What if the chemicals sprayed on our food — at levels regulators insist are “safe” — were quietly fueling cancers we never saw coming?
That’s the unsettling question raised by a long-term animal study showing that glyphosate, the active ingredient in Roundup®, triggered multiple types of aggressive cancers even at doses far below what regulators around the world currently allow. Thyroid tumors, leukemia, nerve sheath cancers — the kinds of illnesses you don’t expect to trace back to a weedkiller.
Here in New Zealand, glyphosate isn’t just sprayed on weeds. It’s routinely used as a pre-harvest drying agent on crops like wheat and oats, meaning trace residues can end up in the food we eat every single day. Honey, cereals, bread — the very staples most of us rely on. And while the Ministry for Primary Industries has proposed raising the allowable limits of glyphosate in some foods, new science is telling us the opposite: even so-called “acceptable” levels may not be safe at all.
This article takes a closer look at what the research is really saying, how it connects to our own food system here in New Zealand, and why it’s time to question whether we can keep turning a blind eye to glyphosate’s hidden toll.
The Study Unpacked
On June 12, 2025, we published a hard-hitting overview of this study, capturing its disturbing breadth: glyphosate exposure from the womb through adulthood triggered at least 14 different tumor types in rats—even at doses regulators currently deem “safe.” These spanned leukemia, liver, thyroid, ovarian, testicular, bone, skin, adrenal, and brain tumors.
A Closer Look at the Study Design
What makes this study stand out is how closely it mimicked real life. Instead of giving rats one-off, high doses of glyphosate, researchers exposed them from the womb right through their entire lives. Mothers were dosed during pregnancy, and their offspring carried that exposure every single day — just as we do through our food, water, and environment.
The results were grim. Not only did the rats develop a wide variety of cancers, but many showed early onset tumours and even multiple cancers at once. That pattern points to a cumulative, aggressive effect rather than random chance.
Scientists also uncovered the “how.” Glyphosate didn’t just sit harmlessly in the body — it caused DNA damage, triggered oxidative stress, and disrupted hormones, particularly in systems sensitive to estrogen.
Perhaps most concerning of all, the commercial products — the Roundups and RangerPros of the world — proved even more toxic than glyphosate alone. Those so-called “inert” co-formulants turned out to amplify harm, confirming what critics have warned for years.
Independent reports back this up. Verywell Health, for instance, highlighted that rats exposed from conception to glyphosate-based products — even at doses regulators call “safe” — developed far more tumours and early leukemia than controls. Or, as they put it: “even so-called ‘safe’ levels may not be safe at all.”
Connecting the Dots: New Zealand Relevance
If glyphosate exposure is driving cancers in lab animals at so-called “safe” doses, what does that mean for us here in New Zealand?
The first point to recognise is that glyphosate isn’t just used on weeds in driveways and sports fields. In New Zealand, it’s also applied as a pre-harvest desiccant on staple crops like wheat, oats, and barley. That practice means residues end up in the human food chain. From cereals and breads to honey and baby foods, glyphosate contamination isn’t an outlier; it’s baked into the system.
Independent testing in New Zealand has already confirmed this. Our own results have found glyphosate residues in honey, Weet-Bix, popular breakfast cereals, and supermarket bread — the exact foods families consume daily. Levels may fall under the current legal thresholds, but this new study shows that “legal” and “safe” are not the same thing.
Meanwhile, regulators seem to be moving in the opposite direction. Instead of tightening controls in light of mounting scientific evidence, the Ministry for Primary Industries has proposed raising the maximum residue limits (MRLs) on key crops. That means glyphosate residues once considered too high for human consumption could soon be deemed acceptable on your dinner plate.
And here’s the contradiction: while Europe is actively debating stricter thresholds — with the European Food Safety Authority recommending an Acceptable Daily Intake (ADI) of 0.1 mg/kg/day — New Zealand continues to stick to a far looser 0.3 mg/kg/day, a limit largely inherited from outdated, industry-funded science.
The bottom line? If rats can develop multiple aggressive cancers at exposures within today’s legal limits, then our current system of “acceptable” residues is failing to protect public health. For a country that prides itself on clean, green food production, allowing higher glyphosate residues risks eroding not just public trust but also the credibility of our food exports.
Why the Findings Matter
The easy response from officials is always the same: “Don’t worry, the residues are well below the legal limit.” But this latest research flips that logic on its head. If animals are developing aggressive cancers at exposures that mirror current “safe” thresholds, then the threshold itself is the problem.
This isn’t just about glyphosate in isolation, either. We’re talking about daily, lifelong exposure. A few micrograms in your cereal here, a trace in your honey there, more in your bread, plus the spray drifting across playgrounds, parks, and roadsides. Each exposure might be small — but together they form a continuous, low-level chemical burden that your body never truly escapes.
