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| These maps might look different from other radon maps that you've seen. And the numbers might even contradict other radon maps. | All of our maps attempt to describe the distribution of annual-average concentrations in the living area of homes. Most radon measurements are made in the basement, for just a short period of time (a few days), so our maps look different. | Short-term, basement measurements are both biased and variable compared to long-term, living-area concentrations that are a more accurate way to judge risk from radon. |
| Be cautious when interpreting the maps! | No single map can adequately display all of the relevant information. For instance, the amount of data (and thus, the accuracy of the plotted results) varies widely among counties. |
Map |
Description |
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| Predicted fraction of homes with long-term living-area concentrations over 4 pCi/L, | The U.S. Environmental Protection Agency recommends remediating your
home if your concentration exceeds 4 pCi/L. This map shows the estimated
fraction of homes over that level, by county.
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| Predicted medians for U.S. counties | Predicted median concentration (of annual-average, living-area concentrations). Half of the homes in a county are expected to exceed this concentration. |