cesium-studyvia Daily Kos / December 2, 2014 / The purpose of this short diary is to report the results of a very recently published study which used a whole body scanner to look for cesium (134-Cs half life ~ 2 years, 137-Cs half life 30 years) contamination in children directly affected by the Fukushima Dai-ichi nuclear power plant (NPP) disaster (behind pay wall unfortunately).  This diary is part of an ongoing series which reports information gained by scientific study regarding the environmental impact of the triple meltdowns at the NPP site.  Whole body measurements of contamination levels in elementary and middle school students who commute to 22 schools located within Minamisoma City were assessed between May and July 2013 (roughly 2 to 2.5 years after the disaster). Of the 3,299 elementary and middle school students in the city, 3,255 individuals, or 98% of the total were screened through school health check-ups. No children screened had detectable levels of 134-Cs or 137-Cs (detection limits were 220 Bq body-1 and 250 Bq body-1 respectively). Maximum annual effective doses (25-66 µSv yr-1), estimated from diet surveys and the detection limits of the whole body scanner, are much lower than the common dose limit recommendation for the public (1 mSv yr-1). The authors suggest that ongoing food inspection by local governments, volunteers, and farmers has been functioning well within Fukushima prefecture to limit the exposure of residents to contaminants.

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.

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.

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.

SOURCE: Daily Kos

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