Radon and cancer
Radon is a naturally occurring, invisible, and odorless radioactive gas that is produced from the decay of uranium in rocks and soil. It can accumulate in indoor spaces, particularly in buildings overlying uranium-rich areas, posing significant health risks. Radon exposure is recognized as the second leading cause of lung cancer, responsible for 3 to 14 percent of lung cancer cases worldwide, as reported by the World Health Organization in 2023. The primary mechanism of harm involves inhalation of radon decay products, which can lodge in lung tissue and emit ionizing radiation, leading to cellular damage and cancer over time.
Individuals who smoke are at an even higher risk of developing lung cancer when exposed to radon due to the combined harmful effects of both carcinogens. Common types of radon-related lung cancers include squamous cell carcinoma and adenocarcinoma, with symptoms often appearing only in advanced stages of the disease. Historically, the dangers of radon exposure were identified through studies of underground miners, and subsequent regulations have aimed to limit indoor radon levels for public health. Testing for radon is essential, and the US Environmental Protection Agency recommends that indoor concentrations should not exceed 4 picoCuries per liter. Understanding radon's health impacts is crucial for both individuals and communities, especially in areas prone to high levels of this gas.
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Subject Terms
Radon and cancer
ALSO KNOWN AS: Radon-222, thoron (radon-220), actinon (radon-219)
RELATED CANCERS: Lung cancer; radon exposure may also increase the incidence of stroke
DEFINITION: Radon is an invisible, odorless, radioactive gas produced naturally from uranium in rocks and soil. Except for areas rich in uranium-ore deposits, radon is usually present at low levels in water, soil, and outdoor air. It decays spontaneously to form solid radioactive products called "radon daughters," or "radon progeny," that emit ionizing radiation, mostly as alpha particles and gamma radiation. Radon gas may seep into buildings from underlying soil and accumulate at dangerous levels in indoor spaces. Its levels can be measured by using radon test kits.
Exposure routes: Inhalation, ingestion
Where found: Uranium mines and mills, hard-rock mines, phosphate mines, granite formations, groundwater, soil, air, building materials
At risk: Workers in uranium mining and milling, workers in iron-ore and fluorite mining, general population exposed to indoor radon levels of 4 picoCurie per liter (pCi/L) or higher
Etiology and symptoms of associated cancers: Radon is the second leading cause of lung cancer after cigarette smoking, and it accounts for 3 to 14 percent of lung cancers worldwide, as the World Health Organization reported in 2023. Most of the risk to humans is from inhaled radon daughters that can lodge in the lungs and emit energetic particles. Damage to epithelial cells in lung tissue can eventually lead to cancer. For smokers, the risk of lung cancer is even greater because of the synergistic effects of radon and smoking.
Among the deadliest of all cancers, lung cancer had an overall five-year survival rate of 28 percent, according to the American Cancer Society in 2024. Radon-related lung cancers include squamous cell carcinoma, adenocarcinoma, small-lung carcinoma, and large-cell carcinoma. In its early stages, lung cancer may be asymptomatic or have nonspecific symptoms (weight loss, fatigue, and fever). By the time symptoms develop that are suggestive of the disease (chronic coughing, shortness of breath, hoarseness, bloody sputum, difficulty swallowing, wheezing, and chest pain), the cancer has usually spread to other organs.
History: Once produced commercially for use in radiotherapy, radon is used mostly in research. Scientists established radon’s carcinogenicity primarily from occupational studies conducted between the 1950s and 1980s that revealed high mortality rates from lung cancer among underground uranium miners. In 1984, exposure to radon in buildings became recognized as a potential health hazard. In the Indoor Radon Abatement Act of 1988, the US Environmental Protection Agency (EPA) recommended that indoor radon levels not exceed average levels outdoors (about 0.4 pCi/L). This standard is one-tenth of the level at which the EPA suggests radon mitigation for homes.
Bibliography
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