From Ohio History Central
Radon is a naturally occurring radioactive gas that is a product of the breakdown of small amounts of uranium in rock or soil. It is thought to be a carcinogenic agent if it is concentrated in buildings in sufficient quantities. The U. S. EPA has set a concentration of four Pico curies per liter as an “action level’ at which steps should be taken to reduce long-term exposure to this gas. Radon enters homes from the soil or bedrock through basements or foundations in contact with the ground and is generally in highest concentrations in the lowest part of the structure. Radon concentrations can be tested in buildings by purchasing kits or canisters at many hardware and home -supply stores.
Home tests by nearly 140,000 individuals across Ohio indicate that most areas of the state do not have significantly high concentrations of radon, although such statistics do not guarantee that specific sites or homes will not have a problem. However, several counties in the state have yielded results suggesting that high radon concentrations may be pervasive in some areas. Knox and Pickaway Counties, and in particular, Licking County, have yielded consistently high radon readings from home tests.
Some areas yielding elevated radon levels are underlain by the Ohio Shale of Late Devonian age. This unit is known to contain uranium. Glaciers of the Ice Age ground up the shale and redeposited it in areas not underlain directly by this unit, leading to elevated radon levels. The glaciers also incorporated weathered soils formed on extensive limestone and dolomite bedrock in western Ohio. These weathered soils tend to concentrate uranium. Therefore, glacial sediments may have higher levels of radon derived from this source. In addition, the permeability of soil, rock, and sediment contribute to radon concentrations in homes as the gas can move more easily through cracks or between grains.
For extensive information on radon in Ohio, please visit the Ohio Radon Information System Web site maintained by the University of Toledo. This Web site has statistics on radon concentrations in counties and zip codes, geologic sources of radon, mitigation, and much other information.