NEW DELHI: A new report released by Central Pollution Control Board (CPCB) on ‘ambient air quality during Deepawali festival 2020’ says Delhi (82.9%) saw the highest PM2.5 spike in the country on Diwali day as compared to pre-Diwali day. Delhi reported the third highest increment in PM10 on Diwali day after Lucknow and Bhopal in the country. The report says arsenic crossed the prescribed annual concentration limit on Diwali day in Delhi, Agra, Lucknow, Kolkata and Bhopal. CPCB conducted monitoring in eight cities—Delhi, Agra, Bhopal, Bengaluru, Kolkata, Lucknow, Shillong and Vadodara—for pre-Diwali (November 7 to November 14), Diwali (November 14) and post-Diwali period (November 15 to November 21). According to the report, highest PM2.5 was recorded in Delhi (82.9%) followed by Bhopal (81.3%), Lucknow (67.6%), Kolkata (53.6%), Shillong (30.5%) and Vadodara (26%) on Diwali day as compared to pre-Diwali day. Highest increase in PM10 on Diwali day was reported in Lucknow (114%) followed by Bhopal (86.2%), Delhi (67.1%), Shillong (53.7%) and Kolkata (22.6%). “During the entire Diwali monitoring period, 24-hourly averages of both PM10 and PM2.5 were found above the National Ambient Air Quality Standard—100 µg/m3 (PM10) and 60 µg/m3 (PM2.5)—in all cities, except Bengaluru and Shillong,” stated the report. Sulphur dioxide (SO2) was found always within the prescribed 24-hourly limit of 80µg/m3 throughout the monitoring period, including Diwali day, but an increase in SO2 concentration was observed on Diwali day in cities like Delhi, Lucknow, Bhopal and Vadodara. “Increase on Diwali day may be attributed to oxidation of sulphur due to bursting of crackers. Bengaluru and Shillong reported SO2 at Below Detection Limit (4 µg/m3),” said the report. Nitrogen dioxide was reported within the prescribed 24-hourly limit (80µg/m3) in all the cities, except Delhi during pre-Diwali, Diwali and post Diwali days. Similarly, arsenic crossed the prescribed annual concentration limit on Diwali day in Agra, Delhi, Lucknow, Kolkata and Bhopal.