Food & Drink / Compounds / Cobalt(II) oxide (CoO)

Cobalt(II) oxide (CoO) in food: ingestion safety

Moderate risk

Not medical or professional safety advice, and not a substitute for a qualified clinician — consult one. Full disclaimer →

Low_to_moderate risk based on available hazard data.

What is cobalt(ii) oxide (coo)?

Also known as: Cobalt [II] oxide, Cobalt(II) oxide, Cobaltous oxide, Cobalt monoxide.

CAS number
1307-96-6
Molecular formula
CoO
Molecular weight
74.933 g/mol
SMILES
[Co+2].[O-2]

Risk for people from eating or drinking it

Moderate risk

Low_to_moderate risk based on available hazard data.

Regulatory consensus

2 regulatory and scientific bodies have classified Cobalt(II) oxide (CoO). The classifications differ — that's the data.

AgencyYearClassificationNotes
IARC2023Group 2B (possibly carcinogenic to humans)IARC Monographs Volume 131 (2022 evaluation, published 2023) evaluated cobalt(II) oxide (CoO, CAS 1307-96-6) as an agent in its own right and classified it Group 2B on the basis of sufficient evidence for cancer in experimental animals; evidence in humans was inadequate. Cobalt(II,III) oxide (Co3O4) was evaluated separately in the same volume and received a different, lower classification — the two oxides are not interchangeable, which is the distinction D-366 split this record out to preserve. Co3O4 is a separate corpus record (hq-c-ino-000095) carrying its own CAS and its own group.
CalEPA1992Listed by OEHHA under California Proposition 65 as known to the State to cause cancerOEHHA Proposition 65 list, edition 2025-12-05: "Cobalt [II] oxide", CAS 1307-96-6, toxicity "cancer", listing mechanism AB (Authoritative Bodies), effective 1992-07-01. Corroborates the record's own regulatory.listings.california_prop65 block, which D-366 verified against the same edition but never expressed as a classification row.

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 you encounter cobalt(ii) oxide (coo)

  • Contaminated Water — Mining site runoff, Industrial discharge, Old infrastructure
  • Food Chain — Fish from contaminated waters, Crops in contaminated soil

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Cobalt(II) oxide (CoO):

  • Mineral-based or plant-derived pigments
    Trade-offs: Narrower color range. May fade faster than synthetic pigments.
    Relative cost: 2-5× conventional

Frequently asked questions

Is cobalt(ii) oxide (coo) safe for you?

Low_to_moderate risk based on available hazard data.

What products contain cobalt(ii) oxide (coo)?

Cobalt(II) oxide (CoO) appears in: Mining site runoff (Contaminated water); Industrial discharge (Contaminated water); Fish from contaminated waters (Food chain); Crops in contaminated soil (Food chain).

See Cobalt(II) oxide (CoO) in the food app

Look up products containing cobalt(ii) oxide (coo), compare to alternatives, and explore the full data record.

Open in food View raw API data

Sources (3)
  1. IARC Monographs Volume 131: Cobalt, Antimony Compounds, and Weapons-grade Tungsten Alloy — Cobalt(II) Oxide Group 2B (2022 evaluation, published 2023) (2023) — regulatory
  2. ATSDR Toxicological Profile for Cobalt (October 2024) — Chemical and Physical Information (2024) — reference
  3. OEHHA Proposition 65 list — Cobalt [II] oxide (CAS 1307-96-6), cancer, 1992 — regulatory

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for medical, legal, or regulatory advice. Why we built ALETHEIA →