Glyphosate is the most widely used herbicide in the world, and is particularly popular with farmers growing common food crops. But there is heated debate in many countries about whether or not glyphosate herbicides should continue to be used due to concerns they may cause cancer. The new finding of flaws in industry studies means regulatory assurances about glyphosate safety in Europe and the United States have been based, at least in part, on shoddy science.
Corporate-backed scientific studies are raising troubling questions about a history of regulatory reliance on such research in assessing the safety of the widely used weedkilling chemical known as glyphosate, the key ingredient in the popular Roundup herbicide.
In a 187-page report researchers from the Institute of Cancer Research at the Medical University of Vienna in Austria said a thorough review of 53 safety studies submitted to regulators by large chemical companies showed that most do not comply with modern international standards for scientific rigor, and lack the types of tests most able to detect cancer risks.
“The quality of these studies, not of all, but of many of these studies is very poor. The health authorities … accepted some of these very poor studies as informative and acceptable, which is not justified from a scientific point of view,” Siegfried Knasmueller, the lead author.
The new analysis challenges safety assurances, finding that much of the methodology used in the industry studies is outdated and not in keeping with international quality standards. Of the 53 studies submitted to regulators by the companies, only two were acceptable, according to current internationally recognized scientific standards, said Knasmueller.
The corporate studies at issue focus on the genotoxic properties of glyphosate – whether or not it causes DNA damage – and they support corporate assurances that the chemical is safe when used as directed and does not cause cancer. They were commissioned and/or conducted by the former Monsanto Co, which is now a part of Bayer AG, as well as Syngenta, Dow, and others involved in making and/or selling glyphosate.
Particularly problematic was the focus on testing for chromosome damage in early stages in red blood cells of the bone marrow in laboratory mice and rats. These tests routinely detect only 50-60% of carcinogens, according to Knasmueller. “So many carcinogens are not detected with this method,” he said.
A type of test known as “comet assay” has a much higher value for identifying carcinogens because it can quantify and detect DNA damage in individual cells in a variety of organs, and is commonly used for evaluating genotoxicity, according to Knasmueller. But no comet assay tests were included, according to the analysis.
“I cannot understand why the health authorities did not ask for such data,” said Knasmueller, who is an expert in genetic toxicology.
Linda Birnbaum, former director of the US National Institute for Environmental Health Sciences, said there has been an ongoing problem that is not unique to glyphosate with regulators taking industry studies “at industry’s word” while ignoring red flags raised in non-industry-funded research.
“This puts once more a finger on a sore spot: that national regulators do not seem to pay close scrutiny when looking at the quality of industry’s studies,” said Nina Holland, researcher at the watchdog group Corporate Europe Observatory. “This is shocking as it is their job to protect people’s health and the environment, not to serve the interests of the pesticide industry.”
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