CCL 6 Frequent Questions

What is the drinking water CCL?

The drinking water Contaminant Candidate List (CCL) is a list of contaminants that are currently not subject to any proposed or promulgated national primary drinking water regulations but are known or anticipated to occur in public water systems. Contaminants listed on the CCL may require future regulation under the Safe Drinking Water Act (SDWA). EPA uses the CCL to identify priority contaminants for regulatory decision making and information collection needs.

How often is the CCL published?

SDWA directs EPA to publish a CCL every five years. The agency published the First CCL (CCL 1) in March 1998, the Second CCL (CCL 2) in February 2005, the Third CCL (CCL 3) in October 2009, the Fourth CCL (CCL 4) in November 2016, and the Fifth CCL (CCL 5) in November 2022.

What approach did EPA use to list contaminants on the CCL 6?

In selecting contaminants for the CCL 6, EPA:

Followed the three-step process, originally developed for CCL 3 and refined during subsequent CCLs, which included building a broad universe of contaminants, screening the universe of contaminants based on available health and occurrence information, and evaluating that information in greater detail with the aid of Agency experts to select the CCL.
Utilized the best available data to characterize the occurrence and adverse health risks a chemical contaminant may pose from potential drinking water exposure.
Sought and evaluated nominations from the public for additional contaminants to consider in February 2023.

What contaminants are included on the draft CCL 6?

The draft CCL 6 includes 75 chemicals, 4 chemical groups (microplastics, pharmaceuticals, per- and polyfluoroalkyl substances (PFAS), and disinfection byproducts (DBPs) and 9 microbial contaminants that are known or anticipated to occur in public water systems.

How has EPA proposed to list PFAS as a group on the CCL?

EPA proposes to list PFAS as a group inclusive of any PFAS covered under the CCL structural definition, except for those PFAS chemicals that will be subject to a national primary drinking water regulation at the time of publication of the final CCL 6 (see 40 CFR Part 141 Subpart Z – Control of Per- and Polyfluoroalkyl Substances (PFAS)). This action is consistent with the science-based approach informed by public comment under the previous CCL 5, is responsive to public nominations, and is in keeping with the agency’s commitment to better understanding and ultimately reducing the potential risks caused by this broad class of chemicals.

How has EPA defined pharmaceuticals on the CCL?

EPA proposes to list pharmaceuticals as a group inclusive of all substances defined as a “drug” under the Federal Food, Drug, and Cosmetic Act, to further prioritize research and information needed to identify which specific pharmaceuticals are occurring in drinking water and may be of greatest public health concern.

Does the CCL impose any requirements on public water systems?

No. Publication of the CCL does not impose any requirements on public water systems. If EPA decides to regulate a contaminant on the list in the future, the Agency will start a separate rulemaking process with opportunity for public comment.

What are the next steps for the CCL?

EPA plans to consult with the SAB on the draft CCL 6 in 2026. The agency will consider public comments and SAB feedback in the final CCL 6. The final CCL 6 is expected to be signed for publication by November 17, 2026.

What happens to contaminants on the CCL 6?

After the final CCL is published, EPA must determine whether or not to regulate at least five contaminants from the CCL in a separate process called Regulatory Determination. EPA will compile and evaluate additional data on the CCL contaminants. The Agency will make regulatory determinations for the CCL contaminants for which there is sufficient health effects and occurrence data, and which present the greatest public health concern. EPA will continue to collect information, conduct, and support research and/or find ways to fill data and information gaps for contaminants that lack sufficient information to make a regulatory determination at that time.

What is a regulatory determination?

A regulatory determination is a formal decision on whether EPA should initiate a process to develop a national primary drinking water regulation for a specific contaminant. The SDWA requires EPA to make regulatory determinations for at least five contaminants from the most recent CCL within five years after the completion of the previous round of regulatory determinations. Once the final CCL 6 has been published, EPA will evaluate the CCL contaminants for regulatory determinations. To see the list of regulatory determinations for the previous CCLs, please go to: https://www.epa.gov/ccl.

Where can I find more information about this notice and the CCL?

For information on the CCL 6, please visit the EPA website, https://www.epa.gov/ccl/draft-contaminant-candidate-list-6-ccl-6. For general information on drinking water, please visit the EPA drinking water website at https://www.epa.gov/ground-water-and-drinking-water.