'Poison In The Air': Richa Chadha's Alarm As Mumbai's AQI 'Beats' Delhi's, BMC In Line Of Fire

News cities mumbai-news 'Poison In The Air': Richa Chadha's Alarm As Mumbai's AQI 'Beats' Delhi's, BMC In Line Of Fire

Last Updated:October 24, 2026, 15:31 IST

Mumbai’s sea breeze is no longer keeping pollution at bay, as farm fires, garbage burning and construction add to the haze. Are unreliable sensors masking the problem?

Mumbai has long benefited from its coastal location, with winds from the Arabian Sea helping disperse pollutants generated by traffic, construction and other urban activities. But as the city’s air quality deteriorates, that natural advantage appears less effective, raising questions about what is driving the pollution and whether monitoring systems are accurately capturing its extent.

The contrast with Delhi is striking. While winter pollution in the national capital is associated with weak winds, farm fires and emissions accumulating close to the ground, Mumbai is also experiencing poor air quality despite its proximity to the sea. Sluggish winds, construction dust, vehicle exhaust, open waste burning, agricultural fires and festival-season firecrackers are among the factors experts have identified.

The concern is no longer limited to how polluted Mumbai’s air has become. Questions are also being raised about whether the readings displayed at some construction sites accurately reflect conditions on the ground. Recent reports have highlighted substantial differences between nearby sensors, even as the Brihanmumbai Municipal Corporation (BMC) prepares to use artificial intelligence to monitor thousands of devices.

Mumbai’s AQI Has Exceeded Delhi’s, But What Do The Numbers Show?

Mumbai’s air pollution has repeatedly drawn attention this year, including periods when its AQI was higher than Delhi’s. According to a report in India Today, the city recorded an AQI of 152 on October 15 on the IQAir platform, placing it fifth globally in that ranking and at the top among Indian cities listed at the time.

However, AQI figures need to be compared carefully. IQAir uses the US AQI scale, while India’s Central Pollution Control Board (CPCB) follows the National AQI system. On October 15, Mumbai’s reading on the CPCB scale was reported at 98, compared with 152 on IQAir’s US scale. These figures are not directly interchangeable.

Mumbai’s pollution has also fluctuated considerably across locations and dates. An India Today report published on October 9 said the city’s AQI had climbed to 197 during an earlier spell of deteriorating air quality. The report linked the worsening conditions to the post-monsoon period and rising particulate pollution.

On October 23, the AQI tracker reported a city average of 153. The following day, its neighbourhood data showed readings ranging from 94 in Worli to 158 in Khindipada-Bhandup West. These figures illustrate how pollution can vary across the city, even within the same reporting period.

The comparison with Delhi is therefore not a fixed contest between two cities. AQI changes with the time of measurement, weather conditions, monitoring locations and the scale used. What matters for Mumbai is the repeated deterioration of its air quality and the combination of emissions and weather that can allow pollution to accumulate.

Why Is Mumbai’s Sea Breeze Not Clearing The Air?

The Arabian Sea has traditionally helped Mumbai disperse pollution by bringing in moving air and carrying emissions away from densely built-up areas. But this advantage depends on wind speed and direction. When winds weaken, pollutants released by vehicles, construction sites and other sources can remain concentrated over the city for longer.

Gufran Beig, chair professor at the National Institute of Advanced Studies on the IISc campus, said that the overall wind speed had been slowing. In a coastal city accustomed to stronger winds, he said, even a modest reduction in air movement could allow pollution to build up.

In simple terms, emissions do not disappear when they leave a vehicle exhaust or a construction site. They need to be dispersed or removed from the atmosphere. If the air remains relatively stagnant, pollution can accumulate near ground level, increasing people’s exposure.

Temperature patterns can also influence how pollutants move. Beig said El Niño conditions were expected to contribute to a relatively mild winter, with temperatures potentially remaining higher than usual. Warm air near the surface can rise and carry pollutants upwards, but the way that air interacts with cooler layers above can influence how far pollutants travel and how effectively they disperse.

These atmospheric processes are complex, and no single weather factor explains every increase in Mumbai’s AQI. The key point is that the city’s coastal setting cannot guarantee clean air when winds are weak and emissions continue.

Can Farm Fires In Madhya Pradesh And Jharkhand Affect Mumbai?

Agricultural burning is another possible contributor to Mumbai’s pollution, although the effect depends on the location of the fires, wind direction, wind speed and the time pollutants spend travelling through the atmosphere.

Beig told India Today that winds during October and November generally come from the north-east of Mumbai. Under suitable conditions, they may carry emissions from areas such as Madhya Pradesh and Jharkhand towards the city, where crop-residue burning also occurs.

He cautioned, however, that these states are a considerable distance away and that winds may weaken before reaching Mumbai. He also said prevailing winds were unlikely to transport stubble-burning pollution from Delhi, Punjab and Haryana directly to Mumbai during the period being examined.

The assessment differs from the one Beig discussed with India Today in February, when he pointed to east-to-west winds as a possible route for carrying emissions from fires inland towards Mumbai. The change illustrates why pollution transport needs to be assessed against current weather patterns rather than assumed to follow the same route throughout the year.

