Occurrence of radon in some schools of Parma and Reggio Emilia (Northern Italy)

Summary Forty-seven measurement of radon concentration were made in some schools of Parma, Reggio Emilia, Albinea and Borzano. The method used was that of activated carbon canisters, which were placed in classrooms, laboratories, libraries and headmaster's offices for at least 48 hours in the period November '90–March '91. It was possible to determine the amount of radon in each canister counting the Pb-214 and Bi-214 gamma emitters by means of NaI (Tl) and Ge (I) detectors. The mean radon concentrations were: 20 Bq/m³ in Parma; 24 Bq/m³ in Reggio Emilia; 46 Bq/m³ in Borzano and 52 Bq/m³ in Albinea. The values recorded in schools are similar to the values previously recorded in dwellings of Parma and Reggio Emilia.     

Preliminary dose estimation from indoor radon for the medical staff of Radiation Oncology and Nuclear Medicine

The aim of this preliminary study was to measure the indoor radon activity concentration in the houses and offices of Radiation Oncology and Nuclear Medicine staff at Dokuz Eylül University and to assess the results from a radiological perspective. LR-115 type II solid-state nuclear track detectors were installed in the homes and hospital and were exposed for 2 months. LR-115 type II detectors were etched for 90 min in 10% (2.5 M) NaOH solution at 60°C and radon activity concentration was determined from observed microscopic track densities. It was observed that measured indoor radon concentration ranged between 18 and 624 Bq/m³ with a geometric mean of 95 Bq/m³ in hospital, and between 22 and 560 Bq/m³ with a geometric mean of 129 Bq/m³ in homes. Estimates of the annual effective dose received by medical staff who participated in the study ranged between 0.76 and 8.79 mSv. On average, the hospital building contributed 41% to the annual effective dose. The reported values for radon concentrations and the corresponding estimated annual effective equivalent doses were within the limits recommended by the International Commission on Radiological Protection as well as the Turkish Atomic Energy Commission recommended limits for workplaces and houses.     

Thoron levels in traditional Chinese residential dwellings

A survey on radon (²²²Rn), thoron (²²⁰Rn) and its decay products (²²⁰RnD) was conducted in Chinese traditional residential dwellings constructed with loam bricks or soil wall. The activity concentrations in 164 dwellings under investigation were 72.4±59.2 (arithmetic mean, AM) and 57.5±2.0 Bq m⁻³ (geometric mean, GM) for ²²²Rn, and 318±368 and 162±3.7 Bq m⁻³ for ²²⁰Rn, respectively. For ²²⁰RnD, 67 dwellings were studied. The AM of the ²²⁰RnD equilibrium equivalent concentration was 3.8±3.3 Bq m⁻³ with a maximum value of 15.8 Bq m⁻³. On the basis of these results, the average annual effective doses to the local residents due to radon and thoron exposure were 1.44–4.62 mSv. Thoron contributes 12.9–56.6% to the total doses. Preliminary results show that there is a relation between ²²⁰RnD in air and ²³²Th in soil. The correlation factors of outdoor and indoor were 0.88 and 0.40. The ²³²Th activity content of Chinese soil is estimated to be about two times the world average. The traditional residential dwellings with soil construction are still common in China. Further investigations on the ²²⁰Rn level in these dwelling with the aim of dose reduction are proposed.     

Radon in Norwegian dwellings and the feasibility of epidemiological studies

Summary The results of a pilot study on radon in Norwegian dwellings are presented together with a discussion on the feasibility of an epidemiological study on the correlation between lung cancer and radon progeny exposure in dwellings. There are large variations in the mean radon concentration in Norwegian municipalities, and the population average indoor radon concentration is high (80–100 Bq m^–3). The large variations and high absolute values, together with excellent lung cancer and smoking habit data, make it feasible to conduct epidemiological studies based on representative exposure data in the Norwegian population.     

