The U.S. EPA’s Unregulated Contaminant Monitoring Rule (UCMR) requires all public drinking water systems serving at least 10,000 people and a random subset of smaller public systems to monitor for selected contaminants of emerging concern (CECs) every five years. This monitoring can help define presence and risk of contaminants may inform future regulatory action, based on findings.

  • EPA selects up to 30 contaminants to test for under UCMR from a longer list of chemicals that are known or suspected to be present in drinking water but are not subject to regulations.
  • The data from UCMR testing creates a federal baseline for exploring the potential presence and health impacts of unregulated chemicals in drinking water, guides federal research priorities, and provides a basis for future regulatory actions.
  • Though most UCMR sampling is conducted on treated water, it can point to source water conditions since CECs may pass through drinking water treatment processes.
  • In 2021, UCMR requirements will be expanded to require monitoring for public water systems serving over 3,300 people.