Preventing contamination of stored water can cut the incidence of killer diseases.

In Mumbai's recent municipal election, the state of the city's water services was a major issue in the minds of voters — and with good reason. Last year, the Municipal Corporation of Greater Mumbai's (MCGM) annual water report showed that nearly 25 per cent of Mumbai's tap water is unfit for consumption. This report probably caused considerable angst in middle-class households, where people likely responded by changing filters in their water purifiers. Yet for Mumbai's poorer majority who live in slums, tap water contamination is only the starting point of their water woes. In fact, the real story regarding water quality in slums begins only after water leaves a tap.

For most of Mumbai, water is only provided for a few hours a day. Middle-class flats ensure 24-hour water availability by hoarding water in overhead tanks. In contrast, slum residents wait in long lines at community taps. Water timings are unpredictable, if it comes at all, especially in slums without legal access to the municipal supply. Slum residents are therefore forced to store water for prolonged periods, often for days on end. To truly understand the predicament of water-related disease in slums, you have to understand these storage practices.

Partners for Urban Knowledge, Action, and Research (PUKAR), a Mumbai-based research collective, and the Harvard School of Public Health recently completed a major water quality study in an unregistered slum. Most residents are only able to obtain water every three days, and 95 per cent do not get enough water to meet the World Health Organisation's recommended minimum usage of 50 litres per person per day. We tested 229 water samples at an internationally accredited lab for coliforms and E. coli (faecal bacteria), including ones from community water taps and hoses used to distribute water to people's homes. We also tested stored household water by intensively following 21 households and collecting multiple samples from each household in each season.

We found no contamination of tap water in winter or summer, while half the number of taps were contaminated with coliforms during the monsoon. Despite the fact that tap water was usually clean, we found very high rates of contamination in stored drinking water, with 52 per cent of summer samples and 76 per cent of monsoon samples contaminated with faecal bacteria. In other words, all of the summer contamination and much of the monsoon contamination had happened after water leaves the tap.

How does stored household water get contaminated? Most slum residents store drinking water in wide-mouthed containers, from which family members scoop out water using their hands or cups. This quickly introduces bacteria into the water that can infect others. Since such self-contamination happens after water collection, boiling or filtering water at the time of collection does nothing to eliminate this problem. High population density combined with a lack of toilets and open defecation means that slum residents are exposed to the faeces of hundreds of other people, and all of these bacteria can get introduced into stored water. This is not a trivial finding. What this means is that, even if the MCGM were able to magically eliminate all tap water contamination, the majority of Mumbaikars who have to store water (which also includes many non-slum areas) will still be drinking contaminated water. Studies of urban slums from around the world have found diarrhoea to be one of the top two causes of death for children under five years. Diarrhoea exacts a massive economic toll: a recent World Bank study estimated that sanitation and water-related diseases cost India 6.4 per cent of its GDP yearly.

Safe water system

There is growing international public health consensus about the need to make household water storage safer. In the early 2000s, after a resurgence of cholera in South America, U.S. scientists developed a “safe water system.” The key concept is absurdly simple: switch people from using wide-mouthed containers to using safer narrow-mouthed containers that don't allow them to stick their hands in the water. The other component is regular chlorination of stored water. Some studies combining use of narrow-mouthed containers with chlorination reduced diarrhoea by nearly 50 per cent.

The safe water system is cheap: it costs as little as Rs.180 to buy a narrow-mouthed storage container and Rs.30 per person per year to chlorinate water. This is much cheaper than boiling water. Further research is needed to understand how best to scale-up the safe water system and whether its benefits will be maintained when applied to larger populations. Nevertheless, it may have the potential to greatly decrease child deaths, hospital visits, and missed days of work, resulting in increased economic productivity.

While the dismal findings of the MCGM's water report understandably garnered media attention, the tragic reality is that there is an even larger silent epidemic of household water contamination that remains unaddressed. This epidemic undoubtedly extends to innumerable other city slums and villages across India with intermittent water supplies, which lead to prolonged water storage. It presents a unique opportunity for the government to intervene on a mass scale with simple, cost-effective interventions to reduce diseases that are major killers of children.

We recognise that the safe water system will only partly address the profound crisis of water in slum communities. Ideally, water poverty would be eliminated by ensuring a universal 24-hour water supply with taps in every home. Water is a human right, and we cannot compromise on this long-term vision. Yet, in light of the slow rate of infrastructural change, we cannot wait for this utopian vision to happen before acting to prevent diarrhoea in slums through simple household interventions.

(Ramnath Subbaraman is an internal medicine physician and works with Partners for Urban Knowledge, Action, and Research, a Mumbai-based research collective.)

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