South Korea said a pall of sand mixed with toxic dust from China could make its way to the Korean peninsula late on Thursday, starting a seasonal event blamed for scores of deaths and billions of dollars in damages.
The sandstorms have been growing in frequency and toxicity over the years because of China's rapid economic growth and have led to increased tension with neighbors South Korea and Japan.
"There is an increasing possibility that yellow dust will appear some time between Thursday night and Friday," South Korea's Meteorological Administration said in a posting on its Web site.
The dust, which originates in the Gobi Desert in China, picks up heavy metals and carcinogens such as dioxin as it passes over Chinese industrial regions, before hitting North and South Korea and Japan, meteorologists say.
Dry weather and seasonal winds in China hurl millions of tons of sand at the Korean peninsula and Japan each spring.
South Korea used to have yellow dust storms about four days a year in the 1980s, nearly eight days a year in the 1990s and over 12 days a year since 2000, the Environment Ministry said.
The state-sponsored Korea Environment Institute said the dust kills up to 165 South Koreans a year, mostly the elderly or those with respiratory ailments, and make as many as 1.8 million ill.
Annual economic damage to South Korea from the storms is estimated at between $4.5 billion to $5.9 billion, according to the institute.
When a storm hits, skies turn a jaundiced hue. Schools shut down and warnings are issued for the young, elderly and those with respiratory ailments to stay inside. Commercial aviation can grind to a halt.
Hynix Semiconductor Inc., the world's second-biggest maker of computer memory chips, said it has to step up its filtration systems to keep the air clean at its sensitive production lines in South Korea.
China is likely to suffer more severe sandstorms than normal this spring because of an unusually dry winter, the country's media reported in January.
Beijing, which had 17 sandstorms in the spring of 2006, has pledged to hold a sandstorm-free Olympics in 2008 and has begun campaigns to repair denuded land and rein in over-grazing and over-logging.
South Korea said in December it has reached a deal with Mongolia and China to set up more monitoring stations for dust storms. Environmentalists said it will take a huge amount of money to contain desertification in China's arid regions.
South Korean stores, knowing the problem will not disappear soon, offer special scarves, hats and other accessories for the yellow dust season.
"I do not let my children go out to play when the storms hit," said a mother in central Seoul.