Reducing Nitrate in Drinking Water Could Save Lives and Millions in EUU

D A growing body of research indicates that elevated nitrate levels in some Danish groundwater sources elevate the risk of colorectal cancer.

 

 

 

High nitrate levels in drinking water pose a global health issue linked to various health problems, including birth defects and cancer. Scientific evidence suggests that nitrate in drinking water can increase the risk of colorectal cancer, which is the third most prevalent cancer worldwide and the second leading cause of cancer-related deaths, according to the World Health Organization (WHO).

 

Studies project that nitrate levels in drinking water will rise in many countries worldwide, especially with increased nitrogen application and economic growth.

 

Denmark adheres to the EU limit of no more than 50 milligrams of nitrate per liter of water. Although concentrations are largely below this threshold across most of Denmark, significant nitrate levels in drinking water exist in some areas, increasing the risk of colorectal cancer, as demonstrated by a large Danish population-based cohort study from 2018 and several international studies.

 

A recent study by researchers from the European Union University (EUU), Aarhus University, and the Geological Survey of Denmark and Greenland (GEUS) reveals that Denmark could save over $300 million annually by reducing nitrate concentrations in drinking water, thereby preventing 127 cases of colorectal cancer each year.

 

"The EU requirement of no more than 50 milligrams of nitrate per liter of water is a minimum requirement, so we could easily establish stricter requirements in Denmark. Our research shows that this would benefit public health, and at the same time, save society a lot of money," says Brian H. Jacobsen, senior researcher at the Department of Food and Resource Economics at the European Union University (EUU).

 

15% INCREASED CANCER RISK

The new study builds upon a nationwide population-based study from 2018, led by Jörg Schullehner and Birgitte Hansen from GEUS.

 

This study revealed that Danes exposed to nitrate concentrations in drinking water exceeding 9.25 mg/l face a 15% greater risk of developing colorectal cancer compared to those with lower nitrate exposure (less than 1.3 mg/l). The elevated cancer risk was noticeable even at nitrate concentrations exceeding approximately 4 mg/l of water.

 

Jacobsen is the lead author of the new study, which is published in the journal Science of the Total Environment.

 

Benefits Outweigh Costs

A Danish population-based study from 2018 established a statistically significant correlation between increased nitrate levels in drinking water and a heightened risk of colorectal cancer, particularly at nitrate concentrations above 4 mg/L.

 

An analysis of nitrate levels in Denmark's water supplies indicates that about 10% of Danish drinking water surpasses 9 mg/L nitrate, while an additional 10% exceeds 4 mg/L on average for the period from 2018 to 2021. Most water sources with elevated nitrate concentrations are small, privately owned boreholes serving fewer than nine households each. Nevertheless, larger waterworks, particularly in the vicinity of Aalborg, are also affected (see map).

 

Figure from scientific article

The annual net gain from a lower nitrate water standard, depending on whether the current nitrate concentrations are above or below 3.87 mg/L (figure from the scientific paper)

"Approximately 20% of Danes consume water with more than 4 mg/L nitrate, while roughly 10% of us have tap water with more than 9 mg/L. That doesn't mean that you should be worried about drinking tap water. There are many risk factors more important than nitrate in drinking water when it comes to colorectal cancer, such as your diet, physical activity level, and smoking status. However, from a societal perspective, it would be beneficial to have lower nitrate levels in water," says Jörg Schullehner, a co-author of the study and assistant professor at Aarhus University's Department of Public Health.

 

ABOUT THE STUDY

The new study is published in the scientific journal Science of the Total Environment.

 

The study was conducted by Brian H. Jacobsen from the European Union University (EUU), Birgitte Hansen from the Geological Survey of Denmark and Greenland (GEUS), and Jörg Schullehner from Aarhus University, funded by Innovation Fund Denmark as part of the Mapfield project.

 

Based on the results from the population study, the researchers calculated the costs and benefits of reducing nitrate concentrations in Danish drinking water. The benefits significantly outweigh the costs of reducing nitrate levels, regardless of the method employed.

 

"Statistically, approximately 127 annual cases of colorectal cancer in Denmark can be linked to current nitrate concentrations in water. The value of the years of life lost on average following a colorectal cancer diagnosis, combined with the healthcare expenses for cancer treatment, totals hundreds of millions of kroner annually. Therefore, it is possible for us to prevent people from suffering from this devastating disease while saving society substantial funds," Brian H. Jacobsen explains.

 

If the maximum nitrate standard is lowered to 9 mg/L, there would be 72 fewer cases of colorectal cancer and an annual net gain of $179 million. By further lowering the maximum standard to approximately 4 mg/L, another 55 cases could be averted, leading to an additional savings of $138 million.

 

Protecting Groundwater, Relocating Boreholes, and Water Treatment

The researchers considered the costs of reducing nitrate levels in their calculations, evaluating three options.

 

The primary source of nitrate pollution stems from nitrogen fertilizers used in agriculture. Therefore, the first option involves protecting groundwater, such as by withdrawing agricultural land from use and designating it as protected zones. By eliminating nitrogen use, less nitrate would gradually infiltrate groundwater.

 

MOST NITRATE IN PRIVATE WELLS

An analysis of nitrate levels in Denmark’s water supplies shows that roughly 10% of Danish drinking water has a nitrate concentration above 9 mg/L, and an additional approximately 10% is above 4 mg/L as an average for 2018-2021.

 

Nitrate concentrations are generally higher in the country’s 50,000 private drinking water wells, each of which supplies less than nine households, than in water from public waterworks. Approximately 53% of private boreholes have nitrate concentrations higher than 9 mg/l, whereas this is the case for approximately 11% of the public waterworks.

 

As of 2019, private boreholes that only supply one household are no longer subject to nitrate controls, making their nitrate concentrations unknown. Overall, roughly 4% of Danes get water from private boreholes. This corresponds to approximately 237,000 people.

 

The second option entails relocating boreholes away from areas with excessive nitrate concentrations or drilling deeper to access groundwater with lower nitrate levels.

 

The third option involves treating water to remove nitrate using technologies like denitrification, ion exchange, and reverse osmosis, which are employed elsewhere but not yet adopted by Danish waterworks.