Unsafe water is one of the world’s largest health and environmental problems, particularly for the poorest people.

The Global Burden of Disease is a major global study on the causes and risk factors for death and disease published in the medical journal The Lancet. These estimates of the annual number of deaths attributed to a wide range of risk factors are shown here.

Lack of access to safe water sources is a leading risk factor for infectious diseases, including cholera, diarrhea, dysentery, hepatitis A, typhoid, and polio.¹ It also exacerbates malnutrition and, in particular, childhood stunting. The chart shows that it ranks globally as a significant risk factor for death.

Globally, unsafe water sources account for a few percent of deaths.

In low-income countries, it accounts for around twice as many deaths.

The map here shows the share of annual deaths attributed to unsafe water worldwide.

When we compare the share of deaths attributed to unsafe water over time or between countries, we are not only comparing the extent of water access but its severity in the context of other risk factors for death. Clean water’s share depends not only on how many die prematurely from it but also on what else people are dying from and how this is changing.

Death rates from unsafe water sources give us an accurate comparison of differences in mortality impacts between countries and over time. In contrast to the share of deaths that we studied before, death rates are not influenced by how other causes or risk factors for death are changing.

This map shows the death rates from unsafe water sources worldwide. Death rates measure the number of deaths per 100,000 people in a given country or region.

What becomes clear is the significant differences in death rates between countries: rates are high in lower-income countries, particularly across Sub-Saharan Africa and Asia. Rates here are often greater than 50 deaths per 100,000 people.

Compare this with death rates across high-income countries: across Europe, rates are below 0.1 deaths per 100,000. That’s a greater than 1000-fold difference.

Therefore, unsafe water sources are limited primarily to low and lower-middle-income countries.

This relationship is clearly shown when we plot death rates versus income, as shown here. There is a strong negative relationship: death rates decline as countries get richer.