Radon Daughter Concentrations Research Articles

Uncertainties associated with assessing Ontario uranium miners’ exposure to radon daughters

The Ontario uranium miners study is a large (n = 28 546) cohort with low levels of radon exposure relative to other uranium miner cohorts. Multiple methods were used over time to estimate annual occupational exposure to radon daughters including: mine-specific extrapolations by mining engineers, area sampling in limited areas of the mines combined with approximate working time and lastly, consistent exposure sampling in different locations of the mine combined with workers’ time cards. Nonetheless, estimating exposures involves assumptions that lead to some uncertainty in occupational exposure characterisation arising from the assessment approach and variability within workplace, over time and by individual. An evaluation of the total uncertainty associated with radon daughter exposure estimation in Ontario miners over time has not been conducted. The objective of this study was to identify the contributing sources and assess the total uncertainty associated with estimating occupational radon daughter exposure among underground Ontario uranium miners over the course of uranium mining. The five sources of radon daughter exposure uncertainty evaluated were: natural variations in radon concentration, estimation of working time, precision of the radon measurement method, unintended errors during sampling, and record keeping and transcription of exposure data. These sources were examined separately for the period 1958 to 1967 and then 1968 onward due to changes in radon daughter concentration measurement practices between these periods. The magnitude of uncertainty associated with each of these sources over time were determined by reviewing historical literature on uranium mining in Ontario as well as through expert advice. Using the root sum square method, the total radon daughter exposure uncertainty was found to be 53 to 67% in the earlier period of uranium mining from 1958 to 1967. This decreased to 31 to 39% for the period 1968 to 1996 with natural variations of radon daughter concentrations in mines accounting for the largest percentage of uncertainty. This assessment provides an initial step in understanding the effect of exposure uncertainty on risk estimates. The impact of this uncertainty on the dose-response relationship between radon exposure and cancer risk will be assessed in future work.

Detection of alpha radionuclides in air from patients during Ra-223 alpha radionuclide therapy

Ra-223 has recently been introduced to alpha radionuclide therapy. According to the decay scheme of Ra-223, an inert gas, Rn-219 is released from patients during alpha radionuclide therapy and its daughter radionuclides may accumulate around the patient. However, the concentration of these radon daughters during alpha radionuclide therapy was not obvious. Here, we first detected the radon daughters of Rn-219 around patients during alpha radionuclide therapy. While the Ra-223-administered patients were in a room for ~1.5 hours, the radon daughter concentration increased to 4 to 5 times higher than without the patients. When the patients were in the room, the energy spectra of the alpha particles in the air showed the peak of the radon daughter of Rn-219, Bi-211 (6.6 MeV), which was different from that without the patients. We conclude that the daughter radionuclides of Rn-219 are accumulated around the patient, and the concentration was higher than that of the natural radon daughters. However, the increase in levels of alpha emitters, while detectable, is lower than the daily variations and thus is likely not a source of concern for radiation exposure.

Intrinsic backgrounds from Rn and Kr in the XENON100 experiment

In this paper, we describe the XENON100 data analyses used to assess the target-intrinsic background sources radon (), thoron () and krypton (). We detail the event selections of high-energy alpha particles and decay-specific delayed coincidences. We derive distributions of the individual radionuclides inside the detector and quantify their abundances during the main three science runs of the experiment over a period of sim 4,hbox {years}, from January 2010 to January 2014. We compare our results to external measurements of radon emanation and krypton concentrations where we find good agreement. We report an observed reduction in concentrations of radon daughters that we attribute to the plating-out of charged ions on the negatively biased cathode.

Radon Concentrations Measurement in Dwellings of Kufa Technical Institute, Iraq Using LR-115 Nuclear Track Detector

In this work, radon concentrations were measured in dwellings Kufa Technical institute, Iraq between November 2014 to February 2015 using time integrated passive radon dosimeters containing LR-115 Type II plastic track detectors. Also, we calculated the concentration of short-lived radon daughters, potential alpha energy, working level month, the annual effective dose rate, the annual equivalent dose rate and the excess lifetime cancer risk in all dwellings under study. The radon concentration in these dwelling ranges from (15.211 ± 2.745 to 32.445 ± 09.200) Bq/m3 with an average of (21.567 Bq/m3), which within the acceptable radon levels (50-150) Bq/m3 recommended by the International Commission on Radiological Protection (ICRP). The mean the excess lifetime cancer risk were found to be ranges from 35.458 to 75.633 with an average value of 50.297 per 106 persons. These values are within in the safe limits recommended by the international organizations.

