On certain mornings, the air over many cities acquires a strange density. Buildings dissolve into a pale grey horizon, traffic moves through a faint veil, and people step outside with a hesitation that has little to do with the weather. The cough that follows is almost routine now, a regular reminder that what we breathe has become one of the defining questions of urban life.
But amidst the doom and gloom we hear about our environment, an encouraging development is unfolding in some cities around the world. A number of major cities have managed to cut their air pollution sharply over the past decade — in some cases by nearly half — while continuing to grow economically. Their experience suggests that toxic air is not an inevitable companion of urban expansion or development. It is, rather, the result of choices made over years about how cities move, how they heat themselves, how they regulate industry and how they plan the spaces where millions live.
That conclusion emerges from a recent report by the Breathe Cities initiative, a partnership backed by Bloomberg Philanthropies, the Clean Air Fund, and the global C40 Cities network. Focusing on pollution trends across major metropolitan areas, the report identifies a group of cities that have achieved significant reductions in both fine particulate pollution and nitrogen dioxide over the past ten years. In several cases, the declines are significant enough to register as transformations.
Interestingly, who does not appear on that list is equally revealing. Cities from Europe, North America and East Asia feature prominently among those that have pushed pollution downward. Nine Chinese cities, including Beijing, are on the chart that shows significant reduction in pollution. But none from South Asia do. Lahore which religiously ranks among the most polluted cities in the world during winter — is absent. So is Delhi, its immediate competitor on the list of most polluted cities. In fact, not a single major Indian city appears among those that have recorded sustained reductions in both major pollutants. For a region where polluted air has become a seasonal crisis affecting hundreds of millions, the omission is difficult to ignore.
All that said, this report raises an uncomfortable set of questions: if some cities have shown that rapid improvement is possible, why do others remain trapped in cycles of worsening smog? What distinguishes those that have broken free from those that continue to choke?
The invisible crisis
Air pollution has become the single most potent threat to human health. Unlike floods or earthquakes, it does not arrive as a dramatic event, does not create a path of visible destruction through neighbourhoods. It accumulates gradually, particle by microscopic particle, in the air people breathe every day.
Fine particulate matter, known as PM2.5, is especially dangerous, small enough to penetrate deep into the lungs and from there into the bloodstream. Over time they contribute to heart disease, strokes, lung cancer and chronic respiratory illness. Nitrogen dioxide, another common pollutant produced largely by vehicles and power plants, inflames the respiratory system and worsens asthma.
The health consequences ripple outward across society, with children exposed to polluted air more likely to develop respiratory problems early in life. Pregnant women face higher risks of complications. During severe pollution episodes, hospitals often record sharp spikes in admissions. The damage unfolds slowly, and because it is invisible, polluted air rarely sparks the urgency of disasters we can see, and so becomes something we simply endure. Cities are where this slow crisis is felt most intensely. Dense populations, heavy traffic, industry and construction concentrate emissions within relatively small spaces. What might disperse across open landscapes, experts say, becomes trapped between buildings and along busy roads.
For much of the past half-century, the relationship between economic growth and pollution appeared almost inevitable. Industrialisation produced jobs and rising incomes, but also smokestacks and traffic. That assumption, according to experts, is now being challenged, not by an isolated case, but by multiple cities that have reduced air pollution while continuing to develop.
Cities that reversed the trend
Over the past fifteen years, a group of cities across Europe, North America, and East Asia has achieved something once considered unlikely – a substantial reduction in both particulate pollution and nitrogen dioxide, all while their economies continued to grow. In some places, the improvements have been described as transformational.
Beijing, China’s capital, long synonymous with choking smog, has cut particulate pollution sharply, a change visible to anyone who has visited the city over the past decade. Warsaw has seen similar reductions, its winter air no longer thick with coal smoke. Amsterdam and Rotterdam have significantly lowered nitrogen dioxide levels. Paris has steadily pushed pollution downward while reshaping large parts of its urban landscape.
Each city followed its own path, with some confronting heavy industrial pollution and others struggling primarily with traffic congestion. Their experiences, according to the report, reveals a shared pattern – sustained improvements came from a series of deliberate policy decisions over many years rather than from any single breakthrough. The lesson, experts point out, is not that cleaning urban air is easy, it is that it is very much possible.
Measuring the air
One of the most important steps came long before new bike lanes or electric buses appeared. Cities began to measure pollution far more carefully. For years, many urban areas relied on a small number of monitoring stations scattered across large metropolitan regions. These stations offered broad snapshots of air quality but revealed little about how pollution varied between neighbourhoods.
Studies show that cities that made progress invested heavily in monitoring networks. Dozens of stations, supported by hundreds of sensors and satellite data, began tracking pollution levels across entire urban regions.
Beijing’s monitoring network now allows officials to track pollution in near real time. When levels rise, authorities can identify likely sources such as traffic congestion, industrial emissions or heating systems.
