Clean water can prevent diarrhea and save lives, but among the world's most susceptible populations, it is cleaned best at its point of use rather than its source, researchers report in a large new review of studies.
"While interventions to improve the microbial quality of drinking water are effective in preventing diarrhea, point-of-use interventions at the household level are about twice as effective as traditional interventions at the water source or point of distribution," said lead author and investigator Dr. Thomas Clasen.
The review compared interventions that treat water at its source - such as wells, boreholes and communal tap stands - with those that treat water where it's actually consumed.
"Simple, affordable technologies … can reduce diarrheal disease among all ages and children under 5 years of age by about 40 percent," said Clasen, an expert in household water management with the Department of Infectious and Tropical Diseases, London (U.K.) School of Hygiene and Tropical Medicine.
These household-level technologies include chlorination, ceramic filters, solar disinfection, improved storage containers and flocculation-disinfection. Flocculation is a process for separating clumps of solids from water or sewage.
The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
Clasen and colleagues compared data from 30 controlled studies, randomized or "quasi-randomized," of interventions to improve the microbiological quality of drinking water in settings where diarrhea is endemic, mostly in poor and developing nations. The studies involved more than 53,000 people.
Control groups consisted of people who followed usual practices, such as getting water from untreated sources, usually shallow surface water, or getting water that came from the same source as other participants but did not receive any intervention, such as filtration.
The reviewers found that while both types of interventions were effective, household interventions "were more effective in preventing diarrhea than those at the source." Among household interventions, they reported, there was evidence that filtration, "offers the most consistent and effective results."
The results of the review appear to confirm ongoing efforts by the World Health Organization (WHO) to promote household water treatment and safe storage as a primary means of improving the health of an estimated 1.1 billion people who lack access to safe drinking water.
Among infectious diseases, diarrhea is the third leading cause of both mortality and morbidity worldwide, according to the reviewers. Young children are most susceptible, comprising an estimated 68 percent of all cases of the disease. Diarrhea accounts for 17 percent of all deaths among children under five.
According to the Web site of the Bill and Melinda Gates Foundation, "Severe diarrhea is caused by a number of viruses and bacteria that spread in contaminated water and food and because of inadequate hygiene. Rotavirus is the single greatest cause of severe diarrhea worldwide and accounts for about a quarter of deaths from acute diarrheal illnesses."
Except for one trial in the United States, all were conducted in developing countries including Bangladesh, Bolivia, Brazil, China, Guatemala, Gambia, Ivory Coast, Liberia, Kenya, Malawi, Pakistan, Rwanda, Saudi Arabia, South Africa/Zimbabwe, Uganda, Uzbekistan and Zambia.
The reviewers cautioned that differences in study interventions, methods, measurements and locations "limit the extent to which generalizations can be made." They wrote that further research "including blinded trials and longer-term assessments, is necessary to understand the full impact of these interventions."
However, Peter Muennig, M.D., of the Mailman School of Public Health at Columbia University in New York, disagreed with some of these conclusions: "We don't need more randomized controlled trials. There are plenty out there, and randomizing people to receive dirty water is unethical."
Added Muennig, "In the real world, people are not always pushed to keep the water clean. Also, people tend to bathe in dirty water or brush teeth using dirty water, so it gets in the mouth. So cleaning it at the source is preferable. Perhaps even more important, though, is preventing feces from getting in the water in the first place. This can be quite cheap and can take the form of universal hole-in-the-ground latrines."
In the same vein, Helen Binns, M.D., associate professor of pediatrics and preventive medicine at Northwestern University Medical School, said, "While clean water is a global problem, the solutions applied to improve its availability will be guided by studies such as this, but must be tailored to local conditions and populations." Binns said that ameliorating factors that influence water quality in a particular area "will improve health, particular for vulnerable children."
By Bruce Sylvester