Parathion
Encyclopedia
Parathion, also called parathion-ethyl or diethyl parathion, is an organophosphate compound. It is a potent insecticide
and acaricide. It was originally developed by IG Farben
in the 1940s. It is highly toxic to non-target organisms, including humans. Its use is banned or restricted in many countries, and there are proposals to ban it from all use. Closely related is "methyl parathion" (see below).
for the German
trust IG Farben
in the 1940s. After the war and the collapse of IG Farben due to the war crime trials, the Western allies seized the patent
, and parathion was marketed worldwide by different companies and under different brand names. The most common German brand was E605 (banned in Germany after 2002); this was not a food-additive "E number
" as used in the EU today. "E" stands for Entwicklungsnummer (German for "development number").
that smells of rotting egg
s or garlic
. The insecticide is more or less stable, although it darkens when exposed to sunlight.
with ethanol (methanol
is used to prepare methyl parathion). Diethyl dithiophosphoric acid is chlorinated to generate diethylthiophosphoryl chloride. The diethyl dithiophosphoric acid is then treated with sodium 4-nitrophenolate (the sodium
salt of 4-nitrophenol
).
, rice
and fruit
trees. The usual concentrations of ready-to-use solutions are 0.05 to 0.1%. The chemical is banned for use on many food crops.
, but indirectly. After being ingested by insects (and unintentionally, by humans), the parathion becomes oxidized by oxidase
s to give paraoxon
, replacing the double bonded sulfur with oxygen.
2P(S)OC6H4NO2 + 1/2 O2 → (C2H5O)2P(O)OC6H4NO2 + S
The phosphate ester is more reactive in organisms than the phosphorothiolate ester, as the phosphorus atoms become much more electronegative.
, which deactivates the molecule, occurs at the aryl ester bond resulting in diethyl thiophosphate and 4-nitrophenol
.2P(S)OC6H4NO2 + H2O → HOC6H4NO2 + (C2H5O)2P(S)OH
Degradation proceeds differently under anaerobic conditions: the nitro group on parathion is reduced to the amine
.2P(S)OC6H4NO2 + 6 H → (C2H5O)2P(S)OC6H4NH2 + 2 H2O
by inhibiting the acetylcholinesterase
. It is absorbed via skin, mucous membranes, and orally. Absorbed parathion is rapidly metabolized to paraoxon, as described above. Paraoxon exposure can result in headache
s, convulsions, poor vision, vomiting
, abdominal pain, severe diarrhea
, unconsciousness
, tremor
, dyspnea
, and finally lung-edema
as well as respiratory arrest. Symptoms of poisoning are known to last for extended periods of time, sometimes months. The most common and very specific antidote is atropine
in doses of up to 100 mg daily. Because atropine may also be toxic, it is recommended that small frequently repeated doses be used in treatment. If human poisoning is detected early and the treatment is prompt (atropine and artificial respiration), fatalities are infrequent. Insufficient oxygen will lead to cerebral hypoxia
and permanent brain damage. Peripheral neuropathy
including paralysis
is noticed as late sequelae after recovery from acute intoxication. Parathion has been used for committing suicide and deliberately poisoning other persons. It is known as "Schwiegermuttergift" (mother-in-law poison) in Germany. For this reason most formulations contain a blue dye providing warning.
Parathion has been used as a chemical weapon, most notably by the Selous Scouts during the Rhodesian Bush War
.
Based on animal studies, parathion is considered by the U.S. Environmental Protection Agency to be a possible human carcinogen
. Studies show that parathion is toxic to fetuses, but does not cause birth defects.
It is classified as a UNEP Persistent Organic Pollutant
and WHO
Toxicity Class
, "Ia, Extremely Hazardous".
Parathion is very toxic to bees, fish
, bird
s, and other forms of wildlife. Parathion can be replaced by many safer and less toxic alternatives (less toxic organophosphate
s, carbamate
s, or synthetic pyrethroid
s).
or PAN, parathion is one of the most dangerous pesticides. This organization lists parathion also as a 'bad actor chemical'. In the US alone more than 650 agricultural workers have been poisoned since 1966, of which 100 died. In underdeveloped countries many more people have suffered fatal and nonfatal intoxications. The World Health Organization
, PAN and numerous environmental organisations propose a general and global ban. Its use is banned or restricted in 23 countries and its import is illegal in a total of 50 countries.
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
and acaricide. It was originally developed by IG Farben
IG Farben
I.G. Farbenindustrie AG was a German chemical industry conglomerate. Its name is taken from Interessen-Gemeinschaft Farbenindustrie AG . The company was formed in 1925 from a number of major companies that had been working together closely since World War I...
in the 1940s. It is highly toxic to non-target organisms, including humans. Its use is banned or restricted in many countries, and there are proposals to ban it from all use. Closely related is "methyl parathion" (see below).
