Academics call for urgent action on nitrate pollution

A trio of academics are calling on the Canterbury Regional Council (CRC) to take urgent action on what they deem a water pollution crisis.

They want the council to commission an independent analysis of how the nitrate levels in the region's drinking water have got so high, and a review by the auditor general of the council's conflict of interest policies.

As nitrate levels climb across the region, municipal water supplies have seen levels increase towards - and in some cases breach - the national drinking water standard of 11.3 milligrams of nitrate per litre of water.

From Waimate, in South Canterbury, which has seen one of its water schemes off limits for several periods over the past two years, to rapidly growing areas on the urban-rural fringe, such as Rolleston in the Selwyn District, and Oxford in Waimakariri, residents and district councils are grappling with increasing nitrate levels in private wells and council supplies alike.

Environment Canterbury's most recent groundwater survey report showed 59 percent of monitored sites had worsening levels of nitrate, and 10 percent had breached the drinking water standard.

The national standard of 11.3mg/L is based on the 1958 World Health Organization guidelines specifically for preventing infant death from methaemoglobinaemia or blue baby syndrome.

Emerging research has pointed to health risks at far lower levels such as a 47 percent increase in premature births at levels over 5mg/L.

In 2021, the College of Midwives advised members to tell women on private bores to get their water tested, and for pregnant and breastfeeding mothers to switch to bottled water if nitrate levels were over 5mg/L.

Another analysis of overseas research has found a potential link with bowel cancer at levels as low as 0.87mg/L.

Public health specialists University of Otago professor Simon Hales, research fellow Marnie Prickett and University of Canterbury associate professor Tim Chambers presented to the regional council on Wednesday - or to the nine of the 16 councillors that turned up - laying bare the extent of Canterbury's water woes, calling on the council to commission independent analysis of how levels kept rising despite its efforts, and requesting the auditor general conduct a conflict of interest review of the council's processes.

Prickett said she was disappointed there wasn't a better showing.

"Drinking water is so fundamental and foundational that all councillors should be valuing information about it.

"The issue itself is old news, but there's still a lot for our councillors to understand and unpack around the state of the environment, and the policies and plans. I would have liked to see a full house."

But CRC chair Craig Pauling said councillors were a "hardworking bunch", and he was not surprised by the turnout.

Pauling agreed the issue of nitrate contamination was "massive", "urgent", and "definitely a concern", and said it was one of the reasons he first stood to be a councillor back in 2016.

But he said changes made by the government to the Resource Management Act last year meant the council could not do freshwater planning at the moment, "even if it wanted to."

"It's definitely urgent - but planning does take time, and it costs a lot of money."

But Prickett and her colleagues said the situation was a crisis, and urged the council to stop framing the problem as a "legacy issue".

She told the meeting they were "troubled" by comments that groundwater lag times meant there wouldn't be improvements for twenty years, and asked the council to be "more accurate and more honest."

While some problems could be traced back decades, "what we put on the table showed there are issues coming about today because of decisions that were made two, three or four years ago."

"That's not what the average Cantabrian would think of as a legacy issue, that's a decision-making issue."

Prickett highlighted the precipitous increase in nitrate in the Lower Waihao scheme, which serves the small settlement of Glenavy in Waimate.

She said the data showed nitrate had been very low in the area for years, until 2015, when the council made a decision to allow irrigation to be changed from border dyke irrigation, where channels cut into the land allow water to run into the pasture, to spray (pivot) irrigators.

A council report at the time warned of the anticipated nitrate increase.

"Assessment results indicate that border dyke conversion could cause nitrate concentrations to exceed the MAV (maximum acceptable value) here," the report said, finding a jump from 33 percent of bores at risk of exceeding the limit, up to 59 percent.

Prickett said it underscored the importance of not pointing to "legacy issues" as a catch-all when the lag between the decision being taken and nitrate levels breaching drinking water standards was seven years, rather than decades.

