Morphological features of the microdistribution of naturally occurring 10Pb/2l0Po and 226Ra in the teeth of children and juveniles

PURPOSE: To examine the microdistribution of natural alpha-radioactivity in deciduous teeth of children and the permanent teeth of juveniles extracted for orthodontic purpose from across the UK. MATERIALS AND METHODS: The microdistribution of 210Pb-supported 210Po and 226Ra in 708 deciduous and permanent teeth and 32 foetal teeth was measured on 1442 TASTRAK alpha-particle track detectors. RESULTS: Of the various findings, a number are of special interest. Around half of the 210Pb activity in the outer enamel of deciduous teeth appears to have been acquired in utero as a result of transplacental transfer. In deciduous and permanent teeth, 226Ra is concentrated mainly in the circumpulpal region, while the highest levels of 210Po are on the highly calcified outer enamel surface. Furthermore, activity concentrations recorded on this surface were In-normally distributed. CONCLUSIONS: 210Pb-supported 210Po activity on the outer enamel surface of permanent teeth constitutes an assay of cumulative environmental exposure with which to assess exposure in bone, both in utero and in childhood. Such assessment can be used to study geographical variations in the alpha-activity in teeth. More work is also required to determine the concentrations of both 210Po and 210Pb in the foetal skeleton.     

Spatial Distribution of Naturally Occurring 210Po and 226Ra in Children's Teeth

Deciduous and permanent teeth extracted from juveniles for orthodontic purposes have been analysed using α-sensitive plastic track detectors for the spatial distribution of total α-activity and naturally occurring ²¹⁰Pb-supported ²¹⁰Po and ²²⁶Ra. The distribution of these radionuclides is nonuniform, with ²¹⁰Po being primarily associated with outer enamel and ²²⁶Ra with the pulp. The observations suggest that ²¹⁰Pb/²¹⁰Po concentrates at the interface of enamel with saliva or blood, by means of unidirectional ionic exchange with calcium. In contrast, ²²⁶Ra concentrates in the predentine band at the interface with pulp and with systemic blood circulation, where its uptake is permitted by the incomplete calcification in this band. Activity concentration was measured in 900 teeth. Total concentration on the outer enamel surface of deciduous teeth, permanent teeth from children ?10 years and permanent teeth from children > 10 years give respective mean values of 8·63±0·26, 5·76±0.48 and 7·00±0·15 Bq kg^?1. ²²⁶Ra concentration on the corresponding longitudinal sections comprising pulp, dentine and annular enamel give respective mean values of 0·715±0·055, 0·418±0·083 and 0·514±0·029 Bq kg^?1. Mean activity concentration in 32 foetal teeth was 2·05±0·31 Bq kg^?1. The results form the basis of more detailed studies of (1) age-dependent uptake of α-radionuclides in teeth and their microdistribution, and (2) the geographical variation in activity concentration with respect to environmental factors such as domestic radon exposure.     

Aspects of the geographical variations of naturally occurring 210Pb/210Po in permanent teeth of juveniles in the UK

Purpose: To study geographical variations in the level of naturally occurring ²¹⁰Pb‐supported ²¹⁰Po in permanent teeth of juveniles in the UK.

Materials and methods: Permanent teeth extracted from 278 juveniles for orthodontic purposes were obtained from 48 counties in the UK. ²¹⁰Po activity concentration was measured on the outer enamel surface using TASTRAK α‐particle‐sensitive plastic track detectors.

Results: Geometric mean±SE activity concentrations in teeth from urban, suburban and rural areas, excluding the high radon area of Devon, were 8.41 +0.25/?0.24, 7.76 +0.37/?0.35 and 7.20 +0.49/?0.46?Bq?kg^?1, respectively. Overall, there was no significant association between α‐activity on the outer enamel surface of permanent teeth and proximity to the major UK motorways. However, when the data were considered with respect to the prevailing south‐westerly wind on the western side of the UK, a statistically significant association with respect to donors living downwind (on the easterly side) of the motorways was found. This effect was greater for sections of the M5 and M6 motorways that traverse urban areas. ²¹⁰Po levels in teeth were also associated with domestic radon concentration. This effect was comparable with that from traffic and urban pollution.

