Research

14 pages, 2961 KiB

Open AccessArticle

Transition of Radioactive Cesium Deposition in Reproductive Organs of Free-Roaming Cats in Namie Town, Fukushima

by Yohei Fujishima, Yasushi Kino, Takumi Ono, Valerie Swee Ting Goh, Akifumi Nakata, Kentaro Ariyoshi, Kosuke Kasai, Tadashi Toyoda, Toru Akama, Hirofumi Tazoe, Masatoshi Yamada, Mitsuaki A. Yoshida and Tomisato Miura

Int. J. Environ. Res. Public Health 2021, 18(4), 1772; https://doi.org/10.3390/ijerph18041772 - 11 Feb 2021

Cited by 2 | Viewed by 3143

Abstract

We investigated the internal contamination by radioactive cesium associated with the FDNPP accident, in the testes or uterus and ovaries of free-roaming cats (Felis silvestris catus), which were protected by volunteers in the Namie Town, Fukushima. A total of 253 samples [...] Read more.

We investigated the internal contamination by radioactive cesium associated with the FDNPP accident, in the testes or uterus and ovaries of free-roaming cats (Felis silvestris catus), which were protected by volunteers in the Namie Town, Fukushima. A total of 253 samples (145 testes and 108 uterus and ovaries) obtained from adult cats and 15 fetuses from 3 pregnant female cats were measured. Free-roaming cats in Namie Town had a higher level of radioactive contamination in comparison to the control group in Tokyo, as the ¹³⁴Cs + ¹³⁷Cs activity concentration ranged from not detectable to 37,882 Bq kg⁻¹ in adult cats. Furthermore, the radioactivity in the fetuses was almost comparable to those in their mother’s uterus and ovaries. The radioactivity was also different between several cats protected in the same location, and there was no significant correlation with ambient dose-rates and activity concentrations in soil. Moreover, radioactive cesium levels in cats decreased with each year. Therefore, it is likely that decontamination work in Namie Town and its surroundings could affect radioactive cesium accumulation, and thus possibly reduce the internal radiation exposure of wildlife living in contaminated areas. It is hence necessary to continue radioactivity monitoring efforts for the residents living in Namie Town. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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11 pages, 2852 KiB

Open AccessArticle

Long-Term Measurements of Radon and Thoron Exhalation Rates from the Ground Using the Vertical Distributions of Their Activity Concentrations

by Oumar Bobbo Modibo, Yuki Tamakuma, Takahito Suzuki, Ryohei Yamada, Weihai Zhuo, Chutima Kranrod, Kazuki Iwaoka, Naofumi Akata, Masahiro Hosoda and Shinji Tokonami

Int. J. Environ. Res. Public Health 2021, 18(4), 1489; https://doi.org/10.3390/ijerph18041489 - 04 Feb 2021

Cited by 11 | Viewed by 2849

Abstract

A long-term measurement technique of radon exhalation rate was previously developed using a passive type radon and thoron discriminative monitor and a ventilated type accumulation chamber. In the present study, this technique was applied to evaluate the thoron exhalation rate as well, and [...] Read more.

A long-term measurement technique of radon exhalation rate was previously developed using a passive type radon and thoron discriminative monitor and a ventilated type accumulation chamber. In the present study, this technique was applied to evaluate the thoron exhalation rate as well, and long-term measurements of radon and thoron exhalation rates were conducted for four years in Gifu Prefecture. The ventilated type accumulation chamber (0.8 × 0.8 × 1.0 m³) with an open bottom was embedded 15 cm into the ground. The vertical distributions of radon and thoron activity concentrations from the ground were obtained using passive type radon-thoron discriminative monitors (RADUETs). The RADUETs were placed at 1, 3, 10, 30, and 80 cm above the ground inside the accumulation chamber. The measurements were conducted from autumn 2014 to autumn 2018. These long-term results were found to be in good agreement with the values obtained by another methodology. The radon exhalation rates from the ground showed a clearly seasonal variation. Similar to findings of previous studies, radon exhalation rates from summer to autumn were relatively higher than those from winter to spring. In contrast, thoron exhalation rates were not found to show seasonal variation. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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16 pages, 2856 KiB

Open AccessArticle

A New Methodology for Defining Radon Priority Areas in Spain

by Alicia Fernández, Carlos Sainz, Santiago Celaya, Luis Quindós, Daniel Rábago and Ismael Fuente

Int. J. Environ. Res. Public Health 2021, 18(3), 1352; https://doi.org/10.3390/ijerph18031352 - 02 Feb 2021

Cited by 8 | Viewed by 2478

Abstract

One of the requirements of EU-BSS (European Basic Safety Standards) is the design and implementation of a National Radon Action Plan in the member states. This should define, as accurately as possible, areas of risk for the presence of radon gas (²²² [...] Read more.

