The State Water Board is sharing the following information on behalf of the United States Environmental Protection Agency.
The Environmental Protection Agency (EPA) is pleased to announce that on December 10, 2024, the EPA Administrator signed a final rule establishing a revised statewide chronic freshwater selenium water quality criterion applicable to certain California waters to protect aquatic life and aquatic-dependent wildlife from exposure to toxic levels of selenium. The criterion replaces California’s previous selenium criterion for certain waters that was promulgated in 2000 as part of the California Toxics Rule (40 CFR § 131.38).
Selenium is an essential micronutrient and low levels of selenium in the diet are required for normal cellular function in almost all animals. However, selenium at amounts not much above the required nutritional levels can have toxic effects on aquatic life and aquatic-dependent wildlife, making it one of the most toxic of the biologically essential elements.
The EPA’s final criterion for California is based on the EPA’s recommended 2016 Clean Water Act (CWA) section 304(a) chronic freshwater selenium criterion, which is comprised of fish tissue and water column criterion elements, with two additions to the criterion:
a bird tissue criterion element for the protection of aquatic-dependent wildlife, and
an optional performance-based approach for translating the tissue elements into site-specific water column criterion elements.
A prepublication version of the final rule is available on the EPA’s Water Quality Standards website. The criterion will be effective 30 days after the date of publication in the Federal Register for use in all CWA programs in California. If you have any questions, please call or e-mail Diane Fleck at (213) 244-1836 or Fleck.Diane@EPA.gov.
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