coauthors concluded that household-based interventions were nearly twice as effective as source-based measures. Clasen and coworkers subsequently conducted a cost-effectiveness analysis to determine the cost per disability-adjusted life year (DALY, a measure of disease burden) averted for a similar range of source and household interventions (Clasen et al., 2007b). The researchers found that upon reaching 50 percent of a country’s population, interventions involving household chlorination and solar disinfection paid for themselves and that all interventions were cost-effective.

The most prevalent method of home water treatment worldwide, boiling, was not included in these analyses. Although highly effective in reducing microbiological contamination, boiled water can be readily recontaminated; moreover, Clasen noted, boiling is relatively costly, is associated with risk for burn accidents, and results in indoor air pollution as well as carbon emissions (Clasen, 2008). Because of boiling’s prominence, Clasen’s group has conducted assessments of its microbiological effectiveness and cost in several developing country settings in order to establish a benchmark against which other safe drinking water interventions can be compared. For example, in a recent study in semirural India, where more than 10 percent of households disinfect their drinking water by boiling, the researchers found that boiling, as practiced in these communities, significantly improves the microbiological quality of water (on a par with water filters), but does not fully remove the potential risk of waterborne pathogens (Clasen et al., 2008). They also calculated that while the entry costs of boiling are the least of any water treatment option in this setting, the cost of continuing the practice annually is greater than the ongoing out-of-pocket cost of treating the same volume of water with sodium hypochlorite, or solar disinfection, and the five-year cost of boiling would also exceed most filtration options.

Efforts to increase the availability, uptake, and correct, consistent use of household water treatment and safe storage systems are spearheaded by the International Network to Promote Household Water and Safe Storage, a consortium of interested UN agencies, bilateral development agencies, international non-governmental organizations (NGOs), research institutions, international professional associations, and private sector and industry associations (Clasen, 2008; WHO, 2008). The Network now claims more than 100 members from government, UN agencies, international organizations, research institutions, NGOs, and the private sector and has accomplished much in terms of advocacy, communication, research, and implementation. However, despite these achievements, the mission of the Network to “achieve a significant reduction of waterborne disease, especially among children and the poor” is far from realization. Presently, only a tiny fraction of the millions of people who could benefit from household water treatment and safe storage (HWTS) interventions—far more than the one billion who use “unimproved” water sources, as previously noted—are being served, and those who need them most are the most difficult to reach.

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