| Identification | More | [Name]
Parathion | [CAS]
56-38-2 | [Synonyms]
ACC 3422(R)
ALKRON(R)
APHAMITE(R)
BLADAN(R)
diethyl 4-nitrophenyl phosphorothionate
DNTP MIXTURE
DNTP(R)
E-605(R)
ETHYL PARATHION
ETHYLPARATHIONE
ETHYL PARATHION(R)
ETILON(R)
Folidol
FOLIDOL(R)
FOSFERNO(R)
NIRAN(R)
O,O-DIETHYL O-(4-NITROPHENYL) PHOSPHOROTHIOATE
O,O-DIETHYL-O-P-NITROPHENYL PHOSPHOROTHIOATE
O,O-Diethyl-O-(p-nitrophenyl)thionophosphate
ORTHOPHOS(R) | [EINECS(EC#)]
200-271-7 | [Molecular Formula]
C10H14NO5PS | [MDL Number]
MFCD00036219 | [Molecular Weight]
291.26 | [MOL File]
56-38-2.mol |
| Chemical Properties | Back Directory | [Appearance]
Parathion is a clear liquid when fresh; pale
yellow to dark brown liquid with a garlic-like odor.
Commercial formulations use carrier solvents that may
change the physical properties shown. | [Melting point ]
6.1°C | [Boiling point ]
375°C | [density ]
1.26 | [vapor pressure ]
0.470 at 20 °C, 0.942 at 25 °C, 1.84 at 30 °C, 3.53 at 35 °C, 6.62 at 40 °C, 12.18 at 45 °C (gassaturation method, Spencer et al., 1979) | [refractive index ]
nD25 1.5370 | [Fp ]
120 °C | [storage temp. ]
APPROX 4°C
| [solubility ]
2,900 and 2,700 g/kg in petroleum ether and heptane, respectively (Williams, 1951) | [form ]
liquid | [color ]
Pale-yellow liquid | [Water Solubility ]
Slightly soluble | [Merck ]
13,7105 | [BRN ]
8912188 | [Henry's Law Constant]
8.56 at 25 °C (wetted-wall column, Fendinger and Glotfelty, 1990) | [Exposure limits]
NIOSH REL: TWA 0.05 mg/m3, IDLH 10 mg/m3; OSHA PEL: TWA
0.1 mg/m3. | [Contact allergens]
One case was reported of a bullous contact dermatitis
due to ethylparathion. | [CAS DataBase Reference]
56-38-2(CAS DataBase Reference) | [IARC]
2B (Vol. 30, Sup 7, 112) 2017 | [NIST Chemistry Reference]
Ethyl parathion (o,o-diethyl-o-p-nitrophenylthiophosphate)(56-38-2) | [EPA Substance Registry System]
56-38-2(EPA Substance) |
| Hazard Information | Back Directory | [Chemical Properties]
Pure parathion is a pale yellow liquid with a faint odor of garlic, while technical parathion
is a deep brown to yellow liquid. It is sparingly soluble in water, but soluble in alcohols,
aromatic hydrocarbons, esters, ethers, n-hexane, dichloromethane, 2-propanol, toluene,and ketones. Parathion is one of the most acutely toxic pesticides and the US EPA has classifi
ed parathion as an RUP, meaning it should only be handled by qualifi ed, trained, and
certifi ed workers. In January 1992, the US EPA announced the cancellation of parathion for
all uses on fruit, nut, and vegetable crops.