One of the requirements of EU-BSS (European Basic Safety Standards) is the design and implementation of a National Radon Action Plan in the member states. This should define, as accurately as possible, areas of risk for the presence of radon gas (²²²Rn) in homes and workplaces. The concept used by the Spanish Nuclear Safety Council (CSN), the body responsible for nuclear safety and radiation protection in Spain, to identify “radon priority areas” is that of radon potential. This paper establishes a different methodology from that used by the CSN, using the same study variables (indoor radon measurements, gamma radiation exposure data, and geological information) to prepare a radon potential map that improves the definition of the areas potentially exposed to radon in Spain. The main advantage of this methodology is that by using simple data processing the definition of these areas is improved. In addition, the application of this methodology can improve the delimitation of radon priority areas and can be applied within the cartographic system used by the European Commission-Joint Research Center (EC-JRC) in the representation of different environmental parameters. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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8 pages, 988 KiB

Open AccessArticle

Measurement of Indoor Thoron Gas Concentrations Using a Radon-Thoron Discriminative Passive Type Monitor: Nationwide Survey in Japan

by Tetsuya Sanada

Int. J. Environ. Res. Public Health 2021, 18(3), 1299; https://doi.org/10.3390/ijerph18031299 - 01 Feb 2021

Cited by 6 | Viewed by 2034

Abstract

As part of a nationwide survey of thoron (²²⁰Rn) in Japan, the indoor ²²⁰Rn gas concentrations in 940 dwellings were measured throughout one year, from 1993 to 1996, using a passive type ²²²Rn-²²⁰Rn discriminative monitor. The monitor [...] Read more.

As part of a nationwide survey of thoron (²²⁰Rn) in Japan, the indoor ²²⁰Rn gas concentrations in 940 dwellings were measured throughout one year, from 1993 to 1996, using a passive type ²²²Rn-²²⁰Rn discriminative monitor. The monitor was placed in a bedroom or a living room in each house for four successive three-month periods. The mean annual indoor ²²⁰Rn concentration was estimated from the four measurements in each house. The arithmetic mean, the median and the geometric mean for indoor ²²⁰Rn concentrations in 899 dwellings were 20.1, 9.6 and 10.0 Bq m⁻³, respectively. The ²²⁰Rn concentrations exhibited a log-normal distribution. It was found that the ²²⁰Rn concentrations were dependent on the nature of the materials used for wall construction and also on the distance of measurement from the wall. Significant seasonal variations in the ²²⁰Rn concentration were not observed. It would seem that the nature of the wall material contributed to the increased indoor ²²⁰Rn concentrations. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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12 pages, 2827 KiB

Open AccessArticle

Temporal and Spatial Variation of Radon Concentrations in Environmental Water from Okinawa Island, Southwestern Part of Japan

by Shunya Nakasone, Akinobu Ishimine, Shuhei Shiroma, Natsumi Masuda, Kaori Nakamura, Yoshitaka Shiroma, Sohei Ooka, Masahiro Tanaka, Akemi Kato, Masahiro Hosoda, Naofumi Akata, Yumi Yasuoka and Masahide Furukawa

Int. J. Environ. Res. Public Health 2021, 18(3), 998; https://doi.org/10.3390/ijerph18030998 - 23 Jan 2021

Cited by 2 | Viewed by 2977

Abstract

In this study, to get a better understanding in characterizing groundwater and ensure its effective management, the radon concentrations in water samples were measured through Ryukyu limestone in southern Okinawa Island, Japan. Water samples were collected from a limestone cave (Gyokusendo cave, dropping [...] Read more.

