Guthion (Azinphos-methyl)


Guthion is the common name of an organophosphorus insecticide. It is a formulation that includes the active ingredient of azinphos-methyl. The molecular formula for azinphos-methyl is C10H12N3O3PS2. Pure guthion is a colourless to white odourless crystalline solid. Technical-grade guthion is a cream to yellow-brown granular solid. It does not occur naturally in the environment. [1,2]

Uses [3]

Guthion has been used on a variety of orchard fruits, cotton, almonds, sugarcane, and other crops; many of these uses have been cancelled and all remaining uses are scheduled to be phased out.

In the Environment [3]

  • Guthion can be released into the environment during its production and use as a pesticide.
  • Guthion is found in all environmental compartments with no pronounced tendency to partition to a particular compartment.
  • Guthion is not highly persistent in the environment; mobility in soil and sediment is moderate to low.
  • In air, guthion is relatively quickly degraded by photolysis and reaction with hydroxyl radicals; the estimated half-life is a few hours.
  • Guthion released to surface water or soil is subject to biodegradation, photolysis, and hydrolysis.
  • The half-life of guthion ranges from approximately 3 to 50 days in surface water and 32 to 150 days in soil.
  • Guthion is not expected to bioconcentrate or bioaccumulate.

Sources & Routes of Exposure

Sources of Exposure [1]

  • Food—primary source of exposure: Exposure to guthion is primarily by ingesting foods treated with this pesticide. Apples, pears, peaches, and cherries are crops most likely to contain guthion residues, but fewer residues are being found as guthion use in agriculture has been diminishing.
  • Air: Exposure may occur via air in areas close to fruit orchards or other crops where guthion is used.
  • Workplace: People who work in agricultural jobs such as pesticide applicators, fruit pickers, and other farm workers can be exposed to higher levels of guthion than the average individual, probably by skin contact with the insecticide and by inhalation.
  • Families of workers can also be exposed because residues on workers’ hands, clothes, vehicles, or other personal items can be brought into the home.
  • Children playing on or near areas that have been treated with guthion may be exposed to guthion in soil by skin contact, when they accidentally or intentionally put soil into their mouths, and through hand-to-mouth activity.

Routes of Exposure [3]

  • Inhalation – Is the predominant route of exposure for workers during production, handling, and application.
  • Oral – Is the predominant route of exposure for the general population from ingestion of contaminated drinking water and particularly food containing guthion residue.
  • Dermal – Is the predominant route of exposure for workers during production, handling, and application.

Health Effects

Acute Health Effects [5]

The following acute (short-term) health effects may occur immediately or shortly after exposure to Guthion:

  • Exposure to Guthion can cause rapid, fatal organophosphate poisoning with headache, sweating, nausea and vomiting, diarrhoea, muscle twitching, and death.
  • Breathing Guthion can irritate the lungs causing coughing and/or shortness of breath. Higher exposures can cause a build-up of fluid in the lungs (pulmonary oedema), a medical emergency, with severe shortness of breath.

  • Chronic Health Effects [5]

  • High or repeated exposure may damage the nerves causing weakness, “pins and needles,” and poor coordination in arms and legs.

  • Repeated exposure may cause personality changes of depression, anxiety or irritability.

It is not known if guthion causes cancer in humans. Guthion was not carcinogenic in male or female mice or in female rats that were fed this substance for more than 1 year. Some tumours were observed in male rats, but it could not be conclusively shown that guthion had caused the tumours. The Department of Health and Human Services (DHHS), International Agency for Research on Cancer (IARC), and EPA have not classified guthion as to its carcinogenicity. It is unknown if guthion affects the ability of humans to reproduce. Exposure to guthion did not affect fertility in animal studies.

Safety [6]

First Aid Measures

  • General: When possible, have the product container or label with you when calling a poison control centre or doctor or going for treatment.
  • Eyes: Hold eye open and rinse slowly and gently with water for 15-20 minutes. Remove contact lenses, if present, after the first 5 minutes, then continue rinsing eye. Call a physician or poison control centre immediately.
  • Skin: Wash off immediately with plenty of water for at least 15 minutes. Take off contaminated clothing and shoes immediately. Call a physician or poison control centre immediately.
  • Ingestion: Call a physician or poison control centre immediately. Rinse out mouth and give water in small sips to drink. DO NOT induce vomiting unless directed to do so by a physician or poison control centre. Never give anything by mouth to an unconscious person. Do not leave victim unattended.
  • Inhalation: Move to fresh air. If person is not breathing, call 911 or an ambulance, then give artificial respiration, preferably mouth-to-mouth if possible. Call a physician or poison control centre immediately.
  • Notes to Physician: This product is a cholinesterase inhibiting organophosphorous pesticide.
  • Treatment: Administer atropine sulfate in large therapeutic doses. Repeat as necessary to the point of tolerance. 2-PAM is also antidotal and may be administered in conjunction with atropine. The product inhibits cholinesterase resulting in stimulation of the central nervous system, the parasympathetic nervous system, and the somatic motor nerves. Do not give morphine. Watch for pulmonary oedema, which may develop in serious cases of poisoning even after 24-48 hours. At first sign of pulmonary oedema, the patient should be placed in an oxygen tent and treated symptomatically.

Exposure Controls & Personal Protection

Engineering Controls

  • Maintain exposure levels below the exposure limit through the use of general and local exhaust ventilation.

Personal Protective Equipment

The following personal protective equipment is recommended when handling guthion:

  • Eye/Face Protection: tightly fitting safety goggles
  • Hand Protection: Chemical resistant nitrile rubber gloves
  • Body Protection: Wear long-sleeved shirt and long pants and shoes plus socks.
  • Respiratory Protection: When respirators are required, select NIOSH approved equipment based on actual or potential airborne concentrations and in accordance with the appropriate regulatory standards and/or Industry recommendations.


United States [4,5]

OSHA: The Occupational Safety & Health Administration has established a legal airborne permissible exposure limit (PEL) for guthion of 0.2 mg/m3 averaged over an 8-hour workshift.

NIOSH: The National Institute for Occupational Safety & Health has set a recommended airborne exposure limit for guthion of 0.2 mg/m3 averaged over a 10-hour workshift.

ACGIH: The American Conference of Governmental Industrial Hygienists has set a recommended airborne exposure limit for guthion of 0.2 mg/m3 averaged over an 8-hour workshift.

EPA: The Environmental Protection Agency has established tolerances for guthion residues that range from 0.2 to 5 parts per million in raw agricultural commodities.

Australia [7]

Safe Work Australia: Safe Work Australia has set a Time Weighted Average (TWA) concentration for guthion of 0.2 mg/m3 averaged over an 8-hour workshift.