Short-lived Radon Decay Products Research Articles

The calibration laboratories for the measurement of radon and short-lived radon decay products at the Federal Office for Radiation Protection (BfS)

Abstract In order to guarantee a high level of accuracy in all areas concerned with radon and radon decay products measurement the BfS has established a quality assurance management system. A set of calibration chambers and containers was installed in the laboratories which were subsequently accredited as a German Calibration Service (DKD) Calibration Laboratory for the units of radon and the potential alpha energy concentration of its short-lived decay products. It is traced back to the national standard established at the Physikalisch-Technische Bundesanstalt (PTB), which is at the same time the national institute for science and technology, and the highest technical authority for metrology in Germany. The equipment makes possible scientific investigations as well as calibrations for the measuring quantity “concentration of Rn-222 in air” in the range between 50 Bq/m3 and 100 kBq/m3 and also for the measuring quantity “potential alpha-energy concentration” (PAEC) in the range between 2 MeV/cm3 (3.2 E-7 J/m3) and 4000 MeV/cm31 (*6 .4 E-4 J/m3).

Simulation of the effect of mucociliary clearance on the bronchial distribution of inhaled radon progenies and related cellular damage using a new deposition and clearance model for the lung

Most of the current dosimetry models of inhaled short-lived radon decay products assume uniform activity distributions along the bronchial airways. In reality, however, both deposition and clearance patterns of inhaled radon progenies are highly inhomogeneous. Consequently, a new deposition-clearance model has been developed that accounts for such inhomogeneities and applied together with biophysical models of cell death and cell transformation. The scope of this study was to apply this model which is based on computational fluid and particle dynamics methods, in an effort to reveal the effect of mucociliary clearance on the bronchial distribution of deposited radon progenies. Furthermore, the influence of mucociliary clearance on the spatial distribution of biological damage due to alpha-decay of the deposited radon progenies was also studied. The results obtained demonstrate that both deposition and clearance of inhaled radon progenies are highly non-uniform within a human airway bifurcation unit. Due to the topology of the carinal ridge, a slow clearance zone emerged in this region, which is the location where most of the radio-aerosols deposit. In spite of the slow mucus movement in this zone, the initial degree of inhomogeneity of the activity due to the nonuniform deposition decreased by a factor of about 3 by considering the effect of mucociliary clearance. In the peak of the airway bifurcation, the computed cell death and cell transformation probabilities were lower when considering deposition and clearance simultaneously, compared to the case when only deposition was considered. However, cellular damage remained clustered.

Radon decay products equilibrium at different aerosol concentrations

The influence of aerosol particle concentration on the activity of short-lived radon decay products (RPDs) was investigated inside a standard radon box. The 218Po:214Pb:214Bi activity ratio was determined for unattached and attached fractions of radon decay products at different aerosol concentrations. For the unattached fraction, this ratio was 1:0.31:0.06, while for the attached aerosol fraction the activity ratio was 1:1.4:0.91 at a low aerosol concentration (2000 cm−3) and with the unattached fraction fp = 0.45. In this case, there was no additional aerosol in the standard radon box and the equilibrium shift ratio for the total activity (attached and unattached) was 1:0.55:0.27 for 218Po:214Pb:214Bi. When the aerosol was injected, the unattached fraction nearly disappeared at a high aerosol concentration (80000-90000 cm−3). The equilibrium shift ratio for the total activity at a high aerosol concentration was 1:2:1.5 for 218Po:214Pb:214Bi. This ratio was the same for the attached fraction. For no more than 0.01 of the unattached fractions, this ratio was 1:0.85:0.7. Radioactive equilibrium factors and unattached fractions were also determined at different aerosol particles concentrations. A negative correlation between unattached fraction and the radioactive equilibrium factor, as well as a positive correlation coefficient between the radioactive equilibrium factor and aerosol particle concentration in a standard radon box, has been determined.

