At the other extreme, the 15 December bulletin showed a cluster of locations with AQI values in the “very poor” to “severe” bands. These were concentrated largely in:
Delhi NCR: Several monitoring stations in and around the capital recorded AQI close to or above 400, brushing into the “severe” category. Fine particulate matter (PM2.5) was the dominant pollutant, reflecting the combined impact of traffic, industry, winter inversion layers and regional pollution drifting into the city.
Neighbouring towns in Uttar Pradesh and Haryana: Cities around Delhi, such as those in the wider NCR belt, also fell into “very poor” territory, with AQI values above 300, again mainly due to high PM2.5 levels.
In CPCB’s health framework, “very poor” air can cause respiratory discomfort and aggravate heart and lung disease, especially in older adults, children and those with existing conditions, while “severe” air can trigger more serious health effects, including a higher likelihood of hospital admissions and acute events with prolonged exposure. On a day like 15 December, residents in these worst hit areas were advised to limit outdoor exertion, especially during peak traffic hours, and for sensitive groups to stay indoors as much as possible.
