The levels of Indoor radon can increase in newly built apartments that mainly use construction materials such as concrete. However, radon measurement in newly built buildings has only been implemented recently, and there is a lack of sufficient data for radon management purposes. This study aimed to determine the levels of indoor radon in newly built apartments by regions, sizes of household, and floor (lower, middle, upper floor), and to explore the trend of radon reduction by time according to ventilation methods. Indoor radon was measured in 48 households in four regions (Gyeonggi-do and Gangwon-do). Measurements were performed for 48 hours and 24 hours under closed and ventilated conditions using real-time measurement devices FRD400 and RAD7, respectively. To analyze changes in radon concentration by floors, data were collected by dividing households into lower, middle, and upper floors according to their vertical height. The concentrations of indoor radon ranged from 12.1 Bq/m3 to 559.0 Bq/m3 when windows were closed and 12.0 Bq/m3~500.0 Bq/m3 when ventilated (including both mechanical and natural ventilation). On average, the concentration of closed conditions of household when sealed (arithmetic average 185.3 Bq/m3) was 1.5 times higher than the concentration during ventilation (including mechanical and natural ventilation: 123.8 Bq/m3), and around three times higher than the average for mechanical ventilation (65.7 Bq/m3). It was found that the indoor radon concentration statistically increased as the height increased and the size of the house became smaller. Typically, it took 7 to 8 hours to exceed the standard of 148 Bq/m3 after windows were closed. It decreased to less than 148 Bq/m3 within 3 to 4 hours after operating the mechanical ventilation system. However, in the case of natural ventilation, it takes more than 24 hours to reach below the standard value, and the concentrations stagnated after 24 hours. In conclusion, radon concentration in narrow spaces can be relatively high if ventilation is not sufficient due to the nature of apartments with wall-type structures. Therefore, it is necessary to prepare various radon reduction measures according to floor, size, and ventilation methods.

As awareness about the danger of radon in indoor air has increased, various studies have been conducted to reduce the source of radon. This study was performed to investigate the effect of radon mitigation technology in a railway tunnel. Radon barrier paint and radon shield membrane developed to reduce the concentration of radon in soil and construction material were applied in the tunnel. The tunnel was divided into three sections, A, B, and C, and radon barrier paint, a buffer section, and radon shield membrane were applied, respectively. After securing a sealing screen to the floor and division of each section, radon concentrations were measured and compared before and after each product was applied, and statistical significance was confirmed through the Wilcoxon signed rank test. Measurement was performed with the In-Situ Method and Closed Chamber Method. Radon concentration measured by the in-situ method changed in A section to 124.1 Bq/m2/day from 614.1 Bq/m2/day (79.8%, z=-2.521, p<0.05), in B section to 416.2 Bq/m2/day from 467.1 Bq/m2/day (10.9%, z=-0.980, p=0.327), and in C section to 47.3 Bq/m2/day from 645.6 Bq/m2/day (92.7%, z=-2.521, p<0.05). Radon concentration measured by the closed chamber method recorded a decrease in A section to 88.8 Bq/m3 from 364.2 Bq/m3 (75.6%, z=-2.201, p<0.05), in B section to 471.8 Bq/m3 from 583.3 Bq/m3 (19.1%, z=-0.700, p=0.484), and in C section to 115.9 Bq/m3 from 718.8 Bq/m3 (83.9%, z=-2.521, p<0.05). In addition to soil, it is very important to mitigate radon from building materials with a high contribution rate of radon in order to manage radon by source. Due to the spatial characteristics of railway tunnels, soil and wall concrete structures are exposed as they are, so it is considered that radon mitigation actions are required utilizing verified methods with high mitigation efficiency.

Although monitoring of radon has been extensively implemented throughout South Korea, the risk assessment has been mainly limited to indoor environments such as schools, workplaces, and multi-use facilities, and evaluations have normally been performed separately. In this study, the differences in radon exposure according to two groups (< 1 and 1-6 years old) were evaluated considering various indoor and outdoor environments, timeactivity patterns, variations in radon concentrations, and dwelling type (single detached and apartment house) using Monte-Carlo simulation. The distribution and representative values of radon concentration by micro-environments were confirmed through the Anders-Darling test, and a uniform distribution was applied in case of uncertainty. The effective dose ranged from 1.81 ± 1.19 to 2.81 ± 3.02mSv/y. Comparing the levels recommended by EPA, WHO, and ICRP with the value of the 95th percentile of this study, it was found that the results for those dwelling in detached houses exceeded recommended levels. Infants that spend a lot of time in homes with relatively high levels of concentration of radon are assessed to be somewhat more vulnerable to radon exposure.

