RADON-PRONE AREAS IN SLOVAKIA PREDICTED BY RESCALED RADON POTENTIAL MAPS.

Several scientific studies have shown that high content of radon in the soil environment can be a precursor of increased indoor radon levels. Inhabited areas where elevated indoor radon concentration appears for natural (geogenic) reasons are commonly referred to as radon-prone areas. In this study, radon-prone areas in the Slovak Republic were predicted on the basis of radon potential maps after its specific rescaling. In total, 99 municipalities have been identified in Slovakia where the annual average indoor radon concentration is expected to exceed the reference level of 300 Bq m-3; five of those are even expected to exceed 1000 Bq m-3. In these municipalities it is then required to conduct a survey of indoor radon measurements. Compared with a nationwide survey, the proposed approach of searching for houses with potentially high radon exposure is more efficient.

INFLUENCE OF AIRWAY GEOMETRY ON RADON RISK ASSESSMENT IN ADULTS AND CHILDREN (MICRODOSIMETRIC APPROACH).

The aim of this work was to use the microdosimetric threshold energy model to study the effects of alpha-emitting 222Rn progeny on the probability of developing lung cancer. The results suggest that the radiation risk may increase by several times as the thickness of the surface layer decreases. The thicker the protective mucus layer and the deeper the sensitive target cells are located in the tissue, the less radiation damage the same dose produces. These findings have been applied to children of various ages. As children grow older, their lungs enlarge, the mucus layer thickens and the cells sensitive to radiation damage move deeper into the lung tissue, resulting in a reduction of radiation risk. The fraction of affected target cells is not only a function of dose but also of lung tissue depth. The results indicate that children can be several times more vulnerable to radiation than adults.

ANALYSIS OF TIME SERIES OF RADON ACTIVITY CONCENTRATION IN OUTDOOR AIR AND THEIR RECONSTRUCTION.

222Rn (radon) is an ever-present radioactive component of the surface layer of the atmosphere. The knowledge of the shape of radon activity concentration (RAC) time series has several important applications in atmospheric studies. This study presents the results of RAC analysis according to Garzon et al. approach during the years 1991-2009, as well as attempts to reconstruct the shape of composite diurnal RAC cycles using either Garzon et al. original approach or other methods. From this study, it follows that in order to accurately reconstruct the mean diurnal RAC cycles for individual months in our locality (Central European region), the parameters have to be calibrated by local RAC and measured global solar radiation data. The original Garzon et al. approach underestimates the amplitude of mean diurnal RAC cycles during April-August by up to 10%, and overestimates the amplitude during September-March by up to 25%.

Radon as a Tracer of Lung Changes Induced by Smoking.

After smoking, exposure to radon and its progeny is the second leading cause of lung cancer. The probability of inducing lung carcinomas by inhaled radon progeny depends on the deposited radiation dose, and is significantly affected by physiological and morphometric changes induced by smoking. Due to irritation of the airways, the inhalation of cigarette smoke leads to the hyperproduction of mucus. Two concurrent processes occur: on one hand, increased production of mucus protects the target cells against radiation damage; on the other hand, in the case of long-term smokers, a chronic lung obstruction develops, causing an increase in the radiation dose to the lungs. Depending on the duration and intensity of smoking, these processes contribute to the final radiation dose with different weights. The primary objective of this study was to investigate to what extent these smoke-induced changes can modify the resulting absorbed dose of inhaled radon progeny relative to healthy nonsmokers. Since the bronchial dose depends on the degree of lung tissue damage, we have used this dose as a tool for detecting the effects of smoking on the lung epithelium. In other words, the biological effect of radon served as a tracer of changes induced by smoking.

LUNG REGENERATION IN ABSTAINING SMOKERS.

Smoking modifies morphological and physiological parameters of the lungs. Due to the irritation of airways, the natural self-cleaning ability of the lungs is impaired. The mucus accumulates in the airways and various infections develop, leading to chronic bronchitis. After the cessation of smoking, the lungs of the smoker start to heal and regenerate. Cilia in the lungs start to grow again and cleanse the lungs, thus reducing the risk of infection. The regeneration of the lungs takes a long time and depends on the degree of lung damage due to smoking. The aim of this study was to reconstruct the evolution of this regeneration process in chronic smokers by using the biological effects of radon and its decay products. Thus, radon in this study served as a tracer of changes induced by smoking.

DEVELOPMENT AND TESTING OF DEVICES FOR CONTINUOUS MONITORING OF RADON ACTIVITY CONCENTRATION IN WATERS.

Continuous radon measurement in waters is an appropriate tool for the study of its variations as well as for the clarification and understanding of the factors that cause these changes. In addition, sudden changes in radon activity concentration (RAC) in groundwater can be used to identify geodynamic activities and earthquake predictions. In this paper, two measuring systems for continuous monitoring of RAC in waters are presented and tested. One of them was designed for water sources with a high yield; the second one operates with a constant volume of a sample using a different method of 222Rn release from water. We present our first laboratory tests of continuous measurement of RAC in tap waters as well as the variations of RAC observed during a week.

On the relation between outdoor 222Rn and atmospheric stability determined by a modified Turner method.

