Yukiko Fujii

Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant

Significance There is a potential risk of human exposure to radiation owing to the March 2011 Fukushima Daiichi Nuclear Power Plant accident. In this study, we evaluated radiation dose rates from deposited radiocesium in three areas neighboring the restricted and evacuation areas in Fukushima. The mean annual radiation dose rate in 2012 associated with the accident was 0.89–2.51 mSv/y. The mean dose rate estimates in 2022 are comparable with variations of the average 2 mSv/y background radiation exposure from natural radionuclides in Japan. Furthermore, the extra lifetime integrated dose after 2012 is estimated to elevate lifetime risk of cancer incidence by a factor of 1.03 to 1.05 at most, which is unlikely to be epidemiologically detectable. Radiation dose rates were evaluated in three areas neighboring a restricted area within a 20- to 50-km radius of the Fukushima Daiichi Nuclear Power Plant in August–September 2012 and projected to 2022 and 2062. Study participants wore personal dosimeters measuring external dose equivalents, almost entirely from deposited radionuclides (groundshine). External dose rate equivalents owing to the accident averaged 1.03, 2.75, and 1.66 mSv/y in the village of Kawauchi, the Tamano area of Soma, and the Haramachi area of Minamisoma, respectively. Internal dose rates estimated from dietary intake of radiocesium averaged 0.0058, 0.019, and 0.0088 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. Dose rates from inhalation of resuspended radiocesium were lower than 0.001 mSv/y. In 2012, the average annual doses from radiocesium were close to the average background radiation exposure (2 mSv/y) in Japan. Accounting only for the physical decay of radiocesium, mean annual dose rates in 2022 were estimated as 0.31, 0.87, and 0.53 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. The simple and conservative estimates are comparable with variations in the background dose, and unlikely to exceed the ordinary permissible dose rate (1 mSv/y) for the majority of the Fukushima population. Health risk assessment indicates that post-2012 doses will increase lifetime solid cancer, leukemia, and breast cancer incidences by 1.06%, 0.03% and 0.28% respectively, in Tamano. This assessment was derived from short-term observation with uncertainties and did not evaluate the first-year dose and radioiodine exposure. Nevertheless, this estimate provides perspective on the long-term radiation exposure levels in the three regions.

Dietary Intake of Radiocesium in Adult Residents in Fukushima Prefecture and Neighboring Regions after the Fukushima Nuclear Power Plant Accident: 24-h Food-Duplicate Survey in December 2011

Since the nuclear power plant accident in Fukushima in March 2011, the Japanese government has conducted screening and removal of contaminated foods from the market that exceed provisional regulation limits for radionuclides. This study aimed to provide an urgent estimate of the dietary exposure of adult residents recruited from three areas in Japan to cesium 134 ((134)Cs), cesium 137 ((137)Cs), and, for comparison, natural potassium 40 ((40)K) on December 4, 2011. Fifty-three sets of 24-h food-duplicate samples were collected in Fukushima Prefecture and neighboring regions. The (134)Cs, (137)Cs, and (40)K levels in the samples were measured using a germanium detector. Items in the food-duplicate samples were recorded and analyzed for radiocesium intake. Radiocesium was detected in 25 of 26 samples from Fukushima. The median dietary intake of radiocesium was 4.0 Bq/day (range <0.26-17 Bq/day). The estimated annual dose from radiocesium was calculated assuming that the daily intake of radiocesium was constant throughout the year. The median estimated dose level was 23 μSv/year (range <2.6-99 μSv/year). The estimated dose level of radiocesium was significantly higher in Fukushima than in the Kanto region and western Japan. Stepwise multiple linear regression analyses demonstrated that the intake of fruits and mushrooms produced in Fukushima were significant factors for the dietary intake of (137)Cs in the 26 participants from Fukushima. The average radioactivity (±SD) of locally produced persimmons and apples (n = 16) were 23 ± 28 and 30 ± 35 Bq/kg for (134)Cs and (137)Cs, respectively. The preliminary estimated dietary dose levels among Fukushima residents were much lower than the maximum permissible dose 1 mSv/year, based on new Japanese standard limits for radiocesium in foods (100 Bq/kg for general foods). In future studies, the exposure estimates should be refined by probability sampling to eliminate biases.

