After choking Delhi-NCR and Lucknow for the past two days, the smog blew down to Varanasi, making the air of Subah-e-Banaras the most polluted of the 42 cities monitored on 10 November 2017. The holy city’s Air Quality Index (AQI) at 4pm on Friday was at an alarming 491 at Ardhali Bazar monitoring station, according to Central Pollution Control Board data, just nine short of where the AQI scale ends at 500 and indicates a “public health emergency”. This was much worse than Delhi’s Friday AQI of 468.
The concentration of PM2.5, the prominent pollutant, was more than eight times the safe limit of 60 micrograms per cubic metre of air. The fine particulate matter, known as an invisible killer, has a diameter of less than 2.5 micrometers, 3% the diameter of a human hair. On 09 November 2017, Varanasi’s AQI was 358, which placed it in the “very poor” category. By rising 133 points to “severe” levels, air quality can now affect even healthy people and seriously impact those with existing diseases.
Fog starts dissipating as the day advances, but smog persists till late afternoon or the whole day,” said Tripathi, adding that air toxicity increases as dust particles and unsaturated hydrocarbons from vehicular exhausts mix in.