Report · 09 September 2026

242 AQI at Bawana, 24 hours to 4 PM, 09 September 2026, the worst monitor in Delhi today, Poor on CPCB's documented formula, and PM2.5 set that figure. 2.6 lakh people live within 4 km of it.

129.4

TODAY

Delhi's AQI calculated with CPCB's documented formula, the mean of 44 stations.

1.78 crore

NEAR MODERATE OR WORSE

Within 4 km of 39 Moderate-or-worse monitors: 85.3 per cent of Delhi, every pollutant counted.

2.2x

THE WHO 24-HOUR LINE

Delhi's PM2.5 today, as measured, against the WHO 24-hour guideline.

The AQI figures here are calculated with the formula that the Central Pollution Control Board (CPCB) publishes for its air quality index. CPCB's own documents set out that formula: CPCB's note on how the AQI is calculated; CPCB's AQI calculator.

The full report

The complete written report for this day, with every figure and the source it comes from.

Download the daily reportPDF, 3.9 MB

The day in brief

Today, 09 September 2026, 24 hours to 4 PM: Delhi's air today is 42.3 points worse than on this date last year, which is 46.8 per cent higher, and 12.7 points worse than yesterday, on the Central Pollution Control Board's own readings. Delhi's AQI was 129.4, Moderate, calculated with CPCB's documented formula as the mean of 44 stations' AQIs (CPCB's note "How is AQI calculated?" and its AQI Calculator; page 32 sets out the formula). As measured, 42 of the 44 monitors reading PM2.5 were above the WHO 24-hour guideline of 15 µg/m³. Poor or worse air reached 2.6 lakh people within 4 km of their monitor today, 1.2 per cent of Delhi.

The year so far, 1 January to 9 September: the cleaner days of 2026 have been the dirtiest for these dates since 2019, because three days in four read above 108.6 on the particle AQI, against 88.2 on the same dates of 2025. The middle day reads 155.4 against 144.5 on the same dates last year. On an average day, 29.5 per cent of Delhi's reporting monitors, about 12 of 43, sat above 200 on the particle AQI.

The findings

What the report says

Against yesterday: the one-day move

From 117 to 129. On the 43 stations that reported on both days, the 95 per cent interval runs 8.7 to 16.5 points.

Against last year: the observed reading

Today 129 across 44 stations. The year is judged on the 36 matched stations: 133 today against 90, the mean of the same date ±7 days of 2025 at those stations. The interval runs 32.8 to 51.7 points.

The worst station in the city today

Poor, set by PM2.5. Its PM2.5 averaged 101.7 µg/m³ over the 24 hours to 4 PM, 6.7 times the WHO 24-hour guideline of 15 µg/m³. Last year this station read 85 on the mean of the same date ±7 days, so the change is +157.1 points. 2.6 lakh people live within 4 km of this monitor. Within 500 m of the monitor, 71% of the land is built up and 26% is under vegetation, so this reading describes a densely built neighbourhood.

The year, from its best days to its worst

On the same 252 complete dates, 1 January to 9 September, the best tenth of days reads 77.5 against 71.4 and the worst tenth 300.0 against 300.0. The days at or below 200 went from 176 to 174.

How much of the city was above AQI 200

That is 12.3 of 43.2 reporting stations, against 28.0 per cent over the same dates last year, a change of +1.6 points on an interval of -4.0 to +7.3, so it is unchanged inside its margin.

Who the monitoring network reaches

Within 4 km live 92 per cent of Delhi's people, within 2 km 45 per cent, and within 500 m only 3.6 per cent. Delhi has 55 monitors in 53 zones, of which 44 reported today, and 30 of the 53 zones stretch past 4 km, the distance that the US EPA's neighbourhood scale treats as the furthest a monitor speaks for.

What each monitor's reading speaks for

That is 1.2 per cent of Delhi, living around the 1 monitor that read Poor or worse. Bawana was worst at 242, and 2.6 lakh people live within 4 km of it. On the wider count, 1.78 crore people, 85.3 per cent of Delhi, live within 4 km of a monitor at Moderate or worse.

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