Kolkata air quality worsened during Kali Puja-Diwali as firecrackers pushed PM2.5 to 336 and several monitoring stations to very poor levels. Kolkata, Howrah Air Quality Dips Sharply Ahead of Kali Puja Amid Firecracker Use - Kolkata, – Air quality in several parts of Kolkata and Howrah has significantly deteriorated, reaching. Kolkata and Howrah air quality turns alarming before Kali Puja as PM 2.