Dust, Radiation and Diesel Exhaust Exposures in Ontario Uranium Mines and Mills

Aim: The objective of this paper was to summarize a comprehensive survey of airborne dust, radiation, and diesel exhaust in two Ontario uranium mines which was conducted by the Occupational Health Protection Branch of Ontario Ministry of Health in 1974. Materials and Methods: About 1000 dust samples of various types were collected from the mine and mill areas under normal routine working conditions. Dust sampling was conducted using various sampling devices including midget impingers, konimeters, and both area and personal respirable dust samplers. About 400 measurements of radon daughter concentrations were made, usually in the same area where dust samples were taken. Diesel exhaust gases, carbon monoxide, formaldehyde, and oxides of nitrogen, were measured using Drager colorimetric tubes, as an index of diesel exposure. Unburnt carbon from diesel exhaust was determined from some of the dust samples. Results: The results show that dust exposure, including crystalline silica (α‑quartz), was generally higher than the recommended exposure limits of the time. Radon exposure was also in excess of the exposure limits of the time in some work areas. Diesel exhaust gases were mostly below the threshold limit value of the time. Conclusions: The data set described in this paper would be useful in future epidemiological or health studies of the uranium miners group for establishing the work‑relatedness for diseases such as lung cancer from radon exposure and silica, respiratory diseases such as silicosis and chronic obstructive pulmonary disease, and autoimmune diseases. It would also be useful in estimating exposure of individual miners for the assessment of compensation claims.

An improved mathematical model for prediction of air quantity to minimise radiation levels in underground uranium mines

Ventilation is the primary means of controlling radon and its daughter concentrations in an underground uranium mine environment. Therefore, prediction of air quantity is the vital component for planning and designing of ventilation systems to minimise the radiation exposure of miners in underground uranium mines. This paper comprehensively describes the derivation and verification of an improved mathematical model for prediction of air quantity, based on the growth of radon daughters in terms of potential alpha energy concentration (PAEC), to reduce the radiation levels in uranium mines. The model also explains the prediction of air quantity depending upon the quality of intake air to the stopes. This model can be used to evaluate the contribution of different sources to radon concentration in mine atmosphere based on the measurements of radon emanation and exhalation. Moreover, a mathematical relationship has been established for quick prediction of air quantity to achieve the desired radon daughter concentration in the mines.

Measurement of Radon Concentrations and Annual Dose Rate in some Regions of Baghdad City using LR-115 Nuclear Track Detector

In this work, LR-115 solid state nuclear track detector used to measure the indoor and outdoor radon concentrations, the annual absorbed dose rate and annual effective dose rate to the lung, were measured in nine houses at different places of Baghdad city, the observed values of indoor and outdoor radon concentrations was in range of 14.7-46.17 Bq/m 3 and 9.69–35.69 Bq/m 3 respectively. The resulting concentration of Short-lived radon daughters expressed in term of an equilibriumequivalent radon concentration (EEC), the minimum and maximum indoor results of (EEC) was 5.88-18.46 Bq/m 3 and the outdoor results was 6.78-24.98 Bq/m 3 . The Potential Alpha Energy (PAE) concentration expressed in Working Level (WL) units was in the range of 1.58-4.99 mWL in indoor and 1.8-6.75 mWL in outdoor regions. The annual effective dose calculated according to the radiation weighting (WR) factor for alpha particles and the tissue weighting (WT) factor and the annual absorbed dose rate, the present results confirmed that the radon gas concentrations in all the nine places of Baghdad city are lower than the International Commission Radiation Protection (ICRP) agency, recommended value (200Bq/m 3 ).

