China's national weather bureau gave the air quality a rare 5 rating - "heavily polluted" - and visibility was so bad that several flights had to be delayed at Beijing Capital International Airport.
Researchers focused on particles with a diameter of 2.5 millionths of a meter, referred to as PM2.5. These particles come from a variety of sources, including power plants, factories, trucks and automobiles and the burning of wood.
PM2.5 means that a particulate matter’s diameter less than or equal to 2.5 micron, it can go into our lung and be harmful for our health. We can’t see this matter without any equipment; it exits in the air in our life. It can travel deeply into the lungs and have been associated in other studies with increased numbers of hospital visits for cardiovascular diseases such as heart attacks.
Although it is a very small matter, includes a large number of harmful matters, it can exist in the air lay for a long time. Because PM2.5 is a very small matter, it is not very easy to proven it go into our lung, cause many diseases such as asthma, bronchitis, angiopathy and so on.
Recently, as the more and more attention to the environment quality and air quality, the indoor air quality and automotive air quality has become a frequently topic which people concerned.
In order to protect environment and the health of human, from February 2012, the government has announced the new standard of air quality, to push the inspection way of PM2.5. The government also set up the laws about how to inspect the PM2.5.
