The PM2.5 concentration in Delhi on Diwali is likely to be the "lowest" in the last four years if no firecrackers are burnt, the government on Thursday said. The Ministry of Earth Sciences' air quality monitor, SAFAR, said that under 'zero-firecracker' scenario, the level of PM2.5 is likely to be the lowest in the past four years as not so calm surface winds in Delhi will help in dispersion (of pollutants).
PM2.5 is particulate matter which is about three per cent the diameter of a human hair and can lead to premature deaths from heart and lung diseases.
An AQI between zero and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".
A spike in PM2.5 in the early hours of November 15 is likely in case of fire-related emissions, it said.
On November 5, the Delhi government banned the sale and use of all types of firecrackers in the city from November 7 to November 30.
On Monday, the National Green Tribunal also imposed a total ban on sale or use of all kinds of firecrackers in the NCR from November 9 midnight to November 30 midnight, saying "celebration by crackers is for happiness and not to celebrate deaths and diseases".
It further said the pollution levels in Delhi during the Diwali period are likely to remain in the higher end of the "very poor" category in the absence of emissions due to fireworks.
SAFAR said stubble burning-induced impact on AQI is expected to increase from negligible to moderate in the next two days.
"The transport-level winds are now north-westerly and will have high potential to transport biomass plume in the next three days, but the expected moderate surface winds in Delhi will not allow rapid accumulation of pollutants for a longer period, it was quoted as saying by news agency PTI.
However, the air quality is expected to remain in the higher end of the very poor category and the lower end of severe category on Diwali night.
SAFAR said moderate easterly boundary layer winds are likely on November 15 and November 16. Isolated rainfall under the influence of a fresh Western Disturbance is also expected by November 16.
"These two factors will help in reducing the impact of any additional emissions and biomass plume," it said.
(With PTI inputs)