Water constituents and trace elements in relation to cardiovascular diseases

Significant inverse correlations between the hardness of drinking water and local cardiovascular mortality rates are found consistently in major national studies and less consistently within smaller regions. A number of bulk and trace constituents of finished water at the treatment plant show correlations with mortality of equal but not greater magnitude to the correlations of hardness with mortality. Little is known about these relationships with tap water, but levels of several trace metals of biological significance are known to vary markedly within water distribution systems and are probably related to types of pipe and the corrosiveness of the water supplied. Tap water studies and studies of localities within smaller regions are recommended to disentangle the association of water quality and health from the associations of both to other regionally distributed factors. Rainfall is one such factor which may influence the content of both drinking water and soil and thus human mineral intake. A number of other environmental and social factors seem unlikely to be intermediaries from the results of several multivariate studies.