Lung Cancer and Radon

Indoor radon is the second leading cause of lung cancer after smoking. Radon can lead to lung cancer after many years of breathing it.

The United States Environmental Protection Agency (EPA) and the U.S. Surgeon General strongly recommends all homes be tested for radon, and if a problem exists, homeowners should fix it.

Radon is measured in picoCuries.  The EPA recommends homes with radon levels of four picoCuries per Liter (4 pCi/L) or higher be fixed.


"Most radon-induced lung cancers occur from low and medium dose exposures in people's homes. Radon is the second most important cause of lung cancer after smoking in many countries."

--Dr. Maria Neira of the World Health Organization (WHO)


EPA Risk Estimates (Based on 1999 NAS Report) for Long Term Radon Exposure in Homes

Average Radon Exposure

Lifetime Risk of Lung Cancer 
(per person) from Radon 

  Persons who Never Smoked Current Smokers
8 pCi/L 15 in 1,000 120 in 1,000
4 pCi/L 7 in 1,000 62 in 1,000
2 pCi/L 4 in 1,000 32 in 1,000
1.3 pCi/L 2 in 1,000 20 in 1,000
0.4 pCi/L
3 in 1,000

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:

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 it takes a long 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: November 28, 2016