Hexavalent chromium (Cr(VI)) in the yard and garden
Moderate risk for your yardHexavalent chromium (Cr(VI), chromate/dichromate) is one of the most potent occupational and environmental carcinogens — IARC classifies Cr(VI) compounds as Group 1 (carcinogenic to humans), confirmed in Volume 100C (2012), based on definitive evidence for lung cancer in chromate production, plating, and pigment workers, and for nasal/sinus cancer. Cr(VI) is genotoxic: it enters cells via sulfate transporters, is reduced intracellularly to Cr(III) generating reactive oxygen species and Cr-DNA adducts (Cr-guanine crosslinks, oxidized bases) that cause strand breaks and mutations. The EPA IRIS classifies Cr(VI) as carcinogenic by inhalation (slope factor 42 (mg/kg/day)⁻¹ — among the highest of regulated metals). EPA's SDWA MCL for total chromium in drinking water is 100 μg/L; however, this covers both trivalent Cr(III) (nutritionally essential, low toxicity) and Cr(VI) without distinction. California established a specific Cr(VI) MCL of 10 μg/L in 2014, and EPA proposed a federal Cr(VI)-specific MCL in its 2023 NPDWR rulemaking. Cr(VI) contamination of groundwater from industrial disposal (electroplating, leather tanning, steel manufacturing, chromate chemical plants) is widespread across the US and globally. The Hinkley, California contamination case (Erin Brockovich) made hexavalent chromium groundwater contamination broadly recognized.
What is hexavalent chromium (cr(vi))?
The IUPAC name is chromium(6+).
Also known as: chromium(6+), Chromium hexavalent ion, Chromium(6+) ion, Cr(VI).
- IUPAC name
- chromium(6+)
- CAS number
- 18540-29-9
- Molecular formula
- Cr+6
- Molecular weight
- 51.996 g/mol
- SMILES
- [Cr+6]
- PubChem CID
- 29131
Risk for people, pets,
Moderate riskHexavalent chromium (Cr(VI), chromate/dichromate) is one of the most potent occupational and environmental carcinogens — IARC classifies Cr(VI) compounds as Group 1 (carcinogenic to humans), confirmed in Volume 100C (2012), based on definitive evidence for lung cancer in chromate production, plating, and pigment workers, and for nasal/sinus cancer. Cr(VI) is genotoxic: it enters cells via sulfate transporters, is reduced intracellularly to Cr(III) generating reactive oxygen species and Cr-DNA adducts (Cr-guanine crosslinks, oxidized bases) that cause strand breaks and mutations. The EPA IRIS classifies Cr(VI) as carcinogenic by inhalation (slope factor 42 (mg/kg/day)⁻¹ — among the highest of regulated metals). EPA's SDWA MCL for total chromium in drinking water is 100 μg/L; however, this covers both trivalent Cr(III) (nutritionally essential, low toxicity) and Cr(VI) without distinction. California established a specific Cr(VI) MCL of 10 μg/L in 2014, and EPA proposed a federal Cr(VI)-specific MCL in its 2023 NPDWR rulemaking. Cr(VI) contamination of groundwater from industrial disposal (electroplating, leather tanning, steel manufacturing, chromate chemical plants) is widespread across the US and globally. The Hinkley, California contamination case (Erin Brockovich) made hexavalent chromium groundwater contamination broadly recognized.
Regulatory consensus
10 regulatory and scientific bodies have classified Hexavalent chromium (Cr(VI)). The classifications differ — that's the data.
| Agency | Year | Classification | Notes |
|---|---|---|---|
| EPA CTX / NIOSH | — | potential occupational carcinogen | |
| EPA CTX / IRIS | — | D (Not classifiable as to human carcinogenicity) | |
| EPA CTX / IRIS | — | Known/likely human carcinogen | |
| EPA CTX / IRIS | — | Carcinogenic potential cannot be determined | |
| EPA CTX / IRIS | — | A (Human carcinogen) | |
| EPA CTX / NTP RoC | — | Known Human Carcinogen | |
| EPA CTX / IARC | — | Group 1 - Carcinogenic to humans | |
| EPA CTX / Health Canada | — | Group I: CEPA (carcinogenic to humans) | |
| EPA CTX / EPA OPP | — | Group A Human Carcinogen by Inhalation | |
| EPA CTX / Skin-Eye | — | Skin Sensitization: Sh (score: high) |
Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.
