Parathion

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Parathion

General
Systematic name	O,O-Diethyl-O-4-nitro -phenylthiophosphate
Other names	E605
Molecular formula	C₁₀H₁₄NO₅PS
SMILES	C(C)OP(OCC)(=S)Oc1 (ccc([N+1]([O-1])=O)cc1)
Molar mass	291,3 g/mol
Appearance	White crystals (pure form)
CAS number	56-38-2
Properties
Density as the solid	1,3 g/cm3
Solubility in water and organic solvents	24mg/l in water, high solubility in xylene or n-butanole
Melting point	6 C
Hazards
MSDS	[1]
OSHA Exposure Limits	PEL 0.1 mg/m3
	2 4 1
Flash point	120 °C
R Statements	R24, R26/28, R48/25, R50/53
S Statements	S28, S36/37, S45, S60, S61
RTECS number	?
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds

Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Parathion, or diethyl parathion, is a very potent insecticide and acaricide.

1 Properties and uses
2 History
3 Toxicity in humans
4 Protection against poisoning
5 Proposals to ban
6 See also
7 External links

[edit] Properties and uses

In its purest form, parathion consists of white crystals; however more commonly distributed forms take the form of a brown liquid which smells of rotting eggs or garlic. The insecticide is more or less stable, though it darkens when exposed to sunlight. It is generally applied by spraying, and often used on cotton, rice and fruit trees. Usual concentrations of the ready-to-use solutions are 0.05 to 0.1%. The chemical is banned for use on many food crops. As per 2005 at least 18 countries (e.g. many EU countries, Switzerland, Peru, Chile) have already forbidden its use in general due to its high toxicity (LD50 in men 5 to 10mg/kg) and pollutant properties. Additionally, Parathion is an experimental mutagen, teratogen, and carcinogen. It is very harmful to bees, fish, birds, and other forms of wildlife. Parathion can be replaced by many safer and less toxic alternatives (less toxic organophosphates, carbamates, or synthetic pyrethroids).

[edit] History

Parathion was developed by the German trust IG Farben in the 1940s. Dr. Gerhard Schrader was the inventor. After the war the Western allies seized the according patent and Parathion was thereafter 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 an E number (not a food additive). "E" stands for Entwicklungsnummer (German for "development number"), not for "European".

[edit] Toxicity in humans

Parathion is a cholinesterase inhibitor. It generally disrupts neural function by inhibiting the essential enzyme acetylcholinesterase. It is absorbed via skin, mucous membranes, and orally. Absorbed Parathion is rapidly metabolized to Paraoxon in which the sulfur atom is replaced by oxygen. Paraoxon exposure can result in headaches, 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 100mg daily. Because atropine may also be toxic, it is now recommended to use small doses which are frequently repeated. If human poisoning is detected early and the treatment is prompt (antidote and artificial respiration), fatalities are infrequent. Insufficient respiration may lead to cerebral hypoxia and permanent brain damage. Additionally, peripheral neuropathy including paralysis is noticed as late sequelae after recovery from acute intoxication. Parathion has been extensively used for committing suicide and deliberately killing other persons. For the latter reason most formulations contain a blue dye providing warning.

[edit] Protection against poisoning

To assure human protection the end user must wear protective gloves, clean protective clothing, and a respirator of the organic-vapour type when handling this material. He/she should bathe immediately after work. 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 may be used as a specific antidote.

[edit] Proposals to ban

According to the non-governmental organization PAN (International Pesticide Network), parathion is the most dangerous pesticide used^{[citation needed]}. PAN lists Parathion also as '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 organizations propose a general and global ban.