Forensic detection and quantification of methomyl in animal stomach contents using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS) and liquid Chromatography tandem mass spectrometry (LC-MS/MS) in Japan

Pesticide poisoning in animals is a rising forensic issue due to widespread chemical use. This study analyzed stomach contents from 44 deceased animals (domestic and wild) in Japan using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS) for non-targeted screening and liquid Chromatography tandem mass spectrometry (LC-MS/MS) for quantification after Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction. Non-target screening detected multiple pesticide classes, with carbamates and herbicides being the most prevalent. Methomyl was identified in 29 cases (65.9%), with concentrations up to 157 mg/kg in cats, 75 mg/kg in a civet, and 30 mg/kg in a dog, exceeding the oral LD₅₀ of methomyl in dogs (10 mg/kg) and cats (estimated to be similar). These findings suggest acute poisoning and possible intentional misuse. The toxicological significance of methomyl highlights the need for stricter regulations, better monitoring, and increased public awareness to prevent further animal poisonings.