Parathion methyl, or methyl parathion, is an organophosphate insecticide, possessing an

organothiophosphate Organothiophosphates or organophosphorothioates are a subclass of organophosphorus compounds. Many are used as pesticides, some have medical applications, and some are used as oil additives. They generally have the chemical formula (RO)3PS, RO)2 ...

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.

Applications

Parathion methyl is used as an insecticide on crops, including

cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...

Trade Names

Penncap-M, Metacide

Safety

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 Acetylcholinesterase inhibitors (AChEIs) also often called cholinesterase inhibitors, inhibit the enzyme acetylcholinesterase from breaking down the neurotransmitter acetylcholine into choline and acetate, thereby increasing both the level and ...

, symptoms of exposure to parathion methyl include irritated eyes and skin, nausea and vomiting, abdominal pain,

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

, salivation, feeling weak and tired, headache,

runny nose Rhinorrhea, rhinorrhoea, or informally runny nose is the free discharge of a thin mucus fluid from the nose; it is a common condition. It is a common symptom of allergies ( hay fever) or certain viral infections, such as the common cold or COVI ...

, tightness in the chest,

blurry vision Blurred vision is an ocular symptom where vision becomes less precise and there is added difficulty to resolve fine details. Temporary blurred vision may involve dry eyes, eye infections, alcohol poisoning, hypoglycemia, or low blood pressure. ...

, pupil constriction,

irregular heartbeat Arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. A resting heart rate that is too fast – above 100 beats per minute in adults ...

, muscle twitches (fasciculation), and difficulty breathing. In the United States, the

Occupational Safety and Health Administration The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...

(OSHA) has not set a legal limit (

permissible exposure limit The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits are established by the Occupational ...

) for parathion methyl exposure in the workplace. The

National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...

(NIOSH) has set a

recommended exposure limit A recommended exposure limit (REL) is an occupational exposure limit that has been recommended by the United States National Institute for Occupational Safety and Health. The REL is a level that NIOSH believes would be protective of worker safet ...

(REL) of 0.2 mg/m³ over an 8-hour workday.

Classifications and restrictions

Parathion methyl has been restricted for many years. It is classified as Extremely Hazardous (Ia) by the

World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...

and it is classified as Severely Hazardous by the

Rotterdam Convention The Rotterdam Convention (formally, the Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade) is a multilateral treaty to promote shared responsibilities in relation ...

. 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.Annex III Chemicals
Methyl-parathion (Emulsifiable concentrates (EC) at or above 19.5% active ingredient and dusts at or above 1.5% active ingredient)
Rotterdam Convention

References

{{Authority control Acetylcholinesterase inhibitors Organophosphate insecticides Methyl esters Organothiophosphate esters