Radon in Missoula

Radon is a naturally occuring colorless, odorless, radioactive gas produced by the breakdown of uranium in soil and rock.


When this gas is drawn into a home or building, it can build up to dangerous levels and be inhaled into the lungs. Radon and its decay products can release radiation into lungs and damage the tissue. In fact, radon exposure is the number one cause of lung cancer among non-smokers and is responsible for about 21,000 lung cancer deaths each year in the US.


Because of Montana's geology, many homes in the state and Missoula County have high levels of radon gas.


  • Missoula levels are high. For example, nationwide 7% of buildings contain elevated levels of radon. In Missoula, 54% of homes have high levels (see pie chart). This is over 7x the national average.


  • In the U.S. the average indoor radon level is 1.3 pCi/L. In Missoula County, the average is 7.2 pCi/L. This is more than 5x the national average. This is like recieving approximately 350 chest x-rays in a year or smoking 14 cigarettes a day.




When the Health Department looked at test results throughout the County, no pattern was observed. Homes in the valley, in the foothills, and it all reaches of the county had high levels*.


Interestingly, one house may test high but a neighbor's home may be low. This is due to differences in the ground structure and to a lesser degree, the home construction. All the more reason to test every home.


The take home message: All zipcode averages are above the EPA Action Level of 4pCi/L.


In a location like Missoula, building homes to be radon resistant from the start makes good sense.

*Based on 2012 study of zip code data from MCCHD test kit sales
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