Originally published May 16, 2025. Updated February 2026 to reflect new research, expanded regulatory context, and revised analysis.
Glyphosate is often described as one of the most studied herbicides in the world. It is also one of the most controversial.
For decades, products like Roundup® have been used across farms, orchards, public parks, and roadside verges. In New Zealand, glyphosate-based weedkillers remain central to conventional agriculture and infrastructure maintenance.
But while regulators maintain that current exposure levels are safe, the scientific debate has not settled as neatly as the public messaging suggests.
The question is not whether glyphosate kills weeds.
The question is whether long-term, low-dose exposure — especially through food and environmental drift — has health implications we are not fully accounting for.
Glyphosate and Fertility Concerns: What Does the Research Say?
In recent years, international discussion has shifted toward reproductive and endocrine effects. Several laboratory and animal studies have examined glyphosate’s potential impact on:
- Hormonal signaling
- Sperm quality
- Ovarian function
- Placental cells
- Developmental outcomes
Some findings suggest possible endocrine-disrupting properties — meaning glyphosate may interfere with hormonal communication in the body. That matters because hormones operate at extremely low concentrations. Small disruptions can have amplified biological effects.
This is explored in more depth in our article on Is Glyphosate an Endocrine Disruptor?
This is not the same as proving widespread human infertility.
But it does raise a reasonable question: are our regulatory frameworks designed to detect subtle hormonal effects, or are they primarily built around acute toxicity and high-dose testing?
That distinction matters.
IARC’s “Probably Carcinogenic” Classification Explained
In 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans” (Group 2A) after reviewing published evidence. A Working Group of 17 experts from 11 countries met in March 2015 to evaluate glyphosate alongside other organophosphate compounds.
Other regulatory bodies, including the US EPA and European agencies, have reached different conclusions regarding cancer risk at permitted exposure levels.
That divergence is often framed as proof that the science is “settled.”
It isn’t.
It demonstrates that risk assessment depends heavily on methodology, weight-of-evidence approaches, and interpretation thresholds.
New Zealand’s regulatory response to international classifications was examined in detail in our Browning–Brunning Review series.
And that is where the debate becomes technical — and uncomfortable.
Glyphosate Residue Limits in New Zealand (MRLs) — What Changed?
In May 2025, the Ministry for Primary Industries (MPI) proposed increasing Maximum Residue Levels (MRLs) for glyphosate on certain imported food crops. The rationale was trade alignment with Codex standards.
MRLs do not measure toxicity directly — they set the maximum legal residue permitted in food based on dietary intake models. If you’re unfamiliar with how these limits are calculated, we explain it step by step in What Are Maximum Residue Levels (MRLs)?
But here is the part that deserves scrutiny:
If new research is exploring endocrine and reproductive effects at low doses, are our exposure models calibrated for that possibility? Or are they built around older toxicological assumptions?
That question becomes especially important when you understand how regulators determine the How Safe Is Glyphosate in Our Food? Rethinking the Acceptable Daily Intake — the amount believed safe for lifetime daily consumption.
New Zealand continues to rely on established international assessments. Yet other countries have moved toward restrictions, buffer zones, or precautionary bans in certain contexts.
The global picture is not uniform.
So when MRLs rise here, it is reasonable to ask whether the public has been adequately informed of both sides of the scientific discussion.
Glyphosate vs Roundup: Why Formulations Matter
One area often overlooked in public debate is the difference between pure glyphosate and commercial formulations like Roundup®.
Several studies have examined whether adjuvants and surfactants in commercial products increase cellular toxicity compared to glyphosate alone. Some laboratory findings suggest they may.
Regulatory testing historically focuses on the active ingredient. But real-world exposure often involves full formulations.
That distinction may not sound dramatic.
But it changes the toxicological question entirely.
Endocrine Disruption and Low-Dose Exposure Concerns
Public health policy often waits for definitive proof.
Yet history shows us that waiting for absolute certainty can take decades — sometimes generations.
Applying a precautionary approach does not mean declaring glyphosate guilty of every allegation. It means acknowledging scientific uncertainty where it exists and ensuring monitoring systems are robust enough to detect emerging risks.
If exposure is safe, transparency strengthens public trust.
If exposure assumptions are outdated, early reassessment prevents long-term harm.
Neither position requires panic.
It requires honest evaluation.
Should New Zealand Apply the Precautionary Principle?
New Zealand markets itself as clean and green. Our agricultural reputation is central to our economy.
That makes this discussion uncomfortable.
But avoiding discomfort is not the same as protecting public health.
Glyphosate may ultimately be proven safe at current exposure levels. Or future evidence may reveal nuanced risks we underestimated.
Either way, the public deserves:
- Independent long-term monitoring
- Transparent residue reporting
- Clear explanation of how ADIs and MRLs are calculated
- Open discussion about endocrine-disruption research
The debate is not about ideology.
It is about whether we are asking the right scientific questions — and whether we are prepared to update policy if the answers change.
Resources and References
If you’ve ever wondered why the debate around glyphosate’s safety never seems to settle, these studies help explain why. They don’t claim to have all the answers. But they do illustrate why the scientific discussion remains active.
Take time to read them carefully. Notice the methodologies. Look at the exposure assumptions. Consider what is being measured — and what is not.
Residential Proximity to Agricultural Fields, Urinary Glyphosate Levels and Breast Cancer Risk: A Case-Control Study in Argentina
This study examined urinary glyphosate levels among women living near agricultural fields and found higher concentrations in those residing closer to sprayed areas, alongside an increased breast cancer risk. While causation is not established, the findings highlight the importance of exposure assessment in agricultural communities.
Read the extract
The Chemical Maga Fears Is Making Us Infertile
This Telegraph article explores the growing US debate around glyphosate and fertility concerns, alongside the political dynamics shaping the narrative.
Read the article
Glyphosate MRL Proposal by the Ministry for Primary Industries (MPI)
This official MPI consultation document outlines proposed changes to allowable glyphosate residue levels in food.
Read the proposal
Differential Effects of Glyphosate and Roundup on Human Placental Cells
Published in Environmental Health Perspectives, this study investigates cellular effects of glyphosate and its commercial formulation on placental cells, noting differences in toxicity between the active ingredient and the full formulation.
Read the study
Glyphosate and the Key Characteristics of an Endocrine Disruptor
This review evaluates glyphosate against established endocrine-disruption criteria, suggesting it exhibits several properties associated with EDCs.
Read the study
These sources do not close the case.
They demonstrate why it remains open.
Science evolves. Risk assessments evolve. Public health policy should evolve with them.
The most responsible position is not blind reassurance — or blind alarm — but continued scrutiny.
Image Source & Attribution
We’re grateful to the talented photographers and designers whose work enhances our content. The feature image on this page is by fotokostic. You can find more of their work here: https://www.123rf.com/profile_fotokostic.