Measurements of indoor radon, thoron, and their progeny using twin cup dosimeters in rural areas of Northern India

Radon, thoron, and their progeny are largest contributors to the radiation dose received by human beings present in the natural environment. The indoor radon depends upon many factors such as building materials, meteorology, ventilation, and occupant’s behavior. This paper presents the measurements of indoor radon, thoron, and their progeny in four villages in rural area of district Kanshiram Nagar (Kasganj) in the state of Uttar Pradesh in Northern India. The concentration of indoor radon and thoron varies from 10.32 to 72.24 and 11.61 to 84.49 Bq m−3 with a geometric mean (GM) of 29.49 and 31.20 Bq m−3, respectively. The concentration of radon and thoron daughters was found to vary from 1.11 to 7.80 and 0.31 to 2.28 mWL, respectively. The annual exposure due to radon and thoron mainly vary from 0.05 to 0.30 WLM. The preliminary results (i.e., bare mode exposure of the LR-115 detectors fixed on cards) of this study have been separately published and compared this recent data with those results.

KATERINA: An in situ spectrometer for continuous monitoring of radon daughters in aquatic environment

The detection system KATERINA has been used in the National Laboratory of Gran Sasso (close to L’ Aquila) in Italy for short term continuous monitoring of radon daughter concentrations in a groundwater path. The system was immersed in an water tank which was supplied with groundwater discharged from the mountain of Gran Sasso. The system offers quantitative results using calibration parameters obtained by reference sources and appropriate system efficiency simulation. Measurements were performed in two periods (December 2005 and November 2007) exhibiting almost constant radon level 2.8 Bq/l in the first period, while in the second period it increased up to 6.8 Bq/l. This gradual enhancement of radon background level could be attributed to the increase of microseismicity that occurred from late of 2007 till April 2009.

9151 Treatment of patients with advanced non-small-cell lung cancer (NSCLC) with erlotinib: results from clinical practice

Bare cellulose nitrate LR-115 films are being used by us as detectors in the survey of radon in dwellings in Algiers. These detectors have been calibrated in a 12-litre air-tight glass bell-jar, and also in an unmodified room atmosphere. In the first experiment, four track films, alongside a semiconductor detector (SCD), were fixed on a stand well away from a radon source. Alpha activity was allowed to grow for fifteen days, with daily measurements recorded with the SCD, until equilibrium between radon production and decay had been reached. The active volume of air producing the alpha counts in LR-115 was estimated. In the second calibration experiment, a set of ten LR-115 dosemeters was exposed in an unmodified room atmosphere in an occupied house for a period of two months. The radon-daughter concentration was monitored daily, using active devices. From these two experiments a calibration factor to be used in the measurement of activity from radon in dwellings, in terms of track densities observed on LR-115 films, was deduced.

Radon daughters’ concentration in air and exposure of joggers at the university campus of Bangalore, India

The concentration of radon daughters in outdoor air was measured continuously from January 2006 to December 2006 near the Department of Physics, Bangalore University campus, Bangalore. The concentration was measured by collecting air samples at a height of 1 m above the ground level on a glass micro fibre filter paper with a known air flow rate. The results show that the radon progeny concentration exhibits distinct seasonal and diurnal variations that are predominantly caused by changes in the temperature gradient at the soil–atmosphere interface. The concentration was found to be high from 20.00 to 8.00 hrs, when the turbulence mixing was minimum and low during the rest of the time. In terms of the monthly concentration, January was found to be the highest with September/August being the lowest. The diurnal variations in the concentrations of radon progeny were found to exhibit positive correlation with the relative humidity and anti-correlation with the atmospheric temperature. From the measured concentration, an attempt was made to establish the annual effective dose to the general public of the region and was found to be 0.085 mSv/a. In addition, an attempt was also made for the first time to study the variation of inhalation dose with respect to the physical activity levels. Results show that in the light of both the effect of chemical pollutants and radiation dose due to inhalation of radon daughters, evening jogging is advisable.