In this study, to get a better understanding in characterizing groundwater and ensure its effective management, the radon concentrations in water samples were measured through Ryukyu limestone in southern Okinawa Island, Japan. Water samples were collected from a limestone cave (Gyokusendo cave, dropping water) and two springs (Ukinju and Komesu, spring water), and the radon concentrations were measured by liquid scintillation counters. The radon concentrations in the samples from the Gyokusendo cave, and Ukinju and Komesu springs were 10 ± 1.3 Bq L⁻¹, 3.2 ± 1.0 Bq L⁻¹, and 3.1 ± 1.1 Bq L⁻¹, respectively. The radon concentrations showed a gradually increasing trend from summer to autumn and decreased during winter. The variation of radon concentrations in the dripping water sample from the Gyokusendo cave showed a lagged response to precipitation changes by approximately 2–3 months. The estimated radon concentrations in the dripping water sample were calculated with the measured radon concentrations from the dripping water obtained during the study period. Based on our results, groundwater in the Gyokusendo cave system was estimated to percolate through the Ryukyu limestone in 7–10 days, and the residence time of groundwater in the soil above Gyokusendo cave was estimated to be approximately 50–80 days. This work makes a valuable contribution to the understanding of groundwater processes in limestone aquifers, which is essential for ensuring groundwater sustainability. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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16 pages, 2334 KiB

Open AccessArticle

Discriminative Measurement of Absorbed Dose Rates in Air from Natural and Artificial Radionuclides in Namie Town, Fukushima Prefecture

by Koya Ogura, Masahiro Hosoda, Yuki Tamakuma, Takahito Suzuki, Ryohei Yamada, Ryoju Negami, Takakiyo Tsujiguchi, Masaru Yamaguchi, Yoshitaka Shiroma, Kazuki Iwaoka, Naofumi Akata, Mayumi Shimizu, Ikuo Kashiwakura and Shinji Tokonami

Int. J. Environ. Res. Public Health 2021, 18(3), 978; https://doi.org/10.3390/ijerph18030978 - 22 Jan 2021

Cited by 9 | Viewed by 3018

Abstract

Ten years have elapsed since the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, and the relative contribution of natural radiation is increasing in Fukushima Prefecture due to the reduced dose of artificial radiation. In order to accurately determine the effective [...] Read more.

Ten years have elapsed since the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, and the relative contribution of natural radiation is increasing in Fukushima Prefecture due to the reduced dose of artificial radiation. In order to accurately determine the effective dose of exposure to artificial radiation, it is necessary to evaluate the effective dose of natural as well as artificial components. In this study, we measured the gamma-ray pulse-height distribution over the accessible area of Namie Town, Fukushima Prefecture, and evaluated the annual effective dose of external exposure by distinguishing between natural and artificial radionuclides. The estimated median (range) of absorbed dose rates in air from artificial radionuclides as of 1 April 2020, is 133 (67–511) nGy h⁻¹ in the evacuation order cancellation zone, and 1306 (892–2081) nGy h⁻¹ in the difficult-to-return zone. The median annual effective doses of external exposures from natural and artificial radionuclides were found to be 0.19 and 0.40 mSv in the evacuation order cancellation zone, and 0.25 and 3.9 mSv in the difficult-to-return zone. The latest annual effective dose of external exposure discriminated into natural and artificial radionuclides is expected to be utilized for radiation risk communication. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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8 pages, 1800 KiB

Open AccessArticle

Radon Activity Concentrations in Natural Hot Spring Water: Dose Assessment and Health Perspective

by Eka Djatnika Nugraha, Masahiro Hosoda, June Mellawati, Untara Untara, Ilsa Rosianna, Yuki Tamakuma, Oumar Bobbo Modibo, Chutima Kranrod, Kusdiana Kusdiana and Shinji Tokonami

Int. J. Environ. Res. Public Health 2021, 18(3), 920; https://doi.org/10.3390/ijerph18030920 - 21 Jan 2021

Cited by 12 | Viewed by 3614

Abstract

The world community has long used natural hot springs for tourist and medicinal purposes. In Indonesia, the province of West Java, which is naturally surrounded by volcanoes, is the main destination for hot spring tourism. This paper is the first report on radon [...] Read more.

