Variation of PM_2.5Redox Potential and Toxicity During Monsoon in Delhi, India

This study investigates daily variations in redox potential of water- and organic-soluble PM_2.5 during Delhi’s monsoon season, offering insights into its chemical composition, cytotoxicity, and oxidative threat to various lung conditions. PM_2.5 samples, categorized by pollution levels, showed an average intrinsic oxidative potential (OPmDTT[jls-end-space/]) of 27.5 pmol min^–1 μg^–1, OH^• generation of 51.1 pmol μg^–1, and antioxidant capacity (AOC) in both gallic acid and trolox equivalency of 62.5 and 35.3 pmol μg^–1, respectively. Water-soluble redox-active compounds (RACs) contributed to approximately 67% of the PM_2.5 redox potential. The polar-phase distribution of RACs in PM_2.5 can be modified by atmospheric photochemistry and precipitation. Biomass burning emerged as a pivotal pollution source, with polluted PM_2.5 samples exhibiting higher cytotoxicity and oxidative stress in A549 cells. All PM_2.5 compounds impaired cellular respiration, reducing the oxygen consumption rates in A549 cells. Intrinsic OPmDTT and OH^• generation of PM_2.5 were influenced by lung fluid variants, such as exogenous nicotine and endogenous inflammatory protein. This study provides a comprehensive perspective on PM_2.5 pollution and its toxicity in Delhi, India during distinct pollution periods and also points out the importance of considering population disparities and individual health status in assessing PM_2.5 health impacts.