Definition Terminology Causes Ambiguous Determinations
Both “probably” and “possibly” are very ambiguous adverbs in the English dictionary. Neither word is definitive, and they may not trigger much of a reaction from an audience. Yet at other times, both words can erroneously be construed as conclusive and decisive.
A great example of this is when Tom Brady of the New England Patriots was suspended for deflating footballs. The NFL disciplined the New England Patriots based on a report that stated it was “more probable than not” that they were aware of the rules infraction. Obviously it was not an overwhelming preponderance of evidence against the Patriots, and the lack of conclusive evidence was a factor in the court’s decision to vacate Tom Brady’s suspension. Yet, still in the minds of most critics, the Patriots cheated.
Recently, these adverbs have been a topic of discussion in weed management. This past spring, the International Agency for Research on Cancer (IARC), a branch of the World Health Organization (WHO), categorized glyphosate, commonly referred to as Roundup, as a Group 2A carcinogen. To the IARC this classification means glyphosate is “probably carcinogenic to humans.” This was followed by the IARC re-evaluation and confirmation of their 1987 decision to categorize the herbicide 2,4-dicholorphenoxyacetic acid (2,4-D) as a Group 2B carcinogen, meaning the IARC believes 2,4-D is “possibly carcinogenic to humans.”
These classifications can be rather concerning to Wyoming agriculture. Both glyphosate and 2,4-D play a critical role in the management of noxious weeds in crops and rangelands. Of all herbicides, glyphosate currently has the highest global production volume. For Wyoming weed and pest control districts, glyphosate plays a critical role in noxious weed programs, including early spring applications to cheatgrass.
Like glyphosate, 2,4-D has also been a reliable tool in most weed management toolboxes. Since its introduction as a herbicide in 1945, it quickly became the primary herbicide for agricultural and residential weed control. Along with glyphosate, weed and pest control districts still utilize 2,4-D on broadleaf and annual weeds.
Therefore, maybe we should simply be happy the IARC did not label either herbicide in Group 1 – Carcinogenic to Humans. Group 1 agents include the likes of asbestos, arsenic and plutonium, in addition to processed meats, boot and shoe repair and the manufacturing of wooden furniture. Alternatively, it’s unfortunate that neither herbicide was categorized in Group 3 – Not Classifiable as to its Carcinogenicity to Humans, or better yet under Group 4 – Probably Not Carcinogenic to Humans, where the compound caprolactam has the dubious honor of being the only agent the IARC can definitively say “probably not” a carcinogen.
Group 2A – Probably Carcinogenic to Humans and Group 2B – Possibly Carcinogenic to Humans seem rather redundant, given both seem to be inconclusive. To clarify the difference between the two categories, when IARC labeled glyphosate as 2A – Probably Carginogenic they based the decision on “limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals.” Compare this to 2,4-D, which they labeled as a 2B – Possibly Carcinogenic due to “inadequate evidence in humans and limited evidence in experimental animals.”
Maybe to get an even better understanding of the differences between Group 2A – Probably Carginogenic and Group 2B – Possibly Carginogenic, we should look at examples of other agents categorized in each group.
Group 2A – Probably Carginogenic includes the insecticides diazinon and malathion, but it also includes red meat, the occupational exposures of a hairdresser and shift work that involves circadian disruption. Therefore, non-vegetarian barbers who work a nightshift are probably exposing themselves to multiple carcinogens. As for Group 2B – Possibly Carginogenic, the pesticides DDT and chlordane are listed, in addition to coffee, pickled vegetables, electromagnetic fields associated with cell phones and carpentry.
Maybe we should narrow our focus on the IARC findings concerning glyphosate and 2,4-D. However, it should be noted the IARC doesn’t do the research in their analysis. Instead they rely on previously published literature. According to the IARC press release for glyphosate, their primary defense of the 2B – Probable categorization was “limited” evidence of non-Hodgkin lymphoma in humans and convincing evidence it causes cancer in laboratory animals. For 2,4-D, their review determined “inadequate” evidence of a carcinogen in humans and “limited” evidence in laboratory animals.
