Scientists say they believe the dust and sand storms that for centuries have blanketed north-east Asia are becoming more dangerous to people's health.
They think the storms are now combining with airborne pollutants emitted by human activities, and are adding to the region's severe air quality problems.
Similar dust storms from the Sahara have been blamed for spreading illness and destroying Caribbean coral reefs.
The concern has been raised with the United Nations Environment Programme.
Unep's governing council is meeting here in Jeju, in South Korea.
It was told four countries have joined in an effort to tackle the problem of the storms.
Records of severe storms here go back at least to the 16th Century: one account from the Korean capital, Seoul, in 1550 spoke of "a fog that looked like smoke creeping into every corner in all directions".
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