Welcome to the Radon Project at Columbia University. This website was created by Prof. Andrew Gelman at Columbia University and Dr. Phillip N. Price at the Lawrence Berkeley National Laboratory to assist U.S. homeowners in deciding what to do about radon (if anything).

Radon is a radioactive gas that can enter your house from the ground. It decays radioactively into other radioactive elements that can cause lung cancer. You might want to measure your house for radon and possibly reduce the level of radon in your house through remediation. Here's some More on radon and why we care about it.

Based on the information you provide, this website will estimate the radon level in your house and how much risk of lung cancer this will cause, and will provide a recommendation as to whether you should:

  1. remediate your house immediately, or
  2. take a year-long radon measurement (and then use that information to decide whether to remediate), or
  3. take a short-term radon measurement (and then use that information to decide whether to remediate), or
  4. do nothing. (If we recommend "do nothing", that doesn't guarantee that you don't have a radon problem, it just means that you probably don't have a problem. If you want to be sure, go ahead and make a measurement!)

The map below shows median living-area radon levels (half the homes are higher, half lower) for counties in the contiguous United States. Areas in grey mostly have low radon levels; redder areas have higher levels. But there is a lot of local variation, and high-radon houses and low-radon houses exist in all areas of the U.S.

Click anywhere on the map to begin, or click here.

  More about this map
US Map with pCi/L colors

For this site, we used data and predictions of long-term, living-area concentrations. Most radon maps are based on data that are biased because they contain some combination of: multiple measurements in high-radon homes but not in normal homes, short-term measurements rather than long-term measurements, basement measurements rather than living-area measurements, or other sources of bias or error. That's why the radon distributions on this site may be much lower than on other maps and websites you may have seen.

You can read about the theory and research behind this program and about the people who did the work.

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