A 2018 report by Down To Earth, citing research by Indian and US scientists, had also discussed how pollutants from agricultural burning in Punjab, Haryana and western Uttar Pradesh could travel beyond northern India, reaching parts of Maharashtra and Madhya Pradesh.

The possibility of long-distance transport does not establish that farm fires elsewhere are responsible for a particular Mumbai AQI spike. It does, however, underline why air pollution cannot always be understood by looking only at sources within municipal boundaries.

Garbage Burning Around Mumbai Adds To The Pollution Burden

Pollution generated closer to Mumbai is another concern, particularly the open burning of household and other waste in areas without adequate collection and disposal systems.

Sumaira Abdulali, founder of the Awaaz Foundation, told that garbage was being burnt in rural areas south of Mumbai, including parts of Alibaug and surrounding belts. Where formal waste services are limited, residents may burn rubbish along roadsides or on open plots, releasing smoke and fine particles into the air.

Abdulali said the combined impact of waste burning and agricultural fires could be significant, depending on prevailing winds.

She also highlighted Bhiwandi in Thane district and Alibaug in neighbouring Raigad district as areas of concern. Sensor-based readings she cited recorded PM2.5 concentrations above 1,000 near roadside garbage fires, while readings in parts of Alibaug ranged between 300 and 400. These are reported local readings, not citywide AQI figures, and should not be interpreted as such.

A further problem is the limited availability of official air-quality monitoring stations in many rural areas. Without adequate monitoring, it becomes difficult to establish the scale of pollution from open burning or determine how much of it is carried into Mumbai.

Crop-residue burning in Maharashtra also occurs at different times of the year, particularly between February and May and again between October and November, depending on the crop and region. Experts have suggested that changing weather conditions may make the effects of these existing sources more noticeable.

Firecrackers Could Make The Situation Worse

Festival-season firecrackers add another source of pollution to an already difficult mix. Their emissions can increase particulate matter and release other substances into the atmosphere, while weak winds may slow the dispersal of smoke.

Abdulali told India Today that tests had detected toxic heavy metals in firecrackers, including some sold as green crackers. She cautioned that the label should not be treated as a guarantee of safety, particularly where compliance with regulations is uncertain.

She also warned that the period between celebrations offers little time for the city’s air to recover, with Diwali followed by Christmas and New Year.

Abdulali wrote to Maharashtra Chief Minister Devendra Fadnavis on October 21, raising concerns about firecracker use despite restrictions. Her letter referred to Bombay High Court directions restricting firecrackers in public spaces, including roads and footpaths, during festivals in 2026, and calling on police to measure decibel levels and take appropriate action.

The Bombay High Court has separately criticised the impact of uncontrolled firecracker use on air quality. In an October 15 report, India Today said the court had upheld year-round restrictions and directed the state and civic authorities to strengthen awareness, monitoring and enforcement. The court also called for complaint mechanisms, nodal officers and equipment for field staff to measure pollution levels.

In the latest proceedings cited in the material, the court directed the police, BMC and Maharashtra Pollution Control Board (MPCB) to explain the steps taken to enforce pollution-control and firecracker-related orders, with their measures due to be presented at the October 26 hearing.

The intervention reflects a wider concern: restrictions have limited value if violations are not detected and acted upon.

Why Are Some Mumbai Pollution Sensors Showing Suspiciously Low Readings?

Alongside concerns about the sources of pollution, a separate issue has emerged over the reliability of readings displayed at construction sites.

A Times of India report published on October 24 highlighted sharp differences between sensors located close to one another. On Thursday, city AQI readings ranged from 57 in Malad to 153 in Worli, while a sensor at a construction site in New Cuffe Parade recorded an AQI of just 16.

The same device reported PM2.5 at 5.6 and PM10 at 11.1. Across the road, a ready-mix concrete plant recorded PM2.5 at 49 and PM10 at 60. Another nearby reading showed PM2.5 at 25.1 and PM10 at 6.3.

Avinash Dhakane, additional municipal commissioner, described the AQI of 16 as practically impossible under the prevailing conditions and said the reading could point to a calibration problem, a sensor error or possible manipulation.

The differences were not confined to New Cuffe Parade. At two construction sites in Sewri located metres apart, one sensor recorded PM2.5 and PM10 at 60 and 71, while the other showed readings of 7 for both pollutants.

In Navi Mumbai, a construction site in Kamothe displayed PM2.5 at 13, PM10 at 11 and an AQI of 13 on Wednesday, when the city’s officially reported AQI was 135.

Such differences warrant investigation, but an isolated reading does not by itself prove deliberate tampering. Local wind conditions, nearby emission sources, sensor placement and the equipment’s condition can all affect measurements.

How Sensor Errors Could Affect Pollution Control

Dr Sagar A Marathe, assistant professor at Somaiya Vidyavihar University’s School of Basic and Applied Sciences, told TOI that air pollution can vary over short distances because of weather, wind and nearby emission sources. However, he said substantial discrepancies between nearby sensors need scrutiny.

