The paper by Tsubokura and colleagues was published in the peer reviewed journal Health Physics (behind a pay wall). The authors collected data on internal radiation contamination in elementary and middle school students who commute to 22 schools located in Minamisoma City using a whole body gamma counter. The total body burden of radioactive cesium isotopes was a key variable as these isotopes are likely to be the most significant fission products with respect to total internal radiation exposure. Students from 6 to 12 years of age visited Minamisoma Municipal General Hospital, while middle school students from the ages of 12 to 15 years were screened at Watanabe Hospital. The hospital locations are indicated below relative to the exclusion and controlled zones around the Fukushim Dai-ichi NPP.
All measurements were performed at Minamisoma Municipal General Hospital and Watanabe Hospital, both of which are located 23 km north of the plant.
Results indicated that none of the students had detectable levels of internal contamination with radiocesium. The stated detection limits of the analyses were 220 Bq body-1 for 134-Cs and 250 Bq body-1 for 137-Cs. No other gamma emitting radionuclides, with the exception of naturally occurring potassium-40 (K-40), were detected. The children did not report with any acute health problems. The authors calculate estimated maximum, combined, annual effective doses from 134-Cs and 137-Cs of 66, 40, and 25 µSv yr-1 for children aged 6, 10, and 15 years, respectively. The estimated does are well below the accepted dose limit recommendation for the public of ~1 mSv yr-1.
The results of this study are similar to previous work which failed to find internal cesium in children using a scanner with a significantly lower detection limit of 50 Bq body-1. While these studies suggest that the contamination of children thus far is minimal other work by Tsubokura has detected limited contamination of adult populations eating diets rich in country foods.
Tsubokura M, Gilmour S, Takahashi K, Oikawa T, Kanazawa Y. Internal radiation exposure after the Fukushima nuclear power plant disaster. JAMA 308: 669–670; 2012.
The work thus far using whole body scanning devices suggests that internal radiation contamination of residents near the Fukushima Dai-ichi NPP is low. The authors stress that continued diet management and screening of foodstuffs for contamination in combination with whole body screening are will help in efforts to avoid or limit internal radiation exposure in contaminated areas of Japan.
Comments are closed on this story.