Table 1.
The distribution of the number of sentinel sites by dose of soil radiation and average of population aged <20 years (for 1-km radius of each sentinel site)
| Soil radiation dm (μGy/h) | Influenza (proportion out of 4496) | Average of population | Norovirus (proportion out of 3064) | Average of population |
|---|---|---|---|---|
| 0 < dm < 0·01 | 36 (0·008) | 904 | 27 (0·009) | 1464 |
| 0·01 ⩽ dm < 0·02 | 8 (0·002) | 1235 | 4 (0·001) | 1242 |
| 0·02 ⩽ dm < 0·03 | 142 (0·032) | 2148 | 94 (0·031) | 1427 |
| 0·03 ⩽ dm < 0·04 | 534 (0·115) | 3262 | 351 (0·115) | 1885 |
| 0·04 ⩽ dm < 0·05 | 923 (0·205) | 3453 | 616 (0·201) | 2087 |
| 0·05 ⩽ dm < 0·06 | 898 (0·200) | 2752 | 606 (0·198) | 1783 |
| 0·06 ⩽ dm < 0·07 | 632 (0·141) | 2047 | 414 (0·135) | 1363 |
| 0·07 ⩽ dm < 0·08 | 446 (0·099) | 2735 | 345 (0·113) | 1667 |
| 0·08 ⩽ dm < 0·09 | 316 (0·070) | 3582 | 227 (0·074) | 2322 |
| 0·09 ⩽ dm < 0·10 | 210 (0·047) | 3378 | 151 (0·049) | 1940 |
| 0·10 ⩽ dm < 0·11 | 122 (0·027) | 4362 | 77 (0·025) | 2349 |
| 0·11 ⩽ dm < 0·12 | 100 (0·022) | 4113 | 61 (0·020) | 2216 |
| 0·12 ⩽ dm < 0·13 | 56 (0·012) | 3324 | 41 (0·013) | 1959 |
| 0·13 ⩽ dm < 0·14 | 34 (0·008) | 2191 | 24 (0·008) | 1235 |
| 0·14 ⩽ dm < 0·15 | 22 (0·005) | 2378 | 15 (0·005) | 1608 |
| 0·15 ⩽ dm < 0·16 | 17 (0·004) | 2824 | 11 (0·004) | 1382 |
| Total | 4496 | – | 3064 | – |
Dose of soil radiation was calculated from data of three radioactive components observed in soil samples which were collected between 1999 and 2003 in Japan. A small number of sentinel sites located in areas with radiation exposure dose 0·16 ⩽ dm μGy/h, were excluded from this study.
Population (national census data of 2005) was extracted by 1-km radius for each sentinel site.