California Hexavalent Chromium Drinking-Water MCL (SWRCB-DDW-21-003)

Summary

This is the California State Water Resources Control Board regulation establishing a drinking-water Maximum Contaminant Level (MCL) of 0.010 mg/L, equal to 10 µg/L or 10 ppb, specific to hexavalent chromium (Cr-VI). The State Water Board adopted the regulation on April 17, 2024; the Office of Administrative Law approved it on July 24, 2024; and it took effect on October 1, 2024. Before this regulation, hexavalent chromium in California drinking water was regulated only indirectly, through the total-chromium MCL of 50 µg/L, which does not separate the hexavalent fraction. The regulation amends California Code of Regulations Title 22 sections 64415, 64431, 64432, 64447.2, 64463.4, 64465, and 64481, with the numeric MCL placed in the inorganic-chemicals MCL table at section 64431.

This is a drinking-water standard, not a food limit. It governs the concentration of hexavalent chromium permitted in water delivered by public water systems. Its relevance to the food supply chain is indirect: water that meets or exceeds the MCL is used in food preparation, in food manufacturing, and to reconstitute powdered products such as infant formula. No California or US regulatory instrument sets a hexavalent-chromium maximum level for a food matrix; this MCL is the closest ingestion-route Cr-VI benchmark in the regulatory record and is derived from drinking-water toxicology, not from food-occurrence data.

Key numbers

Regulatory history

California first adopted a hexavalent-chromium MCL of 10 µg/L (rule DPH-11-005) that took effect in 2014. In 2017 the Superior Court of Sacramento County invalidated that regulation, holding that the State had not adequately documented why the MCL was economically feasible as required by California law. The 2014 MCL was withdrawn, leaving hexavalent chromium regulated only through the total-chromium MCL of 50 µg/L until the present regulation re-established a Cr-VI-specific MCL effective October 1, 2024.

The MCL of 10 µg/L is set above the OEHHA Public Health Goal of 0.02 µg/L (2011), which is the concentration posing no significant health risk over a lifetime of consumption. The gap between the PHG and the MCL reflects detection, treatment, and cost-feasibility considerations that California is required to weigh when setting an enforceable MCL; the State Water Board’s documentation estimates a residual lifetime cancer risk on the order of 1 in 2,000 for a person consuming two liters per day for 70 years at the MCL.

Scope and matrix distinction

The MCL applies to community water systems and nontransient-noncommunity water systems in California. It is an enforceable drinking-water concentration limit. It is not a food contaminant limit, not a labeling threshold, and not a per-day exposure value. It should not be compared directly to a food-occurrence concentration or treated as a food maximum level. Where the wiki cites this MCL, it is cited as the ingestion-route regulatory anchor for hexavalent chromium in water, and the drinking-water-versus-food distinction is stated explicitly.

Wiki pages updated on ingest

• Chromium, Hexavalent
• Chromium
• California — Maximum Contaminant Level for Hexavalent Chromium in Drinking Water
• Water

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.