|Action and reaction|
|Spooky scary chemicals|
|Er, who's got the pox?|
Glyphosate is a synthetic herbicide that is widely used in farming, especially since the introduction of strains of crops rendered glyphosate-tolerant via genetic engineering. It's been historically produced by agricultural biotechnical company Monsanto under the trademark "Roundup", although many people conveniently forget or are otherwise unaware that the US patent for glyphosate expired in 2000.
- It's a chemical
- It's synthetic
- It's highly toxic to plants and mildly toxic to certain animals
- It's used in GMO farming
- It was developed by
Yeah, of course it's going to cause woomeisters and conspiracy nutjobs to go into a rage.
Method of action
Glyphosate inhibits the enzyme EPSP synthase, an enzyme needed by plants to make new amino acids. Therefore, glyphosate will mostly harm plants that are actively growing.
Animal biology (including human biology) does not produce the EPSP synthase enzyme, although some bacteria living in an animal's gut can produce it. Therefore, glyphosate's main mechanism of action isn't harmful to animal biology. The very mild toxicity of glyphosate to animals arises from other reasons.
In practice, farmers need a method of controlling weeds. Going through a field picking plants is very labor intensive, and if combined with pesticide use, well, you are exposing farm workers to those pesticides. The conventional method is soil tilling, which involves turning over the soil and killing anything that has grown. This requires tractors and uses up quite a lot of gasoline, plus exposes the field to a slight amount of leaking oil and exhaust from the tractors. The dead weeds decay into methane as well, something worse than carbon dioxide. Agriculture alone is responsible for 10% of the US's anthropogenic greenhouse gas emissions, so anything that reduces tractor use is going to have huge impacts. Similarly, the loose soil is much more likely to be washed away in the rain, causing serious amounts of topsoil erosion. Instead of tilling, herbicides such as glyphosate can be applied to the soil, which results in much less erosion, slightly less fuel use, and by preventing the weeds from growing in the first place, eliminates much of the CO2 produced. In total, glyphosate alone prevents the annual equivalent of 12 million cars. 
Persistency is how long the herbicide lasts before breaking down, and what happens to it before then. Glyphosate binds readily to soil, which has the advantage of not washing away during a rain storm and needing reapplication (and from a public health view, entering a water supply). However, it can enter a water supply if the soil itself washes away via erosion; typically this is exacerbated by poor farming practices (e.g., The Dust Bowl) and in such a scenario, herbicide contamination is one of the least pressing issues. Ironically, the primary cause of topsoil erosion is soil tilling, the very practice that is replaced by herbicide use.
These issues are not unique to glyphosate, nor does necessarily an "organic" herbicide break down faster nor is it less toxic to humans.
The LD50 rating of glyphosate is estimated at 5600 mg/kg, or about 420 ml for a 75 kg human.. While scary sounding, it's actually close to alcohol's LD50 of ~7000 mg/kg. For comparison, the pesticide caffeine has a LD50 rating of 192 mg/kg, making it over twenty times as deadly as glyphosate.
So long as you aren't swapping out the alcohol for glyphosate in your weird farmer-themed Frat House, this isn't ever going to be an issue. Wear gloves and wash your hands after using. As for low level risk exposure, no, not only has there been no link found between glyphosate and the number of issues constantly brought up, it's not even considered a potential risk at this point.
If anything is possibly an issue, it's the other chemicals combined with glyphosate. The rage directed specifically at Glyphosate ignores these other potential problems, because the anti-Glyphosate crowd doesn't actually care about making Glyphosate formulations safer to use.
The WHO and IARC
The World Health Organization's International Agency for Research on Cancer (IARC) currently classifies glyphosate as a Group 2A carcinogen. Group 2A carcinogens are substances that are "probably" carcinogenic to humans, based on sufficient evidence of carcinogenicity in animals but only limited evidence in humans. Other examples of Group 2A carcinogens include fry cooking, glass work, and working as a hairdresser. By contrast, alcohol (ethanol) is a Group 1 carcinogen (a substance that is definitely carcinogenic in humans), yet alcohol continues to be consumed in large amounts by billions of people, including those who strictly prefer to eat organic and non-GMO.
