UNSCEAR Research Articles

An extended assessment of natural radioactivity in the sediments of the mid-region of the Egyptian Red Sea coast

In this study, nearly 84 marine sediment samples were collected from twelve points in four cities (Quseir, Safaga, Hurghada, and Ras Gharib) along the Egyptian Red Sea sectors. The collected samples were extensively examined to estimate the natural radioactivity level. The obtained results were compared to the reported ranges from other locations in different countries. Hazardous radiation parameters such as radium equivalent, annual dose, and external hazards were estimated and compared to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) recommended levels. The values were recorded in the first natural radioactivity database of coastal sediments from Egyptian Red Sea cities. The dose rate for certain organs was evaluated. The results showed that Red Sea beach sediments are safe in terms of natural radioactivity. It can be concluded that they do not pose a risk to tourists going to the beaches for recreation or to sailors and fishers involved in economic activities along the Egyptian Red Sea coast.

Lung cancer risk and effective dose coefficients for radon: UNSCEAR review and ICRP conclusions

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has provided a detailed and authoritative update of its reviews of the epidemiology and dosimetry of radon and progeny. Lifetime risk of lung cancer calculated using data for several miner cohorts were 2.4–7.5 × 10−4 per working level month (WLM) of radon-222 progeny exposure for a mixed male/female population and 3.0–9.6 × 10−4 per WLM for a male population. Dosimetric models gave mean values of effective dose coefficients from radon-222 progeny of 12 mSv per WLM for mines, 16 mSv per WLM for indoor workplaces and 11 mSv per WLM for homes. The lifetime risk coefficient used by the International Commission on Radiological Protection (ICRP) is 5 × 10−4 per WLM and it has recently recommended an effective dose coefficient for radon-222 and progeny of 3 mSv per mJ h m−3 (about 10 mSv per WLM) for most circumstances of exposure. The ICRP risk and dose coefficients are supported by the UNSCEAR review and provide a clear and firm basis for current international advice and standards for protection from radon. Notwithstanding this evidence and the ICRP advice, UNSCEAR will continue to use a lower value of effective dose coefficient of 5.7 mSv per WLM for assessments of population exposures.

The importance of trustworthy sources of scientific information in risk communication with the public.

ABSTRACTIn the event of a nuclear accident or radiological emergency, effective communication with the public on radiation risks is important in order to contain and rein in damage to physical and mental health, and social and economic consequences. The purpose of this paper is to summarize features of trustworthy sources of scientific information, and to convey their importance in radiation risk communication by recalling other aspects influencing the effectiveness of that communication. This will draw on key references in the literature, augmented with some experience and insight gleaned from a professional career of more than 35 years at the national and international level, including contributing to the International Atomic Energy Agency’s (IAEA) work on the consequences of the Chernobyl accident (1990–1995), heading its incident and emergency centre (1996–2005), and as the secretary (2005–2018) of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which conducts scientific reviews on the levels and effects of radiation exposure. The paper highlights the necessity of sound science and trustworthy sources, and recapitulates the main elements needed both to ensure solid conclusions on radiation epidemiology and to foster trust. The paper concludes that, while sound science and trustworthy sources are necessary, they are in themselves to a greater or lesser degree insufficient to ensure fully effective risk communication. Some of the major problems in communicating this science are highlighted to help others charged with preparing for and conducting this onerous task in the future.

Is the 28-Day Rule Safe for Use in Abdominal Radiography?

Introduction: The 28-day rule is utilized as a precautionary measure for irradiating the fetus at an early stage of conception for abdominal and pelvic radiography. There is a probability of the women being pregnant if the 28-day rule is applied for this examination and thus irradiating the conceptus. It is difficult to convince people that low radiation doses during early pregnancy will not cause any harm to the conceptus. As such this study was to ascertain whether the 28-day rule can be used safely for abdominal radiography in women of reproductive age. Material and Methods: The experimental study was conducted at the Radiography Laboratory, International Islamic University Malaysia, Kuantan using an anthropomorphic PBU-50 phantom. The entrance surface dose (ESD), organ dose and effective dose (ED) were estimated using CALDose_X 5.0 software, based on the exposure parameters and tube output of the x-ray unit. Results: The mean ESD for AP abdominal radiographic examination of 3.162 mGy is within that recommended by radiation protection regulatory bodies. Additionally, the mean organ dose of 0.468 mGy is lower than the threshold value of 100 mSv for the “all-or-none” phenomenon to happen. Further, the mean ED of 0.73 mSv is within the recommendation of the International Atomic Energy Agency (IAEA) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Conclusion: This study indicated that the 28-day rule is safe to be used for abdominal radiography for a woman of reproductive age.

