Urban PM2.5oxidative potential: Importance of chemical species and comparison of two spectrophotometric cell-free assays.
Oxidative potential (OP) of particulate matter (PM) - defined as the capacity of PM to oxidize target molecules generating reactive oxygen species (ROS) - has been proposed as a more health relevant metric than PM mass. In this study two cell-free methods were used to assess the OP of PM filters collected at an urban site and to evaluate correlation with PM mass and PM composition. Among the different assays existing, two inexpensive and user-friendly methods were used both based on spectrophotometric measurements of depletion rate of target reagents oxidized by redox-active species present in PM. One assay measures the consumption of dithiothreitol (OPDTT) and the other the ascorbate (OPAA). Although both assays respond to the same redox-active species, i.e., quinones and transition metals, no correlations were found between OPDTTand OPAAresponses to compounds standard solutions as well as to ambient samples. When expressed in relation to air volume, OPDTTm-3strongly correlates with PM2.5mass whereas no correlation was found for OPAAm-3with PM2.5.When expressed on mass basis, both OPDTTμg-1and OPAAμg-1show a strong dependence on the sample composition, with higher OP for summer samples. OPDTTm-3were highly correlated with the determined metals (Cu, Zn, Cr, Fe, Ni, Mn) whereas OPAAm-3showed only moderate correlation with Cu and Mn. Thus, the two assays could potentially provide complementary information on oxidative potential characteristic of PM. Consequently, the combination of the two approaches can strengthen each other in giving insight into the contribution of chemical composition to oxidative properties of PM, which can subsequently be used to study health effects.
Department of Chemical and Pharmaceutical Sciences, Via Fossato di Mortara 17/19, 44121 Ferrara, Italy.
Marco
M
Visentin
Department of Chemical and Pharmaceutical Sciences, Via Fossato di Mortara 17/19, 44121 Ferrara, Italy.
Antonella
A
Pagnoni
Department of Chemical and Pharmaceutical Sciences, Via Fossato di Mortara 17/19, 44121 Ferrara, Italy.
Elena
E
Sarti
Department of Chemical and Pharmaceutical Sciences, Via Fossato di Mortara 17/19, 44121 Ferrara, Italy. Electronic address: mpc@unife.it.
Maria Chiara
MC
Pietrogrande
D000393:Air Pollutants / Q000032:analysis*; D002474:Cell-Free System; D002947:Cities; D004784:Environmental Monitoring / Q000379:methods*; D008670:Metals / Q000032:analysis*; D010084:Oxidation-Reduction; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis* / Q000737:chemistry*; D017382:Reactive Oxygen Species; D012621:Seasons; D013053:Spectrophotometry
D000393:Air Pollutants; D008670:Metals; D052638:Particulate Matter; D017382:Reactive Oxygen Species
Ascorbic acid; Dithiothreitol; Oxidative stress; Particulate matter; Reactive oxygen species