Radon is a known human carcinogen and is the second leading cause of lung cancer.
Statistics from Cancer.gov displays lung cancer as one most common cancers as displayed below
The most common cancers (listed in descending order according to estimated new cases in 2020) are breast cancer, lung and bronchus cancer, prostate cancer, colon and rectum cancer, melanoma of the skin, bladder cancer, non-Hodgkin lymphoma, kidney and renal pelvis cancer, endometrial cancer, leukemia, pancreatic cancer, thyroid cancer, and liver cancer.
Prostate, lung, and colorectal cancers account for an estimated 43% of all cancers diagnosed in men in 2020. For women, the three most common cancers are breast, lung, and colorectal, and they will account for an estimated 50% of all new cancer diagnoses in women in 2020.
Americans on average spend 90% of their time indoors, where concentrations of air pollutants can be 2 to 5 times higher than typical outdoor air.
People who are often most susceptible to the adverse effects of pollution (e.g., the very young, older adults, people with cardiovascular or respiratory disease) tend to spend even more time indoors.
The link between some common indoor air pollutants (e.g., radon, particle pollution, carbon monoxide, Legionella bacterium) and health effects is very well established.