Mumbai's AQI more than doubled after the monsoon. Deonar had the worst air in October 2026

Mumbai's AQI more than doubled as the monsoon left. From 10 to 23 October 2026, Mumbai's mean daily India NAQI in our archive of official monitors was 101, in the Moderate band, against 45 (Good) from 15 to 28 September. Mumbai's PM2.5 nearly tripled over the same weeks, from 17 to 50 micrograms per cubic metre (µg/m³).

The worst monitor in the Mumbai region was Deonar, at 139, followed by Bhandup West (133) and Navy Nagar-Colaba (130). The cleanest was Borivali East's MPCB monitor, at 69. Mumbai is still much cleaner than Delhi on PM2.5, but the gap has narrowed: Mumbai's PM2.5 was 39% of Delhi's in late September and 68% of it in October.

This is Good Air's analysis of 45 official monitors run by CPCB, the Indian Institute of Tropical Meteorology (IITM), the Maharashtra Pollution Control Board (MPCB) and the Brihanmumbai Municipal Corporation (BMC). For the reading now, see Mumbai's live AQI: at 8:30 am IST on 24 October 2026 it showed an India NAQI of 123 (Moderate), from 23 stations.

Key findings

• Mumbai's city-wide India NAQI rose from 45 to 101. It was above 100 on 9 of the 14 October days and on none in late September. The worst day was 17 October, at 118.
• 38 of 39 monitors got worse. The median monitor in the region rose from 51 to 103. The only one that improved was Sidhi Vinayak Nagar in Ulhasnagar, from 78 to 75.
• The air turned on 30 September and 1 October. Mumbai's daily India NAQI went from 61 on 29 September to 76 on 30 September and 103 on 1 October. It has not been back below 76 since.
• Coarse dust sets Mumbai's index. Across 10 to 23 October, PM10 averaged 104 µg/m³, just above India's 24-hour standard of 100, and PM10 gave a higher sub-index than PM2.5 on all 14 days. In Delhi it did so on 7 of the 14 days.
• No monitor had a daily India NAQI above 200 between 10 and 23 October.

The most polluted areas in Mumbai, ranked

The table ranks monitors by the mean of their daily India NAQI from 10 to 23 October 2026, with 15 to 28 September for comparison. India NAQI runs from 0 to 500: 0 to 50 is Good, 51 to 100 Satisfactory, 101 to 200 Moderate and 201 to 300 Poor. PM2.5 and PM10 are October means in µg/m³.

Ranks use unrounded means. A second monitor at Bandra Kurla Complex, run by IITM, averaged 150 but reported enough hours on only 7 of the 14 days, so it is not ranked.

Mahape, in Navi Mumbai, shows what dust looks like in the data. Its PM10 averaged 144 µg/m³, the highest of any ranked monitor, while its PM2.5 was only 33. Deonar had high levels of both. Ambernath's Chinchpada monitor had a similar dust profile to Mahape, with PM10 of 109 and PM2.5 of 30.

The cleanest air in the Mumbai region

All six averaged Satisfactory. We left Sion (77) out of this list: its monitor reported exactly 80 for every hour of 11 and 12 October, which looks like a stuck reading.

By city, Good Air's city-wide India NAQI for 10 to 23 October was 101 in Mumbai, 100 in Navi Mumbai, 88 in Thane, 87 in Kalyan, 114 in Bhiwandi and 111 in Dombivli. Pune, for comparison, was at 123.

One monitor is one street, and agencies differ

In each of six close pairs of monitors we checked, the IITM monitor read higher than its MPCB or BMC neighbour, by 23 to 46 points:

Within Mumbai, the median IITM monitor averaged 124, the median MPCB monitor 93 and the median BMC monitor 88. Some of that gap may be real, since a monitor beside a busy road or building site sees more dust, and some may be the instruments. We cannot tell which, so treat gaps of 20 or 30 points between single monitors with care. Six of the top seven monitors in our ranking are IITM's, so read the ranking as a list of monitors, not a verdict on neighbourhoods.

Is Mumbai's air worse than Delhi's?

Not on average. On 21 October 2026 the Bombay High Court called it "shocking" that Mumbai's pollution was surpassing Delhi's, in a suo motu case on festival noise and firecrackers (The Federal, 22 October). Reports of the order did not say which figures the court compared.