As it relates to glyphosate, the scientific community has found the data used by IARC to make these assertions concerning. The Academics Review, a group of experts from around the world who separate falsehoods from peer-reviewed science, gave the IARC report on glyphosate an “F.” Of particular note to them was the IARC’s utilization of the discredited and controversial Gilles-Eric Seralini study that ties genetically modified corn to a high incidence of cancer. The Seranlini study was initially published in Food and Chemical Toxicology, only to have the publication’s editor expunge it from their database due to overwhelming scrutiny from the scientific community. A published review of the Seranlini study in the Transgenic Review went as far as to say, “The study appeared to sweep aside all known benchmarks of scientific good practice and, more importantly, to ignore the minimal standards of scientific and ethical conduct…”
Additionally, the Academics Review graded the IARC poorly for not considering glyphosate at doses consumers would normally be exposed. As explained by Henry Miller, contributor to Forbes magazine, in his assessment of the IARC analysis, “As with common chemicals like sugar, salt and water, and foods like nutmeg and licorice, glyphosate at very high doses is capable of causing harm to humans. That’s what the IARC ‘2A’ essentially means.”
In other words, as Miller explained, “IARC bases its conclusion on potential hazard rather than the actual risk of harm.” This method of analysis is completely opposite of what regulatory agencies, such as the Environmental Protection Agency (EPA), use when completing their risk assessments of pesticides.
In fact, the EPA and other regulating bodies, such as the European Food Safety Authority (EFSA), have done thorough reviews of the carcinogenic hazard associated with glyphosate. The EPA concluded that current research “does not provide evidence to show that glyphosate causes cancer.” EFSA, which has more stringent standards than the EPA, concluded glyphosate was unlikely to pose a carcinogenic threat to humans.
The same can be said concerning 2,4-D. In 2008 Canada’s Pest Management Regulatory Agency conducted what is considered the most thorough evaluation of 2,4-D data and concluded, “…2,4-D does not increase the risk of cancer and can be used safely by homeowners, provided label directions are followed.” An EPA review of 2,4-D concluded there was no epidemiological evidence to link 2,4-D as a cause of cancer. That is fairly conclusive, especially since 2,4-D has been the most extensively researched pesticide since its introduction.
With as much ambiguity and conjecture involved in the IARC classifications, its unfortunate the amount of credence given to it by agenda-driven individuals and groups. In fact, much like Tom Brady cynics, some of the groups are determined to take ambiguity out of “probably” and “possibly” and make these adverbs more definitive, like “absolute” or “irrefutable.” Internet petitions to ban the use of glyphosate have popped up citing the IARC classification as justification. California has moved to label glyphosate as a carcinogen under the state’s Proposition 65, which requires the state to identify known carcinogenic chemicals including all agents identified by IARC. Within six months of the IARC press release, at least two lawsuits were filed against Monsanto blaming the manufacturer for cancer related to glyphosate exposure.
Not long ago, while visiting family in Montana, my wife and I took a walk through my sister-in-law’s pasture. The pasture follows the Bitterroot River and abuts a small housing development. Being the good neighbors they are, my wife’s sister and her husband allow the neighborhood to access the river for fishing by walking through their pasture.
On this particular day, my wife and I met one of those neighbors. She had just picked a weed in the field and asked us if we knew anything about it. I quickly replied that it was wild licorice and, without hesitation, started naming off potential herbicide treatments, including 2,4-D. She responded with a disgusted look and informed me she was on a regional board for a coalition opposed to the use of pesticides. She then proceeded to lecture me on how the World Health Organization has branded 2,4-D as a carcinogen and that their findings conclusively proved what her coalition has known all along. Based on this new evidence she believed a ban of 2,4-D in the United States was a matter of time. For my sister-in-law’s sake, in addition to recognizing the stern look from my wife, I chose not to question her understanding of the IARC report. As she walked away I couldn’t help but wonder if she possibly had an opinion on deflated footballs, cell phones and pickles – and whatever it is, it would probably be very fascinating.