**Acknowledgements**

The authors express their gratitude to the former Professor of our Department, Prof. Ayako Ueki, MD, PhD, as well as former members Drs. Akiko Tomokuni-Takata, Fuminori Hyodoh, Takaaki Aikoh, and Yasuhiko Kawakami for their excellent achievement in analyzing the risks of particulate and fibrous substances. Additionally, we thank Ms. Minako Katoh, Naomi Miyahara, Satomi Hatada, Keiko Yamashita, Keiko Kimura, Tomoko Sueishi, Misao Kuroki, and Haruko Sakaguchi for their technical assistance.
