Across cities, official Air Quality Index (AQI) readings often overlook local hotspots. Chennai has eight Continuous Ambient Air Quality Monitoring Stations (CAAQMS) that function 24/7 throughout the year. But this isn’t enough to map particulate matter. Air changes every few metres, as researchers from the Indian Institute of Technology-Madras tell us. Seasonal variation, construction, vehicular movement, and proximity to industries also change the air we breathe, In 2022, over 17 lakh people died in India due to air pollution (PM 2.5), according to a Lancet study. With better hyper-local air data and public awareness, citizens and policymakers can target pollution…