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The study presents the analysis of the results for indoor radon concentration in the kindergartens of two Bulgarian districts. The study presents the analysis of indoor radon concentration results in kindergartens of two Bulgarian districts. Measurements were performed with a passive method for the period from February to May 2015, in 411 children’s rooms situated in 157 kindergartens. The measured radon concentrations in the children’s rooms were between 10 and 1087 Bq per m. The evaluation of the results showed that in 10% of the kindergarten rooms, the radon concentration is above the national reference level of 300 Bq per m. The influence of the presence of a basement and the implementation of building renovation on the radon concentration were examined. The presence of a basement is a prerequisite for reducing the concentration of radon in the building. It has been proven that renovating the building increases the radon concentration in it. The analysis confirms the necessity of measuring the indoor radon concentration before the renovation and repair of the building, especially the implementation of energy efficiency measures.

Bulgaria is a country in the eastern part of the Balkan Peninsula, in South-eastern Europe. The presence of many mountains and karst areas is a prerequisite for a large number of caves in the country, but only some of them are managed and accessible to tourists. The purpose of the study is continuous measurement of radon concentration in six popular Bulgarian tourist caves (Bacho Kiro, Magura, Venetsa, Saeva dupka, Snejanka, and Uhlovica), and analysis of the diurnal variation. The direct, continuous radon measurements were performed with TERA (TSR4) system (Tesla, Czech Republic). 29 radon concentration time series were considered for evaluation of radon variations during the day and night. The period of the measurement was the autumn of 2019, and only one cave (Bacho Kiro Cave) was measured during the winter. The measurements were performed at different points (gallery, halls, or other cave formations) in each of the caves. The average diurnal radon concentration in the different caves varied from 531 Bq m−3 (Magura cave) to 5472 Bq m−3 (Venetsa cave). The variation of radon concentration between distinct places in most caves was approximately 1–2 k Bq m−3. No significant difference in radon concentrations was observed between night and day in a 24–96 h period measurement. The large fluctuations between the values measured at the entry (10–640 Bq m−3) and exit (165–927 Bq m−3) compared to those inside the cave were found only in cave Magura. The radon exposure of workers and visitors was assessed, using long-term measurements in the caves, based on the ICRP recommendation.

The pandemic caused by the COVID -19 virus has affected human health, consequently the health system and health services, both worldwide and in the Republic of North Macedonia. The idea for this research was therefore to examine the impact of the conditions imposed by the pandemic on the visits of the Emergency medical service in Skopje.For this purpose, the frequencies of visits with transport to hospital and just visits, as well as the frequencies of emergency calls and calls only for transport in the periods: before the pandemic (March 2019-February 2020) and during the pandemic (March 2020 to February 2021) were analyzed. The overall number of visits was further analyzed by categories: age and gender.In the period from March 2019 to March 2021, a total of 49,930 visits were performed, of which 24,115 were performed during the pandemic and 25,815 before. In the same period, a total of 13,835 emergency calls were answered, of which 6,434 were during the pandemic and 7,401 before; a total of 9780 calls for transport of patients were carried out, during the pandemic 5602 and 4178 before the pandemic. The analysis showed that the number of transports was increased and the number of emergency calls decreased during the pandemic compared to the pre-pandemic period, while the number of visits during and before the pandemic did not differ significantly. Concerning age and gender, the analysis showed that the number of visits to children, men aged 20 to 40 and women over 60 years was significantly reduced compared to pre-pandemic visits, while there was no difference in other age groups. The contributions of visits related to certain diagnostic and a particular age group are discussed in this paper.We found that the pandemic has not influenced the pace of work, apart from the conditions, only the association between the kind of calls and the diagnoses for which the visits were made has practically changed. During the pandemic, most visits for males and females over 40 were related to COVID diagnosis, while for children, men and women under 40, accidents were the most common cause

