People in the national capital breathed the cleanest air in five years for a day that falls immediately after Dussehra, environment monitoring officials said on Wednesday, but warned that the situation is likely to deteriorate in less than a week.

The celebration of Dussehra includes the burning of towering effigies and fireworks, and has been followed by a spike in air pollution at a time when meteorological factors and farm fires in neighbouring states usually turn Delhi’s air unfit for breathing.

Central Pollution Control Board (CPCB) data showed that on Wednesday, the city’s overall air quality index (AQI) was recorded at 173 compared to 326 last year (see box).

To be sure, when Dussehra falls is also linked to how polluted the air gets since the months of October and November is the period when temperature dips and farm fires peak. It has been celebrated three times in the first half of October in the last five years – among these, 2019’s AQI was the lowest.

Scientists of the India Meteorological Department (IMD) said the easterly winds and a prolonged monsoon had a major part to play in keeping pollutants in check. But that may change after October 12.

“The monsoon withdrawal has begun. It has started withdrawing in Punjab, western Haryana and northern Rajasthan, and in the next three to four days monsoon will withdraw from Delhi. After this, the wind direction will also change and pollution levels are likely to increase,” said Kuldeep Srivastava, head of IMD’s regional weather forecasting in Delhi.

Experts and organisers of Dussehra celebrations said a conscious decision by many to cut back on fireworks and effigy burning may have also contributed to the improved air quality.

“Looking at the rising pollution levels, we decided not to burn any crackers and still maintain the festivity of the day,” said Yogesh Pahuja, president of C-Block Lajpat Nagar-II residents welfare association, which did not burn an effigy this year and instead organised a laser show for the “Ravana dahan” ritual. “A lot of stress has been put on the use of green crackers this time, while bringing residents on board to come up with eco-friendly alternatives. All this, along with favourable weather conditions, has helped Delhi this time,” said Anumita Roychowdhury, executive director (research and advocacy), Centre for Science and Environment.

Experts also noted another change in trend this year in the pollution pattern, which showed a bigger spike in PM10 particles (usually associated with road dust) than PM2.5, finer particles that are emitted during any sort of combustion. “Usually after Dussehra and Diwali, where firecrackers are burnt, the dominant pollutant in the air is PM 2.5 which is more harmful to health. But this time it is PM 10,” said Gufran Beig, programme director of System of Air Quality and Weather Forecasting and Research (Safar).

Delhi’s air pollution is a toxic mix of vehicular exhaust gases, smoke from burning crops in the nearby states of Punjab and Haryana, road dust, and billowing sand from thousands of construction sites. The pollution is intensified by winter weather patterns and hemmed in by the towering Himalayas to the north.

After several years of the situation turning severe, authorities drew up an emergency action mechanism Graded Response Action Plan. The Environment Pollution (prevention and control) Authority – the committee responsible for implementing it– announced this year that some pre-emptive measures will be taken before the air worsens.

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