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.