Outdoor Annual Effective Dose Research Articles

Activity Concentration of Natural Radionuclides in Surface Sediments of Major River Watersheds in Korea and Assessment of Radiological Hazards

The assessment of potential radiation hazards in accumulated sediments in aquatic ecosystems is vital for the management and disposal of sediments. Furthermore, preemptive management of radionuclides in terrestrial ecosystems is critical for marine ecosystem conservation. We analyzed the activity concentrations of natural radionuclides (226Ra,232Th, 238U, and 40K) in the surface sediments of major river watersheds in Korea and evaluated the radiation hazards stemming from these activity concentrations. The mean activity concentrations of 226Ra and 238U were lower than the global average, whereas those of 232Th and 40K were higher. The mean values of radium equivalent activity, external hazard index, and internal hazard index calculated from these activity concentrations did not exceed the recommended maximum values. The mean values of absorbed gamma dose rate in air and annual outdoor effective dose rate (AEDRout) were higher than the global average by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) but remarkably lower than the recommended and background values by the International Commission on Radiological Protection (ICRP) and the Korea Institute of Nuclear Safety (KINS). The contribution of 40K and 232Th to the AEDRout mean value was predominant. In conclusion, the surface sediments of major river watersheds in Korea are associated with negligible radiation hazards. These findings provide fundamental data for the management and treatment of sediments in terrestrial and marine ecosystems.

Determination of natural radioactivity levels in soil samples from irrigated vegetable farming land in and around Addis Ababa, Ethiopia.

Soil samples were collected from vegetable agricultural areas in and around Addis Ababa, and their levels of radioactivity were measured. Gamma spectrometry with high-purity germanium detector was used to quantify radioactivity level. The average concentration of 226Ra, 232Th, and 40K were 32.8±2.1, 62.4±4.4, and 544.3±23.3Bqkg-1 respectively. The mean values of 232Th and 40K are higher, whereas the value of 226Ra is comparable with world average values. Radiological hazard indices, including radium equivalent activity (Raeq), absorbed dose rate (Dr), outdoor annual effective dose equivalent (Deff), external hazard index (Hex), internal hazard index (Hin), and gamma radiation representative level index (Iγ), were calculated based on the activity concentration of 226Ra, 232Th and 40K. The mean values were 163.9Bqkg-1, 78.7 nGy h-1, 0.10mSv y-1, 0.44, 0.53, and 0.60 respectively. All indices are lower than global recommended limit values. These results revealed that radiation hazard due to radionuclides in the soil of the study area is insignificant.

Ambient gamma radiation level around Kaveri river basin, Karnataka state, India.

Studies on ambient gamma radiation in indoor and outdoor environment and their effect on human health have created interest among the researchers across the world. The present study represents the results of indoor and outdoor ambient gamma dose rates around the Kaveri river basin from Talakaveri (Madikeri district) to Mekedatu (Ramanagara district) by using portable Environmental Radiation Dosemeter. The annual effective dose in the present study area varies between 0.14mSv.y-1 and 0.58mSv.y-1 with an average value of 0.30mSv.y-1 for indoor radiation. The outdoor annual effective dose ranged between 0.01mSv.y-1 and 0.14mSv.y-1 with an average value of 0.06mSv.y-1. The total annual effective dose varies from 0.17 to 0.72mSv.y-1 with an average value of 0.36mSv.y-1. The calculated values of indoor and outdoor annual effective dose in the study area (are found to be lower than the world average values (1mSv.y-1 and 0.48mSv.y-1).

On transfer factors of natural radionuclides and radiological health risks assessment of some fruit samples

Abstract In this study, the activity concentration of artificial and natural radionuclides such as 137Cs, 40K, 226Ra, and 232Th was measured in the soil under the roots; leaves; and fruits of six different fruit trees namely mulberry, fig, apricot, olive, black and white grapes in Koya district, Erbil province, Iraq. For this purpose, a high-resolution gamma spectroscopy consisting of a high-purity germanium (HPGe) detector was used. In addition, the associated radiological risks from soil and fruits were assessed by calculating several radiological indices such as radium equivalent (Raeq.s), absorbed dose (Ds), indoor (AEDEs indoor ) and outdoor annual effective doses (AEDEs outdoor ), internal and external hazard indices, gamma index and the excess lifetime cancer risk (ELRCs). The results show that consuming these fruits is radiologically safe because they can cause an annual effective dose of about 61.72 μSv y−1 and excess lifetime cancer risk of 0.06 × 10−3 Sv y−1. On the other hand, transfer factors of radionuclides from soil to leaves; and from soil to fruits were studied. The transfer factor analysis revealed that among the studied fruits and radionuclides, apricot and mulberry exhibited the highest transfer factors for 40K, with values of 1.85 and 1.87, respectively.