Chambers is one of a number of voices - including environmental groups, Fish and Game, GNS Science, the Public Health Association and Canterbury's former medical office of health, Dr Alistair Humphrey - who has called on the government to lower the maximum allowable value of 11.3mg/L per litre of water.

In Wednesday's presentation, he pointed to France, Denmark and the United States, who are all conducting reviews of their nation's limits, citing the growing body of research on health impacts.

The trio also noted the council's own rules set far lower limits in some places.

Thanks to a recent change to the Canterbury Land & Water Regional Plan (Plan Change 7), there was a limit of 5.65mg/L for Waimakariri District Council municipal water supplies, which was also set as a median for private well water supplies. (The council maintains it is not responsible for private wells, though recently agreed to promote well owners getting their own testing done).

Council staff present were unclear on whether the levels were hard limits, and what action would be taken if they were breached.

The council's own, lower limit of 5.65mg/L also appeared to apply to a median from private water wells according to a table in Plan Change 7.

Regional council chair Craig Pauling said he was "not sure" whether the council had responsibility for water in private wells.

But he said the council had recently agreed to an "awareness raising campaign" to encourage those with private water wells to test their own water.

"We're definitely not committing to a private bore monitoring programme, but we are committing to an awareness-raising campaign, and we are going to do some testing in high-risk areas," Pauling said.

Chambers also urged the council to improve its data availability, collection and use.

He said if it had access to the raw data from farm plans, it would be able to see where nitrogen loads were coming from, which land uses were affecting water quality, and what the associated lag times actually were.

Councillor Deon Swiggs asked what influences other land uses, like potato growing, might be having on nitrate levels.

"I'm just really curious why you're picking on dairy specifically?"

Councillor Nick Ward also pointed to other possible contributors, again highlighting the impact of potato crops, which could also leech other contaminants such as phosphate.

Prickett agreed vegetable growing could be very high in nitrogen loss, but was generally occupied smaller areas than dairying.

She said there was research looking at the impact of different land uses to the total nutrient load, such as Maanaki Whenua Landcare Research work on the Waimakariri water zone.

The report breaks down the average nutrient loss from different activities - in the Waimakariri case, dairy and dairy support contributed over half (57 percent) the total load of nitrogen. The second major contributor was sheep, beef and deer, which contributed 33.6 percent, and horticulture contributed 0.36 percent of the total load.

Prickett said it was important to acknowledge the seriousness of the situation, and to stop deflecting with debates on blame.

"We've had a really immature conversation in New Zealand generally about the impact of our agricultural sector on our waterways. I often hear people say, we shouldn't blame - but actually this isn't about blame, this is about understanding an issue and getting on top of it.

"You can distract by saying this is about blame, but actually, if a sector is responsible for a pollution issue, then you have to understand that and put rules and policies in place to reduce that."

The council also heard about potential financial costs.

Councils do not treat for nitrates at present, and removal was a difficult and complicated process, Prickett said.

Estimates from the Waimate District Council were between $500,000 to $750,000 plus ongoing costs to treat one scheme that supplied just 600 people, while the Selwyn District Council estimated finding and establishing a new, lower nitrate water source could cost $400million, and work done for the Christchurch City Council put the price of denitrifying the city's drinking water at $830millon to $1.5billion.

The final recommendation made by the public health experts was for the regional council to request the auditor-general conduct a review of the council's conflict-of-interest processes.

Given the severe intergenerational consequences of contaminated drinking water sources, it was incumbent upon the council to conduct the review, Prickett said.

"It's not assuming there are any problems with conflict of interest, it's just acknowledging there's a high risk conflicts of interest could undermine responsible decision making on drinking water."

She said robust, "watertight" processes would give Cantabrians confidence any conflicts of interests were well managed.

Pauling said the council had not had time to discuss the other two recommendations, but he did rejected the call for the review.

He said the council already had processes in place, including a pecuniary interest register, which was updated every year.

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