The world community has long used natural hot springs for tourist and medicinal purposes. In Indonesia, the province of West Java, which is naturally surrounded by volcanoes, is the main destination for hot spring tourism. This paper is the first report on radon measurements in tourism natural hot spring water in Indonesia as part of radiation protection for public health. The purpose of this paper is to study the contribution of radon doses from natural hot spring water and thereby facilitate radiation protection for public health. A total of 18 water samples were measured with an electrostatic collection type radon monitor (RAD7, Durridge Co., USA). The concentration of radon in natural hot spring water samples in the West Java region, Indonesia ranges from 0.26 to 31 Bq L⁻¹. An estimate of the annual effective dose in the natural hot spring water area ranges from 0.51 to 0.71 mSv with a mean of 0.60 mSv for workers. Meanwhile, the annual effective dose for the public ranges from 0.10 to 0.14 mSv with an average of 0.12 mSv. This value is within the range of the average committed effective dose from inhalation and terrestrial radiation for the general public, 1.7 mSv annually. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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15 pages, 3191 KiB

Open AccessArticle

Radiological Assessment of Indoor Radon and Thoron Concentrations and Indoor Radon Map of Dwellings in Mashhad, Iran

by Mohammademad Adelikhah, Amin Shahrokhi, Morteza Imani, Stanislaw Chalupnik and Tibor Kovács

Int. J. Environ. Res. Public Health 2021, 18(1), 141; https://doi.org/10.3390/ijerph18010141 - 28 Dec 2020

Cited by 34 | Viewed by 4749

Abstract

A comprehensive study was carried out to measure indoor radon/thoron concentrations in 78 dwellings and soil-gas radon in the city of Mashhad, Iran during two seasons, using two common radon monitoring devices (NRPB and RADUET). In the winter, indoor radon concentrations measured between [...] Read more.

A comprehensive study was carried out to measure indoor radon/thoron concentrations in 78 dwellings and soil-gas radon in the city of Mashhad, Iran during two seasons, using two common radon monitoring devices (NRPB and RADUET). In the winter, indoor radon concentrations measured between 75 ± 11 to 376 ± 24 Bq·m⁻³ (mean: 150 ± 19 Bq m⁻³), whereas indoor thoron concentrations ranged from below the Lower Limit of Detection (LLD) to 166 ± 10 Bq·m⁻³ (mean: 66 ± 8 Bq m⁻³), while radon and thoron concentrations in summer fell between 50 ± 11 and 305 ± 24 Bq·m⁻³ (mean 115 ± 18 Bq m⁻³) and from below the LLD to 122 ± 10 Bq m⁻³ (mean 48 ± 6 Bq·m⁻³), respectively. The annual average effective dose was estimated to be 3.7 ± 0.5 mSv yr⁻¹. The soil-gas radon concentrations fell within the range from 1.07 ± 0.28 to 8.02 ± 0.65 kBq·m⁻³ (mean 3.07 ± 1.09 kBq·m⁻³). Finally, indoor radon maps were generated by ArcGIS software over a grid of 1 × 1 km² using three different interpolation techniques. In grid cells where no data was observed, the arithmetic mean was used to predict a mean indoor radon concentration. Accordingly, inverse distance weighting (IDW) was proven to be more suitable for predicting mean indoor radon concentrations due to the lower mean absolute error (MAE) and root mean square error (RMSE). Meanwhile, the radiation health risk due to the residential exposure to radon and indoor gamma radiation exposure was also assessed. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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13 pages, 1183 KiB

Open AccessArticle

An Improved Passive CR-39-Based Direct ²²²Rn/²²⁰Rn Progeny Detector

by Jun Hu, Guosheng Yang, Chutima Kranrod, Kazuki Iwaoka, Masahiro Hosoda and Shinji Tokonami

Int. J. Environ. Res. Public Health 2020, 17(22), 8569; https://doi.org/10.3390/ijerph17228569 - 18 Nov 2020

Cited by 4 | Viewed by 2290

Abstract

An improved passive CR-39-based direct ²²²Rn/²²⁰Rn progeny detector with 3 detection channels was designed and tested in this study to measure and calculate equilibrium equivalent concentration (EEC) of both ²²²Rn and ²²⁰Rn without the equilibrium factor. A theoretical [...] Read more.

