Residents of Delhi's Rohini area endured over 19 hours of the most severe air pollution levels possible, with the Air Quality Index (AQI) hitting the maximum reading of 500. This hazardous spell lasted from 6 pm on Sunday until 1 pm on Monday. However, in a concerning development, the AQI data for Rohini became unavailable from 2 pm onwards on Monday, with authorities citing "insufficient data" as the reason.
Data Discrepancy Raises Questions
The disappearance of the AQI reading has raised serious questions. For the AQI to be calculated, readings for at least one kind of particulate matter are required. Data from the Delhi Pollution Control Committee (DPCC) revealed that while figures for all other major pollutants were available, PM2.5 levels were missing. Officials from both the Central Pollution Control Board (CPCB) and the DPCC did not respond to queries regarding the missing AQI data.
Sunil Dahiya, founder and lead analyst at the think tank EnviroCatalyst, analyzed CPCB data. He pointed out that PM10 levels for Rohini were unavailable for two hours during the night. The highest hourly PM10 concentration was recorded at a staggering 907 micrograms per cubic metre at 3 am, with the lowest at 318 micrograms per cubic metre at 7 am. "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 stated. He added a chilling note: since the AQI was capped at 500, the actual pollution level could have been even higher.
Widespread Hazardous Air Grips the Capital
Rohini was not alone in its toxic crisis. Wazirpur saw its AQI reach the scale's maximum of 500 for the second consecutive day. CPCB data showed Wazirpur's AQI was at 500 for 17 hours from Sunday afternoon, only dropping slightly to 499 at 9 am on Monday.
The air remained grey and grim across the national capital. Even sunlight offered no respite in many pockets due to high emissions from local sources. Out of 39 active air quality monitoring stations in Delhi, AQI was in the severe range at 28 stations. Many areas recorded AQI levels close to the extreme for a second day in a row.
Among the worst-affected locations 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)
Experts Highlight Local Emission Crisis
Dipankar Saha, former head of CPCB's air laboratory, clarified India's AQI calculation method. "A minimum of two major or dominant parameters (one must be particulate matter) are required for the final calculation of AQI," he explained.
Sunil Dahiya emphasized that while the entire city suffered hazardous air, some stations showed significantly higher pollution levels. "It shows the presence of high local emissions around the stations," he said, pointing to sources like vehicular traffic, industrial activity, and construction dust in the immediate vicinity of monitoring sites. This localised intensification of pollution adds another layer of danger for residents in specific neighbourhoods, even as Delhi's overall air quality remains in the severe category.
