Beijing caught out as year's first severe dust storm goes off the scale
Capital caught by surprise as meters fail to record severity of air pollution
Air pollution levels in Beijing were so high they went off the Air Quality Index system scale yesterday as the capital was hit by the year's first severe dust storm.
By noon nearly all Chinese government monitoring stations were recording AQI readings of 500, the nominal maximum of the scale. While the monitoring system at the US embassy in Beijing records AQI readings that are in the so-called Beyond Index - in January it recorded 545 - no readings were available yesterday owing to equipment failure.
Chinese internet users referred to the phenomenon as , or "busted meters".
The problem occurs when at least one type of pollutant exceeds the maximum amount that can be used in the AQI calculation. This time, relatively large fine particulate matter (PM) appeared to be the problem.
Many areas in the capital recorded nearly 1,000 micrograms of PM10 (particles 10 micrometres in diameter or less) per cubic metre of air, but most also recorded fewer than 100 micrograms of PM2.5 (of 2.5 micrometres or less), official data said.
Dust storms often hit Beijing and other parts of northern China in the spring, when strong winds from the northwest carry in dust and sand from the Gobi desert in Inner Mongolia.
Yet in recent years the frequency and severity of dust storms has decreased. Experts attribute this to climate change and deliberate human intervention, such as the creation of artificial forests in many places along the storms' typical routes.
Yesterday's dust storm caught many people by surprise. "I dared not open my car windows even for a second," said resident Li Chen, who had been visiting relatives' graves with her family. "There was dust everywhere and the sky was so brown my children refused to get out of the car.
"But I am not sure whether it is worse than smog. The air was dirty but it did not smell as bad as the days with high PM2.5."
Beijing officials told that a dust storm in Mongolia on Friday might have contributed to the high AQI level.
