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Information about Paraquat

For the British military operation to recapture South Georgia, see Operation Paraquat.


Paraquat
IUPAC name1,1'-dimethyl-4,4'-bipyridinium dichloride
Other namesparaquat dichloride; methyl viologen dichloride; Crisquat; Dexuron; Esgram; Gramuron; Ortho Paraquat CL; Para-col; Pillarxone; Tota-col; Toxer Total; PP148; Cyclone; Gramixel; Gramoxone; Pathclear; AH 501.
Identifiers
CAS number1910-42-5
SMILES[Cl-].[Cl-].C[n+]1ccc(cc1)c2cc[n+](C)cc2
InChIInChI=1/C12H14N2.2ClH/c1-
13-7-3-11(4-8-13)12-
5-9-14(2)10-6-12;;/
h3-10H,1-2H3;2*1H/
q+2;;/p-2/fC12H14N2.2Cl/
h;2*1h/qm;2*-1
Properties
Molecular formulaC12H14Cl2N2
Molar mass257.16 g/mol
Appearanceoff-white powder
Density1.25 g/cm3, solid
Melting point 175 - 180 °C [1]
Boiling point > 300 °C [1]
Solubility in waterhigh
Hazards
Main hazardsToxic
Except where noted otherwise, data are given for
materials in their standard state
(at 25 C, 100 kPa)
Paraquat is the trade name for N,N'-Dimethyl-4,4'-bipyridinium dichloride, a viologen. Paraquat is used as a quaternary ammonium herbicide. It is dangerously poisonous to humans if swallowed. Other members of this class include diquat, cyperquat, diethamquat, difenzoquat, and morfamquat. All of these are easily reduced to the radical ion, which generates superoxide radical that reacts with unsaturated membrane lipids.

History

Paraquat was first produced for commercial purposes in 1961 by ICI (now Syngenta) and is today among the most commonly used herbicides.

The European Union allowed Paraquat in 2004. Sweden, supported by Denmark, Austria, and Finland, brought the European Union commission to court. On 11 July 2007 the court annulled the directive authorising Paraquat as an active plant protection substance.[2]

Herbicide use

The compound is one of the most widely used herbicides in the world. It is quick-acting, non-selective, and kills green plant tissue on contact. It is redistributed within the plant but does not harm mature bark.

Being a herbicide, paraquat protects crops by controlling a wide range of annual and certain perennial weeds that reduce crop yield and quality by competing with the crop for water, nutrients, and light.

The key characteristics that distinguish the non-selective contact herbicide paraquat from other active ingredients used in plant protection products are:
  • Paraquat is non-selective, which means it kills a wide range of annual grasses and broad-leaved weeds and the tops of established perennial weeds.
  • Paraquat is very fast-acting.
  • Paraquat is rain-fast within minutes of application.
  • Paraquat becomes biologically inactive upon contact with soil.[3]
In the United States, paraquat is available primarily as a liquid in various strengths. It is classified as "restricted use," which means that it can be used only by licensed applicators. As with many chemicals, caution must be exercised during use.

In the European Union, paraquat has been forbidden since July 10th 2007.

Health risks

Pure paraquat ingested is highly toxic to mammals and humans, and there are no specific antidotes. However, fuller's earth or activated charcoal is an effective treatment, if taken in time. Death may be up to 30 days after ingestion. Diluted paraquat used for spraying is less so, thus the greatest risk of accidental poisoning is during mixing and loading paraquat for use.[4]

In acute toxicity studies using laboratory animals, paraquat has been shown to be highly toxic by the inhalation route and has been placed in Toxicity Category I (the highest of four levels) for acute inhalation effects. However, the EPA has determined that particles used in agricultural practices (400 to 800 μm) are well beyond the respirable range and therefore inhalation toxicity is not a toxicological endpoint of concern. Paraquat is toxic (Category II) by the oral route and moderately toxic (Category III) by the dermal route. Paraquat will cause moderate to severe eye irritation and minimal dermal irritation, and has been placed in Toxicity Categories II and IV (slightly toxic) for these effects.[5]


Even a single swig immediately spat out can cause death from fibrous tissue developing in the lungs leading to asphyxiation.[6]

According to the Center for Disease Control, ingesting paraquat causes symptoms such as liver, lung, heart, and kidney failure within several days to several weeks that could lead to death up to 30 days after ingestion. Those who suffer large exposures are unlikely to survive. Chronic exposure can lead to lung damage, kidney failure, heart failure, and oesophageal strictures.[7]

Paraquat-induced toxicity in rats has also been linked to Parkinson's-like pathological degenerative mechanisms.[8] A study by the Buck Institute shows a connection between exposure to paraquat and iron in infancy and mid-life Parkinson's in laboratory mice.[9]

Long term exposures to paraquat would most likely cause lung and eye damage, but reproductive/fertility damage was not found by the EPA in their review. Some suspect a possible link to a greater incidence of Parkinson's disease.

