Mumbai vs Chennai: Why did Diwali air pollution affect two coastal cities differently?

New Delhi: Mumbai recorded better air quality than Chennai after Diwali, despite firecracker pollution affecting both cities. Changing wind patterns, coastal geography and industrial emissions played a major role in the difference.

The impact of Diwali celebrations on air quality varied significantly across India’s coastal cities. While Mumbai recorded an Air Quality Index (AQI) of 172, placing it in the ‘moderate’ category, Chennai experienced ‘poor’ air quality on Monday morning. Four of Chennai’s seven active air monitoring stations reported AQI levels above 200.

Mumbai’s coastal location played an important role in reducing pollution. Surrounded by the Arabian Sea on three sides, the city benefits from changing sea and land breezes that help move polluted air away, The Indian Express reported. Weather conditions also supported better air quality. Easterly winds, influenced by an anticyclonic circulation over the Himalayan region, carried pollutants towards the sea. These winds also contributed to lower temperatures and improved air circulation. As a result, Mumbai and eight other cities in the Mumbai Metropolitan Region remained in the moderate AQI category despite extensive firecracker use.

Why was Chennai’s air quality worse?

Unlike Mumbai, Chennai did not receive the benefit of favourable easterly winds from the Bay of Bengal. Instead, northerly winds carried polluted air from industrial and urban areas of Andhra Pradesh and northern Tamil Nadu.

The report further added that the combination of firecracker smoke and pollutants transported from neighbouring regions increased the concentration of fine particulate matter (PM2.5). However, experts expect easterly winds to bring cleaner air and improve conditions.

Why did Maharashtra’s inland cities record high pollution?

Several inland cities, including Pune, Nagpur, Nashik, Jalna and Chandrapur, reported poor or very poor air quality after Diwali.Unlike coastal cities, these locations lack regular sea breezes that help disperse pollutants. Deficient rainfall, high temperatures and weak wind circulation further contributed to pollution levels.

Industrial activities, including automobile manufacturing, mining, steel production and thermal power generation, added to the pollution burden. The contrast highlights how wind direction, geographical location, weather conditions and industrial emissions determine how severely cities experience post-Diwali air pollution.