An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to www.epa.gov. This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Contaminant Candidate List (CCL) and Regulatory Determination

Contaminant Candidate List 4-CCL 4

The 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 announced the Final CCL 4 on November 17, 2016. On February 20, 2020, the Agency announced preliminary regulatory determinations for contaminants on the CCL 4. Read the preliminary regulatory determinations for contaminants on the CCL 4.

Federal Register Notices

What's on the Final CCL 4

The Final CCL 4 includes 97 chemicals or chemical groups and 12 microbial contaminants. The list includes, among others, chemicals used in commerce, pesticides, biological toxins, disinfection byproducts, pharmaceuticals and waterborne pathogens. These lists can be read by selecting the links below.