An improved passive CR-39-based direct ²²²Rn/²²⁰Rn progeny detector with 3 detection channels was designed and tested in this study to measure and calculate equilibrium equivalent concentration (EEC) of both ²²²Rn and ²²⁰Rn without the equilibrium factor. A theoretical model was established to calculate the EEC with optimization. Subsequently, an exposure experiment was carried out to test the performance of this detector, and we compared the chamber experiment and the theoretical model by estimating and measuring various parameters. The deposition flux of progeny derived from the prediction agreed well with the value measured in the exposure chamber. The energy-weighted net track density (NTD) measured by this detector is much more reliable to reflect the linear relation between NTD and time-integrated EEC. Since the detector is sensitive to the exposure environmental condition, it is recommended to apply the detector to measure the EEC after its calibration in a typical indoor environment. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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17 pages, 1152 KiB

Open AccessArticle

Total Diet Study to Assess Radioactive Cs and ⁴⁰K Levels in the Japanese Population before and after the Fukushima Daiichi Nuclear Power Plant Accident

by Hiroshi Terada, Ikuyo Iijima, Sadaaki Miyake, Kimio Isomura and Hideo Sugiyama

Int. J. Environ. Res. Public Health 2020, 17(21), 8131; https://doi.org/10.3390/ijerph17218131 - 03 Nov 2020

Cited by 3 | Viewed by 2331

Abstract

We conducted a total diet study (TDS) of ¹³⁷Cs, ¹³⁴Cs, and ⁴⁰K to assess their average dietary exposure levels in a Japanese adult population before and after the Fukushima Daiichi nuclear power plant (FDNPP) accident. Nineteen market baskets were evaluated [...] Read more.

We conducted a total diet study (TDS) of ¹³⁷Cs, ¹³⁴Cs, and ⁴⁰K to assess their average dietary exposure levels in a Japanese adult population before and after the Fukushima Daiichi nuclear power plant (FDNPP) accident. Nineteen market baskets were evaluated in 2006–2011. In each basket, a TDS sample comprising tap water and 160–170 food items, which were combined into 13 groups, were collected for analysis by gamma-ray spectrometry. From 2006 to 2010, the ¹³⁷Cs activity concentration in the “fish and shellfish” group was 0.099 Bq/kg, representing the highest value obtained, whereas the total committed effective dose (CED) of radiocesium isotopes (¹³⁷Cs + ¹³⁴Cs) was 0.69 μSv. In 2011, “milk and dairy products” from Sendai City had a Cs activity concentration of 12 Bq/kg, representing the highest values among all food groups studied. However, the annual CED of radioactive Cs in Fukushima City was 17 μSv after the FDNPP accident, which is 60-fold lower than the maximum permissible dose of 1 mSv/year. The mean CED obtained for ⁴⁰K was 180 μSv, which is comparable to the global average. Our results reveal the average dietary exposure of ¹³⁷Cs, ¹³⁴Cs, and ⁴⁰K, which can aid in estimating the radiological safety of foods. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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11 pages, 1314 KiB

Open AccessArticle

Passive-Type Radon Monitor Constructed Using a Small Container for Personal Dosimetry

by Yuki Tamakuma, Chutima Kranrod, Takahito Suzuki, Yuki Watanabe, Thamaborn Ploykrathok, Ryoju Negami, Eka Djatnika Nugraha, Kazuki Iwaoka, Mirosław Janik, Masahiro Hosoda and Shinji Tokonami

Int. J. Environ. Res. Public Health 2020, 17(16), 5660; https://doi.org/10.3390/ijerph17165660 - 05 Aug 2020

Cited by 2 | Viewed by 3211

Abstract

The International Commission on Radiological Protection (ICRP) recently recommended a new dose conversion factor for radon based on the latest epidemiological studies and dosimetric model. It is important to evaluate an inhalation dose from radon and its progeny. In the present study, a [...] Read more.