Transmission of ultrafine particles through separating systems of dust samplers

Abstract In underground mines there is a radiation hazard associated with natural radioactive nuclides. The main sources of radiation exposure in Polish mines are short-lived radon decay products, radioactive mine water containing radium and the sediments precipitated from these waters. For miners, the most common hazard is usually the short-lived radon decay products. Aspirators, equipped with separation systems, are mostly used in order to control this hazard. Inside these aspirators there are meters which measure the radiation emitted by radioactive aerosols collected on the filter. The purpose of these systems is to remove particles from the air stream that do not form the respirable fraction. At the same time, however, a deposition of small-size aerosols takes place in them because of the high values of their corresponding diffusion coefficients. This excludes the possibility of their proper detection by radiation meters. In this paper, the transmission of particles up to 100 nm in size by the separating systems is evaluated. The evaluated transmission ranged from about 60% for sizes of 7 nm, reaching up to 95% at the boundary values of the tested range. The influence of the particle distribution of the aerosols on the radiation calibration coefficients was also investigated in a radon chamber, through their exposure to conditions where the air contained low aerosol concentrations of about 4.0 × 108 particles/m3 and also when it was nearly 100-times higher. In the first case, the measured sensitivity of the meters was about 20–30% lower, which was probably due to a higher number of small aerosols and, as a result, particle transmission decreased. However, at higher aerosol concentrations, the sensitivity of the meters remained practically the same, regardless of whether the air reached the filters by the separation systems or if they were omitted.

Radon concentration assessment in water sources of public drinking of Covilhã's county, Portugal

Radon, the heaviest of the noble gases on the periodic table of elements, is a natural radioactive element that can be found on water, soils and rocks.The main goal of this work is to present an evaluation of radon concentration on samples of water, used for human consumption, collected on uranium-rich granitic rock areas. Once the geological features of the sampling region evidence the presence of this natural radionuclides, their slow dissolution steadily increases concentration in ground water.Although, the most important contribution of natural radiation, for most populations, is from inhaled radon (generic term used commonly to refer to the isotope 222Rn), in some circumstances, exposure to natural radionuclides, through drinking water, could exceed acceptable levels, and also present a hazard.Despite the fact that radon can be reduced if the water is boiled, this gas, dissolved in ground water, can be released into the air during household activities such as showering, dishwashing and laundry. So, the short lived radon decay products will contribute to increase the number of those which are present in particles suspended in the indoor air and can be accumulated up to dangerous concentrations. Once the radon progeny emits highly ionizing alpha-radiation, they may cause substantial health damage after long-term exposure.Radon concentration measurements were performed on thirty three samples collected from water wells at different depths and types of aquifers, at Covilhã's County, Portugal with the radon gas analyser DURRIDGE RAD7. Twenty three, of the total of water samples collected, gave, values over 100 Bq/L, being that 1690 Bq/L was the highest measured value.

The influence of particle size distribution on dose conversion factors for radon progeny in the underground excavations of hard coal mine

In Polish underground mines, hazards caused by enhanced natural radioactivity occur. The sources of radiation exposure are short-lived radon decay products, mine waters containing radium 226Ra and 228Ra and the radioactive sediments that can precipitate out of these waters. For miners, the greatest exposure is usually due to short-lived radon decay products. The risk assessment is based on the measurement of the total potential alpha energy concentration (PAEC) and the evaluation of the related dose by using the dose conversion factor as recommended by relevant legal requirements. This paper presents the results of measurements of particle size distributions of ambient aerosols in an underground hard coal mine, the assessment of the radioactive particle size distribution of the short-lived radon decay products and the corresponding values of dose conversion factors. The measurements of the ambient airborne particle size distribution were performed in the range from a few nanometers to about 20 μm. The study therefore included practically the whole class of respirable particles. The results showed that the high concentration of ultrafine and fine aerosols measured can significantly affect the value of the dose conversion factors, and consequently the corresponding committed effective dose, to which the miners can be exposed.

