Health targets for waterborne disease

The World Health Organisation defines the tolerable risk level for waterborne disease in terms of a health burden of 1 microDALY (Disability Adjusted Life Year) per person per year resulting from pathogen infection.

The suitability of target levels for tolerable risks set by this approach have recently been the subject of debate within WHO, and a recent article in the Journal of Water and Health  (Duncan Mara, University of Leeds*) focuses on concerns over the appropriateness of the chosen WHO target level for drinking water and for wastewater irrigation.

In contrast, the US EPA approach sets a tolerable risk in terms of waterborne infection rather than illness. It was developed during drafting of the Surface Water Treatment Rule in the early 1990s, and relates to infection, regardless of whether symptoms occur, and does not differentiate between the variable consequences of infection by different pathogens.

These two approaches, and some of the recent debate around them, are discussed in issue 63 of WQRA's HealthStream.

*Water- and wastewater-related disease and infection risks: what is an appropriate value for the maximum tolerable additional burden of disease? Mara D (2011) Journal of Water and Health 9(2):217-1224.