Indoor radon concentrations in kindergartens in three Bulgarian districts.

This article examines the results of a study of radon concentrations in kindergartens in three districts of north-western Bulgaria. For the period from December 2019 to May 2020, passive radon measurements were accomplished in 1490 premises of 130 kindergartens. The highest arithmetic mean (AM) value of 219 Bq m-3 and geometric mean (GM) value of 156 Bq m-3 radon concentration were found in the state kindergartens of the Vratsa district. The radon values for the remaining two districts are as follows: Lovech-AM = 156 Bq m-3 and GM = 114 Bq m-3; Montana-AM = 125 Bq m-3 and GM = 88 Bq m-3. The effects of various factors on the radon concentration including district, year of building construction, presence of basement, place of premise, wall, and floor interior covering materials, and presence of a ventilation system were investigated. Factor Analysis was used to assess the combined effects of those factors on indoor radon concentration. The results revealed three combinations of the investigated factors: the first combined the district in which the kindergartens were located and the materials used for the floor of the premises, the second combined the year of construction of the building and the presence of a building foundation, and the third combined the rest of the investigated factors. It is concluded that a regional assessment of predictors of radon variability is needed. The walls in kindergartens should not be covered by gypsum, and floors should not be made from materials that can easily develop cracks such as terra cotta. The installation of a ventilation system reduces the radon concentrations in the premises, which is of particular importance in cases where the measured value is above the national reference levels.

Indoor radon concentration in state schools of four Bulgarian districts.

Indoor radon concentrations were surveyed in 230 public schools in four Bulgarian districts for the period November/December 2019 to May/June 2020. The measurements were carried out in 2427 rooms on the basement, ground floor and first floor using the passive track detectors of the Radosys system. The estimated arithmetic and geometric means with standard deviations were 153 ± 154 and 114 Bq/m3 (geometric standard deviation (GSD) = 2.08), respectively. The results are higher than those referred from the National Radon Survey in dwellings. In 9.4% of the rooms, the radon concentrations were above the reference value of 300 Bq/m3. The difference between indoor radon concentrations in the districts was significant, which proves its spatial variation. The hypothesis that the applied energy efficiency measures increase indoor radon values in buildings was confirmed. The surveys demonstrated the importance of indoor radon measurements in school buildings, in order to control and reduce children's exposure.

Analysis of indoor air pollution with radon in the kindergartens of two Bulgarian districts.

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.

Analysis of exposure to radon in Bulgarian rehabilitation hospitals.

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. The doses of workers do not exceed the limit of the annual effective dose for the population from all sources (1 mSv/year).

Inflammatory profile dysregulation in nuclear workers occupationally exposed to low-dose gamma radiation.

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.

Impact of Low-Dose Occupational Exposure to Ionizing Radiation on T-Cell Populations and Subpopulations and Humoral Factors Included in the Immune Response.

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.

RADON RISK COMMUNICATION IN BULGARIA.

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.

Assessment of Some Immune Parameters in Occupationally Exposed Nuclear Power Plants Workers: Flowcytometry Measurements of T, B, NK and NKT Cells.

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.

Assessment of Some Immune Parameters in Occupationally Exposed Nuclear Power Plant Workers: Flow Cytometry Measurements of T Lymphocyte Subpopulations and Immunoglobulin Determination.

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.