CPCB cited estimates from the Indian Institute of Tropical Meteorology’s Decision Support System (DSS)

As a thick grey haze shrouded the city on Monday, leaving Delhiites gasping for clean air, pollution data suddenly disappeared from official platforms for most of the day.

Ground-level ozone has been the lead pollutant on 10 of the 17 days this October, according to the Central Pollution Control Board (CPCB). While October normally sees the highest ozone levels, this year’s concentration exceeded 90 micrograms per cubic metre on several days, making it the highest for October since 2020.

Data from the CPCB highlights this risk, showing that pollution levels — specifically PM2.5 concentrations — are at their worst during the early morning hours.