WHO urged to review nitrate drinking‑water limit
Over 80 organisations have asked the World Health Organization to update its nitrate guideline, citing new health evidence.
Open letter calls for WHO nitrate guideline review
More than 80 international organisations have signed an open letter urging the World Health Organization (WHO) to reassess its drinking‑water nitrate limit.
Signatories include New Zealand’s Climate and Health Council OraTaiao and Greenpeace Aotearoa under its international banner.
Current guideline and concerns
The maximum acceptable value for nitrate‑nitrogen in New Zealand is 11.3 mg per litre, matching the WHO guideline. The letter notes that this benchmark has not been updated since the 1950s and does not reflect recent evidence linking chronic, low‑level nitrate exposure to long‑term health risks such as colorectal cancer and pre‑term birth.
Signatories request that nitrate be fully evaluated as a chemical contaminant in drinking‑water quality guidelines and that the epidemiological evidence be reviewed.
Comments from Greenpeace
Greenpeace agriculture global project lead Amanda Larsson said most governments base water rules on WHO guidelines.
“The global nitrate guideline hasn't changed since 1958 and hasn't been reviewed in 10 years so we're calling on the World Health Organisation to review nitrate guidelines to take account of this science that has emerged over the last 10 years or so,” Larsson said.
She added that New Zealand researchers have been at the forefront of studying health impacts of nitrate below the current guideline and that there is growing concern about what high nitrate in drinking water means for rural people’s health.
Local actions and data
New Zealand’s Ministry of Health expects to finish a review of nitrate health effects by the end of the year.
Canterbury Regional Council declared a nitrate emergency in 2025 after an annual groundwater survey showed rising nitrate and E. coli concentrations.
The 2025 survey sampled groundwater from 358 wells; 38 wells exceeded the drinking‑water nitrate‑nitrogen limit.
In September, the council voted not to fund treatment of private water supplies for nitrate contamination.
Calls for broader change
Larsson said contamination must be tackled at its source, such as chemical fertilisers and intensive livestock farming. She called for a halt to the expansion of meat and dairy production and for more support to help farmers transition to “nature‑friendly” agriculture and clean up contaminated water.
“We think that most people feel that water should be life‑giving and not life‑threatening. It's a human right,” she added.
Industry response
Federated Farmers president Colin Hurst has previously told RNZ that farmers are working hard to reduce nitrogen loss.
The debate highlights a tension between agricultural practices and emerging health research, with governments and NGOs urging the WHO to bring its nitrate guideline up to date.