In practice, information about atmospheric stability is often obtained from discrete stability classes determined from routine meteorological observations. However, changing concentrations of the radioactive gas 222Rn present in the atmosphere are also considered a good indicator of vertical dispersion and atmospheric stability. A complex, in-depth analysis between these different approaches of atmospheric stability assessment has not been performed so far, and was the main motivation behind this study. The study presents atmospheric radon data measured in Bratislava (Slovakia) and stability indexes (SI) calculated according to a modified Turner method during a period of one year. Basic features of the diurnal and seasonal variations of these variables are discussed. It was found that the time series of radon activity concentration (RAC) lags approximately 5 h behind that of the Turner stability classes adjusted for temperate climate regions. Various time lags were also identified between RAC and meteorological variables used to determine the stability classes. Evaluation of seasonal trends revealed a low variability of mean monthly values of stability classes compared to the variability of mean monthly values of RAC. Another notable difference between RAC and stability indexes was found - while the stability index can both increase and decrease with wind speed, concentration of outdoor radon was never observed to increase with increasing wind speed. In spite of the mentioned discrepancies, the time series of RAC and SI are generally in a good agreement. This is especially true if one compares the deviations of RAC and SI from their mean daily values, when the differences in their seasonal variability are eliminated. Deviations of RAC can be used to calculate diurnal variations of stability indexes. Analysis of a complete year of data also revealed a roughly linear relationship between average values of RAC and calculated stability indexes, because in large datasets random processes tend to cancel each other out.

RADIATION EXPOSURE OF THE POPULATION FROM 222Rn AND OTHER NATURAL RADIONUCLIDES AROUND MOCHOVCE NUCLEAR POWER PLANT, SLOVAKIA.

In this article, the effective dose to the population from natural sources of ionizing radiation in the vicinity of Mochovce nuclear power plant in Slovakia is presented. All major contributions to the effective dose were taken into account, including the contributions from gamma radiation of soil and rocks, cosmic radiation, and indoor and outdoor radon and thoron. On the basis of recent indoor radon measurements in Slovak cities and publicly available data about radon concentration in the soil air, a roughly linear relationship was found between these variables. Consequently, the annual effective dose from indoor radon and thoron was conservatively estimated. For the area of interest, a map of conservatively estimated potential effective doses was created. For the villages in the vicinity of Mochovce, the conservatively estimated effective dose to the population from natural sources ranged from 5.4 to 14.6 mSv, which is four orders of magnitude higher than the contribution of radioactive discharges from Mochovce nuclear power plant.

Long-term variations of radionuclides in the Bratislava air.

Variations of aerosol radionuclides (2001-2015) in the ground-level air in Bratislava (Slovakia) showed 7Be maxima in spring/early summer and minima in winter, however, an inverse trend was observed for 210Pb, 137Cs and 40K. A decreasing amplitude and splitting of summer maxima for 7Be in the last years has been found. A temporal behavior of the 7Be/210Pb activity ratio showed higher levels during warm seasons due to vertical convection of air masses from higher altitudes. The 137Cs activity concentration in the surface air between 2003 and 2010 was decreasing with an effective half-life of 1.9 ± 0.3 years. The yearly average 137Cs concentrations during 2009-2014 were almost constant, disturbed only by the Fukushima accident in 2011. The increased atmospheric 137Cs and 40K levels observed during the autumn-winter season may be due to surface soil resuspension, biomass burning and radionuclide transport by winds. Seasonal variations of 222Rn activity concentrations were found with maxima at the end of autumn and in winter, and minima in spring. The variability of the average annual course of 222Rn has been larger than that of 210Pb. The 210Pb/222Rn activity ratio was highest at the end of winter and in the spring, while from June to December remained nearly constant. More intensive atmospheric mixing in spring months caused a decrease in the 222Rn activity concentration, while the aerosol component of the atmosphere has been affected mainly during the autumn and winter seasons. The mean residence time of aerosols in the atmosphere was calculated using the 210Pb/222Rn method to be 4.5 ± 0.9 days.

Daily and seasonal variations in radon activity concentration in the soil air.

Radon activity concentration in the soil air in the area of Faculty of Mathematics, Physics and Informatics (FMPI) in Bratislava, Slovak Republic, has been continuously monitored since 1994. Long-term measurements at a depth of 0.8 m and short-term measurements at a depth of 0.4 m show a high variability in radon activity concentrations in the soil. The analysis of the data confirms that regular daily changes in radon activity concentration in the soil air depend on the daily changes in atmospheric pressure. It was also found that the typical annual courses of the radon activity concentration in the soil air (with summer minima and winter maxima) were disturbed by mild winter and heavy summer precipitation. Influence of precipitation on the increase in the radon activity concentration in the soil air was observed at a depth of 0.4 m and subsequently at a depth of 0.8 m.

Results of outdoor radon monitoring in Bratislava and Nováky.

Measurements of radon activity concentration (RAC) were made in two localities of Slovakia. The first one is located on the campus of Comenius University in Bratislava, where radon has been monitored since 1991. The second area is situated in the city of Nováky (midwest Slovakia, ∼150 km from Bratislava). The localities have a different orography. RAC was measured continuously by large-volume scintillation chambers. The outdoor air was sampled at a height of 1.5 m above the ground. Time courses of RAC in both localities have a similar character. The correlation coefficients between RAC in Bratislava and Nováky was quite high (R(2) = 0.45). However, RACs in Nováky were found out to be about two times higher (∼12.1 Bq m(-3)) than in Bratislava.