A red alert has been issued for several cities in northern China including Changchun and Harbin. A red alert is the highest level on the four-tiered alert system and is defined as serious air pollution for three consecutive days. According to Xinhuanet News, “the density of PM 2.5 — airborne particles measuring less than 2.5 microns in diameter, exceeded 500 micrograms per cubic meter on Monday morning.” Visibility is presently less than 50 meters in the downtown capital city of Harbin of Heilongjiang Province.