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

This study investigates daily variations in redox potential of water- and organic-soluble PM2.5 during Delhi’s monsoon season, offering insights into its chemical composition, cytotoxicity, and oxidative threat to various lung conditions. PM2.5 samples, categorized by pollution levels, showed an average intrinsic oxidative potential (OPmDTT) 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 PM2.5 redox potential. The polar-phase distribution of RACs in PM2.5 can be modified by atmospheric photochemistry and precipitation. Biomass burning emerged as a pivotal pollution source, with polluted PM2.5 samples exhibiting higher cytotoxicity and oxidative stress in A549 cells. All PM2.5 compounds impaired cellular respiration, reducing the oxygen consumption rates in A549 cells. Intrinsic OPmDTT and OH• generation of PM2.5 were influenced by lung fluid variants, such as exogenous nicotine and endogenous inflammatory protein. This study provides a comprehensive perspective on PM2.5 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 PM2.5 health impacts