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 ²³⁸U, ²³²Th and ²²²Rn 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 ²¹⁸Po and ²¹⁴Po by bathers and working personnel inside the thermal stations studied were determined.     

Radionuclides content in grape molasses soil samples from Central Black Sea region of Turkey

The activity concentrations of radionuclides in grape molasses soil samples collected from Zile (Tokat) plain in the Central Black Sea region of Turkey were measured by using gamma spectrometer with a NaI(Tl) detector. Also, the concentrations of ²²²Rn in soil samples and air were estimated essentially taking the activity concentrations of ²²⁶Ra measured in soil samples. Grape molasses soil samples with calcium carbonate content are used for sedimentation for making molasses in this region. The average activity concentrations of ²³²Th, ²²⁶Ra, ⁴⁰K, and ¹³⁷Cs were found as 62 ± 2, 68 ± 3, 479 ± 35, and 8.0 ± 0.3 Bq kg^?1, respectively. The average concentrations of ²²²Rn in soil samples and air were estimated to be 50 kBq m^?3 and 144 Bq m^?3. From the activity concentrations, absorbed gamma dose rate in outdoor air (D), annual effective dose from external exposure (E_E), annual effective dose from inhalation of radon (E_I), and excess lifetime cancer risk (ELCR) were estimated in order to assess radiological risks. The average values of D, E_E, E_I, and ELCR were found to be 90 nGy h^?1, 110 μSv y^?1, 1360 μSv y^?1, and 4 × 10^?4, respectively.     

Measurements of radon activity concentration in mouse tissues and organs

The purpose of this study is to investigate the biokinetics of inhaled radon, radon activity concentrations in mouse tissues and organs were determined after mice had been exposed to about 1 MBq/m³ of radon in air. Radon activity concentrations in mouse blood and in other tissues and organs were measured with a liquid scintillation counter and with a well-type HP Ge detector, respectively. Radon activity concentration in mouse blood was 0.410?±?0.016 Bq/g when saturated with 1 MBq/m³ of radon activity concentration in air. In addition, average partition coefficients obtained were 0.74?±?0.19 for liver, 0.46?±?0.13 for muscle, 9.09?±?0.49 for adipose tissue, and 0.22?±?0.04 for other organs. With these results, a value of 0.414 for the blood-to-air partition coefficient was calculated by means of our physiologically based pharmacokinetic model. The time variation of radon activity concentration in mouse blood during exposure to radon was also calculated. All results are compared in detail with those found in the literature.     

Activity concentrations of222Rn,220Rn,and their decay products in german dwellings,dose calculations and estimate of risk

Summary Measurements of the concentrations of²²²Rn, its short-lived decay products and of²¹²Pb -²¹²Bi were performed in 150 dwellings and in the open air in the Federal Republic of Germany. The concentration of²²²Rn was measured by electrostatic deposition of²¹⁸Po. The concentrations of the short-lived decay products were measured by air sampling and alpha-spectroscopy. It was found that inside dwellings the average potential alpha-energy concentration of the short-lived daughters is about three times higher than in the open air. The total potential alpha-energy concentration indoors amounts to 2.6 · 10^–3 Working Level (W. L.). Direct measurements of the equilibrium factor inside dwellings gave a mean value of 0.3. A strong dependence of the potential alpha energy concentration on the ventilation rate in dwellings has been observed. These ventilation effects exceed the effects caused by differences in the activity concentrations due to different building materials.The dose calculation results in an average dose to the whole lung due to the inhalation of short-lived radon daughters of about 0.05–0.2 mGy/a. An estimate of risk - based on the risk factors for uranium miners - shows an average lifetime risk of about 6 · 10^–4 for the incidence of lung cancer caused by inhalation of radon and thoron daughters in dwellings in the Federal Republic of Germany.The research programme was supported by the Bundesminister des Innern of the Federal Republic of Germany     

