Reference summary — not medical advice or a personal risk estimate.
Indoor biomass fuel smoke (wood)
Quick answer
Classified as Group 2A — probably carcinogenic, based on limited evidence in humans, alongside stronger evidence in animals. Breathed. Cooking or heating with wood, charcoal, dung, or crop residues — especially on open fires or unvented stoves. Roughly a third of the world cooks this way.
Summary
Smoke from indoor wood and biomass burning is associated with lung cancer.
Detail
Indoor emissions from household combustion of biomass fuel (primarily wood) are Group 2A with limited human evidence for lung cancer. Exposure is highest in households relying on open fires for cooking. Improved stoves and ventilation reduce exposure.
What's not established
This classification reflects limited evidence in humans, usually together with sufficient evidence in animals. It does not establish how strong the human evidence would look on its own, a safe exposure threshold, or your personal risk from a given level of exposure.
Regional relevance
regional
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
IARC
IARC Monographs — Classifications by Cancer Site, Vols 1–140
Supporting sources
ACS
ACS — Known and Probable Human Carcinogens
NTP
NTP — Report on Carcinogens (US National Toxicology Program)
Last reviewed: October 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.