Paraquat (
trivial name
In chemistry, a trivial name is a nonsystematic name for a chemical substance. That is, the name is not recognized according to the rules of any formal system of chemical nomenclature such as IUPAC nomenclature of inorganic chemistry, IUPAC inor ...
; ), or ''N'',''N''′-dimethyl-4,4′-bipyridinium dichloride (
systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature.
A semisystematic name or semitrivial ...
), also known as methyl viologen, is an
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
with the
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...
6H7N)2">C6H7N)2l
2. It is classified as a
viologen
Viologens are organic compounds with the formula (C5H4NR)2n+. In some viologens, the pyridyl groups are further modified.
Viologens are called so, because these compounds produce violet color on reduction iolet + Latin ''gen'', generator of
T ...
, a family of
redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...
-active heterocycles of similar structure. This salt is one of the most widely used
herbicide
Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
s. It is quick-acting and non-selective, killing green plant tissue on contact. It is also toxic (lethal) to human beings and animals due to its
redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...
activity, which produces
superoxide
In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of the ...
anions. It has been linked to the development of
Parkinson's disease
Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
and is banned in several countries.
Paraquat may be in the form of
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
with
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
or other anions; quantities of the substance are sometimes expressed by cation mass alone (paraquat cation, paraquat ion).
The name is derived from the ''
para
Para, or PARA, may refer to:
Businesses and organizations
* Paramount Global, traded as PARA on the Nasdaq stock exchange
* Para Group, the former name of CT Corp
* Para Rubber, now Skellerup, a New Zealand manufacturer
* Para USA, formerly ...
'' positions of the
''quaternary'' nitrogens.
Production
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...
is coupled by treatment with
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...
in
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
followed by oxidation to give
4,4′-bipyridine. This chemical is then di
methylated
In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These ...
with
chloromethane
Chloromethane, also called methyl chloride, Refrigerant-40, R-40 or HCC 40, is an organic compound with the chemical formula . One of the haloalkanes, it is a colorless, odorless, flammable gas. Methyl chloride is a crucial reagent in industrial ...
to give the final product as the dichloride salt.
![Synthesis of paraquat](https://upload.wikimedia.org/wikipedia/commons/c/ca/Synthesis_of_paraquat.png)
Use of other methylating agents gives the bispyridinium with alternate
counterion
160px, Polystyrene sulfonate, a cation-exchange resin, is typically supplied with as the counterion.">cation-exchange_resin.html" ;"title="Polystyrene sulfonate, a cation-exchange resin">Polystyrene sulfonate, a cation-exchange resin, is typical ...
s. For example,
Hugo Weidel
Hugo Weidel (13 November 1849 – 7 June 1899) was an Austrian chemist known for inventing Weidel's reaction and describing the structure of organic compound niacin. For his achievements, Weidel received the Lieben Prize in 1880.
Life and work
Hu ...
's original synthesis used
methyl iodide
Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one h ...
to produce the di
iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...
.
Herbicide use
Although first synthesized in 1882,
[ The Austrian chemist ]Hugo Weidel
Hugo Weidel (13 November 1849 – 7 June 1899) was an Austrian chemist known for inventing Weidel's reaction and describing the structure of organic compound niacin. For his achievements, Weidel received the Lieben Prize in 1880.
Life and work
Hu ...
and his student M. Russo synthesized the iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...
salt of paraquat (which they called ''Dimethyldipyridyljodid'') by reacting 4,4'-bipyridine
4,4′-Bipyridine (abbreviated to 4,4′-bipy or 4,4′-bpy) is an organic compound with the formula . It is one of several isomers of bipyridine. It is a colorless solid that is soluble in organic solvents. is mainly used as a precursor to ''N ...
(''γ-Dipyridyl'') with methyl iodide
Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one h ...
(''Jodmethyl''). The synthesis is described on pages 863–864 and the molecule's structure is proposed on p. 867. paraquat's herbicidal properties were not recognized until 1955 in the
Imperial Chemical Industries
Imperial Chemical Industries (ICI) was a British chemical company. It was, for much of its history, the largest manufacturer in Britain.
It was formed by the merger of four leading British chemical companies in 1926.
Its headquarters were at M ...
