Avoiding evidence about cancer (linked to Glyphosate of course)

October 2021

Because humans can't be subjected to experimentation, regulators assessing the safety of a chemical have to weigh whatever other, imperfect, evidence they have at their disposal. Safety assessment is particularly challenging when dealing with a possible carcinogen, such as glyphosate herbicide [1]. It's even trickier, it seems, when the chemical is, like glyphosate, a major money-spinner produced by the powerful biotech industry for use on its commodity GM crops [2].

There are two important types of evidence available to regulators: laboratory experiments using animal models, and epidemiological studies. Neither can yield definitive conclusions, and their limitations are particularly evident in investigations of suspected carcinogens.

The shortcomings of animal models stem from the biology of cancers.

Susceptibility to cancer is affected by a host of interacting factors: besides environmental and chemical stressors, the health of the cell, nutrition, age, underlying conditions, lifestyle and genetics all play a part. Hormones and the sex of the individual are major contributing influences. Although some stressors may tend to be linked to specific types of cancer in specific organs, there are no hard and fast rules, and cancerous cells sometimes go walkabout in the body. Cancer isn't an acute condition: it arises years or decades after the stressors have done their damage.

What this means for animal cancer experiments is variability: if they involve different exposures to the suspected carcinogen, different animals, different genetic strains of the same animal, different sexes (with different hormones), different feed and housing conditions, different laboratories, and even the same laboratory at different times, they can be expected to get different results. Unlike other toxins, a cancer-causing agent may have no safe limit and no simple dose-related response. For these reasons, regulatory guidelines specify that overall trends of cancer incidence should be accepted as an indication of carcinogenicity.

In reality, despite the guidelines, EU and US regulators, whose job it is to protect the public from harmful chemicals, seem to be surprisingly willing to use this inherent variability in the outcomes of tests for cancer as a means to dismiss damaging evidence and to approve whatever toxic substance industry wants to profit from.

When a concerned scientist re-analysed thirteen studies of rodents chronically exposed to glyphosate, and applied the statistical tests regulators had ignored, a very different picture of the herbicide's potential to cause cancer emerged. The newly presented information included overall trends, individual data, data consistency across studies, and historical controls plus associated studies. The overview of evidence given by these tests suggested glyphosate can be linked to cancers of the blood vessels and skin, to kidney, liver and adrenal tumours, and to immune cell cancer.

The authors noted that regulators not only feigned ignorance of the biology of cancers to avoid seeing indications of the disease, but had clearly failed to follow their own guidelines: trend tests were ignored, while absence of dose response, cancer incidence in one sex only and study differences were all wrongly used to eliminate data. In one case an undocumented viral infection in the test animals was used to avoid including a positive cancer finding. In another case a negative cancer finding was included despite the regulators identifying underlying falsified data. Inappropriate use of historical controls to shift the goal-posts so wide apart that a positive cancer finding becomes impossible seems to be endemic in the whole regulatory system.

As the authors concluded: 

"Had regulatory authorities conducted a full reanalysis of all of the available evidence from the 13 animal carcinogenicity studies as was done here, it is difficult to see how they could reach any conclusion other than glyphosate can cause cancers in experimental animals."

The shortcoming of epidemiological studies is that they can't prove cause-and-effect.

Argentina, where glyphosate-sprayed GM crops are grown on many millions of hectares*, has carried out two key studies on its rural populations.

* 25 million hectares in 2017

The biggest survey has been in Monte Maíz, a typical small Argentine agricultural town surrounded by GM crops and exposed daily to spray drift. Analyses of the soil and husk dust in the town revealed unexpectedly high levels of glyphosate contamination. Although Monte Maíz is an affluent town (thanks to the profits from GM crops) where the population should be counted among the healthier in the country, the cancer incidence there is two to three times the national average.

An earlier study compared three soya farming villages which used glyphosate with two cattle-raising villages where glyphosate wasn't used. It found cancer death frequencies of 30-39% in the soya-growing populations, compared with only 3-5% in the cattle-raising populations.

These studies strongly suggest a link between glyphosate and cancer, but they're unable to prove cause-and-effect. Such evidence is easy for regulators to avoid.

OUR COMMENT

Glyphosate is just one tiny part of the whole GM crop safety issue. Currently, this long-used problematic herbicide is being joined by a host of new herbicides each with its own GM herbicide-resistant crops and each with its own cancer-causing potential. Just for starters, watch out for dicamba [3], isoxaflutole [4] and 2,4-D [5] in your food and environment. And that could mean exposure to any one of these herbicides, or to all four. Each one will muddy the waters of epidemiological outcomes still further, and make them ever easier to avoid.


Background

[1] GLYPHOSATE IS A PROBABLE CARCINOGEN - May 2015

[2] ROUNDUP ON TRIAL - May 2019

[3] DICAMBA - WORSE THAN GLYPHOSATE - October 2021

[4] ISOXAFLUTOLE - THE NEXT HERBICIDE HEADACHE? - October 2021

[5] 2,4-D ON THE MENU TOO - October 2021


SOURCE:

• Christopher J. Portier, 2020, A comprehensive analysis of the animal carcinogenicity data for glyphosate from chronic exposure rodent carcinogenicity studies, Environmental Health 19:18
• Medardo Avila-Vazquez, et al., February 2014, Association between Cancer and Environmental Exposure to Glyphosate, International Journal of Clinical Medicine, 8

Photo: Crop spraying. From Creative Commons