Humans And The Environment Through Agriculture - amazonia.fiocruz.br

Assured, what: Humans And The Environment Through Agriculture

It is an organophosphorus compoundspecifically a phosphonatewhich acts by inhibiting the plant enzyme 5-enolpyruvylshikimatephosphate synthase. It is used to kill weedsespecially annual broadleaf weeds and grasses that compete with crops. It was discovered to be an herbicide by Monsanto chemist John E.

Franz in Monsanto brought it to market for agricultural use in under the trade name Roundup. Monsanto's last commercially relevant United States patent expired in Farmers quickly adopted glyphosate for agricultural weed control, especially after Monsanto introduced glyphosate-resistant Roundup Ready cropsenabling farmers to kill weeds without killing their crops. Inglyphosate was the most used herbicide in the United States' agricultural sector and the second-most used after 2,4-D in home and garden, government and industry, and commercial applications.

This was partly in response to the global emergence and spread of glyphosate-resistant weeds, [7] : 1 requiring greater application to maintain effectiveness. The development of glyphosate resistance in weed species Humans And The Environment Through Agriculture emerging as a costly problem. Glyphosate is absorbed through foliage, and minimally through roots, and transported to growing points [ citation needed ]. It inhibits a plant enzyme involved in the synthesis of three aromatic amino acids : tyrosinetryptophanand phenylalanine. It is therefore effective only on actively growing plants and is not effective as a pre-emergence herbicide.

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An increasing number of crops have been genetically Hkmans to be tolerant of glyphosate e. Thhrough Ready soybeanthe first Roundup Ready crop, also created by Monsantowhich allows farmers to use glyphosate as a post-emergence herbicide against weeds. While glyphosate and formulations Humans And The Environment Through Agriculture as Roundup have been approved by regulatory bodies worldwide, concerns about their effects on humans and the environment persist, and have grown as the global usage of glyphosate increases. The German Federal Institute for Risk Assessment toxicology review in found that "the available data is contradictory and far from being convincing" with regard to correlations between exposure to glyphosate formulations and risk of various cancers, including non-Hodgkin lymphoma NHL.

Glyphosate was first synthesized in by Swiss chemist Henry Martin, who worked for the Swiss company Cilag. The work was never published. Somewhat later, glyphosate was independently discovered in the United States at Monsanto in Monsanto chemists had synthesized about derivatives of aminomethylphosphonic acid as potential water-softening agents.

Two were found to have weak herbicidal activity, and John E.

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Franza chemist at Monsanto, was asked to try to make analogs with stronger herbicidal activity. Glyphosate was the third analog he made. Monsanto developed and patented the use of glyphosate to kill weeds in the early s and first brought it to market inunder the Roundup brandname. Duke and Stephen B. Glyphosate is an aminophosphonic analogue of the natural amino acid glycine and, like all amino acids, exists in different ionic states depending on pH.

Both the phosphonic acid and carboxylic acid moieties can be ionised and the amine group can be protonated and the substance exists as a series of zwitterions. The original synthetic approach to glyphosate involved the reaction of phosphorus trichloride with formaldehyde followed by hydrolysis to yield a phosphonate. Glycine is then reacted with this phosphonate to yield glyphosate, and its name is taken as a contraction of the compounds used in this synthesis step, namely gly cine and a phos phon ate. The main deactivation path for glyphosate is hydrolysis to aminomethylphosphonic acid.

Two main approaches are used to synthesize glyphosate industrially. The first is to react iminodiacetic acid with phosphorous acid and hydrochloric acid sometimes formed in situ by addition of phosphorus trichloride via a modified Mannich reaction. Oxidation then leads to the desired glyphosate product. Iminodiacetic acid is usually prepared on-site by various methods depending on reagent availability.

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The second involves hydrophosphonylationusing dimethyl phosphite in a one-pot synthesis. Dimethyl phosphite is then introduced, which leads to a substitution reaction of the hydroxyl of one of the two hydroxymethyl groups. Work-up with hydrochloric acid and heat cleaves the remaining hydroxymethyl group from the nitrogen atom and hydrolyzes both Ad ester linkages.

This synthetic approach is responsible for a substantial portion of the production of glyphosate in China, with considerable work having gone into recycling the triethylamine and methanol. Formaldehydeclassified as a known human carcinogen, [36] [37] and N -nitrosoglyphosatehave been identified as toxicologically relevant impurities.]