(ICI) laboratories at
Jealott's Hill
Jealott's Hill is a village in the county of Berkshire, England, within the civil parish of Warfield. The settlement is on the A3095 road approximately north of Bracknell. The nearest railway station is in .
The name of the hill is reported to ...
.
Paraquat was first manufactured and sold by ICI in early 1962 under the
trade name
A trade name, trading name, or business name, is a pseudonym used by companies that do not operate under their registered company name. The term for this type of alternative name is a "fictitious" business name. Registering the fictitious name w ...
Gramoxone, and is today among the most commonly used herbicides.
Paraquat is classified as a non-selective contact herbicide. The key characteristics that distinguish it from other agents used in plant protection products are:
*It kills a wide range of annual
grass
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...
es and broad-leaved weeds and the tips of established perennial weeds.
*It is very fast-acting.
*It is
rain-fast within minutes of application.
*It is partially inactivated upon contact with soil.
These properties led to paraquat being used in the development of
no-till farming
No-till farming (also known as zero tillage or direct drilling) is an agricultural technique for growing crops or pasture without disturbing the soil through tillage. No-till farming decreases the amount of soil erosion tillage causes in certai ...
.
The European Union approved the use of paraquat in 2004 but Sweden, supported by Denmark, Austria, and Finland, appealed this decision. In 2007, the court annulled the directive authorizing paraquat as an active plant protection substance stating that the 2004 decision was wrong in finding that there were no indications of neurotoxicity associated with paraquat and that the studies about the link between paraquat and
Parkinson's disease
Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
should have been considered.
[Court of first instance of the European Communities]
Press Release No° 45/07
Thus, paraquat has been banned in the European Union since 2007.
![Paraquat use USA](https://upload.wikimedia.org/wikipedia/commons/f/fe/Paraquat_use_USA.png)
In the United States, paraquat is available primarily as a solution in various strengths. It is classified as "restricted use", which means that it can be used by licensed applicators only. The estimated use of paraquat in US agriculture is mapped by the US Geological Survey and shows a doubling from 2013 to 2018, the latest date for which figures are available, and now reaching annually.
There is an ongoing international campaign for a global ban, but the cheap and popular paraquat continues to be unrestricted in most developing countries. A small group of countries, including India and Guatemala and supported by manufacturers, have blocked the listing of paraquat as a hazardous chemical for the purposes of the
Rotterdam Convention
The Rotterdam Convention (formally, the Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade) is a multilateral treaty to promote shared responsibilities in relation ...
.
Reactivity and mode of action
Paraquat is an oxidant that interferes with
electron transfer
Electron transfer (ET) occurs when an electron relocates from an atom or molecule to another such chemical entity. ET is a mechanistic description of certain kinds of redox reactions involving transfer of electrons.
Electrochemical processes ar ...
, a process that is common to all life. Addition of one electron gives the radical cation:
:
araquatsup>2+ + e
− araquatsup>•+
The radical cation is also susceptible to further reduction to the neutral
araquatsup>0:
:
araquatsup>•+ + e
− araquatsup>0
As an herbicide, paraquat acts by inhibiting photosynthesis. In light-exposed plants, it accepts electrons from
photosystem I
Photosystem I (PSI, or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I is an integral membrane protein complex that uses ...
(more specifically
ferredoxin
Ferredoxins (from Latin ''ferrum'': iron + redox, often abbreviated "fd") are iron–sulfur proteins that mediate electron transfer in a range of metabolic reactions. The term "ferredoxin" was coined by D.C. Wharton of the DuPont Co. and applied t ...
, which is presented with electrons from PS I) and transfers them to molecular oxygen. In this manner, destructive
reactive oxygen species
In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen.
The reduction of molecular oxygen () p ...
(ROS) are produced. In forming these reactive oxygen species, the oxidized form of paraquat is regenerated, and is again available to shunt electrons from photosystem I to restart the cycle. This induces
necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
, and unlike with some mechanisms of necrosis, does not produce
double-stranded break
DNA repair is a collection of processes by which a cell (biology), cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolism, metabolic activities and environmental factors such as r ...
s.
Paraquat is often used in science to catalyze the formation of ROS, more specifically, the
superoxide
In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of the ...
free radical. Paraquat will undergo redox cycling ''in vivo'', being reduced by an electron donor such as
NADPH
Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NAD ...
, before being oxidized by an electron receptor such as
dioxygen
There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are:
*A ...
to produce
superoxide
In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of the ...