Conclusions: Higher levels of ²¹⁰Pb‐supported ²¹⁰Po are seen in permanent teeth of juveniles near sources of increased exposure in the UK. Inhalation uptake is an important pathway of exposure, especially with respect to domestic radon exposure. The results might be important in assessing integrated exposure to ²¹⁰Po in the skeleton and consequent high linear energy transfer dose to bone marrow.     

226Ra 228Ra 210Pb和210Po在水生生物及食物链中转移规律的探讨

目的 为了解天然放射性核素²²⁶Ra、²²⁸Ra、²¹⁰Pb与²¹⁰Po在水生物及食物链中转移和蓄积情况。方法 定点采集养殖水产品及栖息环境中水与底质沉积物, 按不同的实验需要, 每个鲜样分别剥取肉, 骨(壳),鳞片和胃肠。烹饪样品, 洗净、称重、清炖, 熟后分离出骨(壳),余为食物。样品分别测定²²⁶Ra、²²⁸Ra、²¹⁰Pb和²¹⁰Po含量。数据按统计学要求处理, 配对数据, 作了配对显着性检验。结果 ²²⁶Ra、²²⁸Ra和²¹⁰Pb主要沉积于骨(壳)中, 浓集系数为10²～10³,肉中为10⁰～10².²¹⁰Po主要蓄积在水生物胃肠中, 浓集系数在10²～10⁴,鱼类胃肠与贝类肉中可达10⁴.水产食品烹饪加工过程²²⁶Ra、²²⁸Ra和²¹⁰Pb在食物链中转移不明显, 经配对显着性检验, 差异无显着性(P0.05);然而210Po在淡水鱼类和虾类中转移是明显的, 肉配对检验有非常显着性差别(P<0.01).结论水生物对²²⁶Ra、²²⁸Ra、²¹⁰Pb和²¹⁰Po有很强浓集能力。     

Calibration of the direct LSC method for radon in drinking water: Interference from 210Pb and its progenies accumulated in 226Ra standard solution

The standard ASTM method is the most commonly applied method for determining ²²²Rn in drinking water. The method is calibrated with a ²²⁶Ra standard solution that usually contains variable amounts of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po if the standard has not recently been purified. Until now it has not been experimentally confirmed that these progenies do not interfere when the method is calibrated. In this study, interference was examined using three different organic cocktails and α/β liquid scintillation spectrometry to separately assess the effect of three radionuclides. The interference from ²¹⁰ Po was 4% for one of the cocktails if the ²²⁶Ra standard had been purified 5 years earlier. The interferences from ²¹⁰Pb and ²¹⁰Bi were negligible compared to that of ²¹⁰Po.     

Aspects of the geographical variations of naturally occurring 210Pb/210Po in permanent teeth of juveniles in the UK

PURPOSE: To study geographical variations in the level of naturally occurring 210Pb-supported 210Po in permanent teeth of juveniles in the UK. MATERIALS AND METHODS: Permanent teeth extracted from 278 juveniles for orthodontic purposes were obtained from 48 counties in the UK. 210Po activity concentration was measured on the outer enamel surface using TASTRAK alpha-particle-sensitive plastic track detectors. RESULTS: Geometric mean +/- SE activity concentrations in teeth from urban, suburban and rural areas, excluding the high radon area of Devon, were 8.41 + 0.25/-0.24, 7.76 + 0.37/-0.35 and 7.20 +0.49/-0.46 Bq kg(-1), respectively. Overall, there was no significant association between alpha-activity on the outer enamel surface of permanent teeth and proximity to the major UK motorways. However, when the data were considered with respect to the prevailing south-westerly wind on the western side of the UK, a statistically significant association with respect to donors living downwind (on the easterly side) of the motorways was found. This effect was greater for sections of the M5 and M6 motorways that traverse urban areas. 210Po levels in teeth were also associated with domestic radon concentration. This effect was comparable with that from traffic and urban pollution. CONCLUSIONS: Higher levels of 210Pb-supported 210Po are seen in permanent teeth of juveniles near sources of increased exposure in the UK. Inhalation uptake is an important pathway of exposure, especially with respect to domestic radon exposure. The results might be important in assessing integrated exposure to 210Po in the skeleton and consequent high linear energy transfer dose to bone marrow.     