Where your yard encounter hexavalent chromium (cr(vi))
- Contaminated Water — Mining site runoff, Industrial discharge areas, Drinking water from old infrastructure
- Soil Contamination — Industrial sites, Smelter areas, Battery recycling facilities
- Food Chain — Fish from contaminated waters, Shellfish from polluted areas, Crops grown in contaminated soil
Safer alternatives
Lower-risk approaches that achieve a similar outcome to Hexavalent chromium (Cr(VI)):
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Process controls to minimize degradant formation
Trade-offs: Additional manufacturing costRelative cost: 1.2-2×
Frequently asked questions
Is hexavalent chromium (cr(vi)) safe for your yard?
Hexavalent chromium (Cr(VI), chromate/dichromate) is one of the most potent occupational and environmental carcinogens — IARC classifies Cr(VI) compounds as Group 1 (carcinogenic to humans), confirmed in Volume 100C (2012), based on definitive evidence for lung cancer in chromate production, plating, and pigment workers, and for nasal/sinus cancer. Cr(VI) is genotoxic: it enters cells via sulfate transporters, is reduced intracellularly to Cr(III) generating reactive oxygen species and Cr-DNA adducts (Cr-guanine crosslinks, oxidized bases) that cause strand breaks and mutations. The EPA IRIS classifies Cr(VI) as carcinogenic by inhalation (slope factor 42 (mg/kg/day)⁻¹ — among the highest of regulated metals). EPA's SDWA MCL for total chromium in drinking water is 100 μg/L; however, this covers both trivalent Cr(III) (nutritionally essential, low toxicity) and Cr(VI) without distinction. California established a specific Cr(VI) MCL of 10 μg/L in 2014, and EPA proposed a federal Cr(VI)-specific MCL in its 2023 NPDWR rulemaking. Cr(VI) contamination of groundwater from industrial disposal (electroplating, leather tanning, steel manufacturing, chromate chemical plants) is widespread across the US and globally. The Hinkley, California contamination case (Erin Brockovich) made hexavalent chromium groundwater contamination broadly recognized.
What products contain hexavalent chromium (cr(vi))?
Hexavalent chromium (Cr(VI)) appears in: Mining site runoff (Contaminated water); Industrial discharge areas (Contaminated water); Industrial sites (Soil contamination); Smelter areas (Soil contamination); Fish from contaminated waters (Food chain).
Why do regulators disagree about hexavalent chromium (cr(vi))?
Hexavalent chromium (Cr(VI)) has been classified by 10 agencies including EPA CTX / NIOSH, EPA CTX / IRIS, EPA CTX / IRIS, EPA CTX / IRIS, EPA CTX / IRIS, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.
See Hexavalent chromium (Cr(VI)) in the outdoor app
Look up products containing hexavalent chromium (cr(vi)), compare to alternatives, and explore the full data record.
Open in outdoor View raw API dataSources (2)
- IARC Monographs Volume 100C: Arsenic, Metals, Fibres and Dusts — Chromium (VI) Compounds Group 1 (Lung Cancer, Nasal/Sinus Cancer), Nickel Compounds Group 1, Beryllium Group 1 (2012) (2012) — regulatory
- US EPA: National Primary Drinking Water Regulations — Inorganic Chemicals (40 CFR 141.62); Total Chromium MCL 100 μg/L, Barium MCL 2 mg/L, Uranium MCL 30 μg/L, Selenium MCL 50 μg/L, Manganese SMCL 50 μg/L (1992) — regulatory
Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →