Health Effects of Radon

Radon gets no respect, because:

It doesn't give you a headache or make you feel bad in any way. You can't even sense that it's there.
It takes years before any effect on the body can be detected by current medical science.
It isn't caused by some evil corporation that can be picketed.

But people should care about radon, for these reasons:

It is radioactive.
It decays into other radioactive elements (polonium, bismuth, lead) that can become lodged in the lungs.
Radiation is not good for the human body. Less is always better, more is worse. ALARA, the Golden Rule of radiation safety should prevail.

All reputable scientists agree: radon causes lung cancer. And virtually all agree with the National Academy of Sciences, who concluded that radon is the leading cause of lung cancer among non-smokers.

Some researchers believe that the EPA Action Level may be too strict, and (Wouldn't you know it!) some say just the opposite. One 1999 laboratory study even discovered a new damage mechanism. [Details]

EPA has published a variety of equivalences between radon exposure and other risks. The one we think easiest to understand is this:

Breathing air with "N" picoCuries/liter of radon for one week gives your lungs the same radiation dose as "N" chest x-rays.
10 pCI/l = 10 x-rays/week = 520 x-rays per year.