California Proposition 65 — Nickel Listings (Cancer; Soluble Nickel Compounds Reproductive Toxicity)

Overview

Nickel appears on California’s Proposition 65 list in two separate registers. Nickel and nickel compounds are listed as carcinogens, and soluble nickel compounds are separately listed as reproductive toxicants, with nickel carbonyl listed for the developmental endpoint before the soluble-compounds determination. The practically important feature of the nickel listings, and the reason this page exists as a distinct regulation entry, is that California has adopted no oral safe-harbor level for nickel. The only Proposition 65 safe-harbor numbers for nickel are inhalation cancer No Significant Risk Levels (NSRLs) for two specific nickel forms; there is no Maximum Allowable Dose Level (MADL) for the reproductive-toxicity listing and no NSRL for elemental nickel or for nickel compounds as a class. For dietary nickel exposure the listing is therefore best described as “listed, no dietary safe-harbor”: the chemical is on the list, but no California number translates the listing into a food pass/fail threshold. The dietary nickel reference value lives in the European Food Safety Authority’s tolerable daily intake, not in Proposition 65 (EFSA 2020; EFSA — Nickel Tolerable Daily Intake (13 µg/kg b.w./day)).

Listing summary

The cancer listing covers nickel and nickel compounds as a class, with the carcinogenic target sites identified as the nasal cavity, paranasal sinus, and lungs (OEHHA 2025 fact sheet). The reproductive-toxicity listing is narrower than the cancer listing: it reaches only soluble nickel compounds and nickel carbonyl, not nickel metal or insoluble nickel compounds. A product containing nickel only as a metallic alloy or an insoluble form therefore does not trigger the reproductive-toxicity arm of Proposition 65 on the basis of nickel content alone (OEHHA 2025).

Reproductive-toxicity listing (soluble nickel compounds, 2018)

California Health and Safety Code 25249.5 et seq. requires the state to publish a list of chemicals known to cause cancer or reproductive toxicity. For reproductive toxicity the state’s qualified experts are the Developmental and Reproductive Toxicant Identification Committee (DARTIC) of OEHHA’s Science Advisory Board. The scientific basis for the soluble-nickel-compounds listing is the OEHHA hazard-identification document “Evidence on the Developmental and Reproductive Toxicity of Nickel and Nickel Compounds” (July 2018), prepared for the DARTIC deliberation held on 11 October 2018 (OEHHA 2018). Soluble nickel compounds were added to the list effective 26 October 2018 for both the developmental and the male-reproductive endpoints; nickel carbonyl had already been listed for the developmental endpoint before that deliberation.

The hazard-identification document’s critical findings are reductions in offspring viability and reductions in body weight of surviving offspring as the most sensitive and consistently reported developmental effects of prenatal nickel exposure in animal bioassays, together with human epidemiology associating ambient-air nickel-particle exposure with lower birth weight and, in two of three case-control studies, with autism spectrum disorders (OEHHA 2018). The dominant human exposure pathway the document examines is inhalation of nickel particles, not diet. That orientation is consistent with the reproductive/developmental critical effect underlying the EFSA chronic dietary TDI for nickel, which is post-implantation fetal loss in rats (EFSA 2020).

Cancer listing and safe-harbor levels

Nickel compounds were listed as a carcinogen effective 7 May 2004, with an earlier listing dated 1 October 1989; nickel metal and additional specific nickel compounds are also carried on the Proposition 65 carcinogen list (OEHHA 2025). OEHHA has published safe-harbor No Significant Risk Levels for only two specific nickel forms, both by the inhalation route: Nickel Refinery Dust at 0.8 µg/day and Nickel Subsulfide at 0.4 µg/day. No NSRL has been adopted for elemental nickel or for nickel compounds as a class, and no Maximum Allowable Dose Level has been adopted for the reproductive-toxicity listing by any route (safe-harbor list verified against OEHHA’s published Safe Harbor Levels table, 2026-06-22).