According to experts, this impact extends beyond policymaking. Public access to air-quality data has changed how citizens perceive pollution, with smartphone apps showing daily readings and news bulletins reporting spikes in particulate levels.
Reimagining the street
With absolute certainty, expert studies and opinion, transport remains one of the largest sources of urban pollution. For decades, cities attempted to accommodate rising car ownership by expanding road networks. The result is predictable – more traffic always equals more emissions.
Several cities have reversed this logic by redesigning streets around a different principle — that cars should not dominate urban space. Amsterdam provides one of the best examples. The Dutch capital expanded its already extensive cycling network while limiting car access in parts of the city centre. Bicycles now account for a substantial share of daily journeys in the city.
Taking a cue from the Dutch capital, Paris has recently undergone its own transformation. Over the past decade the city has added hundreds of kilometres of cycling lanes, many built rapidly during the pandemic years when authorities seized the opportunity to reshape traffic patterns.
Sections of roadway once dedicated to cars have been converted into pedestrian promenades and parking spaces have given way to trees and outdoor cafes.
Such changes are not always welcomed at first, as drivers often resist restrictions and businesses worry about losing customers. But over time, experts note, many cities have discovered that reducing car traffic can make neighbourhoods more vibrant rather than less.
Moving millions differently
Cycling and walking can transform short journeys, but large cities still depend on public transport to move millions of people every day. Environmentalists and scientists studying pollution say that investments in modern transport networks have therefore become central to improving urban air quality.
Warsaw expanded its metro system, linking growing suburbs to the city centre. London introduced the Elizabeth Line, a major rail corridor that allows commuters to travel across the city without relying on congested roads.
Chinese cities have built metro systems at remarkable speed and these networks now carry millions of passengers daily, reducing the need for private vehicles. In Shenzhen, every public bus now runs on electricity. Diesel exhaust that once trailed behind buses has largely disappeared from city streets.
According to experts, such projects take years to complete and require enormous financial investment, but their impact can reshape how entire cities move.
Cleaner vehicles
Even as cities encourage alternatives to driving, millions of vehicles remain on urban roads. Cleaning up the vehicle fleet has therefore become another important strategy.Electric vehicles have begun to play a larger role. Cities have expanded charging infrastructure and introduced incentives to accelerate adoption.
Paris now hosts thousands of public charging points. Beijing has developed one of the largest electric-vehicle charging networks anywhere in the world. Taxi fleets and buses have often been among the first to electrify, producing immediate improvements in urban air quality.
Electric vehicles, which are prohibitively expensive in many parts of the world, are not a complete solution, their environmental impact depends partly on how electricity is generated. That said, environmental watchdogs still credit them with eliminating tailpipe emissions that contribute heavily to city pollution.
Drawing boundaries
Another policy that has gained prominence is the low-emission zone.These zones restrict or charge vehicles that fail to meet certain emissions standards. The goal is to discourage older, highly polluting vehicles from entering densely populated areas.
London's Ultra Low Emission Zone has become one of the most prominent examples. Drivers of high-polluting vehicles must pay a daily charge to enter the area. Paris and Brussels have introduced similar restrictions, gradually tightening emissions standards over time.
Such policies can be controversial and almost always irk people. Owners of older vehicles worry about the cost of replacing them. To ease the transition, some cities provide financial support for scrapping older cars. Despite the debates, the zones have proven effective in reducing nitrogen dioxide levels in busy city centres.
The missing cities
South Asia’s absence from the list of cities achieving major pollution reductions is alarming, not just because they are missing, but because they are precisely the places that need it most. Lahore, Delhi and other cities in the region regularly record some of the highest pollution levels in the world. Thick smog blankets large parts of northern India and Pakistan during winter.
The causes are numerous but mostly common offenders – vehicle emissions, coal-fired power plants, construction dust, brick kilns and seasonal crop burning. Weak enforcement of environmental regulations, experts point out, makes matters worse.
Political tensions and fragmented governance complicate efforts to tackle pollution that crosses borders. The experiences of cleaner cities suggest that none of these challenges are insurmountable. Many cities that eventually improved their air quality once faced similarly severe pollution. The difference, most recent studies show, comes down to cities crafting policies not just for paper but for implementation.
Breathing differently
Most studies have concluded that urban air will never be perfectly clean, as cities concentrate people, vehicles, and energy use in ways that inevitably produce emissions. The experiences of cities that have managed to improve their air offer a quiet but powerful message – pollution should never be accepted as something that is impossible to address or reduce – it is certainly not destiny. By most expert accounts, it is the result of decisions about transport, energy, urban planning and regulation, made over years and sometimes decades.
On mornings when the sky above a city is unexpectedly clear, when distant buildings appear sharply on the horizon and the air feels lighter in the lungs, the difference can seem almost miraculous. In reality, experts note, it is the outcome of something far less obvious but far more demanding — sustained political choices about how a city chooses to breathe.