Parathion was used for the control of pests of fruits, nuts, and vegetable crops. The only
uses retained are those on alfalfa, barley, corn, cotton, sorghum, soybeans, sunfl owers,
and wheat. Further, to reduce exposure of agricultural workers, parathion may only be
applied to these crops by commercially certifi ed aerial applicators and treated crops may
not be harvested by hand. Parathion is a broad spectrum, organophosphate pesticide used
to control many insects and mites. | [Uses]
Parathion is an organophosphate insecticide used on cotton, rice and fruit trees. | [Uses]
Insecticide; acaricide. | [General Description]
Light-yellow liquid, PARATHION MIXTURE, LIQUID(56-38-2) turn solid at 6° C, a deadly poison by all routes. Organic phosphate insecticide, acts as an inhibitor of cholinesterase. | [Reactivity Profile]
Violent reaction when PARATHION is used as solvent to dissolve endrin. When heated to decomposition PARATHION MIXTURE, LIQUID emits very toxic fumes of oxides of sulfur, phosphorus and nitrogen [Lewis, 3rd ed., 1993, p. 984]. | [Air & Water Reactions]
PARATHION MIXTURE, LIQUID is slightly soluble in water. | [Health Hazard]
Highly toxic, may be fatal if inhaled, swallowed or absorbed through skin. Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution. | [Health Hazard]
Parathion is highly toxic by all routes of exposure. Parathion, like all organophosphate
pesticides, inhibits acetylcholinesterase and alters cholinergic synaptic transmission at
neuroeffector junctions (muscarinic effects), at skeletal myoneural junctions, in autonomic
ganglia (nicotinic effects), and in the CNS. Exposures to parathion cause symptoms of poisoning
that include, but are not limited to, abdominal cramps, vomiting, diarrhea, pinpoint
pupils, blurred vision, excessive sweating, salivation and lacrimation, wheezing, excessive
tracheobronchial secretions, agitation, seizures, bradycardia or tachycardia, muscle
twitching and weakness, and urinary bladder and fecal incontinence. Seizures are much
more common in children than in adults. Severe exposures cause loss of consciousness,
coma, excessive bronchial secretions, respiratory depression, cardiac irregularity, eventually
leading to death. Occupational workers and the general public with health disorders
and abnormalities, such as cardiovascular, liver or kidney diseases, glaucoma, or CNS, are
at an increased risk of parathion poisoning. Further, high environmental temperatures
enhance the severity of parathion poisoning. | [Potential Exposure]
A severely hazardous pesticide formulation.
Those exposed include those engaged in manufacture,formulation and application of this broad spectrum insecticide.
This material has also been used as a chemical warfare agent. | [Fire Hazard]
Combustible material: may burn but does not ignite readily. Containers may explode when heated. Runoff may pollute waterways. Substance may be transported in a molten form. | [First aid]
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions, including
resuscitation mask) if breathing has stopped and CPR if
heart action has stopped. Transfer promptly to a medical
facility. When this chemical has been swallowed, get medical
attention. Give large quantities of water and induce
vomiting. Do not make an unconscious person vomit.
Medical observation is recommended for 2448 hours after
breathing overexposure, as pulmonary edema may be
delayed. As first aid for pulmonary edema, a doctor or
authorized paramedic may consider administering a drug or
other inhalation therapy. | [Shipping]
UN3278 Organophosphorus compound, liquid,
toxic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous
materials, Technical Name Required, Potential Inhalation
Hazard (Special Provision 5).UN2783 Organophosphorus
pesticides, solid, toxic, Hazard Class: 6.1; Labels:
6.1-Poisonous materials. UN3018 Organophosphorus pesticides,
liquid, toxic, Hazard Class: 6.1; Labels: 6.1-
Poisonous materials. | [Incompatibilities]
Incompatible with oxidizers (chlorates,
nitrates, peroxides, permanganates, perchlorates, chlorine,
bromine, fluorine, etc.); contact may cause fires or
explosions. Keep away from alkaline materials, strong bases,
strong acids, oxoacids, epoxides. Strong oxidizers may cause
release of toxic phosphorus oxides. Organophosphates, in
the presence of strong reducing agents such as hydrides,
may form highly toxic and flammable phosphine gas. Keep
away from alkaline materials. Attacks some plastics, rubbers,
and coatings. Rapidly hydrolyzed by alkalis. | [Description]
After exposure to parathion ethyl, one case of a bullous
contact dermatitis was reported. | [Waste Disposal]
Consult with environmental
regulatory agencies for guidance on acceptable disposal
practices. Generators of waste containing this contaminant
(≥100 kg/mo) must conform with EPA regulations
governing storage, transportation, treatment, and waste
disposal. In accordance with 40CFR165, follow recommendations
for the disposal of pesticides and pesticide
containers. Must be disposed properly by following package
label directions or by contacting your local or federal
environmental control agency, or by contacting your
regional EPA office. One manufacturer recommends the
use of a detergent in a 5% trisodium phosphate solution
for parathion disposal and cleanup problems. For parathion
disposal in general, however, the recommended
method is incineration (816°C, 0.5 second minimum for
primary combustion; 1204°C, 1.0 second for secondary
combustion) with adequate scrubbing and ash disposal
facilities. | [Physical properties]
Pale yellow to dark brown liquid with a garlic-like odor. Robeck et al. (1965) reported odor
threshold concentrations of 3 and 36 ppm for technical and pure grades, respectively. | [Definition]
ChEBI: Parathion is an organic thiophosphate, a C-nitro compound and an organothiophosphate insecticide. It has a role as an EC 3.1.1.7 (acetylcholinesterase) inhibitor, an EC 3.1.1.8 (cholinesterase) inhibitor, an acaricide, an agrochemical, an avicide and a mouse metabolite. It is functionally related to a 4-nitrophenol. | [Agricultural Uses]
Insecticide, Acaricide: The U.S. EPA announced in November, 2000, the
cancellation of ethyl parathion immediately on seed corn
and the eventual phase out for its use in other pesticide
products by the end of 2000. By the end of October, 2003,
the U.S. EPA phased out its use to control insects and mites
on alfalfa, barley, corn, canola, sorghum, soybeans, sunflowers
and wheat. Also used to control nuisance birds.
