The U.S. Environmental Protection Agency (EPA) has revised its recommended water quality criteria for recreational waters. The revisions replace criteria the agency established in 1986 and are based on several recent health studies. Intended to protect against gastrointestinal illness from fecal contamination, they establish two sets of concentration thresholds for fecal bacteria—enterococci and E. coli—measured as the geometrical mean of colony-forming units in monitored water-quality samples.

The revisions also contain a backstop measure known as a statistical threshold value, or ST V, that was not in the 1986 criteria. The two sets of concentration thresholds are optional according to EPA, and states may use the recommended criteria to establish standards identical to the criteria, or different, so long as they are based on sound science. The ST V serves as the backstop or secondary concentration level that the agency says must be met to protect public health. A consent decree required EPA to publish final criteria by November 30, 2012. NRDC v. EPA, No. 06-4843 (E.D. Cal. 9/12/12).