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Roundup
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Roundup is the brand name of a systemic, broad-spectrum herbicide produced by the U.S. company Monsanto and contains the active ingredient glyphosate. Glyphosate is the most used herbicide in the USA.[ US EPA 2000–2001 Pesticide Market Estimates , ] In the US, 5-8 million pounds are used every year on lawns and yards and 85-90 million pounds are used annually in US agriculture.
Monsanto developed and patented the glyphosate molecule in the 1970s, and marketed Roundup from 1973.
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Encyclopedia
Roundup is the brand name of a systemic, broad-spectrum herbicide produced by the U.S. company Monsanto and contains the active ingredient glyphosate. Glyphosate is the most used herbicide in the USA.[ US EPA 2000–2001 Pesticide Market Estimates , ] In the US, 5-8 million pounds are used every year on lawns and yards and 85-90 million pounds are used annually in US agriculture.
Monsanto developed and patented the glyphosate molecule in the 1970s, and marketed Roundup from 1973. It retained exclusive rights in the US until its US patent expired in September, 2000, and maintained a predominant marketshare in countries where the patent expired earlier.
The active ingredient of Roundup is the isopropylamine salt of glyphosate. Glyphosate's mode of action is to inhibit an enzyme involved in the synthesis of the amino acids tyrosine, tryptophan and phenylalanine. It is absorbed through foliage and translocated to growing points. Because of this mode of action, it is only effective on actively growing plants; it is not effective as a pre-emergence herbicide.
Monsanto also produces seeds which grow into plants genetically engineered to be tolerant to glyphosate which are known as Roundup Ready crops. The genes contained in these seeds are patented. Such crops allow farmers to use glyphosate as a post-emergence herbicide against both broadleaf and cereal weeds. Soy was the first Roundup Ready crop and was produced at Monsanto's Agracetus Campus located in Middleton, Wisconsin.
Chemistry
Roundup is not one substance, but a water based solution containing an herbicide called glyphosate, a sufactant, and other substances.
Glyphosate is an aminophosphonic analogue of the natural amino acid glycine and the name is a contraction of glycine, phospho- and -ate. There are several dissociable hydrogens, especially the first hydrogen of the phosphate group. The molecule tends to exist as a zwitterion where a phosphonic hydrogen is bonded to the amine group. Glyphosate is found in Roundup as one of several salts. While glyphosate is soluble in water to 12g/L at room temperature, the salts are highly soluble.
Glyphosate was first discovered to have herbicidal activity in 1970 by John E. Franz, a scientist who worked for the Monsanto company. Franz received the National Medal of Technology in 1987 for his discoveries and in 1990 received the Perkin Medal for Applied Chemistry.
Biochemistry
Glyphosate kills plants by inhibiting the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which catalyzes the reaction of shikimate-3-phosphate (S3P) and phosphoenolpyruvate to form 5-enolpyruvyl-shikimate-3-phosphate (ESP). ESP is subsequently dephosphorylated to chorismate, which is an essential precursor in plants for the aromatic amino acids: phenylalanine, tyrosine and tryptophan. These amino acids are used as building blocks in peptides and to produce secondary metabolites such as folates, ubiquinones and naphthoquinone. X-ray crystallographic studies of Glyphosate and EPSPS shows that glyphosate functions by occupying the binding site of the phosphoenol pyruvate, mimicking an intermediate state of the ternary enzyme substrates complex. The shikimate pathway is not present in animals, which obtain aromatic amino acids from their diet. Glyphosate has also been shown to inhibit other plant enzymes and also has been found to affect animal enzymes.
Health, ecological concerns and controversy
Roundup has a United States Environmental Protection Agency? (EPA) Toxicity Class of III for oral and inhalation exposure, but more recent studies suggest that IV is appropriate for oral, dermal, and inhalation exposure. It has been rated as class I (Severe) for eye irritation, however.
A 2000 review of the available literature concluded that "under present and expected conditions of new use, there is no potential for Roundup herbicide to pose a health risk to humans". A recent study, on the other hand, has shown that Roundup formulations and metabolic products cause the death of human embryonic, placental, and umbilical cells in vitro even at low concentrations. The effects are not proportional to Glyphosate concentrations but dependent on the nature of the adjuvants used in the formulation.
False advertising
In 1996 Monsanto was accused of false and misleading advertising of glyphosate products, prompting a law suit by the New York State attorney general.
On Fri Jan 20, 2007, Monsanto was convicted of false advertising of Roundup for presenting Roundup as biodegradable and claiming that it left the soil clean after use.
Environmental and consumer rights campaigners brought the case in 2001 on the basis that glyphosate, Roundup's main ingredient, is classed as "dangerous for the environment" and "toxic for aquatic organisms" by the European Union.
Monsanto France planned to appeal the verdict at the time.
