Pet Safety / Compounds / Chlorpyrifos

Is Chlorpyrifos safe for dogs and cats?

Moderate risk for pets

Neurotoxicant; tremors, salivation; avoid agricultural areas and old flea collars.

What is chlorpyrifos?

The IUPAC name is diethoxy-sulfanylidene-[(3,5,6-trichloro-2-pyridinyl)oxy]-lambda5-phosphane.

Also known as: diethoxy-sulfanylidene-[(3,5,6-trichloro-2-pyridinyl)oxy]-lambda5-phosphane, Dursban, Chlorpyriphos, Lorsban.

IUPAC name
diethoxy-sulfanylidene-[(3,5,6-trichloro-2-pyridinyl)oxy]-lambda5-phosphane
CAS number
2921-88-2
Molecular formula
C9H11Cl3NO3PS
Molecular weight
350.6 g/mol
SMILES
CCOP(=S)(OCC)OC1=NC(=C(C=C1Cl)Cl)Cl
PubChem CID
2730

Risk for dogs

Moderate risk

Neurotoxicant; tremors, salivation; avoid agricultural areas and old flea collars.

Risk for cats

Elevated risk

More sensitive than dogs (CYP450 differences); topical products historically caused deaths.

Regulatory consensus

10 regulatory and scientific bodies have classified Chlorpyrifos. The classifications differ — that's the data.

AgencyYearClassificationNotes
US EPA—not likely carcinogenprimary concern: acetylcholinesterase inhibition; crop residue in food
EPA CTX / EPA OPP—Group E Evidence of Non-carcinogenicity for Humans
EPA CTX / Genetox—Genotoxicity: negative (Ames: negative, 2 positive / 4 negative reports)
EPA CTX / Genetox—Genotoxicity: negative (Ames: negative, 2 positive / 4 negative reports)
EPA CTX / Skin-Eye—Eye Irritation: Category 2B (score: moderate)
EPA CTX / Skin-Eye—Skin Irritation: Not classified (score: low)
EPA CTX / Skin-Eye—Eye Irritation: Category 6.4A (Category 2A) (score: high)
EPA CTX / Skin-Eye—Skin Irritation: Category 6.3B (Category 3) (score: moderate)
US_EPA2021banned_food_useEPA revoked all food-use tolerances.
EU_REACH2020bannedEU non-renewal of approval.

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 pets encounter chlorpyrifos

  • Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
  • Occupational Environments — Factories, Warehouses, Transportation vehicles

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Chlorpyrifos:

  • Physical/mechanical pest control (IPM)
    Trade-offs: More labor-intensive. May not be sufficient for severe infestations.
    Relative cost: Variable; lower long-term
  • Spinosad
    Relative cost: 1.2-2×
  • Bt (Bacillus thuringiensis)
    Relative cost: 1.2-2×
  • Neem oil
    Relative cost: 1.2-2×
  • Beneficial insects
    Relative cost: 1.2-2×

Frequently asked questions

Is chlorpyrifos safe for pets?

Neurotoxicant; tremors, salivation; avoid agricultural areas and old flea collars.

What products contain chlorpyrifos?

Chlorpyrifos appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments).

Why do regulators disagree about chlorpyrifos?

Chlorpyrifos has been classified by 10 agencies including US EPA, EPA CTX / EPA OPP, EPA CTX / Genetox, EPA CTX / Genetox, EPA CTX / Skin-Eye, 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 Chlorpyrifos in the pets app

Look up products containing chlorpyrifos, compare to alternatives, and explore the full data record.

Open in pets View raw API data

Sources (1)
  1. US EPA: Chlorpyrifos — Revocation of Food Tolerances (2021) — 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 →