Mumbai pollution: BMC imposes GRAP IV as air quality dips

The Brihanmumbai Municipal Corporation (BMC) has enforced the Graded Response Action Plan (Stage IV), the most severe level of anti-pollution controls, as its air quality dips. This measure primarily involves shutting down construction activities, which have been identified as a major source of air pollution in the city. 

The decision follows a period of air quality fluctuations, with the Central Pollution Control Board (CPCB) recording Mumbai's AQI at 111 in the 'moderate' category on Monday, but with several pockets having previously experienced 'severe' air quality readings. The new enforcement framework comes as BMC aims to limit public health risks and address the ongoing urban transformation driving dust and emissions across the metropolis.

Mumbai and its surrounding regions are undergoing extensive infrastructure changes, including Metro rail projects, roadwork, and large-scale building activity, leading to the replacement of older neighbourhoods with new skyscrapers. These changes have resulted in significant increases in construction-related dust, compounding vehicular emissions and other pollution sources. 

Last week, Mazgaon, an area with substantial ongoing construction, registered AQI readings of 305 on November 11th and 24th, placing it in the 'poor' category. Experts attribute recent AQI spikes to these intensive infrastructure projects, with the BMC's action plan aiming to curtail contributions from this sector through potential closures.

According to the CPCB, Mumbai’s average AQI on Sunday was 104, which is categorised as 'moderate'. However, localised spikes have occurred, such as in the Bandra Kurla Complex, where the AQI briefly reached 'severe' levels. 

Angshuman Modak of the Indian Institute of Technology Bombay pointed out, "Sea breeze circulation is also a factor. During the day, land gets heated up and clean air from the sea mixes vertically. It is much weaker in the winter. There is no proper vertical mixing of air and same amount of pollutants stays in the city." 

Sushma Nair, a scientist with the India Meteorological Department (IMD), Mumbai, has highlighted the role of temperature inversion and seasonal winds, noting, "Temperature inversion and north-easterly winds are a characteristic of this time of the season when there is transition to winter." 

The BMC has implemented several measures to address the city’s air quality, including mandating the use of cleaner fuels in bakeries and crematoriums, expanding the electric bus fleet, scientific management of construction debris, and regular sprinkling of water on roads to suppress dust.