Glyphosate (N-phosphonomethyl glycine , C 3 H 8 NO 5 P, CAS 1071-83-6) is a broad-spectrum, non-selective herbicide developed for the elimination of weeds and shrubs, especially perennials. It is a total herbicide. It is absorbed by the leaves and not the roots . It can be applied to the leaves, injected into trunks and stems , or sprayed on stumps as a forestry herbicide.
The application of glyphosate kills plants because it suppresses their ability to generate aromatic amino acids.
Glyphosate is the active ingredient in the herbicide Roundup ( Monsanto ‘s trade name ) (its patent expired in 2000 ). Monsanto has patented in some countries the “40-3-2” phenomenon in soybeans, which confers resistance to glyphosate . Glyphosate-resistant plants have been obtained through transgenesis.
It is the most widely used herbicide in the US, with 2,000-4,000 t /year used on lawns and 40,000-50,000 t/year used in agriculture.
Chemistry
Glyphosate is an aminophosphonate and an analogue of the naturally occurring amino acid glycine . The name is a contraction of glycine , phospho – and -ate , a particle designating the conjugate base of an acid .
Its herbicidal activity was discovered in 1970 by John E. Franz , working at Monsanto .
Biochemistry
Glyphosate acts by inhibiting 5-enolpyruvyl-shikimate-3-phosphate synthetase (EPSPS), the enzyme responsible for the formation of the aromatic amino acids phenylalanine , tyrosine and tryptophan .
Shikimate (shikimic acid anion) is the key and common precursor in the biosynthesis of all aromatic amino acids and tryptophan resulting from the cyclization of a heptonic acid.
EPSPS catalyzes the reaction between shikimate-3-phosphate (S3P) and phosphoenolpyruvate (PEP) to form ESP and phosphate. Aromatic amino acids are also used to form secondary metabolites such as folates , ubiquinones , and naphthokines . The shikimate biochemical pathway is not found in animals.
It is also used in the fight against poppy , coca and other plants used in the development of narcotics . It is also used as a herbicide in soybean crops, which have been genetically modified to not be affected by this substance.
Formulas and registered names
Although the trademark Roundup still exists on file with the [[US Patent Office]], the patent has already expired. Thus, glyphosate is sold in the US and worldwide in different solutions under many registered names: Roundup, Buccaneer, Razor Pro (41%), Genesis Extra II (41% + surfactant), Roundup® Pro Concentrate (50.2%), Rodeo (51.2%), Aquaneat (53.8%), Aquamaster (53.5%). Such products may contain other ingredients, causing different effects. For example, Roundup has additive effects to glyphosate itself, as it is an aqueous solution of glyphosate, a surfactant and other substances.
Glyphosate is supplied in several formulations for different uses:
- Ammonium salt
- Isopropyl amine salt
- Glyphosate acid – standalone, either as ammonium salt or isopropyl salt
- Potassium salt
Products can be formulated with 120, 240, 360, 480, 680 g of active ingredient per litre. The most common formulation in agriculture is 360 g/ L , either alone or with cationic surfactants.
For 360 g /L formulations , European regulations allow field applications of up to 12 L / ha for control of perennial weeds (such as Elytrigia repens ). Most commonly used is no more than 3 L/ha for usual annual weed control between crops.
Other uses
The spraying of illicit crops with glyphosate has a negative environmental impact on the Colombian jungle, in addition to the deforestation caused by illegal groups.
Glyphosate is one of the herbicides used by the US government to spray coca fields in Colombia under Plan Colombia . Its effects on human health, the environment, legal crops, and effectiveness in combating the US war on drugs are widely disputed.
There are already reports that such extensive aerial applications of glyphosate in its attempt to destroy coca crops in South America resulted in the natural development of glyphosate-resistant strains of coca known as Boliviana negra , which have been improved through selection . Although there are no scientific reports of glyphosate-resistant coca in the peer-reviewed literature, since herbicide spraying is prohibited in Colombian national parks, coca is grown within these areas, cutting down natural vegetation, and establishing illegal coca plantations.
