More Than 80 Organizations Urge WHO to Reconsider Nitrate Limits in Drinking Water

The signatories include Greenpeace International and the World Organization of Family Doctors (WONCA). They are urging the WHO to include nitrates in its upcoming review of drinking-water quality guidelines.

The current limit was established in 1958 and allows nitrate concentrations of up to 50 mg per liter of water. The standard was originally introduced to prevent methemoglobinemia, a dangerous condition in which the blood loses its ability to carry oxygen effectively. Infants are particularly vulnerable to this condition.

However, the letter's authors point out that more recent epidemiological studies suggest a possible link between long-term exposure to nitrates, even at concentrations below the established limit, and colorectal cancer, as well as adverse pregnancy outcomes, including preterm birth. Nitrates can enter surface water and groundwater, partly as a result of intensive agricultural practices.

The organizations cite the findings of an expert group established at the request of the Danish government. Last year, the experts recommended lowering the permitted nitrate concentration to 6 mg per liter - more than eight times below the current WHO limit. In early 2026, Denmark committed to reducing its national limit.

The letter's authors emphasize that many countries rely on WHO recommendations when developing their own drinking-water quality standards. They therefore believe that revising international guidelines could be an important step toward protecting public health. However, the associations identified in the studies do not in themselves prove that nitrates at permitted concentrations directly cause the diseases listed.