PM 2.5 bad, PM 0.5 worse

Professors from Fudan University have found that PM 0.5 (particles smaller than 0.5 microns), which takes 90 percent of air concentration, are more harmful to human health than PM 2.5.

Particles larger than 0.5 microns stay in the respiratory tract, but the smaller ones can be inhaled into the lungs and lead to cardiovascular disease. PM 0.5 mainly comes from automobile exhaust, experts said.