Determination of metal(oid)s and polycyclic aromatic hydrocarbons in size-fractionated airborne particulate matter: methodological approaches, trends, gaps and future needs: a review

This review highlights a significant gap in the multi-pollutant characterisation of ultrafine particulate matter (PM <0.1 µm), focusing on metal(oid)s and polycyclic aromatic hydrocarbons (PAHs). Fractionation mechanisms, sampling protocols and analytical methods are examined with an emphasis on integrating quality assurance measures to ensure high-quality data and facilitate cross-study comparability. Based on studies published between 2010 and 2025, research has largely focused on the analysis of pollutants bound to PM 2.5 or PM 10 . Only 5% of the studies addressed ultrafine particles (UFPs), which have the greatest toxicological impacts. The measurement of both pollutant groups within a single sampling campaign was rare (14% of the studies). The reliability of analytical data was rarely evaluated. Only 33% of the studies employed certified reference materials for quality control and method validation. Microwave-assisted digestion and ultrasound-assisted extraction were commonly used for sample preparation prior to the determination of metal(oid)s and PAHs, by inductively coupled plasma mass spectrometry and gas chromatography–mass spectrometry, respectively. Both pollutant groups exhibited strong seasonal variability, with elevated concentrations observed during heating periods in cold seasons, as well as associated with fine PM and UFPs, fractions that exhibit high bioaccessibility. Smaller PM fractions were associated with anthropogenic sources, including fossil fuel and biomass combustion, traffic and industrial emissions, while coarse PM reflected naturally-derived crustal material. Overall, these findings highlight the importance of uniform and comprehensive protocols for sampling UFPs and quantifying associated pollutants, which are essential for reliable data and effective urban air quality control strategies aimed at mitigating emissions. • Chemical assessment of ultrafine particles is limited, despite their high toxicity • Simultaneous analysis of metal(oid)s and PAHs-bound PM is uncommon • Use of certified reference materials for analytical validation is rare • Strong seasonal variability was observed globally • (Ultra)fine PM links to anthropogenic sources, while coarse PM reflects crustal origin