Implications of WASH Benefits trials for water and sanitation
Authors: Oliver Cumming, Val Curtis
Journal: The Lancet Global Health (2018)

Two large, well designed, and well executed factorial trials, one in Bangladesh1Luby SP Rahman M Arnold BF et al.Effects of water quality, sanitation, handwashing, and nutritional interventions on diarrhoea and child growth in rural Bangladesh: a cluster randomised controlled trial.Lancet Glob Health. 2018; 6: e302-e315Summary Full Text Full Text PDF PubMed Scopus (344) Google Scholar and another in Kenya,2Null C Stewart CP Pickering AJ et al.Effects of water quality, sanitation, handwashing, and nutritional interventions on diarrhoea and child growth in rural Kenya: a cluster-randomised controlled trial.Lancet Glob Health. 2018; 6: e316-e329Summary Full Text Full Text PDF PubMed Scopus (318) Google Scholar published in The Lancet Global Health, have reported no effect of drinking water, sanitation, and hygiene (WASH) interventions on linear child growth. In recent years, researchers, policy makers, and practitioners have enthusiastically espoused the biologically plausible idea that reducing environmental contamination through WASH might be key to tackling the persisent challenge of childhood stunting. Should we now conclude that these calls to prioritise WASH as a nutrition intervention were premature or misguided? First, we congratulate the authors on the quality of these trials. Unlike many previous WASH studies, the trials were registered, data analysis was prespecified, the effects of the interventions on associated behaviours were assessed, objective health outcome measures were used, the trials were adequately powered to detect small effects, geographic buffering reduced the risk of contamination between groups and, at least in the Kenyan study, an active control group was used. The internal validity of these studies is thus likely to be very high. However, as is often the case in such trials,3Eldridge S Ashby D Bennett C Wakelin M Feder G Internal and external validity of cluster randomised trials: systematic review of recent trials.BMJ. 2008; 336: 876-880Crossref PubMed Scopus (148) Google Scholar the external validity of these findings is less clear. In both countries, most trial participants already had access to basic latrines and rates of open defecation were low. Similarly, in both countries, most participants already had an "improved" drinking water source at baseline. The tested WASH interventions might be expected to have a much greater effect on pathogen transmission among populations where open defecation and poor water supply are widespread, which remain significant, especially in sub-Saharan Africa and South Asia.4WHOUNICEFProgress on drinking water, sanitation and hygiene: 2017 update and SDG baselines.https://www.unicef.org/publications/index_96611.htmlDate: June 14, 2017Date accessed: April 18, 2018Google Scholar The choice of interventions raises questions, too. The "water" intervention might have changed the microbial quality of drinking water somewhat, but the quantity of water available at the household, long argued as the driver for water-related health gains,5White GF Bradley DJ White AU Drawers of water: domestic water use in East Africa. University of Chicago Press, Chicago, IL1972Google Scholar was unchanged. The sanitation intervention was delivered to the compounds of participants and not to the wider community, which, in Bangladesh, was only 10% of the village population. As sanitation facilities arguably benefit the owner's neighbours more than the owners themselves, it is plausible that the sanitation intervention did not achieve sufficient density to significantly improve environmental conditions around the enrolled children. Previous trials reporting an effect of sanitation on linear growth adopted a community-wide approach whereby conditions were improved across whole villages, rather than isolated compounds.6Pickering AJ Djebbari H Lopez C Coulibaly M Alzua ML Effect of a community-led sanitation intervention on child diarrhoea and child growth in rural Mali: a cluster-randomised controlled trial.Lancet Glob Health. 2015; 3: e701-e711Summary Full Text Full Text PDF PubMed Scopus (220) Google Scholar, 7Hammer J Spears D Village sanitation and child health: effects and external validity in a randomized field experiment in rural India.J Health Econ. 2016; 48: 135-148Crossref PubMed Scopus (66) Google Scholar Also, since both trials were done in rural settings they cannot demonstrate what would happen if sanitation was improved in the dense, informal, and often poorly served urban populations of, for example, Dhaka or Nairobi. Beyond the usual WASH interventions, recent research8Touré O Coulibaly S Arby A Maiga F Cairncross S Improving microbiological food safety in peri-urban Mali; an experimental study.Food Control. 2011; 22: 1565-1572Crossref Scopus (21) Google Scholar, 9Islam MS Mahmud ZH Gope PS et al.Hygiene intervention reduces contamination of weaning food in Bangladesh.Trop Med Int Health. 2013; 18: 250-258PubMed Google Scholar suggests that food might be a dominant exposure pathway for enteric infection in early childhood but this pathway was unlikely to have been significantly influenced by these interventions. Another reason why children might fail to grow adequately in such settings is exposure to animal waste, with studies showing an association between exposure through animal husbandry and diarrhoeal diseases.10Zambrano LD Levy K Menezes NP Freeman MC Human diarrhea infections associated with domestic animal husbandry: a systematic review and meta-analysis.Trans R Soc Trop Med Hyg. 2014; 108: 313-325Crossref PubMed Scopus (117) Google Scholar In both settings, as acknowledged by the authors, children were likely to be exposed to animal waste and this exposure was not significantly addressed by the interventions. Tackling the environmental contribution to stunting might require more concerted efforts to keep children and animal waste apart. Setting aside the above caveats, these negative results show that limited WASH interventions—basic latrines, treatment of water, and rudimentary handwashing facilities—did not improve linear growth, or, indeed, many other important health outcomes, in these settings. This is a challenge to all of us in the WASH sector. For researchers and research funders, these results remind us again how little we still know about the transmission of enteric pathogens, the causes of symptomatic infections, and the significance of asymptomatic infections. We hope that forthcoming papers from the WASH-Benefits group will contribute new knowledge with regard to these questions. At a policy level, these studies suggest that business as usual in the WASH sector will not be enough to significantly improve child growth. At a policy level, these findings lend support to the new, and more ambitious, Sustainable Development Goal (SDG) that calls for progress towards a piped continuous water supply located on premises coupled with a safely managed sanitation service for all.4WHOUNICEFProgress on drinking water, sanitation and hygiene: 2017 update and SDG baselines.https://www.unicef.org/publications/index_96611.htmlDate: June 14, 2017Date accessed: April 18, 2018Google Scholar Looking forward, if the prospects of those millions of children still born into poverty, and who too often fail to thrive as they should, are to be improved, then it is clear that this new and ambitious level of service is where we should now be aiming. We declare no competing interests. Effects of water quality, sanitation, handwashing, and nutritional interventions on diarrhoea and child growth in rural Kenya: a cluster-randomised controlled trialBehaviour change messaging combined with technologically simple interventions such as water treatment, household sanitation upgrades from unimproved to improved latrines, and handwashing stations did not reduce childhood diarrhoea or improve growth, even when adherence was at least as high as has been achieved by other programmes. Counselling and supplementation in the nutrition group and combined water, sanitation, handwashing, and nutrition interventions led to small growth benefits, but there was no advantage to integrating water, sanitation, and handwashing with nutrition. Full-Text PDF Open Access