Radioactivity in building materials used in and around Dhaka city

Fractionation of environmental radioactivity in road dust from a megacity: external and internal health risks

Naturally occurring radioactive materials (NORMs: 232Th, 226Ra, 40K) can reach our respiratory system by breathing of road dust which can cause severe health risks. Targeting the pioneering consideration of health risks from the NORMs in road dust, this work reveals the radioactivity abundances of NORMs in road dust from a megacity (Dhaka) of a developing country (Bangladesh). Bulk chemical compositions of U, Th, and K obtained from neutron activation analysis were converted to the equivalent radioactivities. Radioactivity concentrations of 226Ra, 232Th, and 40K in road dust ranged from 60-106, 110-159, and 488-709 Bq kg-1 with an average of 84.4 ± 13.1, 126 ± 11, and 549 ± 48 Bq kg-1, respectively. Estimated 226Ra, 232Th, and 40K radioactivities were, respectively, 1.7-3.0-, 3.7-5.3-, and 1.2-1.8-folds greater than the affiliated world average values. Mechanistic pathway of NORMs' enrichment and fractionation relative to the major origin (pedosphere) were evaluated concerning the water logging, relative solubility-controlled leaching and translocation, climatic conditions, and aerodynamic fractionations (dry and wet atmospheric depositions). Computation of customary radiological risk indices invokes health risks. Noticing the ingress of NOMR-holding dust into the human respiratory system along with the associated ionizing radiations, the computed radiological indices represent only the least probable health hazards. Nevertheless, in real situations, α-particles from the radioactive decay products of 232Th and 238U can create acute radiation damages of respiratory system. Policymakers should emphasize on limiting the dust particle evolution, and public awareness is required to alleviate the health risks.

ASSESSMENT OF THE NATURAL RADIOACTIVITY AND RADIOLOGICAL HAZARDS IN LAO CEMENT SAMPLES

The radioactivity concentrations of 226Ra, 232Th and 40K natural radionuclides in Lao Portland cement samples were measured using a gamma-spectrometry with a HPGe detector. The activity concentrations were found to vary from 28.32 ± 2.23 to 65.50 ± 2.83 Bq kg-1 with a mean value of 41.12 ± 2.44 Bq kg-1 for 226Ra; from 7.25 ± 2.00 to 44.01 ± 2.45 Bq kg-1 with a mean of 16.60 ± 2.37 Bq kg-1 for 232Th and from 49.19 ± 4.27 to 196.74 ± 4.75 Bq kg-1 with a mean of 141.48 ± 4.50 Bq kg-1 for 40K, respectively. The radiological parameters were estimated to assess the potential radiological hazard including radium equivalent activity, total external absorbed dose rate in outdoor air at 1 m above the earth's surface, the annual effective dose, the gamma and alpha-indices were calculated using the activity concentrations of 226Ra, 232Th and 40K. The results obtained in this study show no significant radiological hazards arising from using Lao Portland cement for building construction.

Assessment of Natural Radioactivity Levels and Potential Radiological Risks of Common Building Materials Used in Bangladeshi Dwellings

The concentrations of primordial radionuclides (226Ra, 232Th and 40K) in commonly used building materials (brick, cement and sand), the raw materials of cement and the by-products of coal-fired power plants (fly ash) collected from various manufacturers and suppliers in Bangladesh were determined via gamma-ray spectrometry using an HPGe detector. The results showed that the mean concentrations of 226Ra, 232Th and 40K in all studied samples slightly exceeded the typical world average values of 50 Bq kg(-1), 50 Bq kg(-1) and 500 Bq kg(-1), respectively. The activity concentrations (especially 226Ra) of fly-ash-containing cement in this study were found to be higher than those of fly-ash-free cement. To evaluate the potential radiological risk to individuals associated with these building materials, various radiological hazard indicators were calculated. The radium equivalent activity values for all samples were found to be lower than the recommended limit for building materials of 370 Bq kg(-1), with the exception of the fly ash. For most samples, the values of the alpha index and the radiological hazard (external and internal) indices were found to be within the safe limit of 1. The mean indoor absorbed dose rate was observed to be higher than the population-weighted world average of 84 nGy h(-1), and the corresponding annual effective dose for most samples fell below the recommended upper dose limit of 1 mSv y(-1). For all investigated materials, the values of the gamma index were found to be greater than 0.5 but less than 1, indicating that the gamma dose contribution from the studied building materials exceeds the exemption dose criterion of 0.3 mSv y(-1) but complies with the upper dose principle of 1 mSv y(-1).

