The Chief Justice interjected, "No, no... that was only two days ago. Even before that, we couldn't see beyond 500 metres." He refused to accept the explanation given by the state government for the deteriorating air quality. "You tell us what measures are going to be taken," the Chief Justice said. The Court further observed that steps to control pollution had not brought any visible improvement in air quality.

As per the air quality parameters, an AQI between 0-50 is considered 'good', 51-100 'satisfactory', 101-200 'moderate', 201-300 'poor', 301-400 'very poor', and 401-500 'severe'.

The Court also directed the Brihanmumbai Municipal Corporation (BMC) to take "concrete steps" to check pollution levels. The BMC has decided to enforce the GRAP IV (Graded Response Action Plan) in case the AQI in certain pockets in Mumbai does not reduce below 300 for three consecutive days. The measure involves closure of construction sites, considered a major contributor to Mumbai's pollution load.

The Mazgaon area, Mumbai's industrial hub, witnessed the AQI shooting up twice to 305 -- on November 11 and on November 24. On Thursday, Mumbai's AQI was 198, the highest this month. At least half a dozen AQI stations in the city recorded a reading of 200.