Not listed for use in EU countries. Not registered for
use in the U.S. There are 25 global suppliers. | [Trade name]
(There are 921 active and canceled/transferred
labels registered with the U.S. EPA) ACC 3422®;
ALKRON®[C]; ALLERON®; AMERICAN CYANAMID
3422®; APHAMITE®; ARALO®; B 404®; BAY
E-605®; BAYER E-605®; BLADAN®; BLADAN F®;
COMPOUND 3422®; COROTHION®; CORTHION®;
COR-THION®; DANTHION®; DREXEL PARATHION
8E®; E 605®; E 605 F®; ECATOX®; EKATIN WF
& WF ULV®; EKATOX®; ETHLON®; ETILON®;
FIGHTER®; FOLIDOL®; FOLIDOL E®; FOLIDOL
E-605®; FOLIDOL E&E 605®; FOLIDOL OIL®;
FOSFERMO®; FOSFERNO®; FOSFEX®; FOSFIVE®;
FOSOVA®; FOSTERN®; FOSTOX®; GEARPHOS®;
GENITHION®; IDA SEIS-TRES 6-3®; KALPHOS®;
KOLODUST®[C]; KYPTHION®; LETHALAIRE
G-54®; LIROTHION®; MURFOS®; MURPHOS®;
NIRAN®[C]; NIUIF 100®; NITROSTIGMINE®;
NOURITHION®; NOVAFOS-M®; OLEOFOS
20®; OLEOPARATHENE®; OLEOPARATHION®;
ORTHOPHOS®; PAC®; PACOL®; PARA-KILL®[C];
PARAMAR®; PARA-TOX®[C]; PANTHION®;
PARADUST®; PARAPHOS®; PARAWET®; PENNCAP
E®; PESTOX PLUS®; PETHION®; PHOSKIL®;
PLEOPARAPHENE®; RHODIASOL®; RHODIATOX®;
RHODIATROX®; SEIS-TRES 6-3®; SELEPHOS®;
SOPRATHION®; STATHION®; SULPHOS®; SUPER
RODIATOX®; T-47®; THIOMEX®; THIOPHOS®;
THIOPHOS® 3422; TIOFOS®; TOX 47®; TOXOL®;
VAPOPHOS®; VITREX®; WOPROPHOS® | [Carcinogenicity]
In an animal bioassay a dose-related
increase in the incidence of adrenal cortical
adenomas (with a few carcinomas at this site as
well) has been observed in one strain of rats in
both sexes. The significance of these lesions in
aged rats in unclear. Other bioassays in mice
and rats had sufficient limitations, such that the
IARC deemed them inadequate for evaluation
and concluded that there are insufficient data
to evaluate the carcinogenicity of parathion for
animals and no data for humans. | [Environmental Fate]
Biological. Initial hydrolysis products include diethyl-O-thiophosphoric acid, p-nitrophenol (Sethunathan, 1973, 1973a; Munnecke and Hsieh, 1976; Sethunathan et al., 1977;
Verschueren, 1983) and the biodegradation products p-aminoparathion and p-aminophenol
(Sethunathan, 1973; Laplanche et al., 1981; Nelson, 1982). Mixed bacterial cultures were
capable of growing on technical parathion as the sole carbon and energy source (Munnecke
and Hsieh, 1976). Three oxidative pathways were reported. The primary degradative
pathway is initial hydrolysis to yield p-nitrophenol and diethylthiophosphoric acid. The
secondary pathway involves the formation of paraoxon (diethyl p-nitrophenyl phosphate)
which subsequently undergoes hydrolysis to yield p-nitrophenol and diethylphosphoric
acid. The third degradative pathway involved reduction of parathion under low oxygen
conditions to yield p-amino-parathion followed by hydrolysis to p-aminophenol and die
A Flavobacterium sp. (ATCC 27551), isolated from rice paddy water, degraded parathion to p-nitrophenol. The microbial hydrolysis half-life of this reaction was <1 hour
(Sethunathan and Yoshida, 1973; Forrest, 1981). Sharmila et al. (1989) isolated a Baci
In both soils and water, chemical- and biological-mediated reactions transform parathion to paraoxon (Alexander, 1981). Parathion was reported to biologically hydrolyze
to p-nitrophenol in different soils under flooded conditions (Sudhakar-Barik and Sethunathan, 1978; Ferris and Lichtenstein, 1980)
p-Nitrophenol, paraoxon and three unidentified metabolites were identified in a model
ecosystem containing algae, Daphnia magna, fish, mosquito and snails (Yu and Sanborn,
1975) | [Metabolic pathway]
The structure of parathion is similar to those of methyl parathion (the
dimethylphosphoryl analogue) and fenitrothion which has a 3-methyl
group on the phenyl ring: consequently the environmental fate and
pathways for biotransformation are similar. As the first commercial
organophosphorus insecticide, many studies have been conducted on
its mechanisms of activation and degradation in a very wide range of
organisms. The following is necessarily a selection of only some of the
results which have been used to illustrate the principles of its metabolism.