, a major ROS.
Weed resistance management
Problems with
herbicide resistant weeds may be addressed by applying herbicides with different modes of action, along with cultural methods such as
crop rotation
Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. It reduces reliance on one set of nutrients, pest and weed pressure, and the probability of developing resistant ...
, in
integrated weed management (IWM) systems. Paraquat, with its distinctive mode of action, is one of few chemical options that can be used to prevent and mitigate problems with weeds that have become resistant to the very widely used non-selective herbicide
glyphosate
Glyphosate (IUPAC name: ''N''-(phosphonomethyl)glycine) is a broad-spectrum Herbicide, systemic herbicide and Crop desiccation, crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plan ...
.
One example is the "double knock" system used in Australia. Before planting a crop, weeds are sprayed with glyphosate first, then followed seven to ten days later by a paraquat herbicide. Although twice as expensive as using a single glyphosate spray, the "Double Knock" system is widely relied upon by farmers as a resistance management strategy. Nevertheless, herbicide resistance has been seen for both herbicides in Western Australia.
A computer simulation showed that with alternating annual use between glyphosate and paraquat, only one field in five would be expected to have glyphosate-resistant annual ryegrass (''
Lolium rigidum
''Lolium rigidum'' is a species of annual grass. Common names by which it is known include annual ryegrass, a name also given to Italian ryegrass (''Lolium multiflorum''), rigid ryegrass, stiff darnel, Swiss ryegrass and Wimmera ryegrass. It is ...
'') after 30 years, compared to nearly 90% of fields sprayed only with glyphosate. A "Double Knock" regime with paraquat cleaning-up after glyphosate was predicted to keep all fields free of glyphosate resistant ryegrass for at least 30 years.
Toxicity
Paraquat is toxic to humans (
Category II) by the oral route and moderately toxic (
Category III) through the skin.
[Paraquat Dichloride](_blank)
, United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
, accessed 16 August 2007. Pure paraquat, when ingested, is highly toxic to mammals, including humans, causing severe inflammation and potentially leading to severe lung damage, acute respiratory distress syndrome (
ARDS
Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin color ...
), and death.
The mortality rate is estimated between 60-90%.
Paraquat is also toxic when inhaled and is in the
Toxicity Category I (the highest of four levels) for acute inhalation effects.
For agricultural uses, the EPA determined that particles used in agricultural practices (400–800 μm) are not in the respirable range.
Paraquat also causes moderate to severe irritation of the eye and skin.
Diluted paraquat used for spraying is less toxic; thus, the greatest risk of accidental poisoning is during mixing and loading paraquat for use.
The standard treatment for paraquat poisoning is first to remove as much as possible by pumping the stomach.
Fuller's earth
Fuller's earth is any clay material that has the capability to decolorize oil or other liquids without the use of harsh chemical treatment. Fuller's earth typically consists of palygorskite (attapulgite) or bentonite.
Modern uses of fuller's ea ...
or
activated charcoal
"Activated" is a song by English singer Cher Lloyd. It was released on 22 July 2016 through Vixen Records. The song was made available to stream exclusively on ''Rolling Stone'' a day before to release (on 21 July 2016).
Background
In an interv ...
may also improve outcomes depending on the timing. Haemodialysis, haemofiltration, haemoperfusion, or antioxidant therapy may also be suggested.
Immunosuppressive therapy to reduce the inflammation is an approach suggested by some, however only low certainty evidence supports using medications such as
glucocorticoids
Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every vertebr ...
with
cyclophosphamide
Cyclophosphamide (CP), also known as cytophosphane among other names, is a medication used as chemotherapy and to suppress the immune system. As chemotherapy it is used to treat lymphoma, multiple myeloma, leukemia, ovarian cancer, breast cancer ...
in addition to the standard care to reduce mortality.
It is also unknown if adding glucocorticoid with cyclophosphamide to the standard care has unwanted side effects such as increasing the risk of infection.
Oxygen should not be administered unless
SpO2 levels are below 92%, as high concentrations of oxygen intensify the toxic effects.
Death may occur up to 30 days after ingestion.
Lung injury is a main feature of poisoning. Liver, heart, lung, and kidney failure can occur within several days to weeks that can 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.