This study installed and evaluated the efficiency of a radon barrier membrane, radon mat, and radon well in the removal and reduction of radon gas that originates from the soil and flows indoors. The study aims to present a fundamental and long-term solution to radon reduction in buildings by preventing soil radon, which is the main source of radon gas, from migrating indoors. A radon barrier membrane, radon mat, and radon well were developed and verified, and the radon reduction effect of each system was evaluated. Through applying a special radon gas blocking film with a 5-layer structure, the radon barrier membrane prevents radon gas particles from passing through the polymer deposited on the radon blocking film. The radon mat is a type of radon reduction construction method that induces radon gas generated from the soil under the building to move in the desired direction through the plate-structured pressure reducing panel and discharges radon gas to the outside of the building through an exhaust pipe and fan installed at the edge. In addition, the radon well can also be applied to special structures such as old buildings and historical sites where it is difficult to directly reduce radon concentration within the building foundation, because the intake area can be controlled and, therefore, the method can be applied in a variety of environments and ranges. In the case of Intervention 1 (installing a radon barrier membrane and radon mat), the soil radon was reduced by 24.7%. Intervention 2 (installing a radon barrier membrane, radon mat, and radon well) reduced the soil radon by 45.1%, indicating that the effect of reducing the soil radon concentration was 1.8 times higher compared with installing only the radon barrier membrane and radon mat. The measurement showed that the indoor radon concentration was reduced by 46.5%, following the reduction in soil radon concentration through Interventions 1 and 2, demonstrating the effect of reducing indoor radon gas by installing the radon barrier membrane, radon mat, and radon well. Through the production and installation of prototype systems, this study confirmed the reduction effect of radon concentration in soil and indoor air. These systems achieved a higher efficiency at a relatively low cost than that achieved with the existing radon reduction methods applied in Korea and abroad.

In this study, we learned about the effects of indoor radon concentration reduction associated with the operation of a mechanical ventilation system at an apartment house. The experimental parameters were mainly the indoor radon level and air change rate, which were controlled by the amount of emissions released and fan motor speed. Even at the high level of radon diffused in an apartment house, indoor radon concentrations converged to the Korean national guideline level within 3 to 4 hours when the air was ventilated at 0.5 ACH and 0.7 ACH. In the case of 0.3 ACH, however, where the degree of ventilation was insufficient compared to the legal air change rate, the high concentration indoor radon could not be sufficiently removed even if the mechanical ventilation system was operated for more than 14 hours continuously. When the indoor radon level was high, the reduction rate was 34.3% for 0.3 ACH, 70.4% for 0.5 ACH, and 69.7% for 0.7 ACH at 6 hours-operation, while at the medium-level, indoor radon can be reduced by 46.2% (0.3 ACH) to 73.2% (0.7 ACH). Depending on the indoor concentration range, it may be required to secure a ventilation rate of 0.5 ACH or more at all times. In addition, in apartment houses with excellent airtight performance, even if indoor radon is at a level similar to the national guideline, it is difficult to expect a reduction in the concentration due to natural decay. Therefore, it is desirable to lower the indoor concentrations as much as possible.

This study was designed to verify what effect the use of a natural ventilation system can have on improving indoor air quality with regard to radon in various concentration ranges in an apartment house. The results show that both high (2~3 times higher than 148 m3) and low (similar to 148 Bq/m3) levels of indoor radon concentrations can be reduced close to and/or below the Korean IAQ guideline within 6 hours when the natural ventilation system is operated at approximately an air change rate of 0.5. In the case of an air change rate of 0.3, however, the indoor radon levels cannot meet the national guidelines and the reduction effect was insufficient with regard to various radon concentrations. Typically, the air change rate of a natural ventilation system is affected by meteorological factors such as temperature, relative humidity, wind speed, pressure. Its effectiveness varies according to such factors, for that reason, the reduction effects on radon did not increase proportionally with the ventilation time in this study.