Genetically modified crops
Some microorganisms have a version of 5-enolpyruvyl-shikimate-3-phosphate synthetase (EPSPS) that is resistant to inhibition by glyphosate. The version used in genetically engineered crops was isolated from the glyphosate-resistant strain of Agrobacterium CP4 (CP4 EPSPS). This CP4 EPSPS gene was cloned and transfected into soybeans , and commercialization of transgenic soybeans began in 1996 .
Toxicity and undesirable effects
The Environmental Protection Agency (EPA) classified glyphosate herbicides as mildly toxic in “Class III” for oral and inhalation exposure, but recent studies suggest that IV may be more appropriate for oral, dermal, and inhalation exposure. However, it remains in Class I (severe) for ocular exposure. The 2000 review concluded that “under present and expected conditions of use, there is no potential for the herbicide Roundup to pose a health risk to humans.”
However, a recent study has shown that Roundup formulations and metabolic products cause the death of human embryos, placentas, and umbilical cord cells in vitro even at low concentrations (1 x 10 -5 times the recommended concentration for use). The effects are not proportional to the concentrations of glyphosate but depend on the nature of the adjuvants used in the formulation. The glyphosate degradation byproduct AMPA and the main adjuvant POEA separately and synergistically damage cell membranes like RoundUp but at different concentrations. Their mixtures with glyphosate would be even more harmful according to this study.
Inactivated Glyphosate
Glyphosate, like many modern agricultural inputs, are active ingredients that are inactivated when they come into contact with calcium and/or magnesium present in soil and water, and therefore lose their effect on vegetation. However, the truth is that this inactivated product damages the soil surface and contaminates the water table when it penetrates the soil through the action of water. This inactivation capacity has an undesirable effect on the environment but is very beneficial for the companies that produce this drug; this effect lies in the fact that when the product comes into contact with water (which contains calcium and magnesium in different proportions depending on the region), it loses its weed control capacity by 5 to 10%, which is offset by a higher use of the product in the same proportion.
Scientific fraud
On two occasions the U.S. Environmental Protection Agency has found scientists deliberately falsifying test results at research labs contracted by Monsanto to study the effects of glyphosate. In the first incident involving “Industry Biotest Laboratories,” an EPA reviewer stated after the investigation into “routine data falsification” that it was “hard to believe the scientific integrity of the studies when they say they took samples from the uteruses of male rabbits.” In the second incident involving falsifying results, which occurred in 1991, the owner of the lab (Craven Labs) and three employees were indicted on 20 counts; the owner was sentenced to 5 years in prison and fined $50,000, the lab was fined $15.5 million and ordered to pay $3.7 million in restitution. Craven Labs had conducted studies for 262 companies, including Monsanto’s pesticides.
Misleading advertising
In 1996, Monsanto was accused of false and misleading advertising of glyphosate-derived products, leading to a lawsuit filed by the New York State Attorney General.
On January 20, 2007 , Monsanto was found guilty of false advertising for representing Roundup as biodegradable and claiming that soil remained clean after use.
Environmental and consumer rights activists brought the case in 2001 on the grounds that glyphosate, the main ingredient in Roundup, is classified by the European Union as “dangerous for the environment” and “toxic to aquatic organisms.” Monsanto France plans to appeal the verdict.
Debate on endocrinological effects
In vitro studies have shown that glyphosate affects progesterone production in mammalian cells and may increase placental cell mortality. Whether these studies allow glyphosate to be classified as an endocrine disruptor is a matter of debate.
Some consider in vitro studies to be insufficient, and are waiting to see if animal studies show a change in endocrine activity, since a change in a single cell line cannot necessarily occur in an entire organism. Furthermore, it is argued that current in vitro studies expose cell lines to concentrations orders of magnitude higher than those found in real-world conditions, and through mechanisms they would not experience in reality.
