Frequent Questions

I'd like to know more about the CCL process and when CCL contaminants are determined to need regulation (such as cyanotoxin)?

EPA has national primary drinking water regulations for more than 90 contaminants. The Safe Drinking Water Act (SDWA) includes a process that we must follow to identify and list unregulated contaminants which may require a national drinking water regulation in the future.

EPA must periodically publish this list of contaminants (called the Contaminant Candidate List or CCL) and decide whether to regulate at least five or more contaminants on the list (called Regulatory Determinations).

EPA uses this list of unregulated contaminants to prioritize research and data collection efforts to help us determine whether we should regulate a specific contaminant.

Cyanotoxins are on the CCL 3. In developing the CCL 3, EPA implemented an improved process from that which was used for CCL 1 and CCL 2. This new process builds on evaluations used for previous CCLs and was based on substantial expert input and recommendations from the National Academy of Science's National Research Council (NRC) and the National Drinking Water Advisory Council (NDWAC).

EPA used a multi-step CCL process to identify contaminants for inclusion on the final CCL 3. The key steps include:

  • Identifying a broad universe of potential drinking water contaminants (called the CCL 3 Universe). EPA initially considered approximately 7,500 potential chemical and microbial contaminants.
  • Applying screening criteria to the universe EPA identified almost 600 of those contaminants that should be further evaluated (the preliminary CCL or PCCL) based on a contaminant's potential to occur in public water systems and the potential for public health concern.
  • EPA then selected 116 contaminants from the PCCL to include on the CCL based on more detailed evaluation of occurrence and health effects and expert judgment.
  • EPA incorporated information from the public, expert input, and expert review in the CCL process.
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