Mumbai: Even as a heavy blanket of monsoon clouds hovered over the Mumbai Metropolitan Region (MMR), the cities of Mumbai, Thane, and Navi Mumbai recorded starkly contrasting air quality trajectories through most of June.A comparative analysis of air quality index (AQI) data from June 1 to 27 showed that Mumbai emerged as the cleanest city in the MMR by clocking eight days in the ‘good’ category (AQI 0–50), while Thane lagged with the lowest count of pristine air days (3) despite maintaining a highly consistent ‘satisfactory’ AQI streak.According to data compiled from the daily AQI calendar, Mumbai registered clean air spells primarily during the latter half of the month — on June 1, 18, 19, 20, and from June 22 to 25. Satellite city Navi Mumbai logged seven ‘good’ air days, while Thane cut a dismal figure with just three days of ‘good’ AQI days from June 22 to 24.However, Thane dominated the ‘satisfactory’ category (AQI 51–100), logging 24 days where the air quality remained moderate with minor health impacts for sensitive individuals. Navi Mumbai recorded 20 ‘satisfactory’ days, while Mumbai saw 19.None of the three cities breached the ‘moderate’ or ‘poor’ thresholds during this 27-day summer-monsoon transition period, ensuring that the overall regional air remained highly breathable.Overall, Mumbai scored the best in the month due to its superior number of ‘good’ air days and lower localised AQI dips, making it the cleanest pocket in the metropolitan belt. PM10 emerged as the predominant pollutant in Thane and Navi Mumbai, where it dictated the AQI on 26 out of 27 days. Conversely, Mumbai exhibited a mixture of different pollutants: PM10 was the most frequent primary pollutant at 13 days, and ozone and NO2 dominated for seven days each.“Mumbai exhibits higher NO2 levels primarily driven by its concentrated industrial emissions, alongside volatile organic compounds that trigger ground-level ozone formation due to intense vehicular density in the island city,” said Sunil Dahiya, founder and lead researcher at Envirocatalyst. “Conversely, PM10 largely fueled by road dust dominates the satellite cities of Thane and Navi Mumbai, where heavy construction and infrastructure projects remain major contributors.”
