The paper (in two parts) presents an overview of the new guidelines MR 2.6.1.0333-23 (approved on 01 December 2023) that supersede guidelines MU 2.6.1.2838-11, which were used for organizing radiation surveys of residential, public and industrial buildings and facilities and their sanitary assessment in terms of radiation safety indicators over the past 12 years. Due to a large number of critical comments on the document received during this period, a need for significant revision emerged. The scope of the revised document was expanded, and now it covers all stages of the life cycle of buildings and facilities: commissioning; operation period; overhaul and reconstruction; demolition. In the second part of the paper, numerous innovations are considered in terms of estimating the indoor average annual equilibrium equivalent concentration of radon isotopes. The reasons for the introduction of certain changes are outlined. Based on the results of previous studies and the review of foreign recommendations, the procedures for measuring indoor radon concentrations have been improved in such a way as to balance the increase in the reliability of estimating the average annual equilibrium equivalent concentration of radon isotopes and the increase in time and labor costs for testing laboratories to conduct the survey. The revised document introduces separate procedures for measuring indoor radon concentrations in new buildings and existing buildings with round-the-clock and non-round-the-clock occupancy. Estimating a weighted average based on the results of two-season measurements will represent a significant step forward in assessing the actual average annual radon concentrations in operated buildings in Russia. At the same time, the case of radiation survey of the buildings within the framework of events with legally limited duration is considered separately in the revised document. Taken together, the changes should have a positive impact on the quality of measurement information obtained by testing laboratories and underlying decisions made by executive authorities.

The paper presents the results of analysis of the Ivanovo Regional databank of radiation doses to the pub-lic from exposure to natural and technologically enhanced radiation background for 2008–2022. Despite the fact that the average individual annual effective dose of public exposure due to natural sources of radiation in the Ivanovo region calculated for the whole 15-year period (4.63 mSv/year) does not qualify as increased (i.e. does not exceed the level of 5 mSv/year), in some years of the period under review the average dose repeatedly exceeded this level, reaching 7.50 mSv/year. The analysis of the structure of the doses of public exposure due to natural sources of radiation in the Ivanovo region showed that the contribution of the dose from internal exposure to radon, thoron and progenies according to measurement results from 2008–2022 ranged from 65.98 to 81.47%. The paper provides examples of buildings of different types in settlements of the Ivanovo region, in which the indoor radon isotopes equilibrium equivalent concentrations are more than 1.5 times higher than the established action level for existing dwellings and public buildings (200 Bq/m3). Despite the significant amount of measurement data in the Regional databank, it is necessary to obtain additional information on the indoor radon levels in existing wooden and other low-rise dwellings and public buildings in the most radon-prone areas of the region. For this purpose, a radon survey is planned for 2024-2026 in the cities of Ivanovo and Kohma, Privolzhsky, Gavrilovo-Posadsky, Teykovsky and Zavolzhsky districts of the Ivanovo region within the framework of a joint project of Saint-Petersburg Research Institute of Radiation Hygiene after Professor P.V. Ramzaev, the Directorate of the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing in the Ivanovo region, and the Center of Hygiene and Epidemiology in the Ivanovo region.

The paper (in two parts) presents an overview of the new guidelines MR 2.6.1.0333-23 (approved on 01 December 2023) that supersede guidelines MU 2.6.1.2838-11, which were used for organizing radiation surveys of residential, public and industrial buildings and facilities and their sanitary assessment in terms of radiation safety indicators over the past 12 years. Due to a large number of critical comments on the document received during this period, a need for significant revision emerged. The scope of the revised document was expanded and now covers all stages of the life cycle of buildings and facilities: commissioning; operation period; overhaul and reconstruction; demolition. In the first part of the paper, the structure and legal status of the new guidelines are considered, as well as the main innovations in terms of measuring the ambient dose equivalent rate of gamma radiation, searching and identifying local radiation anomalies and sites of radioactive contamination, measuring surface contamination levels, and determining the minimum number of premises to be surveyed. The reasons for the introduction of certain changes are outlined. The issues of evaluation of measurement uncertainty, reporting of measurement results and registration of test reports are covered in detail. In the second part of the paper, numerous innovations will be considered in terms of estimating the indoor average annual equilibrium equivalent concentration of radon isotopes.

