Why Mumbai is hitting the headlines for air pollution

This month, Swiss air tracking index IQAir, a real-time air quality monitor that monitors the Central Pollution Control Board (CPCB) data, ranked Mumbai as the most-polluted city in India

This winter, Mumbai has been more in the news for air pollution compared to the usual newsmaker Delhi — even overtaking the capital city in a recent survey that ranked India’s financial capital as the second most polluted city globally for a week between January 29 and February 8, 2023.

Is Mumbai’s air pollution problem a one-off phenomenon or is the city gradually going the Delhi way? Experts say meteorological reasons could be behind the recent surge, but man-made factors cannot be underplayed or ignored.

Mumbai versus Delhi

One of India’s largest urban conglomerations, air pollution is not new to Mumbai and its busy surrounding areas. Much like Delhi and the national capital region, the greater Mumbai area houses polluting coal-based industrial belts, is home to mega infrastructure and housing related construction projects that generate dust, has a sizeable vehicular population which triggers automobile pollution, and has a huge slum and rural population, where bio-fuel and wood are extensively used.

But unlike a land-locked Delhi, where the pollutants get trapped in winter because of calm winds and cold weather conditions, Mumbai has the advantage of being located beside the sea with strong surface winds, which helps in the quick dispersal of bad air.

So, what really is happening this time, and over the past few years, that Mumbai is grappling with an increasing number of bad air days?

The increasing air pollution levels in Mumbai are an indicator of a high emission load from industrial hotspots and the worsening transport situation in and around the mega city, says Sunil Dahiya, an analyst at the Centre for Research on Energy and Clean Air (CREA).

“Being a coastal city with a higher dilution of pollutants, Mumbai manages to wash away its emission load. But the increasing air pollution is a testament to the polluting nature of the industries, the transport sector and waste management in the city, which need immediate attention," Dahiya says.

Weather factor

This month, Swiss air tracking index IQAir, a real-time air quality monitor that monitors the Central Pollution Control Board (CPCB) data, ranked Mumbai as the most-polluted city in India and second most polluted city globally during the week between January 29 and February 8, 2023. Delhi was not among the top 10 that week.

Apart from the local triggers, Gufran Beig, founder project director, SAFAR (System of Air Quality and Weather Forecasting and Research), also points to the changing meteorological factors that are at play. SAFAR is an air quality information service under the Union Ministry of Earth Sciences.

“The unusual climate change-induced wind pattern has made Mumbai’s air quality worse in the past eight years. Although the present (IQAir) ranking is based on a few days of comparison, the larger issue is that we should speed up our implementing efforts in true spirit,” Beig, who is also chair professor, National Institute of Advanced Studies, Bangalore, said.

Mumbai had ranked 10th in the (IQAir) rankings on January 29 and climbed to the second spot on February 2 before falling again. It again climbed to the second spot on February 8.

In fact, according to Beig, out of 92 days analysed by SAFAR till February 8 this year, Mumbai had 66 ‘poor’ and ‘very poor’ air quality days in the winter of 2022-23 as compared to an average of 28 in the past three years. Beig said the reason for the prolonged pollution spell is part of a larger meteorological phenomenon that should be deeply analysed.

The pollution triggers

Other experts say while weather conditions are not in our hands, the authorities can certainly go all out to mitigate the local factors at play.

“Mumbai’s problem is a combination of growing local pollution, meteorological factors and a change in the regional weather system. While we cannot control the natural forces, we can certainly adopt an ambitious plan for aggressive mitigation of local pollution sources,” says Anumita Roychowdhury, executive director of non-profit Centre for Science and Environment (CSE).

According to a 2020 study by CSE, which assessed four major industrial clusters surrounding Mumbai — the Trans-Thane Creek, Taloja, Ambernath and Dombivali —the massive use of coal in the Mumbai Metropolitan Region is one of the key factors for the deteriorating air quality.

Every year, two million tonnes of coal is burnt here, CSE says, calling for a clean fuel policy, strengthening of air quality monitoring and deterrence, and pushing unclean industries out of city limits, etc., to avoid a situation like Delhi.

According to another CSE analysis based on real-time data from the working monitoring stations, the number of bad-air days in Mumbai doubled between 2019 and 2021, while good days were down by 20 percent.

South Mumbai had the worst air in December 2021 with Mazgaon, which hosts the docks, topping the list. Khindipada at the edge of Sanjay Gandhi National Park in the north was the least polluted in that period, the study showed.

“This underscores the urgency of scaling up action across all sectors to prevent further worsening and to arrest the trend in this region,” the report states.

CPCB data also showed that the number of ‘poor’ and ‘very poor’ days in Mumbai in November-January this winter was more than double compared to three previous winters.

Dust pollution

Dust pollution triggered by a slew of infrastructure and housing projects, which have resumed in full vigour after the Covid lockdowns, is another contributor to Mumbai’s deteriorating air quality.

Construction dust seems to be one of the key reasons behind the surge in pollution this time, says Mumbai-based environmentalist Sumaira Abdulali. “Big infrastructure projects such as flyovers and private constructions are going on in full swing, where hardly any dust mitigation norms are followed.”

Abdulali said detailed pollution mitigation plans are available and the authorities just need to implement them in earnest, adding simple measures such as sprinkling of water and dust screens are not followed. “Industrial pollution has always been there but it seems dust is playing a major role this time. As far as the weather factor is concerned, one can’t just blame it and do nothing,” said Abdulali, founder of the NGO Awaaz Foundation.

In its budget for the year 2023-24, the Brihanmumbai Municipal Corporation (BMC) — which identified road and construction dust, traffic congestion, industries, the power sector and waste burning as major contributors — announced a seven-step action plan to battle air pollution as part of a Clean Air Mumbai initiative.

The measures include air purifiers at five crowded locations, implementation of measures to check dust pollution at construction sites and roadsides, sustainable and clean transport modes, waste control steps, urban greening, effective monitoring of air quality, and awareness campaigns etc. The BMC announced five more air quality monitoring stations. Mumbai has 20 active stations at present, which are not enough given the vastness of the city.

No relief yet

Prarthana Borah, director of CDP India, a not-for-profit that recommends how organisations can lessen their environmental impact, warned exposure to high levels of air pollution would lead to a variety of adverse health issues such as an increased risk of respiratory infections, heart diseases and even lung cancer.

“Acknowledging the fact that air pollution affects several aspects of society and that addressing the problem benefits human health, the economy, ecosystems, and climate is the first step to tackle the issue,” Borah said.

Dahiya also suggests the government should include sectoral emission load reduction targets to move towards better air quality levels.

Though the situation is easing as of now with an increase in temperature, dust storms originating from the Thar Desert, border areas of Afghanistan and Gulf could start to haunt Mumbai and keep the AQI in poor shape, Beig warned. Mumbai’s air quality index (AQI) on February 16 was 199, which is considered moderate. Delhi, on the other hand, was 270 at poor.

An AQI between zero and 50 is ‘good’, 51 and 100 ‘satisfactory’, 101 and 200 ‘moderate’, 201 and 300 ‘poor’, 301 and 400 ‘very poor’, and 401 and 500 ‘severe’.