(ECNS) -- Beijing's air quality dropped sharply on Thursday as a heavy sandstorm swept over the capital from the northwest.
The sandstorm came from central Mongolia and North China's Inner Mongolia Autonomous Region, according to Beijing Municipal Environment Protection Monitoring Center.
It caused levels of PM10, particulate matter with a diameter smaller than 10 microns, to hit 1,000 micrograms per cubic meter by 4am, causing serious air pollution across the city. By 8pm, levels reached 1,582 micrograms per cubic meter on average in Beijing's six districts, with areas in the northwest experiencing more than 2,000 micrograms per cubic meter.
As floating dust and sand shrouded the sky, visibility reduced significantly. Beijing has issued a blue alert, its first this year.
A large swath of China's territory, from southern Xinjiang to Ningxia, northern Shanxi and northwestern Heilongjiang, are set to be hit by dust and sandstorms before 8am Friday, according to weather forecasts.
China has a four-tier color alert system for pollution, with red being the highest, followed by orange, yellow and blue. A blue alert means the air quality index is forecast to reach between 200 and 300 PM2.5 for one day.