Scientific fraud
On two occasions the United States Environmental Protection Agency has caught scientists deliberately falsifying test results at research laboratories hired by Monsanto to study glyphosate. In the first incident involving Industrial Biotest Laboratories, an EPA reviewer stated after finding "routine falsification of data" that it was "hard to believe the scientific integrity of the studies when they said they took specimens of the uterus from male rabbits". In the second incident of falsifying test results in 1991, the owner of the lab (Craven Labs), and three employees were indicted on 20 felony counts, the owner was sentenced to 5 years in prison and fined 50,000 dollars, the lab was fined 15.5 million dollars and ordered to pay 3.7 million in restitution. Craven laboratories performed studies for 262 pesticide companies including Monsanto.
Monsanto has stated that the studies have been repeated and that Roundup's EPA certification does not now use any studies from Craven Labs or IBT. Monsanto also claims that the Craven Labs investigation was started by the EPA after a pesticide industry task force discovered irregularities.
Human and mammalian toxicity
Glyphosate itself is practically nontoxic by ingestion or by skin contact. The acute oral toxicity of Roundup is > 5,000 mg/kg in the rat. It showed no toxic effects when fed to animals for 2 years, and only produced rare cases of reproductive effects when fed in extremely large doses to rodents and dogs. It has not demonstrated any increase in cancer rates in animal studies and is poorly absorbed in the digestive tract. Glyphosate has no significant potential to accumulate in animal tissue.
Not only is glyphosate used as five different salts but commercial formulations of it contain surfactants, which vary in nature and concentration. As a result, human poisoning with this herbicide is not with the active ingredient alone but with complex and variable mixtures.
A review of the toxicological data on Roundup shows that there are at least 58 studies of the effects of Roundup itself on a range of organisms. This review concluded that "for terrestrial uses of Roundup minimal acute and chronic risk was predicted for potentially exposed nontarget organisms". It also concluded that there were some risks to aquatic organisms exposed to Roundup in shallow water. More recent research suggests glyphosate induces a variety of functional abnormalities in fetuses and pregnant rats. Also in recent mammalian research, glyphosate has been found to interfere with an enzyme involved testosterone production in mouse cell culture and to interfere with an estrogen biosynthesis enzyme in cultures of Human Placental cells.
The United States Environmental Protection Agency, the EC Health and Consumer Protection Directorate, and the UN World Health Organization have all concluded that pure glyphosate is not carcinogenic. Opponents of glyphosate claim that Roundup has been found to cause genetic damage, citing Peluso et al. The authors concluded that the damage was "not related to the active ingredient, but to another component of the herbicide mixture".
There is a reasonable correlation between the amount of Roundup ingested and the likelihood of serious systemic sequelae or death. Ingestion of >85 mL of the concentrated formulation is likely to cause significant toxicity in adults. Gastrointestinal corrosive effects, with mouth, throat and epigastric pain and dysphagia are common. Renal and hepatic impairment are also frequent and usually reflect reduced organ perfusion. Respiratory distress, impaired consciousness, pulmonary oedema, infiltration on chest x-ray, shock, arrythmias, renal failure requiring haemodialysis, metabolic acidosis and hyperkalaemia may supervene in severe cases. Bradycardia and ventricular arrhythmias are often present pre-terminally. Dermal exposure to ready-to-use glyphosate formulations can cause irritation and photo-contact dermatitis has been reported occasionally; these effects are probably due to the preservative Proxel (benzisothiazolin-3-one). Severe skin burns are very rare. Inhalation is a minor route of exposure but spray mist may cause oral or nasal discomfort, an unpleasant taste in the mouth, tingling and throat irritation. Eye exposure may lead to mild conjunctivitis, and superficial corneal injury is possible if irrigation is delayed or inadequate.
Aquatic effects
Fish and aquatic invertebrates are more sensitive to Roundup than terrestrial organisms. Glyphosate is generally less persistent in water than in soil, with 12 to 60 day persistence observed in Canadian pond water, yet persistence of over a year have been observed in the sediments of ponds in Michigan and Oregon.
The EU classifies Roundup as R51/53 Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment.
Roundup is not registered for aquatic uses and studies of its effects on amphibians indicate it is toxic to them. Glyphosate formulations that are registered for aquatic use have been found to have negligible adverse effects on sensitive amphibians.
Environmental degradation and effects
When glyphosate comes into contact with the soil it can be rapidly bound to soil particles and be inactivated. Unbound glyphosate can be degraded by bacteria. Glyphosphate has been shown to increase the infection rate of wheat by fusarium head blight in fields that have been treated with glyphosphate.
In soils, half lives vary from as little as 3 days at a site in Texas, 141 days at a site in Iowa, to between 1–3 years in Swedish forest soils. It appears that higher latitude sites have the longest soil persistences such as in Canada and Scandinavia.
A recent study concluded that certain amphibians may be at risk from glyphosate use. One study has shown an effect on growth and survival of earthworms. The results of this study are in conflict with other data and has been criticized on methodological grounds. In other studies nitrogen fixing bacteria have been impaired, and also crop plant susceptibility to disease has been increased.
Endocrine disruptor debate
An in-vitro study has suggested glyphosate may have an effect on progesterone production in mammalian cells and affect mortality of placental cells in-vitro. Whether these studies classify glyphosate as an endocrine disruptor is a matter of debate.
