空气污染中的小颗粒危害更大

When we talk about choking air pollution, the first index we think about is PM2.5 levels, which stands for particulate matter of 2.5 microns. However, a recent study led by Chinese scientists found that another size of particles might be more dangerous to our health.

The smaller the particle, the greater danger they pose.

A recent study led by Chinese scientists shows a strong link between fine air pollution particles and a range of serious health problems.

Researchers from Fudan University studied particulate matter in 23 size categories ranging from 0.25 to 10 microns. They found that particulate matter of 0.5 microns or less in diameter pose more serious health dangers than other lager particles, especially when it comes to increasing the risk of cardiovascular diseases.

"The smaller particles can reach the lower respiratory tract, passing through the blood-air barrier in the lungs and entering the blood as toxins, which can cause cardiovascular diseases. Larger particles are not able to pass through the blood-air barrier so easily." Yang Xin from Fudan University said.

The study has also found that the smaller the particle, the higher the concentration in any given volume of air and so a greater number of toxic particles come into contact with tissues inside the human body. Particles of 0.5 microns or less have the greatest possibility of entering a human’s alveolus, and settling there, posing major harm to human health.

“The particular matter emitted from vehicles and coal ash fit into this dangerous category. Even though larger particles can be removed, smaller particles of less than 500 nanometers are quite difficult to eliminate. So coal ash is also a big source of the fine pollution particles in the air.” Yang said.

From the perspective of mass concentration, the percentage of particulate matter of 0.5 microns or less is very low, but from the perspective of the number of particles, they account for a very high proportion, nearly 90 percent of all air pollution particles. PM2.5 is the main category of pollution currently monitored by government departments. The new study has provided a new direction and focus for the prevention and control of atmospheric pollution.