Delhi recorded its worst day-after-Diwali air quality since the Central Pollution Control Board started measuring this in 2016, with the air quality index, or AQI, soaring to 462 on the back of a sharp increase in stubble burning in Punjab and Haryana, and a blatant violation of the fireworks ban in the national capital.
Lower temperatures and non-existent winds did not help.
Delhi police control room data showed that on November 4, till midnight, at least 1,100 complaints of people using firecrackers was reported from across the city – averaging 47 an hour.
According to CPCB, in 2016, when it started tracking AQI, the day after Diwali saw a reading of 445. That was also the year when Delhi witnessed one of its worst pollution spells, recording its most polluted day ever on November 6 when the AQI rose to 497.
On Thursday (Diwali day), the overall AQI in Delhi was 382, in the “very poor” zone.
CPCB data showed the 24-hour average AQI entered the “severe” zone at 9pm, gradually rising each hour as a haze enveloped the Capital. It was 404 at 9pm, 422 by midnight, 428 by 2am, 444 by 6am, 446 by 7am, and 451 by 8am on Friday.
Other cities and towns in the national capital region (NCR) fared no better, with Faridabad (AQI 464), Ghaziabad (461), Gurugram (470), Greater Noida (441) and Noida (471) — all in the severe zone, according to CPCB’s 24-hour average AQI at 4pm.
An AQI of 51-100 is categorised as “satisfactory”, 101-200 as “moderate”, 201-300 as “poor”, 301-400 as “very poor”, and above 401 as “severe”.
Nasa’s satellite imagery recorded over 3,500 farm fire events across the northern plains on Thursday, with northwesterly winds carrying pollutants from these to the National Capital Region. According to the Union earth science ministry’s System of Air Quality and Weather Forecasting and Research (SAFAR), stubble burning accounted for 25% of PM2.5 (particulate matter with a diameter less than 2.5 micrometers) on Diwali day and 36%, the day after. Prior to this, the highest contribution from stubble burning in Delhi’s air was 20%, on October 29. Interestingly, SAFAR said emissions from fireworks were “almost of the same magnitude”.
Farm fires raging
While the contribution of fireworks to pollution will decline, that of farm fires is expected to increase. The paddy harvest is 70% complete, and instances of stubble burning are peaking; 55% of total cases of stubble burning this year have been reported in the last five days.
The number of farm fires thus far this year, at 23,465, is still almost half of 44,086 cases reported for the corresponding period (till November 4) last year, but most officials expect it to increase over the coming week.
On November 4, 3,032 farm fire events were captured by satellite in Punjab. In 2019, there were 5,953 active fires on the same date, and in 2020 there were 4,908 — indications of how high the number could go.
Delhi environment minister Gopal Rai on Friday blamed large-scale setting of fireworks and the peaking of farm fires in Punjab and Haryana for the steep fall in the Capital’s air quality. He also blamed the Bharatiya Janata Pary for “deliberately encouraging” people to flout the fireworks ban on Diwali.
This October, residents in NCR experienced the cleanest air ever on record, according to government figures. The reasons: unseasonal October rains and a delayed harvest (and therefore delayed stubble burning) season in Punjab and Haryana. HT reported on October 27 that Delhi was headed towards an air emergency with stubble fires expected to peak around Diwali.
“Delhi did not record a single bad air day in October. Impact of 3,500 farm fires around Delhi was visible in national capital today…There was also deliberate violation of the cracker ban in the city, encouraged by the BJP,” Rai said.
Meanwhile, Delhi BJP chief Adesh Gupta slammed the Delhi government for not taking any concrete measures to curb pollution. Referring to Rai’s statement, Gupta said, “The Kejriwal government is trying to hide its failure to curb pollution in the city. In the past six years, the government has taken no concrete steps such as improving last mile connectivity, expanding the bus fleets, encouraging the use of battery-operated vehicles, etc, to curb pollution. They just want to tackle the issue by temporary arrangements. Ban on fire cracker is not the solution, as it hurts the religious sentiments of people. The government has now seen the result. They should have allowed the use of fire crackers for a limited time period.”
