To provide for a study of Radium 224 in drinking water and to amend the Safe Drinking Water Act to require that a national primary drinking water standard be established for Radium 224, and for other purposes.

Requires the Agency for Toxic Substances and Disease Registry to study and report to the Administrator of the Environmental Protection Agency on the toxicological effects of Radium 224 and the health effects of exposure to Radium 224 in drinking water.

Amends the Safe Drinking Water Act to require the Administrator of the Environmental Protection Agency to include Radium 224 on the list of contaminants which may require regulation and be subject to a determination by the Administrator to regulate.

Requires State source water assessment programs to be revised every five years after calendar year 1999. Makes such programs and revisions publicly available.