“Several studies in the past decade have suggested that the death rate from coronary disease is inversely correlated with the hardness of the local water supply: the harder the water, the lower the coronary rate. A study recently published in the New England Journal of Medicine reports evidence that the excess coronary deaths in soft-water areas are almost entirely sudden deaths outside the hospital. Researchers at the University of Toronto School of Hygiene reviewed the death certificates of 55,000 people who died in the province of Ontario in 1967 and classified the deceased individuals according to the hardness of their local water supply.”
—Scientific American, June 1969
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