Bulgaria is rich in geothermal water. The radon level in spas buildings depends on soil underneath, thermal water and the ventilation conditions. The aim of the paper is to analyses influence of ventilation system on indoor radon in air in the spa buildings. Direct measurements of radon in the air were performed in treatment rooms (treatment with thermal water and without) and mineral pools. A statistically significant difference was found between the indoor radon levels in treatment rooms using water and those without water, located in branches with high radon concentration (MW, p = 0.032). The spectra of the rooms for 24 hours were considered for analysing the indoor radon daily variations. The radon arithmetic mean value in rooms with operating ventilation system was 148 Bq /m3, and in those without - 756 Bq /m3 and the statistically difference is significant (MW, p

The production of phosphoric acid from natural phosphate ore generates an industrial waste product named phosphogypsum. Phosphogypsum contains considerable amounts of natural radionuclides from the 238U chain, originating from the ore but enriched during the technological process. In order to perform radiological characterization of the “HIV” (Chemical Industry Veles) phosphogypsum stockpile, five phosphogypsum samples were collected and analyzed. The mean values of gross alpha and beta specific activities ± standard deviation values were: (950±104) Bq/kg and (1694±220) Bq/kg, respectively. Further analysis showed increased gross activities of radionuclides of the 238U chain, while the radionuclides of the 232Th chain and 40K were below the detection limit. The mean values of the specific activities of 238U and 226Ra were (360±55) Bq/kg and (280±84) Bq/kg, respectively. The estimated annual outdoor effective dose, at 1m received by adults was 0.25 mSv/y, which is below a dose limit of 1 mSv/y for members of general public. The results obtained in this study show that radionuclides, although present in relatively high concentrations in the phosphogypsum pile, do not imply an increased external radiation risk for members of the population. The possible use of phosphogypsum in civil construction and agriculture may not be excluded if conditions of prior good planning taking into account the radionuclides activities exist.

The long–term measurements of radon and thoron equilibrium equivalent concentrations (EERC and EETC) were carried out the first time in Republic of Srpska in 25 schools of its capital Banja Luka and in its wider surroundings. After this successful survey, the measurements continued using the same type of the LR 115 nuclear track detectors, i.e., Direct Radon Progeny Sensors/Direct Thoron Progeny Sensors (DRPS/DTPS), and they were deployed in the 36 dwellings nearby the investigated schools. The detectors were exposed for one year period at 15–20 cm distance from the walls. The EERC and EETC were found to vary in the range from 6.3 to 14.4 Bq/m3 and from 0.10 to 1.1 Bq/m3 , with geometric mean 9.3 and 0.36, respectively. The same variance of EER and EET concentrations, measured in living and bedrooms of buildings built with different construction materials as well at different floors have been obtained. The insignificant correlations between EERC and EETC, show that these concentrations appeared to be independent in investigated dwellings. The calculated ratio of EETC to EERC ranged from 0.01 to 0.16 with the geometric mean of 0.04. The aim of this study is to give possible scientific contribution considering the explanation of EERC and EETC behavior in an indoor environment.

Учебникот е наменет за студентите по медицинските науки. Неговата основна цел е да ги објасни концептите на биофизиката на човечкиот организам како и физичките основи на некои медицински дијагностики и тераписки методи. Содржината е организирана, според областите на физиката, во седум тематски целини: механика на цврсто тело, механика на флуиди, звук, транспортни процеси, електрични и магнетни појави, оптика и јонизирачки зрачења. За разбирање на текстот, доволни се основни предзнаења стекнати од кое било средно образование. Секоја тема содржи поглавја структурирани така што се почнува од физиката, потоа биофизиката на одреден дел од телото и на крај медицинската дијагностика и терапија. За секое биофизичко толкување на одреден процес се вклучени неопходните елементарни објаснувања од анатомијата и физиологијата. Одредени процеси во човечкиот организам се анализирани и квантитативно. По неколку примери во секоја тема го илустрираат пристапот, применувајќи исклучително алгебра и тригонометрија. Напредокот на медицинската дијагностика и терапија, меѓу другото, се должи и на примена на физичките методи. Некои од нив, со нивните предности и ограничувања, се објаснети во соодветните теми. Во согласност со наставната содржина, биофизиката е основа за разбирање, првенствено на физиологијата и патофизиологијата, но понатаму и за радиологијата, нуклеарната медицина, физикалната терапија и радиотерапијата. Пишувањето учебник е работа која бара сериозен пристап, особено кога станува збор за мултидисциплинарна наука како што е биофизиката. Имајќи предвид дека повеќето од студентите по медицински науки не се премногу мотивирани за физика, пишувањето беше голем предизвик. Учебникот претставува преработка на мојата претходно објавена скрипта по биофизика, направена врз основа на согледувањата на резулатите од проверките на знаењата на студентите. Некои од појавите се изземени од учебникот, а некои се дообјаснети со голем број примери и илустрации. На крајот од секоја тема се вклучени и примери за самостојна проверка на знаењето.

