary list of unregulated water contaminants requiring further study for potential regulation under the SDWA. It kicks off a regulatory process by identifying priority substances for research, monitoring, and future regulatory consideration. Under the SDWA, EPA must make a formal determination on at least five substances from the list, deciding whether to move forward with a National Primary Drinking Water Regulation, which brings enforceable limits. EPA’s draft CCL 6 identifies four contaminant groups—microplastics, pharmaceuticals, PFAS, and disinfection byproducts—along with 75 chemicals and nine microbes that may be found in drinking water. EPA has described the action as a means to prioritize research, funding, and information collection to better understand potential health risks and to support future regulatory decision-making. EPA also emphasized that this is the first time microplastics and pharmaceuticals have been elevated to the CCL as contaminant groups.
EPA separately released human health benchmarks for 374 pharmaceuticals. According to EPA, these benchmarks are not regulations and are not independently enforceable, but they are intended to help states, Tribes, and local water systems assess risk and evaluate possible next steps when pharmaceutical contamination is detected at concerning levels.
SIGNIFICANCE FOR COMPANIES THAT MANUFACTURE OR USE PLASTICS
EPA’s action signals increased federal attention on microplastics, including potential assessment of where they come from, how they are defined, how they are measured, how prevalent they are in water systems, and whether they may become subject to future regulation. Although the draft does not impose direct obligations on manufacturers or downstream users, it places microplastics more squarely within EPA’s drinking water framework.
This is not just an issue for plastic manufacturers. Businesses that use or generate microplastics—or whose products, packaging, components, or processes may break down or contribute microplastics over time—should be prepared for the potential that EPA considers wastewater pathways, waste handling practices, supplier and customer questions, and ultimately the regulation of a wide array of potential sources of microplastics. The current focus on clear definitions, analytical methods, lab capacity, and standardized sampling suggests those technical issues may be central to future compliance, enforcement, and litigation discussions.
SIGNIFICANCE FOR PHARMACEUTICAL COMPANIES
For pharmaceutical companies, the announcement is notable because EPA is now considering pharmaceuticals as a distinct drinking water contaminant group for the first time. EPA is simultaneously releasing human health benchmarks for 374 pharmaceuticals. For example, EPA has identified certain pharmaceuticals such as antidepressants, hormones, and antibiotics as types of substances that warrant closer evaluation because of the potential impacts on water systems.
Although EPA’s new pharmaceutical benchmarks are not enforceable limits, they will have practical and immediate implications. For instance, states, Tribes, and local water systems can use these benchmarks as the basis for additional actions. EPA has set similar benchmarks for water quality standards that states and local water systems adopt or create stricter standards based on to assess water quality risks, prioritize monitoring, and inform local regulations, especially for contaminants like pesticides.
MONITORING, METHODS, AND OTHER OPEN QUESTIONS
A central issue for these current developments is whether EPA will move from candidate listing to national monitoring. Commentators and stakeholders have emphasized that inclusion in the forthcoming UCMR would be a potentially more consequential next step for microplastics because it could generate significant national occurrence data that would inform and could influence future regulatory determinations.
That transition may not be straightforward. Reporting around EPA’s announcement emphasized several unresolved issues, including the need for clear definitions, validated analytical methods, sufficient laboratory capacity, and standardized sampling and testing protocols. EPA officials and other observers have also suggested that these scientific and operational issues must be addressed before the agency can realistically move toward broader monitoring and, ultimately, enforceable standards.
TIMELINE AND NEXT STEPS
The publication of the draft CCL 6 in the Federal Register opened a 60-day public comment period. EPA has also stated that it will consult its Science Advisory Board before finalizing the list, which the agency expects to be signed by November 17, 2026. Separately, EPA is expected later this year to update the UCMR, and that process may prove particularly important for companies focused on microplastics.
WHAT COMPANIES SHOULD DO NOW
Companies in the plastics and pharmaceutical sectors should consider taking the following near-term steps:
- Assess whether products, processes, packaging, wastewater streams, or disposal practices create any risks or identified pathways for microplastics or pharmaceutical residues to enter water systems
- Track EPA’s next steps, including the CCL 6 public comment period, Science Advisory Board review, and forthcoming monitoring rule
- Consider whether participation in the comment process is warranted, either individually or as part of a group or association, particularly on issues such as definitions, methods, monitoring feasibility, and implementation timing
- Prepare for potential additional inquiries from regulators, customers, investors, and other stakeholders
CONCLUSION
EPA’s decision to place microplastics and pharmaceuticals on the draft CCL 6 does not itself establish new drinking water limits, but it is an important step in that direction. It signals that EPA is moving these issues further into the SDWA pipeline while broader questions about monitoring, methods, and eventual regulatory scope remain unresolved.
Companies that manufacture, use, or may contribute to microplastics, and companies whose products may result in pharmaceutical residues entering water systems, should stay apprised of EPA’s rulemaking, related federal research initiatives, and any subsequent state or local activity as this area continues to evolve.
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