That’s where the danger lies. The new study shows that chronic exposure doesn’t just nudge the body — it disrupts DNA, hormones, and immune function in ways that can accumulate over time. And when “inert” additives in Roundup® formulations make the whole cocktail even more toxic, the risks go beyond what glyphosate alone might explain.
For New Zealand, the implications are clear:
- Public health: We can’t assume current limits are protective if those limits were set using industry data from decades ago.
- Policy credibility: Proposals to raise residue limits look reckless when new science points the other way.
- Consumer trust: Every time glyphosate shows up in honey, cereals, or bread, confidence in our food system erodes a little more.
The message is simple: legal doesn’t always mean safe. And waiting for absolute proof in humans before acting means gambling with future generations’ health.
Taking Action: What New Zealand Can Do
So where does this leave us? If glyphosate at “legal” doses is linked to cancers in animals, and if residues are showing up in our everyday food supply, then the next step is clear: we can’t wait for regulators to catch up.
What individuals can do right now
- Choose organic where possible: Organic grains, oats, and flours are less likely to be contaminated, since pre-harvest glyphosate spraying is prohibited.
- Support local producers who test: Some Kiwi brands, like Comvita with honey, are already moving toward glyphosate testing and transparency. Choosing these products sends a message.
- Filter your water: Certain water filters can reduce glyphosate residues, cutting another pathway of exposure.
- Eat to detox: Foods rich in antioxidants and fibre — leafy greens, cruciferous veg, seaweed — help the body clear chemical burdens more effectively.
“We can’t wait for regulators to catch up.”
What communities can push for
- Independent testing: Continue supporting grassroots initiatives that test food and water for glyphosate residues. These results shine light on what regulators prefer to ignore.
- Glyphosate-free spaces: Schools, councils, sports clubs, and marae can all lead the way by banning Roundup® and choosing safer alternatives.
- Stronger policy: Demand that MPI and the EPA reassess glyphosate safety limits using independent science — not just industry data from the 1980s.
Why this matters beyond our borders
New Zealand markets itself as a “clean, green” producer. But if overseas markets begin rejecting glyphosate-contaminated products — as Japan already has with honey — we risk not only public health but also trade credibility.
“Clean, green isn’t a slogan — it’s a responsibility.”
This isn’t a hopeless fight. Every product you choose, every question you raise with a food producer, every submission to policymakers — it all chips away at the false assurance that glyphosate is harmless. When citizens act, regulators and corporations eventually have to follow.
Where We Go From Here
Glyphosate has long been sold to the public as a “safe” weedkiller — a miracle chemical that keeps farms productive and supermarket shelves full. But the evidence is piling up: when exposure is constant and lifelong, glyphosate is far from harmless. The latest study confirms what communities, scientists, and even courts have been warning for years — the dose we’ve been told is safe may, in fact, be the dose that does us harm.
Here in New Zealand, we face a choice. Do we accept higher residue limits, outdated safety claims, and a food system where chemical contamination is normalised? Or do we push back — demanding independent science, honest labelling, and a genuine commitment to protect public health over corporate profit?
Every jar of honey we test, every loaf of bread we check, every submission we make is a reminder that the public is watching. And the more we shine a light on glyphosate’s hidden presence, the harder it becomes for officials and industry to look the other way.
Now is the time to act — to support independent testing, to question the narratives, and to stand together for a food system that doesn’t gamble with our health. Because when it comes to glyphosate, silence isn’t safety — it’s surrender.
Resources & References
When regulators and industry assure us that glyphosate is “safe,” they’re often leaning on outdated or incomplete evidence. Independent studies, international rulings, and even our own testing in New Zealand paint a very different picture. Below you’ll find a collection of key resources — scientific research, regulatory documents, and media reports — so you can dig deeper and decide for yourself.
Key scientific evidence
Panzacchi et al., 2025 — Environmental Health (Global Glyphosate Study, carcinogenicity phase) — Lifelong exposure from prenatal life to glyphosate and GBHs increased multiple tumour types in rats; full methods and results.
https://ehjournal.biomedcentral.com/articles/10.1186/s12940-025-01187-2
George Mason University news (June 20, 2025) — Plain-language summary: low doses of glyphosate caused multiple cancer types in rats.
https://publichealth.gmu.edu/news/2025-06/international-study-reveals-glyphosate-weed-killers-cause-multiple-types-cancer
Hazard classification & major reviews (global)
IARC Monograph 112 (2015) — IARC classified glyphosate as “probably carcinogenic to humans” (Group 2A).
https://www.iarc.who.int/wp-content/uploads/2018/07/MonographVolume112-1.pdf
ECHA (EU) overview — RAC maintained no CLP carcinogen classification for glyphosate.