Given that the animal evidence for carcinogenicity of glyphosate was based on high-dose exposures (as is almost always the case), and that human (especially non-worker) exposure is very low, there may never be sufficient evidence of carcinogenicity in humans or for that matter sufficient exposure in humans to observe cancer.
Chronic Kidney Disease of Uncertain Etiology (CKDu) has been reported from multiple locations over the past century, of which anti-GMO activists blame glyphosate as the cause. Maithripala Sirisena, president of Sri Lanka, announced in June 2015 that his country would ban glyphosate in response to the rise in CKDu in order to protect the farmers. In response to President Sirisena's decision, the National Academy of Sciences of Sri Lanka (NASSL) said in a statement: “We are not aware of any scientific evidence from studies in Sri Lanka or abroad showing that CKDu is caused by glyphosate. The very limited information available on glyphosate in Sri Lanka do not show that levels of glyphosate in drinking water in CKDu affected areas (North Central Province) are above the international standards set for safety…Therefore the scientific data is lacking to support the contention that glyphosate is the cause of CKDu in the NCP."
So what are the causes of the reports of CKDu? Contributing factors include heavy metals, plant toxins, infections, and dehydration. Farm employment, pesticide use, alcohol consumption, urinary tract infection, non-steroidal anti-inflammatory medication, low selenium intake, high fluoride intake, volcanic ash exposure, snake bite, hard water, and family history have also been identified as risk factors for CKDu. Causal relationships in CKDu are difficult to untangle as many factors are intimately related (ex- farming, pesticide use, dehydration, and snakebite). Furthermore, disease "clusters" (areas in which more people have a given disease than the average rate) are expected to exist simply because of the way random distributions work.
An oft-repeated claim is that Glyphosate is an endocrine disruptor, which could lead to brain problems in developing fetuses. Both the EPA and the European equivalent have found no endocrine link to Glyphosate itself. There does appear to be a link, not based on the amount of Glyphosate but the formulation.
This seems to be a common thread. Non-Hodgkins Lymphoma, CKD, and Endocrine disruption may likely be caused by weedkillers containing Glyphosate, but not Glyphosate itself. Rather, it's the other ingredients, the surfactants and preservatives, that are the problem. These ingredients are worthy of study, and the focus on Glyphosate is a distraction which prevents society from actually solving the issues.
The internet jumped on glyphosate (above and beyond more than it usually does) after GMO proponent and former Greenpeace member Patrick Moore (not this Patrick Moore) suggested that glyphosate was safe enough to drink, but then refused when offered. Pro-GMO slacktivists countered the ridicule by suggesting that the pro-organic try to say the same thing about organic herbicides—many of which have higher LD50 ratings than glyphosate. One man, Steve "Stu" Burguiere, host of the TV show "Wonderful World of Stu," took the challenge and drank a glass of glyphosate (mixed with other chemicals) to demonstrate how safe the chemical is, and was perfectly fine.
You probably shouldn't drink glyphosate if a stranger offers it to you, because (A) most commercial preparations include surfactants that are more toxic than the glyphosate itself, (B) you probably don't know what the stranger with
candy herbicide has done to it, and (C) it tastes awful (D) deaths have been reported after deliberate overdose.
Notwithstanding that there is an extreme paucity of evidence that the product causes any harm to humans, a California jury ordered new parent company Bayer to pay 289 million dollars in in damages to a groundsman who claimed his cancer was caused by glyphosate. The arguments seem to have been "Well you can't prove it wasn't" and "Monsanto". The award was reduced to 78 million dollars on appeal, but was never overturned.
Emboldened by the success of this
lucrative win poor innocent victim, other lawyers went on to file lawsuits up the yin-yang for cases where glyphosate could be blamed for someone's cancer if you squinted hard enough. The biggest award was for two billion dollars, to a California couple that said Monsanto didn't tell 'em that glyphosate might cause cancer.
