Comparison of oxidative potential of PM1 and PM2.5 urban aerosol and bioaccessibility of associated elements in three simulated lung fluids

PM1 and PM2.5 aerosol samples collected during four seasons were analysed for bioaccessibility of 21 elements and oxidative potential (OP) determined by the dithiothreitol (DTT) assay in three simulated lung fluids (SLFs): deionised water, simulated alveoli fluid and Gamble's solution. Most elements had higher bioaccessibility in the submicron fraction than in the fine size fraction. The bioaccessibility of the element not only depends on the aerosol size fraction, but also varies between the three SLFs. In addition, the bioaccessibility of elements depends on both their chemical compound and the composition of the SLF. A very high bioaccessibility (up to 98%) was observed for As, Sb and Cd in all studied SLFs. The lowest bioaccessibility was observed for Ti, Al and Fe. The OP of urban particulate matter (PM), was studied as a relevant metric for health effects. The difference of OP value in simulated alveoli fluid and Gamble's solution compared to deionised water indicate the crucial effect of individual SLFs' composition on the OP. The complexation of elements with different ligands present in the solution can influence OPDTT depletion and, therefore, the potential health effects of inhaled aerosol. The correlation coefficients between total or bioaccessible concentrations of studied elements and volume normalised OP were calculated to examine the relationship between the elements and the OP. The strong positive correlations between some elements (i.e. Cd, Pb, As, Zn, Sn, Cu, Co, Ni, Mn) and DTT activity suggest their participation in the oxidative activity of PM.