The debate over what a prominent freshwater ecologist calls tricky statistics goes another round. David Williams reports
Environment Canterbury is ignoring its own data to cover-up nitrate pollution, freshwater ecologist Dr Mike Joy says. It’s a claim the regional council rejects.
Last Friday, ECan, as it’s known, released its annual groundwater quality survey, which showed that between 2011 and 2020, 47 percent of wells (118) had either likely increasing or very likely increasing nitrate-nitrogen concentrations.
This is important because high nitrate in groundwater can pose health risks to people drinking it. When it flows through to waterways and lakes it can kill fish, and cause excessive weed growth and algal blooms.
Areas near or downstream from intensive farms tend to have higher nitrate concentrations, the report says.
Joy, fresh from winning a battle with Stats NZ over what’s deemed a “natural” concentration of nitrate-nitrogen, says it’s harder to find trends when ECan restricts its survey to 10 years, and uses single, annual data points.
Some ECan well records stretch back to 1989 but the data are not used. In that way, Joy says, the “snapshot” survey uses “tricky stats”.
When he ran the numbers on ECan’s groundwater data two years ago, he found the trends for degraded wells were more pronounced than were being reported, at about two-thirds.
“They’re doing everything they can to gild the lily,” Joy says. “And if they were to stop that, and actually use the full-time record, and not try to do this ‘just 10 years’ bit, then they would actually get some truth around what’s happening.”
(The ECan report also notes its trends differ from those on the Land, Air, Water Aotearoa website because it uses different time periods and sampling frequencies. “It’s the same data,” Joy says with bewilderment. “LAWA isn’t a separate body that collects its own data, it’s a housing point for regional council data.”)
ECan’s science director Dr Tim Davie says the regional council provides a fair representation of groundwater quality in Canterbury. Its annual survey is a snapshot of groundwater quality each spring, when nitrate concentrations are generally at their highest.
The LAWA website contains all ECan’s data, including quarterly samples and trend analyses.
Davie says its reports and data demonstrate nitrate concentrations in groundwater across the region continue to increase, and a significant number of wells exceed current drinking-water standards. The result isn’t surprising, he says.
“A response of “not surprising” does not mean we are happy with the results. We are not, so we continue to push for greater reductions in nitrogen loss across Canterbury.”
ECan, which only returned to full democracy in 2019, nine years after its councillors were sacked and replaced with commissioners, has overseen a massive increase in farm intensification and an explosion in agriculture-related irrigation over the last 20 years or so.
The council’s role is to monitor and protect the quality of water in the region’s aquifers, rivers and lakes. Its website says: “We cannot knowingly let water quality decline.”
ECan’s response has been to introduce farm rules, which it says are some of the strictest in the country, and require farmers to have audited environment plans and adhere to industry-agreed management practices.
Yet improvements to groundwater quality aren’t expected for “at least another 15 to 20 years”.
Another front in the nitrate battle is over health effects.
A Danish study published in the International Journal of Cancer three years ago, which followed 2.7 million people over 23 years, found increased risk of colorectal cancer for those exposed to high nitrate concentrations.
New Zealand has one of the highest rates of bowel cancer in the world.
Environmental groups in this country are using the Danish study to call for a 1 milligram per litre limit for nitrate in waterways. (The study, which suggests a threshold of 0.87mg/L for nitrate nitrogen, found a statistically significant increased risk above 3.87mg/L.)
The World Health Organisation (WHO) drinking water standard is 11.3mg/L, adopted as this country’s maximum acceptable value, after which bottle-fed babies are at an increased risk of blue baby syndrome.
Yesterday, Greenpeace called on ECan to be “upfront with communities about the chronic health risks of nitrate contamination in drinking water”. The regional council’s messages on health risks are too oblique and insufficient, senior campaigner Steve Abel says.
Greenpeace has recently run nitrate testing in various parts of rural Canterbury, at which 450 samples have been tested, and in Southland. Abel, who has attended the testing, says people shouldn’t be left wondering.
“People trust the health limit is 11.3mg/L, that if they’re under that limit then, so far as the official word is, they’re avoiding health risk. The emerging science tells us something very different to that.”
ECan says it contacted the owners of all wells with concentrations over 11.3mg/L. (The highest recorded concentration was 22mg/L.) Most are not used for drinking water, groundwater science manager Carl Hanson said last week. Some owners have installed filters, others have replace their wells.
