Parathion methyl

Parathion methyl
IUPAC name
Other names
Azophos, Methyl parathion, O,O-Dimethyl O-4-nitrophenyl phosphorothioate, O,O-Dimethyl-p-nitrophenylthionophosphate
3D model (Jmol) Interactive image
ChemSpider 3987
ECHA InfoCard 100.005.501
EC Number 015-035-00-7
PubChem 4130
RTECS number TG0175000
UN number 2783
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]
0.006% (25°C)[1]
Vapor pressure 0.00001 mmHg (20°C)[1]
Main hazards reactive with strong oxidizers and water[1]
Lethal dose or concentration (LD, LC):
67 mg/kg (rat, dermal)[2]
10-25 mg/kg (male rat, oral)[3]
24 mg/kg (female rat, oral)[3]
US health exposure limits (NIOSH):
PEL (Permissible)
REL (Recommended)
TWA 0.2 mg/m3 [skin][1]
IDLH (Immediate danger)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Parathion methyl is an organophosphate pesticide and insecticide, possessing a organothiophosphate group. It is structurally very similar to parathion-ethyl.


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


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. 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]

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.[1]

Parathion methyl is not classified as a carcinogen by any global agency.[2]


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