In addition, a few high radium levels have been found in groundwater from sandstone formations in west central Wisconsin and in granite formations in north central Wisconsin. In all cases, the radium was there long before the first well was drilled. By law, all community water systems must be monitored for radioactivity. If gross alpha activity is found, further testing for radium is conducted. The standard applies to levels in the water distribution system, as determined quarterly and averaged over a one-year period.
Radium is known to cause bone cancer when consumed in high doses.
It is approximately the same as the risk of dying from lightning strikes, or tornadoes and hurricanes. Fortunately, the risk from radium is manageable because radium can be removed from drinking water. In the 1920s, radium paint was used to make watch dials luminescent. The workers who painted the watch dials would touch the paintbrush tips to their tongues, and inadvertently swallow high doses of radium. This effect of radium has also been documented in laboratory animals.