The work of the factory for the production of fertilizers in the area of Veles (Republic of North Macedonia) resulted in a residual amount of approximately 3.4 million tons of phosphogypsum, which was deposited at the dump adjacent to the plant between 1980 and 2003. So far, no remediation of the phosphogypsum dump has been performed. This paper presents the results obtained from representative samples taken from the phosphogypsum dump by applying the following methods: analytical methods (ICP-MS, FUS-ICP-MS), mineralogical methods, X-ray powder diffraction (powder-XRD), electron microscopy (SEM-EDS), and high-resolution γ-ray spectrometry. The samples contain crystalline gypsum (Ca-sulphate), Fe-hydroxide, Ba-sulphate, Ca-fluoride, Si-oxy-hydroxide and zircon.The gross alpha specific activities varied between 820 Bq/kg and 1090 Bq/kg with an average of 950 ± 104 Bq/kg, while the gross beta specific activities ranged from 1380 Bq/kg to 1980 Bq/kg with an average of 1694 ± 220 Bq/kg.

The most abundant and efficient source of air ionization in the lower layer of the atmosphere is radon. As an alpha emitter, radon plays cruciant role in the earth atmospheric electricity. Besides physical, radon and ions have a significant biological role concerning human health: radon is health hazard while the ions are beneficial ingredient of the air we breathe. Measurements were made using continual radon monitor Rad-7 and air ion counter CDI-06. Diurnal and spa¬tial variations of both atmospheric constitutens are mutually related and dependant mo¬stly on radon exhalation potential, meterological parameters, aerosol con¬cen-tra¬ti¬on and formation of temperature inversion layer. Indoor concentrations are re¬la¬ted to radon accumulation and partiallz influenced by external radon concentration

The long-term measurements of radon and thoron equilibrium equivalent concentrations (EERC and EETC) were carried out the first time in Republika Srpska in 25 schools of its capital Banja Luka and in its wider surroundings. After this successful survey the measurements continued using the same type of the LR115 nuclear track detectors, i.e., Direct Radon Progeny Sensors/Direct Thoron Progeny Sensors (DRPS/DTPS), which were deployed in the 36 dwellings nearby the investigated schools. The aim of this study was to give possible scientific contribution considering an explanation of EERC and EETC behavior in indoor environment. The detectors were exposed for one year period at 15–20 cm distance from the walls. The EERC and EETC were found to vary in the range from 6.3 to 14.4 Bqm−3 and from 0.10 to 1.1 Bqm−3, with geometric mean 9.3 and 0.36, respectively. The same variance of EER and EET concentrations, measured in living and bedrooms of buildings built with different construction materials as well at different floors, have been obtained. The insignificant corre¬lations between EERC and EETC, shows that these concentrations appeared to be independent in investigated dwellings. The calculated ratio of EETC to EERC ranged from 0.01 to 0.16 with the geometric mean of 0.04.

