Report · 21 August 2026

275 AQI at Anand Vihar, 24 hours to 4 PM, 21 August 2026, the worst monitor in Delhi today, Poor on CPCB's documented formula, and PM2.5 set that figure. 13.6 lakh people live within 4 km of it.

120

TODAY, AS MEASURED

Measured on CPCB's documented formula; with the weather removed, the model's 43 stations read 89, against 118 measured.

1.68 crore

NEAR MODERATE OR WORSE

Within 4 km of 34 Moderate-or-worse monitors: 80.6 per cent of Delhi, every pollutant counted.

2.5x

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, 4.1 MB

The day in brief

Today, 21 August 2026, 24 hours to 4 PM: worse than last year on the observed index, +35 points; with the weather removed, still 1.5 points worse on the model's count. 2 of 3 pollutants, PM2.5, PM10, show no real improvement. Delhi's AQI was 120.1, 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 34 sets out the formula). As measured, 42 of the 43 monitors reading PM2.5 were above the WHO 24-hour guideline of 15 µg/m³. Poor or worse air reached 13.6 lakh people within 4 km of their monitor today, 6.5 per cent of Delhi.

The year so far, 1 January to 21 August: the cleaner days of 2026 have been the dirtiest for these dates since 2024, because three days in four read above 113.3 on the particle AQI, against 95.6 on the same dates of 2025. The middle day reads 161.5 against 152.3 on the same dates last year. On an average day, 31.8 per cent of Delhi's reporting monitors, about 13 of 43, sat above 200 on the particle AQI.

The findings

What the report says

The verdict, both rulers

On the weather model's own count of 35 matched stations, the observed year reads +37.7 points; with the weather removed it reads +1.5 on the model's count; the stations are too mixed to call. 2 of 3 pollutants, PM2.5, PM10, show no real improvement. With the weather removed, 21 of the model's 35 matched stations read higher than last year.

Against yesterday: the one-day move

From 116 to 120. On the 44 stations that reported on both days, the 95 per cent interval runs -2.7 to 10.5 points, so the honest reading is level, not worse.

Against last year: the observed reading

Today 120 across 44 stations. The year is judged on the 36 matched stations: 124 today against 89, the mean of the same date ±7 days of 2025 at those stations. The interval runs 25.5 to 45.3 points.

The worst station in the city today

Poor, set by PM2.5. Its PM2.5 averaged 112.1 µg/m³ over the 24 hours to 4 PM, 7.4 times the WHO 24-hour guideline of 15 µg/m³. Last year this station read 115 on the mean of the same date ±7 days, so the change is +159.9 points. 13.6 lakh people live within 4 km of this monitor. Within 500 m of the monitor, 84% of the land is built up and 14% is under vegetation, so this reading describes a densely built neighbourhood.

The year, from its best days to its worst

On the same 233 complete dates, 1 January to 21 August, the best tenth of days reads 82.9 against 73.3 and the worst tenth 302.2 against 308.3. The days at or below 200 went from 157 to 155.

How much of the city was above AQI 200

That is 13.2 of 43.2 reporting stations, against 30.2 per cent over the same dates last year, a change of +1.6 points on an interval of -4.5 to +8.2, 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 6.5 per cent of Delhi, living around the 1 monitor that read Poor or worse. Anand Vihar was worst at 275, and 13.6 lakh people live within 4 km of it. On the wider count, 1.68 crore people, 80.6 per cent of Delhi, live within 4 km of a monitor at Moderate or worse.

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