IARC Monograph 100C (2012) — Nickel and Nickel Compounds

This is the International Agency for Research on Cancer’s authoritative carcinogenicity evaluation of nickel and nickel compounds, published as a chapter of Monographs Volume 100C, the “Review of Human Carcinogens” re-evaluation of agents previously classified by IARC. Nickel had been considered by earlier Working Groups in 1972, 1975, 1979, 1982, 1987, and 1989; this 2012 reassessment incorporates the human epidemiology, animal bioassay, and mechanistic literature that accumulated since. The Working Group concluded that there is sufficient evidence in humans for the carcinogenicity of mixtures that include nickel compounds and nickel metal, with the evidence strongest for soluble nickel compounds and independent evidence for oxidic and sulfidic nickel compounds; these agents cause cancers of the lung and of the nose and nasal sinuses. The overall classification is that nickel compounds are carcinogenic to humans (Group 1). The monograph is primarily an inhalation-and-occupational carcinogenicity document, but its Section 1.5.3 compiles dietary nickel concentrations across food categories, which is the part most directly relevant to a food-and-supply-chain wiki.

Key numbers

Classification and target organs (Section 5, Evaluation):

• Nickel compounds are carcinogenic to humans, Group 1. There is sufficient evidence in humans for the carcinogenicity of mixtures that include nickel compounds and nickel metal; the evidence is strongest for soluble nickel compounds, with independent evidence for oxidic and sulfidic nickel compounds. Target sites: cancers of the lung and of the nose and nasal sinuses. This Group 1 statement is the only carcinogenicity classification printed in the 100C chapter’s Evaluation.
• On metallic nickel, the 100C Working Group judged that separately excluding metallic-nickel studies from the cancer review was not warranted because nickel metal dust can become solubilized and bioavailable after inhalation (Section 2.1). The standing IARC classification of metallic (elemental) nickel as Group 2B (possibly carcinogenic to humans) derives from the earlier IARC 1990 evaluation (Chromium, Nickel and Welding); 100C does not itself print a Group 2B designation for metallic nickel.
• Sufficient evidence in experimental animals: nickel monoxides, nickel hydroxides, nickel sulfides (including nickel subsulfide), nickel acetate, and nickel metal.
• Limited evidence in animals: nickelocene, nickel carbonyl, nickel sulfate, nickel chloride, nickel arsenides, nickel antimonide, nickel selenides, nickel sulfarsenide, nickel telluride.
• Inadequate evidence in animals: nickel titanate, nickel trioxide, amorphous nickel sulfide.

Dietary exposure (Section 1.5.3):

• Nickel in foodstuffs is measured as “total nickel.” Average concentrations are in the range 0.01–0.1 mg/kg, but can reach 8–12 mg/kg in certain foods (EVM 2002; WHO 2007).
• Highest mean concentrations reported (µg/g): cocoa beans 9.8; soyabeans 5.2; soya products 5.1; walnuts 3.6; peanuts 2.8; oats 2.3; buckwheat 2.0; oatmeal 1.8.
• Reported ranges by food category: grains, vegetables and fruits 0.02–2.7 µg/g; meats 0.06–0.4 µg/g; seafood 0.02–20 µg/g; dairy < 100 µg/L.
• US daily dietary intake estimates: 101–162 µg/day for adults; 136–140 µg/day for males; 107–109 µg/day for females. Pregnant women average 121 µg/day, lactating women 162 µg/day (ATSDR 2005). Diet is reported to contribute less than 0.2 mg/day (WHO 2007).
• Ingestion of nickel in food, and to a lesser degree drinking-water, is the primary route of exposure for the non-smoking general population.

Lung-cancer epidemiology (Table 2.2, Andersen et al. 1996; multivariate Poisson regression, Norwegian refinery cohort):

• Soluble nickel, relative risk of lung cancer by mean cumulative exposure (mg/m³): < 1 → 1.0 (referent); 1–4 → 1.2 (95% CI 0.8–1.9); 5–14 → 1.6 (1.0–2.8); ≥ 15 → 3.1 (2.1–4.8); test for linear trend P < 0.001.
• Nickel oxide: < 1 → 1.0 (referent); 1–4 → 1.0 (0.6–1.5); 5–14 → 1.6 (1.0–2.5); ≥ 15 → 1.5 (1.0–2.2); P = 0.05.