Study of radon/thoron exhalation rate,soil-gas radon concentration,and assessment of indoor radon/thoron concentration in Siwalik Himalayas of Jammu & Kashmir

In the present study, the soil-gas radon concentration was assessed at different depth intervals, i.e., 15 cm, 30 cm, 60 cm, and 100 cm from the 30 villages of Jammu &; Kashmir, India using RAD7, an electrostatic solid state alpha detector. The radon mass exhalation and thoron surface exhalation rate has also been measured in the selected 18 soil samples out of 30 of different grain sizes (i.e., 1 mm, 300 µm, 150 µm). The active radon and thoron concentrations were also assessed in the 20 villages. Both the exhalation rates and active radon/thoron concentration were measured using SMART Rn Duo, a portable radon monitor. The average values of soil-gas radon concentration were 210 ± 84 Bq m^?3, 1261 ± 963 Bq m^?3, 4210 ± 1994 Bq m^?3, and 671 ± 305 Bq m^?3 at the depth intervals of 15 cm, 30 cm, 60 cm, and 100 cm, respectively. The exhalation rate of radon and thoron from soil was found to decrease with the increase of grain size, as smaller soil particles make relatively more contribution to radon and thoron exhalations from the ground surface than larger soil particles. The measured Pearson's correlation coefficient was obtained as statistically significant between different quantities under two-tailed test.     

Temporal variation of thoron decay product concentration in the atmosphere and comparison with radon decay product concentration

Seasonal and long-term variation of the airborne ²¹²Pb concentration, representative of the equilibrium equivalent concentration of thoron decay products (EEC_Rn220), was investigated from 1989 through 1996 at a semi-natural location in southern Germany. Continuous measurement yielded a long-term average concentration of 0.082 Bq m^–3, while daily mean concentrations varied from ≤0.01 to 0.34 Bq m^–3. An average annual effective dose of 1.4 mSv due to outdoor thoron progeny concen-tration was estimated. This is about 2% of the dose due to the average short-lived radon progeny concentration (EEC_Rn222) of 8.4 Bq m^–3 measured for this location in the same period. In most years the seasonal pattern of ²¹²Pb activity concentration in the atmosphere is characterized by two maxima: the first in May and the second one in September. Low concentrations are observed from November through February of each year. This is in contrast to the behaviour of the short-lived ²²²Rn progeny which exhibit enhanced concentrations exactly during these months. The most probable reason for the different temporal behaviour of ²¹²Pb is the extremely reduced flux of thoron gas from the ground during the winter months. Received: 19 August 1997 / Accepted in revised form: 22 January 1998     

Radiocesium decay in populations of brown trout and Arctic char in the alpine Atna area, south-eastern Norway

Some of the highest recordings of radioactive fallout from the Chernobyl accident in Norway were found in the south-eastern Oppland and Hedmark counties. Cesium content and decay rates were followed in populations of brown trout and Arctic char in Lake Atnsjøen over the years 1986–1995. These results were compared with samples for adjacent lakes to test for between-lake variabilities within the same region. The data on brown trout was compared with samples from a wider region, where more than 1800 individual samples of brown trout were collected from nearly 100 localities. Back-calculated initial activity per 1 January 1987 showed a strong regional and within-lake variability for these localities, ranging from 437 to 18000 Bq kg^–1 (average: 2416 Bq kg^–1), while trout and char from Atnsjøen had initial activities of 1259 and 1122 Bq kg^–1, respectively. Most of the other populations from the Atna region also had initial activities below the average (around 2000 Bq kg^–1). Ecological half-life for both brown trout and Artic char in lake Atnsjøen was close to 1.7 years (corresponding to a decay rate of 0.4 year), which was consistently lower than the 2.5 years average for the entire lake data set. Decay constants from linear regressions of total decay over time ranged from 0.15 to 0.28. For trout populations, a positive correlation was found between initial load and decay constants. Although trout and char clearly differ in their diet, no consistent differences were recorded in initial activities or decay rates for these two species in the Atna area.     

