A day after Sri Lankan cricketers took to the field wearing anti-pollution masks, Delhi’s air turned fouler on Monday with a sharp rise in the level of particulates since morning.
The concentration of the most dominant pollutants, PM2.5 and PM10, reached levels as high as 276 and 455 micrograms per cubic metre by 3 p.m., according to the Central Control Room for Air Quality Management of the Central Pollution Control Board (CPCB).
Pollution is considered severe plus or emergency when the readings are above 300 and 500 respectively. The corresponding prescribed standards are 60 and 100.
The Air Quality Index (AQI), as recorded by the CPCB, also reflected the rise in the levels of these ultrafine air-borne particulates. The AQI was 390, on a scale of 500, around 3.30 p.m. It is classified as ‘very poor’. However, it is menacingly close to the ‘severe’ category.
Sunday’s 24-hour average was 351.
A ‘very poor’ AQI comes with the warning that people may develop respiratory illness on prolonged exposure while exposure to ‘severe’ air affects healthy people and seriously impacts those with existing respiratory or cardiovascular diseases.
An AQI between 0-50 is considered Good, 51-100 Satisfactory, 101-200 Moderate, 201-300 Poor, 301-400 Very Poor, and 401-500 Severe.
November witnesses extremely high levels of pollution as smoke from paddy residue burning reaches the city, aggravating the situation.
However, there are phases, when such spikes are seen even during December and January, mostly due to rapid drop in temperature and high moisture content, factors that trap particulates near the surface.
According to an IIT-Kanpur study, the sources of PM2.5 and PM10 during the winter months are: secondary particles like nitrates (25-30%), vehicles (20-25%), biomass burning (17-26%), municipal solid waste burning (9-8%) and to a lesser extent soil and road dust.