During 2001–2017 more than 800 thousand records containing the results of measurements of radon concentration taken in 78 regions of Russia were accumulated in the Federal databank of radiation doses to the population of the Russian Federation. The paper presents the procedure and results of the first data analysis carried out to check the conformity of radon concentrations in the regions of Russia with the lognormal distribution and to calculate the parameters of these distributions. The procedure included verification and validation of data, plotting the frequency distribution histograms and Q-Q plots (normal probability plots) and the use of some methods of elimination of plateaus on the Q-Q plots and the distribution recovery. As a result, in 74 of 78 analyzed regions radon concentrations conform quite well or almost perfect to a lognormal distribution up to a certain level (this level ranged from 55 to 4915 Bq/m3). For all 78 regions geometric means with 95% confidence intervals, geometric standard deviations and arithmetic means were calculated. It should be noted that due to the fact that the Federal databank is a database containing results of measurements taken with different techniques (instant measurements, charcoal canisters, radon monitors and etched track detectors), the lognormal distributions for most regions are in fact contaminated distributions, and currently it is impossible to calculate the parameters of separate distributions that form the mixture. The results show that dose assessment based on arithmetic means could lead to an  overestimation of the doses from radon up to 2.1 times compared to that based on geometric means. The calculated medians can also be used for risk assessment purposes.

According to the analysis of requests for methodological assistance to the Saint-Petersburg Research In ­stitute of Radiation Hygiene after Professor P. V. Ramzaev, measurements of radon concentration (or radon EEC) in existing operated public buildings (primarily children institutions) in the framework of surveillance actions in the regions of the Russian Federation, as a rule, are taken according to Guidelines MU 2.6.1.2838-11, intended for radiation control of public buildings only when they are put into operation after construction, major repairs or reconstruction, due to the absence of special guidelines. Compliance with the requirements of paragraph 6.5 of MU 2.6.1.2838-11 means that the building and premises are in a state that is not equal to their normal operation mode. Registration of high values of indoor radon concentration in this case leads to management decisions, including administrative suspension o f activities for up to ninety days, i.e. the closure of individual premises or even the entire building of a children institution. The consequences of making such decisions may include an increase in social tension in society and provoking radiophobia among the population. The paper presents specific recommendations for the radon survey for existing operated public buildings with non-round-the-clock stay of people, which are based on the results of the analysis of the experience of practical application of various methods of measuring indoor radon concentrations in such buildings in order to assess average radon concentration during working hours in the normal operation mode. The proposed approach can be further used as the basis for developing special guidelines for radiation control of existing operated public buildings with non-round-the-clock stay of people.

The article presents summary information about modern approaches to risk assessment of radoninduced lung cancer caused by exposure to radon of the population and by radon's short-lived daughter decomposition products in residential and public buildings. It is pointed out on the importance of radonprotecting measures in children's school and preschool institutions. As the example for applying of risk assessment models as an instrument for the effectivness of implemented measures, the results of calculation of lifetime attributable risk before and after radon protection in one of the school of St. Petersburg have been introduced.

The paper presents the results of a refined calculation of the average individual annual effective doses to the population of the regions of Russia from exposure to the cosmic radiation. The population-weighted average values of the altitude and latitude of the main settlements, which are home to at least 50 percent of the population of the region, were used as the altitude and latitude of the region. In addition, all settlements with a population of at least 20 thousand people were included in the calculation. Coverage of the population of the regions of Russia in the calculation varies from 50.1 to 95.8 percent (excluding three cities of Federal importance with 100 percent coverage) with the average value of 62.4 percent. The number of settlements included in the calculation in different regions ranges from 1 to 63. The methodology of the dose calculation is based on the approach described in the UNSCEAR 2000 Report. The obtained dose values for different regions range from 0.310 to 0.413 mSv. For Russia as a whole country, the population-weighted average individual annual effective dose from exposure to the cosmic radiation is 0.338 mSv.

An extensive radon survey was conducted in 2008-2011 in the framework of the Federal target program on the territory of 29 districts of Chelyabinsk Oblast. SSNTDs were used to measure indoor radon concentrations in public buildings, dwellings and industrial buildings. The results are stored in the database “Radon” owned by Research and Technical Center of Radiation-Chemical Safety and Hygiene of Federal Medical-Biological Agency. The paper presents the results of the analysis of spatial variability of indoor radon concentration and the relationship of this value with a set of geological predictors of radon potential of the territory integrated into a map of ecological and radiogeochemical zones. The results show that in all districts and the whole Chelyabinsk Oblast radon concentrations conform to a lognormal distribution, but in ten districts log-logistic distribution fits the data slightly better. Nevertheless, relative difference between the median values of indoor radon concentration calculated from the two fitted distributions yields zero. The results show that dose assessment based on the arithmetic means could lead to an overestimation of the doses from radon in 1.4 times on average compared to that based on the medians. The median value does not exceed 400 Bq/m3 in any of the surveyed territories and the 95th percentile lies between 96 and 1274 Bq/m3. The fraction of indoor radon concentrations above 400 Bq/m3 expected from the fitted distribution lies between less than 0.1 and 26.8%. The highest values of this fraction were obtained for the Sosnovsky, Kaslinsky, Bredinsky districts and the Miassky urban district (except for the city of Miass). A map of ecological and radiogeochemical zones in Chelyabinsk Oblast was released in 1993-1995 and it was based on a set of geological predictors of radon potential of the territory. We analyzed the relationship of these zones with the results of the radon survey. One-way ANOVA on ranks with the Bonferroni correction showed that there is no statistically significant difference at the 95% confidence level amongst the medians of indoor radon concentration on basement, ground and first floors in settlements, which are located on the territory of three of four of these zones and outside of the territory of all zones. In the fourth zone the median was even two times lower than outside of the zones. These results lead to the conclusion that the possibility of using this map as a map of radon-prone areas is very doubtful. Each datapoint stored in the “Radon” database has a number of additional properties, which allows analyzing other types of indoor radon concentration variability such as seasonal or floor-to-floor. It is expected that later this dataset could be used for estimating regional seasonal correction factors.