https://echa.europa.eu/hot-topics/glyphosate
EFSA peer-review conclusion (2023) — EU risk assessment conclusions and identified data gaps used for renewal.
https://www.efsa.europa.eu/en/efsajournal/pub/8164
European Commission status — Renewal and standing committee materials for the current EU approval.
https://food.ec.europa.eu/plants/pesticides/approval-active-substances/renewal-approval/glyphosate_en
New Zealand limits, ADI & official positions
FSANZ explainer — Consumer page; ADI for Australia/New Zealand and background on monitoring.
https://www.foodstandards.gov.au/consumer/chemicals/Glyphosate
MPI: Glyphosate in food (New Zealand Government) — New Zealand survey findings and official stance on residues (wheat, honey, etc.).
https://www.mpi.govt.nz/food-safety-home/safe-levels-of-chemicals-in-food/fertilisers-pesticides-hormones-and-medicines-in-food/glyphosate-in-food/
New Zealand residue rules & 2025 proposals
Food Notice: Maximum Residue Levels (MRLs) — (31 Jul 2025; in force 4 Aug 2025)
https://www.mpi.govt.nz/dmsdocument/19550-Food-Notice-Maximum-Residue-Levels-for-Agricultural-Compounds2025
MPI consultation (Feb–May 2025) — Proposed amendments to the MRL notice, including glyphosate.
https://www.mpi.govt.nz/consultations/proposals-to-amend-the-new-zealand-food-notice-maximum-residue-levels-for-agricultural-compounds/
Honey exports & international MRLs
RNZ (Jan 2021) — New Zealand required testing of honey exports to Japan after repeated glyphosate detections.
https://www.rnz.co.nz/news/political/434895/call-for-more-strict-glyphosate-use-guidelines-after-japan-s-honey-warning
AsureQuality advisory — Confirms MPI’s testing requirement for Japan-bound honey.
https://www.asurequality.com/industries/apiculture/glyphosate-testing-for-honey
Analytica Labs (testing guidance) — Overview of commonly applied honey MRLs by market.
https://www.analytica.co.nz/testing-services/honey/glyphosate/
Japan MHLW (Positive List) — Official page referencing the 0.01 ppm default MRL when no specific limit exists; includes an entry listing New Zealand honey – glyphosate with 0.01 ppm.
https://www.mhlw.go.jp/english/topics/importedfoods/20/appendix1.html
Pre-harvest (desiccation) & NewZealand practice notes
- FAR (Foundation for Arable Research) — Pre-harvest glyphosate use discussed; trials on timing/rate and residue implications in wheat, barley, oats.
https://assets.far.org.nz/blog/files/82823e14-24e5-4dc8-8593-796a306f4262.pdf
https://assets.far.org.nz/blog/files/a4d907a1-8b8b-58c3-b9f7-9f6aa9f14330.pdf
Formulations vs. active ingredient (why Roundup® can be worse than glyphosate alone)
Mesnage et al., 2015 (Food and Chemical Toxicology) — A thorough peer-reviewed review highlighting that glyphosate-based herbicide formulations can be toxic below regulatory limits, often due to the added adjuvants boosting glyphosate’s toxicity.
https://pubmed.ncbi.nlm.nih.gov/26282372/
Mesnage et al., 2019 (Toxicology, as summarized by PubMed) — Demonstrated that early-generation POEA surfactants (used in Roundup formulations) are significantly more toxic than glyphosate alone, raising serious concerns about regulatory tests that ignore these mixtures.
https://pubmed.ncbi.nlm.nih.gov/30951798/
Defarge et al., 2016 (MDPI, Int J Environ Res Public Health) — Showed that co-formulants and herbicide formulations, not the declared active ingredient glyphosate, caused hormone-disrupting effects in human cells at much lower concentrations than agricultural dilutions.
https://www.mdpi.com/1660-4601/13/3/264
Myers et al., 2016 (Environmental Health) — A consensus-type article summarizing that glyphosate-based product formulations are often far more toxic than glyphosate alone across multiple organisms—including mammals—and that regulatory assessments significantly underestimate real-world risks.
https://ehjournal.biomedcentral.com/articles/10.1186/s12940-016-0117-0
Related article on nomoreglyphosate.nz
The Cancer We Can’t Keep Ignoring — (June 12, 2025)
Our in-depth look at the groundbreaking Ramazzini study showing how long-term glyphosate exposure triggered multiple cancers in lab animals.
https://nomoreglyphosate.nz/glyphosate-evidence-impact/
Final Thought
Science should guide public health — not lag behind it. These resources show how the story of glyphosate is shifting worldwide: from “safe enough” to “too risky to ignore.” The question for New Zealand is whether we’ll learn from this evidence now, or wait until the damage is undeniable.
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