Health Targets for Waterborne Disease

In the developed world, two major approaches have been adopted for setting tolerable limits for infectious disease risks from enteric pathogens drinking water. The US EPA defines tolerable risk in terms of an annual risk of 1 infection per 10,000 people per year, while the World Health Organisation defines the tolerable risk level in terms of a health burden of 1 microDALY (Disability Adjusted Life Year) per person per year resulting from pathogen infection. The US EPA target for waterborne infection risks was developed during drafting of the Surface Water Treatment Rule in the early 1990s. This target relates to infection regardless of whether symptoms occur, and does not differentiate between the variable consequences of infection by different pathogens. The WHO health burden approach was first incorporated into the 3rd Edition of the WHO Drinking-water Guidelines in 2006, but had been proposed in the literature several years before. This approach takes into account differences in morbidity and mortality associated with different pathogens.