Soft water and ischaemic heart disease: a study of two towns in Northern Ireland.

Portadown and Lurgan have had very similar populations during the years 19501970 and the water supply to each has been established for the past 50 years. Portadown draws its very soft water by aqueduct from two reservoirs on the western face of the Mourne Mountains (at Foffany and Spelga), and Lurgan is supplied by less soft water drawn from Lough Neagh which is at that area largely supplied by the River Bann. The total hardness for the Portadown water supply is about 13 parts per million, and for the Lurgan water about 95 parts per million. There is no reason to suppose any deviation from these figures over the past 20 years.