MUMBAI, Dec. 4 -- A total of 19 Ready Mix Concrete (RMC) plants, crucial to the widespread construction activity currently underway in Mumbai and surrounding areas, have been shut to keep air pollution in check. The action has been taken by the Maharashtra Pollution Control Board (MPCB), which operates 32 air quality monitoring stations in the Mumbai Metropolitan Region (MMR). Of these, 14 are in Mumbai and 18 in satellite townships such as Kalyan, Navi Mumbai and Panvel. The MPCB, which had issued revised guidelines for RMC plants across the state in October, is conducting a survey of compliance. As a result, violations were detected and, accordingly, four RMC plants in the Deonar-Govandi area have been shut. Also shut are eight in Thane, six in Navi Mumbai and one in Kalyan. The four plants in Mumbai are operated by Om Gehlot Operator, NCC Ltd, Ramky Infrastructure Ltd and Construction Pvt Ltd. After the Brihanmumbai Municipal Corporation (BMC) started cracking down on polluting RMC plants in Mumbai, as AQI reached worrying levels, the MPCB initiated a survey to check compliance with its pollution guidelines. Three unauthorised metal-processing furnaces in Sanjay Gandhi Nagar, Sion, had earlier been ordered to shut down, and the BMC has now removed these illegal furnaces, the MPCB said. During its survey in the Wadala-Mahul area, it was found that garbage was being burnt in certain areas along the MbPA Road in the evening. The port authority has been instructed to take preventive measures. Meanwhile, Mumbai's overall Air Quality Index (AQI) has stabilised. It remained in the 'moderate' category on Wednesday, at AQI at 128, according to the Central Pollution Control Board's air quality bulletin. Most monitoring stations stayed within the 'moderate' range, even though several neighbourhoods continued to show elevated pollution driven by localised spiked in PM2.5 particulate matter. The highest levels were recorded at Kherwadi-Bandra East, where AQI was 196 and PM2.5 concentrations jumped to 309. Shivaji Nagar registered an AQI of 184 and a PM2.5 spike of 303 late on Monday night. Other stations, including Sewri (175), Ghatkopar (179), Borivali East (172) and Chembur (159), remained above the city's average, indicating persistent localised emissions despite overall improvement. Meanwhile, minimum temperatures rose marginally. At Santacruz, the maximum temperature reached 33.0degC, 0.5degC below normal, while the minimum settled at 18.0degC, 2degC below normal, higher than Tuesday's 17.7degC. At Colaba, the maximum temperature reached 33.8degC, 0.8degC above normal, while the minimum was 21.3degC, still 1.2degC below normal. An IMD official said, "Minimum temperatures will fluctuate between 19degC and 20degC for the next three to four days. Northerly winds, which kept the nights cool, have begun to ease."...