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Research areas and results of the LBNL high-radon project

Some downloadable data and results are available here.
Please take a look at the detailed information about methods, models, and data.
 

The high-radon project attempted to :
  • determine the most significant factors that are predictive of high radon levels, and 
  • quantify how important they are. 
One disappointing truth is that no matter what variables are included, there is still a lot of unpredictability in radon concentrations. Contrary to popular belief, it is not true that indoor radon concentrations can be predicted from geologic information. Geology is important, but it's not the only important factor.  Also, available geologic information don't include detailed maps of soil permeability to air, etc. 

Here is a brief list of the most significant predictive factors for the U.S. as a whole. Note that the "examples" just give a few cases where the factor is important, not a definitive, all-inclusive list.
 

Significant factor

Examples of where it occurs

Why it matters
Living in the Northern U.S. Northern U.S., of course! In winter, warm indoor air escapes through the top of the house.  As a result, the pressure inside the house is lower than the pressure outside, so air is drawn into the house...including air from the soil around the house.
Having a basement that is used as living space  Mostly in the Northern U.S. Basements have a lot of surface area exposed to the soil, so radon can easily enter the basement. Also, ventilation tends to be poor in the basement.  Basement concentrations are often over twice as high as concentrations on the first floor. If the basement isn't used as living space, high concentrations there aren't much of a problem. If someone spends several hours a day in the basement, though, high levels there can lead to significant radon exposure.
Living in an area with soil or bedrock that has an extremely high radium concentration Parts of NJ; parts of eastern PA; some areas in OH, a few small areas in Northern FL; some small areas near San Diego.  Many other areas too, but these are the worst. Radon is a decay product of radium.  Without radium, there's no radon!  All soils and rocks have some radium, but some have much more than others.  Still, many areas of the country have high soil radium but don't have high indoor radon concentrations: other factors are also very important.
Living in an area with very high soil permeability (to air) Some areas near Spokane, WA; some areas in central KY.  If the soil around a house is very permeable, large amounts of soil gas can enter the house.  The soil gas may not have high radon concentrations compared to other soil gas, but all soil gas has high radon concentration compared to outdoor air, so if a lot of soil gas enters the house then the house can have a high radon level.

 
 
 

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