2023-04-24 400ppm未満が理想(途中) www.njkk.co.jp https://www.mhlw.go.jp/content/11130500/000771215.pdf http://www.shasej.org/recommendation/6-9%20kanki%20teigen%202021.06.21.pdf http://www.kankyokansen.org/uploads/uploads/files/jsipc/20220128-iryo-seminar_1.pdf