Which contaminants make up the Contaminant Candidate List (CCL)?

• A. Contaminants that are newly nominated to be researched
• B. Contaminants that are not known or anticipated to occur at PWSs
• C. Contaminants not regulated by the National Primary Drinking Water Regulations
• D. Contaminants that do not warrant regulation under the SDWA

Answer: (C)

The Contaminant Candidate List identifies substances that are not currently regulated by the National Primary Drinking Water Regulations but for which data exist to support further evaluation for potential regulation under the Safe Drinking Water Act. The purpose is to flag contaminants that may occur in drinking water and could pose health risks, so more information is gathered to decide if they should be regulated in the future. This is why the best description is that these are contaminants not regulated by the National Primary Drinking Water Regulations. The other ideas don’t fit: some candidates are indeed known to occur and are being studied, and the list is about assessing whether regulation might be warranted rather than about substances that are known not to warrant regulation.