Abstract
Water-soluble and insoluble fractions of airborne particulate matter (PM) exhibit different toxicological potentials and peculiar mechanisms of action in biological systems. However, most of the research on the oxidative potential (OP) of PM is focused exclusively on its water-soluble fraction, since experimental criticisms were encountered for detaching the whole PM (soluble and insoluble species) from field filters. However, to estimate the actual potential effects of PM on human health, it is essential to assess the OP of both its water-soluble and insoluble fractions. In this study, to estimate the total OP (TOP), an efficient method for the detachment of intact PM10 from field filters by using an electrical toothbrush was applied to 20 PM10 filters in order to obtain PM10 water suspensions to be used for the DCFH, AA and DTT oxidative potential assays (OPDCFH, OPAA and OPDTT). The contribution of the insoluble PM10 to the TOP was evaluated by comparing the TOP values to those obtained by applying the three OP assays to the water-soluble fraction of 20 equivalent PM10 filters. The OP of the insoluble fraction (IOP) was calculated as the difference between the TOP and the WSOP. Moreover, each PM10 sample was analyzed for the water-soluble and insoluble fractions of 10 elements (Al, Cr, Cs, Cu, Fe, Li, Ni, Rb, Sb, Sn) identified as primary elemental tracers of the main emission sources in the study area. A principal component analysis (PCA) was performed on the data obtained to identify the predominant sources for the determination of TOP, WSOP, and IOP. Results showed that water-soluble PM10 released by traffic, steel plant, and biomass burning is mainly responsible for the generation of the TOP as well as of the WSOP. This evidence gave strength to the reliability of the results from OP assays performed only on the water-soluble fraction of PM. Lastly, the IOPDCFH and IOPDTT were found to be principally determined by insoluble PM10 from mineral dust.
Highlights
Air pollution is widely recognized as a key topic in public health protection actions [1,2]
The contribution of the PM10 insoluble fraction to the total OP (TOP) was assessed comparing the results obtained by the OPDCFH, oxidative potential (TOP); ascorbic acid (OPAA), and OPDTT assays performed on the water-soluble fraction of PM10 (WSOP) to the results achieved by applying the three assays to the aqueous suspension of intact PM10
Results show that all the three oxidative potential (OP) assays for the water-soluble OP (WSOP) and TOP are included in the group of traffic and steel plant water-soluble tracers and in the same direction of biomass burning elemental tracers along PC2
Summary
Air pollution is widely recognized as a key topic in public health protection actions [1,2]. Exposure to particulate matter (PM) is one of the major global health concerns [3,4], since it may adversely affect human health, leading to the development of several chronic and acute pathologies, such as cardiovascular and respiratory diseases, lung cancer, bronchitis, diabetes, and neurodevelopmental disorders [5,6,7,8]. The main cytotoxicity mechanism involved in developing damaging health effects and promoting chronic diseases is the ability of PM to induce oxidative stress, due to the interaction between cells and particles and the production of excess reactive species, such as reactive oxygen species (ROS), reactive nitrogen species (RNS) and reactive carbon species (RCS), which can upset the balance of intracellular oxidants and antioxidants [11,12,13]. PM can trigger oxidative responses by different pathways, such as the introduction of particlebound ROS into the respiratory system, or the introduction of redox-active species inducing the catalytic generation of reactive species and, the depletion of antioxidants [14,15,16]
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