Others believe that in vitro studies, particularly those that identify not only the effect but also the chemical pathway, are sufficient evidence to classify glyphosate as an endocrine disruptor, on the basis that even small changes in endocrine activity can have long-lasting effects on an entire organism that may be difficult to detect through whole-organism studies alone. Further research on the topic is planned, and should shed more light on the debate.
Controversies over glyphosate
Argentina
On January 19, 2009 , the President of the Argentine Republic, Cristina Fernández de Kirchner , issued Decree 21/2009 through which she created the National Research Commission, which will operate within the orbit and with headquarters in the Ministry of Health, and has the following objectives:
1- Investigate the reported events and similar situations, their causes and effects. 2- Make recommendations, propose actions, plans, programs, etc. 3- Outline guidelines to contribute to the rational use of chemicals and agrochemicals. 4- Propose appropriate information tools for use in the media. 5- Identify general problems in the health care of the affected population. 6- Develop care strategies to promote the rational use of products or their elimination. 7- Gather statistical information and impact indicators. 8- Promote the relevant regulations and propose direct actions to be implemented. 9- Propose awareness and education campaigns on the use and handling of chemicals and agrochemicals. 10- Implement, execute and/or coordinate actions, plans, projects and programs. 11- Carry out all actions entrusted to it by the Presidency of the Commission.
Decree 21/09, in its recitals, makes special mention of the Ituzaingó Anexo Neighborhood, an emblematic case of contamination due to glyphosate fumigation in urban and peri-urban areas.
As a result, on April 15, 2009 , the Argentine Association of Environmental Lawyers filed an appeal for protection before the Supreme Court of Justice of the Nation, where it requested a series of measures to protect the environment and the health of the national population in view of the very serious and widespread consequences for ecosystems and the population due to the use of this agrotoxic, invoking the precautionary principle of environmental law. The defendants were the National State and the provinces of Buenos Aires , Córdoba and Santa Fe . The company Monsanto, the main marketer of the glyphosate-based herbicide, is cited as an “interested third party”.
In April 2009 , Argentine media reported that a paper by Andrés Carrasco, Undersecretary of Scientific and Technological Research at the Ministry of Defense, indicated that glyphosate can cause neuronal, intestinal, and cardiac malformations in human embryos. In addition to his role at the Ministry of Defense, Andrés Carrasco is a researcher at CONICET (Argentine National Scientific and Technical Research Council). However, the paper has not been published in a peer-reviewed academic journal , so its content has not been scrutinized by the scientific community .
The confrontation with the Minister of Science and Technology, Lino Barañao , who publicly came out to discredit Dr. Carrasco’s investigations is evident. After this, the National Federation of University Teachers (CONADU) expressed solidarity and accompanied the researcher “who in recent days has been the victim of a campaign of defamation and threats after he announced the results of an investigation.”
For the National Service for Food Safety and Quality (Senasa), the herbicide complies with all regulations, and although it has requested Andrés Carrasco’s report for evaluation, it has not yet received any response. The chambers of the agricultural sector attribute the situation to a smear campaign promoted by the Executive Branch, following its confrontation with the agricultural sector over the withholdings on soybean exports.
The Ministry of Defense of the Argentine Republic has banned the planting of soybeans on some of its lands. The ban has been attributed to the Carrasco report, although prior to it, a journalistic investigative report denounced 8,000 hectares of soybeans planted on land belonging to the Armed Forces, leaving the Executive in a weak argumentative position in its campaign against the massive planting of the oilseed.
Traces of glyphosate found in soybeans
Research groups from the National University of Litoral found toxic substances in mature and green soybeans, as well as in the soil used for planting, which causes contamination of the groundwater. Also, a study carried out in 2001 showed that there were traces of glyphosate and endosulfan in green soybeans. The food products obtained from these grains, which were initially presented as “the ideal food”, are now questioned in the scientific field due to their high degree of exposure to pesticides.