The most polluted area in Delhi before Diwali was R K Puram, not Anand Vihar

The most polluted area in Delhi in the two weeks before Diwali 2026 was R K Puram. From 6 to 19 October its government monitor recorded a mean daily India NAQI of 204, in the Poor band, the highest of Delhi's 45 qualifying monitors. Just over Delhi's north-eastern border, Loni in Ghaziabad was worse still, at 232, the highest of all 68 monitors we ranked across Delhi NCR.

Anand Vihar, the area most often called Delhi's most polluted, came 47th of 68, with a mean of 146. Its air was no worse than it had been in mid-September.

This is Good Air's own analysis of the official monitors run by CPCB, the Delhi Pollution Control Committee (DPCC), the Indian Institute of Tropical Meteorology (IITM) and the Uttar Pradesh and Haryana pollution control boards.

Key findings

• Two monitors averaged above 200 (Poor): Loni, Ghaziabad (232) and R K Puram, Delhi (204). Each was above 200 on 10 of the 14 days.
• Next in Delhi came Dwarka Sector 8 (199) and Jahangirpuri (196), then Vivek Vihar, Punjabi Bagh and IITM's Pusa monitor, all at 192.
• Anand Vihar ranked 47th of 68, and 32nd of Delhi's 45. Its mean was 146 in both periods.
• 50 of 63 monitors got worse than in 13 to 22 September. The median monitor rose from 135 to 164.
• The biggest rises were in the west and on Delhi's edges. Within Delhi, Najafgarh rose most, from 95 to 162. Across the NCR, the Ballabgarh monitor jumped from 60 to 185.
• The cleanest air was at IHBAS, Dilshad Garden (100), only 1.6 km from Vivek Vihar (192). Faridabad's monitors were the NCR's cleanest as a group.

The 15 most polluted monitors in Delhi NCR

The table ranks monitors by the mean of their daily NAQI from 6 to 19 October 2026, with mid-September for comparison. PM2.5 is the mean of daily averages in October, in micrograms per cubic metre (µg/m³). "Days above 200" counts the October days on which the monitor's daily NAQI was in the Poor band or worse. NAQI runs from 0 to 500: 0 to 50 is Good, 51 to 100 Satisfactory, 101 to 200 Moderate, 201 to 300 Poor and 301 to 400 Very Poor.

Ranks use unrounded means, so monitors that show the same rounded figure keep their unrounded order. Where a monitor has fewer than 14 days, the rest had too few hourly readings to count.

Loni also had the highest PM2.5 in the table, 102 µg/m³, nearly seven times the World Health Organization's 24-hour guideline of 15 µg/m³. Jahangirpuri (88), R K Puram and Vivek Vihar (both 86) followed.

Why Anand Vihar was not the worst this time

Anand Vihar is the monitor most often quoted when Delhi's air turns bad. This October it was rarely extreme. Its daily NAQI was above 200 on only two days: 279 on 13 October and 209 on 17 October. On the other 12 days it stayed in the Moderate band, between 109 and 166.

Less than 3 km away, Vivek Vihar averaged 192. In Ghaziabad, Loni had a worse day than Anand Vihar's worst on 19 October, when its daily NAQI reached 341 (Very Poor).

The NCR-wide pattern had two peaks inside our October window. The median monitor's daily NAQI was 206 on 13 October and 207 on 17 October, when 36 and 35 monitors respectively were above 200. It dipped to 105 on 11 October. Our September comparison period was not clean either: the median rose to 193 on 23 September, the day IMD declared the monsoon withdrawn from the whole of Delhi (IMD, 23 September). IMD forecast scattered rain for Delhi from 25 to 29 September, and on 27 September the median fell to 51.

The cleanest air in Delhi NCR

None of these eight had a single day above 200. Even the cleanest is not clean: every one averaged in the Moderate band, and their PM2.5 was two to four times the WHO guideline.

By city, the median monitor in Ghaziabad (6 monitors) averaged 173, Noida (4) 166, Delhi (45) 162, Gurugram (4) 138 and Faridabad (3) 107. Greater Noida's two monitors averaged 180 and 175, and Noida's ranged from 134 at Sector 1 to 177 at Sector 62. For the same monitor-by-monitor view of India's other big metro, see our Mumbai AQI ranking.

Which areas got worse, and which got better

Most of the large rises were in west and north-west Delhi and in the Haryana towns on its edge. Najafgarh rose from 95 to 162, NSIT Dwarka from 97 to 163, Dwarka Sector 8 from 134 to 199 and Bahadurgarh from 123 to 187. Ballabgarh, south of Faridabad, had the largest rise of all, from 60 to 185.

The east went the other way. In mid-September the worst monitors in the NCR were Knowledge Park V in Greater Noida (208), Prashant Garden in Khora (204) and Sector 116 in Noida (192). By October all three had improved, to 175, 186 and 171. Faridabad's Sector 11 fell from 140 to 105 and IHBAS, Dilshad Garden from 123 to 100. Our data shows where the air changed, not why; wind direction, local burning and construction can all move a single monitor.

