The EPA has established strict limits on radium in public drinking waters. These regulations require that if the radium 226 activity exceeds 3 pCi/L, radium 228 activity must be measured. If the combined activities of these radioisotopes exceed 5 pCi/L, the water supply exceeds the EPA limit for radium in water. The standard methods of analyzing for radium involve either alpha counting a purified barium-radium sulfate co-precipitate, or measuring the radian de-emanated from radium 226-containing samples. An involved wet chemical procedure based on the ingrowth of actinium 228 has been published by the EPA for radium 228 analysis (U.S. EPA 1980). Simpler, more precise gamma ray spectroscopy methods have been developed, significantly lowering the detection limits (U.S. EPA 1980).
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