For the past five Diwali nights, the bursting of firecrackers has sent the air quality, which is in any case toxic at this time of year, to emergency levels, maxing out nearly all monitors in the city.
According to data from the Central Pollution Control Board (CPCB), the air in Delhi remains severely polluted for a week after Diwali due to a combination of emissions from firecrackers, farm fires in neighbouring states, and adverse weather conditions.
This means that the slight improvement in Delhi’s air since Wednesday — it went from “severe” to “very poor” — may be short-lived, a possibility experts have flagged in recent days, if the cracker ban is not strictly followed.
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The AQI on Friday was 339, while it was 314 on Thursday.
“The key this year will be to enforce the cracker ban effectively. Last year, because of an early Diwali, and better enforcement, we saw our first “severe” air day only after Diwali. But this year, we have already experienced a week of severe air quality,” said Anumita Roychowdhury, executive director (research and advocacy), Centre for Science and Environment.
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CPCB data shows that over the past five years, the pollution levels in the city have remained in the “severe” levels in the days following Diwali. Last year, despite slightly better wind speeds, the air quality index (AQI) on Diwali day (October 27) was 337, in the “very poor” category. In the subsequent days, the air quality continued to deteriorate and on October 29, the AQI was 400. The next day, it rose further to 419.
In 2018, a similar trend was seen. On November 7, Diwali day, from an AQI of 281 (poor category), it rose to 390 the next day, a tad short of the “severe” zone. The subsequent day, the AQI climbed to 423.
According to Roychowdhury, last year, despite favourable weather conditions and increased enforcement, pollution levels remained high simply because too many firecrackers were used.
On a scale of 0 to 500, an AQI value between 301 and 400 is considered “very poor”, while values between 401 and 500 are considered “severe”.
To assess the impact of firecrackers on Delhi’s air this year, the CPCB has directed the state pollution control boards of Delhi and NCR towns to conduct detailed ambient air quality monitoring in two or three localities, so as to understand the trend. In Delhi, the areas chosen for this monitoring are Pitampura, Janakpuri and ITO.
“It will be a 15-day study, assessing the air quality seven days before Diwali and seven days after Diwali. Noise monitoring assessment will also be carried out from November 9 to November 14,” a statement by CPCB on Friday said.
Senior CPCB officials said in that in northwest Delhi’s Pitampura area, the levels of PM10 (particulate matter with diameter less than 10 micrometres), sulphur dioxide (SO2), nitrogen dioxide (NO2), PM2.5 (ultra fine particulate matter with diameter less than 2.5 micrometres), and metals in PM10 (lead, nickel, arsenic) will be monitored.
In Janakpuri, the levels of metals in PM2.5, such as aluminium, barium and iron will be monitored.
Noise pollution assessments will be conducted in six areas in Okhla, Lajpat Nagar, Mayur Vihar Phase-2, Kamla Nagar, Pitampura and Janakpuri from 6pm to midnight on Diwali.
Real-time noise monitoring will also be done at 10 places in Dilshad Garden, RK Puram, Civil Lines, Anand Vihar, Dwarka and Punjabi Bagh.
A Centre for Science and Environment (CSE) analysis of the air quality during the Diwali week in 2019 showed that in Delhi-NCR the concentration of PM 2.5 levels jumped 10-fold in the seven hours starting 5pm on Diwali evening.
This was alarming as Diwali last year was celebrated earlier than usual, which means the city was warmer and had favourable conditions for the dispersal of pollutants.