The level of PM 2.5, a common air pollutant and a major respiratory health risk, in the national capital over the last 24 hours was the highest in three years, SAFAR pointed out.
PM2.5 is fine, inhalable particulate matter. It is about 30 times smaller than a strand of human hair. PM 2.5 pollutants are made up of hundreds of chemicals. Construction sites, unpaved roads, fields, and smokestacks or fires, power plants, factories, and automobiles emit these pollutants into the air. The pollutants can enter the bloodstream via the respiratory system and cause asthma, lung cancer, and heart disease.
The SAFAR analysis said that while PM2.5 levels were the highest in the three years they were still “much less” compared to 2018. It added while the levels have peaked much faster this Diwali, the dispersion is also expected to be fast. “…local winds have picked up since morning (on Friday) and now fast dispersion is expected,” the analysis said. “Without any more firecracker emissions, AQI (Air Quality Index) will improve to ‘very poor’ category by tonight (Friday) although the stubble contribution is expected to remain almost the same as today (Friday)…”
The analysis showed between 10am on Thursday and 10am on Friday, Delhi’s PM 2.5 levels climbed to 457ug/m3. This was higher than 298ug/m3 in 2020 and 377ug/m3 recorded a day after Diwali in 2019. In 2018, the PM 2.5 levels spiked to 624ug/m3.
SAFAR’s analysis said relief was expected only from Sunday evening.
Anumita Roy Chowdhury, executive director, research and advocacy at the Centre for Science and Environment (CSE), says such an episodic smog event had been forecast by agencies, owing to unfavourable weather conditions and a northwesterly wind, which is bound to heighten the impact of stubble burning. “The share of farm fires is increasing and wind speed is low which is not allowing dispersal of pollutants and firecrackers added additional emissions in Delhi’s air. All of this got trapped, leading to this season’s first ‘severe’ pollution event.”
In addition to these two major sources of pollution, Delhi had to fight high moisture content in the air, resulting in the season’s first shallow fog on Thursday morning, with visibility dropping to 500 metres at both Safdarjung and Palam. On Friday, it dropped even further, to just 200 metres. While IMD only classifies fog based on visibility, the high contribution of pollutants and toxic chemicals in the air is likely to be a major factor in reduced visibility, making this more smog than fog. Fog is generally rare at this time of the year, with the winter’s first moderate to dense fog spell usually seen in late December.
RK Jenamani, scientist at IMD, said, “Fog conditions this morning (November 5) have intensified in Delhi NCR, with moderate fog with visibility levels of 200 to 500 metres reported at its two airports – Safdarjung and Palam — till 5.30am. IGI Palam airport recorded a drop in visibility towards the city side to 200 metres,” said Jenamani.
Okhla-Phase 2 in south-east Delhi saw the biggest hourly spike in PM 2.5 concentration on Diwali day as the PM2.5 concentration touched 1,984 micrograms per cubic metre – over 33 times the acceptable level of 60 micrograms per cubic metre and nearly 397 times the new WHO standards of 5 micrograms per cubic metre. This was followed by Ashok Vihar in north Delhi, where the hourly PM 2.5 concentration touched 1,957 micrograms.
The number of people arrested in the last one and a half months until midnight on Diwali is much lesser that the police action taken on Diwali last year. In the last one and a half months, police arrested around 300 persons for stocking and bursting crackers. On Diwali last year, police arrested 850 for the two offences. On Thursday, Diwali day, the police registered 1,206 .
Despite repeated calls and messages, Delhi Police refused to comment.
IMD says wind speeds are expected to pick up only from Saturday onwards but may reach 25-35km/hr.A visible improvement in air quality might be seen from Sunday, forecasters said.
“There will still be some mist on Saturday morning but wind speeds will increase to 30-40 km/hr during the day and this will help disperse pollutants,” said a met department official who asked not to be named.