More than a quarter of the world’s population — about 2.1 billion people — lack access to clean water, according to a report released this week by the World Health Organization and UNICEF. Accessibility of drinking water, availability when needed and levels of contamination were used to assess water services. National data were available for about 100 countries in 2015, and these are the 10 with the least safely managed water supply.

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10 Countries With the Worst Water Supply originally appeared on usnews.com