According to TNPCB, the air quality index was found to be moderate in Triplicane, satisfactory in Sowcarpet and good in Besant Nagar, T Nagar and Nungambakkam. However, the Central Pollution Control Board’s real-time air quality index revealed a different picture. TNPCB said that PM10 (particulate matter in the ambient air below the size of 10 microns) results ranged from 52 to 111 microgram per cubic meter (µg/m3 ) during Deepavali day against the prescribed limit of 100 µg/m3. In 2019, on Deepavali, the PM10 level ranged from 84 to 128 µg/m3.
On Saturday, the PM 2.5 (Particulate matter of less than 2.5 microns) results ranged from 32 to 59 µg/m3 against the standard of 60 µg/m3. “The PM10 values were within the limit in all stations during Deepavali day except in Triplicane and Sowcarpet where it was marginally higher at 111 µg/m3 and 100 µg/m3. PM2.5 levels were also well within the limit. Gaseous pollutants namely SO2, NO2, were found to be within the prescribed standard of 80 µg/m3,” it said. Contrary to the TNPCB data, the Central Pollution Control Board’s real-time air quality index at 9 pm on Sunday ranged from moderate to severe. According to them, stations at Arumbakkam, Kodungaiyur, Manali Village and Royapuram recorded AQI ranging from 302 to 500 while those at Alandur, Manali and Velachery recorded AQI ranging from 149 to 310. AQI between 401 and 500 is considered severe, which affects healthy people and seriously impacts those with existing diseases. Ambient noise level ranged from 54 to 69 decibel (dB) during pre-Deepavali (November 9) and ranged from 71 to 78 dB on Deepavali. It was observed that the values were found to be lower for Deepavali, and ranged from 4-6 Leq — equivalent continuous sound level in decibels — when compared to 2019.