A comprehensive radiation survey of settlements in six districts of the eastern part of the Orenburg region in terms of exposure to natural sources of ionizing radiation, carried out in 2019, revealed numerous exceedances of the hygienic norm (action level) for indoor radon concentration in residential and public buildings. It was found that among other studied factors, exhalation of radon from the ground under the buildings is the main source of high levels of public exposure. Due to the lack of funding for the continuation of the survey in 2020, specialists of St. Petersburg Research Institute of Radiation Hygiene after Professor P.V. Ramzaev, Directorate of Rospotrebnadzor in the Orenburg region and the Center of Hygiene and Epidemiology in the Orenburg region needed to develop new approaches to survey planning. These new approaches should provide maximum amount of measurement information necessary to ensure radiation safety of the region’s population, with minimal financial investments and labor costs. Indoor radon concentration in residential and public buildings was undoubtedly chosen as the studied factor, and the integrated measurement method using SSNTDs was chosen as the most suitable method for the objectives of the survey due to its scalability and ease of detectors deployment. Since exposure to radon and its progeny is the second leading cause of lung cancer after smoking, the selection of priority districts of the region for the radon survey was based on average standardized trachea, bronchi, and lung cancer morbidity rates in the districts of the Orenburg region for 2009-2018. The survey conducted in 2020-2023 revealed exceedances of the hygienic norm (action level) for indoor radon concentration in five of seven surveyed districts. By 2025 it is planned to conduct radon surveys in three more districts of the Orenburg region with increased respiratory systems cancer morbidity rates.

According to Rosstat statistics, in recent years there has been a tendency in the Russian Federation to increase the intensity of construction, while both the number of buildings put into operation and their total area are increasing. The assessment of the potential radon hazard of land plots for construction provides the possibility of timely inclusion of the necessary protective (preventive) measures against radon in the design of buildings. This is a legal requirement in cases where the density of radon flux from the ground surface within the building area exceeds the established hygienic standards (action levels). The paper presents a review of Russian and foreign approaches to assessing the potential radon hazard of land plots conducted within the framework of engineering and environmental surveys. The current regulatory requirements to radiation safety indicators of land plots for construction of residential, public and industrial buildings and facilities in the Russian Federation are analyzed. The main drawbacks of the algorithm for determining the potential radon hazard of land plots, used in the current guidelines MU 2.6.1.2398-08 approved at the federal level more than 15 years ago, are described. Critical remarks (the unsuitability of the value of density of radon flux from the ground surface for designing radon protective and mitigation (remedial) measures, lack of consideration of seasonal variations of radon flux density, etc.) accumulated over the years as a result of practical application of these guidelines are presented. Benefits and drawbacks of foreign approaches to assessing the potential radon hazard of the territory based on the results of measurements of radon concentration in soil gas, as well as the very possibility of a transition in Russian regulations from the density of radon flux from the ground surface to the radon concentration in soil gas, are analyzed. Some rational proposals of various Russian research teams on improving the algorithm for determining the potential radon hazard of land plots are considered.

The paper presents comments, remarks and opinions on the material presented in the publication “Radon regulation crisis in Russia: scale of the problem and proposals for remediation” by Tsapalov A., Miklyaev P., Petrova T., Kuvshinnikov S., published in the Russian peer-reviewed journal “ANRI” (“Radiation measurement equipment and news”), 2024, No. 1.

