Causes of Paraquat Overdose
Primary Routes of Exposure
Paraquat overdose occurs predominantly through intentional self-poisoning by oral ingestion, which represents the most common and lethal route of exposure. 1, 2, 3, 4
Intentional Ingestion (Most Common)
- Suicidal ingestion accounts for the vast majority of severe paraquat poisonings, particularly in developing countries where the herbicide remains accessible 1, 3
- Even minimal amounts (as little as one mouthful or 50 mg/kg) can be lethal, making intentional overdose particularly dangerous 2
- The accessibility of concentrated paraquat formulations in agricultural settings facilitates deliberate self-harm 5
Accidental Ingestion
- Accidental ingestion occurs when paraquat is transferred to unmarked containers (such as beverage bottles), leading to unintentional consumption 2
- Children may access improperly stored agricultural chemicals in households 5
- Confusion with food or beverages represents a preventable cause of poisoning 2
Alternative Routes of Exposure (Less Common, Better Prognosis)
Inhalation and Dermal Exposure
- Inhalation of paraquat aerosols during agricultural spraying carries significantly better prognosis - all 4 patients with pure inhalation exposure survived in one case series 2
- Dermal contamination through skin contact during handling or spraying operations 2
- These routes result in poor systemic absorption compared to oral ingestion 6
Intravenous Injection (Extremely Rare, Universally Fatal)
- Intravenous paraquat injection represents the most rapidly fatal route, with death occurring within 5 days despite aggressive treatment 4
- This route bypasses gastrointestinal barriers, leading to immediate systemic toxicity and fulminant multiple organ failure 4
- Toxic symptoms develop more rapidly than with oral ingestion, and prognosis is "extremely poor" 4
Occupational Exposure Context
Agricultural Workers
- Vineyard sprayers and agricultural workers face chronic low-level exposure risk 5
- Proper protective equipment failures or inadequate safety protocols contribute to occupational poisoning 5
- The herbicide has been widely used since 1962, creating ongoing exposure risk in farming communities 3
Public Health Considerations
Pesticide Access and Suicide Prevention
- Restricting access to paraquat through bans has demonstrated effectiveness in reducing suicide deaths - observational data from Sri Lanka showed decreased suicide rates after paraquat, dimethoate, and fenthion were banned 5
- Centralized storage facilities for pesticides reduced both pesticide-specific and all-cause suicide deaths 5
- Geographic regions with unrestricted paraquat availability show higher rates of fatal poisoning 5
Critical Prognostic Factors Related to Exposure
Dose-Dependent Toxicity
- Ingestion above 50 mg/kg causes death from circulatory failure within 72 hours 2
- Doses between 35-50 mg/kg result in progressive pulmonary fibrosis with delayed death 2
- Lower doses may still cause severe toxicity depending on individual factors 6, 2
Timing and Food Interaction
- The interval between ingestion and the last meal significantly affects prognosis - paraquat is adsorbed and neutralized by foodstuffs in the stomach 2
- Empty stomach at time of ingestion worsens absorption and outcome 2
Common Pitfalls in Recognition
- Healthcare providers must maintain high suspicion for paraquat poisoning in agricultural regions, even when history is unclear 5
- The absence of immediate symptoms does not exclude significant exposure - toxicity may be delayed 3
- Corrosive burns in the upper digestive tract indicate poor prognosis when present, but their absence suggests better outcomes 2