How much radon raises lung cancer risk for smokers and non-smokers in Canada, why it has no early symptoms, what else it does, and screening by province.
Photo: Shixart1985, CC BY 2.0, cropped, via Wikimedia Commons.
More than 3,000
Lung cancer deaths a year in Canada that Health Canada attributes to radon exposure; it estimates that 16% of lung cancers come from radon. The same factsheet gives 3,200 in its comparison with car accidents (1,898), carbon monoxide (300) and house fires (109); the headline figure is the one used here.
Health Canada attributes more than 3,000 lung cancer deaths a year in Canada to radon, and says 16% of lung cancers come from it. In people who do not smoke, Health Canada names radon the number one cause of lung cancer. The risk builds over years and is higher for smokers. Lung cancer is the only health effect of radon that is well established.
If you have a test result in hand, see what your number means and how soon to act.
The 2024 Cross-Canada Radon Survey and the World Health Organization’s radon handbook both rank radon second to smoking as a cause of lung cancer. Both put it first among people who never smoked or smoked very little. The International Agency for Research on Cancer has classed radon and its decay products as a Group 1 carcinogen, a proven cause of cancer in humans, since 1988.
Three pooled analyses carry the evidence. The European analysis combined 13 studies, 7,148 people with lung cancer and 14,208 controls. The North American analysis combined seven studies (3,662 cases, 4,966 controls), the Chinese two (1,050 cases, 1,996 controls). All three found higher average radon in the homes of people with lung cancer.
16
%Increase in lung cancer risk per 100 Bq/m³ of long-term radon exposure, after correcting for measurement error (8.4% on measured concentrations), in the pooled analysis of 13 European case-control studies. The relationship is linear, with no threshold, and significant below 200 Bq/m³.
Breathing in radon and its decay products exposes your lung cells to alpha radiation. Alpha particles release a lot of energy over a very short distance, beside the cells that absorb oxygen, and those cells repair that damage poorly. Damage to DNA can lead to lung cancer years later.
The Canadian Cancer Society estimates that 32,900 Canadians will be diagnosed with lung and bronchus cancer in 2026, with 19,300 deaths, 22% of all cancer deaths. See how radon gets into a house and into well water.
Health Canada’s lifetime risk table models the chance of lung cancer by radon level and smoking. Its figures are population estimates from a model, never any one person’s risk.
About 2% and 17%
Health Canada's modelled lifetime risk of lung cancer at the 200 Bq/m³ guideline level, for a person who never smoked and for a smoker. It rises to about 5% and 30% at 800 Bq/m³, against a baseline of about 1% for a never-smoker. Population estimates from a model, never an individual's risk.
At the guideline level the table puts a smoker’s lifetime risk far above a never-smoker’s, and both rise as the level rises. The risk is long term: the longer you breathe high levels, the higher it gets, and smoking and radon together raise it further. For former smokers, the WHO handbook places the radon-related risk between current smokers and lifelong never-smokers. Peterson and colleagues estimated that radon in Ontario homes causes 13.6% of the province’s lung cancer deaths, about 847 a year, roughly 84% in people who ever smoked.
The Cross-Canada Radon Survey’s authors anticipate a different risk for someone exposed to tobacco smoke, asbestos or combustion particulates. The same goes for someone who has COPD or has had tuberculosis or severe pneumonia. They recommend that people with those exposures test their building. Health Canada’s guideline wording is that “the health risk below 200 Bq/m³ is small, but there is no level considered risk free”. See how to test your home.
Radon has no symptoms: you cannot see, smell or taste it, and it does not cause headaches, fatigue or a feeling of being unwell. The only way to know your level is to test. A symptom is a reason to see a doctor, whatever your level. A cough that will not go away, coughing up blood or weight loss you cannot explain are reasons to book that visit.
Read why a map cannot tell you about your home. The Cross-Canada Radon Survey says its results should not be used to judge personal risk or whether one household should test, because radon varies between homes, including neighbouring ones. Find which level and room of your home to test.
No other health effect of radon is established.
None established
Health effects of radon other than lung cancer, as found by a 2024 systematic review that screened more than 10,000 records and included 129 studies. It found lung cancer the only well-established effect, and no causal link with leukemia, brain tumours, stroke, heart disease, COPD, melanoma, dementia or other cancers. Some results were suggestive and need more study.
A 2024 review looked for other effects and did not establish any. It covered other cancers, heart and brain conditions and lung disease. For pregnancy, a separate 2024 review found the evidence limited and inconsistent, with no established link to miscarriage, birth defects or other problems, and called for more research.
Radon in drinking water is usually not a problem; the bigger risk is indoor air, though very high levels in private well water can occasionally matter. Age has its own page: read what the evidence says about age and exposure. See the evidence on children and pets.
Lung cancer screening programs are based mainly on age and smoking history, and radon exposure on its own does not qualify you. Programs vary across the country, and some provinces and territories do not have a full program. Eligibility changes, so check with the program before you assume you qualify. As of the date this page was checked, the two provincial programs we list state their criteria this way:
If you have lived with high radon and do not meet the smoking criteria, you are not automatically eligible for screening. Testing the home, and fixing it if the level is high, is the step that is yours to take. See how a high level is fixed.