Radon gas accumulating in poorly ventilated basements and ground-floor dwellings is a recognized cause of lung cancer. Which statement about radon is CORRECT?

• A It is a chemically reactive gas produced by fossil fuel combustion
• B It is a radioactive daughter product in the uranium-radium decay series, emitted from soil and rock ✓
• C It causes lung cancer mainly through chemical irritation of the bronchial mucosa
• D It poses its main hazard through contamination of drinking water supplies

Explanation

Radon is an odourless, chemically inert radioactive gas belonging to the uranium-radium decay chain, seeping from soil, rock and building materials into enclosed spaces. Its short-lived alpha-emitting daughters deposited on bronchial epithelium irradiate basal cells and cause lung cancer; it is ranked the second most important cause of lung cancer after smoking. Chemical reactivity and irritation are ruled out because radon is inert. Inhalation, not drinking water, accounts for nearly all of its carcinogenic hazard.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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