EPA Air Toxics 2000 — Nickel Compounds (Hazard Summary)
The U.S. Environmental Protection Agency’s Office of Air Quality Planning and Standards maintains a series of Air Toxics Hazard Summary fact sheets that consolidate the agency’s IRIS chemical assessments, the ATSDR Toxicological Profile, and CalEPA reference exposure levels into a one-document overview per hazardous air pollutant. This fact sheet is the nickel-and-nickel-compounds entry in that series. It was first issued in April 1992 and updated in January 2000; the health and regulatory values it cites were obtained in December 1999. Its content is fact-sheet-tertiary — it does not derive new toxicological values, but reports values established elsewhere (EPA IRIS for the oral RfD and inhalation unit risks; ATSDR for the chronic inhalation MRL; CalEPA for the chronic inhalation REL; NIOSH, ACGIH, and OSHA for occupational exposure limits). The fact sheet is the canonical EPA Air Toxics one-page reference for nickel compounds and remains the version posted on the agency’s public site under the URL slug nickle-compounds.pdf (the EPA URL retains a historical misspelling).
Summary
| Item | EPA Air Toxics 2000 Hazard Summary value |
|---|---|
| EPA cancer classification — nickel refinery dust | Group A (human carcinogen) |
| EPA cancer classification — nickel subsulfide | Group A (human carcinogen) |
| EPA cancer classification — nickel carbonyl | Group B2 (probable human carcinogen) |
| EPA cancer evaluation — soluble nickel salts | Not evaluated as a class for human carcinogenicity |
| Cancer target sites named (human studies) | Lung, nasal |
| EPA inhalation unit risk — nickel refinery dust | 2.4 × 10⁻⁴ per µg/m³ |
| EPA inhalation unit risk — nickel subsulfide | 4.8 × 10⁻⁴ per µg/m³ |
| Air concentration at 1-in-1,000,000 cancer risk (refinery dust) | 0.004 µg/m³ (4 × 10⁻⁶ mg/m³) |
| Air concentration at 1-in-1,000,000 cancer risk (subsulfide) | 0.002 µg/m³ (2 × 10⁻⁶ mg/m³) |
| EPA oral RfD — nickel, soluble salts | 0.02 mg/kg/day (basis: decreased body and organ weights in rats; medium confidence) |
| EPA inhalation RfC — nickel | Not established |
| ATSDR chronic inhalation MRL — nickel | 0.0002 mg/m³ (2 × 10⁻⁴ mg/m³) |
| CalEPA chronic inhalation REL — nickel | 0.00005 mg/m³ (5 × 10⁻⁵ mg/m³) |
| Critical-study NOAEL (respiratory effects, soluble nickel salt, rats) | 0.03 mg/m³ |
| NIOSH IDLH | 10 mg/m³ |
| ACGIH TLV — nickel metal compounds | 1.5 mg/m³ |
| OSHA PEL — nickel metal compounds | 1 mg/m³ |
| ACGIH TLV — soluble nickel | 0.1 mg/m³ |
| ACGIH TLV — insoluble nickel | 0.2 mg/m³ |
| NIOSH REL — nickel metal compounds | 0.015 mg/m³ |
| OSHA PEL / NIOSH REL — nickel carbonyl | 0.007 mg/m³ |
| Average adult dietary nickel intake (estimate) | 100–300 µg/day |
| Extrapolated daily nickel requirement (animal-data extrapolation) | 50 µg per kg diet, for a 70-kg person |
| Atomic weight | 58.71 g/mol |
| Air conversion factor (gaseous form, 25 °C) | 1 ppm = 2.4 mg/m³ |
| Fact-sheet date | Created April 1992; updated January 2000; values obtained December 1999 |
Provenance notes
Five-page PDF capture of the EPA Air Toxics Hazard Summary for nickel compounds, sourced from the EPA public site at the historical URL epa.gov/sites/default/files/2016-09/documents/nickle-compounds.pdf (the URL slug retains a misspelling of “nickel” that EPA has preserved across hosting migrations). The document explicitly identifies its own sources at the head of the fact sheet: EPA’s Integrated Risk Information System (IRIS is the parallel program; the nickel-specific IRIS chemical assessment files cited here are the IRIS entries for Nickel Carbonyl, Nickel Refinery Dust, Nickel Subsulfide, and Nickel Soluble Salts, all dated 1999), EPA’s 1986 Health Assessment Document for Nickel (EPA/600/8-83/012F), and the ATSDR Toxicological Profile for Nickel (the fact sheet cites the 1997 ATSDR update; the current ATSDR profile in this wiki is the 2024 update, which supersedes the 1997 edition).
