Air pollution is deadly – in fact a recent study found that, on average, it cuts human lifespans by three years, which is higher than the global effect on lifespan caused by smoking. Yet the coronavirus pandemic and subsequent lockdowns enforced by governments across the world has led to cleaner air in many places. We've looked at the 15 most and 15 least polluted countries in the world according to the 2019 World Air Quality Report produced by air pollution tracking organization IQAir. We've quoted the figures they collated on the concentration of harmful PM2.5 particles in micrograms per cubic meter (µg/m³), with a higher number denoting a higher level of pollution. But we've also examined how the current global situation may have reduced these figures, using both current IQAir pollution data and reports. Click or scroll through to find out more on the countries with the dirtiest and cleanest air then and now.

Vietnam had the 15th highest levels of PM2.5 particle pollution in the world in 2019, and that doesn't look set to change after the pandemic if plans to construct a further 26 coal power plants go ahead. The main causes of air pollution are: heavy use of motor vehicles in major cities, worsened by a lack of public transport; burning of waste; and dependence on fossil fuels for increasing energy demand. Over the past decade, coal consumption has tripled while oil consumption rose 70% in the country, according to a briefing in October 2019 by business consultancy Dezan Shira & Associates. Social distancing was only enforced for a relatively brief period so far this year due to a low number of coronavirus infections and pollution has returned to high levels according to IQAir's monitoring.

In January 2020, the thick smog and pollution enveloping Bosnia and Herzegovina’s capital Sarajevo was so bad it prompted the Swedish embassy to brand it “in a category of its own”. Large coal power stations emit sulfur dioxide and other pollutants into the atmosphere, with 44,000 years of life expectancy lost each year due to particulate matter or nitrogen dioxide in the country, according to the UN. The government has banned diesel vehicles from Sarajevo city center and recommended that residents use protective masks. However, while lockdown has brought some relief from vehicle emissions, satellite images from the European Space Agency show the polluting power plants are still affecting the air quality.

Air pollution in Kuwait is caused by a range of factors including vehicles, construction projects, smoke from chimneys and dust and sand storms. Kuwait City’s air had been classified as “unhealthy” by the Air Quality Index. Yet with vehicle traffic greatly reduced and construction having ground to a halt now, leading to huge numbers of migrant workers losing their jobs, the air quality has dramatically increased according to IQAir's latest data. What happens next will likely depend on what path the government pursues for recovery.

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Heavy dust storms often swirl across the United Arab Emirates in the summer, with serious consequences for the air its citizens breathe. A respiratory expert told local newspaper The National the storms carry silica crystals, dust mites and infections. However, the government has condemned international organizations for grouping natural phenomena such as dust storms together with man-made causes when calculating pollution levels. And indeed lockdown has led to a 50% drop in nitrogen dioxide levels recorded in Abu Dhabi, according to the emirate's environment agency. 

The toxic smog that often envelops China’s cities is well-known, though it is far from the most polluted country, coming in at 11th in the 2019 IQAir rankings. Its densely-populated cities might explain why its air seems so deadly – with China recording the highest mortality rates from pollution according to the latest World Health Organization (WHO) data. However, the coronavirus outbreak is affecting pollution levels, with NASA images showing a clear reduction in nitrogen dioxide levels across the country, which it says is "at least partly" associated with the economic slowdown caused by the disease. Yet four Chinese cities are still in the current top 10 major cities with the worst pollution levels recorded by IQAir as the country begins to return to something approaching "business as usual".

War-related air pollution in Iraq has been found to be a factor in the numbers of birth defects and cancers being reported, according to a 2016 study published in the journal Environmental Monitoring and Assessment. Little research has been done to establish the impact of pollution on the general population, although an air sampling study by the US Department of Defense at Balad base in 2008 found high levels of particulate matter, with burn pits used in the warzone contributing to pollution. It's likely though that lockdowns in major cities have improved the air quality for now.

