Generation and photogeneration of hydroxyl radicals and singlet oxygen by particulate matter and its inorganic components

Abstract Polluted air containing particulate matter (PM) is a huge environmental problem in the city of Krakow, Poland. PM causes numerous negative health effects including infection of the respiration system and cardiovascular disorders. The development of autoimmune disorders can be facilitated by redox active transition metals due to the generation of reactive oxygen species (ROS) and induction of oxidative stress, which results in lipid peroxidation, protein oxidation and severe oxidative modification of DNA. Our goal was to study ROS generation (in particular, HO• and 1O2) in the presence of PM collected via different procedures at different locations in Krakow. Scanning electron microscopy analysis confirmed that in all collected samples, aggregates of small grains could be observed. Cold plasma treatment was used to remove parts of the organic compounds and to uncover inorganic compounds which become more relevant following plasma treatment. All samples were photoactive and showed hydroxyl radical generation. Singlet oxygen production studies indicated that during plasma treatment, unsaturated organic species are produced that intensify the generation of 1O2. Generation of hydroxyl radicals and singlet oxygen in vitro was confirmed using human epithelial cell line A549.