Evaluation of uncertainty and detection limits in Pb and Po measurement in water by alpha spectrometry using Po spontaneous deposition onto a silver disk

An easy and accurate method for the determination of ²¹⁰Pb and ²¹⁰Po in water using ²¹⁰Po spontaneous deposition onto a silver disk is proposed and assessed for its detection capabilities according to the ISO Guide for the expression of uncertainty in measurement (GUM) and ISO Standard 11929-7 concerning the evaluation of the characteristic limits for ionizing radiation measurements. The method makes no assumption on the initial values of the activity concentrations of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po in the sample to be analyzed, and is based on the alpha spectrometric measurement of ²¹⁰Po in two different aliquots: the first one measured five weeks after the sampling date to ensure radioactive equilibrium between ²¹⁰Pb and ²¹⁰Bi and the second after a sufficient time for the ingrowth of ²¹⁰Po from ²¹⁰Pb to be significant. As shown, for a recommended time interval of seven months between ²¹⁰Po measurements, the applicability of the proposed method is limited to water samples with a ²²⁶Ra to ²¹⁰Pb activity ratio C_Ra/C_Pb≤4, as usual in natural waters. Using sample and background counting times of 24 h and 240 h, respectively, the detection limit of the activity concentration of each radionuclide at the sampling time for a 1 L sample typically varies between 0.7 and 16 mBq L⁻¹ for ²¹⁰Pb in water samples with an initial activity of ²¹⁰Po in the range 0-200 mBq L⁻¹, and between 0.6 and 8.5 mBq L⁻¹ for ²¹⁰Po in water samples with an initial activity of ²¹⁰Pb in the same range.     

Determination of 210Pb and 210Po in water using the extractive scintillation cocktail Polex™

Method validation was performed to achieve the accreditation for our determination method of ²¹⁰Pb and ²¹⁰Po in water. A Pb(NO₃)₂ carrier is added to the sample and lead is precipitated with Na₂SxH₂O. ²¹⁰Po is co-precipitated and the extractive scintillation cocktail Polex^™ is used to determine ²¹⁰Po and ²¹⁰Pb. Uranium is also extracted by Polex^™. It can be removed by washing the precipitate with 1% HNO₃. The ingrowth of ²¹⁰Pb from ²²²Rn during transportation time must be calculated. It has to be subtracted from the original ²¹⁰Pb in the sample and taken into account for the calculation of the lower limit of detection.     

Comparison of two direct LS methods for measuring 222Rn in drinking water using α/β liquid scintillation spectrometry

Direct liquid scintillation (LS) methods are widely used for surveying ²²²Rn in drinking water. Two direct methods are used that differ in sample composition. In a two-phase sample, water lies below a water-immiscible cocktail, while in a homogeneous sample water is mixed with an emulsifying cocktail. Although these methods were developed in the late 1970s, their performances have not been simultaneously tested. Here, the methods were compared in two ways: by preparing both types of sample similarly from ²²²Rn-bearing groundwater in one emulsifying and in three organic cocktails, and by calibrating the methods with a ²²⁶Ra standard according to their respective procedures. The samples were measured using α/β LS spectrometry. The standard deviations of parallel samples and the repeatability of the measurements were excellent for both methods, except two-phase ²²⁶Ra samples, whose efficiencies decreased slightly over time. This instability was due to interference from ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po, which accumulated in the ²²⁶Ra standard, and possibly also to the migration of ²¹⁴Pb and ²¹⁴Bi into the aqueous phase and deficient transfer of ²²²Rn from the water to the cocktail.     

Dose estimates for the local inhabitants from 210Po ingestion via dietary sources at a proposed uranium mining site in India

Abstract

Purpose: To study the distribution of ²¹⁰Po activity in food in Bagjata in East Singhbhum, India.

Materials and methods: ²¹⁰Po were analyzed in the food samples of plant origin such as cereals, pulses, fruits, vegetables and food of animal origin such fish, chicken, egg, etc., in and around Bagjata uranium mining area as a part of baseline study after acid digestion. The intake and ingestion dose of the radionuclide was estimated.