The consequence is that Proposition 65 supplies no oral dose threshold below which a business is relieved of the warning obligation for nickel. A business whose product causes a nickel exposure must either show the exposure poses no significant cancer risk and no observable reproductive effect through its own risk assessment, or provide a warning. There is no published California number that functions as a dietary nickel limit, which distinguishes nickel from cadmium and lead, where OEHHA has adopted oral MADLs that operate as de facto labeling thresholds (California Proposition 65 — Cadmium Listing and Maximum Allowable Daily Level; California Proposition 65 — Lead and Lead Compounds Listing).

Statutory meaning and what this page is not

Proposition 65 is a right-to-know labeling statute, not a food safety standard. A listing establishes a warning obligation; it does not set a maximum permissible concentration in food. Even where OEHHA adopts a MADL or NSRL, those values are statutory labeling triggers derived through fixed formulae (a 1,000-fold reproductive safety factor; a 1-in-100,000 lifetime cancer risk), not dose-response reference values in the EFSA TDI or EPA RfD sense. For nickel, no such California number exists for the oral route at all. This page records the existence and scope of the listings and the absence of an oral safe-harbor; it is not a basis for any dietary nickel threshold. The dietary nickel basis is the EFSA TDI of 13 µg Ni/kg body weight per day (EFSA — Nickel Tolerable Daily Intake (13 µg/kg b.w./day)), and the binding food maximum levels are the European Union’s, set by Commission Regulation (EU) 2024/1987 (Commission Regulation (EU) 2024/1987 — maximum levels of nickel in certain foodstuffs); the United States has set no nickel maximum level in food.

Sources

• OEHHA 2018 — OEHHA, July 2018. Evidence on the Developmental and Reproductive Toxicity of Nickel and Nickel Compounds (hazard-identification document prepared for the DARTIC deliberation of 11 October 2018, underlying the soluble-nickel-compounds reproductive-toxicity listing).
• OEHHA 2025 — OEHHA, February 2025. Nickel and Nickel Compounds, Proposition 65 Warnings Website fact sheet (listing scope, carcinogenic target sites, exposure routes).
• EFSA 2020 — the dietary nickel risk assessment that supplies the chronic TDI and the post-implantation-loss critical effect parallel to the OEHHA developmental basis.

Safe-harbor NSRL values (Nickel Refinery Dust 0.8 µg/day; Nickel Subsulfide 0.4 µg/day, inhalation) and the confirmation that no nickel MADL is listed were read from OEHHA’s published Proposition 65 Safe Harbor Levels table and the soluble-nickel-compounds listing record on 2026-06-22; exact cancer-listing dates for nickel metallic and individual nickel compounds should be read from the current OEHHA Proposition 65 list before use in a compliance decision.

References

Works cited in this page’s text, in first-appearance order. This is not the full corpus for this page; it is only what the prose above draws on. The complete set of sources is listed under Sources below. Each title links to its source record, which carries the ingest receipt, the extracted values, and the file hash of the document it was built from.

1. Update of the Risk Assessment of Nickel in Food and Drinking WaterEFSA Panel on Contaminants in the Food Chain (CONTAM) · EFSA Journal 2020;18(11):6268 · 2020 · doi.org/10.2903/j.efsa.2020.6268Government
2. Nickel and Nickel Compounds — Proposition 65 Warnings Website fact sheetCalifornia Office of Environmental Health Hazard Assessment · 2025 · www.p65warnings.ca.govGovernment
3. Evidence on the Developmental and Reproductive Toxicity of Nickel and Nickel Compounds (Proposition 65 hazard-identification document)California Office of Environmental Health Hazard Assessment, Reproductive and Cancer Hazard Assessment Branch · OEHHA, California Environmental Protection Agency; hazard-identification document prepared for the Developmental and Reproductive Toxicant Identification Committee (DARTIC), July 2018 · 2018 · oehha.ca.govGovernment

Update history

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