Gamma ray spectrometric analysis and assessment of radiation hazards in soils of Mbeere North region, Kenya.

This study used gamma ray spectrometry to determine the radiological safety of construction soil sampled randomly from Mbeere North region, Kenya. The mean activity concentration of 232Th, 238U, and 40K was 149.7±2.8 Bqkg-1, 88.3±2.4 Bqkg-1, and 490±35 Bqkg-1, respectively. These averages exceed the world average for all the radionuclides. The radionuclides were non-uniformly distributed, with higher concentrations along the slopes and on the feet of the hills. The mean absorbed dose rate, indoor and outdoor annual effective dose, radium equivalent, external hazard index, and internal hazard index were 157.9±4.4 nGh-1, 0.58±0.02 mSvy-1, 0.39±0.01 mSvy-1, 340.7±9.2 Bqkg-1, 0.92±0.02 and 1.14±0.03, respectively. Among the radiation safety indicators, only the average internal hazard index exceeded slightly the acceptable safe limit. Therefore, soils of Mbeere North region are radiologically safe for use in brick making and construction of human habitats.

Estimation of Radiation Dose in Building Materials Used In Federal University Gusau Using Gamma-Ray Spectroscopy Analysis

This study estimated the radiation dose in building materials (sand, cement, and granite) in Federal University Gusau, Zamfara State, Nigeria, through gamma-ray spectrometry system using a Sodium Iodide Thallium activated "NaITl" detector in a low background configuration. The range of the average activity concentration of 226Ra was found to be 56.65±0.75Bqkg-1 to 159.45±2.68Bqkg-1, which was higher than that of the world mean value for soil 35Bqkg-1,for 232Th the range was 46.65±0.45Bqkg-1 to 79.32±1.68Bqkg-1, all the samples, were found to be higher than that of the world mean for soil 30Bqkg-1. While the activity concentrations of 232Th levels of blocks, granite, and sand samples are all above the world range, except the cement which was within the worldwide range 194.84±1.31Bqkg-1 to 656.84±0.76Bqkg-1. The average activity concentration of 40K for cement, sand, and blocks was within the worldwide range, with granite samples slightly higher than the world mean value for soil 400Bqkg-1. The results have been compared with the world mean values of 35, 30, and 400Bqkg-1 specified by the UNSCEAR (2016). Concerning radiological risk to human health, the absorbed gamma dose rate (D) was estimated to be above the world average range of 55nGyh-1; the outdoor annual effective dose equivalent (AEDE) were, estimated to be below the permissible limit of 0.07mSvy-1. The values of Raeq, Hex, and Hin for all the samples in the present work are lower than the accepted safety limit value of 370Bqkg-1 and below the limit of unity, respectively.

Gamma-radiation levels along the main Karakorum thrust area of Northern Pakistan

Abstract In this contribution, the distribution of naturally occurring radionuclides in the area around Main Karakoram Thrust (MKT) in Karakoram Range, North Pakistan is documented. Three natural radionuclides (226Ra, 232Th, and 40K) and one anthropogenic radionuclide (137Cs) were studied for their specific activities in 30 samples. The measurements were made by high resolution gamma-ray spectrometry. The sampling area is located in Gilgit Baltistan province of Pakistan at an altitude of 1838 m/6030 ft above sea level. MKT separates the Karakoram plate from the Kohistan-Ladakh Terranes and Indian Plate to the south. The specific activity varied as 4.5–56.5 Bq kg−1, 18.2–61.4 Bq kg−1, 1.4–19.6 Bq kg−1 and 51–1640 Bq kg−1 for 226Ra, 232Th, 137Cs and 40K, respectively. The average radium equivalent activity was 127.8 ± 45.9 Bq kg−1. The external hazard index was <1 for all samples and representative level index was <1 for majority of the samples. The average air absorbed dose rate was 60.9 ± 23.2 nGy h−1 corresponding to the outdoor effective dose rate of 73.7 ± 28.0 μSv y−1. These values were slightly higher than the world average values for air absorbed dose rate (51 nGy h−1) and outdoor annual effective dose rate (70 μSv y−1). The data revealed significant positive correlation between 226Ra and 40K. Principal component analysis revealed distribution patterns within the samples and identified three distinct groups. Data was also evaluated for the concentrations of uranium, thorium and potassium and their ratios.

