Drinking Water Quality or Availability – Which is more important for human health?

Paul R Hunter, Professor of Health Protection, Norwich School of Medicine, University of East Anglia

Abstract
The Quality versus Quantity debate has continued to one degree or another for almost 30 years. The debate concerns whether or not it is more important to focus our efforts on improving the quality of drinking water or the quantity/availability of water. In the first part of this presentation, I will review the history of this debate. In his landmark review article, Esrey (1991) found that increasing water availability was much more important than efforts to improve water quality. However, opinion swung strongly towards quality of being of primary importance following the publication by Clasen (2007) of his systematic review of interventions to improve water quality. Indeed the first decade of this millennium saw a dramatic increase in efforts by NGOs and others to promote household disinfection in low income countries. Then just two years later, Schmidt & Cairncross (2009) pointed out that almost all of the studies included in Clasen’s paper were unblinded and so open to reporting bias. If the analyses were restricted to blinded studies then no reduction in diarrhoeal disease was seen.  For the final part of the presentation, I will discuss more recent contributions made by myself and others to the quality/quantity debate. For example, in my own meta-regression analysis (Hunter 2009), it was shown that accounting for lack of blinding and duration of follow-up most point-of use household water treatment interventions do not substantially reduce diarrhoeal disease but ceramic filtration does have an effect over and above chlorination suggestion that quality does matter.  Similarly, in a study of malnourished children in Niger, we showed that both quantity and quality were important and that the effect of both together was greater than each alone (Dorion 2012). I will then suggest possible mechanisms whereby drinking water interventions do not apparently deliver improved health gains and discuss other health benefits of drinking water quality and access. This presentation will conclude that both quality and access are essential criteria for drinking water safety and that the benefits are more wide ranging than focussing solely on diarrhoeal disease would suggest. 
Clasen, T., Schmidt, W. P., Rabie, T., Roberts, I., & Cairncross, S. (2007). Interventions to improve water quality for preventing diarrhoea: systematic review and meta-analysis. BMJ, 334(7597), 782.
Dorion, C., Hunter, P. R., Van den Bergh, R., Roure, C., Delchevalerie, P., Reid, T., & Maes, P. (2012). Does village water supply affect children’s length of stay in a therapeutic feeding program in Niger? Lessons from a Médecins Sans Frontières program. PloS one, 7(12), e50982.
Esrey, S. A., Potash, J. B., Roberts, L., & Shiff, C. (1991). Effects of improved water supply and sanitation on ascariasis, diarrhoea, dracunculiasis, hookworm infection, schistosomiasis, and trachoma. Bulletin of the World Health organization, 69(5), 609.
Hunter, P. R. (2009). Household water treatment in developing countries: comparing different intervention types using meta-regression. Environmental science & technology, 43(23), 8991-8997.
Schmidt, W. P., & Cairncross, S. (2009). Household water treatment in poor populations: is there enough evidence for scaling up now?. Environmental science & technology, 43(4), 986-992.