A study of radon emitted from building materials using solid state nuclear track detectors

Radon is a natural radioactive gas derived from geologic materials. Inhalation of the short-lived decay products of radon has been linked to an increase in the risk of developing lung cancers if present at elevated levels. Accurate knowledge of exhalation rate plays an important role in characterization of the radon source strength in some building materials.For this purpose, in this study the Can Technique using CR-39 plastic track detectors was used to measure radium content and exhalation rates of radon in building samples collected from Jizan districts-a province in southern Saudi Arabia. The values of effective radium content are found to vary from 0.21 to 2.2 Bq kg−1 with a mean value of 0.92 Bq kg−1 and a standard deviation of 0.81. All the values of radium content in all samples under test were found to be quite lower than the permissible value of 370 Bq kg−1 recommended by Organization for Economic Cooperation and Development. The values of mass exhalation rates of radon vary from 1.6 to 16.7 mBq kg−1 h−1 with a mean value of 6.9 mBq kg−1 h−1, while the surface exhalation rates vary from 29.7 to 998.9 mBq m−2 h−1 with a mean value of 219.6 mBq m−2 h−1. Alpha index and annual effective doses have also been estimated.

Radon and Thoron Measured in Petrol and Gas-oil Exhaust Fumes by Using CR-39 and LR-115 II Nuclear Track Detectors: Radiation Doses to the Respiratory Tract of Mechanic Workers.

Mechanic workers are exposed to exhaust fumes when controlling vehicle engines in motion inside repair shops. To assess radiation doses due to radon short-lived progeny from the inhalation of exhaust fumes by mechanic workers, concentrations of these radionuclides were measured in petrol (gasoline) and gas-oil exhaust fumes by evaluating mean critical angles of etching of the CR-39 and LR-115 type II SSNTDs for alpha particles emitted by the radon and thoron decay series. Committed effective doses due to ²¹⁸Po and ²¹⁴Po short-lived radon decay products from the inhalation of petrol and gas-oil exhaust fumes by workers were evaluated. A maximum value of 1.35 mSv y⁻¹ due to radon short-lived decay products from the inhalation of gas-oil exhaust fumes by mechanic workers was found, which is lower than the (3-10 mSv y⁻¹) dose limit interval for workers.

Seasonal behavior of radon decay products in indoor air and resulting radiation dose to human respiratory tract

Most of radiation hazard of indoor radon is largely due to the radon progenies, which are inhaled and deposited in the human respiratory tract. It is essential to evaluate aerodynamic characteristics of the radon progenies, which are either attached or unattached to aerosol particles, because the dose is strongly dependent on the location of deposition in respiratory tract and hence on the aerodynamic characteristics of the aerosol particles. This paper presents the seasonal behavior of radon decay products in indoor air under domestic conditions at Nagoya University, Japan. A low pressure cascade impactor as an instrument for classifying aerosol sizes and imaging plate as a radiation detector have been employed to characterize the activity size distribution of short-lived radon decay products. In parallel, radon and its progenies concentrations were measured. Taking into account the progeny characteristics, the inhalation dose in the different seasons was also estimated based on a lung dose model with the structure that is related to the ICRP66 respiratory tract model. The result evident that, the highest dose 0.22 mSvy−1 was observed during the winter where the highest value of equilibrium equivalent concentration of radon (EEC) and lowest value of the activity median aerodynamic diameter (AMAD) were found in this season; whereas, the dose in spring appeared to be lowest 0.02 mSvy−1.

Indoor/outdoor radon decay products associated aerosol particle-size distributions and their relation to total number concentrations.

The activity size distributions of indoor and outdoor radioactive aerosol associated with short-lived radon decay products were observed at Nagoya, Japan, for some periods from 2010 to 2012, following the indoor observation by Mostafa et al. [Mostafa, A. M. A., Tamaki, K., Moriizumi, J., Yamazawa, H. and Iida, T. The weather dependence of particle size distribution of indoor radioactive aerosol associated with radon decay products. Radiat. Prot. Dosim. 146: (1-3), 19-22 (2011)]. The tendency of smaller indoor activity median aerodynamic diameter (AMAD) after rainfalls showed in the previous study was not consistently obtained, while the consistent tendency of less indoor radioactive particles with diameters in the accumulation mode was observed again after rainfalls. The indoor aerosols showed activity size distributions similar to the outdoor ones. Non-radioactive aerosol particle concentrations measured with a laser particle counter suggested a somewhat liner relationship with AMAD.

Radon dose assessment in underground mines in Brazil.

