Reference summary — not medical advice or a personal risk estimate.
Tobacco smoking
Quick answer
Classified as Group 1 — carcinogenic to humans, based on sufficient evidence in humans. Inhaled. Smoking cigarettes, cigars, pipes, water pipes, and other forms of burning tobacco.
Summary
The leading preventable cause of cancer worldwide. Associated with cancers across many organs.
Detail
Tobacco smoking is Group 1 with sufficient evidence for cancers of the lung, larynx, mouth, esophagus, throat, bladder, kidney, liver, stomach, pancreas, colon, rectum and cervix, plus acute myeloid leukemia. WHO and major cancer bodies agree there is no safe level of tobacco use; quitting at any age improves life expectancy and reduces cancer risk.
What's not established
This classification is based on sufficient evidence in humans that this factor can cause cancer. It does not establish a safe exposure threshold, your personal risk, or how this factor's risk compares in size to other Group 1 agents — hazard classifications are not ranked by magnitude.
Regional relevance
global
Documented in these products
Presence in a product category doesn't imply the product causes cancer. Click each to see the source and context.
Evidence sources
Every claim on this page traces back to one of these. Click through to read the primary document yourself.
Primary sources
NCI
NCI — Risk Factors: Tobacco
IARC
IARC Monographs — Classifications by Cancer Site, Vols 1–140
Supporting sources
Canadian Cancer Society
Canadian Cancer Society — Reduce your risk
ACS
ACS — Known and Probable Human Carcinogens
Cancer Research UK
Cancer Research UK — Causes of cancer and reducing your risk
IARC / WHO — European Code Against Cancer
European Code Against Cancer (5th edition) — 14 ways you can help prevent cancer
NTP
NTP — Report on Carcinogens (US National Toxicology Program)
Cancer Council Australia
Cancer Council Australia — Causes of cancer
WCRF/AICR
WCRF/AICR — Diet, Nutrition, Physical Activity and Cancer: a Global Perspective (Third Expert Report)
WCRF/AICR
WCRF — Cancer Prevention Recommendations
Last reviewed: November 2026
Official reference list
A government list some readers use alongside the primary evidence. Meyron is not affiliated with it. A chemical being listed does not by itself describe a risk from any particular product.
- California Prop 65 list
State of California's list of chemicals known to cause cancer or reproductive harm.