"According to the data presented in the paper, about three-eighths of the Chinese population breathe air that would be rated “unhealthy” by United States standards. The most dangerous of the pollutants studied were fine airborne particles less than 2.5 microns in diameter, which can find their way deep into human lungs, be absorbed into the bloodstream and cause a host of health problems, including asthma, strokes, lung cancer and heart attacks."