How a construction boom led to toxic air in Mumbai

Masoom Khan, a resident of east Mumbai’s Govandi, has an unusual daily schedule. Early each morning, she walks around 700 metres through the narrow lanes of the rehabilitated slum colony in which she lives, to spend the day at a relative’s house. As night falls, she walks back to her home to sleep – only to repeat the cycle again the next morning.

Khan has been shuffling between the two flats for the last two months. She does this because after she and her husband, an auto-rickshaw driver, moved to their new one-room-kitchen apartment in May, she began experiencing coughing fits. “Look at all these medicines I have to take,” she said. She pointed to a cough syrup, an antibiotic, and several tiny pills wrapped in a newspaper.

Khan was diagnosed with asthma six years ago, but until two months ago, she said, she had managed the condition with the medicines. Now, however, the problem is worse than it has ever been before. “I cough so badly that I can’t sleep the whole night,” the 52-year-old said.

She added, as she coughed into her dupatta, “The doctor said it is pollution that has triggered my asthma.”

Right next to her building, the Slum Rehabilitation Authority is constructing another residential building on an empty plot. When Scroll visited the building in late October, plumes of dust rose as trucks carried debris away from the construction site on a kuccha road, while limestone and clay churned inside cement mixers. Khan shut her ground-floor window but it did not help.

Her relative’s place offers some respite to her lungs. “I feel better here,” she said. “I go back home only at night because there is no space to sleep here.”

India’s financial capital is slowly gaining the image of one of the most polluted cities in the world: in February, based on air quality index, or AQI, Mumbai was ranked the second-most polluted city in the world. Other parts of the Mumbai Metropolitan Region also showed high pollution levels – Navi Mumbai, one of the nine municipal corporations under the metropolitan region, became the second-most polluted city in the country in October.

One of the largest contributors to this air pollution has been resuspended dust, or dust particles from paved and unpaved roads and construction sites that are raised into the air by mechanisms such as wind or traffic. A 2020 study led by Gufran Beig, a meteorologist, showed that while transport emissions are the dominant source of PM 2.5 in Mumbai, “windblown resuspended dust” is the largest contributor of PM 10. (PM 2.5 and PM 10 refer to particulate matter that measures 2.5 and 10 micrometres in diameter or less, respectively.)

While studies specifically tracking the additional levels of construction dust over the years have not been conducted so far, Beig argued that its role in the air pollution of the metropolitan region is clear from the ratio between the city’s PM 2.5 and PM 10 levels. As one paper noted, “Smaller PM2.5/PM10 ratio reveals dominance of coarse particles mainly generated from natural sources including road-dust suspension, natural dust storm, etc.”

Beig explained that normally, “the ratio of PM 2.5 and PM 10 is around 0.5 or 0.6. But in recent years, we see that the ratio is much lower, indicating that the proportion of PM 10 is higher as compared to PM 2.5.”

For the Mumbai region, he added, dust emitted from construction and roads is the only source for coarse PM 10 particles.

Indeed, data from the Central Pollution Control Board, collated by Centre for Research on Energy and Clean Air, shows that since 2018, the ratio between PM 2.5 and PM 10 has ranged between 0.3 to 0.4.

A major cause for this pollution is a construction boom that the city has been witnessing in recent years. This boom has been fueled by a series of financial incentives the government has given developers to encourage them to construct and redevelop slums and housing societies. The government has also amended coastal building regulations to allow development where it was earlier barred.

The result is a cloud of construction dust hanging over the city.

Khan is among the many witnessing its direct impact. Residents of the area explained that construction on the new high-rise apartment building began about six months ago and that dust levels continue to increase. As they do, Khan worries about the expenditure her family has to incur because of her health. “We are spending too much,” she said.

The health risks of such proximity to this dust are grave: short-term exposure to such particulate matter through inhalation can cause asthma attacks, exacerbate other respiratory diseases and lead to early deaths.

This story is part of Common Ground, our in-depth and investigative reporting project. Sign up here to get a fresh story in your inbox every Wednesday.

For years, Mumbai has been believed to have an advantage in terms of its limited exposure to pollution owing to the fact that it is situated on the coast. As a result of its location, it experienced land breezes at night from the land to the sea, which would sweep away pollutants that settled in the air above the land.

Since last year, however, meteorological factors have affected this natural flushing process, Beig explained.

The most significant among these factors was the La Nina phenomenon that the earth witnesses in some years. Among the effects of this climatic phenomenon is the cooling of waters in some oceans, including off India’s western coast. Last year marked the third consecutive year that the phenomenon occurred – the resultant dip in temperatures of Pacific Ocean waters prevented winds from rushing from across the Arabian Sea towards the Pacific Ocean. These winds would have typically pushed pollutants in Mumbai away from the land and the coast – in their absence, the pollutants remained suspended over the city.

