The storms, which soak up toxic pollution as they cross China's heavily industrialized northern areas, are nearly five times more frequent than they were five decades ago, they said.

The problem of the storms figures high on the agenda at the UN Environment Program (UNEP) three-day conference here, which is being attended by environment ministers and officials from more than 150 nations.

UNEP executive director Klaus Toepfer said the hazardous sandstorms were evidence of "the globalization of environmental problems."

"We are worried about the creep of environmental problems -- their disrespect of political boundaries -- and the way they threaten to compound and disrupt the function of major natural systems," Toepfer said.

"We are seeing a globalisation of environmental problems ... and we need urgent and coordinated action from governments, businesses and civil society groups to address it."

UNEP, citing Chinese data, said the average number of sandstorms occurring per year in China was five in the 1960s, eight in the 1970s, 14 in the 1970s, 15 in the 1980s and 24 in the 1990s.

Scientists said their chief concern was the sandstorms' absorption of pollutants and poisonous heavy metals such as lead in sooty smoke as they travelled over northern China.

The storms are blamed for the disruption of communications, respiratory problems and related deaths, particularly among the elderly and children, as well as losses of livestock and crops.

The storms generally occur during North-east Asia's spring, notably in April. Earlier this week, northern Chinese cities including the capital Beijing were choking under a thick cloud of yellow dust.

The latest dust storm affected 70 million people in northern Chinese provinces with visibility in some areas falling to 100 meters (330 feet).

The Korea Meteorological Administration (KMA) said high winds had driven the sand over the peninsuala late Tuesday and early Wednesday.

The storm was expected to blow through the peninsula and to travel as far as Japan, Hawaii and the western seaboard of the United States, KMA officials said.

KMA scientists said April 2002 dust levels in South Korea's capital Seoul were twice the level deemed hazardous to health.

UNEP's annual report attributed the increased intensity of the storms to the expansion of the Gobi Desert in China with land fast deforested for farming. It said the desert expanded by 52,400 square kilometers from 1994 to 1999, inching ever closer to Beijing where some 400 million people were threatened by desertification.

"As it takes much time to resolve the problem, we step up monitoring activities for an early warning system," said Park Young-Woo, director general for international cooperation at South Korea's environment ministry.

The UNEP said it was allocating part of its one million dollar fund in assisting governments with joint work for monitoring and early warning of dust and sandstorms.

Recent scientific reports suggest that dust storms from the Sahara are being linked to algal infestation of Caribbean coral reefs.

TERRA.WIRE