Estimation of dose rate for indoor radon from building materials

The internal dose rate due to indoor radon (Rn) emissions from building materials is estimated. It is observed that the contribution from building materials to the dose rate is very small. The average indoor radon concentration in 75 different rooms is found to be 55 ± 12 Bq. m^–3. Assuming an occupancy factor of 0.8, the annual average effective dose equivalent is 1.7 mSv. It seems that soil gas is mainly responsible for the internal exposure from indoor Rn.     

Comparison of antioxidative effects between radon and thoron inhalation in mouse organs

Radon therapy has been traditionally performed globally for oxidative stress-related diseases. Many researchers have studied the beneficial effects of radon exposure in living organisms. However, the effects of thoron, a radioisotope of radon, have not been fully examined. In this study, we aimed to compare the biological effects of radon and thoron inhalation on mouse organs with a focus on oxidative stress. Male BALB/c mice were randomly divided into 15 groups: sham inhalation, radon inhalation at a dose of 500 Bq/m³ or 2000 Bq/m³, and thoron inhalation at a dose of 500 Bq/m³ or 2000 Bq/m³ were carried out. Immediately after inhalation, mouse tissues were excised for biochemical assays. The results showed a significant increase in superoxide dismutase and total glutathione, and a significant decrease in lipid peroxide following thoron inhalation under several conditions. Additionally, similar effects were observed for different doses and inhalation times between radon and thoron. Our results suggest that thoron inhalation also exerts antioxidative effects against oxidative stress in organs. However, the inhalation conditions should be carefully analyzed because of the differences in physical characteristics between radon and thoron.

     

Comparative study of 222Rn/220Rn progeny concentration and estimation of age-dependent dose due to inhalation of radon progeny for different body organs

In the present study, the age-dependent doses due to inhalation of short lived decay progeny of radon, i.e., ²¹⁴Po to different body organs have been calculated for the inhabitants of the Jammu district, Jammu &; Kashmir, India. The estimated age-dependent doses for different body organs due to inhalation of radon progeny through air for all age groups varied between 0.002E-06 and 0.10 n Svy^?1 which were found to be well within the recommended limit of 1000 µ Svy^?1 (ICRP). The progeny concentration of radon and thoron was calculated and compared by two different techniques. The attached and un-attached progeny concentration of radon and thoron was calculated by using a passive time integrating, deposition-based technique. The measured attached and un-attached radon and thoron progeny concentrations have been cross-checked by on-line active technique, i.e., Flow-mode Integrated Sampler. A weak positive correlation has been observed between the two devices. The median value of un-attached fraction was found to be 0.15 and 0.12 for thoron and radon progeny, respectively and found to have a log-normal distribution. A good positive correlation has been observed between radon and thoron progeny concentrations.     

Lung dosimetry of inhaled radon progeny in mice

Biological response of exposure to radon progeny has long been investigated, but there are only few studies in which absorbed doses in lungs of laboratory animals were estimated. The present study is the first attempt to calculate the doses of inhaled radon progeny for mice. For reference, the doses for rats and humans were also computed with the corresponding models. Lung deposition of particles, their clearance, and energy deposition of alpha particles to sensitive tissues were systematically simulated. Absorbed doses to trachea and bronchi, bronchioles and terminal bronchioles, alveolar-interstitial regions, and whole lung were first provided as a function of monodisperse radon progeny particles with an equilibrium equivalent radon concentration of 1?Bq?m^?3 (equilibrium factor, 0.4 and unattached fraction, 0.01). Based on the results, absorbed doses were then calculated for (1) a reference mine condition and (2) a condition previously used for animal experiments. It was found that the whole lung doses for mice, rats, and humans were 34.8, 20.7, and 10.7?nGy (Bq?m^?3)^?1?h^?1 for the mine condition, respectively, while they were 16.9, 9.9, and 6.5?nGy (Bq?m^?3)^?1?h^?1 for the animal experimental condition. In both cases, the values for mice are about 2 times higher than those for rats, and about 3 times higher than those for humans. Comparison of our data on rats and humans with those published in the literature shows an acceptable agreement, suggesting the validity of the present modeling for mice. In the future, a more sophisticated dosimetric study of inhaled radon progeny in mice would be desirable to demonstrate how anatomical, physiological, and environmental parameters can influence absorbed doses.     