The presence of radioactive heavy minerals in prospecting trenches and concomitant occupational exposure.

Uranium, perhaps the most strategically important component of heavy minerals, finds particular significance in the nuclear industry. In prospecting trenches, the radioactivity of 238U and 232Th provides a good signature of the presence of heavy minerals. In the work herein, the activity concentrations of several key primordial radionuclides (238U, 232Th, and 40K) were measured in prospecting trenches (each of the latter being of approximately the same geometry and physical situation). All of these are located in the Seila area of the South Eastern desert of Egypt. A recently introduced industry standard, the portable hand-held RS-230 BGO gamma-ray spectrometer (1024 channels) was employed in the study. Based on the measured data, the trenches were classified as either non-regulated (U activity less than 1000 Bq kg-1) or regulated (with 238U activity more than 1000 Bq kg-1). Several radiological hazard parameters were calculated, statistical analysis also being performed to examine correlations between the origins of the radionuclides and their influence on the calculated values. While the radioactivity and hazard parameters exceed United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) guided limits, the mean annual effective doses of 0.49 and 1.4 mSv y-1 in non-regulated and regulated trenches respectively remain well below the International Commission on Radiological Protection (ICRP) recommended 20 mSv/y maximum occupational limit. This investigation reveals that the studied area contains high uranium content, suitable for extraction of U-minerals for use in the nuclear fuel cycle.

Radionuclides Transfer from Soil to Tea Leaves and Estimation of Committed Effective Dose to the Bangladesh Populace.

Considering the probable health risks due to radioactivity input via drinking tea, the concentrations of 226Ra, 232Th,40K and 137Cs radionuclides in the soil and the corresponding tea leaves of a large tea plantation were measured using high purity germanium (HPGe) γ-ray spectrometry. Different layers of soil and fresh tea leaf samples were collected from the Udalia Tea Estate (UTE) in the Fatickchari area of Chittagong, Bangladesh. The mean concentrations (in Bq/kg) of radionuclides in the studied soil samples were found to be 34 ± 9 to 45 ± 3 for 226Ra, 50 ± 13 to 63 ± 5 for 232Th, 245 ± 30 to 635 ± 35 for 40K and 3 ± 1 to 10 ± 1 for 137Cs, while the respective values in the corresponding tea leaf samples were 3.6 ± 0.7 to 5.7 ± 1.0, 2.4 ± 0.5 to 5.8 ± 0.9, 132 ± 25 to 258 ± 29 and <0.4. The mean transfer factors for 226Ra, 232Th and 40K from soil to tea leaves were calculated to be 0.12, 0.08 and 0.46, respectively, the complete range being 1.1 × 10−2 to 1.0, in accordance with IAEA values. Additionally, the most popularly consumed tea brands available in the Bangladeshi market were also analyzed and, with the exception of 40K, were found to have similar concentrations to the fresh tea leaves collected from the UTE. The committed effective dose via the consumption of tea was estimated to be low in comparison with the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reference ingestion dose limit of 290 μSv/y. Current indicative tea consumption of 4 g/day/person shows an insignificant radiological risk to public health, while cumulative dietary exposures may not be entirely negligible, because the UNSCEAR reference dose limit is derived from total dietary exposures. This study suggests a periodic monitoring of radiation levels in tea leaves in seeking to ensure the safety of human health.

