Possible relationships between the physical environment and human hypertension: cadmium and hard water

There is no proven relationship between the physical environment and the pathogenesis of essential hypertension. There are, however, marked and unexplained variations in death rates from cardiovascular disease in the United States. Potable water, an environmental influence to which all persons are exposed, also varies considerably in its hardness and this hardness is inversely correlated with cardiovascular death rates. Experimentally, chronic feeding of cadmium, and perhaps mercury to rats in trace quantities can cause a mild to marked elevation of blood pressure which has been associated with increased mortality. This metal-induced hypertension in animals resembles essential hypertension in man in that there are no other evidences of metal exposure, and it raises the possibility that some clinical hypertension might be related to inapparent metal exposure which in turn might be a function of water hardness.