The International Commission on Radiological Protection (ICRP) recently recommended a new dose conversion factor for radon based on the latest epidemiological studies and dosimetric model. It is important to evaluate an inhalation dose from radon and its progeny. In the present study, a passive radon personal monitor was designed using a small container for storing contact lenses and its performance was evaluated. The conversion factor for radon (²²²Rn), the effect of thoron (²²⁰Rn) concentration and the air exchange rate were evaluated using the calibration chamber at Hirosaki University. The minimum and maximum detectable radon concentrations were calculated. The conversion factor was evaluated as 2.0 ± 0.3 tracks cm⁻² per kBq h m⁻³; statistical analyses of results showed no significant effect from thoron concentration. The minimum and maximum detectable radon concentrations were 92 Bq m⁻³ and 231 kBq m⁻³ for a measurement period of three months, respectively. The air exchange rate was estimated to be 0.26 ± 0.16 h⁻¹, whose effect on the measured time-integrated radon concentration was small. These results indicate that the monitor could be used as a wearable monitor for radon measurements, especially in places where radon concentrations may be relatively high, such as mines and caves. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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12 pages, 823 KiB

Open AccessFeature PaperArticle

Assessment of Radiation Dose from the Consumption of Bottled Drinking Water in Japan

by Aoife Kinahan, Masahiro Hosoda, Kevin Kelleher, Takakiyo Tsujiguchi, Naofumi Akata, Shinji Tokonami, Lorraine Currivan and Luis León Vintró

Int. J. Environ. Res. Public Health 2020, 17(14), 4992; https://doi.org/10.3390/ijerph17144992 - 11 Jul 2020

Cited by 14 | Viewed by 3589

Abstract

Activity concentrations of ²³⁴U, ²³⁵U, ²³⁸U, ²²⁶Ra, ²²⁸Ra, ²²²Rn, ²¹⁰Po, ²¹⁰Pb, ⁴⁰K, ³H, ¹⁴C, ¹³⁴Cs and ¹³⁷Cs were determined in 20 different Japanese bottled drinking water commercially available in Japan. [...] Read more.

Activity concentrations of ²³⁴U, ²³⁵U, ²³⁸U, ²²⁶Ra, ²²⁸Ra, ²²²Rn, ²¹⁰Po, ²¹⁰Pb, ⁴⁰K, ³H, ¹⁴C, ¹³⁴Cs and ¹³⁷Cs were determined in 20 different Japanese bottled drinking water commercially available in Japan. The origins of the mineral water samples were geographically distributed across different regions of Japan. Activity concentrations above detection limits were measured for the radionuclides ²³⁴U, ²³⁵U, ²³⁸U, ²²⁶Ra, ²²⁸Ra and ²¹⁰Po. An average total annual effective dose due to ingestion was estimated for adults, based on the average annual volume of bottled water consumed in Japan in 2019, reported to be 31.7 L/y per capita. The estimated dose was found to be below the recommended World Health Organisation (WHO) guidance level of 0.1 mSv/y for drinking water quality. The most significant contributor to the estimated dose was ²²⁸Ra. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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15 pages, 2338 KiB

Open AccessArticle

Observation of Dispersion in the Japanese Coastal Area of Released ⁹⁰Sr, ¹³⁴Cs, and ¹³⁷Cs from the Fukushima Daiichi Nuclear Power Plant to the Sea in 2013

by Hirofumi Tazoe, Takeyasu Yamagata, Kazuki Tsujita, Hisao Nagai, Hajime Obata, Daisuke Tsumune, Jota Kanda and Masatoshi Yamada

Int. J. Environ. Res. Public Health 2019, 16(21), 4094; https://doi.org/10.3390/ijerph16214094 - 24 Oct 2019

Cited by 16 | Viewed by 3511

Abstract

The March 2011 earthquake and tsunami resulted in significant damage to the Fukushima Daiichi Nuclear Power Plant (FDNPP) and the subsequent release of radionuclides into the ocean. Here, we investigated the spatial distribution of strontium-90 (⁹⁰Sr) and cesium-134/cesium-137 (^{134, 137} [...] Read more.

