About 31 percent of samples had nitrate levels above half of the legal limit, and 5 percent were over the limit. Photo: 123rtf.com
Aotearoa's largest study into nitrates in drinking water signals a widespread threat to freshwater quality in rural areas.
The new study, led by Earth Sciences New Zealand, analysed more than 2,400 rural drinking water samples around the country between 2022 and 2024.
New Zealand has a maximum acceptable value for nitrate in drinking water of 50mg/L.
About 31 percent of samples had nitrate levels above half of the legal limit, and 5 percent were over the limit.
Canterbury, Waikato and Southland had the highest amounts of contamination and seven other regions were identified as having "emerging" nitrate issues.
Earth Sciences New Zealand said the data would help government, iwi, farmers and rural communities monitor water, reduce risks, and support households.
Multiple academic studies had linked high nitrate in drinking water to fatal blue baby syndrome, cancer and pregnancy risks.
The study confirmed Canterbury had the largest percentage of elevated groundwater nitrates in New Zealand.
It comes as a group of public health experts call for an independent review of Canterbury Regional Council's plans to address drinking water pollution.
Environment Canterbury, or Ecan, declared a "nitrate emergency" earlier this month, with councillors voting 9 to 7 in favour of the declaration.
An Ecan spokesperson said the organisation would now start working on points laid out in the Notice of Motion brought forward by departing councillor Vicky Southward.
But an article penned by Otago University academics Tim Chambers, Marnie Prickett and Simon Hales for the Public Health Communication Centre said the steps were not strong enough.
The group are calling for a number of independent reviews to make sure Ecan's plans to address the issue are sufficient.
University of Otago research fellow Marnie Prickett. Photo: RNZ / Nate McKinnon
Marnie Prickett said while declaring the emergency was a good step, stronger ones needed to be in place.
"And the question that needs to be answered is, are our rules and our current plans sufficient to protect our region's groundwater? And if they can't, why can't they do that?
"And if we don't understand that fundamental question, it's going to be really hard to address this problem, and I don't think that the council or councillors have a clear understanding of that yet.
"I think there's still an assumption within council and within council staff that the rules and the plans in place currently are sufficient, and we're pretty confident that they're not."
Prickett believed an audit of ECan's data and a review of its conflict of interest processes was needed as, she said, both were undermining decision making.
Next term, councillors will hold a workshop on the scale of the issue, causes and impacts of nitrate pollution in Canterbury.
Following advice they would also consider options to reallocate costs of nitrate removal from drinking water, which could involve passing the cost on to contributors of pollution.
Prickett said they presented their advice to Council in March and were shocked to see it had not been taken on board.
Ecan acting director of operations Dr Tim Davie. Photo: RNZ / Nate McKinnon
However, Ecan acting director of operations, Dr Tim Davie said they welcomed the recommendations, but it was up to the councillor who put the motion forward to decide what was included.
Dr Davies said the council was always working to get a clearer picture of water quality and ensuring they had the right data.
"An important part of our role in protecting freshwater is monitoring the state and trend of water quality.
"The size of Canterbury and the complexity of how groundwater and surface water sources interact means we are always working to get a clearer picture of water quality, while remaining cost effective for our rate payers.
"We work hard to ensure we are collecting the right data so that all resource users make informed decisions."
He also stressed that robust conflict-of-interest rules were in place for councillors and staff.
"Conflicts of interest are something we have a duty to take seriously."
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