A young Beijing writer recently had the good fortune to be sent on assignment to Mexico City, in order to write a travel article about the metropolis. On his return he said he was surprised to find the traffic wasn’t as bad as he had been told, no-one in his party had been mugged, and the pollution wasn’t half as serious as he had expected.

He added the air quality of Mexico City compared favorably with Beijing, which has recently been bathing in a wintry, grayish soup. His observation was correct. Though Mexico City did have a reputation for poor quality air in the 1990s it has cleaned up its act.

Beijing too is learning to manage the problem. There may be poisonous brown clouds circulating around Asia, the New York Times reported in October, but the capital of China really is experiencing more “blue-sky days.”

Blue-sky days are when the pollution index (from 0-500) is below 101 and there were a record number of these this year, compared with annual figures that have been compiled and published since 1998. Up until September there were just 2 days with “dangerously high pollution,” which is almost nine times better than for the same period in 2000.

It has been pointed out the measurements are imprecise or even misleading, partly because they do not take note of airborne particulate matter, which is most damaging to lungs. Also, the United States Embassy monitors the air and calls the atmosphere “unhealthy” most of the time. But no-one is casting serious doubt on the fact the city has freshened up its air quality.

China has done so by following the example of huge urban areas like Mexico City, where the WHO ozone limit was exceeded on 340 days in 1994. Now it exceeds this limit 30 to 50 percent of the time. Though smog often hangs over the city and thermal inversions forces the smog near the ground in the winter, industrial technology improvements, vehicle emission inspections and the reformulation of fuels has improved air quality.

For the Olympics, a watershed moment, Beijing city planners moved polluting factories out of the main metropolitan area, introduced strict vehicle emission standards and funded a switch from oil to gas heating in homes. It also enacted a rotation system based on license registration for the use of cars, which was maintained after the Games.

Unlike Taipei, where motorcycle exhaust clogs the atmosphere, most of the bikes are powered by people pedaling or electric, which is another big improvement.

You really can see and feel the difference. Four years ago there were often noxious brown clouds that obscured the near horizon. These are rare now. While it is probably still inadvisable to jog in the early evening, when the air is worst, it is no longer suicidal.

While Mexico City has about 21 million people and 6 million cars, Beijing has a shifting population of roughly 17 million (because of migrants) and 4 million cars. City government officials said last month that there was still room for car-ownership growth because 100,000 heavily-polluting vehicles had been removed from the roads. Their emissions were equivalent to 2 million conventional cars.

While there are no immediate plans to put a break on car ownership, stimulated by tax discounts and cheap license fees, hiking parking fees and introducing high-emission taxes are being considered.

The idea is a balance needs to be struck between powering the economy and letting people breathe more easily. The example of Mexico and other major cities shows this is achievable.