Radiological risk assessment of beaches from volcanic oceanic islands: A case study of the Eastern Canary Islands (Spain)

This work constitutes the first survey that allows the establishment of baseline levels of environmental radioactivity in beach sands from the volcanic oceanic islands of La Graciosa, Lanzarote, Fuerteventura and Gran Canaria. Activity concentration values of 226Ra, 232Th and 40K were measured by gamma spectroscopy in 108 samples, collected from 39 beaches across the whole study region. The radiological hazard risks associated with these sands were studied. The mean absorbed dose rate in the study region was 20 nGy h−1, which is below the world average value. The mean outdoor annual effective dose for the beaches studied was 0.025 mSv y−1, which is within the internationally accepted safe limit. Additionally, the assessment of the radium equivalent showed that all samples from the Eastern Canary Islands are below the safe limit of 370 Bq kg−1. Despite not posing any radiological risk to the human population, the radiological hazard indices obtained in Gran Canaria were significantly higher than those of other islands. These significant differences seem to be related to the presence of sediments in the beaches of Gran Canaria that have their origin in lithologies with higher activity concentration values of 226Ra, 232Th and 40K that are not present in the rest of the islands.

Measurement of radioactivity in soils of Karamjal and Harbaria mangrove forest of Sundarbans for establishment of radiological database.

This work presents the first in-depth study of soil radioactivity in the mangrove forest of Bangladesh part of the Sundarbans. It used HPGe gamma-ray spectrometry to measure the amount of natural radioactivity in soil samples from Karamjal and Harbaria sites of the world's largest mangrove forest. The activity concentrations of most of the 226Ra (14±2 Bqkg-1 to 35±4 Bqkg-1) and 232Th (30±5 Bqkg-1 to 50±9 Bqkg-1) lie within the world average values, but the 40K concentration (370± 44 Bqkg-1 to 660±72 Bqkg-1) was found to have exceeded the world average value. The evaluation of radiological hazard parameters revealed that the outdoor absorbed dose rate (maximum 73.25 nGyh-1) and outdoor annual effective dose (maximum 0.09 mSvy-1) for most samples exceeded the corresponding world average values. The elevated concentration of 40K is mainly due to the salinity intrusion, usage of fertilizers and agricultural runoff, and migration of waste effluents along the riverbanks. Being the pioneering comprehensive research on the Bangladesh side of the Sundarbans, this study forms a baseline radioactivity for the Sundarbans before the commissioning of the Rooppur Nuclear Power Plant in Bangladesh.

Geochemical distributions of natural radionuclides in surface soils and sediments impacted by lead-zinc mining activity

