Radon is a carcinogenic gas released during the decay of uranium that exists naturally in soil and bedrock. It has no smell, taste, or color, and it accumulates indoors, where it and its radioactive progeny are inhaled and directly impact lung epithelium. Radon is a leading environmental cause of lung cancer, with risk increasing with exposure time and magnitude.[1] Fortunately, testing indoor levels is easy and inexpensive. In British Columbia, the BC Centre for Disease Control (BCCDC) collects indoor radon measurements and displays them on an interactive public map to promote testing and awareness.[2]

Radon levels in BC

Uranium levels in soil and bedrock vary dramatically across BC, with the highest levels found in the Interior and Northern Health regions. This pattern is clearly visible on the BCCDC’s interactive radon map, where an estimated one-third of homes in the Interior Health region had radon concentrations exceeding Health Canada’s guideline of 200 Bq/m³. However, radon levels vary on the background of these general patterns. Local geographic features can increase radon levels, and some homes have construction elements that promote radon accumulation (e.g., poor ventilation, below-grade basements, foundation cracks, gaps around pipes, porous walls). For example, 10% of measurements collected from some municipalities in the Vancouver Coastal Health region exceeded 200 Bq/m³, despite the area on average having very low indoor radon levels. This is why Health Canada and the BCCDC recommend that every home be tested for radon.

Radon, lung cancer, and smoking

Exposure to radon increases the risk of lung cancer, but this increase in risk is not equal in everyone. Radon and tobacco smoke interact synergistically. Smokers who are exposed to high radon levels face a much higher risk of lung cancer than would be expected if radon and smoking acted independently to increase risk. In fact, the lifetime risk of lung cancer among nonsmokers exposed to high radon levels is about 2 per 100, compared with about 15 per 100 among smokers exposed to high radon. Consequently, about 85% of radon-attributable lung cancers are in smokers.[3] Whether former smokers or those exposed to secondhand smoke have the same increased risk from radon as current smokers is not yet known.

Routine radon testing is warranted

Importantly, areas of BC with higher smoking rates overlap with areas with higher radon measurements. In 2023–24, about 12% of the population in high-radon health regions (Northern Health and Interior Health) reported smoking daily, compared with 7% to 8% of the population in other health regions.[4] These risks compound; therefore, radon poses a higher risk to the population than it might otherwise.

However, awareness of this risk is low. In a 2023 national survey, only 60% of BC households had heard of radon, and, of those, only 7% reported testing their homes.[5] We do not have good insight into whether smokers are aware of their increased risks.

Physicians and other health care providers can help raise awareness about radon, particularly among smokers, and discuss radon testing while encouraging smoking cessation. Patients with a smoking history should be made aware of their additional risk and the steps they can take to reduce radon exposure. This includes providing education on the health risks of radon exposure, encouraging regular screening for radon at home, and sharing available resources, such as those found in the Box, with patients so they can test their homes and take mitigating steps where possible.
—Claudine Henoud, MD, MPH
Public Health and Preventive Medicine Resident, University of British Columbia
—Jeffrey Trieu, MPH
Senior Epidemiologist, Environmental Health Services, BCCDC
—Anne-Marie Nicol, PhD, MES
Environmental Health/Knowledge Translation Scientist, Environmental Health Services, BCCDC
—David McVea, MD, PhD, MPH
Public Health Physician, Environmental Health Services, BCCDC

BOX. Additional information about radon.

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This article is the opinion of the BC Centre for Disease Control and has not been peer reviewed by the BCMJ Editorial Board.

References

1.    Zeeb H, Shannoun F, World Health Organization. WHO handbook on indoor radon: A public health perspective. 2009. Accessed 24 August 2026. https://iris.who.int/handle/10665/44149.

2.    Trieu J, Young C, Nguyen PDM, et al. The BC Radon Data Repository (BCRDR) and BC Radon Map: Integrating disparate data sources for improved public health communication. Can J Public Health 2024;115:680-687. https://doi.org/10.17269/s41997-024-00895-5.

3.    Lantz PM, Mendez D, Philbert MA. Radon, smoking, and lung cancer: The need to refocus radon control policy. Am J Public Health 2013;103:443-447. https://doi.org/10.2105/AJPH.2012.300926.

4.    Canadian Institute for Health Information. Smoking. Updated June 2026. Accessed 29 September 2026. www.cihi.ca/en/indicators/smoking.

5.    Statistics Canada. Knowledge of radon and testing. Table 38-10-0086-01. Released 9 June 2025. Accessed 28 August 2026. https://doi.org/10.25318/3810008601-eng.