The sizes of sand gains of the kosa that comes flying over a long distance from its source place, for example, to Japan are around 0.5 µm to 5 µm (0.0005 mm to 0.005 mm) that is slightly larger than those of grains in smoke from tobacco (0.2 µm to 0.5 µm) and slightly smaller than the diameters of human red blood cells (6 µm to 8 µm).
日本など発生地から遠くに飛来する黄砂の粒の大きさは0.5µm（マイクロメートル）-5µm(0.0005mm-0.005mm)くらいで、タバコ製品の煙の粒子の直径(0.2-0.5µm)よりやや大きく、人間の赤血球の直径(6-8µm)よりやや小さいくらい。