Investigation of the effect of different processes on the pesticide residues of diazinon, pirimicarb, dimethoate and deltamethrin in wheat

Cereals, particularly wheat, are staple foods that provide essential nutrients and energy for the human diet. However, the extensive use of pesticides to protect wheat crops against pests raises serious concerns due to the persistence of their residues in food products, especially bread as a high-consumption commodity. This study aimed to evaluate the impact of different processing stages, including milling, dough preparation, and bread baking, on the residues of diazinon, pirimicarb, dimethoate, and deltamethrin in wheat. Wheat samples were collected from a flour factory in Tehran, Iran, and subjected to standard bread-making processes. Residue extraction was performed using the QuEChERS method, followed by quantification with gas chromatography–mass spectrometry (GC-MS). The initial concentrations of diazinon, pirimicarb, dimethoate, and deltamethrin in wheat were 0.862, 0.194, 0.703, and 3.211 mg/kg, respectively. Processing significantly reduced pesticide levels (p < 0.05), with overall reductions of 94.55% (diazinon), 90.21% (pirimicarb), 92.32% (dimethoate), and 63.78% (deltamethrin). All processing factors were <1, indicating effective dissipation across the stages, with the greatest reduction observed in diazinon and the lowest in deltamethrin. These findings demonstrate that bread-making substantially decreases pesticide residues, thereby reducing potential dietary exposure risks. Nonetheless, the relatively lower reduction of deltamethrin highlights the need for stricter monitoring and improved pre-harvest management practices to ensure consumer safety.