Radon (222Rn) and thoron (220Rn) are natural radioactive gases, generated in the terrestrial materials. They are the main sources of public exposure to ionising radiation in indoor environment worldwide. Differences in half-lives of 222Rn (T1/2=3.8 d) and 220Rn (T1/2=55.6 s) lead to its different indoor behavior. Se¬ve¬ral studies of indoor 222Rn and 220Rn in Northern Macedonia have been per¬for¬med, starting with measurements in dwellings in 2008 and continuing with mea¬su¬re-ments in schools during 2012. The surveys in the Republic of Srpska began later (in 2011) with the simultaneous 222Rn and 220Rn measurements in the dwellings and schools of Banja Luka cities. This paper, as a result of our coop¬eration, su¬m-ma¬rizes the results and general conclusions obtained from 222Rn and 220Rn mea¬su-re¬ments in schools of capitals. In both cities, the measurements were made using Raduet - nuclear tracer detectors; deployed at distances: >0.5m (Skopje) and 0.2m (Banja Luka); and exposed in a period: March 2012 - May 2012 (Skopje) and April 2011 -May, 2012 (Banja Luka). Results for 222Rn and 220Rn concentrations in both cities have a log-normal distribution. The 222Rn geometric mean value of 71 Bq/m3 in Skopje are higher than in Banja Luka city (GM = 50 Bq/m3). Among other factors that affect 222Rn variations, this difference could be related to the different exposure time of detectors. Furthermore, the dispersion of the 222Rn results in each city expressed through geometric standard deviation is relatively low: GSD = 2.13 (Skopje) and GSD = 2.11 (Banja Luka) indicating re¬la¬ti-vely homogeneous data sets. The 220Rn concentrations in Banja Luka (GM = 51 Bq/m3) were higher than in Skopje (GM = 11 Bq/m3). It is obvious that in the case of 220Rn, the exposure pe¬ri¬od did not play a significant role. One of the reasons for this difference could be the position of the detectors as well as the different buil-ding materials in the sch¬o¬ols. On contrary, the dispersion of the 220Rn results in Skop¬je (GSD = 3.38) was greater than in Banja Luka (GSD = 2.07).

As a very mountainous country, Bulgaria has a lot of caves, but only some of them are developed, managed and available for tourist visits. The main sources of radon are rocks and a high concentration can be measured in caves. Caves have been of interest because radon concentration in these environments may sometimes reach high values. A rather large number of investigations have been carried out all over the world, from the point of view of both researches on radon behavior in a cave environment and radiation protection. There are no systematic investigations of radon in the caves in Bulgaria in order to assess the health risk. The paper presents the sample design of the radon concentration survey in Bulgarian caves for the evaluation of the health risk of people. The sample design covers the method of selection, the sample structure and the plan for analyzing and interpreting the results. The method selected to define the representative sample corresponds to the following criteria: it covers all types of caves in different mountains in Bulgaria; it is consistent over time; it includes changes to the definition over time; it constitutes the selection of the sample design for the caves and organization of survey. The samples of caves are defined on the basis of mountains in Bulgaria in order for the definitions to remain constant over time. Groups of caves according to the mountains are: caves in Stara Planina, caves in Rhodope Mountains and caves in other mountains. The design of the samples of caves is built around a random selection from the most visited caves in Bulgaria. According public information, there are 65 of these caves. The calculated sample size for a confidence level of 95% and a margin of error of 30% is 10 caves. The numbers of samples have been weighed according to the percent of the caves in the groups with 5 per cent precision at 95 per cent confidence. The way of the selection of the sample and the measurement method is presented in the paper.