The paper presents the estimated doses to the population of six eastern districts of the Orenburg region, Russia, based on the results of a comprehensive radiation survey conducted in 2019 in 34 settlements with previously found elevated levels of activity concentration of natural radionuclides in tap water from ground water sources of drinking water supply. It is shown that the average individual annual effective dose due to all natural sources of ionizing radiation in 18 of 34 settlements corresponds to ‘elevated level’ of exposure due to natural sources according to established classification (from 5 to 10 mSv/year), and in another 7 settlements to ‘high level’ (over 10 mSv/year) with radon being the main contributor to the dose. Four settlements of Kvarkensky and Adamovsky districts, where the highest indoor radon concentrations had been found, were selected for a detailed survey, which included measurements of density of radon flux from the soil, radon concentration in soil gas, activity concentration of natural radionuclides in samples of building materials and in soil samples, and activity concentration of radon in tap water from groundwater sources of drinking water supply. Results of the detailed survey proved that the main source of radon in the buildings was the soil gas infiltration; compared to it, the contribution of waterborne radon release was insignificant.

The paper presents results of a comprehensive radiation survey conducted in 2019 in six districts of the eastern part of the Orenburg region in 37 settlements with previously found elevated levels of activity concentration of natural radionuclides in tap water from groundwater sources of drinking water supply. The survey included measurements of indoor radon concentrations and EEC in residential and public buildings, as well as measurements of ambient dose equivalent rate of gamma radiation indoors and outdoors. The survey revealed that annual average indoor radon EEC in many residential buildings in 23 settlements and public buildings in 25 settlements exceeded the hygienic norm (action level) of 200 Bq/m3 adopted in Russia for existing buildings. The highest values of annual average indoor radon EEC were obtained in residential buildings in Novovinnitskoe (1242 Bq/m3), Bratslavka (987 Bq/m3) and Anikhovka (942 Bq/m3) in Adamovsky district, and in public buildings in Kvarkeno (2291 Bq/m3) in Kvarkensky district, Karabutak (1114 Bq/m3) and Novovinnitskoe (923 Bq/m3) in Adamovsky district. The established hygienic norms in terms of ambient dose equivalent rate indoors and outdoors were not exceeded in the surveyed settlements. Results of the survey showed that the main reason for high indoor radon concentrations in residential and public buildings in the settlements of the eastern part of the Orenburg region is not related to the usage of tap water from groundwater sources of drinking water supply with elevated levels of activity concentration of natural radionuclides.

The article deals with the issues of normative and methodological support of radiation survey of buildings and structures to be demolished. It is noted that with the intensive growth of construction of dwellings and public buildings in large cities, former industrial territories with a significant number of facilities to be demolished are being included into the development zone. The radiation monitoring and sorting of industrial waste generated after the demolition of buildings is not feasible in practice. The expediency of radiation survey of buildings and structures to be demolished at the stage preceding their dismantling, as well as the need to develop and approve at the federal level the methodology of its implementation is substantiated. Recommendations for the assessment of radiation safety indicators of buildings and structures to be demolished are given. It is shown that if the value of ambient equivalent gamma dose rate in the buildings and structures to be demolished does not exceed 0.6 μSv/h, industrial waste generated after demolition of buildings and structures and containing only natural radionuclides are not a subject to any restrictions related to the radiation factor, since the value of effective activity concentration of natural radionuclides is guaranteed not to exceed 1500 Bq/kg and therefore the waste is classified as Category I in accordance with the Basic sanitary rules for the provision of radiation safety (OSPORB 99/2010).

