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Hayano R.S.,University of Tokyo | Tsubokura M.,Tokyo Medical University | Miyazaki M.,Fukushima Medical University | Ozaki A.,Minamisoma Municipal General Hospital | And 10 more authors.
Proceedings of the Japan Academy Series B: Physical and Biological Sciences

BABYSCAN, a whole-body counter (WBC) for small children was developed in 2013, and units have been installed at three hospitals in Fukushima Prefecture. Between December, 2013 and March, 2015, 2707 children between the ages of 0 and 11 have been scanned, and none had detectable levels of radioactive cesium. The minimum detectable activities (MDAs) for 137Cs were ≤3.5 Bq kg-1 for ages 0-1, decreasing to ≤2Bq kg-1 for ages 10-11. Including the 134Cs contribution, these translate to a maximum committed effective dose of ~16 μSv y-1 even for newborn babies, and therefore the internal exposure risks can be considered negligibly small. Analysis of the questionnaire filled out by the parents of the scanned children regarding their families' food and water consumption revealed that the majority of children residing in the town of Miharu regularly consume local or home-grown rice and vegetables, while in Minamisoma, a majority avoid tap water and produce from Fukushima. The data show, however, no correlation between consumption of locally produced food and water and the children's body burdens. © 2015 The Japan Academy. Source

Furutani T.,Keio University | Tsubokura M.,Tokyo Medical University | Uehara K.,Keio University | Nihei M.,Hirata Radioactivity Inspection Center | Sakuma Y.,Hirata Radioactivity Inspection Center
Journal of Disaster Research

This paper aims to clarify the effect of 137Cs internal exposure after the Fukushima Daiichi NPP accident. Using data of approximately 34,000 examinees of a whole-body counter conducted by the Hirata Central Hospital from October 11, 2011 to January 31, 2013, the relationship between internal radiation dose and food ingestion is empirically and quantitatively demonstrated. As a result, elderly people who lived near the Fukushima NPPs and have daily eaten local rice and fungi have a tendency to display higher internal radiation dose. Source

Tsubokura M.,Tokyo Medical University | Kato S.,Soma Central Hospital | Nomura S.,Imperial College London | Gilmour S.,University of Tokyo | And 6 more authors.

Maintaining low levels of chronic internal contamination among residents in radiation-contaminated areas after a nuclear disaster is a great public health concern. However, the efficacy of reduction measures for individual internal contamination remains unknown. To reduce high levels of internal radiation exposure in a group of individuals exposed through environmental sources, we performed careful dietary intervention with identification of suspected contaminated foods, as part of mass voluntary radiation contamination screenings and counseling program in Minamisoma Municipal General Hospital and Hirata Central Hospital. From a total of 30,622 study participants, only 9 residents displayed internal cesium-137 (Cs-137) levels of more than 50 Bq/kg. The median level of internal Cs-137 contamination in these residents at the initial screening was 4,830 Bq/body (range: 2,130-15,918 Bq/body) and 69.6 Bq/kg (range: 50.7-216.3 Bq/kg). All these residents with high levels of internal contamination consumed homegrown produce without radiation inspection, and often collected mushrooms in the wild or cultivated them on bed-logs in their homes. They were advised to consume distributed food mainly and to refrain from consuming potentially contaminated foods without radiation inspection and local produces under shipment restrictions such as mushrooms, mountain vegetables, and meat of wild life. A few months after the intervention, re-examination of Cs levels revealed remarkable reduction of internal contamination in all residents. Although the levels of internal radiation exposure appear to be minimal amongst most residents in Fukushima, a subset of the population, who unknowingly consumed highly contaminated foodstuffs, experienced high levels of internal contamination. There seem to be similarities in dietary preferences amongst residents with high internal contamination levels, and intervention based on pre- and post-test counseling and dietary advice from medical care providers about risky food intake appears to be a feasible option for changing residents' dietary practices, subsequently resulting in a reduction in Cs internal contamination levels. © 2014 Tsubokura et al. Source

Tsubokura M.,Tokyo Medical University | Tsubokura M.,Hirata Radioactivity Inspection Center | Kato S.,Soma Central Hospital | Nihei M.,Hirata Radioactivity Inspection Center | And 9 more authors.

Resettlement to their radiation-contaminated hometown could be an option for people displaced at the time of a nuclear disaster; however, little information is available on the safety implications of these resettlement programs. Kawauchi village, located 12-30 km southwest of the Fukushima Daiichi nuclear power plant, was one of the 11 municipalities where mandatory evacuation was ordered by the central government. This village was also the first municipality to organize the return of the villagers. To assess the validity of the Kawauchi villagers' resettlement program, the levels of internal Cesium (Cs) exposures were comparatively measured in returnees, commuters, and non-returnees among the Kawauchi villagers using a whole body counter. Of 149 individuals, 5 villagers had traceable levels of Cs exposure; the median detected level was 333 Bq/body (range, 309-1050 Bq/kg), and 5.3 Bq/kg (range, 5.1-18.2 Bq/kg). Median annual effective doses of villagers with traceable Cs were 1.1 × 10-2 mSv/y (range, 1.0 × 10-2-4.1 × 10-2 mSv/y). Although returnees had higher chances of consuming locally produced vegetables, Cochran-Mantel-Haenszel test showed that their level of internal radiation exposure was not significantly higher than that in the other 2 groups (p=0.643). The present findings in Kawauchi village imply that it is possible to maintain internal radiation exposure at very low levels even in a highly radiation-contaminated region at the time of a nuclear disaster. Moreover, the risks for internal radiation exposure could be limited with a strict food control intervention after resettlement to the radiation-contaminated village. It is crucial to establish an adequate number of radio-contaminated testing sites within the village, to provide immediate test result feedback to the villagers, and to provide education regarding the importance of re-testing in reducing the risk of high internal radiation exposure. © 2013 Tsubokura et al. Source

Tsubokura M.,Tokyo Medical University | Nihei M.,Hirata Radioactivity Inspection Center | Sato K.,Hirata Radioactivity Inspection Center | Masaki S.,Hirata Radioactivity Inspection Center | And 10 more authors.
Health Physics

Decontamination workers may face a high risk of exposure to internal irradiation through inhalation during decontamination activities; there is, however, little previous research on the levels of internal contamination during decontamination procedures. The authors reviewed the medical records, including whole body counter measurements, of decontamination workers in villages near the crippled Fukushima Daiichi Nuclear Power Plant to assess their levels of internal radiation exposure. In total, 83 decontamination workers were enrolled in this study. They were regularly engaged in decontamination activities in highly contaminated areas where surface 137Cs deposition density was over 100 kBq m-2. The present study showed low levels of internal exposure among the decontamination workers near the Fukushima Daiichi nuclear plant. The cesium burdens of all the decontamination workers were below detection limits. They had reported no acute health problems. The resuspension of radioactive materials may cause minimal internal contamination during decontamination activities. © 2013 Health Physics Society. Source

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