Heavy smog’s return in northern China masks all-too-fleeting memories of Beijing’s blue skies

Face masks are back in business in Beijing and much of northern China as heavy smog has returned with a vengeance – quickly banishing the rare memories of two weeks of blue skies over the capital leading up to the huge military parade on September 3.

At noon on Thursday the air in Beijing was described as “heavily polluted” by Beijing’s Ministry of Environmental Protection.

Concentrations of PM2.5 – superfine particulate matter smaller than 2.5 microns in diameter, which lodge deep inside the lungs and are considered most dangerous to human health – led to the air quality index being measured at 160 micrograms per cubic metre – more than five times above the safety standards recommended by World Health Organisation.

Levels of pollutants fell to below 10 micrograms per cubic metre as clear blue skies – the colour dubbed by residents “parade blue” – returned for 15 consecutive days after about 10,000 factories in Beijing and its neighbouring provinces were closed or forced to cutback on production, while more than 40,000 construction sites were temporarily shut down.

Yet it did not last long: the capital’s air quality index had already returned to an “unhealthy” 158 the morning after the parade, the American Embassy in Beijing reported at the time.

The Beijing Morning Post reported on Thursday that the pollution was likely to continue, with air quality forecasts expected to be “moderately polluted” on Friday.