Whole-Body Counter(WBC) and food radiocesium contamination surveys in Namie, Fukushima Prefecture

Abstract

PurposeThis study examined the internal Cs exposure of residents and the Cs present in food products produced in Namie. Whole-body counter (WBC) was used for the measurement of internal exposure per each whole body of examinees.MethodsThe food products which appeared to be used for consumption, were brought by residents and commercially available food items were excluded. Most of them were wild plants or food items produced by residents. Four years of data from April 2012 to March 2013 (fiscal 2012) and April 2015 to March 2016 (Fiscal 2015) were analyzed and studied.ResultsThe average radioactivity measured by WBC was approximately 5 Bq for Cs-134, and 20 Bq for Cs-137 and the average committed effective dose was approximately 1 μSv. The average for the residents with detectable radioactivity was 25 μSv, and the human health effects are considered to be extremely low risk. However, the radioactivity of the affected individuals showed a higher value than the theoretical attenuation rate. The majority (83.2%) of individuals exhibiting radioactivity were over 50 years old. The number of food products brought in for detection decreased as the study period progressed, but the number of food products with radioactivity had increased. While the items with a higher detection rate of radioactivity included fruits such as citron and persimmon, shiitake mushrooms exhibited the highest radioactivity. Moreover, the radioactivity of seven items in these 10 items decreased from fiscal 2012 to fiscal 2015. Mushrooms had high radioactivity and were produced over a wide area.ConclusionWe suggest that the elderly try to enjoy life and eat wild plants in moderation while inspecting food products. Therefore, we will continue to work in raising awareness of radiation and its potential presence in food products and thus the continuing necessity of monitoring radioactivity in food in the future.

Radiocesium concentrations in mushrooms collected in Kawauchi Village five to eight years after the Fukushima Daiichi Nuclear Power Plant accident

“…After the FDNPP accident, several studies have been reported concentrations of radiocesium in wild mushrooms [ 23 – 25 ]. In Namie town, Fukushima Prefecture, the median concentrations of radiocesium in shiitake mushroom in each year from fiscal 2012 to fiscal 2015 were 4,070, 973, 2,269 and 742 Bq/kg [ 25 ].…”

“…After the FDNPP accident, several studies have been reported concentrations of radiocesium in wild mushrooms [ 23 – 25 ]. In Namie town, Fukushima Prefecture, the median concentrations of radiocesium in shiitake mushroom in each year from fiscal 2012 to fiscal 2015 were 4,070, 973, 2,269 and 742 Bq/kg [ 25 ]. Previously, we evaluated radiocesium concentration in wild mushroom samples collected in Kawauchi village and found that radiocesium exceeding 100 Bq/kg was detected in 125 of 154 samples (81%) in 2013, and in 123 of 159 samples (77%) in 2015 [ 15 , 18 ].…”

Radiocesium contamination and estimated internal exposure doses in edible wild plants in Kawauchi Village following the Fukushima nuclear disaster

“…Nevertheless, the monitoring system for local foods is effective as a risk communication tool in Kawauchi Village. The FDNPP nuclear disaster has necessitated long-term follow-up of environmental monitoring and countermeasures like further decontamination and restriction of the ingestion of foods that can cause unnecessary radiation exposure, and physical and mental health support services [ 43 – 45 ]. Sustained diligence is needed to protect the physical and mental health of Fukushima residents while allowing for their “ satoyama ” (countryside) culture of ingesting " sansai " (edible wild plants) during the remediation of radiation-affected areas, such as Kawauchi Village, following the nuclear disaster.…”

Individual Doses to the Public after the Fukushima Nuclear Accident

“…Two approaches for internal dose estimation. Cs was 0.025 mSv [55]; (5) no child was found to exceed the 137 Cs detection limit of 300 Bq per body (corresponding to the CED of 0.04 mSv due to 137 Cs for a 6-year old) in 2012 and 2013 [56]; (6) among 2,700 babies, none had detectable levels of 134 Cs or 137 Cs (the detectable level of 137 Cs corresponds to 0.016 mSv per year including the contribution from 134 Cs) [57]; and (7) between 12 to 20 months after the accident, the 137 Cs detection frequency was 1.0% among all ages (0.09% among children) [58].…”

“…Some results obtained by operators for categories (ii) and (iii) have been reported as scientific papers: these papers included subjects of Minamisoma City [51,52], Iwaki City (including its suburbs) [53,54], Namie Town [55], and Miharu Town [56], and subjects in and around Fukushima Prefecture [57,58]. All papers reported very low doses as follows: (1) among 9,498 residents measured between September 26, 2011 and March 31, 2012, CEDs were less than 1 mSv except for 1 resident (1.07 mSv) [51]; (2) CEDs of 566 high-risk residents measured about 4 months after the accident were found to be less than 1 mSv [52]; (3) the maximum CEDs in two studies were both less than 0.1 mSv [53,54]; (4) the aver- Fig.…”