Unintentional fatal paraquat poisonings among agricultural workers in Costa Rica: report of 15 cases.

This study analyzes the exposure circumstances of 15 fatal occupational paraquat poisonings. To evaluate the potential danger of dermal absorption and the amount needed to produce a fatal outcome in the event of oral intake, we reviewed the medical records and autopsy protocols and interviewed relatives. Five fatalities were due to ingestion of a mouthful of paraquat concentrate, and five to intake of a smaller amount; three cases were associated with dermal exposure, and in two, there was no evidence of either oral or dermal exposure. Several cases concerned diluted paraquat spray. The clinical and pathomorphological findings, including a "blinded" evaluation of lung slides, were consistent with paraquat poisoning in all cases. Difficulties in establishing the diagnosis and recognizing the exposure were identified, as well as classification of unintentional poisonings as suicides at autopsy. The findings suggest that paraquat may cause fatal poisonings by ingestion of small amounts, by dermal absorption of diluted paraquat, and possibly by inhalation. More conclusive studies are warranted.