The Chinese capital Beijing has been hit by a huge sandstorm, causing dangerously levels of pollution and triggering warnings for residents and tourists to remain indoors.
Swathes of dust from Inner Mongolia have been swirling around the city, according to Beijing's environment agency. Other parts of China, including Tianjin and Hebei province, have also been affected.
Levels off pollution reportedly went off the charts. The BBC reports that once inhaled, pollution particles at these levels can make people more vulnerable to respiratory infections, as well as leading to increased mortality from lung cancer and heart disease.
According to discovery.com , the US embassy's air quality index for Beijing hit 516, signalling air quality worse than the highest classification of "hazardous" on Thursday. This dropped during the day but remained high.
Smog had already been forecast but now there's a sandstorm mixed together" Beijing resident Hu Jing told Reuters news agency.
There has been a sharp increase in sandstorms in China in recent years. According to the Press Association, China's expanding deserts now cover one-third of the country because of deforestation, urban sprawl and overgrazing. The shifting sands have led to worsening sandstorms, and the grit can travel as far as the western United States.
Just last month, pollution in Beijing reached hazardous levels: see the video below for more.