The March 2011 earthquake and tsunami resulted in significant damage to the Fukushima Daiichi Nuclear Power Plant (FDNPP) and the subsequent release of radionuclides into the ocean. Here, we investigated the spatial distribution of strontium-90 (⁹⁰Sr) and cesium-134/cesium-137 (^{134, 137}Cs) in surface seawater of the coastal region near the FDNPP. In the coastal region, ⁹⁰Sr activity was high, from 0.89 to 29.13 mBq L⁻¹, with detectable FDNPP site-derived ¹³⁴Cs. This indicated that release of ⁹⁰Sr from the power plant was ongoing even in May 2013, as was that of ¹³⁴Cs and ¹³⁷Cs. ⁹⁰Sr activities measured at open ocean sites corresponded to background derived from atmospheric nuclear weapons testing fallout. The FDNPP site-derived ⁹⁰Sr/¹³⁷Cs activity ratios in seawater were much higher than those in the direct discharge event in March 2011, in river input, and in seabed sediment; those ratios showed large variability, ranging from 0.16 to 0.64 despite a short sampling period. This FDNPP site-derived ⁹⁰Sr/¹³⁷Cs activity ratio suggests that these radionuclides were mainly derived from stagnant water in the reactor and turbine buildings of the FDNPP, while a different source with a low ⁹⁰Sr/¹³⁷Cs ratio could contribute to and produce the temporal variability of the ⁹⁰Sr/¹³⁷Cs ratio in coastal water. We estimated the release rate of ⁹⁰Sr from the power plant as 9.6 ± 6.1 GBq day⁻¹ in May 2013 on the basis of the relationship between ⁹⁰Sr and ¹³⁷Cs activity (⁹⁰Sr/¹³⁷Cs = 0.66 ± 0.05) and ¹³⁷Cs release rate. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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11 pages, 1898 KiB

Open AccessArticle

Isotope Composition and Chemical Species of Monthly Precipitation Collected at the Site of a Fusion Test Facility in Japan

by Naofumi Akata, Masahiro Tanaka, Chie Iwata, Akemi Kato, Miki Nakada, Tibor Kovács and Hideki Kakiuchi

Int. J. Environ. Res. Public Health 2019, 16(20), 3883; https://doi.org/10.3390/ijerph16203883 - 14 Oct 2019

Cited by 6 | Viewed by 2240

Abstract

The deuterium plasma experiment was started using the Large Helical Device (LHD) at the National Institute for Fusion Science (NIFS) in March 2017 to investigate high-temperature plasma physics and the hydrogen isotope effects towards the realization of fusion energy. In order to clarify [...] Read more.

The deuterium plasma experiment was started using the Large Helical Device (LHD) at the National Institute for Fusion Science (NIFS) in March 2017 to investigate high-temperature plasma physics and the hydrogen isotope effects towards the realization of fusion energy. In order to clarify any experimental impacts on precipitation, precipitation has been collected at the NIFS site since November 2013 as a means to assess the relationship between isotope composition and chemical species in precipitation containing tritium. The tritium concentration ranged from 0.10 to 0.61 Bq L⁻¹ and was high in spring and low in summer. The stable isotope composition and the chemical species were unchanged before and after the deuterium plasma experiment. Additionally, the tritium concentration after starting the deuterium plasma experiment was within three sigma of the average tritium concentration before the deuterium plasma experiment. These results suggested that there was no impact by tritium on the environment surrounding the fusion test facility. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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11 pages, 1026 KiB

Open AccessArticle

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

by Masahiko Matsuo, Yasuyuki Taira, Makiko Orita, Yumiko Yamada, Juichi Ide, Shunichi Yamashita and Noboru Takamura

Int. J. Environ. Res. Public Health 2019, 16(9), 1481; https://doi.org/10.3390/ijerph16091481 - 26 Apr 2019

Cited by 16 | Viewed by 3542

Abstract

On 1 April 2017, six years have passed since the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, and the Japanese government declared that some residents who lived in Tomioka Town, Fukushima Prefecture could return to their homes. We evaluated environmental contamination and radiation [...] Read more.

On 1 April 2017, six years have passed since the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, and the Japanese government declared that some residents who lived in Tomioka Town, Fukushima Prefecture could return to their homes. We evaluated environmental contamination and radiation exposure dose rates due to artificial radionuclides in the livelihood zone of residents (living space such as housing sites), including a restricted area located within a 10-km radius from the FDNPS, immediately after residents had returned home in Tomioka town. In areas where the evacuation orders had been lifted, the median air dose rates were 0.20 μSv/h indoors and 0.26 μSv/h outdoors, and the radiation exposure dose rate was 1.6 mSv/y. By contrast, in the “difficult-to-return zone,” the median air dose rate was 2.3 μSv/h (20 mSv/y) outdoors. Moreover, the dose-forming artificial radionuclides (radiocesium) in the surface soil were 0.018 μSv/h (0.17 mSv/y) in the evacuation order-lifted areas and 0.73 μSv/h (6.4 mSv/y) in the difficult-to-return zone. These findings indicate that current concentrations of artificial radionuclides in soil samples have been decreasing in the evacuation order-lifted areas of Tomioka town; however, a significant external exposure risk still exists in the difficult-to-return zone. The case of Tomioka town is expected to be the first reconstruction model including the difficult-to-return zone. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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19 pages, 2891 KiB

