Insecticide Poisoning

Definition

Insecticide poisoning is exposure to a group of chemicals designed to eradicate insects that cause affected persons to develop clinical signs that can progress to death.

Description

Insecticides belong to a group of chemicals called organophosphates used to protect against insects. Their use is popular since they are effective and do not remain in the environment, disintegrating within a few days. Organophosphates act to inhibit an enzyme in humans called acetyl cholinesterase. This enzyme functions to degrade a chemical called acetylcholine, which excites nerve cells. The resultant effect of organophosphates would be an increase in acetylcholine, thus causing initial excitation of nerve cells.

Poisoning can occur with a broad range of symptoms affecting the functioning of nerves and initial symptoms similar to the flu such as vomiting, abdominal pain, dizziness, and headache. Common names for insecticides include dichlorvos, chlorpyrifos, diazinon, fenthion, malathion, parathion, and carbamate. A special type of insecticide called paraquat is very lethal and responsible for approximately 1,000 deaths per year just in Japan. Paraquat poisoning releases oxygen free radicals that destroy lung and kidney tissues. When poisoning is suspected, a comprehensive management and assessment plan should be performed. This initial assessment should include:

• Description of toxins: names of chemical(s).
• Magnitude of exposure: determination of amount of exposure.
• Progression of symptoms: determining the progression of symptoms can provide information concerning life support and overall outcome.
• Time of exposure: knowing the time of exposure is vital since symptoms may be delayed, and it may assist to develop a management plan.
• Medical history: underlying diseases and therapeutic mediations may worsen toxic manifestations.

Causes and symptoms

Exposure to insecticides can occur by ingestion, inhalation, or exposure to skin or eyes. The chemicals are absorbed through the skin, lungs, and gastrointestinal tract and then widely distributed in tissues. Symptoms cover a broad spectrum and affect several organ systems:

• Gastrointestinal: nausea, vomiting, cramps, excess salivation, and loss of bowel movement control
• Lungs: increases in bronchial mucous secretions, coughing, wheezing, difficulty breathing, and water collection in the lungs (this can progress to breathing cessation)
• Skin: sweating
• Eyes: blurred vision, smaller sized pupil, and increased tearing
• Heart: slowed heart rate, block of the electrical conduction responsible of heartbeat, and lowered blood pressure
• Urinary system: urinary frequency and lack of control
• Central nervous system: convulsions, confusion, paralysis, and coma

Diagnosis

The confirmatory diagnosis for insecticide poisoning is the measurement of blood acetyl cholinesterase less than 50% of normal. The chemicals can also be detected by specific urine testing. Signs and symptoms in addition to a comprehensive poisoning assessment are essential for diagnosis. Carbamate insecticide poisoning exhibits symptoms similar to organophosphate poisoning but without central nervous system signs.

Treatment

Decontaminate exposed clothing and wash with soap and water immediately. Emergency measures may focus on ventilator support and heart monitoring. If inhalation is suspected, the patient should be removed from the site of exposure. If the eyes were the entry site, they should be flushed with large amounts of water. If the chemicals were ingested, the stomach may be washed out and activated charcoal may be administered. Atropine or glycopyrrolate (Robinul) is the drug of choice for carbamate insecticide poisoning. It reverses many symptoms, but is only partially effective for central nervous symptom effects such as coma and convulsions. A medication called Pralidoxime is also commonly indicated to reactivate acetylcholinesterase and to reverse typical symptoms due to organophosphate poisoning. Additionally, the patient is monitored for heart, lung, liver functioning, specific blood tests, and oxygen levels in blood.

Prognosis

Prognosis depends on the specific chemical of exposure, magnitude and time of exposure, progression of symptoms (severity), and onset for medical attention.

KEY TERMS

Acetylcholine— A chemical called a neurotransmitter that functions to excite nerve cells.

Acetylcholinesterase— An enzyme that breaks down acetylcholine.

Central nervous system— Consists of the brain and spinal cord and integrates and processes information.

Enzyme— A protein that speeds up a chemical reaction, but is not consumed during the process.

Oxygen free radicals— Reactive molecules containing oxygen and can cause cell damage.

Prevention

Adherence to accepted guidelines for handling and management is the key to preventing insecticide poisoning. These may include masks, gowns, gloves, goggles, respiratory breathing machines, or hazardous material suits.

Resources

BOOKS

Behrman, Richard E., et al, editors. Nelson Textbook. 16th ed. W. B. Saunders Company, 2000.

Goldman, Lee, et al. Cecil's Textbook of Medicine. 21st ed. W. B. Saunders Company, 2000.

Rakel, Robert E., et al. Conn's Current Therapy. 53rd ed. W. B. Saunders Company, 2001.

PERIODICALS

Blain, P. G. "Effects of Insecticides." Lancet 357 (5 May 2001).

OTHER

Material Safety Data Sheets. 〈http://oshweb.me.tut.fi〉.

National Toxicology Program. 〈http://ntp-server.niehs.nih.gov/main_Pages/NTP_ALL_STDY_PG.html〉.