Winds blowing from the northwest have been sweeping sand across the country since Saturday, affecting Xinjiang in the far west all the way to Beijing in the country's east. The sand and dust were carried to parts of southern China and even to cities in Taiwan, 1600 miles (2600 kilometers) away from Inner Mongolia where much of the pollution originated.
The sandstorm in Taiwan, an island 100 miles (160 kilometers) away from the mainland, forced people to cover their faces to avoid breathing in the grit that can cause chest discomfort and respiratory problems even in healthy people. Drivers complained their cars were covered in a layer of black soot in just 10 minutes.
The airport on the Taiwanese-controlled islet of Matsu, just off the mainland coast, suspended services Sunday due to poor visibility caused by the sandstorm.
In Hong Kong, environmental protection officials said pollution levels were climbing as the sandstorm moved south. Twenty elderly people sought medical assistance for shortness of breath, Hong Kong's radio RTHK reported.
The Hong Kong government urged people to stay indoors and encouraged schools to cancel sports events.
The latest sandstorm was expected to hit South Korea on Tuesday, said Kim Seung-bum of the Korea Meteorological Administration. The sandstorm that raked across China over the weekend caused the worst "yellow dust" haze in South Korea since 2005, and authorities issued a rare nationwide dust advisory.
Grit from Chinese sandstorms has been found to travel as far as the western United States.
China's Central Meteorological Station urged people to close doors and windows, and cover their faces with masks or scarves when going outside. Sensitive electronic and mechanical equipment should be sealed off, the station said in a warning posted Monday on its Web site.
China Central Television told viewers to clean out their noses with salt water and remove grit from ears with cotton swabs dipped in alcohol.
State television's noon newscast showed the tourist city of Hangzhou on the eastern coast, where graceful bridges and waterside pagodas were hidden in a mix of sand and other pollution. In Beijing, residents and tourists with faces covered scurried along sidewalks to minimize exposure to the pollution.
The U.S. Embassy in Beijing warned that particulate matter in the air made conditions "hazardous," though high winds dispersed some of the pollution and the air quality was later upgraded to "very unhealthy."
Duan Li, a spokeswoman for the Beijing Meteorological Station, said conditions in the city seemed more severe because a sandstorm on Saturday deposited grit on rooftops, sidewalks and trees. The winds Monday carried in even more sand and stirred up what was already there.
A massive sandstorm hit Beijing in 2006, when winds dumped about 300,000 tons of sand on the capital.