Delhi breaths fire: AQI maxed out for over 19 hours at Rohini before data goes missing

NEW DELHI: For over 19 hours, the AQI maxed out at 500 at Rohini - 6 pm on Sunday to 1 pm on Monday.

From 2 pm onwards, Rohini's AQI was unavailable on Monday. "Insufficient data" was stated as the reason.




Readings are required on at least one kind of particulate matter for the calculation of the AQI. Delhi Pollution Control Committee's (DPCC) data shows that except for the PM2.5 levels, figures for all other major pollutants were available. Officials from Central Pollution Control Board (CPCB) and DPCC did not respond to TOI's queries on the missing AQI for Rohini.

Apart from Rohini, Wazirpur saw the AQI reach the scale's maximum of 500 for the second consecutive day.

The air stayed grey and grim in other parts of the city as well. Even after the sun came out, there was no respite in certain pockets due to the high emission load from local sources.

Sunil Dahiya, founder and lead analyst at think tank EnviroCatalyst, said Central Pollution Control Board's data shows that PM10 levels for Rohini were unavailable for two hours in the night. "The highest hourly PM10 concentration was recorded at 907 micrograms per cubic metre at 3 am and lowest at 318 micrograms per cubic metre at 7 am at Rohini. However, PM2.5 levels were unavailable. Since only one particulate matter is needed for AQI, enough data was available for the calculation of Rohini's AQI," Dahiya said. He added that since the AQI was capped at 500, it could have gone higher.

Dahiya said though the city saw hazardous air, some stations showed higher pollution levels. "It shows the presence of high local emissions around the stations," he said.

Dipankar Saha, former head of CPCB's air laboratory, said in India, AQI is designed with eight parameters. "A minimum of two major or dominant parameters (one must be particulate matter) are required for the final calculation of AQI," he said.

CPCB's data showed that Wazirpur's AQI was at 500 for 17 hours from Sunday afternoon. It became 499 at 9 am on Monday. In other parts of the city, the air quality remained hazardous. Out of 39 active air quality monitoring stations in Delhi, AQI was in the severe range at 28 stations.

Many stations recorded AQI close to extreme levels for the second consecutive day. Among the worst-hit areas were Ashok Vihar (499), Jahangirpuri (498), Anand Vihar (493), Vivek Vihar (493), Siri Fort (484), Nehru Nagar (483), Punjabi Bagh (481, Delhi Technical University (479).