Reference summary — not medical advice or a personal risk estimate.
Outdoor air pollution
Quick answer
Classified as Group 1 — carcinogenic to humans, based on sufficient evidence in humans. Breathed. Air pollution from traffic, industry, and burning of solid fuels. Everyone outdoors breathes some — the level depends on where you live.
Summary
Outdoor air pollution and the particulate matter in it are associated with increased lung and bladder cancer risk.
Detail
IARC classifies outdoor air pollution and the particulate matter (PM2.5, PM10) component as Group 1 with sufficient evidence for lung cancer and limited evidence for bladder cancer. WHO estimates air pollution contributes substantially to global lung cancer mortality.
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
WHO
WHO — Cancer fact sheet
IARC
IARC Monographs — Classifications by Cancer Site, Vols 1–140
Supporting sources
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)
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.