Determine the Contaminations of Radon in the Drinking Water Using NTDs (CR-39) and RAD7 Detectors

This presented study was performed to determine the contaminations of radon in twenty-five drinking tap water samples in Penang/Malaysia. The concentration of 222Rn, specific activity of 226Ra, radon emanation factor, equilibrium radon concentration, annual effective dose and mass exhalation rate were measured in drinking water samples available under study by using two methods, passive method (NTDs (CR-39) and active method (RAD7 monitoring). Also, the pH and electrical conductivity of the samples were measured. The results showed that the maximum concentration of radon was found in sample 7 to be 98.154 Bq m−3 and the minimum concentration of radon was found in sample 4 to be 39.715 Bq m−3 with an average of 66.521 Bq m−3. The maximum concentration of radium was found in sample 7 to be 1266.036 × 10−3 Bq kg−1, and the minimum concentration of radium was found in sample 4 to be 530.729 × 10−3 Bq kg−1 with an average (899.999 × 10−3 Bq kg−1). The results obtained from the passive technique (CR-39) and active technique (RAD7) were in good agreement together (66.521, 63.533) Bq m−3, because the passive method and active method are simple and reliable analytical methods. An average annual effective dose (0.770 mSvy−1) was found to be below the value (3–10 mSvy−1) that was reported by the ICRP (1993), therefore, there is no evidence of health problems. Significant strong positive correlations found (r = 1, Pearson Correlation, p < 0.000) in concentrations of radon, radium and annual effective dose. All the results obtained were within the international levels as given by UNSCEAR (United Nations Scientific Committee on the Effect of Atomic Radiation).

Radionuclides Contamination in Soil: Effects, Sources and Spatial Distribution

Radionuclide concentrations in the soil depend on the geological and anthropogenic activities of an area. They influence level of gamma radiation in the environment, which can cause significant health risk in humans. Due to the non-uniform distribution of radionuclides in the soil, various measurement methods have been adopted to monitor our environment. The challenges involved in collecting environmental samples, duration, technicality and cost of measurement have led to various models for predicting unmeasured locations. This article presents geostatistical method using kriging techniques, which adopt the theory of regionalized variables, to characterize the spatial distribution of radionuclide in un-sampled locations using data obtained from sampled locations. Among other things, this paper presents results of application of this method to a study area. Spatial distribution of radionuclides reveal the non-uniform distribution in the study area. Though the radionuclides level in the study area are below global average set by United Nations Scientific Committee on the Effects of atomic Radiation (UNSCEAR), the spatial distribution map can be used to provide adequate information needed by regulatory authorities in identifying the contaminated area in need of remediation.

Eye Lens Doses Received by Radiation Workers in Interventional Medical Procedures

The International Commission on Radiological Protection (ICRP) has recently recommended that the occupational dose limit for the eye lens be reduced to 20 mSv per year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv. ICRP clearly states that the recommendations are chiefly based on epidemiological evidence that suggested the eye lens dose threshold for cataract induction revised downwards from 2-5 Gy to about 0.5 Gy. Interventional medical workers are at greater health risk from radiation exposure to eyes as a result of the procedures they undertake than most other medical specialists. An extensive study has been carried out to measure the eye lens doses received by 373 interventional medical radiation workers in twelve large hospitals in Indonesia. Measurements were made using Thermo Scientific Harshaw thermoluminescence dosimeter (TLD) chip (size 3.2 mm × 3.2 mm × 0.15 mm) put inside an EYE-D holder placed in the worker’s temple. The procedures performed are grouped based on classification made by the UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation). The results showed that in general the measured data are in an agreement with some published data, even though a large range of doses was observed. The highest mean eye lens dose of 0.2378 mSv per procedure was received by interventionists who worked in the abdominal interventions procedure. Overall, from the results of measurement, it can be concluded that most interventionists might receive eye lens dose exceeding the dose limit if the procedures are carried out on daily basis, and the abdominal interventions procedures were found to be the ones that give the highest risk to the eye lens of workers as it delivered the highest dose to this particular organ. 14.00 Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";}

