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

Abstract

Kawauchi Village, in Fukushima Prefecture, is located within a 30-km radius of the nuclear disaster site of the Fukushima Daiichi Nuclear Power Plant (FDNPP). “Sansai” (edible wild plants) in this village have been evaluated by gamma spectrometry after the residents had returned to their homes, to determine the residents’ risk of internal exposure to artificial radionuclides due to consumption of these plants. The concentrations of radiocesium (cesium-134 and cesium-137) were measured in all 364 samples collected in spring 2015. Overall, 34 (9.3%) samples exceeded the regulatory limit of 100 Bq/kg established by Japanese guidelines, 80 (22.0%) samples registered between 100 Bq/kg and 20 Bq/kg, and 250 (68.7%) registered below 20 Bq/kg (the detection limit). The internal effective doses from edible wild plants were sufficiently low (less than 1 mSv/y), at 3.5±1.2 μSv/y for males and 3.2±0.9 μSv/y for females (2.7±1.5 μSv/y for children and 3.7±0.7 μSv/y for adults in 2015). Thus, the potential internal exposure doses due to consumption of these edible wild plants were below the applicable radiological standard limits for foods. However, high radiocesium levels were confirmed in specific species, such as Eleutherococcus sciadophylloides (“Koshiabura”) and Osmunda japonica (Asian royal fern, “Zenmai”). Consequently, a need still might exist for long-term follow-up such as environmental monitoring, physical and mental support to avoid unnecessary radiation exposure and to remove anxiety about adverse health effects due to radiation. The customs of residents, especially the “satoyama” (countryside) culture of ingesting “sansai,” also require consideration in the further reconstruction of areas such as Kawauchi Village that were affected by the nuclear disaster.

Evaluation of Environmental Contamination and Estimated Radiation Exposure Dose Rates among Residents Immediately after Returning Home to Tomioka Town, Fukushima Prefecture

“…Especially, agricultural activities and the countryside ( satoyama ) cultural practice of ingesting edible wild plants ( sansai ) and mushrooms are being carried out carefully based on the guidelines by the Nuclear Emergency Response Headquarters of the Japanese government, accompanied by the ongoing decontamination of farmlands and radiation monitoring [5,38]. Edible wild plants and mushrooms are well-known as accumulators of radiocesium [16,18,19,39,40,41,42]. Currently, the shipment of agricultural products in Japan is determined based on regulations outlined by the Japanese government [43].…”

Radiocesium concentrations in wild boars captured within 20 km of the Fukushima Daiichi Nuclear Power Plant

“…The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident that occurred in 2011 released large amounts of artificial radioactive substances into the environment, particularly cesium-137 ( 137 Cs; 8.8 PBq; half-life: 30.2 years), cesium-134 ( 134 Cs; 9.0 PBq; half-life: 2.1 years), and iodine-131 ( 131 I; 120.0 PBq; half-life: 8 days) 1 . The introduced radionuclides were deposited over a wide area of Fukushima Prefecture and accumulated in local food [2][3][4] . From April 2012, the Japanese government set the regulatory limit for radiocesium in general foods as 100 Bq/kg 5 .…”

Eight years post-Fukushima: is forest decontamination still necessary?

“…These findings indicate that the current radiocesium contamination levels differ substantially between Mt Okura and Mt Takatsuka, as radiocesium derived from the FDNPS accident is found in significantly higher levels at Mt Okura. The customs of residents, especially the ‘ satoyama ’ (countryside) culture of ingesting ‘ sansai ’ (edible wild plants), also require consideration in the further reconstruction of areas that were affected by the nuclear disaster such as Tomioka Town and Kawauchi Village [10, 12]. Although radiocesium contamination has been decreasing in the living spaces of Tomioka Town and Kawauchi Village, an external exposure risk remains in the forest environment [10].…”