Delhi's Post-Diwali Air Quality 'Very Poor', But Best In 7 Years

Delhi recorded "very poor" air quality on Tuesday after residents defied the ban on firecrackers in many parts of the capital on Diwali night, but the pollution levels for the next day were the lowest since 2015 thanks to favourable meteorological conditions that diluted the effect of the fireworks and stubble burning.

However, the neighbouring cities of Ghaziabad (266), Noida (299), Greater Noida (272), Gurugram (292) and Faridabad (289) reported "poor" air quality. An air quality index (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".

The firecracker emissions pushed the PM2.5 concentration at most places in the capital over 550 micrograms per cubic metre by 1 am. However, the PM2.5 levels dropped below 150 micrograms per cubic metre by 4 pm due to warm and windier conditions, which are favourable for the dispersion of pollutants.

PM2.5 are fine particles that are 2.5 microns or less in diameter and can travel deep into the respiratory tract, reaching the lungs and entering the bloodstream.

Delhi recorded an AQI of 310 at 11 pm on Monday. It increased to 326 by 6 am on Tuesday, remained stable till 9 am and started decreasing thereafter.

The 24-hour average AQI at 4 pm stood at 303, the lowest for the day after Diwali since 2015, when the Central Pollution Control Board (CPCB) started maintaining air quality data.

Delhi's AQI on the day after Diwali stood at 360 in 2015, 445 in 2016, 403 in 2017, 390 in 2018, 368 in 2019, 435 in 2020 and 462 in 2021.

Since Diwali was observed early in the season this year, moderately warm and windier conditions prevented rapid accumulation of pollutants from firecrackers bursting and reduced the effect of stubble burning.

Diwali was celebrated on November 4 in 2021 and on November 14 in 2020, when the temperatures were considerably low and the winds calm.

"Early Diwali, with slightly better meteorological conditions and comparatively lower fire counts, had a lower pollution base compared to the last few years," Sunil Dahiya, an analyst at the Centre for Research on Energy and Clean Air (CREA), said.

"Bursting of firecrackers led to a sharp increase in the air pollution with the PM2.5 concentration, on an average, jumping to 540 micrograms per cubic metre across Delhi by 12:30 am. Several monitoring stations in the capital recorded PM2.5 levels above 950 micrograms per cubic metre between 10 pm and 1 am," Mr Dahiya told PTI.

Meanwhile, Chief Minister Arvind Kejriwal said the results of the residents' efforts to curb pollution in the city are encouraging, but there is still a long way to go.

"Delhiites are working hard to curb pollution. The results have been very encouraging but there is still a long way to go. We will make Delhi the best city in the world," Arvind Kejriwal said in a tweet in Hindi.

Environment Minister Gopal Rai said the city saw fewer incidents of firecracker bursting this year and consequently, the air pollution levels dropped by around 30 per cent.

"The people of Delhi were very thoughtful on Diwali this year and I want to thank them. Today, the pollution level is the lowest in five years," Mr Rai told reporters.

The Aam Aadmi Party (AAP) government last month announced a complete ban on the production, sale and use of all types of firecrackers till January 1, including on Diwali, a practice it has been following for the last two years.

Mr Rai had earlier said bursting of firecrackers in Delhi will attract a jail term of up to six months and a fine of Rs 200.

He had said production, storage and sale of firecrackers will be punishable with a fine of up to Rs 5,000 and three years in jail under section 9B of the Explosives Act.

A total of 408 teams have been formed to implement the ban. The Delhi Police has set up 210 teams under assistant commissioners of police, the Department of Revenue has set up 165 teams and the Delhi Pollution Control Committee (DPCC) has constituted 33 teams.

The Delhi Police has reported 23 infractions of the ban on bursting of firecrackers and 150 violations of the ban on the sale of fireworks since October 1.

V K Soni, the head of the India Meteorological Department's Environment Monitoring and Research Centre, said: "The people of Delhi need to be applauded as firecrackers bursting and vehicular traffic were less as compared to the previous years."

The better AQI this year can be attributed to a proactive implementation of measures under the second stage of the Graded Response Action Plan (GRAP) three days ahead of Diwali, he added.

Earlier, the authorities would implement the measures only after the PM2.5 and PM10 concentration touched a particular threshold.

The hospitals in the national capital also saw fewer people coming in with respiratory illnesses as compared to last year.

Also, fewer instances of burn injuries were reported in the hospitals than in 2021.

Doctors, however, warned that it is too early to reach a definitive conclusion about the prevalence of respiratory illnesses post-Diwali since people tend to come to hospitals only when their condition worsens. Experts and forecasting agencies said the number of farm fires in Punjab and Haryana has increased but their contribution to pollution on Diwali remained low.

"Farm fires raged across Punjab and Haryana on Monday but the wind direction changed to south westerly, which is unfavourable for the transport of smoke. Hence, the contribution of stubble burning to Delhi's pollution (five to eight per cent) was also not very significant," said Gufran Beig, chair professor, National Institute of Advanced Studies, Indian Institute of Science.

Mr Dahiya said stubble burning in Punjab and Haryana peaks only in October-end and November and hence, its contribution to air pollution on Diwali was not very significant. However, it is likely to rise sharply in the upcoming days.

Emissions from firecrackers and farm fires have contributed significantly to Delhi's PM2.5 pollution on Diwali over the years.

The share of farm fires in Delhi's PM2.5 pollution was 25 per cent on Diwali in 2021, 32 per cent in 2020 and 19 per cent in 2019.

According to the Early Warning System of the Indian Institute of Tropical Meteorology (IITM), the air quality is forecast to remain in the "very poor" category on Tuesday and is likely to improve slightly over the next two days.

Delhi recorded a 24-hour average AQI of 312 at 4 pm on Monday -- the second best for Diwali in seven years.

The city had recorded an AQI of 281 on Diwali in 2018.

Delhi had recorded an AQI of 382 on Diwali last year, 414 in 2020, 337 in 2019, 319 in 2017, and 431 in 2016, according to the CPCB.

On Sunday evening, the city reported a 24-hour average AQI of 259, which was the lowest for Diwali eve in seven years.

The Indian Agricultural Research Institute reported 1,019 farm fires in Punjab, 250 in Haryana and 215 in Uttar Pradesh on Monday evening.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)