Uzbekistan was the ninth most polluted country in 2019 with average PM2.5 levels at 41.2 µg/m3. The Central Asian country is heavily reliant on fossil fuels, although that’s changing fast. At the end of last year, Uzbekistan had just 4MW of installed solar capacity but that figure is expected to rise to 40MW by the end of 2020, and there’s a plan in place to reach 4GW of solar PV capacity by 2031. This is thanks to a recent partnership between green energy company Helios Energy and Uzbekistan’s Ministry of Innovative Development. However, for now the air quality will still be affected, although a strict lockdown will have significantly reduced vehicle emissions. 

Poorer parts of southern and eastern Asia have some of the highest urban pollution, with annual levels averaging over five times the recommended limits. In Nepal, it has contributed to rising rates of lung and skin disease, according to the BBC. Even major landmarks such as Buddha’s birthplace of Lumbini have been affected by industrial activity nearby. Tourists have reported breathing issues and monks occasionally have to wear masks. A country-wide lockdown has unlocked the beauty of areas such as the Kathmandu Valley though, according to satellite images, if only temporarily.

The presence of nearby deserts causes severe dust storms in parts of the Middle East, including Bahrain. They mark a stark contrast to the smog that engulfs cities in other polluted parts of the world but the dirt and other materials caught up in the storms can still keep people inside and even prove fatal. However, without such storms and with less vehicle pollution, Twitter users have claimed to be able to see the rare sight of the skyline of Bahrain from neighboring Saudi Arabia. 

The sixth most polluted country in the 2019 rankings, the Air Quality Life Index released a specific report on the impacts of air pollution in Indonesia, which states that the average Indonesian loses 1.2 years of life expectancy due to pollution. In the worst affected regions, that figure is as high as four years. Last September, pollution caused by smoke from forest fires caused schools in two cities in Borneo to close for a week, as the air quality had reached “dangerous” levels according to government officials. However, photos vividly show the effect a reduction in people's movements at the moment have had on the air quality in the capital Jakarta.

The air in India’s traffic-clogged capital New Delhi was so bad in December that breathing it in was equivalent to smoking 50 cigarettes a day, according to USA Today. Pollution tends to get worse at that time of year, when the air over the city becomes cool, dry and still, meaning pollution is more easily locked in. At the same time, some residents turn to open fires for cooking and heating, which makes matters worse as it releases ash and dust. Yet a strict lockdown has had a remarkable effect on India's air quality, with IQAir data showing µg/m3 levels in New Delhi in March 2020 fell by 60% compared to the same period the year before, and by 34% in Mumbai over the same period. Activists are hoping these stark figures lead to permanent change.

In Afghanistan, people are more likely to die from air pollution than due to civil war. There were 26,000 deaths caused by air pollution-related diseases in 2017 compared to 3,483 deaths caused by war, according to a report by the Afghanistan Research Center. The mountains that surround the capital Kabul trap polluted air and dust over the city. The poor quality of fuel used by many homes and businesses worsens the problem, and citizens sometimes wear face masks when outside. Lockdown has improved air quality, according to IQAir data, but the respite may only be temporary. And sadly the respiratory problems people face are likely to make them more suspectible to coronavirus.

Few places have more polluted air in the winter than the Mongolian city of Ulaanbaatar, where 46% of the population lives and pollution can reach more than 133 times above the limits recommended by the WHO. Faced with a public health crisis, in May 2019 the government banned coal burning in the capital to reduce pollution levels. As an alternative heat source, the government is encouraging people to use an alternative product made of semicoke, a byproduct of coal, which burns for twice as long and gives off fewer fumes. As in Afghanistan, the pollution is likely to make more people susceptible to coronavirus due to respiratory conditions.

Pakistan was the second most polluted country in the world in 2019 according to IQAir. And 22% of deaths a year are caused by pollution, according to a 2015 study in the medical journal Lancet. In May 2018, the court-appointed Smog Commission implemented the Punjab Clean Air Action Plan, which recommended actions such as emission-reducing technologies and the establishment of Smog Response Desks. Yet Amnesty International claims it’s not enough. “The government of Pakistan needs to do much more to adequately address such a severe public health crisis,” said Rimmel Mohydin, a campaigner. As in India, lockdown has improved air quality significantly but the city of Karachi is still one of the 10 most polluted cities at the moment according to IQAir.

