Pesticide residues in nectar, pollen, and beebread matrices from rapeseed (Brassica napus L.): Which matrix is associated with the highest risks to the honey bee (Apis mellifera L.)?

This study investigated pesticide residues in nectar, pollen, and beebread samples collected from 17 apiaries situated near rapeseed fields in Golestan province, Iran. A total of 54 pesticides, including all those registered for use in the region within the past five years, were analyzed using UHPLC-MS/MS following QuEChERS extraction. A total of 19, 21, and 18 pesticides were detected in nectar, pollen, and beebread, respectively. While overall pesticide concentrations were similar across matrices, distinct pesticide distributions were observed. Fungicides (propiconazole, thiophanate-methyl, tebuconazole, and carbendazim), along with organophosphate and neonicotinoid insecticides, were more prevalent in beebread compared to pollen or nectar. Hazard quotients (HQs) and risk quotients (RQs) were calculated to evaluate potential risks to honey bees. Maximum HQ values for nectar, pollen, and beebread ranged from <0.01 to 5690.80, <0.01 to 4589.61, and <0.01 to 13,090.78, respectively. Diazinon, imidacloprid, and propiconazole exhibited the highest HQ values. Pollen and beebread samples were associated with the highest risks to honey bees, exhibiting a higher number of pesticides with HQs >50 and higher overall HQ values. RQ values revealed that diazinon and imidacloprid exceeded the level of concern for forager bees and drones, while diazinon posed a risk to nurse bees. Our findings highlight the potential exposure of honey bees to pesticide residues from rapeseed fields and emphasize the need for strategies to mitigate these risks.