Parathion, also called parathion-ethyl or diethyl parathion, is an organophosphate insecticide and acaricide. It was originally developed by IG Farben in the 1940s. It is highly toxic to non-target organisms, including humans, so its use has been banned or restricted in most countries. In response to safety concerns, the less toxic but still dangerous analogue parathion methyl was later developed.[6]
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| Names | |
|---|---|
| Preferred IUPAC name
O,O-Diethyl O-(4-nitrophenyl) phosphorothioate | |
| Other names
E605 | |
| Identifiers | |
3D model (JSmol) |
|
| 2059093 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.000.247 |
| EC Number |
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| KEGG | |
PubChem CID |
|
| RTECS number |
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| UNII | |
| UN number | 3018 2783 |
CompTox Dashboard (EPA) |
|
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| Properties[1] | |
| C10H14NO5PS | |
| Molar mass | 291.26 g·mol−1 |
| Appearance | Yellow liquid |
| Density | 1.2681 g⋅cm−3 (20 °C (68 °F)) |
| Melting point | 5.2–7.0 °C (41.4–44.6 °F; 278.3–280.1 K) |
| Boiling point | 375 °C (707 °F; 648 K) Decomposes over 100 °C (212 °F) |
| 1.29 mg/100 mL (20 °C (68 °F)) | |
| Solubility |
|
| log P | 3.83 |
| Vapor pressure | 3.78×10−5 mmHg (5.04×10−3 Pa) (68 °F (20 °C))[2] |
Refractive index (nD) |
1.537 |
| Hazards | |
| GHS labelling:[3] | |
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| Danger | |
| H300+H310+H330, H372, H410 | |
| P260, P262, P264, P270, P271, P273, P280, P284, P301+P310+P330, P302+P350+P310, P304+P340+P310, P314, P362, P391, P403+P233, P405, P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | 120 °C (248 °F; 393 K)[3] |
Threshold limit value (TLV) |
0.1 mg/m3[2] (TWA) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
|
LC50 (median concentration) |
84 mg/m3 (rat, 4 hr)[4] |
LCLo (lowest published) |
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| NIOSH (US health exposure limits):[5] | |
PEL (Permissible) |
TWA 0.1 mg/m3 [skin] |
REL (Recommended) |
TWA 0.05 mg/m3 [skin] |
IDLH (Immediate danger) |
10 mg/m3 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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History
edit
Parathion was developed by Gerhard Schrader for the German trust IG Farben in the 1940s. After World War II 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"). It is an irreversible acetylcholinesterase inhibitor.
Handling properties
editIt is commonly distributed as a brown liquid that smells of rotting eggs or garlic.[citation needed] The insecticide is somewhat stable, although it darkens when exposed to sunlight.[citation needed]
Industrial synthesis
editParathion is synthesized from diethyl dithiophosphoric acid (C2H5O)2PS2H by chlorination to generate diethylthiophosphoryl chloride ((C2H5O)2P(S)Cl), and then the chloride is treated with sodium 4-nitrophenolate (the sodium salt of 4-nitrophenol).[8]
- 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
editAs a pesticide, parathion is generally applied by spraying. It is often applied to cotton, 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.[citation needed]
Insecticidal activity
editParathion acts on the enzyme acetylcholinesterase indirectly. After an insect (or a human) ingests parathion, an oxidase replaces the double bonded sulfur with oxygen to give paraoxon.[9]
- (C2H5O)2P(S)OC6H4NO2 +1/2O2 → (C2H5O)2P(O)OC6H4NO2 + S
The phosphate ester is more reactive in organisms than the phosphorothiolate ester, as the phosphorus atoms become much more electropositive.[9]
Parathion resistance is a special case of acetylcholinesterase inhibitor resistance.[citation needed]
Parathion is toxic to most forms of wildlife in addition to insects if not applied at correct concentrations.[10]
Degradation
editDegradation of parathion leads to more water-soluble products. Hydrolysis, which deactivates the molecule, occurs at the aryl ester bond resulting in diethyl thiophosphate and 4-nitrophenol:[9]
- (C2H5O)2P(S)OC6H4NO2 + H2O → HOC6H4NO2 + (C2H5O)2P(O)SH
Degradation proceeds differently under anaerobic conditions: the nitro group on parathion is reduced to the amine:[9]
- (C2H5O)2P(S)OC6H4NO2 + 6 H → (C2H5O)2P(S)OC6H4NH2 + 2 H2O
Illicit uses
editAs a chemical weapon
editParathion was used as a chemical warfare agent, most notably by an element of the British South Africa Police attached to the Selous Scouts during the Rhodesian Bush War. They used it to poison clothing that was then supplied to anti-government guerrillas. When the enemy soldiers put on the clothes, they were poisoned by absorption through the skin.[11][12]
Use in suicides
editParathion was commonly used for suicides in the 1950s and 1960s.[13]
Safety
editParathion disrupts the nervous system by inhibiting acetylcholinesterase. It is absorbed via skin, mucous membranes, and orally. Absorbed parathion is rapidly metabolized to paraoxon. Exposure can result in headaches, convulsions, poor vision, vomiting, abdominal pain, severe diarrhea, unconsciousness, tremor, dyspnea, and finally pulmonary edema as well as respiratory arrest. Symptoms of poisoning are known to last for extended periods, 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.[citation needed]
Based on animal studies, parathion is considered by the U.S. Environmental Protection Agency to be a possible human carcinogen.[14] Studies show that parathion is toxic to fetuses, but does not cause birth defects.[10]
It is classified by the United Nations Environment Programme as a persistent organic pollutant[15] and by the World Health Organization as Toxicity Class Ia (extremely hazardous).[16]
See also
editReferences
edit- ↑ Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). Boca Raton, Florida: CRC Press. pp. 3–434. ISBN 9781498754293.