This study investigated the distribution features of uranium-238 (238U), radium-226 (226Ra), thorium-232 (232Th), and potassium-40 (40K) and evaluated the associated environmental radiological hazards of the topsoil and river sediments in the Jinding lead-zinc (Pb-Zn) mine catchment from Southwest China. The activity concentrations of 238U, 226Ra, 232Th, and 40K ranged from 24.0 ± 2.29–60.3 ± 5.26 Bq.kg-1, from 32.5 ± 3.95–69.8 ± 3.39 Bq.kg-1, from 15.3 ± 2.24–58.3 ± 4.92 Bq.kg-1, and from 203 ± 10.2–1140 ± 27.4 Bq.kg-1, respectively. The highest activity concentrations for all these radionuclides were primarily found in the mining areas and decreased with increasing distance from the mining sites. The radiological hazard indices, including radium equivalent activity, absorbed gamma dose rate in the air, outdoor annual effective dose equivalent, annual gonadal dose equivalent, and excess lifetime cancer, revealed that the highest values were observed in the mining area and downstream, specifically in the vicinity of the ore body. These elevated values exceeded the global mean value but remained below the threshold value, suggesting that routine protection measures for Pb-Zn miners during production activities are sufficient. The correlation analysis and cluster analysis revealed strong associations between radionuclides such as 238U, 226Ra, and 232Th, indicating a common source of these radionuclides. The activity ratios of 226Ra/238U, 226Ra/232Th, and 238U/40K varied with distance, suggesting the influence of geological processes and lithological composition on their transport and accumulation. In the mining catchment areas, the variations in these activity ratios increased indicated the impact of limestone material dilution on the levels of 232Th, 40K, and 238U in the upstream region. Moreover, the presence of sulfide minerals in the mining soils contributed to the enrichment of 226Ra and the removal of 238U caused those activity ratios decreased in the mining areas. Therefore, in the Jinding PbZn deposit, the patterns of mining activities and surface runoff processes in the catchment area favored the accumulation of 232Th and 226Ra over 40K and 238U. This study provides the first case study on the geochemical distributions of natural radionuclides in a typical Mississippi Valley-type PbZn mining area and offers fundamental information on radionuclide migration and baseline radiometric data for PbZn deposits worldwide.

Assessment of radiation hazard indices due to naturally occurring long-life radionuclides in the coastal area of Barra de Valizas, Uruguay.

The Uruguayan east coast has several mineral resources, which include black sand ores in the Barra de Valizas-Aguas Dulces area. Cancer in Uruguay shows non-homogeneous geographical distribution, with the highest standardized mortality ratio (SMR) in the northeast and east region, which includes the aforementioned area and the town of Barra de Valizas. The activity concentration of natural radionuclides (226Ra, 232Th and 40K) in Barra de Valizas´soil was determined by gamma spectrometry in order to evaluate the radiological hazard for inhabitants and tourists. The outdoor annual effective dose (AEDE), excess lifetime cancer risk (ELCR), and annual gonadal dose equivalent (AGDE) were evaluated for inhabitants with a life expectancy of 77.7years, a 0.2 and 0.5 occupancy factor, and using the conversion coefficients recommended by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The annual effective dose was also evaluated for both summer and fortnight tourists. The radiological hazard indices for Barra de Valizas inhabitants are higher than the worldwide mean and recommended values. This may contribute to Rocha's higher SRM value, although a direct correlation cannot be assured with the epidemiological information currently available. Social, medical and anthropological studies will be carried out in future to provide data and verify this correlation.

Radon concentration and radiation hazard of a rare earth waste dump in China

The 222Rn activity concentration and air absorbed dose rate of a rare earth waste slag heap in China were measured by radon and air absorbed dose rate instruments. A total of 34 monitoring points including waste residue heaps were selected. The 222Rn activity concentration and absorbed dose rate measurement ranges are 51.0–246.9 Bq/m3 and 0.071–0.110 ​μGy/h. Other radiation hazard indicators: outdoor annual effective dose (Eout), annual effective dose from radon (Eradon)), excess lifetime cancer risk for outdoor (ELCRout), excess lifetime cancer risk for radon (ELCRradon), and excess lifetime cancer risk for total (ELCRtot) were calculated. They were 0.087–0.135 ​mSv/y, 0.409–1.640 mSv/y, 0.305–0.472 ​× ​10−3, 1.577–6.314 ​× ​10−3, and 1.959–6.787 ​× ​10−3. The results show that the radiation hazard indicators at all monitoring sites were within the international level. The annual effective dose at 33 monitoring sites in the human activity areas was lower than 1 mSv/y recommended by ICRP for public exposure. Data obtained in this study can be used to treat waste residue heaps and develop and utilize surrounding areas.

