Microparticles contamination in urban wild bees: predominance of cellulose-derived fibres over microplastics

Anthropogenic microparticles, including synthetic microplastics (MPs), and cellulose-based materials-natural or semi-synthetic fibres-are increasingly pervasive in terrestrial ecosystems and may represent an underexplored threat to pollinators. This study investigated microparticle contamination in wild bees to evaluate their potential as bioindicators of airborne particulate pollution in urban environments. Between May and August 2024, 677 wild bee individuals from 26 genera were sampled across urbanisation gradients in two metropolitan areas of northern Italy. Microparticles adhering to bee bodies were characterised according to body position, morphology, colour, and chemical composition through stereomicroscopy and micro-FTIR analysis. A total of 3116 microparticles were detected, predominantly white fibres (69 %) located on the legs (38 %), consistent with passive accumulation during foraging and airborne exposure. Cellulose-derived materials (e.g., cellophane-like and textile-associated fibres), represented the dominant particle class, while synthetic polymers (e.g., PET, PP, PS, and PUR) occurred at lower frequencies. Larger-bodied and hairier genera (Xylocopa and Anthophora), as well as female bees, carried significantly higher microparticle loads, highlighting the role of species-specific functional traits in contaminant exposure. Microparticles were detected across all urbanisation levels, suggesting that local human activities and atmospheric transport collectively shape exposure patterns. These findings provide the first evidence that wild bee communities are broadly contaminated by diverse anthropogenic microparticles, extending beyond conventional plastics to include cellulose fibres. Wild bees therefore emerge as sensitive bioindicators of terrestrial airborne microparticle pollution, while the ecological and physiological implications of chronic exposure to both synthetic and non-synthetic particles warrant urgent further investigation.