Neurotoxic impacts of neonicotinoid pesticide residues in Chinese honey on Apis mellifera L.

Abstract

The threat to bees of neonicotinoid pesticides (NEOs) has raised concern. However, data on the disruption of the bee nervous system following long-term low-dose exposure are lacking. In this study, six NEOs were quantified in 31 honey samples from China, and their behavioral effects on bees were evaluated. Neonicotinoid pesticide detection rates ranged from 35.48% to 83.87%, with mean residue concentrations of 2.39-6.73 μg kg⁻¹. Clothianidin showed the highest detection frequency (83.87%), with an average residue of 5.54 μg kg-1. To assess neurotoxic effects at actual residue levels, bees were fed NEO-contaminated syrup for 21 days. This exposure significantly downregulated eight neurotransmitters, particularly 5-hydroxytryptamine (5-HT) and tryptophan (Trp), impairing normal physiological function. Behavioral assays showed reductions of 31.71% to 68.53% in displacement distance, 27.13% to 40.06% in movement rate, and 64.58% to 77.14% in inter-individual contact time. This study confirmed that the NEO residues in honey could hinder bees' ability to communicate and forage, with potential adverse effects on the development of bee populations. It demonstrated that bees exposed to real-world residue levels of NEOs exhibit neurological impairments. © 2025 Society of Chemical Industry.