Calcium-Carbonate hardness of public water supplies in the conterminous United States

Geographic variations in the hardness of water seem to parallel the geographic variations in certain cardiovascular diseases (Anderson and others, 1969; Biorck and others, 1965; Schroeder, 1966). Winton and McCabe (1970) have provided a recent review of the problem. The map, presented here, showing calcium-carbonate hardness of municipal raw-water sources in the conterminous United States has been compiled to provide data for further examination of correlations between water hardness and cardiovascular diseases.