Delhi's Air Quality Crisis: A Closer Look at Missing Data on Diwali Night

Strategic Insights -

Delhi's ambient air quality stations unexpectedly stopped transmitting data during peak pollution hours on Diwali night, leading to a reduced AQI reading on the day after Diwali. A TOI analysis of hourly air quality readings reveals that if all stations had reported data, the city's average AQI would likely have been closer to 'severe' levels. This raises concerns about the reliability of official air quality data and its implications for public health.

Key Takeaways:

  • Only 8 out of 39 air quality stations in Delhi logged uninterrupted hourly data during the 24 hours till 4pm on Diwali, a period that spans Diwali night and the morning after.
  • A total of 173 hours of AQI data went missing across 31 stations, with a scale of outage unprecedented in comparison to last year's Diwali night.
  • On the day after Diwali last year, 41 hours of data was missing, including 34 hours in the peak pollution period.
  • Delhi's average air quality slipped into the 'severe' category (AQI of 400+) in the hour ending 10pm on Diwali and stayed in the extreme zone for 13 hours.
  • At 1am, when the city's hourly average AQI peaked at 489, the number of working stations dropped to 19, and by 3am, data was available from just 12 stations, less than a third of the total.
  • Delhi environment minister Manjinder Singh Sirsa initially refuted the missing data, stating that all data is available on CPCB and DPCC.
  • However, the AQI data continues to be missing in CPCB's website five days after TOI's initial report.

Statistics:

  • 8 out of 39 air quality stations in Delhi remained operational during the 24 hours till 4pm on Diwali.
  • 173 hours of AQI data went missing across 31 stations.
  • 41 hours of data was missing on the day after Diwali last year, including 34 hours in the peak pollution period.
  • Delhi's average air quality slipped into the 'severe' category (AQI of 400+) in the hour ending 10pm on Diwali.
  • 29 stations in the city recorded an AQI of 500 - the maximum on the scale, before blanking out.

Sources:

  • Times of India (edition dated Oct 22)
  • CPCB (Central Pollution Control Board) website
  • DPCC (Delhi Pollution Control Committee) website
  • Statement of Delhi Environment Minister Manjinder Singh Sirsa