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

Taira, Yasuyuki; Inadomi, Yudai; Hirajou, Shota; Fukumoto, Yusuke; Orita, Makiko; Yamada, Yumiko; Takamura, Noboru

doi:10.1093/jrr/rrz047

Cited by 6 publications

(10 citation statements)

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“…The median ambient dose rate was 0.49 μSv/h (0.19-1.3 μSv/h) along the hiking trail and 0.49 μSv/h (0.14-1.2 μSv/h) off the hiking trail. However, radiocesium was only detected at 2.4% of sites along the hiking trail and at 12.9% sites off the hiking trail 24 . When temporal variations in ambient dose rates in the difficult-to-return to areas of Tomioka Town were evaluated using the RADI-PROBE (car-based survey) during 2018-2019, we confirmed that the dose rates in the area had decreased dramatically due to decontamination efforts 25 .…”

Section: Discussionmentioning

confidence: 93%

“…In the present study, the reduction of radiocesium was estimated to be only 0.35% from October to December 2019 (Supplementary S2) 26,27 . Thus, the median ambient dose rates along the Mt Okura hiking trail remained relatively stable in 2019 20,24 .…”

Section: Discussionmentioning

confidence: 96%

“…3 and Supplementary S1). We also measured the distribution of ambient dose rates in forests around Mt Okura using the RADI-PROBE in 2018 24 . The median ambient dose rate was 0.49 μSv/h (0.19-1.3 μSv/h) along the hiking trail and 0.49 μSv/h (0.14-1.2 μSv/h) off the hiking trail.…”

Section: Discussionmentioning

confidence: 99%

“…When temporal variations in ambient dose rates in the difficult-to-return to areas of Tomioka Town were evaluated using the RADI-PROBE (car-based survey) during 2018-2019, we confirmed that the dose rates in the area had decreased dramatically due to decontamination efforts 25 . 137 Cs was detected at 3.8% to 93% of sites using the RADI-PROBE 25 , while the dose-forming artificial radionuclides 134 Cs and 137 Cs were only prevalent at some measuring sites (Supplementary S1) 24 .…”

Section: Discussionmentioning

confidence: 99%

“…In 2017, we reported that median ambient dose rates around the homes of the residents who had returned to areas where the evacuation order had been lifted in Tomioka Town were 0.20-0.34 µSv/h (1.7-3.0 mSv/y) and the additional radiation exposure dose was estimated at 1.6 mSv/y based on the guidelines from the Ministry of the Environment, Japan 20 . In 2018, we estimated that the median ambient dose rate along the Mt Okura hiking trail was 0.49 μSv/h, and that the individual dose was 0.44 μSv/h (0.42 mSv/y) (Supplementary S1) 24 . In the present study, the median ambient dose rates (0.45-0.48 µSv/h, 3.9-4.2 mSv/y) were higher along the hiking trail than in the residential areas where the evacuation order had been lifted in Tomioka Town.…”

Section: Discussionmentioning

confidence: 99%

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Radiocesium levels in contaminated forests has remained stable, even after heavy rains due to typhoons and localized downpours

Taira

Matsuo

Yamaguchi

et al. 2020

Sci Rep

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In recent years, Japan has suffered serious damage due to natural disasters such as earthquakes, heavy rains due to tropical storms (typhoons) and localized downpours. To assess the chronological changes in the attenuation of external exposure doses and environmental radiation contamination due to the rainfall associated with typhoons and heavy rains during October to December 2019 in Fukushima, we measured environmental radiation levels in forest areas along the Mt Okura hiking trail in Tomioka Town, Fukushima Prefecture, near the Fukushima Daiichi Nuclear Power Station. We confirmed that (1) current ambient dose rates of 0.38–0.95 μSv/h in most forest areas were 79.9–84.7% higher than in residential areas; (2) the number of sites along the hiking trail where 137Cs was detected was limited (1.1–4.7%); and (3) individual dose rates of 0.21–0.34 μSv/h were lower than ambient dose rates. These findings suggest that radiocesium has remained stable in natural forests that have not been decontaminated even though current levels are low, despite the occurrence of heavy rainfall associated with Super Typhoon Hagibis in 2019 and localized downpours. Hiking while managing exposure to environmental contamination using a personal dosimeter may be the safest model for spending time of leisure activities.

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Section: Discussionmentioning

confidence: 93%