ASSESSMENT OF NATURAL RADIOACTIVITY LEVEL AND ASSOCIATED RADIOLOGICAL HAZARDS IN MARINE SEDIMENT SAMPLES COLLECTED FROM ABYAN BEACH, GULF OF ADEN, YEMEN

Twenty three marine sediment samples taken from the side beach from the Abyan beach, Aden Gulf, Yemen to measuring the activity concentration of terrestrial radionuclides radium-226, thorium-232 and potassium-40 and its associated hazard indices using gamma spectrometer with High-Purity Germanium HPGe detector. The average activity concentration of natural radionuclides 226Ra, 232Th and 40k in marine sediments samples under investigation were 16.25± 0.63Bqkg-1, for Ra-226, 23.80± 1.46Bqkg-1 for Th-232 and 518.54±44.61Bqkg-1 for K-40 respectively. The radiation hazard indices which resulting from the presence of natural radionuclides in marine sediment samples were calculated and the obtained results indicate that the average value of radium equivalent activity was 90.21Bqkg-1. The average value of External hazard index Hex was 0.243 and the average values of internal hazard index Hin was 0.287. The average value of outdoor absorbed dose rate Dout was 43.66nGyh−1 and indoor absorbed dose rate Din was 83.13nGyh−1. The average values of annual outdoor effective dose AEDout was 0.053mSvy-1and the annual indoor effective dose AEDin was 0.407mSvy-1. The average values of the annual gonadal dose equivalent AGDE were 312.52μSvy-1. While the average values of outdoor excess life-time cancer risk ELCRout was 0.187×10−3 and the indoor excess life-time cancer risk ELCRin was 1.427×10−3. They are less than worldwide limits.

Measurements of natural radioactivity and evaluation of radiation hazard indices in soils around the Manyoni uranium deposit in Tanzania

Pre-mining natural radioactivity levels in soils over a 27.96 km2 site around the Manyoni Uranium Project in Tanzania were determined by a high purity germanium detector. The mean activity concentrations of 226Ra, 232Th, and 40K in soils were 227.43 ± 38.79 Bq/kg, 65.22 ± 3.70 Bq/kg, and 107.32 ± 23.07 Bq/kg, respectively. The average radium equivalent activity (Raeq), external hazard index (Hex), and internal hazard index (Hin) at these concentrations were 328.95 Bq/kg, 0.89, and 1.50, respectively. The mean absorbed dose rate in air at 1 m above the ground (Da) was 148.94 nGy/h, and the mean outdoor annual effective dose (Ed) was 0.18 mSv/y. Additionally, natural radioactivity levels in soils over a 0.71 km2 site, which is inside the 27.96 km2 site, which is prone to mine dust pollution above healthy levels, were also determined. The mean activity concentrations of 226Ra, 232Th, and 40K in the soils from this site were 380.4 ± 59.93 Bq/kg, 78.69 ± 8.99 Bq/kg, and 70.40 ± 7.91 Bq/kg, respectively. The corresponding means for Raeq, Hex, and Hin were 498.35 Bq/kg, 1.35, and 2.37, respectively. The mean Da and Ed were 226.21 nGy/h and 0.28 mSv/y, respectively. The average values of Ed at both sites were less than the public exposure limit of 1 mSv/y. This means that the sites have normal background radiation levels that do not endanger people's health when they engage in outdoor activities. When mining begins, the natural radioactivity levels obtained in this study, rather than national or global averages, can be used by mine owners or government agencies to assess the environmental effects of mining. Even after mining and during decommissioning, these baseline levels can also be used to measure how well the land has been restored.

Assessment of health risks related to natural radioactivity near the Ife iron and steel industry in Ile-Ife, Nigeria

The environmental risks connected to the operations of Ife Iron and Steel Nigeria Limited, Ile-Ife, located in Osun State, are examined in this paper. According to reports, the soot and other particles the company's operations release are bad for the locals' health and threaten their sources of income. In order to calculate the absorbed dose, external hazard index, and annual effective dose for the estimation of the potential biological risk/damage to the community, the radionuclides present in soil taken from the area around the industry have been identified and their activity concentrations measured. Gamma ray spectrometry with a NaI detector was used to identify the radionuclides and determine the activity content in soil samples taken from the Fashina community. The absorbed dose rates due to the terrestrial gamma rays at 1.0m above the ground in the study area are in the range of 28.85 nGy/h to 37.05 nGy/h with an average of 33.30 nGy/h which is lower than the world average value of 59 nGy/h. The external hazard index ranges from 0.167 to 0.220 with an average of 0.194 which is less than 1.0. The outdoor annual effective doses are in the range of 0.035 mSv/y to 0.045 mSv/y with an average value of 0.041 mSv/y which is lower compared with the world average value of 0.07 mSv/y. The results show that the annual effective dose from natural radioactivity around the industry has an average value lower than the natural world recommended value.