Interestingly, when Environment Southland identifies a well above 4mg/L of nitrate-nitrogen it warns the owner that concentration is “significantly elevated”, and “this should be of consideration to those consuming this water”.
Abel tells the story of one man who spent $10,000 drilling a deeper well, only to find his nitrate concentration had reduced from 12mg/L to 10mg/L. That, the man said, was a kick in the teeth.
“The authorities need to stop worrying about covering their arses and think about their first obligation,” Abel says, “which is to make sure that the public are properly informed and advised of the potential health risks.”
He adds: “They need to face up to the fact that what we’ve done with 30 years of a near seven-fold increase in synthetic nitrogen fertiliser use and a doubling of the dairy herd, is we are in the process of turning people’s drinking water carcinogenic.”
ECan’s groundwater survey mentions the WHO limit but doesn’t explicitly mention the latest health risks. Davie, ECan’s science director, says its reports allow “easy comparison” to thresholds suggested by recent studies into the health effects of nitrate in drinking water.
The council’s website does mention the Danish study. Another recent study mentioned, from California, suggests a link between nitrate contamination and premature births.
Davie says ECan supports calls for further research into drinking-water guidelines. But, he notes, it’s the Ministry of Health that sets drinking-water standards and provides public statements on health risks.
Questions have been raised about the Ministry’s interest in researching this area. RNZ reported in March a working group – chaired by Ian Town, the Health Ministry’s chief science adviser – set up to consider nitrate in water, met twice in 18 months and was disbanded.
In the story, Associate Health Minister Ayesha Verrall said she’d asked for a final report on the working group’s findings. Newsroom asked Verrall’s office for a copy of the report on July 7, but on Tuesday, some 20 days later, was told it had drawn a blank. In comment provided on Thursday morning, Health Ministry director of public health Caroline McElnay said a report was provided in April.
Abel’s attack on ECan doesn’t stop at public health warnings. He says the regional council is complicit – a core player – in contaminating people’s drinking water through permitting extensive synthetic fertiliser use and dairy intensification.
“ECan don’t want to concede that there’s a major problem here because they are actually a facilitator of that problem – they’re the same regulator that issued the consents for the pollution to happen in the first place.”
Davie rejects that claim. But his response seems slightly contradictory.
On one hand he says ECan recognised “many years ago” there were significant environmental and human health risks posed by elevated nitrate concentrations. (Joy has written the Ministry of Works predicted nitrate contamination from regional irrigation schemes in 1986.)
Yet Davie describes it as a legacy issue – one recognised “many years ago”, remember – “which has taken generations to manifest itself fully and will take decades to fix”.
For years, Greenpeace has been pointing the finger at intensive dairy farms and fertiliser companies as being largely to blame for water pollution, as well as their respective contributions to greenhouse gas emissions and, with groundwater contamination, potential human health effects.
The environmental group is calling for a ban on synthetic nitrogen fertiliser. “We need to stop the problem at source and farm in a way that doesn’t poison our drinking water,” Abel says. “That’s do-able; there are many farmers who are doing that.”
Mike Manning, the general manager of innovation and strategy for fertiliser cooperative Ravensdown, says banning nitrogen fertiliser would leave a $7 billion hole and cost 70,000 jobs.
Before the Government imposed a 190kg per hectare limit on fertiliser use, the company, which has a team of environmental consultants, was already helping farmers adjust and minimise nutrient losses, he says. It has spent millions of dollars researching soil testing, to avoid over-application, and developing heat maps to assure compliance.
“Nitrogen is simply a tool which farmers can use wisely or unwisely,” Manning says.
“We are not here to tell our customer-owners what to do, which farm system to pursue, how to put their land to use. We strive to provide them the right amount, not the most.”
The predominant cause of nitrate leaching is livestock effluent, he says – or more specifically from urine.
DairyNZ’s strategy and investment leader for responsible dairy, Dr David Burger, a water quality scientist, says farmers are committed to reducing their environmental footprint through measures like farm environmental plans, good environmental practice, and reducing inputs.
He points to the Mayfield-Hinds area, Mid Canterbury, in which a controversial discharge consent was recently renewed, as a place where farmers have reduced their nitrogen footprint “by 30 percent over the last few years”. “That’s huge,” Burger says.
