Report · 15 September 2026

187 AQI at Sonia Vihar, 24 hours to 4 PM, 15 September 2026, the worst monitor in Delhi today, Moderate on CPCB's documented formula, and PM2.5 set that figure. 14.8 lakh people live within 4 km of it.

101.1

TODAY

Delhi's AQI calculated with CPCB's documented formula, the mean of 42 stations.

1.39 crore

NEAR MODERATE OR WORSE

Within 4 km of 17 Moderate-or-worse monitors: 66.7 per cent of Delhi, every pollutant counted.

3.0x

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, 4.0 MB

The day in brief

Today, 15 September 2026, 24 hours to 4 PM: Delhi's AQI was 101.1, Moderate, calculated with CPCB's documented formula as the mean of 42 stations' AQIs (CPCB's note "How is AQI calculated?" and its AQI Calculator; page 32 sets out the formula). As measured, 41 of the 42 monitors reading PM2.5 were above the WHO 24-hour guideline of 15 µg/m³. 17 of 42 monitors read Moderate or worse on CPCB's documented formula, and 1.39 crore people, 66.7 per cent of Delhi, live within 4 km of one.

The year so far, 1 January to 15 September: the cleaner days of 2026 have been the dirtiest for these dates since 2019, because three days in four read above 107.2 on the particle AQI, against 88.4 on the same dates of 2025. The middle day reads 153.3 against 141.8 on the same dates last year. On an average day, 28.8 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 80 to 102. On the 41 stations that reported on both days, the 95 per cent interval runs 17.6 to 25.7 points.

Against last year: the observed reading

Today 101 across 42 stations. The year is judged on the 34 matched stations: 104 today against 112, the mean of the same date ±7 days of 2025 at those stations. The interval runs -19.6 to 4.9 points, so it leans better, but the interval spans zero and no claim is made.

The worst station in the city today

Moderate, set by PM2.5. Its PM2.5 averaged 86.0 µg/m³ over the 24 hours to 4 PM, 5.7 times the WHO 24-hour guideline of 15 µg/m³. Last year this station read 98 on the mean of the same date ±7 days, so the change is +88.7 points. 14.8 lakh people live within 4 km of this monitor. Within 500 m of the monitor, 56% of the land is built up and 39% is under vegetation, so this reading describes a mixed neighbourhood.

The year, from its best days to its worst

On the same 258 complete dates, 1 January to 15 September, the best tenth of days reads 76.6 against 71.7 and the worst tenth 295.8 against 298.3. The days at or below 200 went from 182 to 180.

How much of the city was above AQI 200

That is 12.0 of 43.2 reporting stations, against 27.4 per cent over the same dates last year, a change of +1.5 points on an interval of -3.9 to +7.1, 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 42 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 66.7 per cent of Delhi, living around the 17 monitors that read Moderate or worse. No monitor read Poor or worse today. Sonia Vihar was worst at 187, and 14.8 lakh people live within 4 km of it.

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