FIGURE 3.

Morphological features of attapulgite particles collected on the filters used in the personal exposure measurement. Samples were examined using an immersion oil with a refractive index of 1.550. The images were observed using dispersion staining‐phase contrast microscopy with ×100 (upper) and ×400 (lower) lenses. Left and right images show the samples provided by company A and B, respectively. White bars in the upper and lower images indicate 80 and 20 μm, respectively. The rectangles in the upper images are the visual fields of the lower images. The white arrows in the lower images indicate examples of particles showing the dispersion color of blue