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Indoor radon exposure is the largest contributor to population dose from natural sources. Radon as a natural radioactive gas could accumulate to harmful levels in buildings, such as homes and buildings with public access. In order to assess the exposure due to radon in school the results of indoor radon measurements in 55 state school buildings in 7 municipalities located in one district in southern Bulgaria are considered in this paper. The survey was carried out with passive CR-39 etched track detectors. Radon concentrations ranged from 17 to 868 Bq m–3 , with a geometric mean of 117 Bq m–3 and a geometric standard deviation of 1.78. The findings revealed that in 30% of the measured buildings the radon concentration was higher than the national reference level of 300 Bq m–3 . The statistically significant difference in indoor radon concentrations between municipalities (KW, р < 0.001) was obtained. The research was also focused on parameters affecting radon concentration levels such as type of room and floor location. The estimated annual effective dose of 0.39 to 1.07 mSv y–1 , applying the ICRP and UNSCEAR methodology, was calculated for students. The results of the measurements were provided to the administrative authorities and measures were proposed to improve the air in school buildings with high radon levels.

The exposure to radon in buildings open to the public and at workplaces depends on many factors, for example, forms of utilization, construction conditions, time of exposure, heating, and ventilation conditions, etc. To evaluate the radon exposure in different working environments, continuous simultaneous measurements of radon (CRn), equilibrium equivalent (EEC), and potential alpha energy (PAEC) concentrations for 24 hours were performed using AlphaE for CRn and DOSEman PRO from SARAD GmbH for EEC and PAEC measurements. The study considered measurements at three locations in the radon-rich spa of Narechen, Asenovgrad, and at an old mine turned museum in the town of Pernik. A comparison was made between the average values of the concentrations relating to all-day and only working hours when the measurements were completed. The CRn increases during the working hours in the museum as well as in the bath of the spa, while it decreases in the spa’s treatment room. On the other hand, the EEC and PAEC are increasing at all locations. The concentrations increasing due to working hours, which are integrated into long-term measurements can cause underestimated radon exposures in radon reach working environment.

Mineral springs are used in spa resorts throughout the world. Radon is a natural radioactive source, which can dissolve, accumulate, and be transported by water. This study investigates the radon concentration in air and water in 12 Bulgarian rehabilitation hospitals and presents the assessment of the exposure to radon in them. The measurements were performed at 401 premises within 21 buildings, using two types of passive detectors for a dry and wet environment that were exposed from February, 2019 to June, 2019. The radon concentration varied from 19 to 2550 Bq/m3 with an arithmetic mean and a standard deviation of 102 Bq/m3 and 191 Bq/m3, respectively. The hypothesis that in hospitals the source of radon, besides soil under the buildings, is also the mineral water that is used for treatment, was tested. Thermal water samples were procured sequentially from a spring and baths to analyse the reduction of radon concentration in them till reaching the premises. The results show that the concentration of radon decreased by approximately 50%. Further, the correlation analysis applied to the data proved the relation of the levels of indoor radon in the treatment rooms with those in the water. Mineral water used in rehabilitation hospitals have radon transfer coefficients ranging from 4.5·10− 4 to 8.4·10− 3. In addition, an analysis of the exposure of patients and workers to radon in rehabilitation hospitals based on the indoor radon levels and period of exposure was performed.

Radon exposure at schools may have a considerable public health impact. The exposure and respectively the health risk is related with CRn and time. The schools are buildings with public access, where the children spent long period of life. The main objective of the study is to evaluate the indoor radon concentrations as an important air pollutant in school buildings of Kardzhali districts, Bulgaria, as a first step in controlling and reducing the children exposure. The measurement of radon concentration was made in 437 occupied rooms, situated on underground, ground and first floor, of 55 state school buildings in 7 municipality of the district. The arithmetic and geometric means of radon concentrations are 140 and 117 Becquerel per cubic meter respectively. In 51 rooms, the radon concentrations were higher than 200 Becquerel per cubic meter while in 28 rooms of 17 school buildings, it exceeds the national reference level of 300 Becquerel per cubic meter. The statistically significant difference in indoor radon concentrations between municipalities was obtained. The effect of: type of room, floor, building year of construction and energy efficiency measures in building, on the indoor radon concentration was considered for analysis as well. The values of the radon concentration in the buildings where energy efficiency measures have been implemented are higher than those where they have not been performed.

