Is It Time for a Class Action on Nitrates?

Across Canterbury, and in other intensive-farming regions, people have been quietly drinking water with elevated nitrate levels for decades. Now the science is catching up – and it makes for grim reading.

International studies show that long-term exposure to nitrates in drinking water is associated with a significantly higher risk of colorectal (bowel) cancer, even at levels well below New Zealand’s current Maximum Acceptable Value. Canterbury has both some of the highest nitrate readings in the country and some of the highest bowel-cancer rates in the world.

So the uncomfortable question is starting to surface:

Is it time for a class action on nitrates?

Even if the law and the science aren’t quite “there” yet, the very fact that we’re asking this question tells us something about how badly our institutions have failed to protect both people and waterways.

This article doesn’t offer legal advice. Instead, it sets out what a nitrate-health case might look like, what tools exist in New Zealand law, and the hard realities any group of plaintiffs would face.

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What’s the problem?

For years, farming intensification and irrigation schemes have driven huge increases in nitrogen loading across Canterbury’s aquifers. Nitrate-nitrogen levels above half the drinking-water limit are now common in many bores; some supplies have exceeded the official MAV.

At the same time, international research is increasingly clear:

• long-term exposure to nitrates in drinking water is linked to a higher risk of colorectal cancer;
• the increased risk appears at concentrations far lower than New Zealand’s current standard;
• those on small rural supplies, private bores and unfiltered groundwater are most exposed.

Put bluntly: a significant number of people may have developed bowel cancer, at least in part, because authorities allowed and enabled high nitrate levels in their drinking water – and then did little or nothing to warn them.

For organisations like NZFFA and CORANZ, who have watched rivers, springs and aquifers steadily loaded with nitrogen, this is not just an environmental issue. It is a human-health and justice issue.

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Does New Zealand even have “class actions”?

New Zealand doesn’t yet have a specific Class Actions Act, the way the US or Australia do. But our courts do allow what are called representative proceedings.

Under the High Court Rules, one person can sue “on behalf of, or for the benefit of, all persons with the same interest” in the subject of a proceeding. In 2020 the Supreme Court confirmed that these cases can run on an opt-out basis – meaning everyone who fits the definition is included unless they actively opt out.

So while the machinery is clunkier than in other countries, we effectively do have a mechanism for class-action-style cases. The Law Commission has recommended a proper Class Actions Act; Parliament has yet to act.

In other words, if nitrate victims in Canterbury wanted to pursue a case together, the door isn’t closed.

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Who might be in the firing line?

Any serious lawsuit would have to decide who, exactly, is alleged to be at fault. Potential targets could include:

• The Crown – for nationwide standards, health advice and failure to respond to mounting evidence.
• Regional and district councils – for consenting intensive land use, failing to protect groundwater, and not acting when bores began to show high nitrate levels.
• Water suppliers – councils or schemes that knew, or ought to have known, that their source water was contaminated.
• Possibly, in some scenarios, large corporate land-users whose discharges largely caused the contamination.

That’s a formidable list. And every one of them will have teams of lawyers ready to argue they did everything required of them at the time.

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What would nitrate victims have to prove?

In very simple terms, a claimant group would need to show four things:

1. Duty of care
   That the Crown, councils and/or water suppliers had a legal obligation to take reasonable care to provide safe drinking water and to protect people from known or reasonably foreseeable harms.
2. Breach of that duty
   That those bodies failed to take reasonable steps – for example by:
   • allowing nitrate levels in groundwater to escalate unchecked,
   • setting or retaining a drinking-water limit that was not protective in light of emerging evidence,
   • failing to warn residents of potential risk or offer alternatives where bores were known to be high in nitrates.
3. Causation
   That this failure materially contributed to the bowel cancers suffered by the group. Not necessarily as the only cause, but as a substantial contributing factor.
4. Loss and damage
   The very real harm of bowel cancer: treatment, long-term health impacts, lost income, and in many cases the grief of families who have lost loved ones.

Law students learn that the hardest problem in toxic-exposure cases is always causation – especially when the disease has multiple risks (diet, genetics, lifestyle) and the exposure history is patchy.

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The science: friend or foe?

