Parathion methyl, or methyl parathion, is an organophosphate insecticide, possessing an organothiophosphate group. It is structurally very similar to parathion-ethyl. It is not allowed for sale and import in nearly all countries around the world, while a few allow it under subject to specified conditions only.

Quick Facts Names, Identifiers ...

Parathion methyl

Names
IUPAC name O,O-Dimethyl-O-p-nitrophenylphosphorothioate
Other names Azophos, Methyl parathion, O,O-Dimethyl O-4-nitrophenyl phosphorothioate, O,O-Dimethyl-p-nitrophenylthionophosphate
Identifiers
CAS Number	298-00-0 Y
3D model (JSmol)	Interactive image
ChemSpider	3987
ECHA InfoCard	100.005.501
EC Number	015-035-00-7
PubChem CID	4130
RTECS number	TG0175000
UNII	41BCL2O91D Y
UN number	2783
CompTox Dashboard (EPA)	DTXSID1020855
InChI InChI=1S/C8H10NO5PS/c1-12-15(16,13-2)14-8-5-3-7(4-6-8)9(10)11/h3-6H,1-2H3 Key: RLBIQVVOMOPOHC-UHFFFAOYSA-N InChI=1/C8H10NO5PS/c1-12-15(16,13-2)14-8-5-3-7(4-6-8)9(10)11/h3-6H,1-2H3 Key: RLBIQVVOMOPOHC-UHFFFAOYAW
SMILES COP(=S)(OC)Oc1ccc(cc1)[N+](=O)[O-]
Properties
Chemical formula	(CH3O)2P(S)OC6H4NO2
Molar mass	263.2 g/mol
Appearance	White to tan, crystalline solid or powder[1]
Odor	pungent, garlic-like[1]
Density	1.36 g/mL (20°C)[1]
Melting point	37 °C; 99 °F; 310 K[1]
Boiling point	143 °C; 289 °F; 416 K[1]
Solubility in water	0.006% (25°C)[1]
Vapor pressure	0.00001 mmHg (20°C)[1]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	reactive with strong oxidizers and water[1]
Lethal dose or concentration (LD, LC):
LD50 (median dose)	67 mg/kg (rat, dermal)[2] 10-25 mg/kg (male rat, oral)[3] 24 mg/kg (female rat, oral)[3]
NIOSH (US health exposure limits):
PEL (Permissible)	none[1]
REL (Recommended)	TWA 0.2 mg/m3 [skin][1]
IDLH (Immediate danger)	N.D.[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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Parathion methyl is used as an insecticide on crops, including cotton.^[2]

Penncap-M, Metacide ^[4]

People can be exposed to parathion methyl in the workplace by breathing it in, getting it on their skin, swallowing it, or getting it in their eyes. Since it is an acetylcholinesterase inhibitor, symptoms of exposure to parathion methyl include irritated eyes and skin, nausea and vomiting, abdominal pain, diarrhea, salivation, feeling weak and tired, headache, runny nose, tightness in the chest, blurry vision, pupil constriction, irregular heartbeat, muscle twitches (fasciculation), and difficulty breathing.^[5][1]

In the United States, the Occupational Safety and Health Administration (OSHA) has not set a legal limit (permissible exposure limit) for parathion methyl exposure in the workplace. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 0.2 mg/m³ over an 8-hour workday.^[1]

Parathion methyl has been restricted for many years. It is classified as Extremely Hazardous (Ia) by the World Health Organization and it is classified as Severely Hazardous by the Rotterdam Convention. It is not allowed for sale and import in nearly all countries around the world, while a few allow it under subject to specified conditions only.^[6][7][8][9]