Preliminary assessment of ecological exposure of adult residents in Fukushima Prefecture to radioactive cesium through ingestion and inhalation

Abstract

ObjectiveThis study aims to estimate the ecological exposure of adult residents of Fukushima Prefecture to 134cesium (Cs) and 137Cs through ingestion and inhalation between July 2 and July 8, 2011.MethodsFifty-five sets of meals with tap water, each representing one person’s daily intake, were purchased in local towns in Fukushima Prefecture. Locally produced cow’s milk (21 samples) and vegetables (43 samples) were also purchased. In parallel, air sampling was conducted at 12 different sites using a high-volume sampler. Nineteen sets of control meals were collected in Kyoto in July 2011. 134Cs and 137Cs levels in the samples were measured using a germanium detector.ResultsRadioactivity was detected in 36 of the 55 sample meals from Fukushima, compared with one of 19 controls from Kyoto. The median estimated dose level (μSv/year) was 3.0, ranging from not detectable to 83.1. None of the cow’s milk (21) or vegetable (49) samples showed levels of contamination above the current recommended limits (Bq/kg) of 200 for milk and 500 for vegetables. The total effective dose levels by inhalation were estimated to be <3 μSv/year at nine locations, but samples at three other locations close to the edge of the 20-km radius from the crippled nuclear power plant showed higher levels of contamination (μSv/year): 14.7 at Iitate, 76.9 at Namie, and 27.7 at Katsurao.ConclusionsLevels of exposure to 134Cs and 137Cs in Fukushima by ingestion and inhalation are discernible, but generally within recommended limits.Electronic supplementary materialThe online version of this article (doi:10.1007/s12199-011-0251-9) contains supplementary material, which is available to authorized users.

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

“…Nevertheless, these radiation levels were much lower than external radiation dose rates. Participants' residences neighbor the restricted and evacuation areas and participants consume homegrown vegetables; however, the doses were comparable to those in our previous research, which examined food-duplicate samples from relatively urban areas in Fukushima (15,19). Local food supply in farming areas did not necessarily increase exposure to radiocesium because local municipalities routinely screen food products for personal consumption.…”

“…The inhalation of airborne dust comprising resuspended radioactive deposits represents an additional route of internal exposure (17,18). For example, a survey in July 2011 showed that the radiocesium concentration in the air was on the order of 1 mBq/m 3 outside restricted areas (19).…”

Size-distribution of airborne radioactive particles from the Fukushima accident

“…Unfortunately, since additional or extended measurements except for Be-aerosols measured at various seasons during last six years with the same manner mentioned in the text radioactivity measurements could not been done on that occasion, all we can do in this stage is only a matter of speculation with scarce experimental evidence. There are several reports concerning size distributions of airborne radionuclides from the Fukushima accident [4][5][6][7][8][9]; in addition, for the Chernobyl accident there also exist comparable data [10][11][12][13][14][15]. For the measurements in Japan, the size distributions of radiocesium are partly different each other probably depending on the emission process from the reactors or transportation mechanism due to different sampling date and distance from the reactor site.…”

Contamination of Japanese foodstuffs of terrestrial origin after the Fukushima nuclear accident and related dose assessment

“…for the period from May to the end of 2011 Koizumi et al (2011) performed evaluations of doses by ingestion based on measurements made during a week in July 2011 in whole-day meal sets purchased in shops in four towns: Fukushima, Iwaki, Soma and Nihonmatsu. The doses evaluated were extrapolated by Koizumi et al over the course of a year; they range from "non-calculable" (activity below detection limits) to 80 µSv/an (in Soma).…”