Parathion-methyl
"Parathion-methyl" (CAS#298-00-0), also known as methyl parathion or dimethyl parathion, was also developed and is marketed for similar uses. It is a distinct compound with diminished toxicity. Some trade names of parathion-methyl include Bladan M, Metaphos, ME605, and E601.History
Parathion was developed by Dr. Gerhard SchraderGerhard Schrader
Dr. Gerhard Schrader was a German chemist specializing in the discovery of new insecticides, hoping to make progress in the fight against hunger in the world. However, Dr...
for the German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
trust IG Farben
IG Farben
I.G. Farbenindustrie AG was a German chemical industry conglomerate. Its name is taken from Interessen-Gemeinschaft Farbenindustrie AG . The company was formed in 1925 from a number of major companies that had been working together closely since World War I...
in the 1940s. After the war and the collapse of IG Farben due to the war crime trials, the Western allies seized the patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
, and parathion was marketed worldwide by different companies and under different brand names. The most common German brand was E605 (banned in Germany after 2002); this was not a food-additive "E number
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...
" as used in the EU today. "E" stands for Entwicklungsnummer (German for "development number").
Handling properties
When pure, parathion is a white crystalline solid, however it is commonly distributed as a brown liquidLiquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
that smells of rotting egg
Egg (food)
Eggs are laid by females of many different species, including birds, reptiles, amphibians, and fish, and have probably been eaten by mankind for millennia. Bird and reptile eggs consist of a protective eggshell, albumen , and vitellus , contained within various thin membranes...
s or garlic
Garlic
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...
. The insecticide is more or less stable, although it darkens when exposed to sunlight.
Industrial synthesis
Parathion is synthesized from diethyl dithiophosphoric acid (C2H5O)2PS2H, which is obtained by treatment of P2S5Phosphorus pentasulfide
Phosphorus pentasulfide is the inorganic compound with the formula P4S10. This yellow solid is the one of two phosphorus sulfides of commercial value...
with ethanol (methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
is used to prepare methyl parathion). Diethyl dithiophosphoric acid is chlorinated to generate diethylthiophosphoryl chloride. The diethyl dithiophosphoric acid is then treated with sodium 4-nitrophenolate (the sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
salt of 4-nitrophenol
4-Nitrophenol
4-Nitrophenol is a phenolic compound that has a nitro group at the opposite position of hydroxy group on the benzene ring.-Properties:...
).
- 2 (C2H5O)2P(S)SH + 3 Cl2 → 2 (C2H5O)2P(S)Cl + S2Cl2 + 2 HCl
- (C2H5O)2P(S)Cl + NaOC6H4NO2 → (C2H5O)2P(S)OC6H4NO2 + NaCl
Applications
As a pesticide, parathion is generally applied by spraying. It is often applied to cottonCotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
, rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
and fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
trees. The usual concentrations of ready-to-use solutions are 0.05 to 0.1%. The chemical is banned for use on many food crops.
Insecticidal activity
Parathion acts on the enzyme acetylcholinesteraseAcetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...
, but indirectly. After being ingested by insects (and unintentionally, by humans), the parathion becomes oxidized by oxidase
Oxidase
An oxidase is any enzyme that catalyzes an oxidation-reduction reaction involving molecular oxygen as the electron acceptor. In these reactions, oxygen is reduced to water or hydrogen peroxide ....
s to give paraoxon
Paraoxon
Paraoxon is a parasympathomimetic which acts as an acetylcholinesterase inhibitor. It is an organophosphate oxon, and the active metabolite of the insecticide parathion. It is also used as an ophthalmological drug against glaucoma...
, replacing the double bonded sulfur with oxygen.
2P(S)OC6H4NO2 + 1/2 O2 → (C2H5O)2P(O)OC6H4NO2 + S
The phosphate ester is more reactive in organisms than the phosphorothiolate ester, as the phosphorus atoms become much more electronegative.
Degradation
Degradation of parathion leads to more water soluble products. HydrolysisHydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
, which deactivates the molecule, occurs at the aryl ester bond resulting in diethyl thiophosphate and 4-nitrophenol
4-Nitrophenol
4-Nitrophenol is a phenolic compound that has a nitro group at the opposite position of hydroxy group on the benzene ring.-Properties:...
.2P(S)OC6H4NO2 + H2O → HOC6H4NO2 + (C2H5O)2P(S)OH
Degradation proceeds differently under anaerobic conditions: the nitro group on parathion is reduced to the amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
.2P(S)OC6H4NO2 + 6 H → (C2H5O)2P(S)OC6H4NH2 + 2 H2O
Safety
Parathion is a cholinesterase inhibitor. It generally disrupts the nervous systemNervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
by inhibiting the acetylcholinesterase
Acetylcholinesterase
"Acetylcholinesterase, also known as AChE or acetylcholine acetylhydrolase, is an enzyme that degrades the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic nervous system, where its activity serves to terminate...
