The Drinking Water Contaminant Candidate List
— EPA Priorities Chemicals for Future Regulation

In response to the 1996 Safe Drinking Water Act Amendments, EPA created a list that prioritizes drinking water contaminants for potential regulation. In particular, the agency considered the health risks of unregulated drinking water contaminants to vulnerable populations such as infants, the elderly, and those with serious illnesses in prioritizing these contaminants. On March 2, 1998, the agency finalized this list, called the Drinking Water Contaminant Candidate List (CCL). The CCL is a list of contaminants that are not subject to any current drinking water regulations but are known to occur in public drinking water supplies.

Contaminants on the CCL are divided into three separate categories:

* Contaminants that EPA will consider regulating;
* Contaminants that need additional health, treatment, or analytical methods research before EPA can consider regulating them; and
* Contaminants that need additional research to see where and how often they occur in drinking water before EPA can consider regulating them.

EPA must select five or more contaminants from the CCL by 2001 and determine whether to regulate them or not. If the agency determines that a contaminant needs regulating, it will establish a standard no later than February 2005. In addition, the agency must identify a maximum of 30 contaminants from the list for unregulated monitoring. This monitoring data will be used for further drinking water research.

Every five years, EPA will revise the CCL using input from the scientific community, water utilities, environmental and public interest groups, state regulatory agencies, public health offices, to name a few. With a revised list, the agency will repeat the process of contaminant selection.

Included on the CCL are 7 inorganic contaminants like aluminum and manganese, 22 synthetic organic contaminants like MTBE (an octane enhancer in gasoline), 21 pesticides including several pesticide degradation products that are as toxic as the pesticides themselves, and 10 microbiological contaminants including several viruses. For a complete list of contaminants, click here to read EPA's summary of the CCL.