It’s clear that many of the world’s biggest cities face major challenges when it comes to air quality. What’s not clear is the best way to tackle the problem. Blueair investigates.

It’s a video clip you can’t ­easily ­forget – a fixed camera showing how the air above a highway in Beijing turns from blue to brown over the course of a few hours. In recent years this kind of nightmarish imagery of Beijing’s polluted air has become a recurring reminder of the air quality crisis in many of the world’s metropolises.

In China, there has long been talk of an “airpocalypse”. According to a ­report last year from the ­Berkeley Center, 1.6 million Chinese people die each year from diseases directly linked to pollution, such as asthma, strokes, lung cancer and heart attacks. These account for more than 4,000 deaths a day. Health experts have compared breathing the air in Beijing with smoking two packs of cigarettes a day. ­According to Greenpeace, more than 90 percent of major cities in China have air that is hazardous to health.

However, the situation in Beijing and other Chinese cities is not unique. In the ­majority of cities around the world, the air is so polluted that it causes deaths as well as provoking health risks among their inhabitants. Although many of these cities have started to ­address these problems, the situation is not quickly solvable.

In the United States, Los Angeles has long been the city with the worst air. As early as the 1940s, Los Angeles had such serious problems with smog and pollution that city residents were at one time convinced that they had been the victims of chemical warfare from Japan. But Los Angeles’s attempts to address the problems in the past half-century are also encouraging.

In a speech a few years ago, ­the then President Obama said, “You wouldn’t want your children growing up in Beijing right now, because they couldn’t breathe. But the truth is that that also used to be the case in Los Angeles, as late as 1970.”

Even today, Los Angeles still has a huge problem. In the metropolitan area around the city, three million people live with asthma, diabetes and heart disease caused by smog and polluted air. The occurrence of asthma is twice as high as the national average. In California more people die from polluted air than from traffic accidents or crime. Since the 1970s, things have been slowly moving in the right direction. Local authorities and companies have jointly sought to improve the air in Los Angeles. A series of environmental regulations introduced in the 1970s are still in force today and have contributed to factories and cars in Los Angeles no longer poisoning the air to the same degree. Investments in public transportation and a sharp increase in electric and hybrid cars have also helped improve air quality.

According to Mayor Eric Garcetti, three factors have been particularly important. First, you need to invest in measuring pollution so residents can get an idea of the severity of the problem. Only then is there a collective willpower to do something about the problems. Second, local authorities and companies must work together to agree on regulations that limit emissions and pollution, without preventing businesses and the local economy from growing.

Finally, you have to rely on private sector innovation, and California has always been a shining example – from the electric car company Tesla in Northern California, to the abundance of green tech companies around Silicon Beach in Los Angeles.

But a more sustainable and long-term strategy is needed for the ­future. When Mayor Garcetti visited Beijing recently, he gave helpful advice on the path forward:

“When you combine regulation with innovation, you get sustainable growth. Through investments in green energy not only can we start solving our pollution problems, but we can also create a new industry for climate-friendly companies that attract thousands of new jobs to the city. After all, air is the most democratic thing we have. So we all have a common responsibility to solve the urgent problems of air pollution in the world’s major cities.”