Calcium and magnesium in drinking water and the risk of death from breast cancer

The relationship between mortality from breast cancer and the levels of cal cium and magnesium in drinking water was examined using an ecological desig n. The study area consisted of 252 municipalities in Taiwan. Data on the le vels of calcium and magnesium in drinking water were collected from the Tai wan Water Supply Corporation (TWSC). The age-standardized mortality rate (A SR) for breast cancer (1982-1991) was compared among municipalities with di fferent levels of magnesium and calcium in drinking water. Weighted multiva riate regression analysis was used, and after adjusting for fertility rates and urbanization, there was a significant inverse relationship between the levels of calcium and magnesium in drinking water and risk of death from b reast cancer.