Underground miners are internally exposed to radon, thoron and their short-lived decay products during the mineral processing. There is also an external exposure due to the gamma emitters present in the rock and dust of the mine. However, the short-lived radon decay products are recognised as the main radiation health risk. When inhaled, they are deposited in the respiratory system and may cause lung cancer. To address this concern, concentration measurements of radon and its progeny were performed, the equilibrium factor was determined and the effective dose received was estimated in six Brazilian underground mines. The radon concentration was measured by using E-PERM, AlphaGUARD and CR-39 detectors. The radon progeny was determined by using DOSEman. The annual effective dose for the miners was estimated according to United Nations Scientific Committee on the Effects of Atomic Radiation methodologies. The mean value of the equilibrium factor was 0.4. The workers' estimated effective dose ranged from 1 to 21 mSv a(-1) (mean 9 mSv a(-1)).

Measurement of radon progenies using the Timepix detector

After an introduction of Timepix detector, results of these detectors with silicon and cadmium telluride detection layer in assessment of activity of short-lived radon decay products are presented. They were collected on an open-face filter by means of one-grab sampling method from the NRPI radon chamber. Activity of short-lived radon decay products was estimated from measured alpha decays of 218,214Po. The results indicate very good agreement between the use of both Timepix detectors and an NRPI reference instrument, continuous monitor Fritra 4. Low-level detection limit for EEC was estimated to be 41 Bq m(-3) for silicon detection layer and 184 Bq m(-3) for CdTe detection layer, respectively.

Attached and unattached fractions of short-lived radon decay products in outdoor environments: effect on the human respiratory system

The authors developed a model for determining the alpha- and beta-activities per unit volume of air due to radon ((222)Rn), thoron ((220)Rn) and their decay products attached and unattached to the aerosol in the outdoor air at the workplace in natural conditions at different locations in Morocco by using both CR-39 and LR-115 type II solid-state nuclear track detectors. In addition, the percentage of (218)Po, (214)Pb and (214)Po radionuclides attached to the aerosols and the unattached fraction f(j) for different values of the attachment rate were evaluated. Radon and thoron concentrations in outdoor air of the studied different locations were found to vary from 9.20±0.8 to 16.30±1.50 Bq m(-3) and 0.22±0.02 to 1.80±0.20 Bq m(-3), respectively. The committed equivalent doses due to the radon short-lived progeny (218)Po and (214)Po attached and unattached to the aerosol air were evaluated in different tissues of the respiratory tract of the members of the public from the inhalation of outdoor air.

Radon decay products in realistic living rooms and their activity distributions in human respiratory system

In this study, the individual activity concentrations of attached short-lived radon decay products ((218)Po, (214)Pb and (214)Po) in aerosol particles were measured in ten poorly ventilated realistic living rooms. Using standard methodologies, the samples were collected using a filter holder technique connected with alpha-spectrometric. The mean value of air activity concentration of these radionuclides was found to be 5.3±0.8, 4.5±0.5 and 3.9±0.4 Bq m(-3), respectively. Based on the physical properties of the attached decay products and physiological parameters of light work activity for an adult human male recommended by ICRP 66 and considering the parameters of activity size distribution (AMD = 0.25 μm and σ(g) = 2.5) given by NRC, the total and regional deposition fractions in each airway generation could be evaluated. Moreover, the total and regional equivalent doses in the human respiratory tract could be estimated. In addition, the surface activity distribution per generation is calculated for the bronchial region (BB) and the bronchiolar region (bb) of the respiratory system. The maximum values of these activities were found in the upper bronchial airway generations.

Interpretation of data from the screen-type diffusion battery with the sequential arrangement of trapping elements

The screen-type diffusion battery developed by the Institute of Industrial Ecology is described. The battery is characterized by a sequential arrangement of trapping elements made of woven metal nets. The instrument has been designed to assess the particulate composition of the environment by the content of short-lived decay products of radon. The simulation results are presented together with the interpretation of data of a real experiment, in which a three-modal distribution with median diameters in the ranges of 1–2, 3–4, and 19–20 nm, has been obtained.