Results: The general range of ²¹⁰Po activity in all the dietary components ranged widely from <0.2–36 Bqkg^-1_fresh. In the food of plant origin, the minimum activity of ²¹⁰Po was estimated in vegetables while maximum in pulses. In food of animal origin, the observed minimum activity of ²¹⁰Po was in eggs and the maximum observed was in chicken samples. The intake of ²¹⁰Po considering all dietary components was found to be 464 Bq.Y^-1 while the ingestion dose was calculated to be 557 μSv.Y^-1, respectively. The estimated doses are reflecting the natural background dose via the route of ingestion, which is much below the 1 mSv limit set in the International Commission on Radiological Protection (ICRP) recommendations.

Conclusion: The study confirms that current levels of ²¹⁰Po do not pose a significant radiological risk to the local inhabitants.     

食品中的铅-210

本文报道了30种常用食品²¹⁰Pb含量, 它们是在样品中²¹⁰Pb～²¹⁰Po接近放射性平衡后, 用银片自沉积法测定²¹⁰Po, 计算出²¹⁰Pb含量。粮食、蔬菜和肉类的²¹⁰Pb平均浓度分剐为0.14, 15.08和1.26×10^-14Ci/g。     

Estimation of annual effective dose due to ingestion of natural radionuclides in foodstuffs and water at a proposed uranium mining site in India

Abstract

Purpose: To study the distribution of ²¹⁰Po, ²²⁶Ra, ²³⁰Th and U(nat) (naturally occurring radioisotopes of uranium [²³⁴U, ²³⁵U and ²³⁸U]) in food and water around the Bagjata uranium mining area in India.

Materials and methods: Radionuclides were analyzed in food samples of plant and animal origin after acid digestion. Intake and ingestion dose of the radionuclides were estimated.

Results: ²¹⁰Po, ²²⁶Ra, ²³⁰Th and U(nat) in all the dietary components ranged widely from < 0.2–36, < 0.02–1.58, < 0.01–2.8 and < 0.017–0.39 Bqkg^-1, respectively. The range of ²²⁶Ra and U(nat) in water was < 3.5–206 and < 12.6–693 mBql^?1, respectively. The intake of radionuclides considering food and water was calculated to be 760 BqY^?1 while the ingestion dose was 601 μSvY^?1. The estimated doses reflect the natural background dose via route of ingestion, which is below the 1 mSvY^?1 limit set by the International Commission on Radiological Protection (ICRP). However, the doses are more than the dose constraint of 300 μSvY^?1 as suggested by the ICRP for members of the public for planned disposal of long-lived radioactive waste.

Conclusion: The study confirms that current levels of radionuclides do not pose significant radiological risk to the local inhabitants, but they need close investigation in the near future.     

Enrichment and vertical profiles of 210Po and 210Pb in monazite areas of coastal Karnataka

A study on radiation level and radionuclide distribution in the environment of coastal Karnataka has revealed the presence of low-level monazite deposit in the Ullal beach area. The paper presents systematic studies on the distribution, enrichment and vertical profiles of ²¹⁰Po and ²¹⁰Pb, important daughter products of ²³⁸U, in Ombattu Kere, Summer Sand and the Bhagavathi Temple region of the Ullal beach area of coastal Karnataka. Sand samples collected at different depths from these locations were analyzed for ²¹⁰Po and ²¹⁰Pb activities to understand the distribution, enrichment and vertical profiles of these radionuclides in monazite area. The activity of ²¹⁰Po in the Ullal region is found to vary from 1.7 to 43.2 Bq kg^?1 with a mean value of 11.2 Bq kg^?1 and that of ²¹⁰Pb varies from 1.0 to 66.7 Bq kg^?1 with a mean value of 19.1 Bq kg^?1. The mean ²¹⁰Po/²¹⁰Pb ratio was observed to be 0.6. The absorbed gamma dose rate in the region varies in the range 39–460 nGy h^?1 with a mean value of 193 nGy h^?1.     

