OPINION | Understanding Mumbai’s AQI: The Lack Of A Unified Architecture

It’s easy to dismiss air quality as a problem at this time of year. Summer and the rains keep our air relatively breathable until the weather cools. It is equally the best time to keep our attention on the problem, which will arise in due course.

Source : PTI

The Indian Constitution protects the right to a clean and healthy environment and imposes an obligation on the State to protect and improve the environment. That said, the air quality crisis across the country speaks for itself.  

Turning specifically to Mumbai, it’s trite and contextually relevant to reiterate that Mumbai is part of the  Mumbai Metropolitan Region (MMR); 6,300 sq. km of densely populated geographies extending across  Thane, Navi Mumbai, Raigad, Kalyan-Dombivli, Vasai-Virar, and adjoining areas. Industrial activity,  transport emissions, construction dust, peri-urban expansion, and coastal atmospheric circulation operate continuously across the MMR and the complexity of larger air circulation patterns is compounded by diurnal land and sea breezes. 

Estimates cited by IIT Bombay suggest that approximately half of Mumbai’s PM2.5 burden may originate beyond the city itself. Road dust, vehicular emissions, industrial activity, construction dust, and secondary aerosol formation remain the principal contributors.  

The Maharashtra Pollution Control Board (MPCB) increasingly recognises the MMR as a single atmospheric system. Recent enforcement action against ready-mix concrete plants across Thane, Navi  Mumbai, and Kalyan reflects an operational understanding that pollution affecting Mumbai frequently originates outside municipal boundaries. 

Reporting systems, the media, and such action as is taken, all continue to focus on Mumbai as a stand-alone city disjunct from the MMR. This necessarily precludes any meaningful redress since, again tritely but necessarily reiterated: An unidentified problem can’t be understood and can’t be addressed (leave aside redressed). 

The Environment (Protection) Act, 1986, and the Air (Prevention and Control of Pollution) Act, 1981, empower authorities to prescribe environmental standards, collect information, monitor pollutants, and coordinate enforcement. 

The MPCB operates monitoring stations under the National Air Monitoring Programme, the State Air  Monitoring Programme, and Continuous Ambient Air Quality Monitoring Stations (CAAQMS). In 2024,  Maharashtra had 167 monitoring stations, including 69 real-time CAAQMS. Coverage within the MMR  remains uneven, with several densely populated urban regions relying on a single station.  

Recent initiatives by the Brihanmumbai Municipal Corporation (BMC), MPCB, and IIT Kanpur seek to expand monitoring through additional CAAQMS stations, hyperlocal sensor deployments, and construction-site monitoring mandates.  

However, MPCB, BMC, CPCB, SAFAR, and independent sensor networks generate data through differing methodologies, calibration standards, and reporting systems. There exists no unified regional platform that aggregates or standardises this information. Studies have also identified calibration failures, flatlined pollutant readings, unit inconsistencies, and siting errors across monitoring stations. 

The Need for a Unified Data Spine 

The MMR requires a unified ‘data spine’, an interoperable regional architecture capable of aggregating, calibrating, standardising, and analysing air-quality information across agencies and jurisdictions. 

Such a framework would integrate reference-grade monitoring stations, low-cost sensors, satellite observations, mobile sensor units, and predictive analytics into a single operational system. It would also support real-time public dashboards, hyperlocal forecasting, and targeted enforcement.

The statutory framework set out above is endorsed in Vellore Citizens Welfare Forum v. Union of India and the actions in the Bombay High Court in PIL number 3 of 2023.  

The financial case for integrated monitoring is equally strong. 

A hybrid monitoring system combining reference-grade stations with calibrated low-cost sensors can achieve substantially greater spatial coverage at lower cost than a purely reference-grade network. IIT Kanpur conducted a pilot project which demonstrated that such a framework could generate more than  1,200 air-quality datapoints across Greater Mumbai at a fraction of conventional monitoring costs.  

The pilot, however, was never scaled. 

The MMR’s air quality challenge is, at present, fundamentally a data governance challenge. The legal framework already permits integrated action, and the technology already exists to build a better system.  What is missing is a unified architecture that treats the MMR as a single airshed, ensures calibration and standardisation, fills spatial gaps, and produces evidence strong enough to support enforcement,  planning, and public accountability. The missing data spine is the missing foundation on which we can begin to address and redress our crisis of air quality.

It’s easy to dismiss air quality as a problem at this time of year. Summer and the rains keep our air relatively breathable until the weather cools. It is equally the best time to keep our attention on the problem, which will arise in due course. I can’t say that we must prepare, but we should do everything we can to keep the authorities’ eye on this ball so that we can actually start making progress towards enjoying our fundamental right to clean air.

Justin M Bharucha is a Managing Partner at Bharucha & Partners.

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