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Atmospheric deposition of microplastics in a semi-urban environment: insights into interferences and reproducibility of mass-based analysis

Microplastics and Nanoplastics 2026
Tatu Martinmäki, Sanna Saarikoski, Hilkka Timonen, Olga Sozinova, Markus Sillanpää

Summary

Researchers measured how much plastic dust actually falls from the air in a Finnish city, finding that tiny plastic particles—mostly from packaging materials and synthetic fabrics—settle at a rate of about 50-100 micrograms per square meter daily, meaning these particles are in the air we breathe every day. This matters because it gives us more reliable, direct measurements (rather than estimates) of how much airborne microplastic we're exposed to, which is a necessary first step before scientists can fully understand the health risks of inhaling these particles.

Abstract Current knowledge about the environmental loading of microplastics via atmospheric deposition is predominantly based on number-based data which has been used to estimate mass deposition. The aim of this study was to determine mass-based atmospheric deposition rates, with an emphasis on uncertainties related to the sampling and analysis of inhalable microplastics in a semi-urban environment in Helsinki, Finland. Atmospheric deposition samples were collected during a six-week sampling campaign with four parallel samplers. Eight common polymers – polycaprolactam, polycarbonate, polyethylene, polymethylmethacrylate, polypropylene, polystyrene, polyethylene terephthalate, and styrene-butadiene rubber – were analysed by pyrolysis-gas chromatography-mass spectrometry. The total mass deposition rates of the studied polymers ranged between 50 ± 10 and 100 ± 23 µg d − 1 m − 2 . The most abundant polymer types were polyethylene, polyethylene terephthalate, and polycaprolactam, which accounted for up to 95% of the plastic polymer mass in atmospheric deposition. High reproducibilities were observed between the parallel samplers. Potential matrix interferences were identified and acknowledged in quantification of polyethylene, polyethylene terephthalate, and polyvinyl chloride. Direct mass-based determination of microplastic deposition rates reduces the uncertainties associated with sample pretreatment and conversion from number-based data.

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