Detection of dicofol and related pesticides in human breast milk from China, Korea and Japan.

Previously, we demonstrated that the concentrations of DDTs were greater in breast milk collected from Chinese mothers than from Japanese and Korean mothers. To investigate dicofol as a possible source of the DDTs in human breast milk, we collected breast milk samples from 2007 to 2009 in China (Beijing), Korea (Seoul, Busan) and Japan (Sendai, Takarazuka and Takayama). Using these breast milk samples, we quantified the concentrations of dichlorobenzophenone, a pyrolysis product of dicofol (simply referred to as dicofol hereafter), dichlorodiphenyltrichloroethane and its metabolites (DDTs) using GC-MS. Overall, 12 of 14 pooled breast milk samples from 210 mothers contained detectable levels of dicofol (>0.1 ng g⁻¹ lipid). The geometric mean concentration of dicofol in the Japanese breast milk samples was 0.3 ng g⁻¹ lipid and significantly lower than that in Chinese (9.6 ng g⁻¹ lipid) or Korean breast milk samples (1.9 ng g⁻¹ lipid) (p<0.05 for each). Furthermore, the ΣDDT levels in breast milk from China were 10-fold higher than those from Korea and Japan. The present results strongly suggest the presence of extensive emission sources of both dicofol and DDTs in China. However, exposure to dicofol cannot explain the large exposure of Chinese mothers to DDTs because of the trace levels of dicofol in the ΣDDTs. In the present study, dicofol was confirmed to be detectable in human breast milk. This is the first report to identify dicofol in human samples.

Levels and profiles of long-chain perfluorinated carboxylic acids in human breast milk and infant formulas in East Asia.

In this study, 90 human breast milk samples collected from Japan, Korea, and China were analyzed for perfluorooctanoic acid (PFOA) (C8), perfluorononanoic acid (PFNA) (C9), perfluorodecanoic acid (PFDA) (C10), perfluoroundecanoic acid (PFUnDA) (C11), perfluorododecanoic acid (PFDoDA) (C12), and perfluorotridecanoic acid (PFTrDA) (C13). In addition, infant formulas (n = 9) obtained from retail stores in China and Japan were analyzed. PFOA was the predominant compound and was detected in more than 60% of samples in all three countries. The PFOA, PFNA, PFDA, and PFUnDA levels in Japan were significantly higher than those in Korea and China (p<0.05). The PFTrDA level was highest in Korea (p<0.05). The median PFOA concentrations were 89 pg mL(-1) (48% of total perfluorinated carboxylic acids (PFCAs) (C8-C13)) in Japan, 62 pg mL(-1) (54%) in Korea, and 51 pg mL(-1) (61%) in China. The remaining ∑PFCAs (C9-C13) were 95 pg mL(-1) in Japan, 52 pg mL(-1) in Korea, and 33 pg mL(-1) in China. Among the long-chain PFCAs, odd-numbered PFCAs were more frequently detected than even-numbered PFCAs, except for PFDA in Japan. There were no evident correlations between the mothers demographic factors and the PFCA concentrations. PFOA, PFNA, and PFDA were frequently detected in both Japan and China, but there were no significant differences between the two countries. The total PFCA concentrations in the infant formulas were lower than those in the breast milk samples in Japan (p<0.05), but not in China (p>0.05). In conclusion, various PFCAs were detected in human breast milk samples from East Asian countries.

