Assessment and estimation of the effective dose due to external exposure from natural radioactivity of sands used in civil construction in the state of Rio de Janeiro,Brazil

The presence of naturally occurring radioactivity in sand and other building materials results in indoor and outdoor exposure to the public. Sand is one of the main components in civil construction alongside cement, crushed stone and bricks. Thus, this research was carried out in twenty sand samples with the objective of investigating the hazard indices of natural radiation, due to the presence of 238U, 226Ra, 232Th and 40K in sand samples collected in some locations in the state of Rio de Janeiro (Brazil), analyzing by gamma spectrometry and using an HPGe detector. The technique used for gamma analysis was gamma spectrometry, and the software used to analyze peaks and obtain counts was LabSOCS. In this context, the average activity concentration values of 226Ra (66.7 ± 1.2) and 40K (647 ± 31) Bq kg-1 are higher than the world mean activity concentration of 50, 50 and 500 Bq kg-1 for these three radionuclides. However, the value of 232Th (40.6 ± 0.7) Bq kg-1 and Raeq (175 ± 5) Bq kg-1 are less than the world average of 50 Bq kg-1 and 370 Bq kg-1, respectively. The estimation of the average values for Annual Effective Dose (0.51 ± 0.01) and Dutch Radiation Performance Index (0.52 ± 0.01) was carried out, with values below the maximum recommended limit for the public. Only one sample had a higher value and the other samples are within the levels required for environmental control. However, the mean values found in this present study, when compared to those of other authors mentioned here, showed higher values. Therefore, most samples have safe values to be used by people in building their homes.

Characteristics of 210Po in Asian overbite clam (Potamocorbula laevis) from the coastal area at Thai Binh province, Vietnam

210Po concentration in the edible muscle tissue and digestive diverticulum organs of Asian overbite clam at the near-shore Thai Binh, Vietnam was analyzed using alpha detectors. The 210Po activity in muscle tissue and digestive diverticulum organs ranged from 5 ± 1 to 178 ± 10 and from 118 ± 7 to 812 ± 12 Bq.kg-1 with the average value of 25 and 324 Bq.kg-1, respectively. Results showed that 210Po activity in the digestive diverticulum was significantly higher than in the muscle tissue. There was a slightly inverse correlation between 210Po activity in muscle tissue, digestive diverticulum, and clam weight and size. The annual committed effective dose was calculated from 210Po due to the consumption of Asian overbite clam for adults in the study area was higher than the guideline value of 0.2 - 1 mSv.y-1.

An assessment of committed effective dose and lifetime cancer risk due to the ingestion of infant milk

Infant milk is a manufactured food designed for feeding babies and infants under 12 months of age. This product is indicated when, for some reason, the baby can not be fed by breast milk. It is used in case of intolerance to milk from farmed animals and is widely used for the nutrition of newborns in artificial lactation, in place of breastfeeding. It can be used as a complete or partial substitute for human milk. In the current study, the committed effective dose and lifetime cancer risk due to ingestion of ⁴ K, ²²⁶Ra, and ²²⁸Ra were estimated using activity concentration obtained from high-resolution gamma spectrometry. Consumption data and dose coefficients were obtained from Brazilian Institute of Geography and Statistics and data published by ICRP 119. Infant milk and water samples were collected in the Rio de Janeiro trade, placed in a polystyrene container, and then sealed to reach the secular radioactive equilibrium condition (at least 45 days). The samples were analyzed by gamma spectrometry using a High Purity Germanium (HPGE). Detection efficiency for each sample was obtained with LabSOCS software. For infant milk samples, the highest values of activity concentrations were (242 ± 9) Bq.kg^-1 for ⁴ K, (5 ± 1) Bq.kg^-1 for ²²⁸Ra and presented values below the detection limit for ²²⁶Ra. The higher values obtained for water samples were (10 ± 1) Bq.l^-1, (5 ± 1) Bq.l^-1, (5.3 ± 0.1) Bq.l^-1 for ⁴ K, ²²⁶Ra and ²²⁸Ra, respectively. These values of committed effective dose are below the values stipulated by UNSCEAR (290 μSv.y^-1) and by the ICRP (1 mSv.y^-1). The values obtained for lifetime cancer risk are considered negligible, once they are below the limit considered for taking action (10^-4). It can be concluded that the values calculated do not present a significant risk regarding the intake of infant milk in the first two years of the child's life.

