California Proposition 65 — Hexavalent Chromium Listing and Safe-Harbor Levels

Chromium (hexavalent compounds) is listed under California’s Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65) under two separate findings: as a carcinogen, listed February 27, 1987 through the Labor Code listing mechanism, and as a developmental, female reproductive, and male reproductive toxicant, listed December 19, 2008 following a determination by the state’s qualified experts (OEHHA Prop 65 Cr-VI). This page covers both findings and their associated safe-harbor levels.

This is a chemical-listing and product-labeling instrument, not a food contaminant limit. A Proposition 65 listing triggers a warning obligation for businesses whose products expose California consumers above the applicable safe-harbor level; it does not set a maximum permitted concentration in any food matrix or in drinking water. The enforceable California drinking-water concentration limit for hexavalent chromium is the separate State Water Resources Control Board MCL covered at California — Maximum Contaminant Level for Hexavalent Chromium in Drinking Water. See Chromium, Hexavalent for the species toxicology and food-occurrence evidence.

Listing record

The 1987 cancer listing followed the Labor Code mechanism of California Health and Safety Code 25249.8, which incorporates chemicals identified as carcinogens by authoritative bodies; hexavalent chromium compounds are classified as carcinogenic to humans by the International Agency for Research on Cancer, with lung cancer by inhalation the canonical endpoint. The 2008 reproductive and developmental listings followed the state’s-qualified-experts mechanism, in which the Developmental and Reproductive Toxicant Identification Committee determined that hexavalent chromium compounds had been clearly shown to cause developmental, female reproductive, and male reproductive toxicity (OEHHA Prop 65 Cr-VI).

Safe-harbor levels

The cancer NSRL is route-specific to inhalation, consistent with the carcinogenicity of hexavalent chromium being best characterized for the inhalation route (OEHHA Prop 65 Cr-VI). The reproductive-toxicity MADL of 8.2 µg/day applies to the oral route. Both are safe-harbor exposure thresholds below which a business is not required to provide a Proposition 65 warning; neither is a maximum permitted concentration in a product or food.

Statutory meaning

A safe-harbor level is the exposure below which no warning is required. For a carcinogen, the NSRL is the daily intake calculated to result in no more than one excess cancer case per 100,000 exposed individuals over a lifetime; for a reproductive toxicant, the MADL is the daily intake at 1,000 times below the level showing no observable reproductive effect. A consumer product that exposes a California consumer above the applicable safe-harbor level by the relevant route must carry a Proposition 65 warning unless the business demonstrates the exposure does not exceed the level. These thresholds are derived through the Proposition 65 statutory framework and are not equivalent to a food-safety reference value such as an EFSA tolerable intake or an EPA reference dose; comparing them requires accounting for the different regulatory functions and the route specificity.

How it compares

The Proposition 65 listing governs product warnings, whereas the State Water Resources Control Board MCL at California — Maximum Contaminant Level for Hexavalent Chromium in Drinking Water governs the permitted concentration of hexavalent chromium in California drinking water (10 µg/L). The two instruments operate on different legal mechanisms and are not interchangeable: a product may carry no Prop 65 warning yet the water used to make it may still be subject to the MCL, and vice versa. For the parallel Proposition 65 listings of other metals, see California Proposition 65 — Cadmium Listing and Maximum Allowable Daily Level, California Proposition 65 — Inorganic Arsenic Compounds Listing, and California Proposition 65 — Lead and Lead Compounds Listing.

Sources

• OEHHA Prop 65 Cr-VI — California Office of Environmental Health Hazard Assessment. Chromium (Hexavalent Compounds), Proposition 65 chemical listing and safe-harbor levels.

Page history

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