Centers for Disease Control
The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
Facts about Paraquat
, accessed 13 October 2006. The mechanism underlying paraquat's toxic damage to humans is still unknown. The severe inflammation is thought to be caused by the generation of highly
reactive oxygen species
In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen.
The reduction of molecular oxygen () p ...
and
nitrite
The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
species that results in
oxidative stress
Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily Detoxification, detoxify the reactive intermediates or to repair the resulting damage. Disturbances ...
. The oxidative stress may result in
mitochondrial toxicity
Mitochondrial toxicity is a condition in which the mitochondria of a body's cells become damaged or decline significantly in number; it occurs as a side effect of certain antiretroviral drugs used to treat human immunodeficiency virus, or HIV.
C ...
and the
induction of apoptosis and
lipid peroxidation
Lipid peroxidation is the chain of reactions of oxidative degradation of lipids. It is the process in which radical (chemistry), free radicals "steal" electrons from the lipids in cell membranes, resulting in cell damage. This process proceeds by ...
which may be responsible for the organ damage.
it is known that the
alveolar Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit.
Uses in anatomy and zoology
* Pulmonary alveolus, an air sac in the lungs
** Alveolar cell or pneumocyte
** Alveolar duct
** Alveolar macrophage
* ...
epithelial cells
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...
of the lung selectively concentrate paraquat. It has been reported that a small dose, even if removed from the stomach or spat out, can still cause death from fibrous tissue developing in the lungs, leading to
asphyxiation
Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can i ...
.
Accidental deaths and suicides from paraquat ingestion are relatively common. For example, there are more than 5,000 deaths in China from paraquat poisoning every year. Long-term exposures to paraquat would most likely cause lung and eye damage, but reproductive/fertility damage was not found by the
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
(EPA) in their review.
"Paraquat pot"
During the late 1970s, a controversial program sponsored by the US government sprayed paraquat on
cannabis
''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: ''Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternatively ...
fields in Mexico. Following Mexican efforts to eradicate marijuana and poppy fields in 1975, the United States government helped by sending helicopters and other technological assistance. Helicopters were used to spray the herbicides paraquat and
2,4-D on the fields; marijuana contaminated with these substances began to show up in US markets, leading to debate about the program.
Whether any injury came about due to the inhalation of paraquat-contaminated marijuana is uncertain. A 1995 study found that "no lung or other injury in cannabis users has ever been attributed to paraquat contamination". Also a
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
manual states: "... toxic effects caused by this mechanism have been either very rare or nonexistent. Most paraquat that contaminates cannabis is
pyrolyzed during smoking to
dipyridyl, which is a product of combustion of the leaf material itself (including cannabis) and presents little toxic hazard."
In a study by
Imperial Chemical Industries
Imperial Chemical Industries (ICI) was a British chemical company. It was, for much of its history, the largest manufacturer in Britain.
It was formed by the merger of four leading British chemical companies in 1926.
Its headquarters were at M ...
, rats that inhaled paraquat showed development of
squamous metaplasia
Squamous metaplasia is a benign non-cancerous change (metaplasia) of surfacing lining cells (epithelium) to a squamous morphology.
Location
Common sites for squamous metaplasia include the bladder and cervix. Smokers often exhibit squamous me ...
in their respiratory tracts after a couple of weeks. This study was included in a report given to the State Department by the
Mitre Corporation. The
U.S. Public Health Service
The United States Public Health Service (USPHS or PHS) is a collection of agencies of the Department of Health and Human Services concerned with public health, containing nine out of the department's twelve operating divisions. The Assistant ...
stated that "this study should not be used to calculate the safe inhalation dose of paraquat in humans."
Use in suicide and murder
A large majority (93 percent) of fatalities from paraquat poisoning are
suicide
Suicide is the act of intentionally causing one's own death. Mental disorders (including depression, bipolar disorder, schizophrenia, personality disorders, anxiety disorders), physical disorders (such as chronic fatigue syndrome), and s ...
s, which occur mostly in
developing countries
A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreem ...
