Beijing…declared its first ever red smog alert…Levels of PM2.5, tiny fragments of particulate matter deemed highly harmful as they are inhaled deep into the lungs, were measured to be as high as 350 microgrammes per cubic metre early Tuesday evening Beijing time, compared with 25 microgrammes the level the World Health Organisation thinks it is safe to inhale…  

Although much of Beijing’s pollution migrates from surrounding provinces, where heavy industry and district heating emits harmful particulates and burns large amounts of smog-causing coal, around two-thirds of the capital’s toxic air is judged to come from sources within the city limits. Vehicles are estimated to account for one-third of Beijing’s smog, with construction, household burning of coal and other highly localised activities believed to account for the remainder…