Rain, gusty winds bring 'significant' improvement in Delhi-NCR's air quality

Delhi's air quality improved "significantly" on Monday due to light rain and favourable wind speed and was recorded in the 'poor' category after a 15-day spell of 'very poor' and 'severe' air days.

The city's 24-hour average air quality index (AQI) improved to 221, which falls in the 'poor' category. It was 435 on Sunday and 414 on Saturday (Diwali).

The last time Delhi's AQI was recorded in the 'poor' category was on November 2.

The AQI reached the 'moderate' category by 6 pm.

The central government's Air Quality Early Warning System for Delhi said AQI improved "significantly" after Diwali owing to rainfall and strong winds and is likely to remain in the 'moderate' category on Tuesday.

The air quality is likely to deteriorate marginally and hit the 'poor' category on Wednesday.

In Delhi-NCR, the levels of PM2.5 – which is about three per cent the diameter of a human hair and can lead to premature deaths from heart and lung diseases – were 88 microgram per cubic meter (µg/m3) at 6 pm.

The safe limit is 60 µg/m3.

PM10 level stood at 135 µg/m3 at 6 pm. PM10 levels below 100 µg/m3 is considered safe in India and 500 µg/m3 is the emergency threshold.

The last time Delhi recorded such low PM10 levels was on September 28.

The neighbouring cities of Faridabad (186), Ghaziabad (207), Greater Noida (226), Gurgaon (246) and Noida (243) recorded their AQI in 'poor' and 'moderate' categories after braving 'severe' air quality on Saturday and Sunday.

Delhi had recorded the worst pollution levels on Diwali in the last four years due to the combined effect of stubble burning, firecrackers and unfavourable meteorological conditions.

The air quality on the day after Diwali was also the poorest since 2016.

In a special report, the Central Pollution Control Board said almost all pollutants reported higher values on Diwali day this year as compared to 2019.

It could be attributed to bursting of firecrackers, higher share of stubble burning and unfavourable meteorology during the festival season, the CPCB said.

However, rain and high-velocity winds came to Delhi's rescue this year.

Winds gusting up to 40 kilometers per hour swept away the pollutants, while light rainfall in the afternoon and evening on Sunday washed everything down.

Kuldeep Srivastava, the head of the India Meteorological Department, said the wind speed was favourable for dispersion of pollutants on Monday as well.

The Ministry of Earth Sciences' air quality monitor, SAFAR, had also predicted that pollution levels may recede to the 'poor' category "in case of enough rains and washout".