A Delhi resident checking an air quality app on Friday morning would have found little difference between neighbourhoods. The national capital's AQI was 419 at 8:40 a.m., and a thick layer of smoky haze covered the city for another day.

The citywide figure hides how uneven the pollution is. According to Central Pollution Control Board (CPCB) data, 33 of Delhi's 58 monitoring stations recorded 'severe' air, and several crossed 450. Among the stations listed, the worst readings were at institutional and commercial centres. IIT Delhi recorded 488, Chandni Chowk 479 and North Campus, Delhi University, 478. Pusa recorded 469, while Punjabi Bagh and Burari Crossing were both at 456.

The station-wise list from north and west Delhi was just as bad. NIH Narela recorded 445, DTU 443, Mundka 435, Aya Nagar 433, Chhawla 425 and Bawana 413. Even the stations with lower readings were in unhealthy territory. Burari recorded 398, Shadipur 385, Maidan Garhi 367, Nangloi and Ghoga 365 each, and Karala 340. The one clear exception was the Cantonment Area, at 160. That reading was still 'moderate', not clean.

The NCR picture: Noida takes the lead

Delhi was not the worst-hit city in the region on Friday morning. Adjoining Noida recorded an average AQI of 474 at 8:05 a.m., higher than the capital's own figure. Gurugram (352), Ghaziabad (369) and Greater Noida (351) were in the 'very poor' category. That category is less severe only in comparison.

CPCB classifies AQI readings of 0–50 as 'good', 51–100 as 'satisfactory', 101–200 as 'moderate', 201–300 as 'poor', 301–400 as 'very poor' and 401–500 as 'severe'. Under that scale, most of the region spent Friday morning in the top two categories.

The problem is wider than Delhi. Data from AQI.in showed that 86 of the world's 100 most polluted cities on Friday were in India. That makes the smog a national public health concern, not only a seasonal problem for the capital.

Why winter keeps doing this to Delhi

The causes are well known and recur every year. Post-Diwali firecracker emissions, stubble burning in Punjab and Haryana, vehicle exhaust, and emissions from industries and coal-fired power plants all add to the pollution. In winter, falling temperatures and low wind speeds trap those pollutants close to the ground.

Weather is not expected to help much soon. Delhi's maximum temperature is forecast at 27–30 degrees Celsius and the minimum at 14–17 degrees Celsius until November 15. These are cool, still conditions in which smog tends to linger.

What comes next

The Commission for Air Quality Management (CAQM) invoked Stage III of the Graded Response Action Plan (GRAP) across Delhi-NCR on November 6 as a precautionary measure. A week later, readings are still in the 'severe' range. That will raise questions about whether the current curbs are enough, or whether stricter measures are needed.

For now, the India Meteorological Department (IMD) expects the air to stay between 'very poor' and 'severe' until at least November 16. Relief depends on stronger winds after that, so residents face several more days of breathing hazardous air.

With inputs from IANS