This spring the World Health Organization (WHO) celebrated the early completion the 2015 development goal of bringing improved drinking water to an additional two billion people since 1990.

“Today we recognize a great achievement for the people of the world,” United Nations Secretary General Ban Ki-moon said at the occasion. “The successful efforts to provide greater access to drinking water.”

The feat was a landmark in securing what the U.N. General Assembly declared in 2010 was a universal human right: “access to safe and clean water.” In an effort to improve health and quality of life across the world between 1990 and 2015, the U.N. established eight Millennium Development Goals (MDG). One of the sub targets was to “halve, by 2015, the proportion of the population without access to safe drinking water and basic sanitation.”

And by early 2012 only approximately 800 million people around the globe still relied on “unimproved” water sources such as streams, ditches or unprotected wells, which are the most likely places for contaminated water. Pipes, boreholes and protected wells are much more likely to prevent contact with dangerous pathogens, chemicals or sewage runoff.

But just because water is pouring out of a spigot does not mean that it is safe to drink. In poorer areas, where infrastructure and sanitation are often much worse, even sources of water that have been “improved” are frequently at risk for contamination by human and animal feces, according to recent analyses.

Improved but not necessarily safe
One report, published earlier this year in the Bulletin of the World Health Organization, analyzed water quality test data from five countries (Ethiopia, Jordan, Nicaragua, Nigeria and Tajikistan) and found that many sources of “improved” water failed the safety test. When these improved waters were tested and compared with survey data about where people got most of their water, the estimates for the populations that have access to safe drinking water fell by 16 percent in Nicaragua, 15 percent in Nigeria, 11 percent in Ethiopia and 7 percent in Tajikistan. (Jordan, which primarily uses public utilities to pipe water, remained at a relatively high percentage.) Additionally, the study authors noted, the number of people who had access to safe—and not just improved—water in 1990 was likely much lower than previously estimated, which means that the 2015 target is even farther away than estimated by the current rubric.

Extrapolating from these five very different countries spread over three continents to the rest of the globe is difficult. But one group of researchers at the Gillings School of Global Public Health’s Water Institute at the University of North Carolina at Chapel Hill took a shot at it in their March International Journal of Environmental Research and Public Health paper. They estimate that some 1.8 billion people—28 percent of the population worldwide—was using unsafe water as of 2010. That is far more than the 783 million (or 11 percent) estimated by WHO and UNICEF to have access to improved water sources. The researchers acknowledge that their “estimate is imprecise,” but “the magnitude of the estimate and the health and development implications suggest that greater attention is needed to better understand and manage drinking water safety.” And other experts in the field agree that their estimate is a good ballpark figure for the true disparity.