On the variation of the 210Po half-life at low temperature

Experiments were performed to verify the possible influence of the temperature and source matrix on the half-life of ²¹⁰Po. Since the precise measurement of the activity of an α-emitting source at cryogenic temperature is far from trivial, a simpler approach was used: the activity of a ²¹⁰Po source was measured at ambient temperature, but in between the measurements, the source was cooled down during a few weeks in a liquid helium Dewar. A ²¹⁰Po solid source was prepared by electro-deposition on a silver plate. The activity of this source was first measured at room temperature, using the defined solid angle α measurement method. The source was then placed in a specific gastight container inside a liquid helium bath at 4 K during 28 days. Then the source was heated up and measured again using the same instrument in the same geometric conditions. The same experiment was repeated with the source coated with a thin layer of silver, in order to be sure that the radioactive material was fully embedded inside the metallic matrix. Our experiments showed no evidence of ²¹⁰Po half-life change at low temperature. A reduction of the half-life of ²¹⁰Po by 6.3% at low temperature, as claimed by Raiola et al. (2007), would have lead to a decay-corrected activity reduction of about 1% after 29 days, which would have been easily detectable.The paper describes the steps of this experiment and gives a detailed uncertainty budget for the measurements. The half-life of ²¹⁰Po obtained in each measurement is compared with the evaluated value of (138.3763±0.0017) d.     

Determination of 210Pb and 226Ra/228Ra in continental water using HIDEX 300SL LS-spectrometer with TDCR efficiency tracing and optimized α⧸β-discrimination

An analytical method for determination of ²¹⁰Pb, ²²⁶Ra and ²²⁸Ra is presented based on adsorption on 3M Empore RadDiscs, and measurement applying liquid scintillation spectrometry (LSC) after elution. The LSC measurement was performed with optimized α⧸β-discrimination and isotope standardization using the triple to double coincidence ratio (TDCR). The consistency of measurement results between radioactive parent–daughter pairs ²¹⁰Pb/²¹⁰Bi, ²²⁶Ra/²²²Rn and ²²⁸Ra/²²⁸Ac was checked in long-term counting experiments and the influence ofinterference of in-growing daughters from ²²⁶Ra into the β-spectrum of ²²⁸Ra+²²⁸Ac was studied as well. Recommendations for optimized LSC ²²⁸Ra measurement besides presence of ²²⁶Ra are given.     

Geochronology of lake sediments using 210Pb with double energetic window method by LSC: An application to Lake Van

In this study the age and sediment accumulation rates of the lake sediment were calculated by using the ²¹⁰Pb concentrations through the sediment core. The specific activity of ²¹⁰Pb for each sediment section was determined by LSC with double energetic window method which relies on the direct determination of ²¹⁰Pb without waiting for the in growth of ²¹⁰Po from ²¹⁰Pb. For the successful determination of this radionuclide two counting windows were optimized to eliminate the overlapping of the beta spectra of ²¹⁰Pb and ²¹⁰Bi.     

Influence of heavy metals upon the retention and mobilization of polonium‐210 in rats

Purpose: To provide information about the tissue retention and mobilization of the alpha‐emitting radionuclide, polonium‐210 (²¹⁰Po), in rats under combined exposure to heavy metal ions and the chelating agent, 2, 3‐dimercaptopropane‐1‐sulfonate (DMPS).

Materials and methods: Rats were pre‐exposed intraperitoneally to either CdCl₂ or Pb(CH₃COO)₂. 9 or 15?h later they received ²¹⁰Po nitrate intravenously. The retention and excretion of ²¹⁰Po via the urine and faeces of pre‐exposed rats, as well as in pre‐exposed rats treated with DMPS, were followed. The radioactivity due to ²¹⁰Po in a broad spectrum of body tissues and excreta was measured by the liquid scintillation counting after sample digestion in a mixture of perchloric acid and hydrogen peroxide. The immunohistochemical localization of metallothioneins (MT) was studied using a mixture of murine monoclonal antibodies directed against MT I+II.

Results: The present study revealed different tissue distributions of polonium‐210 in the rats pre‐exposed to lead or cadmium ions when compared with that in ²¹⁰Po only controls. Under combined exposure to Pb or Cd, the spontaneous excretion of ²¹⁰Po was enhanced and could be further enhanced by treatment with DMPS. Treatment with this chelator was efficient even when its start was postponed until 24h after internal contamination of the body with ²¹⁰Po.