Distribution, annual committed effective dose, and health safety assessment of 210Po in marine biota from Kalpakkam coast, Bay of Bengal

Seafood, intertidal biota, beach sediment, and seawater from Kalpakkam coast, Bay of Bengal were analyzed for ²¹⁰Po to evaluate the internal exposure and other radiological safety aspects. Kalpakkam houses various nuclear power generation facilities on its coast. The activity concentration of ²¹⁰Po was more pronounced in the intertidal organisms. Pelagic planktivorous fishes have the highest activity of the non-technogenic radionuclide, followed by the detrital feeders, benthic planktivores, benthic carnivores, and pelagic carnivore fishes. The affinity of ²¹⁰Po to organic detrital matter and planktonic organisms has led to a higher accumulation of radionuclide in planktivorous fishes. Activity concentration of ²¹⁰Po in seafood ranged between 1.13 ± 0.3 and 96.71 ± 1.6 Bq kg^-1 (Becquerel/kilogram). In seaweeds and gastropods, it ranged from 2.09 ± 0.2 to 8.21 ± 0.6 and from 9.31 ± 0.7 to 21.58 ± 1.2 Bq kg^-1, respectively. The committed effective dose (CED) of ²¹⁰Po in seafood varied from 31.18 to 456.68 μSv yr^-1 (microSievert/year). Radiological hazard parameters, such as activity intake, CED in consumption, of the seafood from this coast are within the acceptable levels prescribed by the International Commission on Radiological Protection and US Environmental Protection Agency.

Radiological evaluation of Ra-226, Ra-228 and K-40 in tea samples: A comparative study of effective dose and cancer risk

Activity concentrations of tea samples were determined using high resolution gamma spectrometry.The values ranged from (421.00 ± 17.00) to (732.00 ± 30.00) Bq.kg ^-1 for K-40 and from (3.00 ± 0.80) to (27.00 ± 3.00) Bq.kg^-1 for Ra-228. The values for Ra-226 were below 27.00 Bq.kg^-1. The committed effective dose was estimated at 4.74-78.89 μSv.y^-1 for adults and 13.55-445.84 μSv.y^-1 for children. The cancer risk was higher for females. However, results showed that the tea consumption do not represent a radiological health risk to the population.

Assessment of the committed effective dose due to the 210Po intake from fish consumption for the Arabian Gulf population

This study aims to assess the committed effective dose due to the intake of ²¹⁰Po from the consumption of fish in Arabian Gulf countries. Twenty different kinds of fish, which represent the most common fish species consumed in the Arabian Gulf countries, were analyzed using alpha spectrometer technique. ²¹⁰Po activity concentrations in fish samples were found to vary over a wide range from 0.1 to 14.7 Bq kg^-1 fresh weight. This variation of ²¹⁰Po concentrations between various type of fish samples might be attributed to the feeding type pattern and the size of fish. The annual committed effective dose due to ingestion of ²¹⁰Po in fish species for adults in the Arabian Gulf countries was estimated and found to vary from 38 μSv in Bahrain to 85 μSv in Oman with an average value of 59 μSv. These values are considered relatively high compared to those reported in some other regions. However, it is still much lower than the world average ingestion dose due to natural radiation sources.

Tertiary evaluation of the committed effective dose of emergency workers that responded to the Fukushima Daiichi NPP accident

In January 2014, Tokyo Electric Power Company (TEPCO) learned that the committed effective dose (CED) for nine emergency workers at the Fukushima Daiichi Nuclear Power Plant accident had been assessed by a method other than the standard assessment methods, established by the Ministry of Health, Labour and Welfare (MHLW) in a secondary evaluation conducted in July 2013. The MHLW requested that the TEPCO and primary contractors review all CED data for 6,245 workers who engaged in emergency work in March and April 2011 except those previously reviewed in the 2013 secondary evaluation. This tertiary evaluation revealed that the recorded CED for 1,536 workers had more than 0.1 mSv discrepancy with the CED evaluated by the standard method. The MHLW requested that TEPCO and primary contractors revise CED data for 142 workers whose CED was 2 mSv or greater that required a CED revision of 1 mSv or greater. The average CED revision was 5.86 mSv. The revised effective dose ranged from 2.17-180.10 mSv. In addition, the number of workers whose CED exceeded 100 mSv increased by one. New issues addressed during the tertiary evaluation included the following: (a) setting of calibration coefficients to convert the CED value from whole body counters equipped with NaI scintillator (WBC(NaI)) to a CED value from WBCs with Ge semiconductor detector; (b) estimation methods for the cases where ¹³¹I was not detectable by WBC (NaI) and where ¹³⁷Cs was not detectable but ¹³⁴Cs was detected; (c) effects of stable iodine (KI) tablets to block the uptake of ¹³¹I by thyroid gland; and (d) complications in determining additional doses during stand-by in the seismically isolated building. To prevent the future use of non-uniform CED assessment methods in the dose assessment for workers, the MHLW issued administrative guidance documents to TEPCO and primary contractors on March 25, 2014.