The principal metabolic routes of degradation in all media are via
de-esterification to give O,O-diethyl phosphorothioate and 4-nitrophenol
and by de-ethylation to desethylparathion (a less important route).
Activation to the toxic anticholinesterase metabolite paraoxon is also a
major metabolic route in soil, plants and animals. Paraoxon is also formed
photochemically in the environment; however, it is relatively quickly
detoxified in animals and plants by esterase and base-catalysed
hydrolysis to 4-nitrophenol and diethyl phosphate. A further detoxification
mechanism, which is mainly important in the soil, and possibly in
plants and in ruminants, is reduction of the 4nitro group to yield aminoparathion.
4-Nitrophenol is conjugated in plants as the glucoside, in
insects as the glucoside and/or sulfate ester and in mammals as the
glucuronide and the sulfate ester. | [Metabolism]
The principal degradation routes of parathion in
animals, plants, and soil are dearylation and dealkylation
to give O,O-diethyl hydrogen phosphorothioate,
p-nitrophenol, and desethylparathion. Oxidative desulfuration
also occurs to form the active methabolite paraoxon,
which is quickly detoxified by hydrolysis. DT50 in soil
was 65 d. | [Degradation]
Parathion is hydrolysed very slowly in acidic media and more rapidly in
alkaline solution. The DT50, values at pH 4, 7 and 8 (22 °C) were 272,260
and 130 days, respectively. The compound isomerises on heating
(>130 °C) via a thiono-thiolo rearrangement to O,S-diethyl O-(4-
nitrophenyl) phosphorothioate (iso-parathion) (2) (PM).
Many photochemical experiments on parathion have demonstrated
paraoxon (3) as a major product. When parathion was irradiated at 350
nm in the presence of oxygen with various dicarbonyl photosensitisers,
it was oxidatively desulfurated to paraoxon (3). The singlet oxygen
generator Rose Bengal did not catalyse this reaction so it was implied that
the reaction was mediated via peroxy radicals rather than singlet oxygen
(Buckland and Davidson, 1987). A potentially important photochemical
reaction with respect to phosphorothioates is the photo-oxidation of aerosols
generated as a result of spraying since such reactions will generate
the generally more toxic oxon compounds in a medium which will be
susceptible to spray drift away from the site of application. This was
demonstrated by Woodrow ef al. (1978), who showed that the half-life
of photo-oxidation of an aerosol generated from an EC formulation of paratfuon to paraoxon (3) was as short as 2 minutes under midday
summer sunlight conditions. Other reports have demonstrated that
many other photolysis products, apart from paraoxon, are formed. In
aqueous THF or ethanol the major product of photolysis when irradiated
at wavelengths between 254 and 350 nm was O,O,S-triethyl phosphorothioate
(4). Lesser mounts of O,O,O-triethyl phosphorothioate (5)
were produced and triethyl phosphate (6) was also formed via the
photolysis of paraoxon (3). Minor photoproducts were 4-nitrophenol (7)
and ethanethiol(8) (Grunwell and Erickson, 1973). Conversely, Mansour
et al. (1983) reported that the main products of photolysis were paraoxon
(3) and 4-nitrophenol (7). Other photoproducts identified from parathion
were the thiono-thiolo rearranged products,O,s-diethyl O-(4-
nitrophenyl) (2) and O,O-diethyl S-(4-nitrophenyl) phosphorothioate (9)
(Joiner and Baetcke, 1974).
