Water Supply and Health

Arguments over the relative importance of increasing consumption ('quantity') versus improving water safety ('quality') have been taking place since at least the beginning of the first United Nations water decade (the 1980s). For those living distant from a water source, using only around 3‐4 litres per person per day, and often suffering from hygiene related disease, the logical priority is to increase quantity consumed, especially for personal and home hygiene. For those at the other end of the spectrum, with water close at hand water quality arguments often carry greater weight. In the late 1980s Stephen Esrey and colleagues carried out one of the first substantial analyses relevant to this debate [1]. In considering impact on a range of water‐ and excreta‐related diseases, these authors concluded that enhancing access to water (thereby increasing quantity consumed) was more important than improving water quality. More recent systematic reviews came to different conclusions, suggesting that improving drinking water quality at the community and the household level can reduce the incidence of diarrhoeal disease by around 30 to 40% and that this improvement can be seen, even in the absence of other interventions, such as handwashing or sanitation [2,3]. The conclusion of these later reviews has driven many authors and agencies to push for the general uptake of point of use (household) water treatment (HWT), as a major water supply intervention [4]. However, a recent reanalysis of this data has suggested that much of the apparent value of household water treatment may be due to recall bias in unblinded studies and that as yet there is insufficient evidence to justify its widespread promotion [5]. This analysis has led to a strong response from other workers in support of household water treatment [6]. A further systematic review from another independent group cast further doubt on the efficacy of HWT, pointing out problems due to lack of blinding, the lack of an association between diarrhoea and reported compliance, strong evidence of publication bias and potential effects from conflicts of interest [7]. So what is the evidence base for widespread household water treatment and why the confusion? There are various technologies available for treating water in the home, that include boiling, disinfection or filtration [4]. Disinfection technologies include chlorination with safe storage, commercial, combined coagulant‐chlorine systems and SODIS where drinking water is left in clear polyethylene terephthalate (PET or PETE) bottles in the sun to be disinfected …