When the level of airborne particles with a diameter of 2.5 microns or less, known as PM2.5, has reached more than 400 on average, and in some cases as high as 900, in as many as 33 cities in eastern and central China, and caused serious air pollution for days, there is no reason to underestimate the harm it does to people's health. Neither is there any reason for us to not reflect on what we've contributed to the smoggy days.

Despite the meteorological reasons, such as the lack of wind and a cold current, the sulphur dioxide, carbon dioxide, nitrogen dioxide and carbon monoxide we have discharged into the air have contributed greatly to the air pollution, according to experts.

That such harmful substances stay floating in the dirty air within the fifth and sixth ring roads in Beijing when there is no wind for just a day or two points to the fact that the high rises are too densely built and block the dirty air from dispersing.

The rapid increase in car ownership and the increasingly serious traffic congestion have increased the exhaust fumes in cities. The number of motor vehicles in Beijing already exceeds 5 million and will increase further.

There are not enough green areas and trees within the city proper to help soak up the fumes discharged by vehicles and industries.

Almost all cities have these problems.

In the middle of a rapid urbanization process, it is urgent for China to think about how such a process can press forward without compromising the quality of urban life with an increasingly worse living environment.

The air quality in big cities could have been better had more attention been paid to the density of the high rises, had more trees been planted in proportion to the number of residential areas, and had the number of cars been strictly controlled. These are the lessons China should learn for its further urbanization.

For those cities suffering seriously polluted air, every resident needs to have a sense of environmental awareness, since everyone is a victim. They need to reduce their use of motor vehicles. The government also needs to have measures to reduce the use of government vehicles and the pollutants emitted by industries. Other measures are also needed to reduce traffic congestion, which will greatly reduce the exhaust fumes discharged by cars.