We’re told that when regulators say “glyphosate is safe,” they mean safe for everyone.
But is that really true? What if men and women don’t respond the same way? What if the risks depend not just on the dose, but on who’s exposed?
A new study using zebrafish — one of the go-to models for human health research — has thrown a spanner in the works. It found that Roundup® WG, a commercial glyphosate-based weedkiller, caused sex-specific liver damage. In plain language: male and female bodies didn’t cope with the chemical in the same way. One group’s livers — the body’s detox powerhouse — showed more strain than the other.
That should make us all stop and think. Because the truth is, most of the safety studies regulators lean on don’t even ask this question. They test glyphosate in isolation, often on male animals only, and then assume the results apply across the board. We’ve already raised concerns about this in our article Glyphosate Gender Risks: Why Women Face Higher Stakes. Now, this new research adds weight to the case: glyphosate-based weedkillers don’t affect all bodies equally — and pretending they do is another dangerous blind spot.
The Zebrafish Study
So what did the researchers actually do? They exposed zebrafish (Danio rerio) — a tiny freshwater fish often used in medical and toxicology research — to Roundup® WG, a commercial glyphosate-based herbicide. Zebrafish may not look much like us, but their biology has surprising similarities. That’s why they’re so widely used to model human liver function, hormonal systems, and even brain chemistry.
The team wanted to know whether exposure would affect males and females differently. And it did. They measured a series of oxidative stress markers and looked closely at the fish livers. What they found was clear: Roundup® WG triggered liver damage, but the effects weren’t the same across sexes.
Some of the fish showed higher oxidative stress and more signs of hepatotoxicity (liver injury) than others — simply because of whether they were male or female. In other words, this wasn’t just “general toxicity.” It was sex-specific toxicity.
That raises some uncomfortable questions. If Roundup® can stress male and female zebrafish livers in different ways, what does that mean for people? For women who are already more vulnerable to endocrine disruption? For men with existing liver conditions? And most importantly: why are regulators still pretending that one-size-fits-all safety studies are enough?
Why the Liver Matters
The liver doesn’t get much attention in everyday conversations about health, but it should. It’s the body’s detox powerhouse — breaking down toxins, filtering blood, and keeping the system running smoothly. If the liver is under stress, the whole body feels it.
That’s what makes the zebrafish findings so important. Liver damage isn’t a minor side effect. It means the body’s first line of defense against chemical exposure is compromised. And when the chemical in question is something as widely used as Roundup®, that should ring alarm bells.
Think about it: we’re told glyphosate is safe at the “levels people are exposed to.” But if Roundup® formulations can damage liver function in ways that differ between males and females, how can a single safety threshold possibly capture that? It can’t. One body might cope — another might not.
Most glyphosate safety assessments don’t even look at this level of detail. They don’t test full formulations. They don’t account for sex differences. They just average the data and call it good enough. But when it comes to the liver — the organ that keeps toxins from overwhelming us — can we really afford to rely on averages and assumptions?
If fish livers can’t cope with Roundup®, what about ours?
Male vs Female Susceptibility
This isn’t the first time science has uncovered differences between how male and female bodies respond to chemicals, but it’s a reminder we can’t ignore. For decades, medical research was built around a “default male” model — drugs were tested mainly on men, lab animals were often male only, and results were assumed to apply to everyone. We now know that’s not true.
The same blind spot shows up in toxicology. Hormones, metabolism, and even body fat distribution can all influence how a chemical is absorbed, stored, or broken down. That means a dose that looks “safe” for one sex may not be safe for the other. The zebrafish study makes this point hard to miss: Roundup® WG didn’t just cause liver damage — it caused different damage depending on whether the fish were male or female.
So what happens when regulators set one universal “acceptable level” of glyphosate exposure? Whose body are they really protecting? And whose risks are they downplaying? These are uncomfortable questions — but they go right to the heart of how chemical safety is defined, and who ends up carrying the burden when shortcuts are taken.
The Regulatory Blind Spot
Here’s the problem: regulators don’t usually ask whether a chemical affects males and females differently. In fact, most of the studies they rely on don’t even make that distinction. They test glyphosate in isolation, often on male animals only, and then use those results to set exposure limits for the entire population.