This study discusses the sampling frames of the buildings with public access to radonconcentration surveys on the territory of Bulgaria in order to assess the health risk for the population.The sampling frame is the list from which the sample is selected, so the quality of the sampling frameaffects the quality of the sample. The general list of different types of buildings with public access hasbeen prepared in accordance with the list of the Ministry of the Regional Development and PublicWorks in Bulgaria and international experience in the field of radon investigation. The types ofbuildings with public access have been classified in nine general groups. These groups of buildingswith public access are defined as follows: educational institutions; buildings for commerce and/orservices; health and social care buildings; buildings in the field of culture; sports facilities; buildingsin the field of transport; prisons; cult and religious buildings and post offices. Multicriteria analysiswas applied to select the types of buildings in order to assess the health risk from radon exposure inbuildings with public access. The main criteria for the analysis are: the probability of high radonconcentration; time spent in building and the number of people accessing the place. For the purposeof the precise definition of the target buildings, it is necessary to ensure that the all the places wherethe population could be exposed to radon are adequately covered. To define the whole list of thetarget buildings, the official available information has been used from: the Ministry of Education andScience for the schools and universities; Ministry of Health for the hospitals and polyclinics; Ministryof Culture for the theatres, cinemas and museums and the Ministry of Tourism for hotels, caves, etc.

In the last decade, many studies have been made for measuring natural radioactivity in regions of the Republic of Macedonia. However, the information on terrestrial radiation exposure, and, consequently, risk assessment were not available. In this study, a risk assessment was done considering a specific activity concentration of 137 Cs in the topsoil. The results indicate that the external gamma doses due to natural radionuclides in soils are higher than those of 137 Cs. The absorbed dose rate in air varies in intervals: from 4.3 to 57 nGy/h (due to Ra); from 3.9 to 88 nGy/h (due to 232 Th); from 3.3 to 58 nGy/h (due to 40 K); and from 0.01 to 5.3 nGy/h (due to Cs). In addition, the mean annual effective doses due to natural radionuclides and 137 Cs in the soils of the Republic of Macedonia are estimated to be 78 μSv and 1.01 μSv, respectively. As well as, the values of external hazard index H ex indicate in general low gamma radiation risk for populations living in the Republic of Macedonia. 226 226 137 Ra, 232 Th, 40 K and

To establish baseline values of concentrations of terrestrial radionuclides for the Republic of Macedonia, a survey covering the entire territory was performed. 213 soil samples were collected from regions around the major settlements and cities, about evenly distributed over the geotectonic units which constitute the country’s geological foundation. The specific activities of radionuclides were measured by gamma spectrometry. The values were in ranges: (8-1390) Bq kg-1 for 40K, (9-123) Bq kg-1 for 226Ra, (9-111) Bq kg-1 for 238U and (7-145) Bq kg-1 for 232Th in dry soil. The relation between specific activities of natural radionuclides and geology was investigated. Correlation between radionuclides, which may serve as additional geochemical indicators, and geology could not be found convincingly. Mutual correlations between 226Ra, 238U and 232Th activities were found to be high (Spearman  about 0.8), whereas the ones between these and 40K are a bit lower, somewhat above =0.6.

The paper deals with the analysis of the annual indoor radon concentrations variations due to different geological parameters of Sjenica community, Western Serbia. The measured 222Rn concentrations were ranging from 10 to 1130 Bq/m3. In 14% of the buildings, the radon action level of 300 Bq/m3 is exceeded, indicating that Sjenica community could be characterized as a radon priority area. Each of 35 measuring location was georeferenced and corresponding lithostratigraphic units and geological period was assigned. Data were analyzed using the multiple linear regression (MLR) method and two predictive models were developed. The MLR model generated by the geological periods explained 17% of the radon variability while, the better one, was the lithostratigraphic MLR model, which explained 52% of the radon variability. Analysis has shown that lithostratigraphic units are important parameters in the prediction of radon levels. © 2019 Carpathian Journal of Earth and Environmental Sciences.

