An integrated pre-treatment and correlative spectroscopic approach for the identification of airborne microplastics

Microplastics (MPs) are solid plastic particles (<5 mm) that have been detected across different environmental and biological contexts. Despite their widespread presence, airborne MPs in indoor environments, including workplaces, remain poorly understood, and standardized operational protocols (SOPs) for sampling, pretreatment, and analysis are currently lacking. In this study, airborne MPs were collected in a bottling plant and subjected to an innovative pretreatment method, including pre-purification, oil-extraction, and filtration steps. The development of a customized 3D-printed holder enabled correlative micro-FTIR/micro-Raman analyses of individual particles, which, to our knowledge, has not been previously applied to airborne MPs, enhancing reliability and providing complementary chemical information. FE-SEM-EDS results revealed typical MP morphologies, including fibres, fragments, and films. Spectroscopic analyses identified a variety of polymers, dominated by polyethylene terephthalate (PET), cellophane, cotton blends, and poly (methyl methacrylate) (PMMA), as well as common surface pigments, such as indigo blue (NB1) and diarylide yellow (PY83). The polymer composition was consistent with potential sources within the bottling plant, suggesting hypothesis-driven source attribution. This study primarily focuses on the methodological approach, and the obtained results demonstrate the effectiveness of a multi-analytical workflow for airborne MPs characterization, contributing to the development of a reliable procedure for their identification in the particulate matter.