Many Delhiites felt that decibels levels on Diwali night were a shade lower than previous years, but the dense haze of near-choking pollution told a different story. Now the verdict is out. The PM 10 (coarse particles) levels this year were found to be higher compared to last year at all monitoring locations in the city, the Central Pollution Control Board said.
Levels of sulphur dioxide, associated with breathing difficulty and other respiratory ailments, were also higher, according to Delhi Pollution Control Committee data.
Interestingly, the noise levels were higher than last year in many east and north Delhi areas — Mayur Vihar, Dilshad Garden, Kamla Nagar and Pitampura — but were lowered in south and central locations such as Ansari Nagar near AIIMS , ITO and Lajpat Nagar.
Even though there isn’t much of a difference in other parameters like nitrogen dioxide (NO2), PM 2.5 and carbon monoxide (CO) as compared to 2012, the peaking levels of these pollutants were extremely high on Sunday evening.
Weather conditions also played a part. The average wind speed (0.36m/sec) was lower compared to last year (0.43 m/sec) which meant that pollutants like PM 10 hung in the air instead of dispersing.
A lower mixing height (atmospheric zone of almost stable temperature and specific humidity) than last year also aggravated the condition by keeping pollutants trapped.
According to CPCB, PM 10 levels increased quite a bit from 2012, the maximum level rising by about 187 microgram per cubic metre. NO2 levels decreased at most locations while SO2 decreased at five locations but increased at two — Pitampura and Shahzadabagh . But DPCC, which monitors other locations in the city, found that SO2 levels were higher compared to 2012 — the maximum level increasing by about 26 micrograms per cubic metre.
“It’s a cause for concern. SO2 is an extremely harmful pollutant. On normal days, SO2 in Delhi is usually much below the standard. The fact that it has increased so much on Diwali points to the kind of crackers that are being manufactured ,” said Anumita Roychowdhury , executive director , research and advocacy, Centre for Science and Environment (CSE).
In fact, there could be a worrying trend hidden in the sudden peaks of certain pollutants measured real-time by DPCC. For instance, SO2 levels went up to 345 microgram per cubic metre at 11pm in RK Puram on Sunday and to 570 microgram at IGI Airport around 12.30am. NO2 levels spiked to 464 micrograms at 11.30pm in Punjabi Bagh and the PM 2.5 level at R K Puram was recorded at a high 643 microgram . These peaks are not shown in the range given by DPCC for Diwali day.
At Anand Vihar, both PM 10 and PM 2.5 were exceedingly high. PM 10 level was 13 times the permissible limit. “The levels are high in Anand Vihar also because of heavy vehicular traffic because it’s near the border with Ghaziabad ,” said M P George from air and water lab at DPCC.