Guthion is an alternative trade name for azinphos-methyl, a broad-spectrum organophosphate insecticide once widely applied to fruit, vegetable and nut crops. Like other organophosphates it acts by inhibiting acetylcholinesterase, making it acutely toxic to humans as well as target pests. Concerns over dietary exposure, worker safety and environmental persistence led regulators in the EU, USA and many other countries to cancel or severely restrict its registrations. Its history illustrates the regulatory trajectory of older insecticides: effective crop protection weighed against residue risks, with maximum residue limits enforced during the phase-out and monitoring continuing on imported produce from regions where it may still be used.