Link: https://www.rnz.co.nz/news/national/589304/greenpeace-calls-for-government-to-drastically-cut-legal-limit-of-nitrates-in-drinking-water

I think this is not directly politics but rather a discussion on nitrates so have posted here.

A selection of key quotes from the article:

Greenpeace is calling on the government to drastically cut the legal limit of nitrates in drinking water as the Danish government moves to drop its legal limit by almost 90 percent.

The Danish government plans to lower its limit to just over one milligram of nitrate-nitrogen per litre (mg/L) of drinking water, a steep drop from its current limit of 11.3mg/L.

New Zealand's current legal limit for nitrates in drinking water is 11.3 mg/L, but there was growing evidence of health impacts at levels as low as 1mg/L.

"The Danish government aren't operating off a secret playbook or anything, they don't know anything we don't know. They're just following the scientific evidence and choosing to prioritise people's health. Meanwhile, our government is burying its head in the sand," Appelbe said.

The panel's report quoted 2023 University of Copenhagen research, which found lowering nitrate contamination would save 2.2 billion Kroner ($580m NZD) by preventing approximately 127 cases of bowel cancer per year linked to the current nitrate levels.

Appelbe said the government was more concerned with protecting dairy industry profits than human health and he called for reductions in the size of the dairy herd, an end to ongoing dairy expansions and limits to the use of nitrate fertiliser.

Rural communities were disproportionately affected and faced considerable costs installing filters to make their water drinkable, he said.

"We need, as a country, to have a grown-up conversation about nitrate contamination in drinking water - the evidence is pretty overwhelming on what's causing it and there's a growing body of evidence that links risks to human health."

Appelbe said the current limit of 11.3mg/L is based on World Health Organisation guidance from the 1960s to avoid Blue Baby Syndrome, an acute illness that could affect babies.

A 2025 GNS Science research paper estimated there could be more than 21,200 people drinking water above the legal limit of 11.3 mg/L and 101,000 people drinking water above half that (5.65mg/L) across rural New Zealand.

The authors found Waikato, Canterbury and Southland were disproportionately affected by elevated levels of nitrate

Public health specialists had long advocated to lower the nitrate limit, primarily based on international research linking low levels of nitrate (5mg/L) with pre-term birth and colorectal cancer (0.87mg/L).

New research from Australia's Edith Cowan University and the Danish Cancer Research Institute found a link to early-onset dementia as low as 1.2mg/L with nitrates from processed meat and drinking water posing a higher risk, while nitrates from vegetables were associated with a lower risk.

Canterbury's dairy herd has increased by about 1000 percent since 1990 to well over a million cows.

Between 1990 and 2022, Southland's dairy herd increased by 1668 percent from 38,000 to 668,000 cows.

N.B. A normal water filter doesn't remove nitrates. You need ion exchange or reverse osmosis which aren't the standard charcoal filters used to make drinking water taste better.

as an aside, in fish-keeping you aim to keep nitrates below 5ppm, and in many cases below 1ppm.

The drinking water limits are there for 2 to 10 x what most people would keep fish in

Oh good context. The article mentions farmers facing considerable costs installing water filters, but it doesn't specify why the costs are high.

Do you know if anything is done in town supply water to remove nitrates, or do they just aim to use water sources that are less affected? The article mentions farmers and rural areas being the ones affected by this so my assumption is urban areas don't really have this problem.

I'm going to assume that the minister for drinking water is going to try and double the limit.

Do you know if anything is done in town supply water to remove nitrates, or do they just aim to use water sources that are less affected?

We would need some transparency on which "suppliers" have had high readings. One would think that data would be readily available given that the suppliers are supposed to collect the data and report it. All I can find are aggregate data reports, at least from Taumata Arowai.

Here is the part of the Water Services Act 2021 where it says:

A drinking water supplier must report the results of the supplier’s source water quality monitoring to the Water Services Authority, and the Water Services Authority must provide regional councils with monitoring results annually.

Having the producers check their own work can create measurement bias. Yeah, the testing happens via accredited labs but think of the case where a single unelected person can decide to time collections around weather events to obtain more desirable results.

The long and boring "Factsheet: Drinking Water Regulation Report 2024 and Network Environmental Performance Report 2023/24" points our that:

Nitrate is an emerging risk in some parts of New Zealand.

I can't find any consistent raw measurement data on Taumata Arowai's web site. It looks like the 2023 data had median nitrate concentrations per supply (seems to be median for the year) but they've further aggregated / obfuscated that in the 2024 data.

My guess is that the data is a mess with a bunch of missing measurements and they are embarrassed to make it public. It doesn't seem like a scandal so much as just slow uptake. Their most recent annual report boasts increases in reporting compliance.

AFAICT, an OIA would be required to get a jumble of messy data; and then, likely, a weekend to make sense of it all. You might be able to see some outliers pretty quickly though.

If your water comes from a lake / river, or is pumped up from a valley with upstream agriculture, then you probably want to check the measurement data. For my town, there's a catchment up in the hills that feeds the towns water supply. Less than 100km away, they are pumping ground water out of a bore at the base of a valley with a high level of agriculture. Even the old measurements from the Greenpeace Map show the difference in testing levels between those two setups. The catchment in the hills has low / barely any; while the valley shows elevated levels. That jives with the explanation from LAWA on "How does nitrate enter groundwater?".

Like when MBIE tested for herbicide / pesticide residuals in food, and then it came back too high, and then ten years went by where they didn't publish any new testing numbers, and then they tried to increase the limit of some by 100-fold, and then thousands of people submitted on it?

Thanks, heaps of cool info. That Greenpeace map shows that even town supply water can vary a lot. Most of the larger North Island places have hardly any nitrates. I was surprised to see Taranaki and the Waikato having largely ok results, with their concentration of dairy farming.

Holy hell that rural Christchurch/Ashburton area though, with many way outside the current limits, and almost all of the area above what should probably be the limit!

Yes. Exactly.

But, does everyone just ignore the impact on share holders? What about their dividends? If we have to spend money to avoid polluting where does it come from? The back pocket of Mom and Pop investors expecting that dividend? How are you...

Sorry. Can't keep it up.