Thoron Gas Research Articles

Radiological Risk to Inhalation of Thoron Gas from Medical Materials Samples Derived from Medical Plants in Iraq

Pollution by thoron is one of the factors that is harmful to human health. Medical materials, especially those derived from plants, have natural ingredients which are a major source of natural radioactivity, thoron being one of them. Therefore, the presence of harmful radioactivity in these materials is a matter of concern. This study determined the concentrations of thoron (220Rn or radon-220) from 70 samples of medical materials derived from medical plants using a CR-39 detector. Samples are drugs (solid), skin creams, herbs, toothpaste, drugs (liquid), and cosmetic products found in Iraqi pharmacies. Also, radiological risks such as Annual Effective Dose (AED), Excessive Lifetime Cancer Risk (ELCR), and Lung Cancer Case (LCC) due to inhalation of thoron from medical materials samples in pharmacies were calculated. The results show that the results of the thoron concentrations in the samples of medical materials ranged from 1.02 Bq/m3 to 74.53 Bq/m3, with an average value of 18.21 ± 2.00 Bq/m3. The range values of AED, ELCR (×10-3) and LCC (×10-6) were 0.01-0.588 mSv/y, 0.04-2.36, and 0.18-10.58, respectively. It was als found that the thoron concentrations in samples of the present study vary from a minimum of 12.82 Bq/m3 in cosmetic products samples to a maximum of 30.29 Bq/m3 in herbs samples. Nonetheless, all thoron and radiological risk values were lower than the acceptable world limit (thoron = 200-300 Bq/m3 by ICRP and AED = 1.1-4.4 mSv/y by UNSCEAR).

Assessment of radiological risk associated with thoron gas at primary schools in Al-Najaf city, Iraq

Children spend considerable time at home and school, so school is likely to be a second source of natural radionuclide exposure after home. This study evaluates the radiological risk associated with thoron gas in the air within the building of one hundred primary schools in Al-Najaf City, Iraq, using a CR-39 detector. The results of the average value of thoron concentration detector, the annual effective dose (AED), Excessive Lifetime Cancer Risk (ELCR) × 10−3, and Lung Cancer Case (LCC) × 10−9 measured in the building of the schools were 7.47 ± 2.85 Bq/m3, 0.03 ± 0.01 mSv/y, 0.11 ± 0.04, and 0.54 ± 0.20, respectively. All the results of indoor thoron were below the global average limit. The results of the radiological survey due to thoron concentrations for studied primary schools suggest that the radionuclides and their radiological hazard indexes in all studied schools in AL Najaf city, Iraq, do not impose a health hazard.

A study of radon, thoron and annual effective dose in some Egyptian dwellings by twin-cup dosimeter technique with LR-115 detectors

In the present study, Solid State Nuclear Track Detectors (LR-115–type II) based twin-cup dosimeters were used for estimating radon (222Rn) and thoron (220Rn) gas concentration levels in the environmental air of thirty dwellings in ten cities in Egypt. In the studied dwellings radon concentration levels were found to vary from 24.80 ± 3.98 to 39.71 ± 8.71 Bq m−3 with an average of 32.64 ± 4.34 Bq m−3 whereas thoron concentration is found to vary from 10.46 ± 2.87 to 15.41 ± 2.72 Bq m−3 with an average of 12.48 ± 1.58 Bq m−3. The total annual effective dose by the inhabitants of these dwellings due to radon and thoron was found below the recommended limit by the international agencies. The present study concluded that the dwellings are safe without posing significant radiological threats to human beings.