(Actually, modelled nutrient load reductions by Mayfield-Hinds farmers using water from the MHV Ltd irrigation scheme are more like 10-to-15 percent, experts suggest. And compared to a baseline of 2009-2013, the nitrogen flowing into the soil is estimated to have increased 40 percent.)
“We realise the job’s not done,” says Burger, who represents an industry that earned $20 billion in exports last year. “We realise that we’ve still got high nitrogen in some catchments compared to the current standards, particularly the current standard for ecosystem health that was introduced last year, and we’re committed to continuing that journey.”
Burger is keen to talk up the positives from ECan’s groundwater survey.
Across the region, the median nitrate concentration dropped from 3.4mg/L to 2.7mg/L. And the number of sites exceeding the 11.3mg/L WHO standard dropped from 30 to 20.
“That’s really good news,” Burger says, while noting sites with high nitrate concentrations will get worse before they get better.
A lot of sites are stabilising or going down, he says – 53 percent, according to the report. At the moment, 94 percent of sites are within WHO standard.
“When you have too much nitrate it gets metabolised into things that cause damage to the body.” Tim Chambers
Burger addresses the elephant in the room: “We believe the science on increased health risks in drinking water is still not clear.”
(Manning, of Ravensdown, is more combative, saying the Health Ministry and WHO are the proper authorities and the topic shouldn’t be informed by “the fear mongering or farmer-bashing perspective from those with an anti-dairy agenda”.)
It’s important not to over-interpret the impacts of nitrate on human health, Burger says. Greenpeace refers to the Danish study but, he says, subsequent studies have found the opposite or no relationship.
Burger points to a “meta-analysis” of studies, undertaken by Iranian researchers and published late last year. “Our understanding is that study found no association at all.”
Indeed, the paper, published in the journal Clinical Nutrition, which reviewed 15 studies, including the Danish one, says “nitrate in water did not show an association with risk of colorectal cancer”. However, in a section about its weaknesses, the paper mentions a possible lack of controls for dietary intake, which can affect association with colorectal cancer.
“We’re not medical health experts,” Burger says. “But from where we are sitting there is still a bit of uncertainty around the science, on that human health aspect.”
(DairyNZ and Ravensdown also sent a link to this Stuff story, in which Bowel Cancer NZ medical adviser Professor Frank Frizelle warns against over-interpreting the 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”.)
Dr Tim Chambers, a senior research fellow in University of Otago, Wellington’s, Health, Environment and Infection Research Unit, was a lead author of a preliminary study which found up to 800,000 New Zealanders were exposed to potentially harmful nitrate concentrations in drinking water. He says the Clinical Nutrition meta-analysis paper is “factually wrong and methodologically flawed”.
Studies have shown the association between nitrate and colorectal cancer, Chambers says, as well as pre-term births and low birth weights. “When you have too much nitrate it gets metabolised into things that cause damage to the body.”
A complicating factor, he says, is there are many things that can help reduce nitrate’s negative impact on the body, like fruit and vegetable consumption, and vitamin C and anti-oxidants. Whereas higher consumption of red meat and processed meat can accelerate harm.
“That’s a lot of the reason we see some variation in the studies,” he says. “My comment on state of the epidemiological evidence is that the study that is the most robust, the largest one, and the ones that account for these complexities – vitamin C and other dietary impacts – actually show the strongest association [with colorectal cancer].”
Is Greenpeace fearmongering? No, Chambers says. “There’s science to support what they’re saying.”
What next? A hugely influential factor is whether WHO will re-consider its drinking water standards. Our Health Ministry has a big role to play, too, in terms of research funding.
(Chambers isn’t aware of any current New Zealand studies into the issue.)
Abel, of Greenpeace, says many farmers are already facing reality and changing their operations – or as he puts it, becoming part of the solution. However, he believes the dairy industry is dragging its hooves. To illustrate the scale of the challenge, Abel draws a climate change comparison.
“If we expect Australia to take on the coal industry, and we expect Canada to take on the tar sands industry – which are huge, multi-billion-dollar industries – then we need to be, as a nation, prepared to take on the dairy industry, and recognise the part that it plays in impacting our environment, and now impacting human health.”
* This story has been updated with comment from Health Ministry director of public health Caroline McElnay.