Assessment of natural radioactivity levels of cements and cement composites in the Slovak Republic

The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices) of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58-19.1 Bq·kg(-1), 9.78-26.3 Bq·kg(-1) and 156.5-489.4 Bq·kg(-1) for 226Ra, 232Th and 40K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Ra(eq) = 67.87 Bq·kg(-1), gamma index Iγ = 0.256, alpha index Iα = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h(-1), external hazard index H(ex) = 0.182 and internal hazard index H(in) was 0.218. The radionuclide activity in composites ranged from 6.84-10.8 Bq·kg(-1) for 226Ra, 13.1-20.5 Bq·kg(-1) for 232Th and 250.4-494.4 Bq·kg(-1) for 40K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.

Assessment of radiation hazards due to natural radioactivity in some building materials used in Egyptian dwellings

Different types of Egyptian building materials from various locations in Cairo and its suburbs have been analysed for natural radioactivity using gamma ray spectrometry. Concentrations of (226)Ra, (232)Th and (40)K were in the ranges of (12 +/- 2.8-65 +/- 6.5), (5 +/- 1.8-60 +/- 6.7) and (159 +/- 3.8-920 +/- 12.7 Bq kg(-1)), respectively. The minimum concentration of (226)Ra, (232)Th and (40)K was found in gravel samples, whereas the maximum in granite samples. The results are compared with the published data of other countries and with the world average limits. The radiological hazard parameters: radium equivalent activity, gamma index, alpha index, absorbed dose rate and the annual exposure rate, were determined to assess the radiation hazards associated with Egyptian buildings. All studied samples are lower than world average limits.

Assessment of natural radionuclide content of cements used in Nigeria

The activity concentrations of (226)Ra, (232)Th and (40)K in seven brands of Portland cement used in Nigeria have been determined using a gamma-ray spectrometer with a hyperpure germanium detector. A total of 22 samples were collected from suppliers. The mean activity concentrations varied between 19.2 and 85.1 Bq kg(-1), 12.9 and 31.7 Bq kg(-1), and 31.5 and 116 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively, which are lower than the world averages for building materials. The average values of (226)Ra, (232)Th and (40)K content of all the cement samples are 43.8, 21.5 and 71.7 Bq kg(-1), respectively. The results of the radium equivalent activity, external hazard index, gamma activity index and alpha index calculated were all within the recommended limits for safety, and compare well with results obtained in some other countries of the world.

Measurement of the natural radioactivity in building materials used in Ankara and assessment of external doses

A total of 183 samples of 20 different commonly used structural and covering building materials were collected from housing and other building construction sites and from suppliers in Ankara to measure the natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K. The measurements were carried out using gamma-ray spectrometry with two HPGe detectors. The specific activities of the different building materials studied varied from 0.5 +/- 0.1 to 144.9 +/- 4.9 Bq kg(-1), 0.6 +/- 0.2 to 169.9 +/- 6.6 Bq kg(-1) and 2.0 +/- 0.1 to 1792.3 +/- 60.8 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The results show that the lowest mean values of the specific activity of (226)Ra, (232)Th and (40)K are 0.8 +/- 0.5, 0.9 +/- 0.4 and 4.1 +/- 1.4 Bq kg(-1), respectively, measured in travertine tile while the highest mean values of the specific activity of the same radionuclides are 78.5 +/- 18.1 (ceramic wall tile), 77.4 +/- 53.0 (granite tile) and 923.4 +/- 161.0 (white brick), respectively. The radium equivalent activity (Ra(eq)), the gamma-index, the indoor absorbed dose rate and the corresponding annual effective dose were evaluated to assess the potential radiological hazard associated with these building materials. The mean values of the gamma-index and the estimated annual effective dose due to external gamma radiation inside the room for structural building materials ranged from 0.15 to 0.89 and 0.2 to 1.1 mSv, respectively. Applying criteria recently recommended for building materials in the literature, four materials meet the exemption annual dose criterion of 0.3 mSv, five materials meet the annual dose limit of 1 mSv and only one material slightly exceeds this limit. The mean values of the gamma-index for all building materials were lower than the upper limit of 1.

Assessment of the natural radioactivity and radiological hazards in Turkish cement and its raw materials

The natural radioactivity due to presence of (226)Ra, (232)Th and (40)K radionuclides in raw materials, intermediate products (clinker) and end products (22 different cement types) was measured using a gamma-ray spectrometry with HPGe detector. The specific radioactivity of (226)Ra, (232)Th and (40)K in the analyzed cement samples ranged from 12.5+/-0.3 to 162.5+/-1.7Bqkg(-1) with a mean of 40.5+/-26.7Bqkg(-1), 6.7+/-0.3 to 124.9+/-2.5Bqkg(-1) with a mean of 26.1+/-18.9Bqkg(-1) and 64.4+/-2.3 to 679.3+/-18.2Bqkg(-1) with a mean of 267.1+/-102.4Bqkg(-1), respectively. The radium equivalent activity (Ra(eq)), the gamma-index, the emanation coefficient, the (222)Rn mass exhalation rate and the indoor absorbed dose rate were estimated for the radiation hazard of the natural radioactivity in all samples. The calculated Ra(eq) values of cement samples (37.2+/-8.7-331.1+/-15.5Bqkg(-1) with a mean of 98.3+/-53.8) are lower than the limit of 370Bqkg(-1) set for building materials. The Ra(eq) values were compared with the corresponding values for cement of different countries. The mean indoor absorbed dose rate is slightly higher than the population-weighted average of 84nGyh(-1).