This year, the problem was further aggravated by winds in October from cooler areas around Mumbai, such as Lonavala and Khandala, which transported pollutants towards the city. Here, they encountered stable weather conditions that accompany the ending of the monsoon – as a result, the particles were arrested over the city, as Beig explained in a recent Indian Express column.

“These meteorological conditions explain why Mumbai saw the worst of pollution last year and this year,” Beig told Scroll.

But he added that to understand the causes of the broader trend of increasing pollution over the years, the sources of the pollution would have to be closely monitored. “The weather is only an additional factor that manipulates the existing emissions and creates a larger problem,” he said.

Experts agreed that a key cause of this increase was the rise in construction projects in the city. “Now, almost all of the city is undergoing some of the other forms of redevelopment or construction projects,” said Hussain Indorewala, an assistant professor at Kamla Raheja Vidyanidhi Institute for Architecture and Environmental Studies. The Times of India reported that between 2021 and 2023, the number of construction projects underway in the metropolitan region increased by 98%.

Pankaj Kapoor, managing director and founder of Liases Foras, the independent real-estate research company that conducted the research quoted in the news report, agreed that this growth was unprecedented. “The pollution in Mumbai is also a fall out of this massive construction and redevelopment,” he said.

Government incentives to encourage such construction began emerging by the early 1970s. But Shreyank Khemalapure, a co-author of the book (De)coding Mumbai and an assistant professor at CEPT University, noted that in a 2018 revised development plan of Greater Mumbai, the incentives that the government offered increased dramatically.

Many of these changes pertained to increases in the Floor Space Index, or FSI, permitted for building houses. This refers to the ratio of the total plot area to the total built-up area of a project. The municipal corporation imposes this to “limit concentration of people” in a given place, which would also limit the burden on the water supply, roads and other public infrastructure.

Until 1969, the FSI permitted in the island city was two. This meant that if a builder had a plot of 1,000 square metres to build on, the total built-up area allowed would be 2,000 square metres. The developer could, for instance, choose to build a two-storey building of 1,000 square metres each, or a four-storey building with 500 square metres each.

In its early initiatives, the government offered additional FSI as compensation for landowners if they surrendered a part of their land for work that benefited the public, such as building or widening roads. A 1991 development plan for the city expanded the benefits available to builders by offering them extra FSI for certain categories of projects even if they did not give up part of their land to the government. These projects included reconstruction of low-cost schemes of the Maharashtra Housing and Area Development Authority, rehabilitation projects for slum dwellers and construction of information technology parks.

“Gradually, the interests of the government and developers became more and more intertwined,” Indorewala said. “The government needed developers for implementation of its plans, and developers in turn demanded more FSI and other incentives and fewer regulations.”

Then, in 2018, the number and scope of such incentives was increased even further, when the Municipal Corporation of Greater Mumbai issued a Revised Development Plan for Mumbai, to replace the 1991 plan. Indorewala compared the two in his paper to explain the advantages that builders gained from this.

He noted for instance that where earlier, additional FSI was granted in projects involving the redevelopment of low-cost state housing authority projects, the new plan allowed this for all the authority’s projects. Similarly, where earlier FSI could be granted for “starred category residential hotels in the suburbs and extended suburbs”, under the new plan it could be granted for any hotels anywhere in the city.

In other categories, too, the geographical areas where these exemptions could be granted were expanded – for instance, while the earlier plan allowed this increase in FSI for construction of government offices only in the suburbs, the new plan allowed it on government or private land “anywhere in the city”.

Khemalapure noted that the tendency of providing incentives “began with the earlier plan and has continued in the 2018 plan in a more heightened way”.

Much of this 2018 plan is focused on redevelopment. Indorewala argued that though the pretext for this was that land in the city was in short supply, “the real reason is that redevelopment in high land value areas is much more profitable than green field projects” – referring to those that developers construct from scratch – “in low land-value areas away from the city”.

A year after the new plan was implemented, the Brihanmumbai Municipal Corporation also eased the process for payment of premiums. These are payments that developers have to make to the corporation to avail of higher FSI for their projects. Earlier, they were required to make an initial payment of 33%, followed by two annual instalments of 33%. Now, for buildings with heights of less than 70 metres, builders could pay their premium over five years with an instalment of 10% at the start and 22.5% for each of the next four years.

For buildings with heights of over 70 metres, builders could pay 10% of the premium in the first year, followed by 18% over five more years. The earlier deadline required them to complete the payment in two instalments.