The purpose of this study was to introduce strategies and projects through which local government can play a role in mitigating damage to health when addressing the health challenge posed by radon (222Rn). We first compared and analyzed naturally occurring radioactive material (NORM) in the soil of relatively high (Geumsan) and low (Boryeong) concentration areas of indoor radon (222Rn) to understand the factors influencing concentrations. Mortality rates linked to lung cancer in the areas were also compared and analyzed in the study (T-test). We selected two key priority research studies and four key strategies based on status analysis and a review of domestic and international policy trends in relation to radon (222Rn). As a result of comparing the radium and thorium in the soil with indoor radon concentrations, Geumsan had a higher mean concentration of indoor radon (222Rn = 182.8 Bq/m3) and recorded a higher concentration of radium (226Ra = 48.4 Bq/kg) than Boryeong (226Ra = 43.9 Bq/kg). These findings show that Geumsan, which had a high concentration of radium (226Ra), revealed a high concentration of radon (222Rn), a radioactive decay material of radium (226Ra), demonstrating that the concentration of indoor radon (222Rn) can vary according to geological and soil characteristics. The age standardized mortality from lung cancer per 100,000 people was 31.6 in Geumsan and 27.3 in Boryeong (p < 0.05). These findings show that there is likely an association between the concentration of indoor radon (222Rn) and mortality from lung cancer. Two key priority research studies include a survey on factors influencing exposure to radon (222Rn) in local environments and preparation of a potential map of radon (222Rn). Four key strategies include “management of exposure factors regarding radon (222Rn),” “environmental health services provided to protect radon (222Rn) exposure,” “management of technical support measures for radon (222Rn),” and “disclosure regarding the risk of radon (222Rn) exposure (risk communication).”

We investigated the distributions of airborne radon concentration on the platforms of the stations of Seoul Metro by the underground depth of each subway line, and explored the correlation between the radon concentration and the depth and geological conditions around each underground station. The measurements of radon levels were performed in 254 subway stations within Seoul Metro Lines 1 to 8 using the passive sampler (RADUET). Radon concentration data from 2007 to 2017, as well as the depth of each subway station were obtained from the Seoul Metro corporation. The geological information of each subway station were purchased from the Korea Institute of Geoscience and Mineral Resources. Student t-test and correlation analyses were performed to compare the levels of radon by the depth of subway stations, and to investigate the association of radon levels based on geological information. The geometric mean concentration of the all subway stations was 27.9 Bq/m3 ( range, 3 . 7Bq/ m3~124.0 Bq/m3). The depth of Lines 5-8 (geometric mean, –20.3 m) was significantly deeper by about 50% or more than that of Lines 1-4 (–13.1 m) (P<0.01). The radon levels increased significantly in deeper depths and as the number of Lines increased (P<0.05). A significant higher mean concentration of radon above the igneous rock (33.0 Bq/m3) was observed, comparing to that of non-igneous rock (27.5 Bq/m3) (P<0.00001). Our findings indicate that the deeper the subway is built or the more it is constructed on the granite area, the more careful management, including frequent ventilation and measurement monitoring, is necessary.

This experiment evaluated the efficiency of mechanical ventilation, one of the measures to reduce indoor radon concentration in residential spaces. In the most popular ventilation rates of the air conditioning system, the most efficient air conditioning system was confirmed by checking the time when the radon concentration reached the lowest level, the radon reduction rate, and the radon concentration that could be lowered as much as possible. The results showed a reduction rate of up to 80% or more as a result of conducting the experiment by blocking the inflow of outside air. It was confirmed that the time to reach the lowest concentration after starting the mechanical ventilation was about 6 hours to a maximum of 7 hours. Therefore, this study verified that indoor radon concentrations can be efficiently reduced by using a mechanical ventilation system.

Radon is a radioactive gas material, which is not detectable by humans because of the absence of color and odor. Radon gas can exist indoors through a number of pathways and long-term exposure to such material can affect the human body, which may result in serious health issues such as lung-cancer. It is thus essential to reduce and maintain indoor radon concentration in order that potential health risks from radon can be diminished. In order to achieve the aforementioned goals, it is requisite to utilize a practical detector which is capable of continuous radon monitoring. In relation to this, a recently developed prototype radon detector, i.e., RS9A, provides highperformance comparable to existing research-grade radon detectors for the purpose of continuous radon monitoring in the air. Furthermore, RS9A is a convenient piece of equipment for use by the public as it is compact in size and affordable. In this paper, we conducted continuous measurements of indoor radon concentrations by using sets of RS9A and evaluated the equivalence of RS9A in terms of quality assurance.

Radon is known to be one of the representative carcinogen materials, and may cause severe health damage to the human body with long-term exposure. Without proper treatment such as natural and mechanical ventilation, indoor radon concentration tends to increase as time passes. In this aspect, it is necessary to maintain indoor radon concentration below the domestic indoor air quality (IAQ) management standard by continuous monitoring. However, the number of practical devices which can detect radon concentration is scarce and most of the existing devices are very costly. Among such devices, the RS9A, a prototype of a radon detector, detects indoor radon concentration and is priced significantly lower compared to other existing radon detectors. In this paper, we investigated the RS9A for the continuous detection of indoor radon gas and compared its performance to a commercially available radon detector (RadonEye). We measured indoor radon concentrations at two separate sites by using both detectors simultaneously. The indoor radon concentrations measured by the aforementioned detectors revealed a high correlation. Therefore, the RS9A can be considered as an appropriate candidate for use as a continuous indoor radon monitoring system.

