The problems of urban water supply and water related disease in the Americas are examined in the context of population growth and geographical features. The debate concerning the transmission of potentially water-borne pathogens is discussed. The factors affecting the quality of water supply services in a large metropolitan area (Lima) are described and the epidemiological characteristics of water-related disease summarised and compared with data from Africa (Lesotho).

A water quality additive index is proposed in order to identify the level of risk for each metropolitan district. This incorporates the presence of faecal coliforms and the absence of chlorine residual. A water-related disease product index (DPI) is also proposed which incorporates the incidence of typhoid, hepatitis and diarrhoea. The indices were matched for all districts, where adequate data were available, and a strong correlation was noted. The water quality index was divided into categories (A,B,C) and it was observed that these were generally dependent upon the water supply service levels. It is concluded that disinfection control is grossly deficient in most developing countries but essential for the control of water-borne disease.

* The full version of this article will appear in Water Science and Technology, 21(6/7), 579-591 (1989).

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