What is IARC Group 1?
Group 1 — carcinogenic to humans. 74 factors in the Meyron reference are currently classified this way.
Plain-language explanation
Strong evidence that this can cause cancer in humans. Examples: smoking, alcohol, UV radiation.
Examples
Aflatoxins
Infection. Spread through contaminated food and water in regions where storage conditions favour Aspergillus mould — most commonly in tropical and subtropical staple crops (peanuts, maize, tree nuts).
Alcoholic beverages
Eaten and drunk. Beer, wine, spirits — risk rises with the amount consumed.
Asbestos
Breathed. Older insulation, ceiling tiles, vinyl flooring, vehicle brake pads, and some industrial products. Most current exposure comes from disturbing legacy materials during renovation.
Benzene
Breathed. Gasoline vapours at the pump, vehicle exhaust, cigarette smoke, and occupational exposure in petrochemicals.
Combined menopausal hormone therapy
Prescription medication. Used to manage menopausal symptoms.
Combined oral contraceptives
Prescription medication. Most widely used reversible contraceptive worldwide.
Diesel engine exhaust
Breathed. Roadside air, fuelling stations, and occupational exposure in mining, transport, and mechanic work.
Epstein-Barr virus (EBV)
Infection. Spread through saliva; most adults are infected without symptoms. No vaccine yet.
Formaldehyde
Breathed. Off-gassing from particleboard, plywood, and other pressed-wood products; embalming fluids; some hair-smoothing salon treatments; certain manufacturing.
Helicobacter pylori
Infection. Lives in the stomach lining of about half the global population; passes between people, often in childhood. Testable and treatable with antibiotics.
Reading IARC classifications carefully
The IARC groups describe the strength of evidence that an agent can cause cancer under some conditions — not the size of the risk to any individual, not the dose required, and not how likely exposure is in everyday life. A Group 1 classification does not mean an exposure is unavoidable or catastrophic; a Group 3 classification does not mean it is safe.