New-designed measurement device for radon and thoron activity concentration based on gas direct detection

A new-designed measurement device for radon and thoron activity concentration is developed based on gas direct measurement to support their in-situ calibration. It consists of a 2000 mm2 Passivated Implanted Planar Silicon (PIPS) detector, a Multi-Channel Analyzer (MCA), a Micro Controller Unit (MCU), and a small electrostatic chamber with a volume of nearly 23 ml. The device records those alpha particles emitted from radon and thoron gas, and the detection efficiency and the crosstalk factor of 218Po/216Po are determined by Monte Carlo simulation. Measurement results have been compared with AlphaGUARD DF2000 in pure radon and thoron environments, respectively. Results show that the measurement results of the devices and the reference monitor agree well with each other, with an average relative deviation of 0.48% for radon gas from about 3300 Bq/m3 to 38 kBq/m3 and -3.25% for thoron gas from about 25 kBq/m3 to 70 kBq/m3. Uncertainty assessment has also been done, and a relative system uncertainty of radon is about 6.8%, while that of thoron is nearly 7.3%.

Levels of Radon in Soils of Dodoma City, Central Tanzania

Purpose: Humans receive radiation doses exceeding fifty percent (50%) of the total dose from natural sources as a result of inhaling radon and thoron gases and their daughters. Radon occurs naturally in soils and can diffuse into indoor environments leading to adverse health effects for inhabitants. In this study, measurement of levels of radon gas in soils was performed with the purpose of categorizing areas and highlighting the likelihood of high levels of radon in indoor environments.
 Design/Methodology/ Approach: The study targeted the environs of Dodoma where the rapid expansion of human settlements is ongoing or anticipated. For easy access and convenience, the study was conducted in areas located along main roads leading to the nearby towns/cities. Sampling was done by inserting the drilling rod to a depth of approximately one meter (1 m) below ground level with the aid of a heavy hammer. The alpha pump was used to suck the soil gas from the ground through a metallic tube (the capillary probe) and pressed it into the ionization chamber of the measuring instrument (AlphaGUARD). Radon concentration was read directly from the instrument’s display.
 Findings: It was found that radon concentrations in soil vary from 18.8 to 233.5 kBq.m-3. Based on the radon risk criterion, surveyed areas range from normal to high radon risk categories.
 Research Limitation/Implication: The study only covered a limited area in Dodoma City, and therefore the results may not be representative of the entire city or even the surrounding regions.
 Practical Implications: This study is useful in categorizing building areas based on radon risk criterion with the purpose of reducing possibilities of radon-related health risks; mainly lung cancer to the population.
 Social Implications: Radon is a proven cause of lung cancer in humans. Therefore, knowledge of radon levels in the study area will help in setting the mitigation measures necessary for public health protection.
 Originality / Value/ Novelty: The study demonstrates an approach for estimating radon levels in soils which is beneficial to current and future researchers, environmentalists and regulators, among others.

Impact of humidity and flowrate on the thoron measurement sensitivity of electrostatic radon monitors

The accurate measurement of thoron activity concentration is an important issue in both thoron exposure evaluation and in reducing its influence on radon measurement. For radon monitors based on electrostatic collection technique and an alpha spectrometry analyser, air humidity and sampling flowrate are key factors influencing the sensitivity of thoron activity concentration measurement. For the purpose of improving thoron measurement sensitivity and stability, theoretical derivation and experimental studies were systemically performed in this study. The results show that thoron measurement sensitivity decreases as a negative exponential function with absolute humidity increasing, and the sensitivity of thoron is much lower than that of radon under the same conditions, which is mainly caused by the small value of the concentration ratio of thoron inside to outside of the chamber. When the air exchange rate of the measurement chamber (sampling flowrate/inner volume) increases, the measurement sensitivity of thoron gas first increases rapidly and then decreases slowly after reaching its maximum at the air exchange rate of 0.24 s−1. In practice, in the normal air exchange rate range (for example <0.05 s−1), increasing the sampling flowrate could greatly improve the thoron measurement sensitivity, which consequently suggests an effective way to update thoron measurement under the present conditions of the monitor.