One monitor is one street, not a whole neighbourhood

Each figure here describes the air at one monitor, which sits next to a particular road, depot, park or industrial area. It is not an average for everyone who lives in R K Puram or Loni. The gaps between nearby monitors show how local the picture is:

• Vivek Vihar (192) and IHBAS, Dilshad Garden (100) are 1.6 km apart.
• Loni (232) and Ved Vihar-Loni (162), both run by the UP board, are 2.1 km apart.
• R K Puram (204) and IIT Delhi (168) are 2.4 km apart; Sri Aurobindo Marg (125) is 3.6 km from R K Puram.
• Delhi has two monitors at Pusa, about 80 m apart. IITM's averaged 192 and DPCC's 156. Part of that gap is the instruments and how they are sited, not the air. Treat differences of 20 or 30 points between single monitors with care.

The live Delhi page lists every station's reading now, worst first, and our hourly analysis shows the NCR's air is usually cleanest in the early afternoon (best time of day to go out).

Why our numbers run higher than CPCB's bulletin

CPCB's daily 4 pm bulletin gives each city's AQI as the "average of past 24 hours". It put Delhi at 158 on 13 October, 90 on 16 October and 139 on 19 October (CPCB, 13 October; 16 October; 19 October). Ghaziabad was at 175 and Ballabgarh at 248 on 19 October.

Our figures are higher because they are built differently. Good Air stores an NAQI value for every hour at every monitor, worked out from that hour's pollutant readings on CPCB's scale, and a daily figure is the mean of those hourly values. The index climbs steeply between 60 and 120 µg/m³ of PM2.5, so a day with a smoggy night usually scores higher this way than when the whole day is averaged first. Our hourly values are not smoothed 24-hour figures: at R K Puram on 19 October the hourly value went from 97 at about 4:30 pm to 328 at about 9:30 pm, India time. That is why we rank on daily means, never on hourly peaks.

The ranking holds on CPCB's own 24-hour rule too. Using daily mean PM2.5 above 90 µg/m³, the Poor line in CPCB's 24-hour PM2.5 scale, Loni and R K Puram each had 8 such days out of 14, the most of any monitor, and Anand Vihar had one. Compare our monitors with each other, not with the bulletin's headline number.

What comes next: GRAP and Diwali

CAQM, the Commission for Air Quality Management, brings in Stage I of the Graded Response Action Plan (GRAP), Delhi NCR's emergency pollution plan, when Delhi's AQI reaches or is forecast to reach 201 to 300 (CAQM, revision of 29 September). Delhi's 24-hour average stayed below that in the three bulletins above. We could not confirm from CAQM which stage, if any, was in force on 20 October; the Delhi air pollution tracker shows the latest, and our GRAP explainer sets out what each stage does.

IITM's Early Warning System expected Poor air in Delhi on 21 and 22 October, according to an IANS report (Social News XYZ with IANS, 19 October). Diwali falls on Sunday 8 November 2026 in the central government's holiday list (DoPT holiday list, reproduced by StaffNews). Our Diwali 2026 air quality guide covers the firecracker rules and how to protect your home on the night.

We will rerun this ranking with the same monitors after Diwali, in mid-November, and update this article.

How we measured

• Data. Hourly readings from the continuous monitors in CPCB's national network, run by CPCB, DPCC, IITM, UPPCB and HSPCB, collected by Good Air. No satellite estimates, model output or low-cost sensors.
• Area. Every monitor between 28.33° and 28.90° N and 76.85° and 77.50° E: Delhi, Noida, Greater Noida, Ghaziabad (including Loni and Khora), Gurugram, Manesar, Faridabad, Ballabgarh and Bahadurgarh. That box holds 82 monitors. Sonipat, Meerut, Bhiwadi and Dharuhera fall outside it.
• 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).
• Thresholds. A monitor is ranked only with at least 10 valid days of the 14 from 6 to 19 October: 68 qualified, 45 of them in Delhi. The September comparison needs at least 6 valid days of the 10 from 13 to 22 September (our archive starts on 13 September); 63 monitors had both.
• Dropped. 14 monitors had too few valid October days, including ITO, Cantonment Area and IGNOU Maidan Garhi in Delhi, Govindpuram in Ghaziabad, and ten DPCC monitors such as Nangloi and Tikri Kalan that appear in our archive only from 6 October or later. Three newer DPCC monitors (Badarpur, Burari and Vasundhara Enclave), Wave City in Ghaziabad and IGI Airport qualified for October but not for the comparison.
• Outliers. 11 of the 68 monitors logged an hourly NAQI of exactly 500, the top of the scale, on at least one day. We never use daily maxima; every figure is a mean of daily averages. No two monitors reported identical values, so none share a feed.

For how the rest of India changed after the monsoon, see India's air quality after the monsoon.