Pet Safety / Compounds / Endrin

Is Endrin safe for dogs and cats?

Extreme risk for pets

Endrin is extremely acutely toxic to dogs — more so than aldrin or dieldrin on a weight basis. Canine LD50 values for organochlorine cyclodienes place endrin as the most acutely dangerous of the three. GABA-A receptor antagonism produces rapid-onset seizures with minimal warning signs; death can follow within hours. Dogs at legacy-contaminated sites (former agricultural areas, pesticide storage facilities) are at risk from soil and vegetation ingestion. Treatment requires emergency seizure management (diazepam, phenobarbital) and intensive supportive care; prognosis is grave in severe poisoning. ASPCA APCC identifies endrin as an extreme acute hazard in companion animals.

What is endrin?

The IUPAC name is (1R,2R,3R,6S,7S,8S,9S,11R)-3,4,5,6,13,13-hexachloro-10-oxapentacyclo[6.3.1.13,6.02,7.09,11]tridec-4-ene.

Also known as: (1R,2R,3R,6S,7S,8S,9S,11R)-3,4,5,6,13,13-hexachloro-10-oxapentacyclo[6.3.1.13,6.02,7.09,11]tridec-4-ene, Hexadrin, Mendrin, Nendrin.

IUPAC name: (1R,2R,3R,6S,7S,8S,9S,11R)-3,4,5,6,13,13-hexachloro-10-oxapentacyclo[6.3.1.13,6.02,7.09,11]tridec-4-ene
CAS number: 72-20-8
Molecular formula: C12H8Cl6O
Molecular weight: 380.9 g/mol
SMILES: C1C2C3C(C1C4C2O4)C5(C(=C(C3(C5(Cl)Cl)Cl)Cl)Cl)Cl
PubChem CID: 12358480

Risk for dogs

Extreme risk

Risk for cats

Extreme risk

Cats' sensitivity to GABA-A antagonists combined with endrin's high acute toxicity makes this combination particularly dangerous. The rapid onset of seizures in feline endrin poisoning gives minimal time for intervention. Cats in areas with legacy endrin contamination may also be exposed through predation on small mammals and birds that have bioaccumulated endrin residues. Treatment is symptomatic and intensive; prognosis is poor in animals presenting with established seizures. The extreme rating reflects both the intrinsic feline sensitivity and endrin's position as the most acutely toxic cyclodiene.

Regulatory consensus

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

Agency	Year	Classification
UNEP	—	Persistent Organic Pollutant (POP)
EPA CTX / IRIS	—	D (Not classifiable as to human carcinogenicity)
EPA CTX / IARC	—	Group 3 - Not classifiable as to its carcinogenicity to humans
EPA CTX / EPA OPP	—	Group D Not Classifiable as to Human Carcinogenicity
EPA CTX / Genetox	—	Genotoxicity: negative (Ames: negative, 0 positive / 5 negative reports)
EPA CTX / Genetox	—	Genotoxicity: negative (Ames: negative, 0 positive / 5 negative reports)

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 endrin

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 Endrin:

Physical/mechanical pest control (IPM)
Trade-offs: More labor-intensive. May not be sufficient for severe infestations.

Relative cost: 1.2-2×

Frequently asked questions

Is endrin safe for pets?

What products contain endrin?

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

Why do regulators disagree about endrin?

Endrin has been classified by 6 agencies including UNEP, EPA CTX / IRIS, EPA CTX / IARC, EPA CTX / EPA OPP, EPA CTX / Genetox, 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 Endrin in the pets app

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

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Sources (3)

IARC Monographs Volume 20: Endrin — Group 3 (not classifiable as to carcinogenicity in humans); acute toxicity data; human poisoning episodes (1979) — iarc_monograph
US EPA IRIS: Endrin — Oral Reference Dose, Cancer Classification D (not classifiable), Ambient Water Quality Criterion 0.036 μg/L chronic freshwater (1988) — regulatory
ATSDR Toxicological Profile for Endrin — Acute Neurotoxicity, Human Poisoning Incidents, Aquatic Toxicity, Wildlife Impacts, Soil Persistence (1996) — 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 →