Carcinogens: Tobacco, Alcohol & UV Radiation — WHO Group 1 Classification

The WHO/IARC classifies tobacco, alcohol, and UV radiation as Group 1 carcinogens — sufficient evidence of carcinogenicity in humans.

Tobacco

• 7,000+ chemicals; ≥70 known carcinogens (PAHs, N-nitrosamines, aromatic amines, benzene, arsenic, cadmium, formaldehyde).
• Causes: lung, larynx, oral, esophageal, pancreatic, bladder, kidney, cervical, AML, more.
• Mechanism: DNA adducts, mutations (TP53, KRAS), chronic inflammation, immune suppression.

Alcohol

• Ethanol → acetaldehyde (Group 1) via ADH/CYP2E1.
• Acetaldehyde: DNA adducts, crosslinks, impaired repair.
• Also: oxidative stress, folate disruption, estrogen ↑, microbiome alteration.
• Causes: oral, pharyngeal, laryngeal, esophageal, liver, colorectal, breast.
• No safe threshold; risk dose-dependent.

Ultraviolet (UV) Radiation

• UVA (315–400 nm): deeper penetration, oxidative damage, photoaging.
• UVB (280–315 nm): direct DNA damage (CPDs, 6-4PPs), sunburn, carcinogenesis.
• Causes: melanoma, BCC, SCC, Merkel cell, ocular melanoma.
• Tanning beds = Group 1.

Synergy

Tobacco + alcohol = multiplicative risk for upper aerodigestive cancers. UV + immunosuppression = aggressive skin cancer.

Prevention: tobacco cessation, alcohol minimization, broad-spectrum SPF 30+, shade, protective clothing, avoid tanning beds.