The objective of this study was to evaluate the indoor gamma dose rate in 17 inspected hospitals for rehabilitation where the radon measurements were conducted and to give a more comprehensive evaluation of the total exposure dose. The gamma dose rate in the air was measured in 355 rooms in 17 inspected hospitals for rehabilitation on the territory of Bulgaria. The maximum parameter value was 0.390 μSv/h and the minimum value was 0.06 μSv/h with the 0.157 μSv/h arithmetic mean (standard deviation - 0.160). The gamma dose rate was within the natural variations of the parameter in buildings. Direct measurements of radon were conducted, and the results ranged from 12 Bq/m3 to 3920 Bq/m3. The relationship between the two parameters was examined. A weak correlation between gamma dose rate and indoor radon concentration was found. The measurement of a gamma dose rate could be a useful parameter for carrying out radon workplace control.

Chronic inflammation is a common denominator linking a wide range of health conditions, including tissue response to radiation exposure. This pilot study investigates whether inflammatory cytokines—interleukins IL-6, −8, −10, monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor α (TNFα)—can be used as early biomarkers of radiation-induced adverse health effects in occupationally exposed individuals. The study included 33 workers externally exposed to gamma radiation from the nuclear industry with cumulated doses from 0.11 to 190 mSv and 42 non-exposed controls of comparable age and socio-economic status. IL-6, IL-8, MCP-1, TNFα and IL-10 were analyzed by enzyme-linked assay (ELISA) in blood plasma samples. Total antioxidant status (TAS) of blood plasma was determined by a colorimetric assay. The radiation-exposed and control groups measured significantly different levels of MCP-1, TNFα and IL-10. Seventy-five percent of radiation workers had either high MCP-1 levels or low IL-10 levels and 30% had all three cytokines dysregulated. Approximately 50% of workers showed upregulated antioxidant status, which appeared to compensate the pro-inflammatory cytokine shift in these individuals. In contrast, only 2% of the control subjects were found to have three dysregulated cytokines, and all of them measured within the normal TAS range. The present study may represent an important step towards the establishment of a reliable set of biomarkers for health-risk estimation in population cohorts exposed to low radiation doses.

The main purpose of this paper is to analyse the activities for Radon Risk Communication under the National Radon Program and to outline the main objectives in the new Radon Action Plan for developing a communication strategy. The preliminary activities were implemented under the National Radon Program. Survey via the Internet for assessment of perceptions and the level of knowledge regarding radon was conducted as a benchmark for evaluation of public awareness. The main channels which were used to inform the population were publications on websites, magazines, in TV interviews and radio (local), seminars, from which the most widely used were local seminars. On the basis of this, six objectives are proposed for a new radon action plan: to obtain wide organisational support and to determine the need of risk communication; to develop goals for risk communication with key messages to different target groups; to form and to train the communication team; to evaluate the stakeholders and the communication channels; to develop plans with different organisations for different focus groups; to evaluate the radon risk communication programme.

The aim of the present study is to assess the effects of low-dose occupational exposure on T helper response. One Hundred five employees working in Nuclear Power Plant, Kozloduy, Bulgaria and control group of 32 persons are included in this investigation. Flow cytometry measurements of T-cell populations and subpopulations and natural killer T cells are performed and levels of G, A, and M immunoglobulins and interleukin 2 (IL-2), IL-4, and interferon γ were determined. The data interpreted with regard to cumulative doses, length of service, and age. The results of the present study are not enough to outline a clear impact of occupational radiation exposure on T helper populations. Nevertheless, the observed even slight trends in some lymphocyte’s populations and in cytokines profile give us the reason to assume a possibility of a gradual polarization of T helper 1 to T helper 2 immune response at dose range 100 to 200 mSv. The results of the present study indicate the need to perform a more detailed epidemiological survey including potential confounding and misclassifying factors and possible selection bias that could influence the results.

