Visualizing pesticide migration and dietary risk in lychee: Insights from tissue-specific residue analysis

Current dietary risk assessment for pesticides in fruits often assumes uniform distribution, which misrepresents the actual, localized residue profiles. This study comprehensively investigated the residue behaviors and dietary risks of 68 pesticides in lychee, focusing on tissue-specific distribution. Results showed that 15 pesticides were detected in lychee and 87.5% of the samples containing multiple residues, with the vast majority confined exclusively to the pericarp. The violation rate for maximum residue limits (MRLs) was 15% for whole fruits but only 1.25% for the pulp. Mass spectrometry imaging directly visualized the spatial distribution and migration of high-risk pesticide which revealed that post-harvest desiccation of the pericarp forms a protective barrier, effectively preventing pesticide migration into the pulp. Whole fruit posed significantly higher dietary risks (acute: 2.87-71.00×, with Cypermethrin and λ-Cyhalothrin presenting the highest multiplier; chronic: 1.43-6.93×), especially for children (cumulative risk: 1.08 vs 0.048). These findings provide spatially-resolved evidence for refining MRLs and consumer guidance, ensuring a science-based approach to lychee safety. ● 15 pesticides were detected in lychee and 87.5% of the samples containing multiple residues. ● 70% of detected pesitcides found exclusively in the pericarp. ● Post-harvest water loss of pericarp restricts the migration and penetration of pesticides into the pulp. ● The cumulative acute dietary risk from lychee samples for Chinese children was up to 108% but only 4.8% from pulp. ● The acute and chronic risks from residues in the whole fruit were 2.87–71.00 and 1.43–6.93 times higher, respectively, than those from the pulp.