Following the relaxation of these rules, Mumbai began seeing higher levels construction and redevelopment than ever before. Liases Foras’ Kapoor said, “Looking at the supply side of construction, the inventory and construction stock of buildings, it’s the highest that Mumbai has ever seen.”

The municipal corporation did not respond to emailed queries from Scroll about the rising pollution in the city. In press notes, it stated that it had set up squads to inspect environmental violations at construction sites across Mumbai, and had issued notices in recent weeks to 916 sites for violating construction norms. Further, the corporation plans to form a squad of 500 marshals responsible for preventing the open burning of garbage in the city. In addition, the state chief minister said that the body would deploy 1,000 tankers to spray water on roads and settle dust.

In 2020, the construction business in Mumbai, as elsewhere, was slowed down by lockdowns imposed across the country in response to the Covid-19 pandemic.

To stimulate the industry, the Brihanmumbai Municipal Corporation announced a 50% discount on premium payments in 2021 for ongoing and new constructions, regardless of their size and type. Developers rushed in to register new construction projects. In 2019-’20, corporation had collected roughly Rs 3,800 crore from developers. In the next year, the premium collected tripled to Rs 12,000 crore. Mumbai-based property broker Mohammad Akram Ahmed noted that the premium discounts had prompted “at least a hundred new construction sites in Andheri West” in the western suburbs.

Kapoor estimated that in the Greater Mumbai region, 80% of these projects are redevelopment projects, rather than new constructions.

About the present area in the city under redevelopment, he said, “My own estimate is that redevelopment projects would contribute an additional 75 lakhs to 1 crore square feet.”

Kapoor explained that the construction boom was also spurred by stricter building compliance measures from the government in recent years. “In 2016, RERA came into being, which catalysed the construction boom in the Mumbai market,” Kapoor said. He was referring to the Real Estate (Regulation and Development) Act, 2016 which aimed to protect home buyers and boost investment in real estate. The act also mandates that developers have to lay out a construction timeline at the outset, and prescribes penalties for those who do not adhere to it.

“Earlier, without any regulations, many developers were not complying with the construction progress,” Kapoor said. “But since implementation of RERA, developers started doing extra efforts to meet their deadlines.”

In a 2019 study that Kapoor carried out, he found that between 2016 and 2018, the average time that developers took to complete construction work up to the first floor of a project had come down significantly following the introduction of RERA. The highest such drop among Tier 1 cities analysed in the study was witnessed in the Mumbai Metropolitan Region – while earlier, the average time was 15 months, this dropped to just five months.

As construction work and pollution increased, in the last week of October, the corporation released a set of guidelines for the mitigation of pollution. Twenty of these 27 guidelines were aimed at controlling pollution from dust – these include a rule that sites of projects that were more than 70 metres tall had to have 35-foot-high metal sheets around them.

When Scroll visited a construction site in Andheri West, cement mixers spewed dust as they drove in. While there was a metal sheet around the perimeter, it was only around 10 feet high. In a flat in an adjacent apartment building, Krishna Kala and her mother-in-law Aisha are both suffering from respiratory ailments. “I had a persistent cough for several weeks,” Kala said. She underwent an X-ray and CT scan, which revealed that her lung tissues were scarred – a doctor diagnosed her with lung fibrosis.

Twenty kilometres away from this construction site, Dr Kaushik Desai, a homoeopathic practitioner in Govandi, said that 40% of local patients visiting his clinic complained of allergic cough, asthma attacks and breathlessness. “This trend has been occurring for three years,” he said. A ready-mix concrete plant operated just a few metres from his clinic – open trucks plied to and from it to collect the ready concrete, billowing clouds of dust.

Desai is convinced that his patients’ symptoms, such as coughs that last for around 20 days, are induced by pollution. He has been recommending that his patients use dehumidifiers and air purifiers for ten hours a day. “There is no other way to bring the cough under control,” he said.

The rush to build in the Mumbai metropolitan region has also spilled onto the coasts, particularly aided by a dilution in 2019 of the Coastal Regulation Zone notification, or CRZ notification, a policy that lays out the rules for the protection of the country’s coasts, by regulating activities such as industrial development, mining, tourism, and construction within a certain distance of the shoreline.

The notification was first issued in 1991, and amendments have been issued roughly every decade. Prior to 2019, an amendment was issued in 2011. In that form, the notification prohibited setting up industries, storing or disposing hazardous substances, reclaiming land, mining and other similar work between 100 and 200 metres from the high-tide line of the sea, or rivers, creeks, and backwaters, across the country. In the 2019 amendment, this distance was lowered to a uniform 50 metres. For all areas where some construction had already occurred along the coast, the new notification allowed FSI “as on the date of this notification,” referring to January 18, 2019, the date the notification was issued, whereas the 2011 notification mandated that developers adhere to the FSI norms of 1991.