Radiological safety assessment of mined Trona commonly consumed in Nigeria

ABSTRACT Mined Trona is a naturally occurring inorganic salt that is consumed by humans for diverse purposes in Nigeria. Due to the increase in consumption rates of these salts following a renewed government interest in solid minerals exploration and exploitation, it is imperative to assay its radiological content. Reconnaissance survey revealed that the most commonly used Trona varieties were: Farar Kanwa, Jan Kanwa, Dan Libya, Ngurnu, Manda, Farar Balma, Jar Balma and Yar Agadez. Samples of the identified Trona varieties were purchased from markets within Zaria, Nigeria. The samples were analysed using NaI (Tl) gamma ray spectrometry system. Radium equivalent activity (Raeq), annual effective dose (AED), Internal and Alpha hazard Indices (Hin and Iα) and total cancer risks (TCR) were used to assess the radiological safety of its consumption. The activity concentration of 238U (226Ra); 232Th and 40K varied widely and had an average ± error values of 42.904 ± 4.54 Bq/kg, 11.96 ± 1.41 Bq/kg and 455.28 ± 10.56 Bq/kg respectively. Raeq, AED, Iα, Hin and TCR were estimated at 95.07 ± 63.10 Bq/kg, 68.52 ± 52.53µSv/y, 0.21 ± 0.23, 0.37 ± 0.27 and (390.57 ± 299.44) × 10 − 06 respectively; which were by far less than the US EPA and UN SCEAR acceptable thresholds. It was established that the threshold consumption rate is 40 Kg/year and any value slightly higher than the threshold values will be associated with a significant radiological health risk. Therefore, at the present consumption rate of Trona in Nigeria, there is no cause for radiological concern.

Activity Concentrations of Sr-90 and Cs-137 in Seawater and Sediment in the Gulf of Tonkin, Vietnam

In this study, we measured the activity concentrations of Cs-137 and Sr-90 in surface seawater and surface sediments at the Tra Co, Bach Long Vi, and Ky Anh locations in the Gulf of Tonkin, Vietnam, from December 2018 to October 2019. The average activity at the selected locations was 1.22, 1.43, and 1.33 Bq/m3 for Cs-137 and 0.88, 1.17, and 1.09 Bq/m3 for Sr-90 in surface seawater samples and 0.74, 1.01, and 0.81 Bq/kg dry for Cs-137 and 0.49, 0.49, and 0.43 Bq/kg dry for Sr-90 in sediment samples. The ratio of the average activity concentration (Cs-137/Sr-90) in the surface seawater was 1.42, 1.22, and 1.22 at the Tra Co, Bach Long Vi, and Ky Anh locations, respectively. These are somewhat low compared to the global ratios (1.6 and 1.8). Meanwhile, Cs-137/Sr-90 ratios in the sediment samples at the selected locations were 1.51, 2.06, and 1.88, respectively, which is equal to or greater than the corresponding value for global sedimentation according to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Correlations between Sr-90, Cs-137, and organic carbon content were detected in this study. The results showed that Cs-137 has a high correlation with the organic carbon content in sediment, while Sr-90 has a low correlation.

Radiological safety of groundwater around a uranium mine in Namibia

Uranium mining activities produce the main element used in nuclear energy production. However, it can also negatively affect the environment including groundwater by release of residues or effluent containing radioactive elements. The study investigated the concentration and radiological hazard of uranium in groundwater and seepage water from the tailings of a uranium mine in Namibia. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to assess the concentration of uranium in the groundwater and seepage water and the radiological hazards were determined. The radiological hazard indices Radium equivalent activity (Raeq), Absorbed dose (D), Annual Effective Dose equivalent (AEDE), External hazard index (Hex) and Internal hazard index (Hin) were determined and compared to limits recommended by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The calculated average value of D and Hin of groundwater is 108.11nGyh−1 and 1.26, respectively and are above the UNSCEAR values (55 nGyh−1 and 1). Further, the average values of Raeq, AEDE and Hex were below the recommended values. The isotopic ratio of uranium radionuclides in groundwater indicates that the uranium in the sampled groundwater is below 1 suggesting it is not natural uranium present but a possible contamination from the mine seepage. The radiological hazard parameters of the seepage water were above the recommended values and thus pose a radiation risk to human and environment.