Environmental and other occurrence:

• Nickel is the 24th most abundant element, ~0.008% of the earth’s crust. Soil concentration ~79 ppm (range 4–80 ppm).
• Air: rural and urban ambient 5–35 ng/m³; remote areas 1–3 ng/m³.
• Water: average reported concentrations ~< 20 µg/L (groundwater), 0.1–0.5 µg/L (seawater), 15–20 µg/L (surface water); up to 980 µg/L in groundwater at pH < 6.2.
• General-population non-dietary intakes are minor: inhalation of ambient air contributes < 0.05 µg/day (USA) up to ~122 µg/day only at the highest reported ambient concentration (Copper Cliff, Ontario).

Mechanism (Section 4.3, Synthesis):

• The ultimate carcinogenic species in nickel carcinogenesis is the nickel ion, Ni(II). Soluble nickel enters cells via ion channels and transporters; poorly water-soluble particulate compounds enter by phagocytosis and gradually release Ni(II) intracellularly.
• Nickel compounds are not mutagenic in bacteria and only weakly mutagenic in mammalian cells under standard procedures, but induce DNA damage, chromosomal aberrations, and micronuclei in vitro and in vivo; delayed mutagenicity and chromosomal instability appear long after treatment. Disturbance of DNA repair, epigenetic changes (altered DNA methylation, histone modification), and inflammation are proposed mechanisms.

Provenance notes

Fifty-page PDF of the Nickel and Nickel Compounds chapter (printed pages 169–218) of IARC Monographs Volume 100C, “Arsenic, Metals, Fibres, and Dusts” (Lyon, 2012). The chapter PDF was retrieved 2026-06-22 from a public mirror because the historical monographs.iarc.fr/ENG/Monographs/vol100C/mono100C-10.pdf path returns 404 after the IARC site reorganisation; the canonical landing page for the volume is https://publications.iarc.who.int/120. Content was verified against the IARC NCBI Bookshelf record (NBK304378). No DOI is assigned to IARC monograph chapters.

This source was surfaced because the OEHHA Prop 65 nickel fact sheet names IARC Monograph Vol. 100C as one of its underlying scientific sources, and it was not previously ingested. The only prior IARC-authored nickel page in the corpus is the 1990 chromium/nickel/welding monograph (Chromium, Nickel and Welding); this 2012 100C re-evaluation supersedes the nickel evaluation in that earlier volume for classification purposes.

Implications

Certification: IARC Group 1 is the highest carcinogenicity classification and is the international anchor for treating nickel and nickel compounds as a carcinogen of concern. The classification is driven by inhalation/occupational lung and nasal cancer, not by dietary exposure; the monograph explicitly notes that no tumours were observed in oral animal carcinogenicity studies and that the general-population cancer concern is dominated by the respiratory route. This matters for any HMTc-adjacent analysis: nickel’s Group 1 status is a respiratory-carcinogen finding, while the food-relevant systemic toxicity endpoints (reproductive/developmental effects, contact dermatitis elicitation) are governed by the EFSA TDI derivation (Scientific Opinion on the risks to public health related to the presence of nickel in food and drinking water, Update of the Risk Assessment of Nickel in Food and Drinking Water) rather than by this carcinogenicity classification.

Courses: useful as the canonical citation for “nickel is an IARC Group 1 carcinogen,” with the important qualifier that this is an inhalation/occupational finding, and as a source of food-category nickel concentration benchmarks (cocoa, soy, nuts, oats highest among common foods).

App: the Section 1.5.3 food-category concentration figures (cocoa beans 9.8 µg/g, soyabeans 5.2, walnuts 3.6, peanuts 2.8, oats 2.3) are useful order-of-magnitude priors for nickel contamination likelihood by ingredient, though they are coarse literature averages, not matrix-specific occurrence distributions.

Verification notes

Fresh-context audit subagent (2026-06-22) confirmed numerical fidelity across all Key-numbers figures (food-category concentrations, daily-intake estimates, Table 2.2 lung-cancer relative risks and CIs, environmental occurrence) against the PDF with no transposition, no invented taxonomy slug, and no brand- or HMTc-firewall violation. One finding applied: the “metallic nickel = Group 2B” designation was reattributed to the standing IARC classification / IARC 1990 evaluation because the 100C chapter prints only the Group 1 classification for nickel compounds and does not itself state a Group 2B figure for metallic nickel (verified against Section 5 Evaluation, printed pp. 210–211). Verdict: REVISE → corrected.

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