Ask any Mumbaikar, and they will tell you about the haze: a grey blanket over the skyline that was rare 20 years ago but is now routine. They are not imagining it. Ground monitors and satellites agree. Until 2006, Mumbai’s annual average PM10 levels hovered around 60-80 µg/m³, low by Indian standards. After 2006, it climbed, reaching 166 µg/m³ in 2018. Official data show a decline since then, yet the city’s PM10 level in 2025 was 88 µg/m³, 1.5 times the national standard.

But annual averages hide the worst of it. Mumbai’s pollution is seasonal: relatively low from June to September, when the monsoon scrubs the air, and high to severe from October to March. In the peak months, PM10 levels run 3-4 times the national standard. And our standard is lenient. In winter, Mumbai’s air can be 10-15 times what the WHO considers safe.