According to the annual information packet “Radiation exposure doses to the population of the Russian Federation”, internal exposure to radon has been the main contributor to the annual dose for the population for many years. The paper presents results of a comparative assessment of doses and health risks for students (pupils) and employees of four educational institutions in the Kingiseppsky district of the Leningrad region due to exposure to radon and its progeny. Evaluation of the doses and risks was based on results of instant and long-term measurements of indoor radon concentrations published earlier. Individual annual effective doses to students (pupils) and employees due to exposure to radon while in the building of an educational institution, calculated on the basis of the results of instant measurements of radon EEC, ranged from 0.34 to 4.87 mSv/year for different institutions. However, calculation on the basis of the results of long-term measurements of radon concentration resulted in the dose values 2-4 times higher (from 1.40 to 14.79 mSv/year). These results do not reflect the real exposure scenario, since solid-state nuclear track detectors were exposed continuously, including nights, weekends and holidays (i.e. periods of actual absence of people in the buildings of the educational institutions). Based on the results of instant measurements of radon EEC, the contribution of radon and its progeny to the individual annual effective dose due to all natural sources of ionizing radiation to students (pupils) and employees was 59% (2.21 mSv/year) in the kindergarten of Opol’e, 61% (2.41 mSv/year) in the kindergarten of Falileevo, 82% (6.81 mSv/year) in the school of Falileevo, and 82% (7.11 mSv/year) in the school of Bol’shaya Pustomerzha. According to the classification established in sanitary rules and norms OSPORB 99/2010, the exposure of students and employees of the surveyed schools is classified as “increased” (from 5 to 10 mSv/year) when using the results of instant measurements of radon EEC, and is classified as “high” when using the results of long-term measurements of radon concentration (more than 10 mSv/year). The average individual lifetime risk of radon-induced lung cancer death (based on the results of instant measurements of radon EEC) for students (pupils) and employees was 3.8∙10–4 in the kindergarten of Opol’e, 4.1∙10–4 in the kindergarten of Falileevo, 1.2∙10–3 in the school of Falileevo, and 1.2∙10–3 in the school of Bol’shaya Pustomerzha. However, calculation on the basis of the results of long-term measurements of radon concentration resulted in the risk values from 1.5 to 2.4 times higher. The results obtained can be used to improve the method of monitoring of indoor radon concentration in existing operated public buildings in the Russian Federation, which in turn will make it possible to obtain correct values of doses and health risks.

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 paper presents data on indoor radon concentrations in the buildings of children institutions in a number of regions of the Russian Federation. The results of detailed radon surveys in 132 buildings of children institutions in 85 settlements of six districts of the Leningrad Region conducted in 2018-2020 were analyzed. In 14 buildings of children institutions in the Leningrad region (10.5% of all surveyed buildings) the hygienic limit on the indoor radon EEC was exceeded, the maximum measured value of radon concentration in the premises of children institutions reached 2200 Bq/m3. It seems appropriate to extend the experience of cooperation between the Directorate of the Rospotrebnadzor for the Leningrad Region and the Saint-Petersburg Research Institute of Radiation Hygiene after Professor P.V. Ramzaev in conducting detailed radon surveys in children institutions on other regions of the Russian Federation that face problems with indoor radon.

1,500 respondents took part in an Internet survey conducted in autumn 2020 in the Russian Federation. The survey was a part of the Radon Cross-Cultural Multilingual Public Opinion Survey (STEAM project) in the framework of the IAEA technical cooperation project RER9153. The survey was representative for the population of the country as per sex, age, and a region of residence. Random sampling error didn’t exceed 2.5 % for 95 % confidence interval. All respondents were given some information on radon that was as similar as possible in questionnaires published in languages spoken in all 22 coun- tries that took part in the STEAM project; it was done in order to provide an opportunity to make further cross-country com- parison of the survey results. The objective of the survey was to investigate what attitudes people had towards their health and towards radon as a possible health risk factor. The survey revealed that in the Russian Federation people were rather poorly aware about radon. Only 31.7 % re- spondents stated that they were to a greater or lesser extent informed about radon. The level of knowledge about radon as a health risk factor was at a comparable level. For the majority of respondents, information about radon received from Ro- spotrebnadzor and its subordinate research institute formed the perception of radon as a risk factor that requires actions to mitigate its impact on health. Medical specialists turned out to be the most trustworthy source of information about health risks, first of all, family doctors and physicians in polyclinics; people also trusted medical prevention centers, Rospotrebnad- zor, regional and local public health care authorities. Results of the presented survey that was the first social survey focusing on the radon problem and conducted throughout the country can be used as a basis for planning communication strategies within the framework of both national and regional radon programs.

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.

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.

