Frequently asked questions about radium in drinking water
Wisconsin Department of Natural Resources
Radon is a substantial health risk in many Wisconsin homes. There is a risk of developing cancer from long term exposure to radon in air and water. If you get your drinking water from a private well, this page will guide you in evaluating whether radon is a concern.

Radon and Your Home
by James R. Brooks March, 1988
Radon, first discovered in 1910, is a colorless, odorless, radioactive gas formed from the radioactive decay of radium. Radium in turn is formed from uranium which is present to some extent in all rocks but is most common in those of granitic composition. It is not unusual for granites to contain as much as 3.9 parts per million uranium and .0013 parts per billion radium. When rocks weather, these radioactive elements find their way into the soil. Radon has a half-life of only 3.8 days; consequently, most of the gas decays harmlessly in the ground or atmosphere.

The primary source of radon in homes is from the underlying soil and bedrock. For most Americans, their greatest exposure to radon is in their homes; especially in rooms that are below grade (e.g., basements), rooms that are in contact with the ground and those rooms immediately above them. However, an additional source could be the water supply, particularly if the house is served by a private well or a small community water system.