Hu Liˈs heart sank due to the color of the air. Driving 140 kilometers from Tianjin City to Beijing last week，she held her breath as the air became a charcoal grey haze(炭灰色的阴霾)．The 39­year­old businesswoman has lived in Beijing for a decade，and this past month，she said，brought the worst air pollution she has ever seen. It gave her husband a cough and left her seven­year­old daughter housebound(足不出户)．“My husband as well as I is working here，so we have no choice，” she said.“But if we had a choice，weˈd like to escape from Beijing.”

The extended heavy pollution over the last month，which caused punishment in return for a day last week－called the “airpocalypse” by internet users－has largel y changed the way that Chinese think about the countryˈs air. On one day，pollution levels were 30 times higher than levels considered safe by the World Health Organization (WHO)．Flights were cancelled. Roads were closed. One hospital in east Beijing reported they had treated more than 900 children for breathing issues. Bloomberg found that for most of January，Beijingˈs air was worse than that of an airport smoking area.

The smogˈs(烟雾) most threatening aspect is its high concentration(浓度) of PM 2.5－particulate matter that is small enough to breathe deep into the lungs and enter the bloodstream，causing breathing infections，lung cancer and possibly damaging childrenˈs development. The WHO has estimated that outdoor air pollution accounts for two million deaths per year，65% of them in Asia.