He identified several possible reasons for unreliable readings, including low-quality equipment, voltage fluctuations, inadequate calibration and incorrect placement or shielding. Differences of a few micrograms per cubic metre may be expected, but much larger variations raise questions about whether the devices are functioning properly.

The BMC’s own guidelines recognise that sensors that are poorly maintained, inadequately calibrated or not checked regularly can under-report pollution. A May 2025 circular requires calibration every two months, comparison with reference-grade monitors and periodic equipment checks.

Dust accumulating on sensor optics and high humidity can affect readings, while fluctuations in power supply may also interfere with their performance. Experts have called for clearer technical specifications and consistent rules governing sensor installation and placement.

Marathe also cautioned against treating an instantaneous reading as a definitive measure of compliance. Particulate pollution is generally assessed over a 24-hour period when compared with national ambient air-quality standards. A brief snapshot may not capture the exposure people experience over an entire day.

BN Kumar, environmentalist and director of NatConnect Foundation, warned that inadequate surveillance could leave room for manipulation of displayed readings. He called for standardised meters and checks by the BMC to establish whether the figures shown at construction sites are accurate.

The distinction matters because monitoring data are used to identify pollution hotspots and assess whether construction sites are following prescribed requirements. If devices produce misleading readings, enforcement decisions may be based on an incomplete picture.

BMC Plans AI Monitoring Across 3,000 Sensors

The BMC is planning to use artificial intelligence-enabled analytics to monitor around 3,000 sensors installed at infrastructure and construction sites. The system is intended to identify pollution hotspots, flag locations where readings breach prescribed limits and help officials coordinate corrective action.

The civic body has empanelled 18 agencies to install sensors and directed officials to remove devices that repeatedly fail to meet calibration or maintenance requirements. Flying squads have been inspecting construction sites since October 1.

The sensor network could help officials identify areas requiring closer attention, but its usefulness will depend on the accuracy of the underlying data. Automated analysis cannot compensate for faulty equipment or inconsistent calibration.

The BMC is also considering practical steps such as washing roads with non-potable water to control dust. Earlier measures included a special road-washing drive from October 1 to 15, street cleaning, covering major construction projects and assigning nodal officers to monitor large works.

Dhakane said the CPCB’s Sameer app was the reliable source for monitoring air quality, noting that other platforms may not use standardised devices comparable to those employed in official monitoring.

The BMC has reported 231 days of good or satisfactory air quality so far this year, compared with 222 days in the previous year and 216 days the year before. That figure offers one measure of the city’s annual air-quality record, but it does not remove the need to investigate individual pollution spikes or questionable readings.

Mumbai And Delhi: Similar Pollution Sources, Different Weather Challenges

Delhi’s winter pollution is associated with a combination of vehicle emissions, construction dust, industrial activity, crop-residue burning in neighbouring states and weather conditions that restrict dispersion. Once winds weaken and the atmosphere becomes less effective at clearing pollutants, emissions can accumulate near the surface.

The timing of agricultural fires also matters. Changes in paddy sowing and harvesting schedules can shift some burning into November, overlapping with the period when winter weather increasingly favours pollution build-up in northern India.

Mumbai’s pollution pattern is different in important ways. The sea and coastal winds can help disperse emissions, but the city remains exposed to its own traffic and construction pollution, open waste burning in surrounding districts, local crop-residue fires and firecracker emissions. The effects of possible transported pollution depend on the winds at the time.

This means Mumbai cannot simply be treated as another version of Delhi. The two cities have different geographical and meteorological conditions, even though both face emissions from human activity and periods when weather allows pollutants to accumulate.

Nor does a single day on which Mumbai records a higher AQI establish that its air is consistently more polluted than Delhi’s. Comparisons must use readings from the same period and a consistent measurement scale.

What Needs To Change To Improve Mumbai’s Air?

Mumbai’s current pollution spell points to the need for action on both emissions and monitoring. Construction dust and vehicle exhaust remain important local sources, while waste burning and agricultural fires in surrounding areas require attention beyond the municipal limits.

Enforcement of firecracker restrictions is another part of the response, particularly during festival periods when additional smoke can enter the atmosphere. Authorities also need to ensure that complaints are investigated and that restrictions are implemented consistently.

At the same time, the reliability of air-quality sensors needs to be established. Regular calibration, comparison with reference-grade equipment, correct placement and transparent checks are essential if sensor readings are to guide enforcement. AI-based monitoring may help officials process thousands of readings, but only if the data are trustworthy.

Mumbai’s experience also highlights why air quality should not be judged by geography alone. The Arabian Sea may provide conditions that help disperse pollution, but it cannot neutralise emissions indefinitely. When winds slow and multiple sources continue releasing pollutants, the city’s natural advantage can weaken.

For residents, the comparison with Delhi is a warning rather than a competition. The central question is not which city records the higher number on a particular day, but whether authorities can reduce emissions, improve monitoring and prevent recurring episodes of polluted air from becoming an accepted part of urban life.

About the Author

Parishmita Saikia

A sociologist by training and a storyteller by profession, I spend my days shaping news, and when I’m not chasing deadlines, I’m exploring new places, discovering different cultures and tasting unique...Read More

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