Pesticide residues in maize kernels: Monitoring and human dietary risk assessment

Abstract

The protective structure of maize husks often leads to the underestimation of pesticide residues in kernels, where limited pesticide residue data pose significant challenges for effective risk management. This large-scale investigation evaluated residue levels and dietary risks of 60 representative pesticides in maize kernels from China's three major maize production regions (358 field samples). Samples were analyzed using a QuEChERS-based pretreatment method combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Sixteen pesticides were detected, with pyraclostrobin, tebuconazole, carbendazim, triadimefon, chlorpyrifos, and fludioxonil being the most frequently detected (detection rate ≥5 %), with concentrations ranging from 1.0 to 175.9 μg/kg. Pesticide residues in maize kernels primarily originate from soil, stalks, and husks. Co-occurrence analysis revealed that 21.3 % of samples contained at least one pesticide, with up to six residues detected in a single sample. Overall, multiple pesticide co-occurrence was low, and correlations between different pesticides were weak. Probabilistic dietary risk assessment indicated that, at the 97.5th percentile exposure level, risk quotient (RQ) values ranged from 2.7 × 10⁻⁷ to 2.9 × 10⁻⁴, which were well below safety thresholds. However, pyraclostrobin, thiamethoxam, and atrazine exceeded China's maximum residue limits (MRLs) in two samples each. These findings highlight the need for continued monitoring and targeted control strategies to reduce potential dietary risks associated with pesticide residues in maize.