Central Ohio has relatively high natural concentrations of uranium from glacial deposits and shale, which during radioactive decay, produces radium and radon.

The EPA’s current radon action level is four picocuries of radon per liter of air (4 pCi/L). Most counties in central Ohio have high potential for radon, with predicted average indoor greater than the EPA action level. According to one study cited by Ohio Department of Natural Resources Department of Geological Survey, 38% of Ohio’s 88 counties had average indoor radon levels above 4.0 pCi/L, but Licking County’s average was above 8.0 pCi/L. Seven Ohio counties—Carroll, Fairfield, Franklin, Harrison, Knox, Pickaway, and Ross—had average indoor Radon concentrations between 6 and 8 pCi/L.

The amount of radon in the soil depends on soil chemistry, which varies from one house to the next. Radon levels in the soil range from a few hundred to several thousands of pCi/L in air. The amount of radon that escapes from the soil to enter the house depends on the weather, soil porosity, soil moisture, and the suction within the house.