Quantitative health impact of indoor radon in France

Radon is the second leading cause of lung cancer after smoking. Since the previous quantitative risk assessment of indoor radon conducted in France, input data have changed such as, estimates of indoor radon concentrations, lung cancer rates and the prevalence of tobacco consumption. The aim of this work was to update the risk assessment of lung cancer mortality attributable to indoor radon in France using recent risk models and data, improving the consideration of smoking, and providing results at a fine geographical scale. The data used were population data (2012), vital statistics on death from lung cancer (2008–2012), domestic radon exposure from a recent database that combines measurement results of indoor radon concentration and the geogenic radon potential map for France (2015), and smoking prevalence (2010). The risk model used was derived from a European epidemiological study, considering that lung cancer risk increased by 16% per 100 becquerels per cubic meter (Bq/m³) indoor radon concentration. The estimated number of lung cancer deaths attributable to indoor radon exposure is about 3000 (1000; 5000), which corresponds to about 10% of all lung cancer deaths each year in France. About 33% of lung cancer deaths attributable to radon are due to exposure levels above 100 Bq/m³. Considering the combined effect of tobacco and radon, the study shows that 75% of estimated radon-attributable lung cancer deaths occur among current smokers, 20% among ex-smokers and 5% among never-smokers. It is concluded that the results of this study, which are based on precise estimates of indoor radon concentrations at finest geographical scale, can serve as a basis for defining French policy against radon risk.     

Biofiltration of waste gases with the fungi Exophiala oligosperma and Paecilomyces variotii

Two biofilters fed toluene-polluted air were inoculated with new fungal isolates of either Exophiala oligosperma or Paecilomyces variotii, while a third bioreactor was inoculated with a defined consortium composed of both fungi and a co-culture of a Pseudomonas strain and a Bacillus strain. Elimination capacities of 77 g m^–3 h^–1 and 55 g m^–3 h^–1 were reached in the fungal biofilters (with removal efficiencies exceeding 99%) in the case of, respectively, E. oligosperma and Paecilomyces variotii when feeding air with a relative humidity (RH) of 85%. The inoculated fungal strains remained the single dominant populations throughout the experiment. Conversely, in the biofilter inoculated with the bacterial–fungal consortium, the bacteria were gradually overgrown by the fungi, reaching a maximum elimination capacity around 77 g m^–3 h^–1. Determination of carbon dioxide concentrations both in batch assays and in biofiltration studies suggested the near complete mineralization of toluene. The non-linear toluene removal along the height of the biofilters resulted in local elimination capacities of up to 170 g m^–3 h^–1 and 94 g m^–3 h^–1 in the reactors inoculated, respectively, with E. oligosperma and P. variotii. Further studies with the most efficient strain, E. oligosperma, showed that the performance was highly dependent on the RH of the air and the pH of the nutrient solution. At a constant 85% RH, the maximum elimination capacity either dropped to 48.7 g m^–3 h^–1 or increased to 95.6 g m^–3 h^–1, respectively, when modifying the pH of the nutrient solution from 5.9 to either 4.5 or 7.5. The optimal conditions were 100% RH and pH 7.5, which allowed a maximum elimination capacity of 164.4 g m^–3 h^–1 under steady-state conditions, with near-complete toluene degradation.     

