Chennai had the highest reading in a six-city air-quality comparison reported by NDTV Profit on Monday, Oct. 26, while India Today had cited a higher AQI.in figure earlier that afternoon.
NDTV Profit reported Chennai at 222 in an article published at 7:27 p.m. IST (1:57 p.m. UTC). It did not specify when that reading was taken. The comparison also listed Kolkata at 155, Bengaluru at 146, New Delhi at 142, Mumbai at 140 and Hyderabad at 122.
India Today reported that AQI.in showed Chennai at 303 at 1 p.m. IST (7:30 a.m. UTC). Neither historical reading could be verified in AQI.in's accessible data.
India Today described the 303 reading as “severe,” but AQI.in's scale classifies scores from 301 onward as “Hazardous.” AQI.in labels readings from 201 to 300 “Severe.”
India's Central Pollution Control Board (CPCB) uses a separate National Air Quality Index. Its categories call readings from 201 to 300 “Poor” and those from 401 to 500 “Severe”; the highest pollutant sub-index determines the overall reading. The two indexes are not interchangeable.
The reports provide point-in-time figures. They do not establish Chennai's average AQI for the day, a sustained pollution trend or the cause of the different readings.
