Exclusive: Mumbai’s air pollution may be worse than what data shows

Worli and Prabhadevi shrouded in a thick morning smog on January 28. Pic/Ashish Raje

Are bureaucratic and operational inefficiencies compromising Mumbai's ability to tackle one of its most pressing environmental challenges? This question resonates among air quality experts, environmentalists, analysts, and citizens. For the past two years, Maharashtra Pollution Control Board (MPCB) and BMC have pushed for recalibration and relocation of SAFAR AQI monitoring stations, while the latter has defended its adherence to international and scientific standards. Compounding this issue, several monitoring stations have reportedly been offline, either entirely or for most of the day for months, disrupting accurate tracking of air quality trends.

A 2024 analysis of data from all 30 AQI monitoring stations revealed significant inconsistencies and gaps in Mumbai's AQI readings, raising concerns about the credibility of the city's overall pollution data. As a result, what residents perceive in reality may starkly differ from what the indices report, undermining effective policy and citizen awareness efforts to combat pollution.

While observing air quality trends since November 2024, mid-day found that AQI monitors in Mumbai and MMR, installed by IITM (Indian Institute of Tropical Meteorology), MPCB, and BMC, yielded data with missing crucial inputs. Some stations would display messages like "No Available data" or "Insufficient data for computing AQI" for hours.

SAFAR AQI monitoring station in Mazagaon. Pic/Shadab Khan

Several pollution hotspots lacked data inputs for significant periods. Monitoring stations in Bandra Kurla Complex and Bandra had no inputs for several days. A second monitoring station in BKC operated by Maharashtra Pollution Control Board (MPCB) showed no signal for several hours on most days, similar to stations in Kandivli East, Deonar, Siddharth Nagar in Worli, and Vile Parle East.

The Chakala (Andheri East) AQI monitoring station has displayed "Insufficient data for computing AQI" since July 8, 2024. After seven months, the situation remains unchanged. Additionally, since January 2, 2025, the Kandivli West AQI monitoring station operated by BMC has gone offline with the same message. The stations at Bandra and BKC (IITM) have shown no data for months.

ExpertSpeak

According to Sunil Dahiya, founder and lead analyst at EnviroCatalysts, CPCB data from Mumbai's AQI monitoring stations during 2024 reveals significant gaps in data availability, with some stations dysfunctional for months and others consistently reporting missing hourly readings.

Dahiya noted that the BKC station, managed by IITM, has been offline since December 2023, with minimal data recorded throughout 2024. The Chakala station has been offline since July 2024, while the Mazagaon station was inactive from May to October 2024. The Siddharth Nagar station in Worli was offline from July to September 2024. Furthermore, the Bandra station (MPCB) has shown no data throughout 2024.

SAFAR AQI monitoring station in Borivli East. Pic/Anurag Ahire

Dahiya said that gaps in data collection indicate inefficient use of invested resources and infrastructure. "Prolonged data unavailability hampers accurate analysis at local hotspot levels and affects longer-period averages. Setting up monitoring stations only to have them remain offline wastes resources," he stated. Mohsin Khan Pathan, senior project associate at Waatavaran Foundation, explained that real-time monitoring stations' completeness is evaluated based on valid 15-minute intervals reported annually.

"Daily 24-hour averages require at least 16 hours of data per day, with 75 per cent annual completeness needed for reliable analysis. Many stations lack monitors for key pollutants, particularly PM2.5 and ozone. Poor distribution of monitoring results and uneven population coverage create significant gaps in data generation, hindering trend analysis," Pathan said.

His recommendations include expanding monitoring networks with better spatial planning, extending coverage to rural areas, focusing on high-risk pollutants, integrating hybrid monitoring systems, and maintaining equipment regularly. "Real-time health advisories via mobile notifications would help sensitive populations take necessary precautions," he added.

A CPCB official confirmed that not all station values are used for computing city-wide AQI due to power cuts, data publication delays, and maintenance issues.

MCAP perspective

Even the Mumbai Climate Action Plan (MCAP), released in 2022, recognises data monitoring, collection, and archiving, as well as institutional coordination, as key gaps. MCAP mentions: "The current air quality landscape of the city highlights several multi-pronged sectoral challenges related to data monitoring, inventorisation, collection and archiving, institutional coordination, awareness and capacity building, congestion and large-scale fuel emissions, increased suspended dust, and waste management."