Ablation of Rnf213 retards progression of diabetes in the Akita mouse

Moyamoya disease (MMD) and moyamoya syndrome are vasculopathies characterized by progressive stenosis in the circle of Willis and its branches. The RNF213 gene, which encodes a novel class of proteins, characterized by both E3 ligase and AAA+ATPase activities, has been identified as the susceptibility gene for MMD. However, its physiological functions remain unknown. MMD and moyamoya syndrome are often accompanied by diabetes mellitus. In this study, we generated Rnf213 knockout (KO) C57BL/6 mice (Rnf213(-/-); Ins2(+/+)), which were mated with Akita (C57BL/6 Rnf213(+/+); Ins2(+/C96Y)) mice, a strain that develops diabetes spontaneously by 5 weeks of age, to obtain mice lacking Rnf213 and carrying the Akita mutation (KO/Akita, Rnf213(-/-); Ins2(+/C96Y)). Body weight and blood glucose concentration were measured from 6 to 20 weeks. Glucose tolerance, insulin resistance, plasma insulin and leptin concentrations, food consumption, pancreatic insulin content and histopathology were evaluated at 18 weeks of age. We found that glucose tolerance, as indicated by AUC, was 20% lower (p<0.05) and insulin contents in pancreas were 150% higher (p<0.05), in KO/Akita than in Akita mice. The number of CHOP positive β-cells assayed by histopathological examination was 30% lower and food consumption was 34% lower in KO/Akita than in Akita mice (p<0.05 each). These findings indicated that the disruption of Rnf213 improved glucose tolerance by protecting islet β cells.

Occurrence of perfluorinated carboxylic acids (PFCAs) in personal care products and compounding agents.

Perfluorinated carboxylic acids (PFCAs), including perfluorooctanoic acid (PFOA), are persistent organic pollutants that pose human health risks. However, sources of contamination and exposure pathways of PFCAs have not been explored. In this study, PFCA concentrations were quantified in personal care products. Among 24 samples that listed fluorinated compounds, such as polyfluoroalkyl phosphate esters (PAPs), in their international nomenclature of cosmetic ingredients (INCI) labels, 21contained PFCAs (13 of 15 cosmetic samples, and 8 of 9 sunscreen samples). The concentrations of total PFCAs ranged from not detected to 5.9 μg g(-1) for cosmetics and from not detected to 19 μg g(-1) for sunscreens. We also investigated components of PFCAs in cosmetics and sunscreens. Commercially available compounding agents, mica and talc, which were treated with PAPs were analyzed and high concentrations of PFCAs were detected (total PFCAs 2.5 μg g(-1) for talc treated with PAPs, 35.0 μg g(-1) for mica treated with PAPs). To the best of our knowledge, this is the first report on contamination of end consumer products containing PAPs with high concentrations of PFCAs.

137Cs Trapped by Biomass within 20 km of the Fukushima Daiichi Nuclear Power Plant

Analysis of (137)Cs trapped in biomass in highly contaminated zones is crucial in predicting the long-term fate of (137)Cs following the explosion at the Fukushima Daiichi Nuclear Power Plant. We surveyed forest 20-50 km from the plant in July and September 2011 to evaluate (137)Cs trapped in biomass within 20 km of the plant. We determined the ambient dose rate and collected forest soils and twigs at 150 sampling points. Removability from the canopy was evaluated by washing leaves and branches with water and organic solvents. The biomass of the forest canopy was then calculated. (137)Cs fallout was simulated with an atmospheric transport model. The modeled dose rate agreed with observations (n = 24) (r = 0.62; p < 0.01). Washing experiments demonstrated that unremovable portions accounted for 53.9 ± 6.4% of (137)Cs trapped by deciduous canopy (n = 4) and 59.3 ± 13.8% of (137)Cs trapped by evergreen canopy (n = 10). In total, it was estimated that 74.5 × 10(12) Bq was trapped by canopy in the forest within the no-go zone, with 44.2 × 10(12) Bq allocated to unremovable portions, and that 0.86% of the total release was trapped in biomass as of September 2011.

Historical trends in human dietary intakes of endosulfan and toxaphene in China, Korea and Japan.

