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 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 This website is no longer updated and links to external websites and some internal pages may not work.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

Regulatory Determination 3

The Safe Drinking Water Act (SDWA) directs EPA to publish a list of contaminants (referred to as the Contaminant Candidate List, or CCL) to assist in priority-setting efforts. SDWA also directs the Agency to select five or more contaminants from the current CCL and determine whether to regulate these contaminants with a National Primary Drinking Water Regulation (NPDWR).
To regulate a contaminant SDWA requires that EPA determine whether:
  1. The contaminant may have an adverse effect on the health of persons;
  2. The contaminant is known to occur or there is a substantial likelihood the contaminant will occur in public water systems with a frequency and at levels of public health concern; and
  3. In the sole judgment of the Administrator, regulation of the contaminant presents a meaningful opportunity for health risk reductions for persons served by public water systems.

Final Regulatory Determinations for CCL 3

On January 4, 2016, EPA announced the final determinations not to regulate four of the 116 CCL 3 contaminants – dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone. The agency delayed the final regulatory determination on strontium to consider additional data and decide whether there is a meaningful opportunity for health risk reduction by regulating strontium in drinking water.

Preliminary Regulatory Determinations for CCL 3

EPA announced and requested public comment on the preliminary regulatory determinations for five CCL 3 contaminants. EPA made preliminary determinations to regulate strontium in drinking water and to not regulate four contaminants (i.e., dimethoate, 1,3-dinitrobenzene, terbufos, and terbufos sulfone).

Public Meetings Held On Preliminary Regulatory Determinations for the CCL3

EPA hosted a public stakeholder meeting on December 9, 2014, in Washington, DC, to discuss the Agency’s Regulatory Determination 3. For more information see the slides presented.