Bangladesh had the highest levels of PM2.5 pollution in the world in 2019, at an average rate of 83.3 µg/m³. The situation is worst in capital Dhaka, and despite lockdown it remains among the five most polluted major cities in the world. Pollution figures recorded in other cities by IQAir don't show significant improvement either. The government has tried introducing measures such as fining polluters and encouraging use of lower-emission brick kilns, yet campaigners say it’s not enough. “The authorities have no interest in combating air pollution. They are doing nothing effective,” Abdul Matin, general secretary of Bangladesh Poribesh Andolon, told the Dhaka Tribune.

Turning now to the countries with the lowest pollution levels on the 2019 IQAir list, in 15th place was Denmark. The country’s four largest cities – Copenhagen, Aalborg, Aarhus and Odense – have low emission zones, which means that there are strict regulations around heavy goods vehicles in city centers. In Copenhagen, the City Council reported in July 2019 that 62% of residents were commuting to work or school by bike, thanks in part to the council’s 14-year plan to make cycling safer and easier for residents. Figures in March 2020 from the Danish Centre for Environment and Energy showed air pollution in the biggest cities had fallen by a third during lockdown.

Malta is one of just a handful of nations not to breach European Union rules on air pollution in recent years. It has curbed emissions from cars and power plants, though it still has its problems, according to Malta Today. A 2018 study by environmental NGO BirdLife reported alarmingly high emissions near the Valletta Port, where cruise ships regularly dock. However, its policies are clearly working as French energy consultancy Sia Partners said it was one of the countries with the lowest drops in emissions during the early stages of coronavirus lockdowns across Europe.

The coastal city of Porto can boast Portugal’s freshest breeze, with the government ranking its air “good” or “very good” more than 95% of the time. The Portuguese authorities started taking their environmental responsibilities very seriously in the early 1990s, according to the OECD. The average citizen’s exposure to fine pollutants in the air dropped by 18% between 2005 and 2013 alone. Further drops during lockdown have led to 609 pollution-related deaths being avoided in Portugal this year, according to the Centre for Research on Energy and Clean Air.

The USA’s Clean Air Act of 1970 began five decades of progress in air quality, according to USA Today. Many harmful emissions from vehicles and factories have plummeted since, with new cars now 99% cleaner in terms of common pollutants. Despite president Donald Trump’s attempts to revitalize coal plants by rolling back environmental protections, in 2019 they shut down at the second fastest rate on record, according to data from the government and Thomson Reuters. Lockdowns in many states have seen air pollution levels drop dramatically, particularly noticeably in LA, but pollution is still higher in industrial centers.

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In Quito, Ecuador's capital, the government has put into place a Transit Oriented Development (TOD) strategy which aims to maximize the amount of public space in walking distance of public transport, prioritizzing environmental and social sustainability and shifting away from private vehicles. The country's lockdown during the pandemic has further improved air quality.

Strong environmental regulations have helped maintain enviably clean air across urban Australia, although recent bushfires have caused a rapid spike in PM2.5 air pollution. In Sydney, Australia’s largest city by population, the air quality exceeded “hazardous” levels at several points during the fires, leading to a 10% rise in hospital admissions. In order to address the issue, in January health authorities recommended people avoid exercising outdoors, as people breathe in more when they exercise. Early research shows a small increase in air quality during the country's lockdown.

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Many of Canada’s cities rank among the cleanest in the world for their air quality, including major centers such as Ottawa (pictured), Toronto and Vancouver. In Ottawa, the vast greenbelt around the city, relatively small population for a capital and successful bike-share schemes show how pollution can be curbed. Canada even has a Clean Air Day to encourage the public to reduce pollution even further.