Multifractal detrended cross-correlation analysis of radioactivity borne radon, thoron and meteorological time series

Owing to the potential health threats due to sustained exposure from the radioactivity born radon and thoron gases and their applications, especially radon as earthquake precursor, the complex dynamic relationship between either of the radioactive gas with meteorological parameters has become the focus of research area. Several studies have reported that meteorological factors greatly influence the radon and thoron radioactive gases. In present study we investigated the scaling behavior of cross-correlations between simultaneously observed Radon and Thoron time series with temperature, pressure, and humidity time series. Data for radon, thoron and other meteorological parameters were obtained using RTM 1688-2 active detector from March 2017 to April 2018, with the total number of data points in each time series greater then fifteen thousands. Data obtained was investigated by Multi-fractal Detrended Cross-correlation Analysis (MFDXA) method through detrended covariance function. The computed cross-correlations were also investigated for multifractal or monofractal nature as well as for the degree of multifractality. Results of the study show that all correlations exhibit long range power law behavior. A nonlinear variation of scaling exponent ′hxy(q)′ vs ‘q’ (order of fluctuation) shows multifractal nature of cross-correlations with hxy(q)>0.5 for all correlations. Which means that all correlations are persistently positive correlated. The degree of multifractality was estimated by the width of singularity spectrum Δα. The results show that for each of the correlations width of singularity spectrum is nonzero confirming the multifractal nature of computed correlations. Finally, for Radon/Thoron correlation with temperature and humidity the width of singularity spectrum i.e., Δα>0.5 shows high multifractality when compared with Radon/Thoron vs pressure correlation with Δα<0.5 showing low multifractality.

Assessment of Threshold Dose of Thoron Inhalation and Its Biological Effects by Mimicking the Radiation Doses in Monazite Placer Deposits Corresponding to the Normal, Medium and Very High Natural Background Radiation Areas.

The dose contributed from thoron (220Rn) and its progeny has been neglected in the dose assessment because of its short half-life (t1/2 = 55.6s) and generally low concentrations. Recently, concentrations of 220Rn gas and its progeny were found to be pronounced in the traditional residential dwellings in China, on beaches of India and in other countries. Accordingly, we investigated the biological effects of thoron (220Rn) decay products in various mouse organs, succeeding inhalation of thoron gas in BALB/c mouse. We investigated the biological effects upon thoron inhalation on mouse organs with a focus on oxidative stress. These mice were divided into (4 random groups): sham inhalation, thoron inhalation for 1, 4 and 10days. Various tissues (lung, liver and kidney) were then collected after the time points and subjected to various biochemical analyses. Immediately after inhalation, mouse tissues were excised for gamma spectrometry and 72h post inhalation for biochemical assays. The gamma spectrometry counts and its subsequent calculation of the equivalent dose showed varied distribution in the lung, liver and kidney. Our results suggest that acute thoron inhalation showed a differential effect on the antioxidant function and exerted pathophysiological alterations via oxidative stress in organs at a higher dose. These findings suggested that thoron inhalation could alter the redox state in organs; however, its characteristics were dependent on the total redox system of the organs as well as the thoron concentration and inhalation time.

A preliminary study on real-time Rn/Tn discriminative detection using air-flow delay in two ion chambers in series

Due to its short half-life, thoron gas has been assumed to have negligible health hazards on humans compared to radon. But, one of the decay products with a long half-life can make it to be transported to a long distance and to cause a severe internal dose through respiration. Since most commercial radon detectors can not discriminate thoron signals from radon signals, it is very common to overestimate radon doses which in turn result in biased estimation of lung cancer risk in epidemiological studies. Though some methods had been suggested to measure thoron and radon separately, they could not be used for real-time measurement because of CR-39 or LR-115. In this study, an effective method was suggested to measure radon and thoron separately from the free air. It was observed that the activity of thoron decreases exponentially due to delay time caused by a long pipe between two chambers. Therefore from two ion chambers apart in time, it was demonstrated that thoron and radon could be measured separately and simultaneously. We also developed a collimated alpha source and with this source and an SBD, we could convert the ion chamber reading to count rate in cps.