. For instance, in
Samoa
Samoa, officially the Independent State of Samoa; sm, Sāmoa, and until 1997 known as Western Samoa, is a Polynesian island country consisting of two main islands (Savai'i and Upolu); two smaller, inhabited islands (Manono Island, Manono an ...
from 1979 to 2001, 70 percent of suicides were by paraquat poisoning. Trinidad and Tobago is particularly well known for its incidence of suicides involving the use of Gramoxone (commercial name of paraquat). In southern
Trinidad
Trinidad is the larger and more populous of the two major islands of Trinidad and Tobago. The island lies off the northeastern coast of Venezuela and sits on the continental shelf of South America. It is often referred to as the southernmos ...
, particularly in Penal, Debe from 1996 to 1997, 76 percent of suicides were by paraquat, 96 percent of which involved the over-consumption of alcohol such as rum. Fashion celebrity
Isabella Blow
Isabella "Issie" Blow (nee Delves Broughton; 19 November 1958 – 7 May 2007) was an English magazine editor. As the muse of hat designer Philip Treacy, she is credited with discovering the models Stella Tennant and Sophie Dahl as well as pr ...
committed suicide using paraquat in 2007. Paraquat is widely used as a suicide agent in third-world countries because it is widely available at low cost. Further, the toxic dose is low (10 mL or 2 teaspoons is enough to kill). Campaigns exist to control or even ban paraquat, and there are moves to restrict its availability by requiring user education and the locking up of paraquat stores. When a 2011 South Korean law completely banned paraquat in the country, death by pesticide plummeted 46%, contributing to the decrease of the overall suicide rate.
The indiscriminate
paraquat murders
The paraquat murders were a series of indiscriminate poisonings carried out in Japan in 1985. Police were unable to gather any evidence about the murders, and the case remains unsolved. All the beverages were poisoned with the herbicide paraquat ...
, which occurred in Japan in 1985, were carried out using paraquat as a poison.
Paraquat was used in the UK in 1981 by a woman who poisoned her husband.
Steven David Catlin killed two of his wives and his adoptive mother with paraquat between 1976 and 1984.
Parkinson's disease
In 2011, a US
National Institutes of Health
The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...
study showed a link between paraquat use and
Parkinson's disease
Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
in farm workers. A co-author of the paper said that paraquat increases production of certain oxygen derivatives that may harm cellular structures, and that people who used paraquat, or other pesticides with a similar mechanism of action, were more likely to develop Parkinson's.
Paraquat-induced toxicity in rats has also been linked to Parkinson's-like neurological degenerative mechanisms. A study by researchers at the
Buck Institute for Research on Aging
The Buck Institute for Research on Aging is an independent biomedical research institute that researches aging and age-related disease. The mission of the Buck Institute is to extend the healthy years of life. The Buck Institute is one of nine cen ...
showed a connection between exposure to paraquat and iron in infancy and mid-life Parkinson's in laboratory mice. A 2013 meta-analysis published in ''Neurology'' found that "exposure to paraquat ... was associated with about a 2-fold increase in risk" of Parkinson's disease.
Paraquat is structurally similar to
MPP+, a known fast-acting inducer of Parkinson's disease in primate brains. The chloride of MPP
+ was sold under the trade name Cyperquat.
Paraquat also induces
oxidative stress
Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily Detoxification, detoxify the reactive intermediates or to repair the resulting damage. Disturbances ...
in
invertebrates
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
such as ''
Drosophila melanogaster
''Drosophila melanogaster'' is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly" or "pomace fly". Starting with Ch ...
''. Paraquat-fed flies suffer early-onset mortality and significant increases in
superoxide dismutase
Superoxide dismutase (SOD, ) is an enzyme that alternately catalyzes the dismutation (or partitioning) of the superoxide () radical into ordinary molecular oxygen (O2) and hydrogen peroxide (). Superoxide is produced as a by-product of oxygen me ...
activity.
While in 2022 UK farmers were calling for a ban on the UK production of paraquat, a BBC article stated that "There is no scientific consensus and many conflicting studies on any possible association between Paraquat and Parkinson's"; in the USA a
class action
A class action, also known as a class-action lawsuit, class suit, or representative action, is a type of lawsuit where one of the parties is a group of people who are represented collectively by a member or members of that group. The class actio ...
lawsuit against Syngenta is ongoing; the company rejects the claims but has paid £187.5 million into a settlement fund.
References
Further reading
*
*
External links
*
*
*
*
*
{{Authority control
Herbicides
Bipyridines
Avian embryotoxicants
Superoxide generating substances
Nephrotoxins
Pyridinium compounds