Recently, the Stockholm Convention prohibited the use of toxaphene and has been reviewing endosulfan. The historical use of these pesticides may contaminate food and tend to accumulate in the food chain. In this study, to evaluate the spatial and temporal trends of food contamination, the endosulfan and toxaphene levels were measured in pooled 24-h food composite samples from Chinese (n=10), Korean (n=10) and Japanese (n=40) adults in the 1990s and 2007-2009. Endosulfan was detected in 32 of 40 samples from Japan, but its levels (sum of α- and β-isomers) were low in both the 1990s and 2009 (range as geometric mean (geometric standard deviation) [GM (GSD)]: 0.96 (1.6)-1.42 (1.4) ng kg(-1)d(-1)). The dietary intakes of endosulfan in Seoul as GM (GSD) were 38.68 (1.3) ng kg bw(-1)d(-1) in 1994 and 92.17 (4.4) ng kg bw(-1)d(-1) in 2007, and significantly higher than those in Japan (p<0.05). The samples from Beijing showed a 50-fold increase in the endosulfan levels from 1993 (GM: 0.58 ng kg(-1)d(-1)) to 2009 (GM: 24.91 ng kg bw(-1)d(-1)) (p<0.05). Toxaphene was detected in 33 of 40 samples from Japan. The dietary intake of toxaphene in Japan (sum of Parlars #26, #50 and #62) was 0.32-1.21 ng kg bw(-1)d(-1) (range as geometric mean) and no temporal trend was observed. The dietary intake of toxaphene in Seoul increased significantly from 0.2 ng kg bw(-1)d(-1) (GM) in 1994 to 3.6 ng kg bw(-1)d(-1) (GM) in 2007 (p<0.05). Only one of 10 pooled samples from Beijing contained a detectable level of toxaphene (0.3 ng kg bw(-1)d(-1)). For the entire population, the risk of adverse health effects from dietary intakes of endosulfan and toxaphene is unlikely. However, the concentrations of endosulfan in several samples exceeded 10% of the acceptable daily intake limit value of 6 μg kg bw(-1)d(-1) set by the World Health Organization (WHO). It appears important to refine dietary intake estimates targeting food types and source identification to ensure safe food for consumers.

Comparative survey of levels of chlorinated cyclodiene pesticides in breast milk from some cities of China, Korea and Japan.

Exposure of mothers to organochlorine pesticides (OCPs) was assessed by measuring the levels of 20 OCPs in 70 human breast milk samples pooled from 210 individuals from China, Korea and Japan. The OCPs were analyzed using gas chromatography/mass spectrometry (GC/MS) in electron capture negative ionization (ECNI) monitoring. The results showed that β-hexachlorocyclohexane and hexachlorobenzene were one order of magnitude higher in China than in the other nations, whereas chlordanes and polychlorinated biphenyl levels were highest in Japan. Heptachlor epoxide, dieldrin, endrin, toxaphenes and mirex were detected in most samples, and levels of these chemicals were significantly higher in Japan (0.8-4.5 ng g(-1) lipid), followed by Korea (0.2-4.7 ng g(-1) lipid), and lowest in China (less than 1.0 ng g(-1) lipid). α- and β-endosulfans were detected at a range of 0.9-1.5 ng g(-1) lipid levels in all samples analyzed, and their levels were higher in Korean than in Chinese samples.

Short-chain chlorinated paraffins in cooking oil and related products from China.

Short-chain chlorinated paraffins (SCCPs) are emerging persistent organic pollutants. It has been found that dietary intakes of SCCPs in China have recently increased and are now higher than in Japan and Korea. The contribution of cooking oil to dietary exposure to SCCPs in China was evaluated by analyzing SCCPs in cooking oil, raw seeds used to produce cooking oil, and fried confectionery products collected in China in 2010 and 2012. Detectable amounts of SCCP homologs were found in 48 out of the 49 cooking oil samples analyzed, and the SCCP concentrations varied widely, from <9 to 7500 ng g(-1). Estimated dietary intakes of total SCCPs in cooking oil ranged from <0.78 to 38 μg d(-1). The estimated dietary intake of SCCPs was relatively high (mean 14.8 μg d(-1)) for residents of Beijing. Fried confectionery was found to contain SCCP concentrations of 11-1000 ng g(-1). Cooking oil might therefore be one of the sources of SCCPs to Chinese diets. SCCPs were also detected in raw seeds used to produce cooking oil, but the concentrations varied widely. The SCCP homolog patterns in the raw seed and cooking oil samples were different, implying that the seeds used to produce the oil (and therefore the soil on which the seeds were produced) were unlikely to be the sources of SCCPs in cooking oil. Further investigations are needed to determine the routes through which cooking oil becomes contaminated with SCCPs during the production and processing of the oil.