Design of an alpha spectrometry system for separated measurement of radon/thoron daughters’ concentration by lexan PC SSNTD

A special system has been designed to measure separately the concentration of radon and thoron alpha emitter's daughters in air. The system components consist of collimators, energy degraders, a filter and a lexan PC (polycarbonate) film, which are integrated and connected to a small portable pump. In this spectrometry method, alpha peaks are resulted from registered track size distribution in a wide energy range of 0.9–5.2 MeV under new electrochemical etching (ECE) conditions. Geometric characteristics of the system components are determined based on the optimization between desirable FWHM and detection efficiency by means of the Monte Carlo simulation method using the Fluka code. The results show that 218Po and 214Po from radon chain and 216Po (which is the representative of thoron concentration), 212Bi and 212Po from thoron chain can be measured separately in a mixed field with the FWHM of less than 0.2 MeV. The sensitivity was calculated to be 8.5 and 0.018 (Track cm −2 kBq −1 m 3 h −1) for radon and thoron, respectively. The radon level can be measured via 218Po concentration using a special measurement setting so that a short-term measurement of equilibrium factor can be performed by this spectrometry method.

Modelling of cell deaths and cell transformations of inhaled radon in homes and mines based on a biophysical and microdosimetric model

Purpose: In this study a biophysical mechanism-based microdosimetric model was applied to predict the biological effects of inhaled radon progenies in homes and in uranium mines.Materials and methods: The radon daughter concentrations of more than 2000 homes were averaged in case of home exposure and the New Mexico uranium mine data were used in case of exposure in mines. The complex microdosimetric model applied in this work was developed by combining a computational fluid and particle dynamics (CFPD) lung model with a lung dosimetry model that quantify the local distribution of radiation burden and the Unit-Track-Length Model, which characterizes the biological outcome of the exposure.Results: Our results show that the inhomogeneity of radon daughter deposition is stronger in the case of mines. Consequently, the numbers of cells which receive multiple hits and the maxima of radiation burdens are significantly higher in mines. In contrast to this, the distributions and maximum values of cell transformation probabilities are very similar in the two cases.Conclusions: If the same amounts of inhaled progenies are considered then primary cellular consequences are very similar in case of homes and mines, however, the local maxima of radiation burden are higher in mines.

The radon indicator

The radon indicator is an efficient instrument for measuring the radon daughter concentrations in a house or dwelling. Physics or environmental science students could build a radon indicator as a student project. Another possibility would be to use a radon indicator in a student investigation of radon levels in different houses. Finally the radon indicator is an excellent device for producing a radioactive source, free of charge, for the study of α-, β- and γ-radiation. The half-life of the activity collected is approximately 40 min. The radon indicator makes use of an electrostatic method by which charged particles are drawn to a small aluminium plate with a high negative voltage (−5 kV), thus creating a strong electric field between the plate and a surrounding copper wire. The radioactivity on the plate is subsequently measured by a GM-counter and the result calculated in Bq m−3. The collecting time is just 5.5 min and therefore the instrument is only suitable for use in a short-time method for indicating the radon concentration. An improved diagram, ground-radon and/or wall-radon in houses, is presented on the basis of the author's measurements recorded with the radon indicator over many years. This diagram is very useful when discussing how to reduce radiation levels in homes.

Indoor radon, thoron, and thoron daughter concentrations in Korea

A nationwide survey for radon ( 222Rn), thoron ( 220Rn), and thoron daughters has been conducted. The arithmetic mean of annual radon concentration in Korean dwellings was 53.4±57.5 Bq/m 3. The indoor radon concentration showed a lognormal distribution with a geometric mean and its standard deviation of 43.3±1.8 Bq/m 3. The arithmetic mean of annual thoron and its progeny concentrations in Korean dwellings were 45.2±110.1 and 0.99±1.00 Bq/m 3, respectively. The equilibrium factor between thoron and its progeny was 0.022. The arithmetic mean indoor gamma dose rate was 212±52 nGy/h. The radon concentrations in the traditional and modern style houses were about two times higher than those in apartments. The average annual effective doses to the general public from radon, thoron, and gamma dose rate were 1.35, 0.23, and 1.03 mSv/y, respectively.