In 2016, a joint panel from the WHO and the Food and Agriculture Organization of the UN issued a summary evaluation of glyphosate, concluding that it poses no cancer risks as encountered in food and does not impact our genes. In 2016, the EPA released a report that was one of the most extensive ever undertaken on the herbicide, concluding that glyphosate is “‘not likely to be carcinogenic to humans’ at the doses relevant to human health risk assessment….” The EPA also determined that glyphosate is of “relatively low oral and dermal acute toxicity” and is not carcinogenic as used. A longitudinal epidemiological study on 45,000 pesticide applicators who had used Roundup/glyphosate over many years has found “no association” between glyphosate and NHL.
Scientific consensus firmly remains that glyphosate is a comparatively mild herbicide that poses no harm to the general population from residues in our food and is unlikely to cause cancer in workers who face long term exposure.
There has been talk lately, of the horribly named "superweeds". These are wild plants that have, one way or another, acquired glyphosate resistance. This is indeed a serious economic problem, but it's not like we are at risk of having another kudzu vine crisis. It's important to understand the four F's of biology:
The categories don't have strict boundaries, but it's useful for getting a grasp on biology. Any "spending" in one category comes at a cost. Flee farther and from lesser threats than is required, and the animal has less time and energy left to collect more food. Evolution tends to reward the organisms that best manage their resources. Take the human immune system for example. The vast amount of energy spent on the immune system, which has the potential to suffer a catastrophic breakdown and literally devour you from the inside out. If we magically created a sterile world, those without immune systems would have an overwhelming advantage over those that do, but we have to share this world with E. coli. Much like the immune system, herbicide tolerant plants generally have to use extra energy and materials to survive, often in configurations that would make them weaker, except that the are able to survive in the presence of herbicides whereas non-resistant strains cannot. Glyphosate-resistant strains of soybeans for example produce typically 5% less per acre under ideal conditions. A field full of weeds is the opposite of ideal, and the vast amounts of energy and time (and pollution) needed for other forms of weed control makes this a good deal regardless. This means that in absence of the herbicide, the "superweeds" would be overwhelmed and outcompeted in the wild, and evolution would wipe them out.
The complaint about superweeds contains a logical flaw as well. While similar to the arguments against the overuse of antibiotics resulting in antibiotic resistant "superbug" bacterial strains, the "superbug" issue relies on the debaters' assumption that antibiotics are by themselves a good thing that will become less useful with overuse. Likewise, the "superweed" issue is only a problem if you start with the assumption that herbicides are a good thing, and that overuse will make this good thing less good. If glyphosate was "bad", then surely herbicide resistant plants would be a nonissue, wouldn't it?
A number of claims have been made about glyphosate's supposed "hypertoxicity", in an attempt to undermine the acceptance of the use of herbicide-tolerant crops and GMOs in particular. As mentioned above, no, it's safe so long as you aren't intentionally adding it to your food. It is not known to be carcinogenic to humans, though that doesn't prevent people from repeating canards.
Glyphosate detected in the air
Anti-GMO websites made headlines of glyphosate being detected in the air. This caused a stir, claiming that the glyphosate "poison" was not only in the food but the air we breathe. The websites cited a study by Feng-Chih Chang, Matt F. Simcik, and Paul D. Capel. However, the anti-GMO activists twisted the study's claims and conclusions.
Glyphosate detected in breast milk
On April 7, 2014 a television "documentary" in Australia reported that a study of 10 nursing mother’s milk revealed the presence of glyphosate. This report referenced claims announced made by a "study" commissioned by anti-GMO activist group Moms Across America (MAA) with "Sustainable Pulse", an online "news service" published by anti-GMO campaigner Henry Rowlands. This "news" spread throughout the organic anti-GMO crowd, particularly concerned women.
However, the cited "study" produced by Moms Across America held little to no academic weight. Even MAA noted on their webpage, "The initial testing that has been completed at Microbe Inotech Labs, St. Louis, Missouri, is not meant to be a full scientific study. Instead it was set up to inspire and initiate full peer-reviewed scientific studies on glyphosate, by regulatory bodies and independent scientists worldwide."
The MAA "study" did not match the data produced by US scientists. The samples were so small, and their history of exposure was not revealed. Also, detection depends on the sensitivity of the assay system employed. As more and more sensitive assay techniques are developed, an increasing number of samples can be expected to test positive. But is any small detectable traces of glyphosate still cause for concern? The US Centers for Disease Control and Prevention have noted, "Just because we can detect levels of an environmental chemical in a person's blood or urine does not necessarily mean that the chemical will cause effects or disease."
