Does exposure to radon causes cancer?

Little risk. This is largely about politics and how much money we are willing to pay (or to force a homeowner to pay) to decrease a very small risk to something even smaller. The risk to a non-smoker is too small to measure even in a big study, and the risk to smokers, while a majority of studies suggest it's real, is also miniscule. Most scientists today seem to be opposed to pricey forced radon-proofing.