Conclusions: Polonium‐210 is bound in vivo to binding sites on various biomolecules, among them erythrocytic enzymes and MT. This phenomenon explains the different affinity and overall distribution of ²¹⁰Po in control body tissues. When the appropriate binding sites are occupied by lead or cadmium, enhanced natural excretion of polonium‐210 occurs.     

The natural radioactivity in Guarani aquifer groundwater, Brazil.

The measurements of gross alpha and gross beta radioactivity in groundwater samples from Guarani aquifer in Brazil are reported in this paper together with the activity concentration of the natural dissolved radionuclides (40)K, (238)U, (234)U, (226)Ra, (222)Rn, (210)Po, (210)Pb, (232)Th, (228Th), and (228)Ra. Most of the gross alpha radioactivity values were below the critical level of detection corresponding to 1mBq/L, however, the whole data set for the gross beta radioactivity and radionuclides (40)K, (238)U, (234)U, (226)Ra, (222)Rn, (210)Po, (210)Pb, and (228)Ra was submitted to a statistical treatment, considering class intervals arranged in geometric progression, because of the great variability of the activity. The analysis indicated lognormal distribution of the data, as usually observed in samples taken from the natural context. An inverse relationship between the gross alpha and gross beta activity has been identified and is related to an increase in the K content in the water. The mobility coefficient has been estimated for (238)U, (226)Ra, (232)Th and (228)Ra in Guarani aquifer and the results indicated that the radioelement solubility in the studied system varies according to the following order: radium>uranium>thorium. The implications of the data obtained in terms of standards established for defining the drinking water quality have also been discussed.     

Relationship between radioactivity of radium and concentrations of barium and lead in hokutolite

Hokutolite consists of barite (BaSO₄) and anglesite (PbSO₄), and contains significant amounts of radium isotopes as a radioactive mineral. Photon activation and gamma-ray spectrometry were employed to determine Ba, Pb and ²²⁶Ra contents in hokutolite samples and to investigate the correlation between ²²⁶Ra activity and both Ba and Pb content. ²²⁶Ra activity in 30 hokutolite samples were estimated in the range of 40–65 Bq/g and was positively related to Ba content (r=0.859, p<0.001), but independent of Pb content (r=−0.236, p=0.217). Experimental results implied that ²²⁶Ra preferably precipitated with Ba over Pb. The ²²⁶Ra activity in hokutolite from the Peitou Hot Spring was experimentally estimated based on the Ba/Pb ratio and expressed as ²²⁶Ra (Bq/g)=14.67 (Ba/Pb)_molar+14.13.     

Simultaneous determination of 226Ra and 210Pb in groundwater and soil samples by using the liquid scintillation counter-suspension gel method.

A method for the simultaneous determination of 226Ra and 210Pb in groundwater and soil samples by liquid scintillation counting was developed. Radium and lead were separated together from the samples as Ba(Ra) x PbSO4 co-precipitate, which was centrifuged and dissolved with 0.1 M EDTA solution (pH 9.0). Radium was separated as Ba(Ra)SO4 co-precipitate by adding ammonium sulfate and adjusting the pH of the solution to 4.2. Lead remaining in the solution was separated as PbSO4 precipitate by adding 9 M sulfuric acid. These Ba(Ra)SO4 and PbSO4 precipitates were purified with EDTA solution and used for measurement. To save time and to make counting samples simpler, direct counting of Ba(Ra)SO4 and PbSO4 precipitates instead of the phosphoric acid fusion method was attempted. Ba(Ra)SO4 and PbSO4 precipitates were suspended in the scintillation gel, and measured. Two liquid scintillation cocktails, Instagel XF and UltimaGold AB were used to prepare the counting samples. A mixture of water (40%), Instagel XF (40%) and UltimaGold AB (20%) formed a stable gel. Activities of 226Ra and 210Pb were calculated from the alpha spectrum of Ba(Ra)SO4 and beta spectrum of PbSO4, respectively. The long-term stability of the suspension gel was good. The analytical results of 226Ra and 210Pb in spiked groundwater samples were in good agreement with the known concentrations of 226Ra and 210Pb. The analytical values of 226Ra and 210Pb in the soil reference samples were within 11.5 and 1.6% of the relative error from the reference values, respectively.