Management overview for herbicide poisoning
Herbicides are chemicals that kill unwanted vegetation. Many agents are available, including chlorophenoxy herbicides, diquat, dicamba, glyphosate, paraquat, bromoxynil and propanil.
The majority of herbicide poisonings are caused by glyphosate; however, all concentrated herbicide solutions can cause severe toxicity after deliberate ingestion. Even when active herbicidal ingredients are relatively nontoxic, coformulation with other substances, particularly surfactants and toxic alcohols, results in significant toxicity.
It is important to identify which herbicide is implicated in a poisoning, as toxicity differs between agents:
- chlorophenoxy and bromoxynil herbicides—muscle fasciculations, rhabdomyolysis; uncoupling of oxidative phosphorylation, characterised by tachycardia, tachypnoea and fever; metabolic acidosis
- paraquat—severe oxidative stress, oropharyngeal burns, mediastinitis, kidney injury, pneumonitis, progressive pulmonary fibrosis
- propanil—severe methaemoglobinaemia, haemolysis
- glyphosate—gastrointestinal toxicity, liver and kidney dysfunction, metabolic acidosis.
Sudden death can occur more than 24 hours after ingestion of chlorophenoxy herbicides and bromoxynil in patients who do not initially appear to be severely affected.
If herbicide poisoning is suspected, particularly involving deliberate ingestions, urgently contact a clinical toxicologist or poisons information centre (13 11 26). Specific management advice is given for poisonings due to the following herbicides, which have particular management issues or can cause serious or life-threatening toxicity:
For all other herbicide poisonings, follow the advice in this monograph. Management is primarily supportive care.