Starting with water and sanitation interventions and then trying to gauge the health impact can actually take us away from our desired goal of securing health improvements. Reversing this approach to start with health impact (first) and then determine causality (second) may create a more effective framework to optimize the trade-offs between water, sanitation and a range of other interventions!
The water and sanitation sector has been subject to numerous health impact studies. These are complex undertakings that require careful intervention and control conditions, extensive and carefully managed data sets, considerable time and money. Even in the best cases, quantifying the health impact of water and sanitation interventions is plagued by the high levels of uncertainty that surround the confounding variables. Furthermore, such studies do not quantify the relative health impact of choosing to invest in water and sanitation rather than breast feeding, or female literacy, or any other intervention. Even worse, such studies can draw a positive correlation between an intervention and the health impact … while the overall health for the particular target population has decreased. In such a scenario, it could be legitimately argued that investing in water and sanitation (and not female literacy) was the wrong choice - if the goal was a positive impact on health.