Mystery of Delhi's missing PM2.5 data

For nearly a whole day, Delhi was not only wrapped in post-Diwali choke-smoke but also in a mystery: missing Monday morning air quality readings from several monitoring stations. It was only that evening that Delhi Pollution Control Committee (DPCC) released the 'missing' data: PM2.5 concentrations at some stations had crossed 2,000 g/m³ in early Monday, exceeding the national 24-hr standard of 60 g/m³ by more than 60x. Better late than never, sure. But as Centre for Research on Energy and Clean Air has pointed out, more than 20 monitoring stations not reporting data between midnight and 2 am during peak smog hours is a mystery by itself that needs solving.

Becoming 'shy' when faced with unpleasant facts isn't new. Last Diwali, DPCC's website stopped displaying PM2.5 readings from its RK Puram station for 5 hrs after levels touched 1,476 g/m³. This year, the disappearing act was more widespread: 35 of Delhi's 60 monitoring stations initially stopped reporting hourly data during the Diwali pollution spike. Also, CPCB and DPCC reported wildly different peaks. While the latter blamed a technical glitch, CPCB offered no explanation.

If data went missing, so, too, it seems, did political will and judicial authority that were supposed to make this Diwali different. According to Indian Institute of Tropical Meteorology, more than 80% of Delhi pollution the day after Diwali was due to firecracker emissions. Despite this, politicians fell back on pointing to sources beyond Delhi's borders. Supreme Court's green-cracker and designated bursting hours prescription was dispensed with. Add missing and conflicting readings to the mix and we have a deeper problem: distrust in the form of brushing unflattering facts under the dari.