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Glyphosate, the active ingredient in the world’s most widely used weedkiller, does not cause cancer. Yet, for the second time, a jury has recently sided with the plaintiff in a lawsuit alleging that glyphosate does and did cause cancer. What are we to make of this? Should we stop using this weedkiller to keep our driveways weed free? Should it be banned? To answer such questions can be complicated—but it need not be. Let us consult some data and experience.
What follows is a story in three parts:
- an exadumbration of the origin of the myth of glyphosate carcinogenicity, which myth is the foundation for the lawsuits, and a survey of the considered judgments of scientific and regulatory authorities around the world;
- a summary of what the world’s farmers think about the safety and value of glyphosate; and
- a commonsense question which, when asked, demonstrates that the claim of carcinogenicity is illogical and unreasonable.
1.The myth of glyphosate carcinogenicity
Whence came the notion that glyphosate might be a carcinogen? The primary impetus was born with a 2015 classification by the International Agency for Research on Cancer, IARC. IARC is a loosely attached subordinate body to the World Health Organization (WHO) dedicated to “…promot[ing] international collaboration in cancer research.” It is not a regulatory agency, and it doesn’t conduct risk assessments. It was set up in 1965 to prepare “a compendium on carcinogenic chemicals.” It does this by convening groups of experts to examine candidate compounds and publish their findings in Monographs that “embody principles of scientific rigour, impartial evaluation, transparency, and consistency.” Their monograph on glyphosate, based on a single meeting of one week, published 2 years after their classification was announced by press release, is Number 112. It does not satisfy those criteria.
The sins of IARC and the facts about glyphosate’s safety have been catalogued at length by many voices. And it’s worth noting that the WHO has three times considered and rejected the claim that glyphosate is carcinogenic, so there’s that. Even Mother Jones joined Reuters in noting that IARC had deliberately suppressed inconvenient findings from the Agricultural Health Study (AHS), the largest ever survey of farm chemical applicators (N=54,251) which concluded “…no association was apparent between glyphosate and any solid tumors or lymphoid malignancies overall, including NHL [Non-Hodgkin’s’ Lymphoma] and its subtypes.” And while the AHS data on glyphosate had not yet been published by 2015, the data were not only available but well known to one of its authors, the chairman of IARC’s monograph team, Aaron Blair, who admitted in a legal deposition that the AHS data, if IARC had considered it, would have prevented it from classifying glyphosate as a “probable carcinogen.” Why IARC did not review these data, and why it has not undertaken to revise its classification in light of these fresher, much more powerful data, is unclear. What is abundantly clear, however, is that these failures violate IARC’s own published standards which require such updating. But suppressing critical data (which counts as unethical misconduct in academic circles) is just the beginning of IARC’s sins.
In addition to ignoring inconvenient data, IARC misrepresented and wrongly cited papers it claimed supported its carcinogenicity classification of glyphosate. One of these looked at rural Colombians exposed to glyphosate sprayed in coca eradication campaigns. IARC cited it to support claims that glyphosate is “genotoxic”—i.e., causes genetic changes of the sort that might lead to cancer. Yet one of the study’s principal authors, Keith Solomon, insisted that conclusion is “totally wrong.” He should know, as an article in Western Producer noted, because he wrote the Colombian study. “They stated there was evidence of genotoxicity and they quoted one paper to support that statement,” Solomon was quoted as saying. “There’s no evidence that glyphosate is genotoxic.” Other scientists have also looked at the data on which IARC claims its determination was based and found they do not support the IARC classification, including the former Biostatistics Director at the International Epidemiology Institute and retired National Cancer Institute statistician Robert Tarone, who lays out in considerable detail why scientists generally agree “that the classification of glyphosate as a probable human carcinogen was the result of a flawed and incomplete summary of the experimental evidence evaluated by the Working Group.” This is why every regulatory body that has looked at glyphosate worldwide has reached conclusions opposite to that of IARC. The Genetic Literacy Project has summed it up in one infographic:
So the question becomes—how did IARC reach its verdict?
The answer has been uncovered in a series of muck-raking excavations by David Zaruk, aka “the Riskmonger.” Zaruk discovered some fascinating facts. Apparently, unbeknownst to the world, and despite IARC’s position with respect to conflicts of interest, one of those most heavily involved in the Monograph 112 process knew what the conclusions would be before it was launched. Christopher Portier, a scientist formerly with EPA, was on the payroll of the Environmental Defense Fund while working on the IARC monograph, without publicly disclosing that fact as required. It gets worse. To make a long and sordid story very short, here it is in Zaruk’s bullets:
- During the same week that IARC had published its opinion on glyphosate’s carcinogenicity, Christopher Portier signed a lucrative contract to be a litigation consultant for two law firms preparing to sue Monsanto on behalf of glyphosate cancer victims.
- This contract has remunerated Portier for at least 160,000 USD (until June, 2017) for initial preparatory work as a litigation consultant (plus travel).
- This contract contained a confidentiality clause restricting Portier from transparently declaring this employment to others he comes in contact with. Further to that, Portier has even stated that he has not been paid a cent for work he’s done on glyphosate.
- It became clear, in emails provided in the deposition, that Portier’s role in the ban-glyphosate movement was crucial. He promised in an email to IARC that he would protect their reputation, the monograph conclusion and handle the BfR and EFSA rejections of IARC’s findings.
