Politics Clashes with Science over Glyphosate and Cancer

Nothing exemplifies the attack on science more than its subversion to politics. The intrusion of political forces into the scientific sphere has distorted the debates over dietary fat, climate change, GMO crops and other controversial topics. Particularly contentious at present is the charge that the weedkiller glyphosate causes cancer, an allegation that’s behind thousands of U.S. lawsuits filed by cancer victims against glyphosate manufacturer Monsanto. The victims, who suffer from non-Hodgkin’s lymphoma, claim the cancer was caused by spraying the company’s glyphosate-based Roundup herbicide.


Best-seller Roundup has been used since 1974 to kill weeds in more than 100 food crops as well as greenhouses, aquatic areas, and residential parks and gardens. It became an especially profitable product for Monsanto in 1996 after the agricultural behemoth introduced Roundup Ready seeds, which are genetically engineered to make crop plants resistant to the herbicide; the revolutionary advance meant that farmers could now use Roundup to kill weeds while the crop was growing, instead of only before planting.

The carcinogenic potential of glyphosate has been evaluated several times in the U.S. by the EPA (Environmental Protection Agency), and in Europe by the EFSA (European Food Safety Authority) and the ECHA (European Chemicals Agency). While all these evaluations concluded that glyphosate was unlikely to be carcinogenic to humans, the IARC (International Agency for Research on Cancer) shocked the world in 2015 by classifying glyphosate as a potential carcinogen. It’s the IARC assessment that underpins the multimillion-dollar mass litigation against Monsanto.

So who’s right? The various government agencies in the U.S. and Europe that see no problem in continuing to use Roundup, or the WHO (World Health Organization)’s IARC? Both camps maintain that the scientific evidence is on their side.

The dispute is an all-too-common example of how politics is invading science. As reported by Reuters last year, the IARC made significant changes between the original draft of its 2015 monograph on glyphosate and the published version. Although it’s not unusual for a final agency report to differ from the draft, what stands out in this case is that the principal changes were the deletion of all statements and findings – and there were many – contrary to the IARC’s ultimate conclusion that glyphosate probably causes cancer.

The agency refuses to say who made the changes or why. If such secrecy alone were not enough to arouse suspicion, Reuters found 10 significant alterations to the draft chapter on animal studies – the very chapter that in the final report provided “sufficient evidence" that glyphosate causes cancer in animals. The draft chapter had reported the conclusions of multiple studies finding no link at all between glyphosate and cancer in laboratory animals. But the final report concluded exactly the opposite.

That the changes to the IARC report were politically rather than scientifically motivated is reinforced by the EPA’s finding that glyphosate poses no carcinogenic risk to humans. This conclusion was also reached by the EFSA, the ECHA and the UN’s FAO (Food and Agriculture Organization) – despite the EFSA and ECHA, like other European agencies, being more conservative and pro-environment than their U.S. counterparts. Not surprisingly, the environmentally activist organization Greenpeace has called the EFSA report faulting the IARC declaration “a whitewash.”

By far the greatest amount of scientific data on the possible human carcinogenicity of glyphosate comes from a 2005 study of 85,279 American farmers and their spouses. The so-called AHS (Agricultural Health Study) included epidemiological, animal carcinogenicity, and genotoxicity investigations to elucidate the carcinogenic potential of Roundup products.

Both the EPA and the IARC utilized the AHS data in their recent, conflicting evaluations of glyphosate. However, the IARC monograph also included a number of “low-quality” studies that the EPA elected to omit. Although this may seem arbitrary on the EPA’s part, the studies omitted by the EPA lacked, for example, information on glyphosate exposure of individual subjects. Such shortcomings are important in light of the current reproducibility crisis in the biomedical sciences: up to 90% of published findings in some areas of biomedicine can’t be replicated. The inclusion of scientifically inferior data by the IARC strongly suggests political interference in the scientific process.

Of six specific studies that investigated the association between glyphosate exposure and non-Hodgkin’s lymphoma – the possible linkage at issue in the mass lawsuits – the EPA stated that “a conclusion … cannot be determined based on the available data.” Nevertheless, for cancer overall, the EPA report found the strongest support for an assessment of glyphosate exposure as “not likely to be carcinogenic to humans,” which is the weakest of five EPA risk classifications on cancer.

Meanwhile, the jury in the first trial of the Roundup litigation ruled on August 10 that Monsanto’s weedkiller was a substantial contributing factor in causing non-Hodgkin’s lymphoma and ordered the company to pay $289 million in damages, a figure since reduced to $78 million on appeal. With further trials scheduled in 2019, only time will tell who is right about the science.

Next week: When No Evidence Is Evidence: GMO Food Safety