Environmental interventions in developing countries : interactions and their implications

This study assesses the effect of drinking water quality on diarrhoeal disease in good and poor sanitary conditions using a random sample of 2,355 Filipino infants over the first year of life. The study confirms the importance of environmental factors on diarrhoea. The effects of water quality, household sanitation, and community sanitation are strong, consistent, and statistically significant. The positive impact of improved water quality is greatest for families living under good sanitary conditions, with the effect statistically significant when sanitation is measured at the community level but not significant when sanitation is measured at the household level. Improving drinking water quality would have no effect in neighbourhoods with very poor environmental sanitation; however, in areas with better community sanitation, reducing the concentration of faecal coliforms by two orders of magnitude would lead to a 40 per cent reduction in diarrhoea. Providing private excreta disposal would be expected to reduce diarrhoea by 42 per cent, while eliminating excreta around the house would lead to a 30 per cent reduction in diarrhoea. Improvements in both water supply and sanitation appear to be necessary if infant health in developing countries is to be improved. Not epidemiologic but behavioural, institutional, and economic factors should correctly determine the priority of interventions.