Persistence of fenthion residues in olive oil

The level of fenthion residues was followed for up to one year in olive oil samples. The concentration of the parent compound decreased slowly following a double‐phase first‐order decay model, both in the freezer and laboratory, while the total concentration (parent compound and its sulfoxide) remained unchanged. Storage, therefore, cannot be used as a decontamination technique for oil containing higher than the toxicologically acceptable residues of this compound.