Earlier this summer, the U.S. Environmental Protection Agency (EPA) published its draft fifth Contaminant Candidate List (CCL 5) and accompanying technical support document.

By way of background, contaminants listed on the drinking water Contaminant Candidate List (CCL) are not currently subject to any proposed or promulgated national primary drinking water standards. EPA’s CCL does not impose any requirements on public water systems. But CCL contaminants may become regulated under the Safe Drinking Water Act because they are known or anticipated to occur in public water systems. EPA consequently uses the CCL as a stepping stone: the list ultimately classifies priority contaminants that require more information and a regulatory decision.

After considering public comments and the federal Science Advisory Board’s recommendations, EPA finalized its CCL 5 and technical support document this month. The final CCL 5 “includes 66 chemicals, 3 chemical groups (cyanotoxins, disinfection byproducts (DBPs), and per- and polyfluoroalkyl substances (PFAS)), and 12 microbial contaminants.” EPA expanded the definition of PFAS to include additional PFAS substructures such as PFAS that are (1) ethers or highly branched, (2) persistent in water, and (3) known to occur in drinking water or source water, or both. Next, EPA will continue to gather and analyze data on the CCL 5 contaminants to decide whether to formally promulgate a national primary drinking water regulation for at least five contaminants on the list.