Restating incorrect information over and over doesn’t make it true, regardless of how passionate the people giving the misinformation might be.
The expert in this subject is Frank Frizelle, Professor of Colorectal Surgery at the University of Otago, Canterbury, and advisor to Bowel Cancer NZ.
Professor Frizelle has stated publicly that “nitrates in drinking water are highly unlikely to increase the risk of bowel cancer in New Zealand, according to the current weight of evidence”.
Bowel Cancer NZ’s website carries a similar message, explaining that approximately half of the nitrates in our bodies come from metabolising amino acids; the other half comes from our diet, particularly green vegetables.
Less than 10% of nitrates in New Zealand come from drinking water.
Claims that people are at risk of colorectal cancer in New Zealand because of high nitrate rely on a study of citizens in Denmark published in 2018.
That study investigated the link between nitrates and colorectal cancer in Denmark over 23 years and could not determine causation. The results did not show a dose-related response. In other words, more nitrates didn’t result in more cancer.
The World Health Organisation (WHO) is alert for ‘emerging research’ on this matter, but it hasn’t changed its recommendations for safe drinking water concentrations of nitrate based on any study in recent years.
Their 2022 update on drinking water states: “Nitrate can reach both surface water and groundwater as a consequence of agricultural activity (including excess application of inorganic nitrogenous fertilisers and manures), from wastewater disposal and from oxidation of nitrogenous waste products in human and other animal excreta, including septic tanks.
“Nitrate can also occasionally reach groundwater as a consequence of natural vegetation,” the update says.
From this, it is clear that agriculture is not the only source of nitrate in drinking water.
The WHO report also makes it clear that babies are at risk from nitrate-related problems (such as Blue Baby Syndrome) when there is microbial contamination as well as high nitrate.
The 2022 report emphasises the importance of ensuring septic tanks are not sited near a well.
Another health concern incorrectly associated with nitrate in drinking water is preterm birth.
In New Zealand, approximately 7.4% of births are defined as preterm (less than 37 weeks of gestation), in comparison with 6.2% in Denmark, 8% in the UK, 8.7% in Australia and 10.5% in the USA.
The 2024 ‘New Zealand Maternity Clinical Indicators: background document’ recommends managing high blood pressure and tobacco to reduce likelihood of pre-term babies. Nitrate was not mentioned.
Further, in New Zealand, there is no relationship between higher-nitrate groundwater and wells and increased incidence of preterm births. Whatever region is examined, very few wells are over the World Health Guideline for nitrate in drinking water (50 mg/l) and few are above half the guideline recommendation.
All of the above information is in the public domain, but alarmist headlines still appear.
Farming leaders such as Wayne Langford have tried to point out the misinformation.
“Farmers and others in rural communities are drinking this water, so if there is a link then we want to know about it. But we will be taking our advice from health professionals, not environmental activists,” Langford has said.
He went on to say, “Greenpeace is using misinformation about a human health issue to prey on people’s fear of cancer and to push an anti-farming agenda”.
Professor Frizelle has also warned against over-interpreting the nitrate and bowel cancer research, “particularly in the environment we are in where we have a big anti-dairy lobby and water purity lobby who want to throw everything they can on the fire to say it is causing all this damage”.
But activists have cloth ears when correct information doesn’t suit their narrative.
In the nitrate case, the agenda appears to be pushing farmers to change from conventional agriculture to regenerative and organic farming or converting entirely to plant-based agriculture instead of animals.
Those wanting to see this happen believe it would be a win from all angles. However, they overlook the fact there would be a drastic fall in the production of high-quality protein for humans.
Fewer people would be fed, so it wouldn’t be a win for those who have no food.
The protein produced would have more environmental impact per kg of product; hence, no win for the environment.
And thirdly, New Zealand income would be reduced, which would leave the country with a balance-of-payment problem.
Cutting through the passion and misinformation is not always easy, but Mr Langford has the answer: get your advice from experts because they are both passionate and informed.
Dr Jacqueline Rowarth, Adjunct Professor Lincoln University, has a PhD in Soil Science, and is a director of DairyNZ, Ravensdown and Deer Industry NZ. She is also a member of the Scientific Council of the World Farmers’ Organisation.
Federated Farmers, New Zealand’s leading independent rural advocacy organisation, has established a news and insights partnership with AgriHQ, the country’s leading rural publisher, to give the farmers of New Zealand a more informed, united and stronger voice. Federated Farmers news and commentary appears each week in its own section of the Farmers Weekly print edition and online.
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