Serum electrolytes and skeletal mineralization in hard- and soft-water areas.

Serum levels of calcium and magnesium were measured in two Ontario cities that differ widely in the hardness of their local water-supply. The hypothesis being tested was that residents of the city with the hard water-supply (and a low cardiovascular death-rate) would show relatively high serum levels of calcium and/or magnesium. In addition, a comparison was made of the cortical thickness of the second metacarpal bone in the two areas to see if there was any evidence of increased skeletal mineralization in the hard-water area. The results obtained did not support either of these hypotheses, but it is suggested that the failure to demonstrate differences in body-levels of calcium or magnesium may not be incompatible with one (or both) of these water-borne elements functioning as the "water-factor" in cardiovascular disease.