Radionuclide Potential of Holocene Sediments in the West of Marmara Sea (Turkey)

Radionuclides that cause radioactive pollution descend to the bottom in marine and water environments such as heavy metals and accumulate in bottom sediments. It is useful to determine the radionuclides in these environments in order to control the damage that accumulated radionuclides can cause to the environment. Radioactive pollution can harm people directly or through the food chain. In this study, natural and artificial radionuclide values were measured in current sediment samples taken from the seabed in the western part of the Marmara Sea. Gamma spectrometry method was used in radionuclide examinations. In gamma spectrometry studies of sediments, values of radionuclid (40K, 137Cs, 226Ra, 54Mn, 95Z and 232Th) were determined. Sea depths where 18 analyzed sea floor sediments are taken vary between 15-50 m. The determined radionuclide concentration activity values of the study area are 137Cs (0.9 - 9.4 (Bq / kg)), 232Th (18.9 - 86 (Bq / kg)), 226Ra (10 - 50 (Bq / kg)), 40K (24.4 - 670 (Bq / kg)), 54Mn (0.71-0.9 (Bq / kg)) and 95Zr (0.18 - 0.19 (Bq / kg)). These values were correlated with the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The 226Ra series, 232Th series and 40K radionuclides accumulate naturally and their concentrations increase gradually due to anthropogenic impurities. 226Ra values obtained across the study areas are within normal limits according to UNSCEAR values. 40K and 232Th values were higher than UNSCEAR values in all locations. The presence of 137Cs (0.9 - 9.4 (Bq / kg) from almost all locations reveals the presence of a risky situation in terms of ambient conditions. Because this element cannot be found in the natural environment and can be found artificially as an end of radioactivity.

Dust and Radon Levels on the West Coast of Namibia – what did we learn?

Abstract The study investigated the potential for adverse health impacts from exposures to inhalable atmospheric dust and radon in the main towns along Namibia's central-western coast. An ambient air quality monitoring network was established at the end of 2016 to measure and track the inhalable dust (specifically PM10) and radon concentrations. Data collected between November 2016 and the end of December 2018 were assessed and selected PM10 samples were analysed for mineral and radionuclide content. In addition, emissions from anthropogenic sources were quantified and simulated using a regional dispersion model. Episodic dust storms associated with easterly winds are a common phenomenon during the winter months in the western part of Namibia. During such events, dust is transported over long distances westwards towards and well into the Atlantic Ocean. In view of the natural and anthropogenic nature of atmospheric dust, the study differentiated between sources of natural dust and those arising as a result of man-made processes. It was found that PM10 concentrations were, on average, higher at the coastal monitoring stations than at the stations located further inland, often exceeding the daily World Health Organisation (WHO) guideline value. Whilst high atmospheric dust concentrations were mostly associated with easterly wind conditions, sea salt was found to be a significant PM10 contributor at the coastal stations. Modelled results, which only included emissions from man-made sources, indicated that these sources contribute very little to the total PM10 concentrations measured at the coastal towns. The radiation exposure doses associated with the inhalation of atmospheric dust and radon were found to be well-below the world-wide average inhalation doses provided by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR).

Dust and radon levels on the west coast of Namibia – What did we learn?

The study investigated the potential for adverse health impacts from exposures to inhalable atmospheric dust and radon in the main towns along Namibia's central-western coast. An ambient air quality monitoring network was established at the end of 2016 to measure and track the inhalable dust (specifically PM10) and radon concentrations. Data collected between November 2016 and the end of December 2018 were assessed and selected PM10 samples were analysed for mineral and radionuclide content. In addition, emissions from anthropogenic sources were quantified and simulated using a regional dispersion model.Episodic dust storms associated with easterly winds are a common phenomenon during the winter months in the western part of Namibia. During such events, dust is transported over long distances westwards towards and well into the Atlantic Ocean. In view of the natural and anthropogenic nature of atmospheric dust, the study differentiated between sources of natural dust and those arising as a result of man-made processes.It was found that PM10 concentrations were, on average, higher at the coastal monitoring stations than at the stations located further inland, often exceeding the daily World Health Organisation (WHO) guideline value. Whilst high atmospheric dust concentrations were mostly associated with easterly wind conditions, sea salt was found to be a significant PM10 contributor at the coastal stations. Modelled results, which only included emissions from man-made sources, indicated that these sources contribute very little to the total PM10 concentrations measured at the coastal towns.The radiation exposure doses associated with the inhalation of atmospheric dust and radon were found to be well-below the world-wide average inhalation doses provided by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR).