Radon and thoron monitoring in the environment of Kumaun Himalayas: survey and outcomes

Monitoring of radon, thoron and their daughter products was carried out in houses of Kumaun Himalaya, India using LR-115 plastic track detectors. The measurements were made in residential houses from June 1999 to May 2000 at a height of 2.5 m from ground level using a twin chamber radon dosimeter. The twin chamber radon dosimeter can record the values of radon, thoron and their decay products separately. Maximum and minimum indoor radon and thoron concentrations were evaluated and activity concentrations of radon and thoron daughters were estimated. The resulting dose rates due to radon, thoron and their decay products varied from 0.04 to 1.89 μSv/h. A detailed analysis of the distribution of radon, thoron and their decay products inside the house is also reported. The observed dose rates inside the houses of Kumaun Himalaya were found to be lower than the ICRP recommended value of 200 Bq/m 3 and thus are within safe limits.

Mortality from lung cancer among silicotic patients in Sardinia: an update study with 10 more years of follow up

OBJECTIVESTo evaluate the association between silica, silicosis and lung cancer, the mortality of 724 patients with silicosis, first diagnosed by standard chest x ray film between 1964 and 1970, has...

Deterministic chaos in atmospheric radon dynamics

The correlation dimension and Lyapunov exponents have been calculated for two time series of atmospheric radon daughter concentrations obtained from four daily measurements during the period 1993–1996. A number of about 6000 activity concentration values of 222Rn and 220Rn daughters have been used. The measuring method is based on aerosol collection on filters. In order to determine the filter activity, a low background gross beta measuring device with Geiger‐Müller counter tubes in anticoincidence was used. The small noninteger value of the correlation dimension (≃2.2) and the existence of a positive Lyapunov exponent prove that deterministic chaos is present in the time series of atmospheric 220Rn daughters. This shows that a simple diffusion equation with a parameterized turbulent diffusion coefficient is insufficient for describing the dynamics in the near‐ground layer where turbulence is not fully developed and coherent structures dominate. The analysis of 222Rn series confirms that the dynamics of the boundary layer cannot be described by a system of ordinary differential equations with a low number of independent variables.

Diurnal and seasonal variation of the equilibrium state between short-lived radon decay products and radon gas in ground-level air.

To study seasonal and diurnal variations and the effect of meteorological parameters, the equilibrium factor F (i.e. the ratio of equilibrium equivalent radon daughter concentration and radon gas concentration) was determined as a result of measurements on a test field at Munich-Neuherberg, Germany, continuously from October 1995 through March 1997. On average, F was found to be 0.62+/-0.09 (95% confidence level). The time series of F showed no distinct seasonal variations. Nevertheless, typical diurnal variations as well as seasonal variations of the diurnal behaviour were observed. Generally, F was found to be increased in the early afternoon, i.e. under conditions of enhanced vertical mixing in the atmosphere. The daily differences between high and low values of F depended on the season. On average, low F values were characteristic for days with precipitation and high wind speed, i.e. under turbulent atmospheric conditions. Therefore, taking daily mean values into account, F was found to be positively correlated with the aerosol concentration, although a relationship between the diurnal behaviour of the aerosol concentration and that of F was not detectable.

A Stratified Approach to Individual Dosimetry for Radon Daughters in Mines

Measurements of radon daughter concentrations in some mines suggest that exposures in certain cases might routinely approach the exposure standards of 4 WLM.y -1 recommended by ICRP. This paper discusses the options for individual dosimetry and the principles behind three popular methods of exposure estimation viz. personal dosemeter for radon daughters, personal dosemeter for radon gas coupled with knowledge of equilibrium factor, and time-weighted area monitoring. It is concluded that there can be considerable technical benefit in favouring radon gas personal dosemeters over dosimetry based on area monitoring. Evidence is presented to show that area monitoring data often leads to overestimates of exposure, and personal monitoring usually leads to more realistic estimates of individual exposure. The degree of overestimation by area monitoring is quantified and used to propose a basis for designing a practical but focussed programme of personal dosimetry with the highest priority being given to reliable dosimetry for miners wit the highest exposures.