Does glyphosate cause cancer? Australia’s Roundup case against Monsanto will offer a fresh legal answer

The class action will be decided by a single judge and could be a ‘genuine problem for Monsanto and Bayer if we’re successful’, lawyer says

From his mid-teens, Kelvin McNickle began helping out in his family’s vegetation management business in Queensland. As part of the work, he regularly used the herbicide Roundup, sometimes ending the day saturated in the weedkiller despite using protective equipment. At 35, after 20 years of exposure to the glyphosate-based herbicide, McNickle developed non-Hodgkin lymphoma – cancer of the lymphatic system.

Now 40, McNickle is the lead applicant in a landmark class action against Monsanto, the chemical giant which was acquired by the German company Bayer in 2018. It involves more than 800 Australians with the condition, who allege their cancer is linked to their exposure to Roundup between July 1976 and July 2022.

The judge-only trial mirrors legal challenges in other countries, and could have significant regulatory implications in Australia if the applicants are successful.

The first part of the case, which began on 4 September and will run for several weeks in the federal court in Melbourne before Justice Michael Lee, seeks to specifically establish whether glyphosate is carcinogenic.

“If that question is answered positively to us, then there’s still more that will need to be done before we can obtain compensation for people,” says Andrew Watson, the national head of class actions at Maurice Blackburn Lawyers, which has brought the case against Monsanto.

If the class action group members are successful in the first part of the trial, the court will then consider whether the chemical company was negligent with regard to the risk posed by its glyphosate-based formulations.

Carcinogenic risks contested

Glyphosate, one of the most widely used herbicides globally, kills weeds by interfering with a plant pathway that produces certain amino acids, the building blocks of proteins. It was patented by Monsanto in the early 1970s, although the patent has now expired.

Legal challenges began overseas in 2015, after the World Health Organization’s International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans”, in the same category as eating red meat and drinking beverages hotter than 65C. Its conclusion was based on “sufficient” evidence that the compound causes cancer in animal experiments, and “limited” evidence of cancer in humans from real-world exposure.

The IARC’s classification also noted there was “strong” evidence that glyphosate was genotoxic – able to damage the genetic information within cells, which can lead to mutations that result in cancer.

But the evidence for its carcinogenicity has been highly contested – other agencies, including the European Chemicals Agency, Canada’s Pest Management Regulatory Agency and the Australian Pesticides and Veterinary Medicines Authority (APVMA), have concluded that glyphosate does not pose significant carcinogenic risks to humans.

Last week the European Commission proposed extending the EU approval for glyphosate use – which is set to expire in December – by 10 years. The proposal will be put to a vote on 13 October. Individual member states, however, including France and Germany, have opted for partial restrictions or total bans of the weedkiller.

In the US, a 2020 review by the Environmental Protection Agency (EPA) found that glyphosate was unlikely to be a human carcinogen. But in June last year, an appellate court ordered the EPA to re-review the chemical, finding that officials had discounted several important studies and that “most studies EPA examined indicated that human exposure to glyphosate is associated with an at least somewhat increased risk of developing NHL [non-Hodgkin lymphoma]”.

Bayer has faced numerous lawsuits in the US. It has had a string of recent successes defending Roundup at trial, but the firm has paid out about $10.9bn to settle or otherwise resolve cases brought against it by 113,000 claimants.

What the scientists say

The first part of the Australian court case is hearing from scientists testifying on behalf of both the claimants and Monsanto.

The court has heard evidence on epidemiological studies in humans, from which it can be difficult to establish carcinogenicity, as such research must follow large numbers of people over long periods of time.

One of the largest studies, the Agricultural Health Study, followed tens of thousands of pesticide applicators in the US for 20 years from the early 1990s, finding no apparent association between “glyphosate and any solid tumours or lymphoid malignancies overall, including NHL and its subtypes”. However, a 2019 meta-analysis that included the Agricultural Health Study and five other studies found “a compelling link between exposures to [glyphosate-based herbicides] and increased risk for NHL”.

Mechanistic evidence – looking at the means by which a chemical causes cancer in cells – is also being considered in the trial, which Watson describes as the area “where the strongest evidence emerges”. As the IARC noted in its 2015 classification, studies have shown that glyphosate can result in DNA damage and also induce a process known as oxidative stress in cells, which has been linked to the development of cancer.

In the coming weeks, experts will testify on evidence of carcinogenicity from animal experiments – whose results are not always applicable to humans – and also on exposure, to establish whether glyphosate could be absorbed in sufficient quantities through herbicide use to cause cancer.

Closing submissions for the first portion of the trial are expected on 31 October.

Monsanto’s position is that Roundup and glyphosate-based herbicides “have been rigorously tested in hundreds of studies, that the weight of this extensive body of science confirms that glyphosate is safe when used as directed and is not carcinogenic”.

The chemical company is arguing that there are other reasons the litigants may have developed non-Hodgkin lymphoma, such as genetic predisposition, random chance, and gene changes and DNA mutations caused by other factors.

‘Devastating impact on his life’

The last formal review of glyphosate by Australia’s pesticides regulator, the Australian Pesticides and Veterinary Medicines Authority (APVMA), was in 1997.

In 2016, following the IARC classification, the authority said it “found no grounds” to formally reconsider the herbicide’s status.

It noted that the IARC looked at the “intrinsic toxic potential or ‘hazard’ of the chemical glyphosate”, but that it was beyond the remit of the international agency to consider how “actual use and exposure affects the final overall risk (risk = hazard x exposure)”.

“Glyphosate does not pose a carcinogenic risk to humans,” the APVMA concluded.

“It is Monsanto’s view that IARC’s classification is inconsistent with the conclusions of regulatory authorities and other experts around the world,” Bayer said in a statement provided to Guardian Australia. “According to IARC, IARC ‘identifies cancer hazards even when risks are very low at current exposure levels.’ In our view this means that IARC’s classifications do not reflect real-world levels of exposure.”

In July a review of the APVMA initiated by the agriculture minister, Murray Watt, criticised the authority for the slow pace of its work reviewing chemicals already on the market, without making any judgment about the effects of particular chemicals.

“It appears that the APVMA has limited capacity to progress ongoing monitoring activities, with the most notable example being the protracted progression of its Chemical Review Program,” the review found.

In a statement, Bayer said it “respects the independence and expertise of the APVMA” and noted that the review concluded that the “registration process continues to uphold the stringent regulatory requirements which ensure the safety and efficacy of agricultural chemical products”.

“I’m not imagining that there will be a review of Roundup [by the APVMA] now,” Watson says, given the current class action before the court. “If we are successful in our claim, then I would hope that the regulator takes appropriate steps.”

After undergoing chemotherapy and radiotherapy, McNickle went into remission in 2019, but has subsequently had a recurrence of cancer this year.

“His circumstances obviously had a pretty devastating impact on his life,” Watson says, describing the recurrence as a further blow. “Kelvin’s is a particularly stark case, but a lot of people of that 800 [involved in the class action] had reasonably significant amounts of exposure.”

What distinguishes the Australian court case from US trials, Watson says, is that the outcome will be decided by a judge, whose detailed consideration of all the evidence is likely to be “more powerful and persuasive” than decisions handed down by juries.

“I think it will be a genuine and significant and widespread problem for Monsanto and Bayer if we’re successful in this trial.”


Donna Lu Science reporter

The GuardianTramp

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