Pengukuran Konsentrasi Gas Radon (222Rn) dan Thoron (220Rn) Menggunakan Detektor CR-39 Pada Rumah Penduduk Di Nagari Alam Pauh Duo, Solok Selatan

Telah dilakukan pengukuran konsentrasi gas radon (222Rn) dan gas thoron (220Rn) menggunakan metode pasif CR-39 pada rumah penduduk di Nagari Alam Pauh Duo, Kabupaten Solok Selatan. Pengukuran bertujuan untuk mengetahui dosis efektif yang diterima oleh penduduk di daerah tersebut. Pengukuran gas radon dan gas thoron dilakukan menggunakan 50 buah detektor CR-39 yang dipasang pada 3 lokasi selama 3 bulan. Hasil pengukuran konsentrasi gas radon terkecil yaitu 7 ± 0,50 Bq/m3 sampai dengan yang terbesar yaitu 37 ± 2,65 Bq/m3 dengan rata-rata 14 ± 0,99 Bq/m3, sedangkan konsentrasi gas thoron yang terkecil yaitu 3 ± 0,18 Bq/m3 dan yang terbesar yaitu 25 ± 1,78 Bq/m3 dengan rata-rata 6,25 ± 0,45 Bq/m3. Hasil konsentrasi gas radon dan gas thoron yang didapatkan masih di bawah batas yang direkomendasikan oleh UNSCEAR tahun 2008 yaitu 300 Bq/m3. Estimasi dosis efektif yang diterima penduduk akibat paparan gas radon dan gas thoron yaitu 0,94 mSv/tahun dan 0,63 mSv/tahun. Nilai dosis efektif yang didapatkan tidak melebihi ambang batas yang telah direkomendasikan oleh PERKA BAPETEN No. 4 pasal 23 ayat 1 tahun 2013 yaitu 1 mSv/tahun.

Dosimetry of indoor alpha flux belonging to seasonal radon, thoron and their EECs.

Radon (222Rn) and thoron (220Rn) are ubiquitous radioactive noble gases present in the earth's crust. The source term for these gases includes soil and building materials as well. The radiological impact of radon/thoron gases and their decay products on human life is a matter of concern and has been given due attention in research and policy. The present study aims to measure and quantify residential radon/thoron gas and the decay product's concentration and to discuss the associated interpretations for Ludhiana district of Punjab, India. Passive measurement techniques employing a single-entry pinhole dosimeter for gases and direct progeny sensors for the decay product's concentration have been used in this work. The obtained data from these measurements have been analysed using appropriate statistical techniques. The variations have been linked with the changes in the ventilation conditions, building material, room type and altitude. A higher concentration of radon and thoron gas was observed in the winter season for the study region. It was estimated that the contribution of radon and thoron decay products towards the annual average inhalation dose is 75% and 25%, respectively.

Lung Cancer Risk Assessment due to Radon and Thoron Exposure in Dwellings in Ortum, Kenya

Radon and thoron gases are produced by radioactive decay of soil and rocks containing uranium and thorium. Radon and thoron in dwellings constructed using soil and rocks rich in uranium and thorium are considered as a major causes of lung cancer especially for nonsmokers. Despite the dangers that these gases can cause to human health, extensive mapping of concentration of radon and thoron gases in Kenyan dwellings has not been done. This phenomenon leaves a large population at risk of exposure to these gases especially in rural areas where good ventilation is not considered in most of the housing design. In this study, indoor radon and thoron exposure were measured in 7 dwellings chosen using purposive sampling method in Ortum, West Pokot county, Kenya. The radon and thoron concentration in mud houses was determined using a passive radon and thoron discriminative detector (RADUET). The detectors were placed in mud houses at a height of about 2 meters above the ground for 3 months (103 days). The concentrations of radon and thoron were calculated and found to range from 16 ± 6 to 72 ±13 and 18 ±11 to 110 ±30 respectively. The average radon and thoron concentration were found to be 40 ± 19 Bq/m3 and 54 ± 30 Bq/m3 respectively, which is below the International Commission on Radiological Protection (ICRP) recommended lower and upper limit of 100 Bq/m3 and 300 Bq/m3 respectively. The annual effective dose was found to be 1.03 mSv/y for radon and 0.30 mSv/y for thoron which is within the 1.3 mSv average global annual effective dose due to radon, thoron and its progeny.

