BMJ  2005;331:468-469 (3 September), doi:10.1136/bmj.331.7515.468

Editorial

Clean drinking water for homes in Africa and other less developed countries

Flocculant-disinfectant treatment with bleach is effective and acceptable

More than 1 billion people in developing countries lack access to safe water, and 2.2 million die annually of diarrhoea.¹ Unfortunately, communities where diarrhoea is a leading cause of morbidity and mortality often lack the capacity and the resources to establish and sustain centrally purified water free from sewage.²

Contamination of water during collection, transport, and storage at home presents a serious risk to health for millions of households in developing countries. Several studies have shown an increased risk of diarrhoea because of inadequate water storage.³ Regardless of where or how the water is collected, storage vessels with wide openings such as pots or buckets are easily contaminated with faeces, through the introduction of cups, dippers, or hands. Water might also be contaminated by flies, cockroaches, and rodents.

Several organisations have adopted a three pronged approach for treating water at the point of use.⁴ This includes using simple household bleach (sodium hypochlorite) to disinfect the water, using narrow mouthed storage vessels, and working with communities to educate people about the causes and prevention of diarrhoea.⁵ It has proved difficult to convince people to add bleach to drinking water because it affects the taste.² Moreover, bleach may not be effective in water that is turbid or contains chlorine resistant organisms such as Cyclospora cayetanensis or Cryptosporidium parvum.⁶

Until recently, interventions to improve the safety of water and sanitation have focused on safe disposal of excreta and proper use of water for personal hygiene rather than on paying attention to water quality.⁷ The focus is now changing.⁸ A recent review by the World Health Organization found that low cost simple and acceptable interventions in households can improve the biological quality of water stored in the home and hence reduce the risk of diarrhoea and death.² Such interventions include boiling, chlorination, and coagulation-flocculation. Unfortunately, boiling consumes a lot of energy (it takes 1 kg of wood to boil 1 litre of water) and the cost may be prohibitive, particularly in the developing countries where wood and other biomass fuels are not always available. Moreover, burning wood can lead to deforestation with serious environmental degradation.²

Various interventions may remove particles and microbes from water. Although cloth has been found to remove zooplankton and phytoplankton carrying Vibrio cholerae⁹ and is used extensively for the eradication of guinea worm, cloth is not recommended for routine treatment of water in the home because its pores are too large to remove bacteria and viruses. Chemical precipitation (coagulation and flocculation) removes particles and microbes. It can be used in households to reduce transmission of diarrhoeal disease but its use in developing countries has been limited by issues of safety, effectiveness, cost, and sustainability.¹⁰

This is why the paper by Crump et al in this week's BMJ is an important advance in treating water in households.¹¹ In a randomised controlled trial, the authors compared standard practice with flocculant-disinfectant treatment of drinking water with sodium hypochlorite (bleach) in homes in a rural area of western Kenya, where the water is highly turbid and contaminated with faecal bacteria. The treatment lowered the turbidity of drinking water, improved the acceptability of water treatment at home, and reduced the prevalence of diarrhoea by 25% among participants.

The authors also report fewer deaths in the intervention group than in the control group. It is not clear, however, whether the study had enough power to detect a significant difference in mortality, and these results on mortality reduction need to be confirmed in an appropriately powered, randomised controlled trial. The authors claim that, if the flocculant-disinfectant treatment were available in the marketplace, the visible effect on water turbidity might lead families to treat water in their homes. Yet there is no evidence to show that, in this community or indeed in other communities in the region, people would be encouraged by such results to purchase.

This study is, nevertheless, an important addition to the list of randomised controlled trials on the effect of flocculant-disinfectant on the quality and acceptability of drinking water. The challenge now is to demonstrate affordability, sustainability, and the feasibility of scaling up such interventions to reach the millions of households in developing countries that lack safe drinking water.

Department of Paediatrics and Child Health, Makerere Medical School, PO Box 7072, Kampala, Uganda (jtumwine{at}imul.com)

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Papers p 478

Competing interests: None declared.

References

1. Kosek M, Bern C, Guerrant RL. The global burden of diarrhoea disease, as estimated from studies published between 1992 and 2000. Bull WHO 2003;81: 197-204.[ISI][Medline]
2. Sobsey DM. Managing water in the home: accelerated health gains from improved water supply. Geneva: World Health Organization, 2005. www.who.int/water_sanitation-health/dwq/wsh0207/en (accessed 16 Aug 2005).
3. Knight SM, Toodayan W, Caique WC, Kyin W, Barnesa A, Desmachelier P. Risk factors for the transmission of diarrhoea in children: a case control study in Malaysia. Int J Epidemiol 1992;21: 812-8.[Abstract/Free Full Text]
4. Quick RE, Kimura A, Thevos A, Tembo M, Shamputa I, Hutwagner L, et al. Diarrhoea prevention through household-level water disinfection and safe storage in Zambia. Am J Trop Med Hyg 2002;66: 584-9.[Abstract]
5. Mintz ED, Reiff FM, Tauxe RV. Safe water treatment and storage in the home: a practical new strategy to prevent water-borne disease. JAMA 1995;273: 948-53.[Abstract]
6. Meinhardt PL, Casemore DP, Miller KB. Epidemiological aspects of human cryptosporidiosis and the role of waterborne transmission. Epidemiol Rev 1996;18: 118-36.[Free Full Text]
7. Esrey SA, Habicht J-P. Epidemiologic evidence for health benefits from improved water and sanitation in developing countries. Epidemiol Rev 1986;8: 117-28.[Free Full Text]
8. Clasen TF, Cairncross S. Household water management: refining the dominant paradigm. Trop Med Int Health 2004;9: 187-91.[CrossRef][ISI][Medline]
9. Huq A, Xu B. A simple filtration method to remove plankton-associated Vibrio cholerae in raw water supplies in developing countries. Appl Environ Microbiol 1996;62: 2508-12.[Abstract]
10. Reller ME, Mendoza CE, Lopez BM, Alvarez M, Hoekstar RM. A randomized controlled trial of household-based flocculant-disinfectant drinking water treatment for diarrhoea prevention in rural Guatemala. Am J Trop Med Hyg 2003;69: 411-19.[Abstract/Free Full Text]
11. Crump JA, Otieno PO, Slutsker L, Keswick BH, Rosen DH, Hoekstar RM, et al. A cluster randomised trial of household-based flocculant-disinfectant drinking water treatment for diarrhoea prevention in the setting of highly turbid source water in rural western Kenya. BMJ 2005;331: 478-81.[Abstract/Free Full Text]

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