Lung Cancer and Radon

Indoor radon is the second leading cause of lung cancer after smoking, according to a 1999 report from the National Academy of Sciences. The United States Environmental Protection Agency (EPA) and the U.S. Surgeon General strongly recommend that all homes be tested for radon, and if a problem exists, corrective action be taken.Representation of Radon affecting the lungs causing lung cancer

Radon is not an irritant to the eyes or nose, nor is it an allergen. The only risk from radon in air is lung cancer, after many years of breathing it.

Four picoCuries per Liter (4 pCi/L) is the EPA's action guideline for radon concentrations in air of occupied spaces. When long-term exposures are higher, action should be taken to reduce them.

Additional Confirmation of the Risk

According to a National Cancer Institute fact sheet: "Studies showing a link between radon and lung cancer in humans include studies of underground uranium miners and of the general population exposed to radon in their homes."  The latter is a new, significant result, from pooled results of measurements of radon in homes of persons with lung cancer and radon in homes of matched controls.  The pooled results show statistically significant differences, confirming the  risk estimates from studies of underground miners: Darby, et al. (pdf version), British Medical Journal, 2005;  Krewski, et al., Epidemiology, 2005.



The lung cancer risk, accumulated over a lifetime (75 years) from breathing four pCi/L in one's home, depends on an individual's smoking history:

Average Radon  Lifetime Risk of Lung Cancer 
(per person) from Radon 


Persons who Never Smoked

Current Smokers 


 14 in 1,000

 12 in 100


 7 in 1,000

 6 in 100


 3.5 in 1,000

 3 in 100

These assume one spends 70% of the time indoors, breathing the indicated radon concentrations for many years.  The risk is proportional to the cumulative radon exposure through time.  For one year of exposure, the risk would be about 1/75th as high. 

For former smokers, the risks are between those shown for smokers and never-smokers.  

Because of a latency time for lung cancer to develop, and the cumulative nature of the risk, there is little chance that someone could get lung cancer from radon before age 35, although exposures before that age contribute to the risk at later ages. The average loss of life expectancy per lung cancer death is about 15 years (out of 75).


    Last Revised: July 23, 2015