About 4.4 billion people drink uncertain water-twice as many as The previous estimate -according to a study published today in science data action = "anchor-link" data track label = "go to reference" data track category = "references"> 1 . This realization, which indicates that more than half of the world's population has no clean and accessible water access, throws a light on gaps in the basic health data and raises questions about the estimate of reality better reflects.

It is “unacceptable” that so many people have no access, says Esther Greenwood, a water researcher at the Swiss Federal Institute of Aquatic Science and Technology in Dübendorf and author of the science paper. "There is an urgent need that the situation changes."

The United Nations has been pursuing access to safely managed drinking water since 2015, which is recognized as a human right. Before that, the UN only reported whether global drinking water sources were 'improved', which means that they were probably protected against external contamination, e.g. by infrastructures such as backyard fountains, connected lines and rainwater collection systems. This scale seemed that 90% of the world's population had their drinking water in order. However, there was little information about whether the water itself was clean, and almost a decade later, statisticians still rely on incomplete data.

“We really have a lack of data on drinking water quality," says Greenwood. Today, water quality data only exist for about half of the world's population. This makes it difficult to calculate the exact extent of the problem, adds Greenwood.

numbers crunchen

In 2015 the UN to improve people's well -being of people . One of them is to achieve a universal and fair access to clean and affordable drinking water for everyone by 2030. The organization updated their criteria for securely managed drinking water sources: they have to be improved, consistently available, accessible wherever a person lives, and free of contamination.

Using this framework, the joint surveillance program for water supply, sanitary supply and hygiene (JMP), a research collaboration between the World Health Organization (WHO) and the UN Children's Aid Unicef ​​was estimated that there was 2.2 billion people without access to clean drinking water in 2020. In order to achieve this value, the program aggregated data from national census, report regulatory authorities and service providers as well as budget surveys.

But it evaluated the availability of drinking water differently than the method of Greenwood and her colleagues. The JMP checked at least three of the four criteria in a certain location and then used the lowest value to present the overall quality of the drinking water in this area. For example, if a city had no data about whether its water source was consistently available, but 40% of the population had no contaminated water, had 50% improved water sources and had 20% water access at home, the JMP estimated that 20% of the population of this city had access to safe drinking water. The program then scaled this number about the population of a country with a simple mathematical extrapolation.

In contrast, the science paper used survey answers about the four criteria of 64,723 households in 27 countries with low and medium-sized incomes between 2016 and 2020. If a household did not meet one of the four criteria, it was classified as no safe drinking water. The team then trained a mechanical learning algorithm and integrated global geodata -including factors such as regional average temperature, hydrology, topography and population density -to estimate that 4.4 merchant people have no access to clean drinking water, half of which are contaminated with the pathogenic bacterium are.

The model also indicates that almost half of the 4.4 billion people in South Asia and Sub -Sahar Africa live (see 'water problems').

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'a long way to go

It is “difficult” to say what estimate - that of the JMP or the new number - is more precise, says Robert Bain, a statistician in the regional office for the Middle East and North Africa by Unicef, based in Amman, Jordan, who contributed to both figures. The JMP combines many data sources, but has restrictions in its aggregation approach, while the new estimate uses a small data record and scaled it up with a sophisticated model, he says.

The study by Greenwood and colleagues really emphasizes “the need to take a closer look at water quality,” says Chengcheng Zhai, a data scientist at the University of Notre Dame in Indiana. Although the machine learning technology used by the team is “very innovative and intelligent”, she says, access to water is dynamic, so the estimate may still not be entirely correct. Fountains can free from e. be coli and be contaminated the next day, and the household veteran does not capture this, Zhai suggests.

“regardless of which number you use - two billion or four billion - the world has a long way to ensure that people are fulfilled, says Bain.