RADIOLOGICAL EVALUATION OF THE CONCENTRATION AND IMPACT OF OIL AND GAS ACTIVITIES IN ERUEMUKOHWARIEN AREA OF SOUTHERN NIGERIA

The study was carried out in-situ using a Radalert 100 nuclear radiation monitor and a geographical positioning system (GPS). Five facilities were investigated at the rig site which included the rig site host community as well as the camp site for the oil workers at Ekapkamreh town. Ten 10 sampling locations were evaluated at a total of 60 study points. The values obtained range between 0.115±0.018 (µSv/hr) and 0.299±0.040 (µSv/hr) for the rig site environment, 0.111±0.006 (µSv/hr) and 0.337±0.031 (µSv/hr) for field logistic base (offices and workshops), 0.114±0.011 (µSv/hr) and 0.312±0.021 (µSv/hr) for components of the mud circulation section. Also, the radiological concentration of the Chemical Store ranged between 0.126±0.019 (µSv/hr) and 1.181±0.104 (µSv/hr), while the radiological values obtained from other facilities within the rig site ranged from 0.155±0.026 (µSv/hr) and 0.249±0.026 (µSv/hr). Radiation readings obtained for soil ranged from 0.149±0.05 (µSv/hr) to 0.219±0.025 (µSv/hr) and 0.114±0.039 (µSv/hr) to 0.219±0.051 (µSv/hr) respectively at the host community and camp site. Most of the results obtained showed that the general environment of the rig site is slightly above the permissible absorbed dose rate threshold of 0.15(µSv/hr) recommended by the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in 2009. However, the exposure rates exceed the standard background level of 13µR/hr (coequal to 0.13µSv/hr). There is high tendency for the industry workers to be exposed to radiation with time.

The Activity Concentration of Radionuclides (226Ra, 232Th and 40K) in Soil Samples and Associated Health Hazards in Natore, Kushtia and Pabna District of Bangladesh

The study has been carried out to measure the activity concentration of natural and anthropogenic radionuclides in fifteen(15) soil samples of Natore, Kushtia and Pabna district, which are around the 30 km peripheral area of Rooppur Nuclear Power Plant, by gamma ray spectrometry system using a High Purity Germanium (HPGe) detector. It is found that the activity concentration of 226Ra, in the collected sample was from 3.52 Bq/kg to 28.5 Bq/kg with the average value of 12.42 Bq/kg. For 232Th, the range was from 4.18 Bq/kg to 34.5 Bq/kg with the average value of 12.6 Bq/kg. Finally, the activity concentration of 40K, in the collected sample was in the range of 84 Bq/kg to 345 Bq/kg, and the average value was 198.9 Bq/kg. The absorbed dose rate (D) was found to be in the range of 4.59 nGy/h to 40.93 nGy/h with the mean value 21.3 nGy/h. The annual effective dose (E) was in the range of 0.006 mSv/yr to 0.152 mSv/yr with an average of 0.033 mSv/yr. The radium equivalent activity was in the range from 10.02 Bq/kg to 89 Bq/kg with an average of 44.99 Bq/kg. The external hazard index (Hex) was found to be in the range of 0.027 to 0.242 with the mean value of 0.121 and the internal hazard index (Hin) was found to be in the range of 0.044 to 0.302 with the mean value of 0.156. All the values are much below the recommended limit by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), 35 Bq/kg for 226Ra, 30 Bq/kg for 232Th and 400 Bq/kg for 40K. According to international and national regulation, the annual dose to members of the public, 1 mSvy-1 and Hex &amp; Hin must be lower than unity. Moreover, no artificial radioactivity was found in the soil samples of this study area. This research concludes that the found values are within the permissible limits as required by the Nuclear Safety and Radiation Control(NSRC) Rules-1997 of Bangladesh and International Atomic Energy Agency(IAEA) Safety Standards- General Safety Requirements (GSR): Part-3.&#x0D; Journal of Bangladesh Academy of Sciences, Vol. 43, No. 2, 169-180, 2019

Absorbed radiation doses in the thyroid as estimated by UNSCEAR and subsequent risk of childhood thyroid cancer following the Great East Japan Earthquake.

