Principal aquifers can contribute radium to sources of drinking water under certain geochemical conditions

http://pubs.usgs.gov/fs/2010/3113/

Knowledge of the geochemical processes controlling radium occurrence in groundwater may help water-resource managers anticipate and minimize human exposure to this cancer-causing element.

by Szabo, Zoltan; Fischer, Jeffrey M.; and Hancock, Tracy Connell

U.S. Geological Survey Fact Sheet 2010-3113