Beijing Cough Page: updated

Following added to the page:
What is in the polluted air?
A study in 2013 by researchers of Tsinghua University identified more than 1,300 microbes in the atmosphere over Beijing. Although most of them may pose no direct threat to human health, the number still makes for alarming reading. The components of the pollution differ from city to city. In Xi’an most of it is related to coal consumption while Beijing, Shanghai and Guangzhou have more complex sources, due to the growing number of vehicles. Particulate matters due to the burning of oil are more hazardous than those formed by the burning of coal. It is estimated there are some 200 to 300 chemicals in the PM2.5. The most hazardous are organic compounds containing polycyclic aromatic hydrocarbons, a group of compounds thought to be carcinogenic. The most dangerous particles are the PM1 and Shanghai has more of those than Beijing, a reason for visibility on smog days to be worse in Shanghai; I thought it was due to higher humidity. [source: China Daily]