Waterborne health risks and the WHO perspective.

The benefits of improved water and sanitation include both health and non-health effects. The direct health benefits are related to two contrasting roles of water: that of disease vector when it carries pathogens; and that of health mediator through its use in personal and domestic hygiene. Indirect effects related to health include for example improved quality of life and decreased expenditure on medical expenses. Non-health effects include time savings for productive activity or education. The fact that the health impact of inadequate water supply services, especially in the developing world, has never been established is recognised (Troare, 1992) and recent work highlights unrecognised health burdens elsewhere--both from apparently good quality supplies (Payment et al., 1991; Payment et al., 1997); and from outbreaks of disease (Ford and Colwell, 1996). This paper looks at the WHO perspective on waterborne health risks and is divided into three main sections: our knowledge of the existing situation; recognised and emerging priorities arising from the changing context; and the availability of approaches and tools to meet the recognised and emerging priorities.