As it stands, no specific adverse health effect has ever been demonstrated to have been caused by exposure to or low-level consumption of glyphosate. The WHO, EFSA, EPA and other regulatory agencies around the globe have concluded that trace levels of glyphosate in food should be of no more health concern than the presence of myriad potentially toxic chemicals that occur naturally in food.
"GMO farmers douse their fields in RoundUp!"
Whenever one hears about farmers using glyphosate on fields of herbicide-tolerant GM crops, it can conjure up images of drenching the whole field in so much glyphosate you could swim in it.
In truth, farmers use less than 1 liter of glyphosate to treat an entire acre of cropland sown with RoundUp-Ready GM crops. More importantly, this is applied to the ground, instead of directly on the crops themselves. And non-GMO farmers use similarly small amounts.
- Is glyphosate (Roundup) dangerous? — Genetic Literacy Project
- Top Concerns About Glyphosate Include Birth Defects and Cancer — GMO Science
- Glyphosate and Cancer: What does the data say? — Andrew Kniss from Weed Control Freaks
- Debunking pseudo science “lab testing” health risk claims about glyphosate (Roundup) — Academics Review
- So Roundup “probably” causes cancer. This means what, exactly? — Grist
- In a Nutshell
- from the EPA
- from NIH
- Effects of glyphosate-resistant crop cultivation on soil and water quality
- "Is glyphosate, used with some GM crops, dangerously toxic to humans?", Genetic Literacy Project, invoking Betteridge's law of headlines
- Effects of Surfactants on the Toxicitiy of Glyphosate, with Specific Reference to RODEO, Fed
- Peer review of the pesticide risk assessment of the potential endocrine disrupting properties of glyphosate
- Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines, NIH
- Patrick Moore, Man Who Refused to Drink Roundup, is Not a Monsanto Lobbyist, Newsweek, 27-March-2015
- "Pathological and toxicological findings in glyphosate-surfactant herbicide fatality: a case report". The American Journal of Forensic Medicine and Pathology 33 (3): 234–37. Sep 2012. doi:10.1097/PAF.0b013e31824b936c. PMID 22835958.
- "Glyphosate poisoning". Toxicological Reviews 23 (3): 159–67. 2004. doi:10.2165/00139709-200423030-00003. PMID 15862083.
- Cancer, Juries, and Scientific Certainty: The Monsanto Roundup Ruling Explained: Juries sometimes render verdicts on scientific questions, but that doesn’t mean their verdict is always accepted by the scientific community at large. by Alex Kasprak (17 August 2018) Snopes.
- Sullivan, Emily. "Groundskeeper Accepts Reduced $78 Million Award In Monsanto Cancer Suit". NPR.
- "Bayer's $2 Billion Roundup Damages Boost Pressure to Settle". bloomberg.com.
- JOINT FAO/WHO MEETING ON PESTICIDE RESIDUES from the World Health Organisation
- Elmore et al., Glyphosate-Resistant Soybean Cultivar Yields Compared with Sister Lines, Agronomy Journal, Vol. 93 No. 2, p. 408-412
- Case studies: A hard look at GM crops, Nature news, 1-May-2013
- Chronological Increase in Resistant Weeds Globally, International Survey of Herbicide Resistant Weeds, retrieved 12-Sept-2015
- Glyphosate Toxnet, National Library of Medicine (archived from May, 2017).
- Feng-Chih Chang, Matt F. Simcik, and Paul D. Capel, “Occurrence and Fate of the Herbicide Glyphosate and Its Degradate Aminomethylphosphonic Acid in the Atmosphere,” Environmental Toxicology and Chemistry, Vol. 30, No. 3, pp. 548–555, 2011
- U.N. experts find weed killer glyphosate unlikely to cause cancer
- How Much Roundup Do Farmers Actually Use?, Southeast Saskatchewan Farmer blog, 22-May-2016
- Farm Babe: No, wheat isn’t drenched in glyphosate, Ag Daily, 12-march-2019