h The purpose of this article is to analyze the results of a 10-year survey of the radiation effects of some immune parameters of occupationally exposed personnel from the Nuclear Power Plant “Kozloduy”, Bulgaria. 438 persons working in NPP with cumulative doses between 0.06 mSv and 766.36mSv and a control group with 65 persons were studied. Flow cytometry measurements of T, B, natural killer (NK) and natural killer T (NKT) cell lymphocyte populations were performed. Data were interpreted with regard to cumulative doses, length of service and age. The average values of the studied parameters of cellular immunity were in the reference range relative to age and for most of the workers were not significantly different from the control values. Low doses of ionizing radiation showed some trends of change in the number of CD3+CD4+ helper-inducer lymphocytes, CD3+ CD8+ and NKT cell counts. The observed changes in some of the studied parameters could be interpreted in terms of adaptation processes at low doses. At doses above 100–200 mSv, compensatory mechanisms might be involved to balance deviations in lymphocyte subsets. The observed variations in some cases could not be attributed only to the radiation exposure because of the impact of a number of other exogenous and endogenous factors on the immune system.

Analysis of performed rescue operations during previous nuclear and radiation accidents highlights several problems impacting the quality of emergency response: unsatisfactory preparation of the population and the medical profession for action in extreme circumstances; presence, along with pure radiation damage, of varied spectrum of psychological side effects. According to the authors, in order to reduce the health risk for the affected people, preliminary preparation and training is required. This publication presents a training concept, together with related levels and means of realization.

A 10-year survey of immune status of nuclear power plant (NPP) workers was assessed by cellular and humoral immune parameters. The cumulative doses of NPP workers were in the range of 0.06 to 766.36 mSv. The results did not show significant deviations in the studied parameters of cellular and humoral immunity, but a tendency of elevated values in CD3+4+ helper inducers cells, especially its CD4+62L+ subpopulation, regulatory CD4+25+ cells, CD8+28+ cytotoxic subpopulation, and immunoglobulin M, was established. The observed trend of the above-mentioned parameters could be interpreted by assumption that while the adaptation processes are dominated with low prevalence of T-helper (Th) 1 immune response to cumulative doses less than 100 mSv, a switch to Th-2 response occurred at doses above 100 mSv. The impact of a number of other confounding factors on the immune system does not allow definitive conclusions about the direct radiation-induced changes in immune parameters.

The aim of the study is to assess the health status of Kozloduy Nuclear Power Plant personnel in association with their occupational exposure to low doses of ionising radiation (IR) as well as with other factors of their working environment and to determine the probability of the occupational exposure to be a reason for the diagnosed malignant diseases (Probability of Causation – PC). More than 1000 occupationally exposed workers and nonexposed administrative staff have been studied during 1993–2008. No statistically significant variation in the average cumulative dose was found between the healthy people and the persons with at least one disorder. The highest rate of morbidity was registered in persons with doses up to 1 mSv. The analysis of parameters of peripheral blood showed that at occupational lowdose exposure the haemopoietic system completely preserves the tri-linear cell proliferation capacity of the bone marrow. The analysis of results of PC demonstrated that this is spontaneously arising malignant diseases, regardless of condition of work.

This paper describes the studies that were carried out to establish the available resources of the hospitals situated near to Bulgarian NPP 'Kozloduy' to perform medical treatment of casualties in mass radiation accidents. Special attention has been paid to evaluate the possibility to perform first aid and triage to the victims, radiation monitoring procedure and decontamination. The expert view on the sets of criteria for assessing the ability of hospitals to participate in emergency response is given. We also studied the awareness and training of medical staff. The results of the studies were taken into account in the last updating of the national emergency action plan for nuclear accident.

This paper describes changes in Bulgarian legislation concerning the health monitoring of occupationally exposed individuals to ensure the radiation safety and protection of radiation workers. The expert view on the implementation of health monitoring programmes to different occupational groups and assessment of health risk, including molecular-epidemiological analyses, is given. Special attention is focused on the prevention of significant social diseases and the promotion of a healthy lifestyle. A computerised national health register for persons who are working or have worked with ionising radiation in Bulgaria is proposed and some aspects in the national legislation requiring changes in order to answer the challenges of the time are discussed.