When parathion was irradiated in methanolic solution with either a
xenon arc lamp or a medium pressure mercury arc lamp filtered to
remove light of <280 nm the nature of the photoproducts was similar. Six
photoproducts were identified and the reasons for the apparent discrepancy
in other reports with respect to the main products of photodegredation
were shown to be the kinetics whereby certain products were
formed and subsequently degraded through their own photolysis. Compounds
formed in the initial stages of photolysis were paraoxon (3) and
O,O-diethyl O-phenyl phosphorothioate (10) (formed via loss of the
4-nitro group). 4-Nitrophenol (7), desethylparathion (11) and O,O,Striethyl
phosphorothioate (4) were produced in the later stages of photodegradation
after considerable decomposition of parathion had already
occurred. These products were thus likely to be the products of secondary
processes (see Scheme 1). The sixth photolysis product,O,O-diethyl
S-methyl phosphorothioate (not shown in Scheme l), was demonstrated
to be formed via the participation of the methanol solvent. Analysis of
the photolysis products was by GC-MS and 1H NMR spectroscopy (Mok
et al., 1987).
In an investigation of the effect of plant cuticle components on the
nature of parathion photolysis products, Schwack et al. (1994) incorporated
methyl 12-hydroxystearate and parathion into thin films and
analysed the products of photodegradation by HPLC separation and 1H
and 13C NMR and UV and IR spectroscopy. Under these conditions the
major products of photolysis were azoparathion (12), azoxyparathion (13)
and 2-hydroxyazoparathion (14). These dimeric products were formed via
the self-condensation of nitroso (15), hydroxylamino (16) and aminoparathion
(17) (not isolated in this experiment) generated by the sequential
photoreduction of the 4-nitro group. Subsequent photolytic hydrolysis of
(14) yielded O,O-diethyl 2,4’-dihydroxyazobenene-4-phosphorothioate
(18) and 2,4,4’-trihydroxyazobenzene (19) (Scheme 1). | [Toxicity evaluation]
The acute oral LD50 for rats is about 2 mg/kg. Inhalation LC50
(4 h) for rats is 0.03 mg/L air. NOEL (2 yr) for rats is
2 mg/kg diet (0.1 mg/kg/d). ADI is 4 μg/kg b.w. |
| Safety Data | Back Directory | [Hazard Codes ]
T+;N,N,T+,Xn,F | [Risk Statements ]
R24:Toxic in contact with skin.
R26/28:Very Toxic by inhalation and if swallowed .
R48/25:Toxic: danger of serious damage to health by prolonged exposure if swallowed .
R50/53:Very Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment .
R67:Vapors may cause drowsiness and dizziness.
R65:Harmful: May cause lung damage if swallowed.
R38:Irritating to the skin.
R11:Highly Flammable. | [Safety Statements ]
S28:After contact with skin, wash immediately with plenty of ... (to be specified by the manufacturer) .
S36/37:Wear suitable protective clothing and gloves .
S45:In case of accident or if you feel unwell, seek medical advice immediately (show label where possible) .
S60:This material and/or its container must be disposed of as hazardous waste .
S61:Avoid release to the environment. Refer to special instructions safety data sheet .
S62:If swallowed, do not induce vomiting: seek medical advice immediately and show this container or label . | [RIDADR ]
UN 3278 | [WGK Germany ]
3 | [RTECS ]
TF4550000 | [HazardClass ]
6.1(a) | [PackingGroup ]
I | [HS Code ]
29201100 | [Safety Profile]
A deadly poison by all routes. Human systemic effects by ingestion: general anesthetic; pulmonary effects; and hdney, ureter, bladder effects, true cholinesterase changes. Experimental teratogenic and reproductive effects. Questionable carcinogen with experimental carcinogenic and tumorigenic data. Human mutation data reported. A cholinesterase inhibitor. Parathon, like the other organic phosphorus poisons, acts as an irreversible inhibitor of the enzyme cholinesterase and thus allows the accumulation of large amounts of acetylcholine. When a critical level of cholinesterase depletion is reached, grave symptoms appear. Whether death is actually caused entirely by cholinesterase depletion or by the disturbance of a number of enzymes is not yet known. Recovery is apparently complete if a poisoned animal or human has time to re-form a critical amount of cholinesterase. The organism exposed remains susceptible to relatively low dosages of parathion untd the chohnesterase has regenerated. Small doses at frequent intervals are, therefore, more or less additive. There is no indication that, when recovery from a given exposure is entirely complete, the exposed organism is prejudiced in any way. Combustible when exposed to heat or flame. Violent reaction with endrin. Highly dangerous; shock can shatter the container, releasing the contents A broad spectrum insecticide in agricultural applications. When heated to decomposition it emits highly toxic fumes of NOx, POx, and SOx. | [Hazardous Substances Data]
56-38-2(Hazardous Substances Data) | [Toxicity]
LD50 in female, male rats (mg/kg): 3.6, 13 orally; 6.8, 21 dermally (Gaines) | [IDLA]
10 mg/m3 |
|