Производството на фосфорна киселина од природни фосфатни карпи го зголемува индустрискиот отпад наречен фосфорен гипс. Фосфорниот гипс содржи значително количество радионуклиди од серијата 238U, поради нивната висока концентрација во фосфатните руди. За време на активностите на Хемиската индустрија Велес, во периодот од 1979 до 2003 година, складирани се 3,7 милиони тони фосфорен гипс во депонија. Таа се наоѓа на околу 1,5 km југозападно од комплексот на фабриката, во долина помеѓу ридови, на територија од 70,000 m². Со цел да се изврши радиолошка карактеризација на депонијата, се зедоа пет примероци на фосфорен гипс и се испратија на анализа во Activation laboratories во Канада. Вкупните алфа- и бета-активности се мереа со пропорционален систем на броење; специфичните активности на 40K, 232Th и 238U се мереа со гамаспектометрија, а производите од распадот на серијата 232Th and 238U се анализираа радиохемиски. Вкупните алфа-специфични активности варираат помеѓу 820 Bq/kg и 1090 Bq/kg, со просек од 950±104 Bq/kg, додека вкупните бета-специфични активности се со ранг од 1380 Bq/kg до 1980 Bq/kg, со просек од 1694±220 Bq/kg. Сите вредности на вкупните алфа- и бета-специфични активности индицираат зголемена радиоактивност. Понатамошната анализа на радионуклидите, исто така, го потврдува овој факт. Гама-спектометриската и радиохемиската анализа покажуваат дека зголемената активност доведува до формирање на радионуклиди од серијата 232Th и 40K, кои се под лимитот за детекција. Овие специфични активности ± вредности на стандардна девијација, со опсег во загради на 238U, 2226Ra, 214Pb и 214Bi во Bq/kg е 360±55 (300-400), 280±84 (300-400), 350±45 (300-400) и 380±45 (300-400), соодветно. Надворешниот и внатрешниот радиолошки ризик исто така беше пресметан. Земајќи ја предвид надворешната зафатнина од 0,2 фактор годишно и 0,7 Sv Gy-1 фактор на конверзија од дозата апсорбирана во воздухот до ефективната доза што ја прима возрасно лице, се доби средна вредност од 0,25 mSv/y, која е под лимитот од 1 mSv/y за јавноста (1). Се пресмета и внатрешниот ризик (2,3) во случај на употреба на фосфорен гипс како градежен материјал. Пресметаните алфа (Iα = 1,4) и бета (Iβ = 1,3) индекси се над 1, што е ниво за безбедно користење. Резултатите добиени од оваа студија покажуваат дека радионуклидите, и покрај тоа што се присутни со висока концентрација во фосфорниот гипс, не покажуваат значителни надворешни дози за јавноста, додека, доколку се користи фосфорен гипс како градежен материјал, може да се зголеми внатрешната изложеност. Се препорачува понатамошно испитување на ефектот на депонијата на животната средина.

Quantification of uranium in human urine is a valuable technique for assessing occupant and public exposure to uranium. Human hair and nails can be considered as bio-indicators of the public exposure to certain natural radionuclides and toxic metals over a long period of months or even years. All urine, hair and nail samples were collected from a population of both sex aged from 40 to 87 years in Niška Banja (227 km south of Belgrade) with a high level of natural radioactivity (HLNRA), a suburban municipality of Serbia which located in the quaternary alluvium of River Nišava along the contact of the Koritnik limestone and travertine rock. Air dose rate in indoor environment has been measured. To assess and monitor the public exposure, urine samples for each subject (24 h period) were collected and concentration of uranium was analyzed using alpha-particle spectrometry. After addition of radioactive tracer U-232 and concentrated nitric acid, samples were evaporated to dryness. Residues were wet ashed with nitric acid and H2O2, radiochemical separation of uranium radioisotopes were performed by extraction chromatography using UTEVA resin. Uranium concentration in hair and nail samples from same subjects were analyzed using inductively coupled plasma mass spectrometry. Uranium concentrations in hair, nail and urine varied from 0.2 to 77.1 ppb, 2.5 to 44.7 ppb, 54-730 ppb respectively. There was a large variation and may be due to geological origin and anthropogenic activities., 9th International Conference on High Level Environmental Radiation Areas-For Understanding Chronic Low-Dose-Rate Radiation Exposure Health Effects and Social Impacts (ICHLERA 2018)

