Multi-City Exposure Assessment of PM2.5 and Its Optical Properties for the APEAL: A Longitudinal Cohort Study

Rapid urbanization intensified spatial variability in air pollution across India, while monitoring networks are limited in capturing local exposure conditions. This study develops and evaluates an exposure assessment framework, with pilot findings from the Air Pollution Exposure on Adolescents’ Lungs (APEAL), a multi-centre prospective cohort study conducted in Delhi, Mumbai, Bengaluru, and Mysuru, which represent diverse air pollution levels. Residential measurements of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) were conducted using standardized protocols. Results from pilot-phase showed that mean outdoor PM2.5 concentrations were highest in Delhi (90.4 ± 12.0 µg/m³), followed by Mumbai (57.2 ± 12.8 µg/m³), and Bengaluru (53.0 ± 9.0 µg/m³), with Mysuru having the lowest at 32.3 ± 9.3 µg/m³, indicating a north-south gradient attributed to anthropogenic activities. Optical properties of PM2.5, including absorption coefficients (Babs370 and Babs880), and calculated Absorption Angstrom Exponent (AAE), show significant variations and are primarily influenced by combustion sources. Further, this approach will include seasonal monitoring, chemical characterization, toxicity analysis, land-use regression (LUR) modelling, and time activity pattern to generate high-resolution exposure estimates. This methodology provides a robust, scalable framework for epidemiological studies and urban air pollution assessment in resource-limited settings, with relevance for urban planning and policy making.