Radon sources and impacts: a review of mining and non-mining issues

Radon is a ubiquitous natural carcinogen derived from the three primordial radionuclides of the uranium series (²³⁸U and ²³⁵U) and thorium series (²³²Th). In general, it is present at very low concentrations in the outdoor or indoor environment, but a number of scenarios can give rise to significant radiological exposures. Historically, these scenarios were not recognised, and took many centuries to understand the links between the complex behaviour of radon and progeny decay and health risks such as lung cancer. However, in concert with the rapid evolution in the related sciences of nuclear physics and radiological health in the first half of the twentieth century, a more comprehensive understanding of the links between radon, its progeny and health impacts such as lung cancer has evolved. It is clear from uranium miner studies that acute occupational exposures lead to significant increases in cancer risk, but chronic or sub-chronic exposures, such as indoor residential settings, while suggestive of health risks, still entails various uncertainties. At present, prominent groups such as the BEIR or UNSCEAR committees argue that the ‘linear no threshold’ (LNT) model is the most appropriate model for radiation exposure management, based on their detailed review and analysis of uranium miner, residential, cellular or molecular studies. The LNT model implies that any additional or excess exposure to radon and progeny increases overall risks such as lung cancer. A variety of engineering approaches are available to address radon exposure problems. Where high radon scenarios are encountered, such as uranium mining, the most cost effective approach is well-engineered ventilation systems. For residential radon problems, various options can be assessed, including building design and passive or active ventilation systems. This paper presents a very broad but thorough review of radon sources, its behaviour (especially the importance of its radioactive decay progeny), common mining and non-mining scenarios which can give rise to significant radon and progeny exposures, followed by a review of associated health impacts, culminating in typical engineering approaches to reduce exposures and rehabilitate wastes.     

Long-term variation of outdoor radon equilibrium equivalent concentration

Long-term variation of outdoor radon equilibrium equivalent concentration was investigated from 1982 to 1992 at a semi-natural location 10 km north of Munich, southern Germany. For this period the continuous measurement yielded a long-term average of 8.6 Bq·m^–3 (arithmetic mean) and 6.9 Bq·m^–3 (geometric mean), from which an average annual effective dose of 0.14 mSv due to outdoor radon can be derived. A long-term trend of the radon concentration was not detectable over the whole period of observation. However, by time series analysis, a long-term cyclic pattern was identified with two maxima (1984–1986, 1989–1991) and two minima (1982–1983, 1987–1988). The seasonal pattern is characterized by an autumn maximum and an early summer minimum. On average, the seasonal maximum in October was found to be higher by a factor of 2 than the June minimum. The diurnal variation of the radon concentration shows a maximum in the early morning and a minimum in the afternoon. On average, this maximum is a factor of 2 higher than the minimum. In the long term a seasonal pattern was observed for diurnal variation, with an average diurnal maximum to minimum ratio of 1.5 in winter compared with 3.5 in the summer months. The radon concentration is correlated with a meteorological parameter (stagnation index) which takes into account horizontal and vertical exchange processes and the wash-out of aerosols in the lower atmosphere.Dedicated to Prof. F. Waschsmann on the occasion of this 90th birthday     

Stimulation of lymphocyte receptor capping by the ionophore monensin

Summary The carboxylic ionophore monensin has a biphasic effect on antibody-induced Thy-1 cap formation. At higher concentrations, 5×10^–6–5×10^–5 m monensin causes a significant inhibition of receptor capping similar to that previously found with the Ca²⁺ selective ionophore A23187. At lower concentrations, 5×10^–8–5×10^–7 m capping is stimulated. It is concluded that capping at lower ionophore concentrations is a secific response to the ability of monensin to induce a rise in intracellular Na⁺, which indirectly elevates intracellular Ca²⁺ activity. This in turn activates the contractile machinery required for the aggregation of surface receptors into capped structures. At higher concentrations monensin acts as a nonspecific detergent, which causes detrimental structural alterations in some of the membrane components involved in the capping process.