When analyzing the results of radon surveys, there could be an issue with measurements that are below the limit of detection (LOD) of the measurement technique used. This issue is usually referred to as the management of left-censored data. The paper presents the results of the practical application of one the most accurate and easy to calculate methods for analyzing censored data – the β-substitution method – to the analysis of an indoor radon concentrations dataset. The results of the radon survey conducted in the framework of the regional program “Radon” in Krasnoselskiy district of St. Petersburg in 2000 have been used as the test dataset. It is shown that inappropriate approaches to the management of the censored data, such as discarding the censored values or substituting them with the LOD value, can lead to considerably biased estimates of parameters or statistics of the resulting distributions. Further, this could result in an overestimation of doses and risk estimates which are based on the median values. The visual and quantitative analysis of Q-Q plots leads to conclusion that the estimated parameters of the distribution after the application of the β-substitution method are characterized by a minimum bias. The applied β-substitution method could be recommended for use as an element in the procedure of analyzing the results of radon surveys to minimize the bias of the estimates of the parameters of the radon concentration distributions alongside with Q-Q plots used to verify the conformity of radon concentrations with a lognormal distribution.

The deadline for the development of the final draft of the new radiation safety standards RSS-2019, harmonized with international recommendations, including the regulation of radon content in the indoor air of residential and public buildings is expected to be finished in 2019. We estimated the possibility and expediency for replacement of the hygienic standard established in RSS -99/2009 with the reference level recommended by the International Basic Safety Standards of IAEA GSR Part 3 on the basis of data analysis results on radon content levels in indoor air of residential and public buildings on the territory of subjects of the Russian Federation. An analysis of the array of measurements results for radon content with a volume of 680,301 measurements taken during the period from 2001 to 2017 in the subjects of the Russian Federation collected as part of Unified State System for Control of Individual Exposure Doses and stored in the Federal database of exposure doses of citizens of the Russian Federation due to the natural and man-made background radiation was carried out. Absolute and relative estimates of the number of radon EEVA values exceeding 200, 150 and 120 Bq/m 3 were obtained, both for individual regions and for the country as a whole. The results show that the reduction of hygienic standard of radon EEVA will increase the share of the non-compliant regulatory instruments of residential and public buildings up to 150 Bq/m 3 almost in 2 times, up to 120 Bq/m 3 almost in 3 times on average in Russia. We formulated a number of proposals aimed at harmonizing the Russian standards of radon content in indoor air with the IAEA recommendations taking into account the economic feasibility and while maintaining the possibility of monitoring compliance with the requirements of radiation population safety.

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.

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.

The deadline for the development of the final draft of the new radiation safety standards RSS-2019, harmonized with international recommendations, including the regulation of radon content in the indoor air of residential and public buildings is expected to be finished in 2019. We estimated the possibility and expediency for replacement of the hygienic standard established in RSS -99/2009 with the reference level recommended by the International Basic Safety Standards of IAEA GSR Part 3 on the basis of data analysis results on radon content levels in indoor air of residential and public buildings on the territory of subjects of the Russian Federation. An analysis of the array of measurements results for radon content with a volume of 680,301 measurements taken during the period from 2001 to 2017 in the subjects of the Russian Federation collected as part of Unified State System for Control of Individual Exposure Doses and stored in the Federal database of exposure doses of citizens of the Russian Federation due to the natural and man-made background radiation was carried out. Absolute and relative estimates of the number of radon EEVA values exceeding 200, 150 and 120 Bq/m3 were obtained, both for individual regions and for the country as a whole. The results show that the reduction of hygienic standard of radon EEVA will increase the share of the non-compliant regulatory instruments of residential and public buildings up to 150 Bq/m3 almost in 2 times, up to 120 Bq/m3 almost in 3 times on average in Russia. We formulated a number of proposals aimed at harmonizing the Russian standards of radon content in indoor air with the IAEA recommendations taking into account the economic feasibility and while maintaining the possibility of monitoring compliance with the requirements of radiation population safety.