People who drink water that is contaminated with human faeces are at risk of diarrhoea, a condition that results in 1.8 million deaths in children each year.1 In this week's BMJ, a systematic review and meta-analysis by Clasen and colleagues2 finds that household interventions to improve the microbiological quality of drinking water reduce the occurrence of diarrhoea. Their results show that the quality of water has an impact on health. They also highlight the value to public health of achieving the targets outlined in the seventh millennium development goal—to reduce by half the proportion of people without sustainable access to safe drinking water.

Two articles published in 1985 and 1991 are the most cited reviews on the effectiveness of interventions to prevent diarrhoea.3 4 These considered only improvements to the water source, however. They did not assess the microbiological quality of the water at the point …