Two cancer classifications are bundled in the fact sheet that the more recent agency literature splits differently. EPA’s Group-A “human carcinogen” determinations apply to nickel refinery dust (a mixture in which nickel subsulfide is the major constituent) and to nickel subsulfide itself. EPA’s Group-B2 “probable human carcinogen” determination applies to nickel carbonyl. Soluble nickel salts have not been evaluated by EPA as a class for human carcinogenicity. The IARC and California Prop 65 frameworks subsequently expanded coverage to “nickel and nickel compounds” as a class; see OEHHA Prop 65 2025 for the California position and ATSDR 2024 for the current carcinogenicity narrative.
The food/dietary nickel pathway appears only in two narrow contexts in this fact sheet: as a generic statement that food is the major source of human nickel exposure with an adult intake estimate of 100–300 µg/day, and as a one-line nutritional-requirement extrapolation from animal data (50 µg per kg diet for a 70-kg person). No matrix-specific occurrence values are presented. The fact sheet is calibrated to nickel as an inhalation/air-toxics hazard, consistent with its origin in the EPA Air Toxics Web Site.
The RfD of 0.02 mg/kg/day for nickel soluble salts is the value EPA IRIS has carried since 1986 and remains the operative US oral reference dose for nickel; the fact sheet’s “medium confidence” qualifier reflects the IRIS database’s documented concerns about the critical study (high control-group mortality) balanced against adequate supporting subchronic studies. EPA explicitly notes it has not established an inhalation RfC for nickel; the two values that fill that gap in the fact sheet — the ATSDR chronic inhalation MRL of 2 × 10⁻⁴ mg/m³ and the CalEPA chronic inhalation REL of 5 × 10⁻⁵ mg/m³ — are both anchored on the same critical-study NOAEL of 0.03 mg/m³ for respiratory effects in rats exposed to a soluble nickel salt, differing in the uncertainty factors each agency applied.
Implications
Certification: this fact sheet anchors the canonical US federal-and-California regulatory landscape for nickel as an air toxic and dietary trace metal as of December 1999, and the values it consolidates have remained operative in subsequent agency guidance. The 0.02 mg/kg/day oral RfD for soluble nickel salts is the relevant US federal reference value for dietary nickel exposure calibration; for a 70-kg adult this is 1,400 µg/day, which sits an order of magnitude above the fact sheet’s own 100–300 µg/day typical-adult-intake estimate. The CalEPA REL of 5 × 10⁻⁵ mg/m³ and ATSDR MRL of 2 × 10⁻⁴ mg/m³ are the operative inhalation reference values; EPA itself has not promulgated an RfC. The Group-A carcinogen determinations for nickel refinery dust and nickel subsulfide are the basis for occupational airborne-nickel exposure controls, not for dietary nickel certification.
Courses: useful as a one-page anchor explaining the US federal cancer classification structure for nickel (Group A for refinery dust and subsulfide; Group B2 for carbonyl; soluble salts unevaluated as a class) and the agency division of labour between EPA, ATSDR, CalEPA, NIOSH, ACGIH, and OSHA in setting nickel exposure values. The fact sheet is also a clean illustration of how a regulatory fact sheet packages primary IRIS, ATSDR, and CalEPA derivations into a consumer-and-regulator-facing summary.
App: low utility for product-level contamination benchmarking — the fact sheet supplies no matrix-specific occurrence values, no per-product nickel concentrations, and no consumption-frequency-modulated dietary nickel estimates. The 100–300 µg/day adult intake range is a generic anchor that downstream apps should defer to more granular dietary-exposure assessments (the EFSA CONTAM Panel 2020 update and matched national TDS values) rather than treat as a product-level benchmark.
Wiki pages updated on ingest
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.
| Commit | Date | Description |
|---|---|---|
| 9c0b0a7 | 2026-06-05 | codex fire 2026-06-05: no unclaimed auto-fetched pdfs |