Residential Radon Exposure and Lung Cancer Prevention in Canadian Primary Care: A Narrative Review and Practice Algorithm

Residential radon is an invisible radioactive gas produced during the uranium-238 decay series and is an established cause of lung cancer. In Canada, recent national surveillance suggests that about one in five residential buildings may exceed the national radon guidelines, yet household testing remains uncommon. This narrative clinical review translates international and Canadian evidence into practical primary-care and hospital-to-community actions. Evidence was prioritized from carcinogen classifications, World Health Organization guidance, pooled residential case–control analyses, Canadian surveillance and guidance, and the peer-reviewed literature on mechanisms, histology, and risk communication. Radon-222 can enter buildings from soil gas; its short-lived progeny deposits in the respiratory tract and emits high-linear-energy-transfer alpha particles that can damage bronchial epithelial DNA. Because elevated levels cannot be reliably predicted from symptoms, smoking status, house age, or community maps, clinicians should use a simple workflow: ask about prior testing and lower-level occupancy; test with a long-term, approved device in the lowest occupied level; act by interpreting the result, advising mitigation, and directing patients to certified radon professionals when needed; document the exposure assessment, result, advice, referral, and retesting plan; and follow up after mitigation or major building changes. This review clarifies Canadian residential and workplace guidance, contrasts global reference-level approaches, and distinguishes radon prevention from lung cancer screening. No individual patient information or human-subject data are reported.