Estimation of 222Rn, 220Rn exhalation rate and 226Ra, 232Th, 40K radionuclides in the soil samples of different regions of Gurdaspur district, Punjab

Soil is the main source of concentration of radon and thoron gases in the indoor environment. The level of radon and thoron concentration mainly depends upon the radium, thorium contents and radon exhalation, thoron exhalation from the soil. The exhalation rate is the primary index to estimate the natural radioactivity potential of soil. The radium, thorium and potassium activity concentration were analyzed by NaI (Tl) gamma ray spectrometer. Radon and thoron surface exhalation rates were determined by scintillation-based detector SMART RnDuo Portable Radon Monitor. The geometric mean value of radon mass exhalation rate is 1.3 mBqkg-1h−1 and thoron surface exhalation rate is and 951.5 mBqm-2s−1. The geometric mean values of activity concentration of 226Ra, 232Th and 40K were 30.3 Bqkg−1, 45.8 Bqkg−1 and 339.9 Bqkg−1 respectively. The Radium equivalent activity concentration for all the soil samples was below the level of 370 Bqkg−1, recommended for building materials, by OECD 1979 (Organization for Economic Cooperation and Development).

Measurement of Indoor Thoron Gas Concentrations Using a Radon-Thoron Discriminative Passive Type Monitor: Nationwide Survey in Japan.

As part of a nationwide survey of thoron (220Rn) in Japan, the indoor 220Rn gas concentrations in 940 dwellings were measured throughout one year, from 1993 to 1996, using a passive type 222Rn-220Rn discriminative monitor. The monitor was placed in a bedroom or a living room in each house for four successive three-month periods. The mean annual indoor 220Rn concentration was estimated from the four measurements in each house. The arithmetic mean, the median and the geometric mean for indoor 220Rn concentrations in 899 dwellings were 20.1, 9.6 and 10.0 Bq m−3, respectively. The 220Rn concentrations exhibited a log-normal distribution. It was found that the 220Rn concentrations were dependent on the nature of the materials used for wall construction and also on the distance of measurement from the wall. Significant seasonal variations in the 220Rn concentration were not observed. It would seem that the nature of the wall material contributed to the increased indoor 220Rn concentrations.

Lung dose measurement from indoor 222Rn and 220Rn in dwellings of Fatehgarh district of Punjab, India

In order to study the health risk factors caused by indoor radon and thoron gases, environmental testing of these gasses has been carried out in various dwellings in the Fatehgarh district of Punjab. The average concentration of indoor 222Rn (CR) and indoor 220Rn (CT) is 59.8±15.9 Bq/m3 and 70.6±22.4 Bq/m3. The equivalent dose rate for lung (H) ranges from 33.54 to 82.60 nSv with mean dose of 47.85±12.73 nSv. The Effective dose rate to lungs (DLung) due to radon emitted alpha particles and progenies ranges from 1.68 to 4.13 nGy h-1 with mean of 2.39±0.63 nGy h-1. The effective dose rates trachea-bronchial (DT-B) and pulmonary + pulmonary lymph (DP+PI) ranges from 2.01 to 4.96 nSv with average value of 2.86±0.63 nSv. The rate of lung dose DRL owing to radon varies from 4.03 to 9.91 nSv with average value of 5.74±1.52 nSv. The average of the 222Rn and 220Rn inhalation dose in the study region is not as much of the 222Rn and 220Rn overall average inhalation dose worldwide.

Evaluation of the Influence of Thoron on Portable Radon Measurement Devices

Radiation exposure due to 222Rn is recognized as a matter of international concern for its health risk to humans. Portable devices for 222Rn concentration measurements, which are user-friendly, can be easily installed and provides a direct readout of values of 222Rn concentration on the built-in LCD (liquid-crystal display) and internal storage. However, there is a possibility that 220Rn can influence experiments for 222Rn measurement because of some similarity in their element properties. In this preliminary study, the influence of 220Rn on the performance of two commercial portable devices for 222Rn measurements was investigated. It was found that the indicated value for radon concentration in these devices could be affected by the presence of thoron gas.

