South Korea closed schools and factories producing memory chips stepped up safeguards yesterday, as a choking pall of sand mixed with toxic dust from China covered most of the country. The annual ?yellow dust? spring storms, which originate in China?s Gobi Desert before sweeping south to envelop the Korean peninsula and parts of Japan, are blamed for scores of deaths and billions of dollars in damage every year in South Korea. South Korea issued a ?yellow dust? warning at the weekend and yesterday, major schools districts in southeastern regions urged parents to keep kindergarten and elementary school children at home.

?We advised the closure because kindergarten, primary school students have weaker immune systems,? said Min Eyu-gi, an education official in Busan. An official with the Meteorological Administration said the first major storm of the season, which has also hit parts of Japan, was dissipating.