. It is absorbed via skin, mucous membranes, and orally. Absorbed parathion is rapidly metabolized to paraoxon, as described above. Paraoxon exposure can result in headache
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
s, convulsions, poor vision, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, abdominal pain, severe diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
, unconsciousness
Unconsciousness
Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...
, tremor
Tremor
A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving to-and-fro movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the...
, dyspnea
Dyspnea
Dyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...
, and finally lung-edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
as well as respiratory arrest. Symptoms of poisoning are known to last for extended periods of time, sometimes months. The most common and very specific antidote is atropine
Atropine
Atropine is a naturally occurring tropane alkaloid extracted from deadly nightshade , Jimson weed , mandrake and other plants of the family Solanaceae. It is a secondary metabolite of these plants and serves as a drug with a wide variety of effects...
in doses of up to 100 mg daily. Because atropine may also be toxic, it is recommended that small frequently repeated doses be used in treatment. If human poisoning is detected early and the treatment is prompt (atropine and artificial respiration), fatalities are infrequent. Insufficient oxygen will lead to cerebral hypoxia
Cerebral hypoxia
Cerebral hypoxia refers to a reduced supply of oxygen to the brain. Cerebral anoxia refers to a complete lack of oxygen to the brain. There are four separate categories of cerebral hypoxia; in order of severity they are; diffuse cerebral hypoxia , focal cerebral ischemia, cerebral infarction, and...
and permanent brain damage. Peripheral neuropathy
Peripheral neuropathy
Peripheral neuropathy is the term for damage to nerves of the peripheral nervous system, which may be caused either by diseases of or trauma to the nerve or the side-effects of systemic illness....
including paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
is noticed as late sequelae after recovery from acute intoxication. Parathion has been used for committing suicide and deliberately poisoning other persons. It is known as "Schwiegermuttergift" (mother-in-law poison) in Germany. For this reason most formulations contain a blue dye providing warning.
Parathion has been used as a chemical weapon, most notably by the Selous Scouts during the Rhodesian Bush War
Rhodesian Bush War
The Rhodesian Bush War – also known as the Second Chimurenga or the Zimbabwe War of Liberation – was a civil war which took place between July 1964 and December 1979 in the unrecognised country of Rhodesia...
.
Based on animal studies, parathion is considered by the U.S. Environmental Protection Agency to be a possible human carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
. Studies show that parathion is toxic to fetuses, but does not cause birth defects.
It is classified as a UNEP Persistent Organic Pollutant
Persistent organic pollutant
thumb|right|275px|State parties to the Stockholm Convention on Persistent Organic PollutantsPersistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes...
and WHO
Who
Who may refer to:* Who , an English-language pronoun* who , a Unix command* Who?, one of the Five Ws in journalism- Art and entertainment :* Who? , a 1958 novel by Algis Budrys...
Toxicity Class
Toxicity Class
Toxicity Class refers to a classification system for pesticides that has been created by a national or international government-related or -sponsored organization...
, "Ia, Extremely Hazardous".
Parathion is very toxic to bees, fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, and other forms of wildlife. Parathion can be replaced by many safer and less toxic alternatives (less toxic organophosphate
Organophosphate
An organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...
s, carbamate
Carbamate
Carbamates are organic compounds derived from carbamic acid . A carbamate group, carbamate ester, and carbamic acids are functional groups that are inter-related structurally and often are interconverted chemically. Carbamate esters are also called urethanes.-Synthesis:Carbamic acids are derived...
s, or synthetic pyrethroid
Pyrethroid
A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums . Pyrethroids now constitute a major commercial household insecticides...
s).
Protection against poisoning
To assure human protection the end user must wear protective gloves, clothing, and a respirator of the organic-vapour. Industrial safety during the production process requires special ventilation and continuous measurement of air contamination in order not to exceed PEL levels as well as keeping personal hygiene. Frequent determination of workers' serum acetylcholinesterase activity is also helpful in regards of occupational safety, because the action of parathion is cumulative. If an area of the body is contaminated with parathion, if possible, it should be removed immediately. Also, atropine has been used as a specific antidote.Proposals to ban
According to the non-governmental organisation Pesticide Action NetworkPesticide Action Network
Pesticide Action Network is "an international coaltion of around 600 NGOs, citizens' groups, and individuals in about 60 countries."PAN is involved in fighting problems caused by pesticide use, and advocates ecologically sound alternatives. Branches include PAN North America, U...
or PAN, parathion is one of the most dangerous pesticides. This organization lists parathion also as a 'bad actor chemical'. In the US alone more than 650 agricultural workers have been poisoned since 1966, of which 100 died. In underdeveloped countries many more people have suffered fatal and nonfatal intoxications. The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
, PAN and numerous environmental organisations propose a general and global ban. Its use is banned or restricted in 23 countries and its import is illegal in a total of 50 countries.
External links
- ATSDR - Methyl Parathion Expert Panel Report U.S. Department of Health and Human Services (public domain)
- Ethyl parathion:
- Methyl parathion: