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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, and has 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 most 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.
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 main cause of topsoil erosion, soil tilling, is reduced with the application of herbicides such as glyphosate.
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, this is only slightly more dangerous than alcohol's ~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 using glyphosate as the main ingredient in your potato salad, this isn't an issue. (Wear gloves and wash your hands.) 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.
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).
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.
Notwithstanding that there is little only limited that the product causes cancer in 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".
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:
All organisms need to manage their resources. Any resources spent in one category are resources that are unavailable in another category. Herbicide tolerant plants generally have to spend extra energy to survive, in much the same way your immune system uses up vast amounts of energy. Glyphosate-resistant strains of soybeans for example produce typically 5% less per acre under ideal conditions. It should be noted, though, that 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.
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.
- 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
- Patrick Moore, Man Who Refused to Drink Roundup, is Not a Monsanto Lobbyist, Newsweek, 27-March-2015
- 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.
- 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
- 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