Radiological mapping of tin mining areas in Doguwa, Kano State, Nigeria

This paper presents an extensive radiological mapping of the Doguwa tin mining areas of Kano, Nigeria, where uranium has been found in quantities for commercial mining. The goal of this study is to provide detailed radiological information that could be used as a reference in monitoring any future environmental changes that may result from other natural or artificial activities in the area. A total of 701 gamma dose rate in situ measurements were taken covering the study area using a portable NaI (Ti) scintillation detector (identiFINDER® 2). The measured terrestrial gamma dose rate varied between 38 and 958 nGy/hr with a mean value of 202 nGy/hr which is 3 times higher than the reported world average value of 59 nGy/hr by the United Nations Scientific Committee on the Effect of Atomic Radiation. The results varied significantly in accordance to the magnitude of the mining activities from one location to another. A radiological map of the study area was plotted using an ArcGIS software. The calculated values of the mean indoor, outdoor annual effective dose, and excess life cancer risk for the adult members of the public in the study area are 1 mSv/y, 0.25 mSv/y and 4.38 × 10−3 respectively. The findings in this study could be used for a proper radiation protection plan for the area.

Activity Level of 238U, 232Th, 40K and Resultant Dose Rates in Soil and Some Commonly Cultivated Vegetables

This present study aims to determine the level of natural radionuclides of 40K, 238U and 232Th in soil samples and (Potato, Solanum tuberosum and Carrot, Daucus carota) samples and vegetables (Tomato, Solanum hycopersicum and Eggplant Solanum melongena) in Al- Mada'in district 30 km south east of Baghdad, Iraq. High purity germanium (HPGe) detector was used for measurement. The transfer factors, annual absorbed dose rate and the annual effective dose in the samples collected were determined. The results showed that the mean level of measured natural radionuclides were 362.6 ± 41.6 Bqkg-1, 184.7 ± 17.4 Bqkg-1, 191.9 ± 13.5 Bqkg-1, 120.3 ± 10.6 Bqkg-1 and 126.1 ± 11.7 Bqkg-1 for 40K; 19.67 ± 2.00 Bqkg-1, 4.70 ± 0.609 Bqkg-1, 5.43 ± 0.977 Bqkg-1, 3.30 ± 0.460 Bqkg-1 and 2.40 ± 0.701 Bqkg-1 for 238U and 12.34 ± 4.12 Bqkg-1, 3.77 ± 0.904 Bqkg-1, 4.54 ± 0.709 Bqkg-1, 3.51 ± 0.721 and 3.81 ± 0.796 Bqkg-1 for 232Th to soil, tomato, eggplant, potato and carrot samples respectively. The soil-to-tomato transfer factors were found to be 0.512, 0.242 and 0.344 for 40K, 238U and 232Th and soil-to-eggplant transfer factors were found to be 0.534, 0.279 and 0.408 for 40K, 238U and 232Th respectively. The soil-to-potato transfer factors were found to be 0.336, 0.170 and 0.320 for 40K, 238U and 232Th while the soil-to-carrot transfer factors were found to be 0.348, 0.122 and 0.309 for 40K, 238U and 232Th respectively. The mean absorbed dose rate was 30.0 ± 0.57 nGyh-1 and the mean annual outdoor effective dose was 55.2 mSvy-1. This present study's annual effective dose report was 91.6% of the world average value of 70.0 msvy-1 and 87.3% of Thi-Qar government, south Iraq state value of 39.9 msvy-1.