MCAP states under the sectorial priority for air quality management in Mumbai that there should be an emphasis on and prioritisation of increased availability of data and information by strengthening and decentralising the pollution monitoring and forecasting mechanism. This would enhance the health resilience of vulnerable communities. Hence, MCAP highlights the need for increasing information availability through improved monitoring, forecasting, and awareness programs as part of sectoral action tracks.

Further, as part of these sectoral action tracks, MCAP has recommended developing ward-level action plans to prevent and reduce open waste burning, along with campaigns against indiscriminate burning of garbage, biomass, and crop residues. The timeframe for these action tracks was from 2022 to 2024. However, nothing has been done on these lines by the BMC.

Apart from this, MCAP also recommended preparing site-specific air quality data repositories for disseminating information on poor air quality and corresponding occupational health hazards at the site. The action tracks began in 2022 and were intended to be continuous site-specific activities.

As part of other priority actions, MCAP recommended that MPCB increase the number of monitoring stations, such as Continuous Ambient Air Quality Monitoring Stations (CAAQMS), equipped with low-cost indigenous sensors and real-time monitoring technology, based on CPCB criteria for site location. It also urged the Mumbai civic body to develop a robust data survey mechanism to address the issue of varied types of personal exposure to different air pollution risks.

"Reliable data is the cornerstone of an effective air quality management strategy, especially for a city as dynamic and densely populated as Mumbai. Expanding the network of air quality monitoring stations by incorporating more Continuous Ambient Air Quality Monitoring Stations (CAAQMS) and hyperlocal sensors is essential to gain a clearer understanding of pollution sources, underlying causes, and critical hotspots. This data plays a vital role in enabling informed governance and facilitating ward-level actions tailored to local needs. Moreover, mapping vulnerable populations and assessing their exposure to pollutants is crucial for implementing targeted interventions that can safeguard public health. Accurate data and analysis not only enable immediate responses but also form the foundation for long-term planning to sustainably improve the city's air quality," said Sree Kumar Kumaraswamy, programme director, Clean Air Action - WRI India.

The tussle

There are a total of 30 stations in the Mumbai region, which includes one in Vasai. Of these 30 stations, 16 are Continuous Ambient Air Quality Monitoring Stations (CAAQMS) in the city operated by MPCB, nine by IITM/SAFAR, and five by BMC. The CAAQMS operated by MPCB usually records lower levels of AQI compared to the SAFAR monitoring systems.

Over the past two years the MPCB has sought to relocate nine stations run by SAFAR, claiming they do not accurately reflect Mumbai's ambient air quality. In 2023, MPCB submitted a report on inaccurate AQI readings by SAFAR monitors. These monitors are managed by the IITM, Pune, an autonomous institute of the Ministry of Earth Sciences.

Allegations of inaccuracy against SAFAR systems have been disputed by senior officials from the IITM, Pune. When asked about offline stations, especially the ones at Chakala and BKC, Dr Sunil Ghude, Scientist at IITM, Pune, explained: "Both of our stations are currently offline: BKC due to a power issue, and Andheri due to vandalism at the site by external parties. However, we are continuously feeding data into the SAMEER app of CPCB. All other stations are operational, and the data can be accessed at the SAFAR portal. Additionally, the Navi Mumbai station at Nerul, maintained by NMMC, has disconnected its power supply. This action appears to be unrelated to the station's maintenance. The station had been showing higher AQI levels, likely due to local construction activity and the nearby highway."

When questioned about the significant difference between the readings of MPCB stations and IITM stations, and the resulting confusion among the public, Ghude replied: "Please be informed that our BKC station is currently closed due to power issues. At the Borivli East station, significant construction is taking place near the site. However, the MPCB station in Borivli is located farther from our site, where no construction is occurring. Since Colaba is close to the seashore, ship emissions frequently influence the readings there. Additionally, the MPCB station in Colaba is situated 2-3 km away from the IITM station. It's essential to understand that an Air Quality Monitoring Station (AQMS) represents air quality in the immediate area, usually within a 500-metre to 2-km radius. Therefore, when comparing data, these factors must be considered."