Comparing the two cities on PM2.5 in µg/m³, the fairest common measure, Delhi was worse on most days. From 10 to 23 October Mumbai's city-wide PM2.5 averaged 50 and Delhi's 74. Mumbai was level with or above Delhi on only 3 of those 14 days: 11, 15 and 16 October, by 1 to 3 µg/m³. Mumbai's own peak was 62 µg/m³ on 17 October. Delhi then pulled away, reaching 111 on 20 October. CPCB's own 4 pm bulletin for 23 October gave Mumbai an AQI of 101 (Moderate) and Delhi 230 (Poor) (CPCB, 23 October).

Many apps quote the US AQI, which is stricter for the same air: Mumbai's mean US AQI from 10 to 23 October was 134, against an India NAQI of 101 (US AQI vs India NAQI).

Why Mumbai's air turns bad after the monsoon

The India Meteorological Department (IMD) said on 3 October that the southwest monsoon had withdrawn from parts of Maharashtra, with the withdrawal line running through Baramati and Harnai, south of Mumbai (IMD, 3 October). Mumbai's air had already turned two days before that. Without rain to wash it out, dust from roads, building sites and traffic stays in the air.

Construction is the usual suspect. Mumbai has about 3,200 active construction sites, and 3,166 had installed AQI display screens by 20 October, as the Bombay High Court had directed (Free Press Journal, 20 October). Our numbers fit a dust problem, with PM10 setting the index every day, but they cannot apportion sources.

What the BMC and the High Court have ordered

• BMC action plan, 2 October. At least 10 pollution hotspots per ward, each with a named officer; the 28-point dust rules enforced at construction and demolition sites, with stop-work notices and sealing for violators; developers to clean the roads around their sites; and a graded plan. Above AQI 200, roads are washed and sprinkled. If a monitoring station stays above 300 for three days in a row, polluting work within 2 km of it is suspended (Free Press Journal, 2 October). On our numbers no monitor has come near the 300 trigger this month.
• Bombay High Court, 21 October. Firecrackers banned on public roads, streets and footpaths, and completely in silence zones near hospitals, schools, courts and government offices. The BMC and Mumbai Police commissioners must file compliance affidavits by 26 October (Outlook India, 22 October).

As of 24 October we had not seen what the affidavits will say or when the court will hear the case next.

What usually comes next: November to January

October is only the start. A Centre for Science and Environment (CSE) study of the 2024–25 winter found Mumbai's worst month was December, with a winter average PM2.5 of 50 µg/m³ from 1 October to 31 January and a worst day of 81 (CSE, March 2025). Mumbai's 10 to 23 October mean in our archive was already about 50, though CSE's method differs from ours. An analysis of five winters of CPCB data found Mumbai's AQI rises sharply in November, December and January and eases a little in February; the 2025–26 winter had no Poor days (Newslaundry, 10 March 2026).

Our Diwali 2026 air quality guide covers firecracker rules. See also India's air quality after the monsoon and the most polluted areas in Delhi. We plan to rerun this Mumbai ranking in mid-November.

Why our numbers can differ from CPCB's bulletin

CPCB's bulletin gives a city's AQI as the average of the past 24 hours. Good Air computes an India NAQI for every hour at every monitor and averages those, so our daily means usually run higher: on 23 October CPCB said 101 for Mumbai and our daily mean was 112. Compare our monitors with each other, not with the bulletin.

How we measured

• Data. Hourly readings from CPCB-network monitors (CPCB, IITM, MPCB, BMC), collected by Good Air. No satellite, model or low-cost sensor data.
• Area. Every monitor between 18.8° and 19.6° N and 72.7° and 73.4° E: Mumbai, Navi Mumbai, Belapur, Thane, Kalyan, Dombivli, Ulhasnagar, Ambernath, Badlapur, Bhiwandi, Mira-Bhayandar and Virar. That box holds 45 monitors.
• Valid days. A day counts only if the monitor reported at least 12 hourly readings. Days run midnight to midnight UTC (5:30 am to 5:30 am in India). Our archive is complete to 23 October.
• Thresholds. A monitor is ranked only with at least 10 valid days of the 14 from 10 to 23 October: 41 qualified, 23 of them in Mumbai. The September comparison needs at least 7 valid days of the 14 from 15 to 28 September; 39 monitors had both.
• Checks. Ghatkopar's PM2.5 barely changed from hour to hour between 16 and 23 October, and Sion was stuck at 80 on two days. Chakala-Andheri East's September PM2.5 looks implausibly low next to its PM10.