1. .2-2.6 Ushiyama et al. 1991 (20)
2. .1-13.8 Wakabayashi et al. 1992 (3)
3. .5-1.8 Satoh et al. 1984(23) 0.1 National Academy of Sciences 1981 (24) Scanlan 1983 (25)
4. .01-1.4 Ministry of Health and Welfare 1989 (26)
5. .1-1.6 IARC 1983 (27) 3.0 National Academy of Sciences 1981 (24) Scanlan 1983