Some believe that in-vitro studies are insufficient, and are waiting to see if animal studies show a change in endocrine activity, since a change in a single cell line may not occur in an entire organism. Additionally, current in-vitro studies expose cell lines to concentrations orders of magnitude greater than would be found in real conditions, and through pathways that would not be experienced in real organism.
Others believe that in-vitro studies, particularly ones identifying not only an effect, but a chemical pathway, are sufficient evidence to classify glyphosate as an endocrine disruptor, on the basis that even small changes in endocrine activity can have lasting effects on an entire organism that may be difficult to detect through whole organism studies alone. Further research on the topic has been planned.
Glyphosate resistance in weeds and microorganisms
The first documented cases of weed resistance to glyphosate were found in Australia, involving rigid ryegrass near Orange, New South Wales. Some farmers in the United States have expressed concern that weeds are now developing with glyphosate resistance, with 13 states now reporting resistance, and this poses a problem to many farmers, including cotton farmers, that are now heavily dependent on glyphosate to control weeds. Farmers associations are now reporting 103 biotypes of weeds within 63 weed species with herbicide resistance, and this will continue to grow as a problem.
Some microorganisms have a version of 5-enolpyruvoyl-shikimate-3-phosphate synthetase (EPSPS) that is resistant to glyphosate inhibition. The version used in genetically modified crops was isolated from Agrobacterium strain CP4 (CP4 EPSPS) that was resistant to glyphosate. The CP4 EPSPS gene was cloned and inserted into soybeans. The CP4 EPSPS gene was engineered for plant expression by fusing the 5' end of the gene to a chloroplast transit peptide derived from the petunia EPSPS. This transit peptide was used because it had shown previously an ability to deliver bacterial EPSPS to the chloroplasts of other plants. The plasmid used to move the gene into soybeans was PV-GMGTO4. It contained three bacterial genes, two PC4 EPSPS genes, and a gene encoding beta-glucuronidase (GUS) from Escherichia coli as a marker. The DNA was injected into the soybeans using the particle acceleration method. Soybean cultivar A54O3 was used for the transformation. The expression of the GUS gene was used as the initial evidence of transformation. GUS expression was detected by a staining method in which the GUS enzyme converts a substrate into a blue precipitate. Those plants that showed GUS expression were then taken and sprayed with glyphosate and their tolerance was tested over many generations.
Genetically modified crops
In 1996, genetically modified Roundup Ready soybeans resistant to Roundup became commercially available, followed by Roundup Ready corn in 1998. Current Roundup Ready crops include soy, maize (corn), sorghum, canola, alfalfa, and cotton, with wheat still under development. These cultivars greatly improved conventional farmers' ability to control weeds since glyphosate could be sprayed on fields without hurting the crop. As of 2005, 87% of U.S. soybean fields were planted to glyphosate resistant varieties.
The use of roundup ready crops has changed the herbicide use profile away from atrazine, metribuzin, and alachlor. This has the benefit of reducing the dangers of herbicide run off into drinking water. The use of roundup-ready crops has resulted in greater use of roundup, which has created a problem with weeds that are resistant to the herbicide. With greater use, it has become more likely that weeds not affected by the herbicide survive, reproduce and proliferate.
Tradenames
The Roundup trademark is registered with the US Patent Office and still extant. However, the chemical formulation is no longer under patent, so similar products using glyphosate as the active ingredient are available from other manufacturers and marketed under many names, including Buccaneer, Razor Pro, (41%), Roundup Pro Concentrate (50.2 %), Rodeo (51.2%), Aquaneat
(53.8%), and Aquamaster (53.5%)
Other uses
Glyphosate is one of a number of herbicides used by the United States government to spray Colombian coca fields through Plan Colombia. There are reports that widespread application of glyphosate in attempts to destroy coca crops in South America have resulted in the development of glyphosate-resistant strains of coca known as Boliviana negra, which have been selectively bred to be both "Roundup ready" and also larger and higher yielding than the original strains of the plant. However, there are no reports of glyphosate-resistant coca in the peer-reviewed literature. In addition, since spraying of herbicides is not permitted in Colombian national parks, this has encouraged coca growers to move into park areas, cutting down the natural vegetation, and establishing coca plantations within park lands.
External links
Further reading
- Baccara, Mariagiovanna, et al. , NYU Stern School of Business: August 2001, Revised July 14, 2003.
- Pease W S et al. (1993) Preventing pesticide-related illness in California agriculture: Strategies and priorities. Environmental Health Policy Program Report. Berkeley, CA: University of California. School of Public Health. California Policy Seminar.
- Wang Y, Jaw C and Chen Y (1994) Accumulation of 2,4-D and glyphosate in fish and water hyacinth. Water Air Soil Pollute. 74:397-403
- Marie-Monique Robin. (2008) Le monde selon Monsanto. Arte Editions (book written in french). ISBN 978-2-7071-4918-3. An overview of Monsanto products: PCB, Dioxine,Roundup, Bovine Growth Hormone, OGM.
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