Mumbai, Oct. 13 -- Days after the Indian Meteorological Department (IMD) announced withdrawal of the monsoon from Mumbai, the city's air quality has deteriorated steadily and is expected to worsen further as Diwali approaches. According to data from the Central Pollution Control Board (CPCB), the city's Air Quality Index (AQI) showed a consistent decline over the past week. The month began with 'good' air quality levels, which slipped to the 'satisfactory' category between October 5 and 9. By Friday, the overall AQI had deteriorated to 134, and further rose to 152 on Saturday, placing it in the 'moderate' category. On Friday, the IMD declared the monsoon withdrawal on October 10. As per the IMD, this year's monsoon began on May 26, its earliest onset since 1950, and ended on October 10, its earliest withdrawal since 2018. "The moisture in the air during monsoon helps suppress dust particles, allowing for cleaner air. After the rains recede, it usually takes some time for the atmosphere to dry before pollution levels start to rise. But this year, the deterioration was immediate," said Dr Gufran Beig, chair professor at the National Institute of Advanced Sciences (NIAS). "This happened because wind movement along the western coast was sluggish, preventing dust particles from dispersing and causing them to remain trapped in the lower atmosphere," he added. On Sunday, the city's overall AQI averaged 153, based on readings from 25 of the 30 continuous air quality monitoring stations in the city. Except for Borivali East, with an AQI of 91, and Sion, with an AQI of 90, which remained in the 'satisfactory' range, 22 stations recorded AQI levels above 100. Deonar reported the poorest air quality, logging an AQI of 253. Areas such as Bandra Kurla Complex (AQI 194), Kandivali West (AQI 193), Vasai West (AQI 186) and Kandivali East (AQI 186) were nearing the 'poor' category threshold of 200. As per CPCB standards, an AQI between 0-50 is considered good, 51-100 satisfactory, 101-200 moderate, 201-300 poor, 301-400 very poor, and above 400 severe. With the upcoming Diwali festival, the air quality is further expected to worsen and deteriorate with the bursting of crackers, the officials said....