Photo: AFP
Government agencies are confident the herbicide glyphosate is safe, despite the retraction of a widely referenced study due to corporate meddling.
The 2000 study by Gary Williams, Robert Kroes and Ian Munro had long been treated as an authoritative source on the safety of glyphosate, but court documents released in 2017 revealed it had been substantially ghost-written by employees of agri-tech giant Monsato, now under Bayer.
But further studies had backed up its findings, and the New Zealand government said it didn't need to reassess glyphosate's safety.
The Williams study wasn't retracted until 2025, when New Zealand-based scientist Alexander Kaurov formally requested it while working on a broader study about corporate ghost-writing.
"We didn't plan to go for glyphosate specifically, we were interested in corporate influence on science," he said.
Dr Kaurov chose to use the Williams paper as a case study, but discovered it had never been retracted.
"We wrote to the editor of the journal asking why it's not retracted and it turns out we were the first people to ask for a retraction," he said.
"In this particular case it's important because glyphosate is the most popular herbicide on the planet, so if we want to keep scientific records around glyphosate straight it's important to keep it straight from the beginning and correct all the problems right away."
Dr Kaurov said the highly influential study was in the top 0.1 percent of most cited papers on the topic of glyphosate, and had influenced government policy around the world.
"The problem is a lot of science since 2000 has been built on top of this review, so essentially you're out the brick at the bottom of the pyramid ... Probably it will be fine but if you take out a couple more, then it will be a problem," he said.
Shaun Presow, manager of hazardous substances reassessments at the Environmental Protection Authority, clarified the Williams study hadn't influenced any decisions.
"This paper has not be used by the EPA in making any decisions on glyphosate," he said.
"It was referenced in an EPA report in 2016, but only as part of a broader overview of the science of glyphosate at the time."
But Presow said the retraction was noteworthy.
"It reminds us that we need to be careful when considering information and making sure the conclusions they make are backed up by multiple studies," he said.
He said the EPA wouldn't reassess glyphosate.
"We decided in 2024 that there weren't grounds to reassess glyphosate, and this was based on a large amount of more recent data that is publicly available... And this decision remains valid," he said.
"The retracted paper has no effect on this so there's no reason to reassess that decision."
Meanwhile, NZ Food Safety said the maximum residue levels it set for glyphosate were supported by international data, which was backed by the World Health Organization, and the retraction wouldn't influence its decision making.
It said international bodies agreed that glyphosate posed a very low health risk from food when it was used as directed.
A spokesperson for Bayer, which acquired Monsanto in 2018, defended its involvement in the Williams study.
"Monsanto's involvement with the Williams et al paper did not rise to the level of authorship and was appropriately disclosed in the acknowledgements. The listed authors had full control over and approved the study's manuscript," they said in a written statement.
"Two prior inquiries into the study previously found that the paper was appropriate, including the European Food Safety Authority and Williams' former employer."
They reiterated that further studies had corroborated glyphosate's safety.
"Glyphosate is the most extensively studied herbicide over the past 50 years. Thousands of studies have been conducted on the safety of glyphosate products, and the vast majority of published studies had no Monsanto involvement," the spokesperson said.
"The consensus among leading regulatory bodies worldwide is that glyphosate can be used safely as directed and is not carcinogenic."
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