Oxidative Potential of Atmospheric Aerosols over Different Regions of India and Surrounding Oceans

The capacity of particulate matter (PM) to induce reactive oxygen species (ROS) generation, known as PM's oxidative potential (OP), attracts atmospheric scientists, epidemiologists, and toxicologists to work critically in exploring their links. In the human body, the reactivity of particles with biological molecules strongly depends upon PM's composition. We observed that the diversity in PM sources and composition over different regions including urban, semiurban, remote, marine, and high-altitude sites in India results in disparate OPM (PM mass-normalized OP, PM's intrinsic reactivity) and OPV (volume-normalized OP, exposure). This work suggests that OP exposure is not a function of PM mass concentration alone and also depends on the PM composition. OPM follows the relative contribution of organic matter in PM2.5 mass over north/northeastern India. Results disclose higher OPM for combustion-derived emissions compared to noncombustion sources over India and surrounding oceans. Despite the measured lower PM2.5 and PM10 mass concentrations over remote locations, people are often exposed to similar OPV (OP concentrations) compared to those living near sources in urban regions of India. Our observations over remote regions also hint that atmospheric aging makes PM more reactive. We suggest considering PM composition, mainly redox-active species, while developing mitigation strategies to improve air quality for better health.