American Cancer Society in their Website declares that multiple studies have found that exposure to radon increases lung cancer risk
- Studies of people working in underground mines with high levels of radon exposure
- Studies comparing radon levels in homes of people with lung cancer with the levels in homes of similar people without lung cancer
- Studies comparing lung cancer cases or deaths in areas with differing levels of radon exposure
These studies also show that the overall risk of lung cancer from radon is even higher in smokers and former smokers.
But many other agencies state the same thing:
The International Agency for Research on Cancer (IARC) is part of the World Health Organization (WHO). One of its goals is to identify causes of cancer. Based on sufficient evidence that radon and its progeny can cause lung cancer, IARC classifies them as “carcinogenic to humans.”
The US Environmental Protection Agency (EPA) monitors the human health effects from exposure to various substances in the environment. The EPA lists radon as the second leading cause of lung cancer and the number one cause of lung cancer among non-smokers, estimating it is responsible for about 20,000 lung cancer deaths every year.