Outdoor & Yard / Compounds / Chromium(VI) / Hexavalent Chromium

Chromium(VI) / Hexavalent Chromium in the yard and garden

High risk for your yard

Chromium(VI) is a known human carcinogen primarily via inhalation exposure, causing lung and nasopharyngeal cancers in occupational settings. Ingestion of Cr(VI) in drinking water poses potential carcinogenic risk. Reproductive and developmental toxicity documented in animal studies at occupational exposure levels.

What is chromium(vi) / hexavalent chromium?

CAS number
18540-29-1
Molecular formula
Cr+6
Molecular weight
51.996 g/mol
SMILES
[Cr+6]
PubChem CID
29131

Risk for people, pets,

High risk

Chromium(VI) is a known human carcinogen primarily via inhalation exposure, causing lung and nasopharyngeal cancers in occupational settings. Ingestion of Cr(VI) in drinking water poses potential carcinogenic risk. Reproductive and developmental toxicity documented in animal studies at occupational exposure levels.

Regulatory consensus

3 regulatory and scientific bodies have classified Chromium(VI) / Hexavalent Chromium. The classifications differ — that's the data.

AgencyYearClassificationNotes
IARC1990Group 1 (Carcinogenic to humans)Classification based on sufficient evidence of carcinogenicity in humans via inhalation; lung and nasopharyngeal cancers documented in occupational cohorts
US EPA2008Likely carcinogen (inhalation); potential carcinogen (ingestion)EPA established interim chromium(VI)-specific maximum contaminant level evaluation; final MCL status remains unresolved as of 2024. Occupational exposure limits: OSHA PEL 5 µg/m³ (1990), NIOSH REL 1 µg/m³ (recommended, not mandatory)
NTP1998Known carcinogenListed in 12th Report on Carcinogens based on sufficient evidence of carcinogenicity in animal studies and human occupational exposures

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 chromium(vi) / hexavalent chromium

  • 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 Chromium(VI) / Hexavalent Chromium:

  • Trivalent chromium (Cr(III)) passivation
    Trade-offs: Direct Cr(VI) replacement for corrosion protection. Appearance: slight yellow vs clear/blue. Corrosion resistance: 90-95% of Cr(VI) for most applications. Salt spray test 168-720 hrs. Cost: 10-20% higher per bath but lower waste treatment costs.
    Relative cost: 1.2-2×
  • Zinc-nickel alloy plating
    Trade-offs: Superior corrosion resistance to Cr(VI) passivated zinc (1000+ hrs salt spray). No hexavalent chromium at any process step. Higher bath maintenance cost. Excellent for automotive.
    Relative cost: 1.2-2×
  • Silane/siloxane-based conversion coatings
    Trade-offs: Chrome-free, non-toxic. Excellent paint adhesion. Corrosion resistance varies (moderate standalone). Works as primer for powder coating. Lower waste disposal costs.
    Relative cost: 1.2-2×

Frequently asked questions

Is chromium(vi) / hexavalent chromium safe for your yard?

Chromium(VI) is a known human carcinogen primarily via inhalation exposure, causing lung and nasopharyngeal cancers in occupational settings. Ingestion of Cr(VI) in drinking water poses potential carcinogenic risk. Reproductive and developmental toxicity documented in animal studies at occupational exposure levels.

What products contain chromium(vi) / hexavalent chromium?

Chromium(VI) / Hexavalent Chromium 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 chromium(vi) / hexavalent chromium?

Chromium(VI) / Hexavalent Chromium has been classified by 3 agencies including IARC, US EPA, NTP, 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 Chromium(VI) / Hexavalent Chromium in the outdoor app

Look up products containing chromium(vi) / hexavalent chromium, compare to alternatives, and explore the full data record.

Open in outdoor View raw API data

Sources (6)
  1. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans — Chromium, Nickel and Welding (Volume 49) (1990) — regulatory
  2. US EPA Integrated Risk Information System (IRIS) — Chromium(VI) (2008) — regulatory
  3. National Toxicology Program — 12th Report on Carcinogens (1998) — regulatory
  4. US EPA Chromium(VI) Drinking Water Evaluation — Unfinalized MCL Status (2024) — regulatory
  5. OSHA Chromium(VI) Occupational Exposure Standard — 29 CFR 1910.1026 (1990) — regulatory
  6. Occupational Exposure to Chromium(VI) — Cancer Risk Characterization in Chromate Production and Welding Workers (2020) — research

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 →