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Radon exposure causes lung cancer

What you may have heard

Radon gas causes cancer.

What science tells us

Radon is a colorless, odorless gas that, after long-term exposure, can lead to lung cancer. Radon breaks down into radioactive elements in the air, which are absorbed into the body.

Radon is considered carcinogenic to humans by national and international organizations, including the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), and the U.S. Environmental Protection Agency (EPA) (ACS). Cigarette smoking is by far the most common cause of lung cancer in the United States, but radon exposure is the second-leading cause (ACS).

Who is at risk for radon exposure? Those who work in underground areas, specifically miners, have significantly higher rates of radon exposure. This is also true for those who work in uranium processing factories or come into contact with phosphate fertilizers. As a result, these groups have a higher chance of developing lung cancer and should take caution and pursue regular screening (ACS).

Epidemiological Evidence

In a paper that examined 13 epidemiological studies across Europe, it was concluded that long term exposure to radon increases the risk of lung cancer (Darby et al.).

Laboratory Evidence/Supporting Evidence

Several laboratory studies using rats and dogs have shown that exposure to radon leads to the development of lung cancer(National Research Council (US) Committee on the Biological Effects of Ionizing Radiations). Several other animal studies have confirmed the results of human studies that high exposure to radon can lead to the development of lung tumors (NCI).

IARC Carcinogen Classification: Group 1 (Carcinogenic to humans)

How to reduce your risk

Since radon is in the air, we can’t completely eliminate our exposure to it. However, there are steps you can take to reduce your risk:

  • In your home: Test the level of radon (EPA) in your home by purchasing a do-it-yourself kit or hiring a professional to test the radon level for you. Levels of radon above 4.0 pCi/L are considered harmful to humans. You may also decrease your exposure through cracks by sealing walls or floors or by increasing ventilation using fans and pipes.
  • In your workplace: OSHA and the NRC have taken steps to reduce the exposure of radon for those who work in an underground mine (ACS).

If you are exposed to radon and you are a smoker, experts recommend quitting or decreasing cigarette use. This can reduce your chance of developing lung cancer dramatically (ACS).

In addition, speak to your doctor about regular health checkups and tests to look for possible signs of lung cancer. Some symptoms of lung cancer to take note of are shortness of breath, a new or worsening cough, pain or tightness in the chest, hoarseness, or trouble swallowing (ACS).

Bottom line

Radon exposure is the second-leading cause of lung cancer in the United States, after cigarette smoking. Decreasing your cigarette use and ensuring your workplace and home are up to national standards for radon levels are the most effective ways to reduce your risk of lung cancer.

American Cancer Society (ACS): Radon and cancer
Environmental Protection Agency (EPA): Radon
Centers for Disease Control (CDC): Radon


Published: July 6, 2021
Verified/updated: August 22, 2022