Paraquat is the trade name for N,N'-Dimethyl-4,4'-bipyridinium dichloride or viologen, a quaternary ammonium herbicide. It is dangerously poisonous to humans. 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.
Characteristics
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 (unwanted plants) 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 grass 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.
Paraquat was first produced for commercial purposes in 1961 by ICI (now Syngenta) and is today among the most commonly used herbicides.
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.
Health Risks
Paraquat is dangerously poisonous, and many people have died of paraquat poisoning. See http://www.pan-uk.org/pestnews/actives/paraquat.htm
Paraquat like many chemicals can be harmful if the guidelines for safe use are not followed.
According to the Center for Disease Control, paraquat exposure can lead to several health risks, such as liver, lung, heart, and kidney failure in a matter of weeks after exposure to a medium dose of paraquat. However, when following the safety guidelines paraquat proves to be a very useful tool for weed control.
Paraquat can be found in the air in areas that have been sprayed with the herbicide. Ground water that has leached the chemical is also a source of contamination and exposure.
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 the spraying and rendered the crop unsafe to smoke. However, independent bodies have studied paraquat in this use. Jenny PronCzuk de Garbino, (Ref: 1) 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 US 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" (Ref: 2).
External links
References
- 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.
- Reigart,J Routt and Roberts, James R. Paraquat and diquat in: Recognition and Management of Pesticide Poisonings by RJ Reigart and JR Roberts. 5th edition. Washington, DC: US Environmental Protection Agency, 1999. Book can be accessed at: http://www.epa.gov/pesticides/safety/healthcare/handbook/handbook.pdf