Air Quality Monitors Go Blank as PM2.5 Levels Cross 1,000 µg/m³
Photo : PTI
New Delhi: At a time when Delhi’s air quality plunged to “hazardous” levels post-Diwali, several air monitoring stations in the national capital mysteriously stopped displaying data during the most critical hours. Around midnight, when PM2.5 levels at RK Puram peaked at a staggering 1,476 micrograms per cubic metre, real-time readings vanished from the Delhi Pollution Control Committee’s (DPCC) website for nearly five hours, as per a TOI report.
The data reappeared at 6 am, showing a downward trend, 1,187 µg/m³ at 6 am and 1,064 µg/m³ at 7 am, but by then, the city’s worst pollution phase had passed.
Data Vanishes During Peak Pollution Hours
Experts said several monitoring stations run by DPCC, the Central Pollution Control Board (CPCB), and the India Meteorological Department (IMD) stopped showing hourly data for PM10 and PM2.5 when levels neared or exceeded the 1,000 µg/m³ mark. They warned that such data gaps could distort daily averages and obscure the true severity of pollution, as per the report.
At Nehru Nagar, the most polluted station on Diwali night, hourly PM2.5 concentration touched 1,763 µg/m³ at 10 pm, but the 11 pm data was missing. Similarly, CPCB’s ITO station recorded 923 µg/m³ at 1 am, but no data for six hours in between. Gaps were also found at NSIT Dwarka, where PM10 data disappeared between midnight and 5 am. IMD’s Ayanagar station reported missing PM10 readings for five hours and missing PM2.5 data between 2 am and 4 am.
Experts Cry Foul Over Missing Data
Sunil Dahiya, founder and lead analyst at EnviroCatalysts, said the blackout wasn’t isolated, in the report. “Many stations blanked out on Monday night. This is not an issue with stations run by one monitoring agency; all four agencies, IITM, IMD, DPCC and CPCB, faced this issue,” he said.
He further noted, “The observed pattern shows that most stations stopped providing data when they approached 1,000 µg/m³ while there were stations such as Anand Vihar, Nehru Nagar, Mundka, etc. that recorded values above 1,000 µg/m³, indicating that the technology of monitoring isn’t an issue, at least in terms of being available. This is not the first time that the stations have stopped providing data; we have observed this over the past years too.”
Dahiya added that if monitoring systems have a technical limit, they must be upgraded. “Such missing data hampers data-driven insights, understanding the contribution of certain activities, their impact on health as well as skews the daily pollution level recordings, giving a false sense of lower air pollution levels,” he added.
Government Denies Data Blackout
Environment Minister Manjinder Singh Sirsa, however, dismissed the claims, saying, “All data is available on CPCB and DPCC, there is no missing data. You have to check.” Taking a veiled dig at the AAP, which had raised the issue, he added, “Those who are saying there is missing data, you know what their intentions are.”
Meanwhile, CPCB, DPCC, the Commission for Air Quality Management, and the IMD did not respond to queries regarding the missing data.
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