That leaves a gaping hole. If formulations like Roundup® WG can damage male and female livers in different ways, then any “average” safety threshold built on incomplete data is misleading at best — and dangerous at worst. It’s not just about zebrafish in a lab. It’s about whether our own regulatory system is fit for purpose when it comes to protecting real people with different bodies, different vulnerabilities, and different risks.
This blind spot isn’t unique to glyphosate, but glyphosate is a perfect example of why it matters. A weedkiller sprayed across our crops, our roadsides, and even near schools should be held to the highest testing standards. Instead, we get narrow studies, selective data, and assumptions that sweep inconvenient differences under the rug.
So the real question is: how many risks are hidden in those averages? And how much damage has to be done before regulators admit that “one size fits all” doesn’t actually fit anyone?
Implications for New Zealand
For New Zealand, the zebrafish findings aren’t just an academic curiosity — they hit close to home. Roundup® and other glyphosate-based weedkillers are everywhere here: sprayed on crops before harvest, on council verges, in playgrounds, and even around school grounds. If these formulations can damage livers differently in males and females, then our current approach to safety looks dangerously out of date.
Food safety: Our residue limits are set as though all bodies respond the same way, yet this study shows that’s not true. A slice of bread or a bowl of cereal might meet the “legal” threshold, but what if that threshold doesn’t protect everyone equally? We’ve already found residues in honey and cereals — but those limits are set as though all bodies respond the same way.
Public spraying: Councils apply glyphosate in busy public spaces without warning signs, let alone consideration of whether pregnant women, children, or those with pre-existing conditions might be more vulnerable. If regulators aren’t even asking whether male and female bodies respond differently, how can local authorities claim these exposures are safe?
Health equity: Māori, Pasifika, and working-class communities are often closer to roadside spraying or more likely to be in occupations with glyphosate exposure. Add in the overlooked dimension of sex-based vulnerability, and the blind spots in New Zealand’s risk framework get even bigger.
In short: New Zealand’s safety net isn’t woven tightly enough to catch everyone. And when it comes to chemicals like Roundup®, the gaps fall along the lines of biology, equity, and basic precaution.
Rethinking ‘Safe’
The zebrafish study reminds us of something simple yet often ignored: glyphosate-based weedkillers don’t affect every body the same way. Male and female organisms can react differently, sometimes in ways that expose vulnerabilities safety studies never account for.
That means every time regulators wave away concerns with “safe at approved levels,” we should be asking: safe for whom? Because when Roundup® WG can trigger sex-specific liver damage in fish, it’s not such a leap to question whether the same blind spots exist for us.
New Zealanders deserve better than one-size-fits-all safety claims built on half the data. We deserve science that reflects the realities of real bodies, real communities, and real-world exposures. Until then, “safety” is just another assumption — and assumptions don’t protect our health.
Resources & References
Behind the “safe at approved levels” mantra lies research that regulators rarely mention. These resources highlight why sex differences matter — and how glyphosate-based weedkillers pose risks that don’t show up in averaged data.
Sex-specific hepatotoxicity in zebrafish (Danio rerio) induced by Roundup WG® exposure
The study showing that Roundup® WG caused liver damage that varied between male and female zebrafish, revealing the blind spot in one-size-fits-all safety assessments.
Read the study on ResearchGate
Glyphosate Gender Risks: Why Women Face Higher Stakes
Our earlier article exploring why glyphosate may pose unique risks for women, from hormonal disruption to higher cumulative exposures.
Read on NoMoreGlyphosate.nz
Roundup vs Glyphosate Toxicity
A breakdown of why real-world formulations like Roundup® are often more toxic than glyphosate alone, with evidence on the role of additives such as surfactants.
Read on NoMoreGlyphosate.nz
Implication of sex differences in toxicology (2024)
A more recent analysis of how sex-based biology influences exposure, metabolism, and risk, underscoring the urgent need for regulators to stop treating “average” data as universal.
Read more on Science Direct
Sex differences in toxicology: A neglected variable – A landmark review showing how male and female organisms can respond differently to chemical exposures, highlighting why sex-specific data is essential.
Read the review on PubMed
Together, these resources remind us that glyphosate-based weedkillers don’t affect every body the same way. Ignoring sex-specific risks doesn’t make them disappear — it just leaves regulators and the public in the dark.
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