Herbicide poisoning referrals to an Australian State Poisons Information Centre: a retrospective case series

Abstract

Introduction: Herbicides are chemicals used to control weeds and plants. Globally, herbicide exposures are associated with significant morbidity and mortality. However, the Australian experience is not well understood. We aimed to characterize herbicide exposures to an Australian State Poisons Centre. Methods: This is a retrospective series of all herbicide exposures referred to the Queensland Poisons Information Centre from 1 January 2018 to 31 December 2023. Data regarding demographics, exposure details and clinical features were retrieved from the unit database. Results: There were 1,833 calls regarding 1,658 patients exposed to herbicides. Most were accidental exposures 1,569 (94.6%), with 416 (25.1%) paediatric (<15 years) cases. The most common routes of exposure were dermal and oral, occurring in 827 (38.3%) and 651 (30.1%) exposures, respectively. Calls from healthcare professionals accounted for 519 (30.2%) calls. The commonest exposures were glyphosate 782 (47.2%), 2-methyl-4-chlorophenoxyacetic acid/dicamba 158 (9.5%), 2-methyl-4-chlorophenoxyacetic acid/bromoxynil 81 (4.9%) and paraquat 73 (4.4%). Most exposures 1,573 (94.9%) were asymptomatic or had mild toxicity. Only 66 (4.0%) exposures resulted in moderate to severe toxicity. There were seven deaths, following deliberate self-poisoning of paraquat (n = 3), 2-methyl-4-chlorophenoxyacetic acid/bromoxynil (n = 2) and high concentration glyphosate products (n = 2). Discussion: The pattern of poisoning in Australia may differ from other regional experiences. Deliberate herbicide exposures are uncommon, most exposures are via the dermal route, and severe toxicity is rare. Conclusions: Herbicide poisonings in Australia are mostly accidental and associated with minimal toxicity. Severe toxicity is rare and associated with deliberate self-poisonings with paraquat, 2-methyl-4-chlorophenoxyacetic acid/bromoxynil coformulation, and high concentration glyphosate products.