This study was performed to determine the effects of soil and building materials on indoor radon concentration. Short-term measurements were made in the underground soil of a building along with the radon emanation rates from the phosphogypsum board used as the interior wall. The radon measurements in the soil were 9,213 Bq/m3 in the B3 level, and 3,765 Bq/m3 in the B4 level. Soil radon concentration in the B4 level was 2.4 times higher than in the B3 level. Indoor radon measurements in 50 different locations in the underground of the building, averaged from 144.3 Bq/m3 (B1), 177.0 Bq/m3 (B2), and 189.2 Bq/m3 (B3) to a high of 210.1 Bq/m3 (B4). Indoor radon concentration was increased from the lower level to the upper level. The radon emanation rates from phosphogypsum were 4,234.1 mBq/m2/h and, 450.4 mBq/kg/h. The measurement results indicated that the phosphogypsum board used as building materials as well as the soil could affect the indoor radon concentration.

In this study, indoor radon concentrations were measured in 56 multiple-use facilities located in Gwangju area from December 2017 to December 2018. The average indoor radon concentration in underground space was 51.70 Bq/m3, and that of the 1st floor was 38.73 Bq/m3, indicating that the indoor radon concentration of underground space was higher than that of the 1st floor. The indoor radon concentration was investigated according to the presence or absence of underground space. The concentration of radon on the 1st floor with underground space was 37.25 Bq/m3, and the concentration of radon on the ground floor without underground space was 47.94 Bq/m3. In the absence of underground space, indoor radon concentration was high. The indoor radon concentration of buildings over 30 years old was 87.26 Bq/m3, indicating a significantly higher indoor radon concentration compared to those of buildings less than 30 years old. The indoor radon concentration was investigated according to the operation of a ventilator. The indoor radon concentration of space without an operating ventilator was 52.17 Bq/m3, and that of space with a ventilator in operation for more than 8 hours per day was 36.31 Bq/m3. This result shows that the indoor radon concentration in the space with an operating ventilator is lower than the space where the ventilator is not in operation. The indoor radon concentration in the space with an operating ventilation system was lower than that on the same floor of the same building, and the indoor radon concentration of enclosed space was about 4.4 times higher than that of open space in the same building. In addition, the indoor radon concentration was measured according to the spatial features. The concentration of indoor radon of enclosed space was 64.76 Bq/m3, which is higher than those of an open space and an active space.

The purpose of this study is to implement through the utilization of geographical information that was currently constructed in the development of the radon map creation methodology. In addition, we suggested a model for forecasting radon gas in soil based on the mechanism of radon exhalation from soil. To provide basic data for radon mapping in Korea, we compared the results obtained using the proposed model with the results of a field survey. Based on the comparison, we discussed the feasibility of the proposed model. The soil radon exhalation rate prediction model was built on the first order prediction model in the steady-state based on the law of conversion of mass. To verify the model by comparing the predicted value with a field survey, a grid of 7.5 × 6.3 cm was created at a 1:500,000 map of Korea, and the intersection point of the grid was selected as measurement site. The results showed a low error rate when compared with the previous studies, and it is expected that the model proposed in this study and the currently constructed geogenic information database can be used in combination to map the soil radon gas in Korea.

This study was carried out considering that activated carbon physically adsorbs radon. Among the air cleaners equipped with activated carbon filter, eight air cleaners sold in Korea were selected and the radon reduction rate experiment was conducted. The instrument used an ionization chamber type instrument with a sensitivity of 3 CPM. The experiment was carried out by excluding the natural rate of reduction of radon in order to accurately grasp the radon reduction rate of activated carbon filter. Of the eight air purifiers, only three showed a reduction rate of more than 30%, while the remaining five air purifiers showed a reduction rate of less than 20%. This does not seem to be much different from the natural reduction rate. In addition, since it is not adsorbed by radon alone due to the nature of activated carbon, it is expected that the reduction rate will be lower in a real life environment.

As radon is a naturally occurring radioactive gas that can cause lung cancer and is classified as a Group 1 carcinogen, it is essential for the public to be aware of what radon is, and how to manage radon. Therefore, general information on radon, as well as its health risks, measurement methods, mitigation methods and suggestions for its management are addressed in this article. Over the last one to two decades, a number of wide-ranging studies on radon measurement and mitigation have been conducted in Korea, and the results of each study are comparable to the research achievements of other developed countries. For this reason, it is time to systematically establish a well-made Korean radon management organization.