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Coping with Uncertainty: Policy and Politics in the National Health Service.

Improving water and sanitation and improvements in health Results of epidemiological studies into the relationship between the quality of water supply and sanitation versus human health vary widely and there are severe methodological difficulties involved in undertaking such studies. Nevertheless there is sufficient evidence to support the conclusion that improving water supply and sanitation can have a significant impact on human health. Table 3 summarizes the findings of an extensive review of studies of this type. Table 3: Percentage reduction in the diarrhoea morbidity rate attributed to improvements in water supply or excreta disposal WHO SEMINAR PACK FOR DRINKING-WATER QUALITY 4 Type of Intervention Number of Studies Percentage reduction Median Range All 53 22 0-100 Water quality improvements 9 16 0-90 Improvements in availability 17 25 1-100 Improvements in availability and quality of water 8 37 0-82 Improvements in excreta disposal 10 22 0-48 Source: after Esrey, Feachem and Hughes, 1985 One of the reasons for the difficulty in undertaking studies on the health impact of improvements in water supply quality is that the faecal – oral route includes several and multiple routes to infection as summarized in Figure 1 below. Figure 1: Principal elements of faecal – oral disease transmission This complexity of routes also demonstrates the importance of various aspects of hygiene as complementary actions to water quality improvements.