Interventions to improve water quality are generally effective in preventing diarrhoea, and interventions to improve water quality at the household level are more effective than those at the source. Significant heterogeneity among the trials suggests that the actual level of effectiveness may depend on a variety of conditions that research to date cannot fully explain. Rigorous, blinded, multi-arm randomized controlled trials conducted over a longer duration in a variety if settings may help clarify the potential effectiveness.
Effect of chlorination of drinking-water on water quality and childhood diarrhoea in a village in Pakistan.
To evaluate the importance of public-domain transmission of pathogens in drinking-water, an intervention study was carried out by chlorinating the public water-supply system in a village in Pakistan. The water quality improved and reached a geometric mean of 3 Escherichia coli per 100 mL at the last standpipe of the water-supply system. Drinking-water source used and the occurrence of diarrhoea were monitored on a weekly basis over a six-month period among 144 children aged less than five years in the village. In this group, the children using chlorinated water from the water-supply scheme had a higher risk of diarrhoea than children using groundwater sources, controlled for confounding by season and availability of a toilet and a water-storage facility. The incidence of diarrhoea in the village (7.3 episodes per 10(3) person-days) was not statistically different from that in a neighbouring village where most children used water from a non-chlorinated water-supply system with very poor water quality. In this study area, under non-epidemic conditions, the reduction of faecal bacteria in the public drinking-water supply by chlorination does not seem to be a priority intervention to reduce childhood diarrhoea. However, the study was of limited size and cannot provide conclusive evidence.