Open AccessFeature PaperReview

Characteristics of Thoron (²²⁰Rn) and Its Progeny in the Indoor Environment

by Shinji Tokonami

Int. J. Environ. Res. Public Health 2020, 17(23), 8769; https://doi.org/10.3390/ijerph17238769 - 25 Nov 2020

Cited by 35 | Viewed by 3657

Abstract

The present paper outlines characteristics of thoron and its progeny in the indoor environment. Since the half-life of thoron (²²⁰Rn) is very short (55.6 s), its behavior is quite different from the isotope radon (²²²Rn, half-life 3.8 days) in [...] Read more.

The present paper outlines characteristics of thoron and its progeny in the indoor environment. Since the half-life of thoron (²²⁰Rn) is very short (55.6 s), its behavior is quite different from the isotope radon (²²²Rn, half-life 3.8 days) in the environment. Analyses of radon and lung cancer risk have revealed a clearly positive relationship in epidemiological studies among miners and residents. However, there is no epidemiological evidence for thoron exposure causing lung cancer risk. In contrast to this, a dosimetric approach has been approved in the International Commission on Radiological Protection (ICRP) Publication 137, from which new dose conversion factors for radon and thoron progenies can be obtained. They are given as 16.8 and 107 nSv (Bq m⁻³ h)⁻¹, respectively. It implies that even a small quantity of thoron progeny will induce higher radiation exposure compared to radon. Thus, an interest in thoron exposure is increasing among the relevant scientific communities. As measurement technologies for thoron and its progeny have been developed, they are now readily available. This paper reviews measurement technologies, activity levels, dosimetry and resulting doses. Although thoron has been underestimated in the past, recent findings have revealed that reassessment of risks due to radon exposure may need to take the presence of thoron and its progeny into account. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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9 pages, 1050 KiB

Open AccessBrief Report

Study of Well Waters from High-Level Natural Radiation Areas in Northern Vietnam

by Van-Hao Duong, Thanh-Duong Nguyen, Miklos Hegedus, Erika Kocsis and Tibor Kovacs

Int. J. Environ. Res. Public Health 2021, 18(2), 469; https://doi.org/10.3390/ijerph18020469 - 08 Jan 2021

Cited by 8 | Viewed by 2193

Abstract

The determination of natural radionuclide concentrations plays an important role for assuring public health and in the estimation of the radiological hazards. This is especially true for high level radiation areas. In this study, ²²⁶Ra, ²²⁸Ra and ²³⁸U concentrations were [...] Read more.

The determination of natural radionuclide concentrations plays an important role for assuring public health and in the estimation of the radiological hazards. This is especially true for high level radiation areas. In this study, ²²⁶Ra, ²²⁸Ra and ²³⁸U concentrations were measured in well waters surrounding eight of the high-level natural radiation areas in northern Vietnam. The ²²⁶Ra, ²²⁸Ra and ²³⁸U activity concentrations vary from <1.2 × 10⁻³–2.7 (0.46), <2.6 × 10⁻³–0.43 (0.07) and <38 × 10⁻³–5.32 Bq/L (0.50 of median), respectively. ²²⁶Ra and ²³⁸U isotopes in most areas are in equilibrium, except for the DT-Thai Nguyen area. The calculated radiological hazard indices are generally higher than WHO (World Health Organization) recommendations. Average annual effective dose and excess lifetime cancer risk values due to drinking well water range from to 130 to 540 μSv/year and 7.4 × 10⁻⁶ to 3.1 × 10⁻⁵, respectively. Full article

(This article belongs to the Special Issue Assessment of Environmental Radioactivity and Radiation for Human Health Risk)

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