Kolkata, Oct 31 (IANS): With the Air Quality Index (AQI) in Kolkata already showing signs of deterioration since Wednesday evening, the pollution level is expected to be alarmingly high on Thursday night when the bursting of firecrackers will be maximum on the occasions of Kali Puja and Diwali.

On Wednesday evening, the AQI levels in Kolkata crossed 100, which is considered as unhealthy for sensitive groups especially elderly citizens. Similar deterioration in AQI levels has been witnessed in various pockets in Kolkata and the adjacent district of Howrah.

According to environmental activists, with the AQI levels crossing 100 in most places of the city on Wednesday evening when the bursting of firecrackers was minimal, it is well imaginable what the situation will be on Thursday night when cracker bursting will be at maximum.

AQI levels within 101 and 160 come within the orange category. At this level, elderly citizens, children and people with respiratory problems like that of asthma are advised to avoid prolonged outdoor activities.

As witnessed during the last few years, the air quality in Kolkata starts worsening from the second and third week of October because of the city's pre-winter spike in accumulation of pollutants in the air. So was witnessed in the third week of October this year when, on a day, AQI at a particular monitoring station slipped into the unhealthy category which is between 201 and 300 and comes under the purple category.

However, environmentalists believe that the continuous heavy showers as an impact of the landfall of Cyclone Dana last week improved the situation to a great extent.

Every year, the same phenomenon is witnessed where the AQI levels deteriorate sharply from the night of Kali Puja and Diwali and remain poor for the next few days.

Kolkata Police have announced that they will deploy additional police personnel at the residential areas to quickly address complaints related to fire-crackers. Associations of different high-rise buildings in the state have been advised to keep their terraces locked on Thursday.