Science: Four billion people lack safe water

In 2020, more than 2 billion people were estimated to lack access to safely managed drinking water services (1). However, the existing data on safely managed drinking water services are scarce especially in low- and middle-income countries. On page 784 of this issue, Greenwood et al. (2) report that an estimated 4.4 billion people lack safe drinking water across 135 low- and middle- income countries, which is more than double the global estimate made in 2020. Their approach involves geospatial modeling of Earth observation—information from land-based, airborne, and satellite data—and household surveys. The authors identify primary factors, including fecal contamination, that affect drinking water safety, which can support policy-makers to improve delivery of safe drinking water services.

Safely managed drinking water services must satisfy three criteria: They should be available on demand, accessible on premises, and free of priority contaminants such as Escherichia coli and specific chemicals (1). Established policies and practices often focus on improving access through building new water infrastructures. However, water service is more than just providing access. According to the Human Rights to Water and Sanitation resolution declared by the United Nations, water services must ensure sufficient quantity, safety, reliability, physical proximity, affordability, and nondiscrimination (3). These goals are challenging in rural areas of Africa and Asia and in sparsely populated regions where safe drinking water services on premises are costly and complicated to maintain.

Greenwood et al. mapped the contributions of the three safe water criteria to assess the role of climate variability, environmental change, and human activities. The results identify fecal contamination as the primary limiting factor in achieving safely managed drinking water for almost half of the population studied. However, insufficient data were available to model contaminations from chemical sources, such as arsenic and fluoride, which limits discussion of potential pollution from industry or agriculture (4)…