Estimating the health impacts of unsafe drinking water in developing country contexts

The major health threat posed by drinking unsafe water is infectious diarrhoea. The impacts of infectious diarrhoea are considerable and it disproportionately affects children under 5 in developing country contexts. In fact it is the leading cause of mortality for children under 5 and estimated to cause 1.5 million deaths annually. In India it is the leading cause of child mortality and is estimated to cause 0.5 million deaths annually. While diarrhoea related mortality has been falling in recent years due to more successful treatment, morbidity rates remain high. Currently available mortality and morbidity rates for diarrhoea are likely to be under-estimates due to errors in the data sets and systematic under-reporting. In addition, the most widely used measure for estimating the relative health impacts of diseases (the DALY) may not accurately reflect the impact of diarrhoea as it tends to under-estimate the importance of disease affecting young children. Since there are multiple transmission routes for infectious diarrhoea, which are mediated by a complex interaction of issues related to water quality and availability, sanitation and behaviours and it is difficult to quantify the contribution of unsafe water alone. However, intervention studies have estimated that the incidence of diarrhoea can reduced by around 44% by improving the quality of water actually consumed, while improving source water quality can reduce diarrhoea incidence by 21%.