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

OBJECTIVE This 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. METHODS Fifty-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. RESULTS Radioactivity 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. CONCLUSIONS Levels of exposure to ¹³⁴Cs and ¹³⁷Cs in Fukushima by ingestion and inhalation are discernible, but generally within recommended limits.