Radon and Thoron Concentrations Measurement in Tea Samples Consumed in Iraqi Markets Using CR-39 Detector

Tea is one the most food used in the form of cold and hot drinks in Iraq, so 12 samples of the most frequently traded teas have been collected on the market, where Radon and thoron levels were measured using CR-39 nuclear track detector, and exhalation rates of radon and thoron gas were calculated. The results show that the highest concentration of radon is in sample T-4 and the highest concentration of thoron is in sample T-5 and were 34.725 ± 13.2 Bq/m3 and 10.164 Bq/m3 respectively. The obtained radon levels is within the natural limits of the activity concentrations of the naturally occurring radionuclides in foods, and this will not form any risk on human health.

Inspection and radiation dose evaluation results for NORM-containing products in Taiwan

In 2018, “negative ion powder” mattress produced by a South Korean manufacturer producing a dose rate of > 1 mSv/year, was found to have monazite powder in it. In order to verify if other products advertised as containing “negative ion powder” were also hazardous, an investigation had been carried out by the Atomic Energy Council and Institute of Nuclear Energy Research in Taiwan. By the end of April 2019, 11 kinds and a total of 59 samples were inspected for radon content. The radiation doses for the samples were evaluated using Atomic Energy Council approval evaluation setup which was established according to the characteristics of the products. The highest concentration of 220Rn among the inspected mattresses was over 10 kBq/m3 and the evaluated annual dose was about 78.5 mSv. The linearity of the surface dose rate and the measured thoron gas concentration for the mattress samples was also discussed in this study.

Environmental radon, its exhalation rates and activity concentration of 226Ra, 232Th, and 40kK in Northern India

Human beings are constantly exposed to radioactivity in the environment. As they are major sources of harmful radiation, radionuclides found in the atmosphere might result in a substantial potential risk to living beings. On the Earth's surface, the radioactive elements uranium and radium are naturally present, contributing to radon and thoron gases in the indoor as well as outdoor climate, soil and water. Radon is one of the most important toxins that, after cigarette smoking, is the second most common cause of generating lung cancer. Due to these health-related concerns, a lot of work has been undertaken by numerous research organizations to determine their levels at different locations throughout the world. This paper is an attempt to comprehensively report with different techniques all those studies being carried out in this part of India so that a current assessment of the indoor radon levels should be available for further work in this field. Six northern Indian states, viz. Punjab, Haryana, Himachal Pradesh, Rajasthan , Uttar Pradesh and Uttarakhand are considered for this examination. This study also provides data on exhalation rates and activity concentration of natural radionuclides (226Ra, 232Th, and 40K) present in these states.

Estimation of natural radionuclide and exhalation rates of environmental radioactive pollutants from the soil of northern India

The estimation of radioactivity level is vital for population health risk assessment and geological point of view and can be evaluated as rate of exhalation and source concentration (226Ra, 232Th and 40K). The present study deals with the soil samples for investigation of radionuclides content and exhalation rates of radon –thoron gas from different sites in northern Haryana, India. Absorbed dose and associated index estimated in the present study are the measures of environmental radioactivity to inhalation dose. Effective doses received by different tissues and organs by considering different occupancy and conditions are also measured. Exhalation rates of radon and thoron are measured with active scintillation monitors based on alpha spectroscopy namely scintillation radon (SRM) and thoron (STM) monitors respectively. Sample height was optimized before measurement of thoron exhalation rate using STM. Average values of radon and thoron exhalation are found 16.6 ± 0.7 mBqkg−1h−1 and 132.1 ± 2.6 mBqm−2s−1 respectively. Also, a simple approach was also adopted, to evaluate the thoron exhalation which accomplished a lot of challenges, the results are compared with the data obtained experimentally. The study is useful in the nationwide mapping of radon and thoron exhalation rates for understanding the environmental radioactivity status.