Emergency care

Persons exposed to or contaminated by paraquat, with any suspected ingestion or absorption, should be treated by emergency medical services immediately. Prehospital care should follow these guidelines: [10]
  • Remove patient from further contact with substance.
  • Decontaminate with large volumes of water; remove patient's clothing.
  • Avoid secondary contamination by contact either with substance or runoff from decontamination efforts.
  • Establish and maintain a patent airway.
  • The administration of supplemental oxygen is advised against; however, prudent patient care dictates that oxygen should not be withheld from persons exhibiting clinical signs and symptoms of hypoxia. Emergency medical services personnel should consult with their medical control physician for specific case-by-case guidance.
  • Provide supportive treatment as indicated.
  • Consider evacuation to an appropriate hospital by helicopter; if air evacuation is not available, expedite transport by ground ambulance.
  • In the case of contamination of the eye, irrigate the affected eye with normal saline solution for at least 15 minutes.

Paraquat Pot

During the late 1960s, a controversial program sponsored by the US government sprayed paraquat on marijuana fields in South America. Since much of this marijuana was subsequently smoked by Americans, the US government's "Paraquat Pot" program stirred much debate. Perhaps in an attempt to deter people from using marijuana, representatives of the program warned that spraying rendered the crop unsafe to smoke. However, independent bodies have studied paraquat in this use. Jenny Pronczuk de Garbino, [11] stated: "no lung or other injury in marijuana users has ever been attributed to Paraquat contamination".

On this topic, D.P. Morgan states in a United States Environmental Protection Agency publication that: "Smoking Paraquat-contaminated marijuana does not result in lung damage as the herbicide is pyrolyzed to dipyridyl (which does not present a toxic hazard) during smoking". [12]

References

1. ^ Paraquat dichloride. International Programme on Chemical Safety (October 2001).
2. ^ COURT OF FIRST INSTANCE OF THE EUROPEAN COMMUNITIES, PRESS RELEASE No° 45/07
3. ^ Revkin, A. C. 1983. Paraquat: A potent weed killer is killing people. Science Digest 91(6):36-38, 42, 100-104.
4. ^ PAN UK, Paraquat, accessed 13 October 2006.
5. ^ EPA, [1], accessed 16 August 2007.
6. ^ Buzik, Shirley C.; Schiefer, H. Bruno; Irvine, Donald G. (1997). Understanding Toxicology: Chemicals, Their Benefits and Risks. Boca Raton: CRC Press, 31. ISBN 0-8493-2686-9. 
7. ^ Center for Disease Control, Facts about Paraquat, accessed 13 October 2006.
8. ^ K. Ossowska, M. S'Mialowska, K. Kuter, J. Wieron'ska, B. Zieba, J. Wardas, P. Nowak, J. Dabrowska, A. Bortel, I. Biedka, G. Schulze and H. Rommelspacher (2006). "Degeneration of dopaminergic mesocortical neurons and activation of compensatory processes induced by a long-term paraquat administration in rats: Implications for Parkinson's disease". Neuroscience 141 (4): 2155-2165. DOI:10.1016/j.neuroscience.2006.05.039.Neuroscience&rft.date=2006&rft.volume=141&rft.issue=4&rft.au=K.%20Ossowska,%20M.%20S%27Mialowska,%20K.%20Kuter,%20J.%20Wieron%27ska,%20B.%20Zieba,%20J.%20Wardas,%20P.%20Nowak,%20J.%20Dabrowska,%20A.%20Bortel,%20I.%20Biedka,%20G.%20Schulze%20and%20H.%20Rommelspacher&rft.pages=2155-2165&rft_id=info:doi/10.1016%2Fj.neuroscience.2006.05.039"> 
9. ^ Buck Institute for Aging Research (June 2007). Combined Exposure to Environmental Toxics Accelerates Age-related Development of Parkinson's Disease in Mice. Press release.
10. ^ Halpin, Ted; Eric Hallman, Ellen Abend, Tonya Van Slyke (2005). Cornell Farmedic Training Program Student Manual. Ithaca, NY: Cornell University Press. 
11. ^ Pronczuk de Garbino J, Epidemiology of paraquat poisoning, in: Bismuth C, and Hall AH (eds), Paraquat Poisoning: Mechanisms, Prevention, Treatment, pp. 37-51, New York: Marcel Dekker, 1995.
12. ^ Reigart, J. Routt and Roberts, James R. Recognition and Management of Pesticide Poisonings, 5th edition. Washington, DC: United States Environmental Protection Agency, 1999. Book available online

