Professor and Chairman Atomic Bomb Disease Institute Radiocesium Concentrations in Wild Mushrooms Collected in Kawauchi Village after the Accident at the Fukushima Daiichi Nuclear Power Plant Noboru TAKAMURA Professor and Chairman Atomic Bomb Disease Institute Nagasaki University

Introduction From the experience after the accident at the Chernobyl Nuclear Power Plant (1986) that radiocesium tends to concentrate in wild mushrooms. Comprehensive studies have not been conducted to measure the concentrations of radiocesium in mushrooms in a certain area and to clarify the risk of internal exposure in Fukushima. Aim of the study: To evaluate their radiocesium concentrations in mushrooms to estimate the internal radiation exposure of local residents in Fukushima.

Fukushima Dai-ichi nuclear power plant (FNPP) Tochigi Prefecture Gunma Miyagi Prefecture Yamagata Prefecture Niigata Prefecture 30km 20km Kawauchi village http://www.freemap.jp/ より Fukushima Dai-ichi nuclear power plant (FNPP) Tochigi Prefecture Gunma Prefecture Ibaraki Prefecture

Materials and Methods Collection of wild mushrooms in Kawauchi village from September through November 2013, 30–32 months after the accident in cooperation with the residents (n=154, 22 species). Preparation of samples: dried for 3,600 s Measurement of 134Cs and 137Cs concentrations in dried mushroom Calculation of committed effective doses, based on the average daily and annual intake of Japanese.

Map of mushroom collected in Kawauchi Village ●Sarcodon aspratus　　 ▲Hypholoma sublateritium ◆Armillaria mellea ■Others

Concentrations of radiocesium (134Cs + 137Cs) in dried wild mushrooms Species n Detected number (%) Concentrations of Cs (Bq/kg)* Sarcodon aspratus 79 79/79 (100) 8,794 ± 7,416 (1,250–46,700) Hypholoma sublateritium 11 10/11 (90.9) 4,116 ± 3,531 (164–11,700) Armillaria mellea 10 8/10 (80.0) 1,241 ± 1,318 (124–4,280) Tricholoma matsutake 6 6/6 (100) 4,394 ± 3,910 (1,849–12,180) Pholiota microspora 6 6/6 (100) 13,599 ± 14,543 (1,906–39,500) Lyophyllum shimeji 5 4/5 (80.0) 1,612 ± 674 (701–2,164) Lyophyllum decastes 5 2/5 (40.0) 190 ± 108（113–266） Cortinarius salor Fr. 4 4/4 (100) 74,335 ± 50,014 (8,540–124,900) Boletopsis leucomelas 4 4/4 (100) 7,409 ± 7,827 (1,831–18,490) Pholiota squarrosa 4 1/4 (25) 410 Hygrophorus russula 3 3/3 (100) 26,447 ± 30,298 (7,670–61,400) Grifola frondosa 3 0/3 (0) ND Phaeolepiota aurea 3 0/3 (0) ND Suillus bovinus 2 2/2 (100) 14,535 ± 1,294 (13.620–15,450) Lyophyllum fumosum 2 2/2 (100) 1,742 ± 786 (1,186–2,297) Lepista sordida 1 1/1 (100) 112,400 Lepista nuda 1 1/1 (100) 68,900 Panellus serotinus 1 1/1 (100) 911 Pleurotus ostreatus 1 1/1 (100) 591 Lentinula edodes 1 0/1 (0) ND Armillaria tabescens 1 0/1 (0) ND Entoloma sarcopum 1 0/1 (0) ND

Distribution of radiocesium concentrations (134Cs + 137Cs) in mushrooms 86 Number of samples 36 19 7 6 （Bq/kg-dry）

Committed effective dose due to wild mushroom intake (minimum – maximum) Species n μSv/day mSv/year   Sarcodon aspratus 79 0.037–1.387 0.013–0.506 Hypholoma sublateritium 10 0.004–0.351 0.002–0.128 Armillaria mellea 8 0.003–0.129 0.001–0.047 Tricholoma matsutake 6 0.055–0.362 0.020–0.132 Pholiota microspora 6 0.056–1.184 0.021–0.432 Lyophyllum shimeji 4 0.018–0.066 0.007–0.024 Lyophyllum decastes 2 0.003–0.009 0.001–0.003 Cortinarius salor Fr. 4 0.256–3.748 0.093–1.368 Boletopsis leucomelas 4 0.054–0.551 0.020–0.201 Pholiota squarrosa 1 0.011 0.004 Hygrophorus russula 3 0.229–1.842 0.084–0.672 Suillus bovinus 2 0.408–0.464 0.149–0.169 Lyophyllum fumosum 2 0.037–0.069 0.014–0.025 Lepista sordida 1 3.377 1.232 Lepista nuda 1 2.066 0.754 Panellus serotinus 1 0.027 0.010 Pleurotus ostreatus 1 0.018 0.006

Hypholoma sublateritium* Tricholoma matsutake* Sarcodon aspratus Armillaria mellea* Hypholoma sublateritium* Tricholoma matsutake* Pholiota microspora* Lyophyllum decastes* Lyophyllum shimeji* Cortinarius salor Fr.* Boletopsis leucomelas Pholiota squarrosa Hygrophorus russula* Suillus bovinus* Lyophyllum fumosum* Pleurotus ostreatus Lepista nuda* Panellus serotinus* ＊Photograph；The mushroom of Abukuma spelled with the observation data and the photograph for 15 years

Armillaria tabescens* Grifola frondosa Phaeolepiota aurea* Lentinula edodes* Entoloma sarcopum* Armillaria tabescens* Figure ５　Pictures of mushroom which showed low concentrations (< Bq/kg) of radiocesium ND　  検出限界値以下またはセシウム１３４だけしか検出されておらず合算できなかったきのこが５種類です。 菌根菌：ウラベニホテイシメジ 腐生菌、マイタケ、コガネタケ、シイタケ、ナラタケモドキ 赤：15年間の観察データと写真でつづる阿武隈のきのこH26.08.15 黄：川内村観光協会 *Photograph；The mushroom of Abukuma spelled with the observation data and the photograph for 15 years

Map of mushroom concentrations in Kawauchi Village ●Sarcodon aspratus　　 ▲Hypholoma sublateritium ◆Armillaria mellea ■Others Cs-134＋Cs-137 （Bq/kg-dry） n.d. 100－499 500－999 1,000－9,999 ＞10,000

Risk communication with residents

Discussion Radioactive cesium exceeding 100 Bq/kg was detected in 135 of 154 (87.7%) dried mushrooms collected in Kawauchi Village, Fukushima Prefecture. 17 species showed relatively higher concentrations of radiocesium and five species showed relatively lower concentrations. Concentration of radiocesium might depend on the species of mushroom.

Committed effective doses ranging from 0. 256–3. 748 μSv and 0. 093–1 Committed effective doses ranging from 0.256–3.748 μSv and 0.093–1.368 mSv, respectively, based on the average intake of mushrooms in Japan. Committed effective doses were relatively limited even if residents ate contaminated foods several time. Long-term risk evaluation for the internal radiation exposure of these individuals is needed to gain a better understanding of radiation safety in Fukushima.

Conclusion We evaluated radiocesium concentrations in wild mushrooms collected at Kawauchi Village in Fukushima Prefecture and found that radiocesium exists in wild mushrooms at a relatively high frequency. Take home message: Although committed effective doses are relatively limited even if residents eat contaminated foods several times, we believe that comprehensive risk-communication based on measurements of radiocesium in the food and water, as well as in the soil, is necessary for the recovery of Fukushima after the nuclear disaster.