- 1 2 3 "Chemical Datasheet - Parathion". cameochemicals.noaa.gov. National Oceanic and Atmospheric Administration | CAMEO Chemicals. Retrieved 14 May 2026.
- 1 2 "SDS - Parathion" (pdf). www.sigmaaldrich.com. 6.16. Millipore Sigma. 25 December 2025. pp. 2–3. Retrieved 14 May 2026.
- 1 2 3 "Parathion". Immediately Dangerous to Life or Health Concentrations. National Institute for Occupational Safety and Health.
- ↑ "NIOSH Pocket Guide to Chemical Hazards".
- ↑ Mirer, Franklin E.; Levine, Barry S.; Murphy, Sheldon D. (10 January 1977). "Parathion and methyl parathion toxicity and metabolism in piperonyl butoxide and diethyl maleate pretreated mice". Chemico-Biological Interactions. 17 (1): 99–112. Bibcode:1977CBI....17...99M. doi:10.1016/0009-2797(77)90075-8. PMID 872271.
- ↑ [https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32001D0520 Directive 2001/520/EEC of 9 July 2001 of the European Parliament and of the Council Concerning the non-inclusion of parathion in AnnexI to Council Directive 91/414/EEC and the withdrawal of authorisations for plant protection products containing this active substance]
- ↑ Fee, D. C.; Gard, D. R.; Yang, C. (2005), "Phosphorus Compounds", Kirk-Othmer Encyclopedia of Chemical Technology, New York: John Wiley, doi:10.1002/0471238961.16081519060505.a01.pub2, ISBN 9780471238966
- 1 2 3 4 Metcalf, R. L. (2002). "Insect Control". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a14_263. ISBN 978-3-527-30673-2.
- 1 2 "Pesticide Information Profiles - Parathion". Extension Toxicology Network. Oregon State University. September 1993.
- ↑ "Poison in Rhodesia" (PDF). 31 January 2019.
- ↑ Cross, Glenn (2017). Dirty War: Rhodesia and Chemical Biological Warfare, 1975–1980. Solihull, UK: Helion & Company. ISBN 978-1-911512-12-7.
- ↑ Carson, Rachel. Silent Spring. HarperCollins. ISBN 978-0-547-52762-8. OCLC 1346358856.
- ↑ "Parathion". Integrated Risk Information System. U. S. Environmental Protection Agency. 26 January 2007. Archived from the original on August 23, 2000.
- ↑ Sah, Ram Charitra; Joshi, Keshab Raj (2011). Fact Sheet of 22 Persistent Organic Pollutants under Stockholm Convention (PDF). Lalitpur, Nepal: Center for Public Health and Environmental Development (CEPHED). pp. 19, 20, 53, 101. ISBN 978-9937-8479-1-9. Retrieved 15 August 2025.
- ↑ Besil, Natalia; Rezende, Sofia (2024). "Parathion". In Wexler, Philip (ed.). Encyclopedia of Toxicology. Vol. 7 (Fourth ed.). Elsevier. pp. 283–287. doi:10.1016/B978-0-12-824315-2.00888-5. ISBN 9780123864550.
External links
edit- Parathion in the Pesticide Properties DataBase (PPDB)
- ATSDR - Methyl Parathion Expert Panel Report Archived 2019-06-14 at the Wayback Machine U.S. Department of Health and Human Services (public domain)
- CDC - NIOSH Pocket Guide to Chemical Hazards U.S. Department of Health and Human Services (public domain)
- Ethyl parathion: International Chemical Safety Card 0006
- Methyl parathion: International Chemical Safety Card 0626