Why does Colorado have high radon levels and low lung cancer rates?
Relative to other states, Colorado has the third lowest lung cancer death rate in the nation. For the period 1993-1997, the Colorado cancer death rate per 100,000 population was 48.2 among males, 25.6 among females. These rates are well below the national averages of 69.4 for males, 34.0 for females.
Colorado radon levels are well above the national average. The average short term radon test done in Colorado comes in at 7.3 pCi/L. USEPA estimates the average indoor radon level nationwide is 1.3 pCi/L.
So why don't cancer rates match up better with radon levels? Mobility is a key factor. Colorado's population is growing rapidly- people move here from other parts of the nation where they might have been exposed to more or less radon. Also death statistics are from the county in which the person died. Many residents move away from Colorado (retire in another state for example) and are not residents when they die, so their deaths are not recorded in Colorado. This in addition to the fact that they have moved here after exposure to unknown amounts of radon elsewhere shows that this is not a reliable way to equate any state's radon levels with the state's lung cancer rates.
Second it must be remembered that smoking is the chief cause of most lung cancers. USEPA estimates that only about 10% of all lung cancers are attributable to radon. Most of these 10% are smokers, who have succumbed to the combined risks of smoking and radon. Therefore Colorado's low smoking rate might help explain our low lung cancer rate.