ASSESSMENT OF ANNUAL EFFECTIVE DOSE OF GAMMA RADIATION IN VISAKHAPATNAM, ANDHRA PRADESH STATE, INDIA

The living creatures on the earth are continuously exposed to radiation from extraterrestrial and terrestrial sources. These sources are caused to the ambient gamma dose rates which affect the dwellers. This study reveals the results of observations for a while about the dose in both indoor and outdoor atmospheres. The measurements were done in 17 locations in the Visakhapatnam district, Andhra Pradesh. The PM-1405 ambient radiation dosimeter was used to make these measurements, which is a portable detector based on the Geiger Muller counter. Annual effective dose (AED) was estimated using a standard method based on the measured average absorbed dose rates. The measured indoor absorbed dose rates in Visakhapatnam district 2021–June, ranged between 0.19±0.02 to 0.32±0.07 μSv.h-1, and the measured outdoor absorbed dose rates ranged from 0.15 ± 0.01 to 0.28±0.06 μSv.h-1 and the mean of indoor and outdoor measurements being 0.26±0.04 to 0.22±0.03 μSv.h-1 respectively. The indoor AED ranged between 0.93 to 1.57 mSv.y- 1 and the outdoor AED ranged from 0.18 to 0.34 mSv.y-1 with average values of 1.3 mSv.y-1 and 0.27 mSv.y-1 respectively. In the year 2018 – June, the indoor and outdoor absorbed dose rates, measurements ranged from 0.18±0.01 to 0.34±0.06 μSv.h-1 and 0.16 ± 0.02 to 0.31±0.06 μSv.h-1 and the mean values being 0.26±0.03 to 0.21±0.03 μSv.h-1. The indoor and outdoor AED ranged from 0.88 to 1.67 mSv.y-1 and 0.2 to 0.38 mSv.y-1 with average values of 1.28 mSv.y-1 and 0.26 mSv.y-1 respectively for the year 2018, External exposure to terrestrial radiation for members of the public should not exceed an effective dose of roughly 0.48 mSv per year, as recommended by the UNSCEAR 2000 report. As a result, it may be assumed that the general population faces signicant radiological hazards from terrestrial radiation caused by the natural radionuclides in the area.

Radiological risks from 40K, 226Ra and 232Th in urbanised and industrialised karstic coastal area (Kaštela Bay, Croatia).

Radiological risks associated with 40K, 226Ra and 232Th massic activities in limestones, marls, stream sediments and soils of the Kaštela Bay (Croatia) coastal area were assessed by calculating outdoor absorbed dose rates in air (D), annual outdoor effective dose rates (Def), radium equivalent activities (Raeq) and external hazard indices (Hex). Radionuclides relative contributions to D and Hex were determined for all four types of samples as well as their total contribution to Hex in all samples. D, Def, Raeq and Hex were the lowest in limestones and the highest in soils. Maximum Raeq and Hex in soil were below the recommended values of 370Bq/kg and 1.0. No adverse radiological effects were determined in the researched area. The most important contribution to D and Hex in limestones was almost exclusively from 226Ra, in marls from 40K, in stream sediments from 226Ra and in soils from 232Th. The most significant total contribution to Hex in all samples came from 226Ra and 232Th, and the lowest came from 40K. 226Ra showed the largest variability of its total contribution to Hex, with tendency to higher values. Special attention should be given to 226Ra when studying radiological risks in typical karstic areas, irrespectively of other possible influences of geological background.

Estimation of Cosmic Effect on Background Nuclear Radiation

The effect of cosmos on background nuclear radiation has been estimated with altitude on Idanre hill using the rad scanner model 500VBR. Five readings were taken in order to ensure accuracy and reliability of the result. The mean absorbed dose rate in air for ground, middle and top of the hill were estimated to be 322.67±35.80, 353.72±37.79 and 457.88 ± 40.30 nGy h-1 respectively. The absorbed dose rate and the effective dose equivalent increases with height which is an indication of nuclear radiation enhancement by the cosmos. The mean outdoor annual effective dose equivalent was obtained as 0.40±0.05, 0.43±0.08 and 0.56±0.06 mSv y-1 respectively. The mean absorbed dose rate and the mean outdoor annual effective dose equivalent from different heights are higher than the world average of 59 nGy h-1 r and 0.07 mSv y-1 respectively and the World Health Organization recommendation of 0.1 mSv y-1, but lower than the International Commission on Radiological Protection recommendation of 1.0 mSv y-1. The estimated excess lifetime cancer risk 1.83 x10-3 is higher than the world average value of 2.9 x 10-4. This implies a highly significant radiation health risk in the area most predominantly as the height increases and the cosmic effect heightened up. Keywords: Cosmos; Background nuclear radiation; Rad scanner; Effective dose; Cancer risk.