For a class action to work, plaintiffs would need strong, credible expert evidence. The good news is that the international epidemiology has moved a long way in recent years:

• Several large cohort studies overseas have demonstrated an increased risk of colorectal cancer even at nitrate levels lower than New Zealand’s current standard.
• New Zealand data shows that regions with higher nitrate in groundwater – particularly parts of Canterbury – align uncomfortably with elevated bowel cancer incidence.
• Overseas public-health bodies and researchers are increasingly questioning whether existing drinking-water limits are protective.

However, the defence would not be short of experts either. They’d argue that:

• The science is not yet “settled” enough to prove causation for individual patients on the balance of probabilities.
• At all relevant times, New Zealand regulators followed World Health Organisation guidance and existing limits.
• Other factors (diet, alcohol, smoking, genetics, screening access) could equally explain local bowel-cancer rates.

We have seen this pattern before: the science becomes clear long before courts and regulators are willing to say the words “causes X disease”. It took decades for smoking and lung-cancer cases to gain traction.

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Practical realities: it would be a very hard road

Even if a nitrate-bowel cancer class action is legally possible, several realities need to be front and centre:

Cost and complexity

Representative proceedings against the Crown and councils are not cheap. Claimants would almost certainly need:

• a specialist litigation team,
• international-level epidemiologists, hydrologists and medical experts,
• detailed reconstruction of historical nitrate levels in particular bores,
• careful case-selection (e.g. starting with a small number of very strong “test” cases).

That likely means either litigation funding or some form of pro-bono/public-interest support.

Time

Such a case could run for years, with appeals. Many of the people most affected are already unwell or elderly. Justice delayed risks becoming justice denied.

Uncertain outcome

Even with good science, courts can be conservative about imposing liability on public bodies for large, systemic harms – especially where decisions were made under earlier, looser standards.

There is a real risk that a case could fail not because the harm isn’t real, but because the legal thresholds for causation and breach are simply too demanding.

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So why talk about a class action at all?

If the road is so hard, why raise the idea?

Because sometimes the mere possibility of litigation is enough to change the political weather.

As with asbestos, contaminated blood, or smoking, the point where people start asking “could we sue?” is often the point at which governments realise the cost of inaction is no longer just moral or environmental – it may become financial and legal as well.

For NZFFA and CORANZ readers, the “class action” question is really a way of asking:

• How serious are we, as a country, about the link between land-use decisions, polluted water and human health?
• How long will authorities hide behind outdated standards and claimed uncertainty?
• At what point does persistent inaction become not just poor policy, but a breach of duty to the public?

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What could happen before the courtroom?

Whether or not a lawsuit ever gets off the ground, there are clear, concrete steps that affected communities, health advocates and environmental groups can push for right now:

1. A formal public inquiry
   into nitrates in drinking water and bowel cancer risk – with powers to compel evidence and make strong recommendations.
2. Lower, precautionary nitrate limits
   bringing New Zealand into line with the emerging science, rather than clinging to a limit set decades ago.
3. Comprehensive monitoring and public mapping
   of nitrate levels in all drinking-water sources, including private bores, with plain-language health information attached.
4. Support for affected communities
   including funded bowel-cancer screening programmes for residents in high-nitrate areas, and assistance to switch to safer supplies.
5. Serious nitrogen reduction targets
   in regional plans, coupled with land-use changes, to protect groundwater and surface water for future generations.
6. Legal reform
   passing a proper Class Actions Act and strengthening duties on those who supply drinking water, so that when things do go wrong, ordinary people are not left with all the risk and none of the remedy.

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A matter of justice, not just law

At the heart of this issue is a simple ethical question:

If it turns out that people in Canterbury and elsewhere have developed bowel cancer partly because their drinking water was loaded with nitrates, and authorities chose not to act on mounting evidence – who should bear that cost?

The individual patient, quietly, alone?
Or the system that allowed contamination to build while looking the other way?

A class action, if it ever comes, would be one way of forcing that question into a courtroom. But even before we get there, the possibility should focus minds.

For NZFFA, CORANZ and all who care about rivers, aquifers and rural communities, the message is clear:

• Nitrates are not just an abstract water-quality number; they are a potential driver of deadly disease.
• Our current standards and oversight may not be protecting people or waterways adequately.
• And unless we change course, the question “Is it time for a class action on nitrates?” will only get louder.

Whether through law, politics or public pressure, it is past time for those responsible to confront the consequences of decades of nitrate pollution – and to put the health of people and waterways ahead of short-term intensification.