Strong winds sweeping in from the sea, relatively low urban populations and a lack of heavy industry ensure high air quality in New Zealand. Efforts to increase energy efficiency and improve waste systems in cities including capital Wellington have also made a difference. According to the New Zealand government, the key contributors to air pollution are burning wood and coal, with home heating causing a third of PM 2.5 particles. Officials suggest changing technologies, such as improved wood burners, combined with behavioral change, will be key to reducing pollution even further. IQAir data suggests the country's lockdown has led to a further small improvement in air quality.

Norway’s capital city is a world leader with its sustainable public transport system, which runs entirely on renewable energy, and aims to be emission-free by 2028. Thanks to its commitments to conserving natural areas and reducing pollution, Oslo was named the European Green Capital 2019 – but it’s not stopping there, as the city plans to reduce its overall emissions by 95% by 2030 (compared to 2009). Research by the Centre for Research on Energy and Clean Air found that Norway had seen decreases in both nitrogen dioxide and particulate matter pollution during lockdown.

Stockholm has been crowned the cleanest capital on the planet, and was named as the first European Green Capital in 2010. It has already curbed CO₂ emissions by a quarter since the 1990s and the Swedish city’s authorities hope to make it fossil-fuel free by 2040. The popularity of cycling rather than car ownership, sustained efforts to cut waste and cleaner public transport have helped Stockholm and other Swedish cities limit air pollution. Despite the Swedish government's decision not to impose a coronavirus lockdown, the Centre for Research on Energy and Clean Air reported a decrease in particulate matter pollution as people choose to stay at home during the outbreak.

The medieval heart of Tallinn, Estonia’s capital, probably has its narrow, cobbled streets to thank for keeping traffic levels low rather than any environmental initiative. Wind from the Gulf of Finland also stops the build-up of polluted air in the coastal city, according to the local government. Yet officials can take some credit for the city’s extensive green spaces, free public transport and a reduction in the burning of domestic waste. During the current pandemic, researchers have reported being able to see across the Gulf of Finland from Finland to Estonia, in part due to decreased pollution levels from both shipping and vehicles on dry land.

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Finnish authorities have invested heavily in public transport, aiming to make it so efficient and comfortable that citizens see no need to have their own vehicles – Helsinki is aiming to be car-free by 2025. According to Pia Anttila of the Finnish Meteorological Institute, speaking to Finnish newspaper Yle, pollution is also low because “for a long time we’ve been implementing environmental protections in industrial sectors”, plus Finland is located far away from large industrial areas. Finland has imposed a coronavirus lockdown, which will start easing from 1 June, which has seen huge decreases in vehicle traffic on land and sea.

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Iceland ranked third best in the world for air pollution levels in 2019, largely because it’s blessed with cheap and eco-friendly geothermal energy that powers much of the small nation’s heating and electricity. Contrary to the island’s clean image, not everything is rosy when it comes to the environment, however. The European Environment Agency has warned that pollution levels soar during the rush hour in winter, due to the use of sand and studded tires on icy roads. Lockdown is likely to have improved its already clean air further though.

As it’s a US territory, the Virgin Islands – a tiny archipelago with a population of just over 100,000 – is part of the US Clean Air Act, which has helped to drastically improve air quality since its implementation in 1970. Despite already having very clean air, the Environmental Protection Agency (EPA) has recently awarded the territory just over $400,000 (£312k) to help the islands improve air quality even further, as they are sometimes affected by hurricanes which can release pollution into the atmosphere.

Taking the top spot on IQAir's 2019 list was the Bahamas. The islands are known for their beautiful, tranquil beaches and crystal-clear surrounding waters, but the cherry on top is that the air’s exceptionally clean too. However, when Hurricane Dorian devastated the island last September, many buildings were turned to rubble and pollutants were swept up into the air, which may have impacted the island’s air quality since. But the islands have also had lockdowns during the coronavirus pandemic, including a complete ban on tourist arrivals, which is likely to have helped.

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