Size-resolved exposure risk and subsequent role of environmentally persistent free radicals (EPFRs) from atmospheric particles

Abstract

Environmentally persistent free radicals (EPFRs) are pollutants in the environment that have recently received widespread attention, but information about their formation and size-resolved distribution in atmospheric particles is scarce. We report the exposure risk and the related effect on human health of EPFRs in size-resolved (<10 μm) atmospheric particles in Xiamen, China, using electron paramagnetic resonance (EPR) spectroscopy. We found that the concentration of EPFRs in atmospheric particles ranged from 1.60 × 1013 spins/m3 to 24.48 × 1013 spins/m3, and the EPFRs concentration were lower in PM2.1–10 than in PM < 2.1. The results also present that g factor range observed in the spectra was 2.0031–2.0038. These EPFRs are considered to correspond to the g-factors of C-centred radicals with adjacent O atoms. In addition, the concentration of EPFRs was positively correlated with the concentrations of Cu, Fe, Mn, Pb and V. We also discuss reactive oxygen species (ROS), mainly OH radicals, which were formed by redox cycle of the EPFRs. The EPFRs deposition observed in the respiratory system was equal to smoking 29 cigarettes (extrathoracic: 13; tracheobronchial: 8; pulmonary: 8) per person per day. This study presents information about the potential pathogenic risks of size-resolved atmospheric particles, and this information has certain guiding significance for reducing respiratory diseases.