The main contribution to the population exposure is due to radon and thoron progenies and not radon and thoron itself. Nevertheless, due to the simplicity and cost effectiveness of radon/thoron measurements compared to the measurements of their progenies, effective doses are usually estimated from the measured Rn/Tn concentrations with the assumed value of equilibrium factor. In this paper, an overview of direct measurements of radon and thoron progenies is some parts of Balkans performed within the framework of large international collaboration is given. In this joint venture, long-term measurements were carried out in dwellings and schools using direct radon progeny sensors/direct thoron progeny sensors (DRPSs/DTPSs). Large scale Rn/Tn progeny survey was performed using 321 DRPSs/DTPSs detectors in the period from 2011 till 2013 encompassing some parts of Serbia: 125 dwellings in the region of Soko Banja (Southern Serbia), 48 dwellings in Kosovo, 44 schools in FYR of Macedonia and 37 dwelling and 25 schools in Republic of Srpska. The detectors were deployed from 3 months up to one year, since long term measurements are essential for assessing inhalation doses to the public. In case where possible seasonal variations were discussed as well. Effective doses were estimated from measured equilibrium equivalent radon and thoron concentrations (EERC and EETC) considering different occupancy factors for inhabitants and pupils.

Radon is a natural radioactive gas present in each indoor environment. Its harmful health effect is confirmed in many epidemiological studies. In the Republic of Macedonia, since 2008 intensive survey of radon measurements in dwellings have been started and continued with measurements in schools in 2012. Survey of indoor radon concentration in dwellings and schools of Republic of Srpska started in 2011, in Banja Luka city. In this paper, we present only the results of measurements performed in primary schools of Skopje and Banja Luka cities. In both cities, the radon measurements were performed with different types of detectors, but for this paper, the only measurements by the Raduet detector were used. Comparing the 222Rn results it can be concluded: Arithmetic means are higher than geometric mean values indicating log normal distributions; The values in Skopje are higher than in Banja Luka city. Considering a number of factors that affect radon variations, there are many reasons for differences. One of them is the different exposure time of the detectors. On the other hand, the dispersion of the results in each city expressed through the geometric standard deviation is relatively low indicating relatively homogeneous factors. Comparing the 220Rn it can be concluded: Arithmetic means are higher than geometric mean values indicating log normal distributions; The values in Banja Luka are higher than in Skopje. It is obvious that in the case of 220Rn, the exposure period does not play a significant role. One of the reasons for this difference could be the position of the detectors as well as different building materials in the schools. The dispersion of the results in Skopje is greater than in Banja Luka.

Quantification of uranium in human urine is a valuable technique for assessing occupant and public exposure to uranium. Human hair and nails can be considered as bio-indicators of the public exposure to certain natural radionuclides and other toxic metals over a long period of months or even years.All urine, hair and nail samples were collected from a population of both sex aged from 40 to 87 years in Niška Banja (227 km south of Belgrade) with a high level of natural radioactivity (HLNRA), a suburban municipality, of Serbia which located in the quaternary alluvium of River Nišava along the contact of the Koritnik limestone and travertine rock. Air dose rate in indoor environment has been measured. To assess and monitor the public exposure, urine, hair and nail samples were collected to analyze the concentration of uranium, using inductively coupled plasma mass spectrometry and alpha-particle spectrometry. Uranium was determined in 24 h samples. After addition of radioactive tracer U-232 and concentrated nitric acid, samples were evaporated to dryness. Residues were wet ashed with nitric acid and H2O2, radiochemical separation of uranium radioisotopes were performed by extraction chromatography using UTEVA resin.Source preparation for alpha-particle spectrometry was carried out by the micro-coprecipitation method with neodymium fluoride.U concentrations in hair, nail and urine varied from 0.2 to 77.1 ppb, 2.5 to 44.7 ppb, 54-730 ppb respectively.There was a large variation and may be due to geological origin and anthropogenic activities.