Break down of asian dust particle on wet surface and their possibilities of cause of respiratory health effects.

Asian dust (called 'Kosa' in Japan) is comprised of a large number of soil particles originating from the arid regions and deserts of China and Mongolia and dispersed long-range to Japan. A major public concern about Asian dust is its impact on human health. We collected Asian dust particles over the Japan Sea at an altitude of 900 m to directly estimate their effects on health. We examined the properties of the collected particles on wet surfaces. Through size distribution measurements and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis, we demonstrated that small dust particles (less than 1 µm) form aggregations with water-soluble salts such as calcium and sodium and they are transported to Japan as aggregates. These aggregates probably break down into small particles on nasal mucous membranes and may cause adverse respiratory health effects.