The identification of thyroid cancers among children after the Chernobyl nuclear power plant accident propelled concerns regarding long-term radiation effects on thyroid cancer in children affected by the Fukushima Daiichi nuclear power plant accident in Fukushima, Japan. Herein we consider the potential association between absorbed dose in the thyroid and the risk of developing thyroid cancer as detected by ultrasonography on 300 473 children and adolescents aged 0–18 years in Fukushima. The absorbed dose mentioned in the present study indicates the sum of that from external exposure and that from internally deposited radionuclides. We grouped participants according to estimated absorbed doses in each of 59 municipalities in Fukushima Prefecture, based on The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2013 report. The 59 municipalities were assigned to quartiles by dose. We limited our analyses to participants aged ≥6 years because only one case of thyroid cancer was observed in participants aged ≤5 years; 164 299 participants were included in the final analysis. Compared with the lowest dose quartile, the age- and sex-adjusted rate ratios (95% confidence intervals) for the low-middle, high-middle and highest quartiles were 2.00 (0.84–4.80), 1.34 (0.50–3.59) and 1.42 (0.55–3.67) for the 6–14-year-old groups and 1.99 (0.70–5.70), 0.54 (0.13–2.31) and 0.51 (0.12–2.15) for the >15-year-old group, respectively. No dose-dependent pattern emerged from the geographical distribution of absorbed doses by municipality, as estimated by UNSCEAR, and the detection of thyroid cancer among participants within 4–6 years after the accident. Ongoing surveillance might further clarify the effects of low-dose radiation exposure on thyroid cancer in Fukushima.

RADON IN THE WATER

Man and his environment are constantly exposed to the effects of ionizing radiation. Most of this radiation comes from natural and artificial radionuclides and the biggest radioecological problem is the 222Rn radioactive gas. Natural radioactivity comes from unstable radioisotopes that were present during the formation of the Earth, and are present today. According to the research by UNSCEAR(United Nations Scientific Committee on the Effects of Atomic Radiation) it is estimated that the radiation dose, which comes from natural radionuclides and to which man is exposed, is 2.4 mSv per year. Natural sources of radioactivity are cosmic radiation and Earth’s crust that contains primordial radioactive elements including those that are sources of radon (uranium). Radon is a natural inert radioactive gas without smell and taste. It is soluble in water and can easily diffuse with the gaseous and aqueous phase and in this way forms significant concentrations. The techniques and methods most commonly used to detect and determine the activities of radon in water are alpha spectrometry, gamma spectrometry and measurement techniques on a liquid scintillation detector. Throughout epidemiological studies, the World Health Organization has provided convincing evidence of the correlation of exposure to indoor radon and the development of lung cancer. Radon and its decomposition products are considered to be the second cause of lung cancer after consuming tobacco.

Estimation of internal dose from tap water after the Fukushima Daiichi Nuclear Power Station accident using newly obtained data.

Massive release of radioactive materials into the atmosphere occurred due to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in March 2011. The World Health Organization (WHO) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported the results of dose estimation to assess the health effect of the accident and both reports state that their assessments of internal and external exposure doses contain certain uncertainties due to uncertainties inherent to the basic data. Therefore, estimation of the internal dose from tap water was conducted in this study by utilizing a database of deposition calculated by an atmospheric transfer, dispersion and deposition model (ATDM) in conjunction with the newly obtained data on the volume of daily water intake obtained by a web-based survey. The median mean and 95-percentile of thyroid equivalent doses were estimated for 1-year and 10-year children and adults in 12 municipalities in the evacuation area in Fukushima prefecture. The present mean thyroid dose estimations for 1-year children (0.4–16.2 mSv) are smaller than the corresponding values in the UNSCEAR 2013 report (1.9–49 mGy). Dose-modifying factors in the Japanese or local community are discussed.