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.