Definition and epidemiology
Pesticide poisoning refers to toxicity from agricultural or household chemicals used to kill insects, weeds, or rodents. The term is most often used clinically to mean organophosphate (OP) or carbamate insecticide poisoning, both of which inhibit acetylcholinesterase (AChE) and cause a cholinergic toxidrome. Other pesticide classes (pyrethroids, organochlorines, paraquat, rodenticides) cause distinct syndromes and are discussed briefly under differentials.
- Pesticide self-poisoning is a leading method of suicide globally, particularly in rural Asia, sub-Saharan Africa, and Latin America, accounting for a substantial proportion of worldwide suicide deaths.
- Occupational exposure occurs in agricultural workers through dermal contact, inhalation, or accidental ingestion.
- WHO and public health bodies have promoted bans on highly hazardous pesticides (e.g., restricting access to the most lethal OPs) as an effective suicide-prevention strategy, with measurable reductions in mortality in countries that implemented bans (e.g., Sri Lanka).
- OPs cause irreversible AChE inhibition (aging); carbamates cause reversible inhibition.
- Cholinergic toxidrome = SLUDGE/DUMBELS (muscarinic) plus fasciculations/weakness (nicotinic).
- Atropine is titrated to secretions/bronchospasm, not heart rate.
- Pralidoxime works for OPs only, not carbamates.
- Intermediate syndrome causes delayed respiratory failure 1-4 days after apparent recovery.
- Delayed polyneuropathy appears 2-3 weeks after exposure.
- Pesticide self-poisoning is a leading global suicide method; agent bans reduce mortality.
- Decontaminate before treating to prevent staff exposure.
Etiology and risk factors
- Intentional ingestion (self-poisoning): the most common cause of severe, fatal OP/carbamate toxicity worldwide.
- Occupational exposure: agricultural spraying without protective equipment, mixing concentrated formulations, contaminated clothing.
- Accidental exposure: improperly stored pesticides, pediatric ingestion, contaminated food or water.
- Risk factors: rural residence, farming occupation, easy access to concentrated agrochemicals, underlying mental health conditions (for intentional poisoning), lack of regulatory control over highly toxic formulations.
Pathophysiology
Organophosphates and carbamates inhibit acetylcholinesterase, the enzyme that normally breaks down acetylcholine (ACh) at synapses. The result is accumulation of ACh at:
- Muscarinic receptors (parasympathetic effector sites): causes secretions, bradycardia, bronchoconstriction, miosis, GI hypermotility.
- Nicotinic receptors (neuromuscular junction, sympathetic ganglia): causes muscle fasciculations, weakness, paralysis, and can cause tachycardia/hypertension early.
- CNS muscarinic and nicotinic receptors: agitation, confusion, seizures, respiratory center depression.
Key mechanistic distinction: OPs cause irreversible inhibition of AChE through covalent phosphorylation (and can undergo "aging," making the bond permanent and resistant to reactivation over time), while carbamates cause reversible, spontaneously hydrolyzing inhibition — carbamate toxicity is generally shorter-lived and does not respond to pralidoxime.
Death most often results from a combination of respiratory failure (bronchorrhea, bronchospasm, respiratory muscle weakness) and CNS depression.
Clinical features
The cholinergic toxidrome dominates the presentation. Two mnemonics capture the findings:
Muscarinic effects (SLUDGE / DUMBELS)
- Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis
- Defecation, Urination, Miosis, Bradycardia/Bronchorrhea/Bronchospasm, Emesis, Lacrimation, Salivation
Nicotinic effects
- Muscle fasciculations, cramps, weakness progressing to flaccid paralysis
- Tachycardia and hypertension can occur early (competing with muscarinic bradycardia)
CNS effects
- Agitation, confusion, seizures, coma, respiratory center depression
Timing
- Acute cholinergic crisis: within minutes to hours of exposure.
- Intermediate syndrome: proximal muscle weakness and respiratory failure occurring 24–96 hours after apparent recovery from the acute crisis; mechanism not fully understood.
- Delayed (organophosphate-induced) polyneuropathy: sensorimotor axonal neuropathy appearing 2–3 weeks after exposure, affecting distal limbs.
Diagnosis
Diagnosis is primarily clinical, based on history of exposure plus the cholinergic toxidrome. Confirmatory and supportive tests include:
- Red blood cell (RBC) acetylcholinesterase: reflects tissue AChE activity, more specific but slower to obtain.
- Plasma (pseudo)cholinesterase: more sensitive to acute exposure but less specific (also depressed in liver disease, pregnancy, genetic variants); recovers faster than RBC AChE.
- A reduction to below roughly 50% of normal baseline supports significant exposure, though absolute values vary by lab.
- ECG: may show bradycardia, QT prolongation, or arrhythmias.
- ABG and pulse oximetry: assess respiratory failure.
- Clothing/skin or gastric contents may be sent for identification of the specific agent if available.
No single rapid bedside test is universally available, so management decisions are usually made on clinical grounds without waiting for cholinesterase results.
