BEIJING (AP) -- Sandstorms whipping across China shrouded  cities in an unhealthy cloud of sand Monday, with winds carrying the pollution outside the mainland as far as Hong Kong and Taiwan. It was the latest sign of the effects of desertification: Overgrazing, deforestation, urban sprawl  and drought have expanded deserts in the country's north and west. The shifting sands have gradually moved onto populated areas and worsened sandstorms that strike cities, particularly in the spring. 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 _ problems even in healthy people. Drivers complained their cars were covered in a layer of black soot in just 10 minutes. 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 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. 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. A massive sandstorm hit Beijing in 2006, when winds dumped about 300,000 tons of sand on the capital. The passage tells us that the sandstorms mainly came from  _  .
Xinjiang Hangzhou Beijing Inner Mongolia