Estimation of annual effective dose from indoor radon/thoron concentrations and measurement of radon concentrations in soil

Radon short-lived decay products generated from the earth is one of the serious indoor air and soil pollutants. The RAD-7 Electronic Radon Detector with a special accessory is used for the purpose of measurement. The radon and thoron concentrations in the houses of the study area are found to vary from 35±0.5 to 315.2±5.35 Bq m(-3) and 66.1±2.3 to 1710±139.36 Bq m(-3) with the average values of 98.65±1.9 and 388.19±11 Bq m(-3), respectively. From indoor air, the total annual effective dose is calculated and it varies from 0.88 to 7.94 mSv y(-1). The preliminary investigation shows that the thoron concentration is higher than the radon concentration in the houses of the study area. In general, the values of the indoor air are within the recommended action level of the International Commission on Radiological Protection, 2009.

Variation of activity concentration of radon decay products in the Curonian Spit

Variation of radon decay products activity concentration on the ground level of the atmosphere has been researched in the Curonian Spit. The influence of meteorological parameters on variation in these pollutants has been estimated. During the measurement period, activities concentration of radon short-lived decay products varied from 2 to 16 Bq/m3 and values of activity concentration measured during day and night varied from 5 to 7 times. The investigation data showed that meteorological parameters as temperature, relative humidity, wind speed and direction had great influence on radon decay products activity concentration. Negative corelation (–0.77) between radon decay products activity concentration and the temperature and positive correlation (0.8) with the relative humidity was determined. It has been observed that variations of activity concentration of radon decay products were influenced by the periodically varying wind direction – breeze, a phenomenon which rarely occurs in the region of the Baltic Sea.

The investigation of tobacco smoke influence on the changes of indoor radon and its short-lived decay products volumetric activities

Abstract The changes of radon and its short-lived decay products were investigated in accommodations under natural living conditions and in tobacco smoke-filled premises. The measured radon and its short-lived decay products volumetric activities, aerosol particle concentration in the air, radioactive equilibrium factor, unattached fraction factor values are presented. It was identified that the increase of aerosol particles concentration in the air (in smoke-filled premises) determines the increase of the unattached nuclides of radon short-lived decay products attached to aerosol particles (the average values of radioactive equilibrium factor varied from 0.35 to 0.72). In this case, larger volumetric activity of the alpha particles is registered. Therefore larger amount of radon progeny is inhaled in smoke-filled premises and there is an increased possibility of damaging the organism. Positive correlation (r = 0.9) between the radioactive equilibrium factor and aerosol particle concentration in the air o...

Radiation doses to individuals due to 238U, 232Th and 222Rn from the immersion in thermal waters and to radon progeny from the inhalation of air inside thermal stations

In Morocco, thermal waters have been used for decades for the treatment of various diseases. To explore the exposure pathway of (238)U, (232)Th and (222)Rn to the skin of bathers from the immersion in thermal waters, these radionuclides were measured inside waters collected from different Moroccan thermal springs, by means of CR-39 and LR-115 type II solid-state nuclear track detectors (SSNTDs), and corresponding annual committed effective doses to skin were determined. Accordingly, to assess radiation dose due to radon short-lived decay products from the inhalation of air by individuals, concentrations of these radionuclides were measured in indoor air of two thermal stations by evaluating mean critical angles of etching of the CR-39 and LR-115 II SSNTDs. Committed effective doses due to the short-lived radon decay products (218)Po and (214)Po by bathers and working personnel inside the thermal stations studied were determined.

Nanoaerosols including radon decay products in outdoor and indoor air at a suburban site.

Nanoaerosols have been monitored inside a kitchen and in the courtyard of a suburban farmhouse. Total number concentration and number size distribution (5–1000 nm) of general aerosol particles, as measured with a Grimm Aerosol SMPS+C 5.400 instrument outdoors, were mainly influenced by solar radiation and use of farming equipment, while, indoors, they were drastically changed by human activity in the kitchen. In contrast, activity concentrations of the short-lived radon decay products 218Po, 214Pb, and 214Bi, both those attached to aerosol particles and those not attached, measured with a Sarad EQF3020-2 device, did not appear to be dependent on these activities, except on opening and closing of the kitchen window. Neither did a large increase in concentration of aerosol particles smaller than 10 or 20 nm, with which the unattached radon products are associated, augment the fraction of the unattached decay products significantly.