- Portier admitted in the deposition that prior to the IARC glyphosate meetings, where he served as the only external expert advisor, he had never worked and had no experience with glyphosate.
In other words, the IARC conclusion rests on a foundation of misrepresentation and lies through which data were tortured to support conclusions they in fact contradict, and vested special interests conspired to drive IARC towards their desired result in secrecy.
Despite IARC’s full throated defense of their corrupt process, critical and credible scientists the world over have not been deceived. The GLP infographic included above documents the rejection of IARC’s classification by regulatory agencies around the world, best encapsulated in the recent Health Canada observation that “No pesticide regulatory authority in the world currently considers glyphosate to be a cancer risk to humans at the levels to which humans are currently exposed.” Perhaps the best summary comes from Robert Tarone:
Those who defend the Monograph 112 Working Group deliberations on glyphosate endorse the selective inclusion of evidence from the studies relied upon by IARC that is interpreted as supporting a claim of carcinogenicity, while simultaneously excluding equally strong, or stronger, exculpatory evidence from the very same studies… The systematic exclusion in Working Group deliberations of exculpatory evidence from the very glyphosate rodent studies relied upon by IARC is inexcusable… When the rodent tumor data from the glyphosate studies relied upon by IARC are properly evaluated, the classification of glyphosate as a probable human carcinogen is not consistent with IARC criteria and should be retracted or revised.
2. What do farmers think about glyphosate?
Farmers love glyphosate. It has allowed them to manage weeds much more easily and effectively than any other weed management measures, and allowed them dramatically to decrease their reliance on tillage. This has been a boon to topsoil conservation efforts, reducing runoff, enhancing retention of soil moisture, organic matter, and carbon sequestration, while dramatically improving the sustainability of production agriculture. All true environmentalists should welcome this innovation.
Farmers around the world have rallied in defense of glyphosate: In the United Kingdom, Germany, New Zealand, France (also here, here, and here), perhaps because they understand the high environmental and economic costs a ban would impose and that the alternative weed control measures would be so much worse. Conservation biologists agree, and toxicologists point out that the most dangerous thing about glyphosate is the van that delivers it. These are the folks who use and rely on glyphosate the most, and are exposed to it far more extensively than any others in society. They have seen the sad results of bans that have been tried in Sri Lanka only to be reversed once reality set in; and the miserable inadequacy of alternatives demonstrated from California to New Zealand. Perhaps they know something juries don’t.
3. Does the claim that glyphosate causes cancer pass the laugh test?
No, it doesn’t. Consider this simple thought experiment. Which members of society face the highest exposure to glyphosate? This is not a trick question—it’s clearly farmers. It’s not kids eating cheerios or oatmeal for breakfast, nor is it backyard gardeners or sidewalk crack weed haters. It’s farmers.
Since biotech improved crops were first introduced on large commercial acreages in 1996, the use of glyphosate has climbed, even as the application rates of many of the older herbicides it displaced plummeted. And even though farmers apply it at very low rates—about a Coke can equivalent per acre—(hardly the “dousing” or “drenching” alleged by opponents)—USDA data show total usage went up dramatically.
Given the indisputable fact that farmers are exposed to orders of magnitude more glyphosate than any other members of society, the cancer rates in farmers should be substantially higher than in other members of the population. Second, farmers’ cancer rates would have risen at a rate similar to the increase in applications of glyphosate illustrated in the figure above, with a lag appropriate to the time between exposure and diagnosis. But we don’t see anything like that at all. In fact, “In this large, prospective cohort study, no association was apparent between glyphosate and any solid tumors or lymphoid malignancies overall, including NHL and its subtypes. There was some evidence of increased risk of AML [acute myeloid leukemia] among the highest exposed group that requires confirmation.” So the bottom line is clear: We have no plausible mechanism for glyphosate to cause cancer; we have no indication of any rise in farmer cancer rates commensurate with the dramatic increase in their use of glyphosate over the past two decades; and thus a complete absence of the dose/response relationship between exposure and disease incidence that is the bedrock of toxicology.
This reality explains, then, why IARC deliberately excluded data that would have led them to a different conclusion; why IARC misrepresented data as supporting their classification of glyphosate as a probable carcinogen when they did not; why they refuse to update and correct their classification in the face of more recent, and far more powerful data. It’s because the data were not cooperating, and they couldn’t reach their preferred result without chicanery.
Then why have two juries now sided with plaintiffs claiming their cancer was caused by glyphosate? Indeed, why do juries so often reach conclusions at odds with data and experience? It looks like what’s known as the Robin Hood Bias, which shows that juries are statistically more likely to rule against wealthy defendants (in this case, a large corporation).
Whereas the Robin Hood Bias is the result of human perception and emotion, the question of glyphosate’s alleged carcinogenicity is a myth debunked by data, experience, and scientific evaluation. Therefore, the result of these misguided jury verdicts should not discourage the use of glyphosate in weedkillers. The data clearly indicate that glyphosate does NOT cause cancer; further, banning it would cripple farmers’ ability to manage weeds and dramatically corrode major environmental gains in agricultural sustainability made over the past generation, while increasing production costs and environmental impacts. This is a scenario that is bad for everyone.