Federal court finds insufficient evidence Roundup weedkiller causes cancer. What does the science say?

The Federal Supreme Court class action lawsuit was dismissed this week after Judge Michael Lee ruled there was not enough evidence to prove the weedkiller Roundup causes cancer.

Plaintiff Kelvin McNickle, currently at the age of 41He developed non-Hodgkin’s lymphoma after using glyphosate (the energetic ingredient in Roundup) in his family’s plant care business for more than 20 years.

More than 800 others joined class action lawsuit against German chemical and pharmaceutical company Bayer, which produces Roundup. Bayer has long maintained that glyphosate does not cause cancer, despite numerous lawsuits around the world. he said This week’s ruling was a “victory for Australian farmers.”

The court acknowledged that the scientific community has mixed views on whether glyphosate causes cancer. Judge Lee he was looking at In his ruling, he cited three types of scientific evidence – epidemiological, animal studies and evidence showing the mechanisms involved in the development of cancer.

However, in 2015 International Agency for Research on Cancer (IARC) has classified the herbicide as “probably carcinogenic to humans.”

So what does science say?

What is glyphosate?

Glyphosate is one of the most widely used herbicides in the world and has been used in agriculture, public parks and paths, and home gardens in Australia for over 40 years.

It kills weeds by affecting a specific pathway (shikimic acid pathway) found in plants and a certain type of bacteria (eubacteria), but not animals (or humans).

When it comes to short-term exposure, glyphosate is less toxic than table saltFor example, a 70-kg person would have to eat a quarter of a kilogram of table salt to die, but would have to eat about half a kilogram of glyphosate to die.

However, it is chronic, long-term exposure to glyphosate that is causing controversy.

What does “probably carcinogenic” to humans mean?

Those who believe glyphosate causes cancer often cite a 2015 report by the International Agency for Research on Cancer (IARC) that classified the herbicide as “probably carcinogenic to humans.” It was based on:

convincing evidence that these agents cause cancer in laboratory animals.

However, IARC reached its conclusion using a narrower evidence base than other peer-reviewed articles and government reviews. Furthermore, unlike other regulatory bodies, it flags any possibility causing cancer, not risk from probable exposures.

Report of the Joint Meeting of the Food and Agriculture Organization of the United Nations/World Health Organization on Pesticide Residues 2016 Completed that glyphosate is unlikely to pose a carcinogenic risk to humans through dietary exposure.

Contrary to IARC’s confident conclusion that there is convincing evidence that glyphosate causes cancer in laboratory animals, the joint meeting concluded:

Glyphosate is not carcinogenic to rats, but the possibility that it is carcinogenic to mice at very high doses cannot be ruled out.

The Australian regulatory authority, the Australian Pesticides and Veterinary Medicines Authority, Rated the safety of glyphosate as determined by IARC and Completed:

There is no credible evidence that products containing glyphosate pose a risk of causing cancer in humans.

What have epidemiological studies shown?

The IARC considered ten cohort studies, in which study participants were followed over a period of time, and nine case-control studies, in which people with the disease were compared with groups who did not have the disease to try to identify possible causes. There was no evidence of an association with cancer.

However, three tiny studies he suggested association with non-Hodgkin’s lymphoma, but this association was not statistically significant. This means that the association may have occurred by chance.

AND 2016 meta-analysis which reviewed all available evidence at the time suggested a tiny but not statistically significant association between glyphosate and non-Hodgkin’s lymphoma, but no causal relationship was established.

In 2018 Agricultural Health Research was published. It was a long-term study of 54,251 participants with a license to exploit glyphosate, where their exposure could be tracked. This tough study, which controlled for a number of factors that could confound the conclusion, found no statistically significant associations between glyphosate exploit and cancer at any site.

What do animal studies say?

There have been many animal studies on glyphosate and cancer. In these studies, rodents are typically exposed to high but sublethal concentrations for at least 80% of their total lifetime. These concentrations will be higher than what humans would likely be exposed to.

In European Food Safety Authority Review 2015Nine studies were conducted in rats in which no cancer was observed.

There were also five studies in mice in the review. Three of them were negative. One showed sporadic tumors that were not dose-related (indicating that glyphosate was not a causative factor). In the second study, the researchers found tumors only in males at the highest doses.

Animal studies do not show consistent evidence of cancer development and there is no equivalent of human non-Hodgkin’s lymphoma. The European Food Safety Authority has therefore concluded that glyphosate is unlikely to pose a carcinogenic risk to humans.

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Read more: Research Check: Should We Be Concerned About Glyphosate in Our Beer and Wine?

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In a 2015 report by the International Agency for Research on Cancer (IARC), report which classified the herbicide as “probably carcinogenic to humans,” six studies were conducted in rats. Cancer was observed in only one study, but again, this was not dose-related. This indicates that glyphosate was not the causative factor.

Two studies were conducted in mice: one yielded a negative result, and the other showed a “tendency” for cancer to form in glandular tissue in men but not in women.

No case consistent with human non-Hodgkin’s lymphoma was observed.

IARC concluded that there was sufficient evidence that the tumor could cause cancer in animals, but there was no consistency as to the type of tumor (mice or rats) or its location.

What mechanisms might be involved?

Chemicals can cause cancer in many ways, most commonly by damaging DNA or chromosomes.

In the case of glyphosate, there is little evidence for the involvement of these classical mechanisms.

Bacterial mutation studies to look for bacterial DNA damage have been negative, mutation studies in mammalian cell lines have been negative, and chromosomal damage studies have been largely negative. These studies involve concentrations and routes of exposure that humans will never encounter.

Oxidative stress occurs when there is an imbalance of toxic free radicals and antioxidants in the body, which leads to cell damage. Oxidative stress is associated with cancer and has been suggested to Oxidative stress may be a possible mechanism to cause cancer. Although this damage may be linked to causing cancer, it may also be part of a mechanism that the body It is used to fight cancer.

However, although oxidative stress has been shown to Cellular research AND animal research In the case of glyphosate exposure, the concentrations were much higher than those to which humans are exposed.

Although glyphosate exposure may alter markers of oxidative stress in humans, these changes are relatively smallGiven the lack of evidence for cancer induction in animal studies and human epidemiology, the significance of these minor changes is unclear.

Overall, there is currently no credible mechanism for glyphosate to cause cancer at the concentrations to which humans are exposed.