Roundup Totally Explained

Everything about Roundup totally explained

| Section2 = | Section3 = }} 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 and is the most-sold agrichemical of all time. 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. 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 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 isn't 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 an 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.

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.

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 hasn't 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 isn't 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 indicates 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.
   Studies have shown that the application of Roundup on wheat crops a week before harvesting results in higher glyphosate residue in the resulting grain and in the baked flour.
   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 isn't 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.
Roundup isn't registered for aquatic uses and studies of its effects on amphibians indicate it's 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. Low activity because of binding to soil particles suggests that glyphosate's effects on soil flora will be limited. Roundup has been shown to increase the disease rate in the crop following a sprayed crop, suggesting damaged soil flora.
Low glyphosate concentrations can be found in many creeks and rivers in U.S. and Europe, and in the US glyphosate has been called "relatively persistent" by the EPA.
   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 more northern sites have the longest soil persistences such as in Canada and Scandinavia.
   However, the binding of glyphosate to particulates can be an advantage for the detoxification of industrial toxin-polluted streams containing a wide class of toxicants. Treatment of industrial wastewater using immobilized bacteria showed complete conversion of glyphosate to nontoxic aminomethylphosphonic acid.
   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.
Monsanto firmly denies any negative impact on anything, including wildlife, and has many studies it has funded to back up its position. They would also be quick to point out that any possible negative impact on earthworms and nitrogen fixing bacteria, etc., would be offset by greater yields, which have not been proven, due to the elimination of weeds, and also would point to soil benefits from less mechanical cultivation of weeds by using Roundup and similar products.

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. 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's resistant to glyphosate inhibition. The version used in genetically modified crops was isolated from Agrobacterium strain CP4 (CP4 EPSPS) that was resisitant 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 .

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 maufacturers and marketed under many names, including Buccanner, 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 which have been selectively bred to be both "Roundup ready" and also larger and higher yielding than the original strains of the plant. (External Link

) However, there are no reports of glyphosate-resistant coca in the peer-reviewed literature. In addition, since spraying of herbicides isn't 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.

Further Information

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