External links

Operation Paraquet was the code name for the British military operation to recapture the Island of South Georgia from Argentine military control in April 1982 at the start of the Falklands War.
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File extension: .smi
Type of format: chemical file format

The simplified molecular input line entry specification or SMILES
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The IUPAC International Chemical Identifier (InChI) is a textual identifier for chemical substances, designed to provide a human-readable standard way to encode molecular information and to facilitate the search for such information in databases and on the web.
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A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs.
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Molar mass, symbol M,[1] is the mass of one mole of a substance (chemical element or chemical compound).[2] It is a physical property which is characteristic of each pure substance.
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In physics, density is mass m per unit volume V—how heavy something is compared to its size. A small, heavy object, such as a rock or a lump of lead, is denser than a lighter object of the same size or a larger object of the same weight, such as pieces of
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The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. Although the phrase would suggest a specific temperature and is commonly and incorrectly used as such in most textbooks and literature, most crystalline compounds
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boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid.[1][2][3][4]
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Solubility is a physical property referring to the ability for a given substance, the solute, to dissolve in a solvent.[1] It is measured in terms of the maximum amount of solute dissolved in a solvent at equilibrium. The resulting solution is called a saturated solution.
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Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
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standard state of a material is its state at 1 bar (100 kilopascals exactly). This pressure was changed from 1 atm (101.325 kilopascals) by IUPAC in 1990.[1] The standard state of a material can be defined at any given temperature, most commonly 25 degrees Celsius,
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The Viologens are diquaternary derivatives of 4,4'-bipyridyl. The name comes from the fact that this class of compounds is easily reduced to the radical mono cation, which is intensely blue coloured.
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A herbicide is used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often based on plant hormones.
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Diquat is a contact herbicide that produces desiccation and defoliation. As an ionic compound, it may have a variety of counterions associated with it. The herbicide is most often used as the dibromide salt, diquat dibromide.
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Superoxide is the anion O2−. It is important as the product of the one-electron reduction of dioxygen, which occurs widely in nature.[1] With one unpaired electron, the superoxide ion is a free radical, and, like dioxygen, it is paramagnetic.
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Lipids can be broadly defined as any fat-soluble (hydrophobic), naturally-occurring molecules. The term is more-specifically used to refer to fatty-acids and their derivatives (including tri-, di-, and monoglycerides and phospholipids) as well as other fat-soluble sterol-containing
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19th century - 20th century - 21st century
1930s  1940s  1950s  - 1960s -  1970s  1980s  1990s
1958 1959 1960 - 1961 - 1962 1963 1964

Year 1961 (MCMLXI
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Imperial Chemical Industries plc

Public (LSE:  ICI )
Founded 1926
Headquarters London, England, UK

Key people Peter Ellwood (Chairman)
John McAdam (CEO)
Industry Chemicals
Products Paints & speciality chemicals
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Syngenta AG is a large global agribusiness which markets seeds and crop protection products (pesticides). Syngenta is involved in biotechnology and genomic research.
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WEED

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WEED
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Grass is a common word that generally describes a monocotyledonous green plant in the family Gramineae (Poaceae). True grasses include most plants grown as grains, for pasture, and for lawns (turf).
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Fuller's earth is any nonplastic clay or claylike earthy material that can be used to decolorize, filter, and purify animal, mineral, and vegetable oils and greases.

Occurrence and composition


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Activated carbon, also called activated charcoal or activated coal, is a general term which covers carbon material mostly derived from charcoal. For all three variations of the name, "activated" is sometimes substituted by "active".
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