New Study Finds More than 4 Billion People Lack Clean Drinking Water, Doubling Previous Estimate

Number six on the list of United Nations Sustainable Development Goals, adopted universally in 2015, reads: “Ensure availability and sustainable management of water and sanitation for all.” In 2020, five years into the SDG era, the World Health Organization and UNICEF estimated that 2 billion people still lacked access to suitable drinking water, and the world was still well off track to meet the goal by 2030; an update two years later upped the total to 2.2 billion people.

This is, obviously, not great. But a study released in the journal Science on Thursday says it is actually far worse: researchers primarily located in Switzerland combined household survey data with geospatial modeling to examine access to “safely managed drinking water services,” and found that the number of people across 135 low- and middle-income countries that lack such access is 4.4 billion — twice the WHO/UNICEF estimate.

The distribution of these billions is largely as one might expect: 1.2 billion in southern Asia, close to 900 million in sub-Saharan Africa, and more huge groups in other parts of Asia and Latin America. By proportion of population, the story is a little bit different: virtually all of sub-Saharan Africa lacks clean drinking water, followed closely by Pacific island nations in Micronesia, Melanesia, and Polynesia. Around three-quarters of southeast Asia and Latin America/Caribbean are victims of this scourge.

Fecal contamination is the primary driver of the problem, the study found. But critically, climate change could be making that issue worse: “Climate variables, on the other hand, made the largest contribution to the prediction of fecal contamination, with higher annual mean temperatures contributing to higher estimations of E. coli contamination,” the authors wrote. Warming’s effects on clean water overall is reasonably well understood, with increased evaporation of reservoirs and lakes along with heavier flooding events making access to water an increasing challenge.

But the scope of the issue here is astonishing: double what was previously believed, with more than a year of accelerated warming just behind us and only half a decade to go until the U.N.’s 2030 general deadline for the SDGs. “[O]ur results point toward a substantial underestimation of the number of people whose basic human rights to safe drinking water are not being met,” the authors wrote.

In an accompanying comment, Rob Hope of Oxford University called the issue a “daunting challenge,” and one that affects some vulnerable people more than others. Addressing those inequalities will be key if a meaningful dent is to be made in the 4.4 billion number; targeting that number, Hope wrote, “must reflect the social inequalities of water services that disproportionately fall on women, girls, pastoralists, and other groups who often live in water-insecure environments.”