Differential diagnosis
| Condition | Distinguishing feature |
|---|---|
| Carbamate poisoning | Similar toxidrome, shorter duration, no benefit from pralidoxime |
| Nerve agent exposure | Same mechanism as OPs, mass-casualty/military context |
| Nicotine toxicity | Nicotinic-predominant, less secretions |
| Opioid overdose | Miosis and respiratory depression but no secretions/fasciculations |
| Paraquat poisoning | Oral ulcers, delayed pulmonary fibrosis, no cholinergic signs |
| Mushroom (muscarine-containing) poisoning | Isolated muscarinic symptoms, no fasciculations |
| Sepsis/myocardial infarction | Can mimic bradycardia or GI symptoms but lacks exposure history/secretions |
Management
Management follows ABC resuscitation with specific antidotal therapy; current guidance is informed by WHO recommendations and clinical toxicology society guidelines.
Decontamination and supportive care
- Remove contaminated clothing, wash skin with soap and water; protect healthcare staff with gloves and gowns to avoid secondary exposure.
- Airway management and early intubation if respiratory failure or depressed consciousness; aggressive suctioning of secretions.
- Activated charcoal may be considered if ingestion is recent and airway is protected, though evidence of benefit is limited.
Antidotes
- Atropine: competitive muscarinic antagonist; titrated to drying of secretions and resolution of bronchospasm/bradycardia, not to a fixed heart rate — doses are repeated and escalated as needed (large cumulative doses may be required).
- Pralidoxime (2-PAM): reactivates AChE by removing the organophosphate from the enzyme if given before "aging" occurs; effective for OP poisoning, not useful in carbamate poisoning. Guideline consensus on routine use varies between regions, but it remains part of standard management in most protocols when available.
- Benzodiazepines: for seizures or severe agitation.
Disposition
- Monitor closely for intermediate syndrome (recurrent respiratory failure) over several days.
- Psychiatric evaluation and safety planning for intentional self-poisoning before discharge.
- Public health reporting for occupational exposures.
Complications and prognosis
- Respiratory failure is the leading cause of death, from combined bronchorrhea, bronchospasm, and neuromuscular weakness.
- Intermediate syndrome: delayed respiratory failure 1–4 days after initial recovery requiring ventilatory support.
- Organophosphate-induced delayed polyneuropathy: distal sensorimotor neuropathy weeks later, generally from certain OP compounds.
- Aspiration pneumonia from vomiting and secretions.
- Chronic neuropsychiatric effects are debated and not firmly established.
- Prognosis depends on the specific agent, amount ingested, and time to treatment; case fatality is markedly higher with highly toxic OP formulations and in settings with delayed access to care. Early, aggressive atropinization significantly improves survival.
DUMBELS: Defecation, Urination, Miosis, Bradycardia/Bronchorrhea/Bronchospasm, Emesis, Lacrimation, Salivation — for the muscarinic effects of cholinergic toxicity.
Practice questions
1. A 34-year-old farmworker is brought to the emergency department after being found confused in a field where he had been spraying insecticide. On exam, he has excessive salivation, lacrimation, diffuse muscle fasciculations, and a heart rate of 42/min. His pupils are 2 mm bilaterally. Which of the following is the most appropriate immediate pharmacologic treatment?
2. A 28-year-old man ingests an unknown pesticide in a suicide attempt. He develops the cholinergic toxidrome and is treated with atropine and pralidoxime with good initial response. On hospital day 3, he develops progressive proximal muscle weakness and acute respiratory distress requiring intubation, despite having been asymptomatic for the prior 24 hours. Which of the following best explains this presentation?
3. A 45-year-old woman presents after ingesting a carbamate insecticide 2 hours ago. She has excessive secretions, miosis, and bradycardia. After appropriate decontamination and atropine administration, which of the following statements about further treatment is correct?
Frequently asked questions
What causes pesticide poisoning?
Pesticide poisoning is most often caused by ingestion, inhalation, or skin absorption of organophosphate or carbamate insecticides, which inhibit acetylcholinesterase. Common scenarios include intentional self-poisoning, occupational exposure during spraying or mixing without protective equipment, and accidental ingestion of improperly stored chemicals, especially in rural agricultural settings.
What are the first symptoms of pesticide poisoning?
Early symptoms typically include excessive salivation, sweating, tearing, nausea, vomiting, and abdominal cramping, often with blurred vision from miosis. As exposure worsens, bradycardia, wheezing from bronchospasm, muscle twitching, and confusion develop, progressing to respiratory failure if untreated.
How is pesticide poisoning diagnosed?
Diagnosis is mainly clinical, based on a history of exposure combined with signs of the cholinergic toxidrome such as excessive secretions, miosis, bradycardia, and fasciculations. Blood tests measuring red blood cell acetylcholinesterase or plasma cholinesterase activity support the diagnosis but are not required before starting urgent treatment.
Is pesticide poisoning curable?
Yes, pesticide poisoning is treatable and many patients recover fully with prompt decontamination, airway support, and atropine, especially with carbamate exposure which is shorter-lived. Outcomes depend heavily on the specific agent, dose, and how quickly treatment begins; severe organophosphate poisoning carries a real risk of death or prolonged complications.
Organophosphate vs carbamate poisoning — what is the difference?
Both cause the same cholinergic toxidrome by inhibiting acetylcholinesterase, but organophosphates bind irreversibly (and can 'age,' making the bond permanent), while carbamates bind reversibly and the enzyme recovers spontaneously over hours. This means pralidoxime, which reactivates the enzyme, works for organophosphate poisoning but not for carbamate poisoning.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: T60
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.