Table 3.
Radioactivity of 137Cs and natural radionuclides in deciduous teeth (mBq/g).
| 137Cs | 214Pb (U series) | 212Pb (Th series) | 40K | |
|---|---|---|---|---|
| Fukushima A(12) | 0.21 ± 0.07 | 0.91 ± 0.31 | 0.39 ± 0.15 | 7.9 ± 1.5 |
| Fukushima B(23) | 0.39 ± 0.03 | 0.61 ± 0.16 | LTD | 14.0 ± 0.9 |
| Fukushima C(8) | LTD | LTD | LTD | 12.6 ± 3.8 |
| Fukushima D(8) | 0.79 ± 0.09 | LTD | 0.39 ± 0.15 | 10.9 ± 2.8 |
| Hokkaido (21) | 0.14 ± 0.04 | 0.57 ± 0.14 | 0.27 ± 0.07 | 10.2 ± 1.1 |
| Shizuoka (24) | 0.07 ± 0.02 | 0.65 ± 0.16 | 0.24 ± 0.03 | 5.4 ± 1.0 |
| Niigata (8) | 0.60 ± 0.16 | 0.65 ± 0.38 | LTD | 7.9 ± 2.2 |
| Kumamoto (14) | 0.25 ± 0.06 | 0.41 ± 0.18 | LTD | 8.5 ± 1.0 |
Data are shown as mean ± counting error. Parentheses show numbers of teeth in a sample. When the counts did not exceed the mean + 3SD of the background, we considered the value as LTD (lower than detection limit). SD, standard deviation. Since radioactive caesium was not detected during the 1 million seconds measurement (11.6 days), we increased the duration of measurement (Table 1) to 1.6–3.0 million seconds (18.5–34.7 days) to increase peak counts (662 keV). The teeth from the Fukushima prefecture were divided into the following 4 groups according to the time they fell out: Fukushima A, before the FNPP accident; Fukushima B, 0–2 after the FNPP accident; Fukushima C, 2–4 after the FNPP accident; and Fukushima D, 4–6 years after the FNPP accident. 134Cs was undetectable in all samples.