Rampant pollution in Asia has left more than half the world’s population breathing unsafe air

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Located in the heart of Vietnam’s capital, Hoan Kiem Lake is popular with runners, dog walkers and tourists looking to relax in front of a scenic view. But on a recent morning, there wasn’t much to see: The far side of the lake, just 625 metres away, was shrouded in haze.

For much of this spring, Hanoi has choked on smog, a combination of emissions from vehicles, coal plants and agricultural burning, which is carried out to get rid of crop debris and to control pests and weeds. At times, it has topped Swiss air-quality monitoring service IQAir’s table of the world’s most polluted cities.

It’s an undesirable title, but a surprisingly competitive one. On any given day, IQAir’s map of Asia is a sea of yellow and orange, indicating moderate to unhealthy air quality, with only a few spots of green. On bad days, large swaths of the continent are purple, indicating an air-quality index (AQI) of more than 200, or “very unhealthy.”

Poor air quality causes an estimated one in nine deaths worldwide and can lead to lung cancer, heart disease and other health problems, according to the World Health Organization.

But as anyone who has lived downwind of a Canadian wildfire knows, the effects are not only long term. Even moderately polluted air, with an AQI of 100 to 200, can make your nose sting and your throat and eyes dry and itchy. Breathing is more difficult. Headaches and fatigue are common, and, depending on the cause, the air may smell like ash, fuel or even bleach, so being outside for even short periods is unpleasant.

In IQAir’s most recent world report, measuring concentrations of fine particulate matter, or PM2.5, 12 of the top 25 most polluted countries are in Asia, more than in any other region. These countries account for some 4.3 billion people, more than half of the world’s population. Topping the list are Bangladesh, Pakistan and India, with Indonesia at 14, Vietnam at 22 and China, once seen as a poster child for bad air, coming in at 19.

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Hanoi and Jakarta are vying for the title of the most polluted capital among Southeast Asian countries, said Lauri Myllyvirta, lead analyst at the Centre for Research on Energy and Clean Air, which is headquartered in Finland. “Both of them are now more polluted than Beijing, while South Asia, particularly northern India, Pakistan and Bangladesh, is even worse – they’re in a class of their own.”

Christi Chester Schroeder, air-quality science manager at IQAir, said that because of climate conditions and geography in South Asia, “you get this streak of PM2.5 concentrations that just skyrocket because the pollution has nowhere to go.”

“On top of that are factors such as agricultural practices, industry and population density,” she said. “Unfortunately, it really does look like it will get worse before it gets better.”

While air quality has been steadily worsening globally for decades now, a result of rapid industrialization and climate change, the risks of bad air really came to light around the Beijing Olympics in 2008, when athletes began to express alarm about competing in the Chinese capital’s smog.

In the years that followed, in a rare example of public pressure leading to policy change in China, the government made concerted efforts to tackle poor air quality in major cities, with only four Chinese cities in the Top 100 in IQAir’s most recent report – and Beijing not even breaking 400.

But while some of this improvement is a result of measures such as restricting the number of private cars on roads, promoting electric vehicles and cracking down on coal burning and emissions from construction, China has also been able to relocate heavy industry and power generation – a major source of pollutants – away from big cities, something smaller countries are not able to do.

Even this has taken years to pay off, Mr. Myllyvirta said, with much of the improvement seen only recently as the result of actions taken back in the 2010s.

Vietnam is following a similar playbook, he said, implementing new emissions standards, improving monitoring and attempting to reduce traffic, even as the country’s economy is set to be among the fastest-growing in the world this year.

“The challenge is Vietnam has been seeing very rapid increases in fossil fuel consumption, so they’re in a race against that,” Mr. Myllyvirta said. “It’s exactly the dynamic China was facing for a long time, and only when fossil-fuel consumption fell and they settled into a lower growth rate were they able to lower AQI.”

With reports from Reuters