Nitrates in drinking water can cause colorectal cancer: Expert panel wants the limit significantly lowered
DR-Inland in Denmark
Thursday, February 12, 2026 • 5:28 AM UTC - in Denmark
Excessive nitrate in drinking water can increase your risk of colorectal cancer—and an expert panel now recommends sharply lowering the limit.
Every time you turn on the tap and drink a glass of tap water, high levels of nitrate in the water pose a small but increased risk of developing colorectal cancer.
That’s why an international expert group appointed by the Ministry of Environment and Food recommends reducing the nitrate limit in drinking water.
Currently, the limit is set at 50 milligrams per liter, in line with EU standards, but it should be lowered significantly to just six milligrams per liter to prevent cases of colorectal cancer.
This is the view of Tina Kold Jensen, a professor in environmental medicine at the University of Southern Denmark and one of the experts behind the recommendation.
“We’ve set the limit at six milligrams because we believe this could prevent between 50 and 70 cases of cancer (per year in Denmark) in the colon,” she says. “That’s a major public health benefit.”
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**Colorectal cancer and nitrate**
Colorectal cancer is one of the most common forms of cancer in Denmark.
Around 4,500 Danes are diagnosed with colorectal cancer (colon and rectal cancer) annually.
Approximately 130 cases of colorectal cancer each year are attributed to nitrate, accounting for nearly three percent of all cases.
Sources: The Danish Health Authority and a Danish study from 2024.
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**Nitrate comes from fertilizer**
The nitrate originates from the fertilizers—whether synthetic or slurry—that farmers apply near drinking water wells. When nitrate enters the drinking water, it converts into nitrites and nitrosamines in the gut, which are carcinogenic, says Tina Kold Jensen.
According to the Danish Environmental Protection Agency, most Danes have drinking water with nitrate levels below the new proposed limit. However, in 300 of the country’s 2,500 drinking water wells, nitrate levels exceed six milligrams per liter, and in some of these, the levels are dangerously high, Tina Kold Jensen believes.
“It’s crucial that we ensure, in the future, that groundwater and drinking water maintain a quality that allows us to continue drinking tap water safely.”
> “This is an urgent matter. When our independent experts reach such a clear conclusion, we must respond. There’s no other choice.”
> **Magnus Heunicke (S), Minister of Environment and Food**
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**Minister to follow expert advice**
After several studies suggested a possible link between nitrate in drinking water and an increased risk of colorectal cancer, Environment Minister Magnus Heunicke (S) asked the expert panel in 2024 to review whether the limit should be changed.
Now, the minister is ready to follow the panel’s recommendation and lower the limit.
“When the expert group—one I myself appointed—provides such a clear recommendation, we have no choice but to act.”
“This is an urgent matter. When our independent experts reach such a clear conclusion, we must respond. There’s no other choice.”
Aalborg Water Supply previously stated that it would spend 645 million Danish kroner to remove nitrate from drinking water in the area, as levels were too high. The cost will be passed on to customers.
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**Aalborg is the first to act**
Aalborg Municipality has been particularly affected by nitrate in groundwater, as soil conditions in the region allow nitrate from farmers’ fertilizers to seep into groundwater more quickly than elsewhere.
That’s why the area has some of the highest nitrate levels in drinking water—and with 74 cases of colorectal cancer annually due to nitrate out of around 130—it also has a higher incidence of cancer linked to nitrate exposure.
Read also: Bill for 645 million kroner to clean drinking water lands on Aalborg residents.
Last year, Aalborg Municipality became the first in the country to begin treating drinking water for nitrate to reduce levels to 15 milligrams per liter.
The project will cost 645 million kroner, and the expense will be directly passed on to residents, who can expect an additional annual bill of around 1,000 kroner for a typical household—over a period of ten years.
Nitrate in drinking water comes from farmers spreading slurry on fields. (Photo: © Bo Amstrup, Ritzau Scanpix)
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**Focus on agriculture**
But according to Torben Sigsgaard, a professor in environmental medicine at the Department of Public Health at Aarhus University, it’s completely wrong for consumers to bear the cost of cleaning drinking water.
Instead, the focus should be on preventing nitrate pollution from the fertilizers farmers use near drinking water wells.
“It would be better to ensure that agriculture stops contaminating the water and that we don’t have nitrate seeping into groundwater. That’s what we need to work on.”
“Of course, water can be treated, but it’s expensive. And far more costly than protecting the areas where we source our drinking water.”
Magnus Heunicke acknowledges that agriculture plays a role in nitrate levels in drinking water.
“It’s clear that nitrate comes from fertilizers, and we’ve taken steps to address this—including those outlined in the major green tripartite initiative to reform agriculture, which has led to lower fertilizer use.”
“But that’s not enough. That’s why my task is to ensure we reach the levels recommended by independent researchers and to outline the measures that need to be taken by individual water utilities.”
Warning: This article was translated by a Large Language Model, in case of doubt, you can always visit the original source.