This dilution made coastal areas in the country a gold mine for real estate developers. Experts point out that this is exacerbating the pressure on the coastal land.

“There have already been constructions along the coastal regulation zone which would be within 50 metres on the shoreline, and thus considered illegal according to the previous notification,” explained Sarita Fernandes, a Goa-based coastal policy researcher, who has studied Mumbai’s CRZs.

For instance, in 2017, the Mumbai suburban district administration identified 53 unauthorised structures on the coastal regulation zone. “But now, when this policy has been relaxed to accommodate real estate and new construction, it has legitimised what were considered as violations earlier,” Fernandes added.

This has also led to grave concerns for the lives and livelihoods of villages and communities that live in these coastal areas.

Both the 2011 and 2019 notifications identify Greater Mumbai as an “area requiring special consideration”. But the 2011 version gave greater protection to Mumbai’s koliwadas, or settlements of the Koli community of fishers, which are found along Mumbai’s coast. The notification mandated that these be surveyed and mapped and then classified under CRZ III, a category of land where only restricted work can be carried out, such as repairs of dwellings, and construction of schools, hospitals and community toilets.

In a public meeting held in March 2020 to discuss a draft coastal zone management plan, Indorewala noted that under the new notification, Koliwadas had not been classified under CRZ III and thus had lost these special protections they once had. Now, he said, they “can be destroyed and new construction can be started with extra FSI”. This, he explained, could destroy the culture and livelihood of fishing communities. He also noted that the mapping of koliwadas had so far not been carried out. The minutes of the meeting show that this argument was well received, and that “participants supported the same by clapping hands”.

For the last three years, Devendra Tandel, a resident of a fishing village in Cuffe Parade, Mumbai’s southernmost tip, has watched construction work move closer to him. “Dust and dirt has increased,” said Tandel, who is also the president of Akhil Maharashtra Machhimar Kruti Samiti.

Just a kilometre from his home, the controversial 30-kilometre, eight-lane coastal road project connecting Nariman Point to Kandivali is under construction. The road had attracted protests by fisherfolk who argued that it would remove their access to fishers’ traditional fishing areas, while environmentalists have raised concerns over the loss of coastal and marine habitat. The construction of this road is causing marine pollution, killing breeding spots of fishes and affecting the plankton population, Tandel said.

Researchers maintain that moves like this will ensure that developers swarm into coastal areas. “Coastal areas have high real-estate value, this is where most money is to be made,” said Indorewala. “Now that CRZ is effectively gone, there is a lot of rush of developers into these properties.”

Developments in this direction are already visible. This October, the Maharashtra government proposed slum rehabilitation in almost 200 hectares of Mumbai’s CRZ – this land would be made available for developers to build high-rise buildings to rehabilitate slums.

Researchers argue that apart from the fact that people will be displaced, such development can also compromise the city’s safety, since the work usually involves clearing coastal vegetation, which acts as a natural protection against extreme weather events like cyclones. This protection is particularly crucial because Mumbai is one of the world’s most climate-vulnerable cities. “When cyclones hit, you need those mangroves,” Fernandes said. “If there are no beaches and no mangroves, that’s the end for coastal resilience.”

Large public infrastructure like the coastal road also has harmful long-term impacts to air pollution, as Indorewala noted. “Projects like the coastal road incentivise use of private vehicles, whose emissions in turn would add to the air pollution,” he said.

In Aug 2021, the Maharashtra government cleared a coastal zone management plan for Mumbai city and its suburbs, which replaced one that had existed since 2018. The new plan further established changes introduced by the 2019 notification – most significantly, it demarcated on a map of the city the 50-metre zone from the coast where construction is barred, and beyond which it is allowed. In August this year, the Maharashtra government also issued a similar plan for the rest of the Mumbai metropolitan region, which included zones mapped out in the areas of Thane, Raigad, Palghar, Ratnagiri, and Sindhudurg districts.

Khan and her husband too despair of their living conditions, and the effects on their health. “I will die if we continue to live here,” Khan said, adding that she and her husband have been mulling over the idea of relocating. The Lalitkumars have considered the option too, but do not see it is viable. In a city where construction and dust is rampant everywhere, a better place is exceedingly difficult to find. “Relocating is not an option,” Kala said. “Where do we go? It’s the same everywhere.”

This reporting is made possible with support from Report for the World, an initiative of The GroundTruth Project.