Regarding allegations of inaccuracy by MPCB officials, Ghude clarified, "We respectfully disagree with the views expressed by both MPCB and BMC, as SAFAR is a research-driven project dedicated to maintaining the highest standards of data quality. Last year, we submitted a thorough report on this issue. We conduct monthly calibrations and regularly share the data with BMC. Calibration reports are available for public access if required. Additionally, we have a dedicated team of five engineers monitoring the stations in Mumbai and three engineers in Pune, ensuring the proper functioning of the stations on a daily basis."

What can the solution be?

Speaking on the gaps in the air quality monitoring system, Dr Rakesh Kumar, president of the Society for Indoor Environment (SIE) and former Director and Head of the NEERI Zonal Centre in Mumbai, said, "National Ambient Air Quality Standards (NAAQS) require a minimum of 104 monitoring days per year for manual stations, which translates to twice-weekly 24-hour monitoring. Failure to meet this 104-day requirement results in deficient monitoring, leading to insufficient data and, consequently, inaccurate annual averages. Mumbai has multiple agencies monitoring air quality, including MPCB, BMC, and IITM, which is not an issue at all. However, I believe the process of releasing data for public access should be centralised. This is a common international practice but is lacking in some cities, including Mumbai. As a statutory body, MPCB needs to take control of the data collection and reporting process. Data collation and public communication are the MPCB's responsibilities."

Addressing concerns about the accuracy of IITM's air quality readings, Dr Kumar clarified: "No, the data and readings from IITM stations do not appear to be inaccurate. However, the readings are often higher at their stations because most of them are located in hotspots or designated curbside areas. While curbside data is crucial for identifying and addressing specific problem areas, it does not represent the overall air quality of the city; it reflects conditions in a localised pocket or hotspot."

Dr Kumar emphasised the need for a redesignation of AQI stations or CAAQMS, recommending a comprehensive study of Mumbai: "The city requires an in-depth study that takes into account infrastructural changes, emission levels, and other factors. For instance, CPCB protocols specify that monitoring stations should be set 12-15 metres away from hotspots or curbsides. However, there are no guidelines on the proximity of greenbelts or green patches. Over time, Mumbai has undergone significant demographic and infrastructural changes, such as taller buildings, more vehicles, and altered meteorological conditions. I strongly recommend conducting a study that evaluates these changes comprehensively. Based on the findings, the locations of existing AQI monitoring stations should be reassessed and redesignated to ensure they accurately represent the city's air quality."

Meanwhile, in the absence of health alerts and public health advisories from MPCB, BMC, or the state government, NGO Awaaz Foundation has been collating data from the CPCB portal/SAMEER app and posting PM2.5 readings on its official X handle. Talking about their social media campaign and the scientific jargon around air quality, Sumaira Abdulali, founder and convenor of Awaaz Foundation, said: "Instead of confusing the public, it is for the MPCB and BMC to issue public health alerts and advisories. They are not doing anything on that; instead, they are fighting each other over whose data is accurate and whose is not. They need to work on the gaps in data and AQI monitoring and make simple, accessible data available to the public. This should include advisories on their phones, similar to flood and rain alerts. Since September 2024, we have been posting PM2.5 readings daily as part of a social media campaign. I feel there is not just a gap in data monitoring and reading but also in communication. It's a huge failure on the part of planning and monitoring authorities if they are not reaching out to the public."

Residents say

Pankaj Trivedi, a resident of Srikrishna Society, Borivli East, expressed his frustration with air quality monitoring. "These apps are confusing. Despite regular garbage burning and pollution in the area, stations often report low or moderate AQI. There are two stations in Borivli East, and their readings differ significantly." Trivedi added, "I don't believe these monitoring stations accurately reflect the actual conditions."

Abhinav Kamal, who works in BKC, highlighted the health impacts of pollution and data inconsistencies: "There's constant dust and pollution in BKC, which affects health. One of the AQI stations here is defunct, and the other consistently shows moderate levels. Even at home, the Chakala station hasn't worked for over a year. These apps have become meaningless to follow."

Abhinav also noted the growing congestion in BKC, "Traffic has quadrupled since I started working here 11 years ago."

How bad is the air?

According to IQAir, a Swiss firm, India ranked third among the world's most polluted countries/regions from 2018 to 2023. The ranking is based on the annual average PM2.5 concentration (μg/m³). As per IQAir's live city AQI rankings on Tuesday, January 28, at 12.47 pm, Mumbai was the sixth most polluted city in the world. Kolkata ranked second, while Delhi was fourth