Evaluation of radionuclides transfer from soil-to-edible flora and estimation of radiological dose to the Malaysian populace

Malaysia, a rapidly growing industrial country, is susceptible to pollution via large-scale industrial engagements and associated human activities. One particular concern is the potential impact upon the quality of locally resourced vegetables, foodstuffs that contain important nutrients necessary for good health, forming an essential part of the Malaysian diet. As a part of this, it is of importance for there to be accurate knowledge of radioactive material uptake in these vegetables, not least in respect of any public health detriment. Herein, using HPGe γ-ray spectrometry, quantification has been performed of naturally occurring radionuclides in common edible vegetables and their associated soils. From samples analyses, the soil activity concentration ranges (in units of Bq/kg) for (226)Ra, (232)Th and (40)K were respectively 1.33-30.90, 0.48-26.80, 7.99-136.5 while in vegetable samples the ranges were 0.64-3.80, 0.21-6.91, 85.53-463.8. Using the corresponding activities, the transfer factors (TFs) from soil-to-vegetables were estimated, the transfers being greatest for (40)K, an expected outcome given the essentiality of this element in support of vigorous growth. The TFs of (226)Ra and (232)Th were found to be in accord with available literature data, the values indicating the mobility of these radionuclides to be low in the studied soils. Committed effective dose and the associated life-time cancer risk was estimated, being found to be below the permissible limit proposed by UNSCEAR. Results for the studied media show that the prevalent activities and mobilities pose no significant threat to human health, the edible vegetables being safe for consumption.

Assessment of committed effective dose due to the ingestion of (210)Po and (210)Pb in consumed Lebanese fish affected by a phosphate fertilizer plant

Ingestion of radionuclides through seafood intake is a one of the sources contributing to the internal effective dose in the human organism. In order to evaluate the internal exposure and potential risks due to (210)Po and (210)Pb associated with fish consumption, these radionuclides were measured in commonly consumed fish species from a clean area and an area subjected to the impact of a Lebanese phosphate fertilizer plant. The highest concentration of (210)Pb was 98.7 Bq/kg fresh weight while (210)Po activity concentrations varied from 3.6 Bq/kg to 140 Bq/kg. A supplementary radiation exposure was detected; the highest committed effective dose due to (210)Po and (210)Pb was found to be 1110 μSv/y and 450 μSv/y, respectively. Moreover, the average mortality and morbidity risks due to the fish consuming were estimated.

The radium legacy: Contaminated land and the committed effective dose from the ingestion of radium contaminated materials

The manufacture and use of radium in the early to mid-20th century within industrial, medicinal and recreational products have resulted in a large number of contaminated sites across a number of countries with notable examples in the USA and Europe. These sites, represent a significant number of unregulated sources of potential radiological exposure that have collectively and hitherto not been well characterised. In 2007, the Radioactive Contaminated Land (RCL) Regulations came into force in the UK, providing the statutory guidance for regulators to classify and deal with RCL. Here we report on results derived from digestion experiments to estimate committed effective dose, a key aspect of the RCL Regulations, from the ingestion of radium contaminated sources that can be found in the environment. This case study includes particles, clinker and artefacts that arise from past military activities on a site that was once an airfield at Dalgety Bay on the Firth of Forth, UK. Since 2011 the number of radium contaminated finds has increased by one order of magnitude on the foreshore areas of Dalgety Bay. The increase in finds may in large part be attributed to a change in monitoring practice. A subsample of sixty sources was selected, on the basis of their activity and dimensions, and subjected to digestion in simulated stomach and lower intestine solutions. The study demonstrated that more radium-226 ((226)Ra) and lead-210 ((210)Pb; driven by Polonium solubility) are dissolved from sources in artificial 'stomach' solutions compared with 'lower intestine' solutions. The combined 'gut' solubility for (226)Ra and apparent (210)Pb varied from less than 1% to up to 35% ICRP 72 conversion factors were used to convert the activities measured in solution to committed effective dose. A little over 10% of the sources tested dissolved sufficient radioactivity to result in 100mSv committed effective dose to an infant. Using the solubility of 35% as a worst case, minimum source activities necessary to deliver 100mSv to the full age range of users of the foreshore were estimated. All the estimated activities have been detected and recovered through routine monitoring.