Determination of specific activity of (226)Ra, (232)Th and (40)K for assessment of radiation hazards from Turkish pumice samples

The specific activity of (226)Ra, (232)Th and (40)K in 52 Turkish pumice samples collected from 11 geographical areas located in Central Anatolia, Eastern Anatolia, Mediterranean and Aegean regions was determined by gamma-ray spectrometry with a high-purity germanium (HPGe) detector. The specific activity of (226)Ra, (232)Th and (40)K ranged from 12.7+/-0.5 to 256.2+/-9.1Bqkg(-1) with a mean of 89.1+/-65.2Bqkg(-1), 12.3+/-1.0 to 237.9+/-12.2Bqkg(-1) with a mean of 87.0+/-61.4Bqkg(-1) and 300.1+/-5.5 to 1899.0+/-30.8Bqkg(-1) with a mean of 1211.9+/-419.8Bqkg(-1), respectively. Elemental concentrations were determined for U (from 1.0 to 20.7ppm with a mean of 7.2+/-5.3ppm), Th (from 3.0 to 58.6ppm with a mean of 21.4+/-15.1ppm) and K (from 1.0 to 6.1% with a mean of 3.9+/-1.3%). The radium equivalent activity (Ra(eq)), the activity index, the emanation coefficient, the (222)Rn mass exhalation rate, the indoor absorbed dose rate and the effective dose rate were estimated for the radiation hazard of the natural radioactivity in all samples. The calculated mean Ra(eq) value was 306.6+/-177.7Bqkg(-1) (54.6+/-5.5 to 737.6+/-49.0Bqkg(-1)) for all pumice samples. This value is lower than the recommended limit value of 370Bqkg(-1) for building raws and products. The emanation coefficient and the (222)Rn mass exhalation rate of all samples ranged from 29.4 to 42.9% with a mean of 36.2% and from 11.0 to 196.4microBqkg(-1)s(-1) with a mean of 73.5microBqkg(-1)s(-1), respectively. The mean indoor absorbed dose rate and the corresponding mean effective dose rate were 274.6+/-153.6nGyh(-1) (50.4-644.6nGyh(-1)) and 1.35+/-0.75mSvy(-1) (0.24-3.16mSvy(-1)), respectively. For all pumice samples the mean indoor absorbed dose rate is about three times higher than the population-weighted average of 84nGyh(-1), while the mean effective dose rate values except for PUM 05, PUM 06, PUM 10 and PUM 15 exceed the dose criterion of 1mSvy(-1).

Radiological significance of cement used in building construction in Turkey

The activity concentration of (226)Ra, (232)Th and (40)K in seven cement types from different factories and grinding plants were measured using a gamma ray spectrometry with HPGe detector. The average activity concentrations observed in the studied cement samples (all from 141 samples) were 40.0 +/- 27.1, 28.0 +/- 20.9 and 248.3 +/- 95.0 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The radium equivalent activity (Ra(eq)), the representative level index, the indoor absorbed dose rate and the corresponding annual effective dose were estimated for the potential radiological hazard of the cement. The Ra(eq) values were compared with the corresponding values for cement of different countries. The mean indoor absorbed dose rate (87.4 +/- 48.5 nGy h(-1)) is slightly higher than the population-weighted average of 84 nGy h(-1), whereas the corresponding effective dose rate (0.4 +/- 0.2 mSv y(-1)) is lower than the dose criterion of 1 mSv y(-1). The obtained results indicate no significant radiological hazards arise from using Turkish cement in building construction.

Assessment of external dose indoors in Lithuania

The aim of this paper was an assessment of external exposure indoors and its dependence on construction materials and indoor radon concentrations in Lithuanian living houses. Relationship of absorbed dose rate in air indoors and activity indexes of the most commonly used construction materials (wood, concrete and bricks) have been studied using results received in measurements done in >4700 rooms in 1995-2005. Possible connections of dose rate indoors with indoor radon concentrations are also discussed. Findings of this study helped to make an assessment of the mean value of effective dose of Lithuanian population due to external exposure indoors which is equal to 0.58 mSv y-1. The received data might also be used in improvement of quality of personal dosimetric measurements done in premises constructed of different construction materials.