The Safe Drinking Water Act (SDWA) requires the EPA to make regulatory determinations on at least five contaminants on the Contaminant Candidate List (CCL) every five years. The 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. A regulatory determination is a decision about whether or not to begin the process to propose and promulgate a national primary drinking water regulation for an unregulated contaminant. A preliminary regulatory determination presents EPA’s supporting rationale about whether the specific statutory criteria for regulating a contaminant have been met. On March 10, 2020, the EPA published a notice which proposed to make positive regulatory determinations for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and to make negative determinations for six contaminants (1,1-dichloroethane, acetochlor, methyl bromide, metolachlor, nitrobenzene, and RDX). The notice also presents an update on three other contaminants (strontium, 1,4-dioxane, and 1,2,3-trichloropropane).Proposing a regulatory determination enables the public to provide the EPA with information critical to regulatory decision making towards protecting public health and communities across the nation.