From Time:
Anyone stepping outside in Beijing around midday on June 18 would have noticed something slightly amiss. The sky was dark enough for cars to use their headlights, and the air was as thick as a smoky bar just before last call. After one of the cleanest springs on record, the Chinese capital’s air quality took an unhealthy plunge for the worse.
You wouldn’t have known it by the official numbers. The Ministry of Environmental Protection publishes air quality data online each day at noon, but only for the previous 24-hour-period. Anyone who checked on the afternoon of June 18 would have seen an air pollution figure that indicated Beijing’s skies were “slightly polluted,” referring to the 24 hours before. (See pictures of Beijing’s attempt to clean up its air.)
But a glimpse from another monitoring station that gives hourly updates shows a very different picture. The U.S. Embassy operates a single station in eastern Beijing that records levels of PM2.5, fine particles considered particularly dangerous to human health. At noon that same day, the hourly measure of PM2.5 crept up into the “hazardous” range, according to U.S. Environmental Protection Agency standards, and hit a maximum value of 500 for several hours.
