Fine and ultrafine particulate: sampling, analysis and metal characterization for a risk assessment on human health.

Information about the size-distribution of airborne particulate matter (PM) and PM-bound toxic metals is a key knowledge in terms of health concern. The global aim of the project was to characterize the mass concentration, size-distribution and metal composition in different PM2.5 size ranges. The experimental design involved the collection of size-segregated particles at an outdoor urban background site in Como during a long-term monitoring campaign by means of a multistage low pressure impactor. The highest PM concentration levels were found during the heating period because of a joint influence of meteorological factors and variations in type and number of emission sources. In particular, the greatest and significant increase effect was registered for particles between 0.15 and 1.60 μm. For chemical analysis purposes, a novel and reliable Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) measurement protocol was properly developed and optimized, providing precise and accurate results. The proposed LA-ICP-MS method was then applied for the analysis of selected trace metals (Cr, Mn, Fe, Ni, Cu, Zn, Ba and Pb) on the extended set of size-segregated PM samples. Obtained findings revealed different and characteristic metal size-distributions in the fine, submicrometer and ultrafine fractions. The studied elements were variously enriched in the particulate sizes, suggesting that local emission sources may exist for these chemical species. Moreover, from a health and sanitary perspective, the estimated hazard quotient and index values suggested no non-carcinogenic health risks via the inhalation exposure route. Also the carcinogenic risks of Cr and Ni were within the acceptability range.