Radiation Protection Dosimetry (2014), Vol. 160, No. 1–3, pp. 149 –153 Advance Access publication 17 April 2014
doi:10.1093/rpd/ncu073
INFLUENCE OF ENERGY-SAVING MEASURES ON THE RADON CONCENTRATION IN SOME KINDERGARTENS IN THE CZECH REPUBLIC I. Fojtikova* and K. Navratilova Rovenska National Radiation Protection Institute, Bartosˇkova 28, Prague 4 140 00, Czech Republic *Corresponding author: [email protected]
INTRODUCTION The first comprehensive study of radon concentrations in Czech schools and pre-school facilities was carried out in the early 1990s, using bare solid-state track detectors exposed for 1 y. After nearly 20 y, it was decided to repeat the measurements in the framework of the action plan within the Radon Programme for the Czech Republic. The primary purpose was to check the radon levels in the facilities. A second task was, where possible, to compare the current results with the data from the earlier study. Kindergartens were chosen for this study for several reasons: the facilities are spread homogeneously throughout the county and are well accessible through the local authorities, the number of kindergartens is manageable and it is generally accepted that children could be more sensitive to radiation than older age groups. Furthermore, kindergartens measurements can contribute to radon risk awareness raising (mothers of young children are very solicitous and are very sensitive to radon risk information, and the local authorities are willing to co-operate when children are concerned). There are a total of 4000 kindergartens currently operating in the Czech Republic. Fifty per cent were constructed in the 1970s and 1980s, 45 % are located in buildings older than that, and only 5 % are in structures built since 1990. It is obvious that many of the buildings need special attention (reconstruction of floors, wall rendering, sanitary facilities, etc.). Most of them do not conform to current energy consumption standards and are being renovated to meet the new requirements (new tight windows, external wall insulation). The aim of this study was to analyse the influence of renovation works on the average radon concentration measured in kindergartens. A subset of the
analysed data shows the influence of energy-saving reconstructions reported in the literature in recent years(1 – 4). This is a very important topic, due to the large number of subsidies for energy-saving reconstructions that have been granted by the government. The authors also report on some lessons learned from the detailed continuous radon measurements. MATERIALS AND METHODS Long-term measurements Solid-state nuclear track detectors based on Kodak LR-115 foil have been used for long-term radon measurements for about 30 y in the Czech Republic. Bare LR-115, in fact measuring the equilibrium equivalent concentration (EEC), was used from 1985 to 2003. The EEC can be recalculated to the radon concentration using the equilibrium factor F. The results of bare detectors depend on many unknown factors (such as F) and are very sensitive to correct placement in the room. They have therefore been replaced by a system of track detectors enclosed in a diffusion chamber. This system is called RamaRn and has been in place since 2003. RamaRn detectors are traceable to PTB Braunschweig, and more details on the calibration and detector parameters are given in the literature(5, 6). This is the only measuring system used for the long-term measurements in the Czech Republic. Organisation of the surveys A first comprehensive study of Czech schools and preschool facilities was carried out in the early 1990s, using bare solid-state track detectors exposed for 1 y. New measurement campaigns were carried out from
# The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
Due to the large number of subsidies for energy-saving reconstructions granted, and expecting a strong influence of reconstruction on the radon level in building, the long-term measurements of radon concentration are offered free of charge to kindergartens in the Czech Republic. Classrooms and playrooms where the radon levels exceeded the reference value for kindergartens, which is 400 Bq m23, are monitored continuously for at least a week to obtain the average activity concentration of radon when children are present. Some of the kindergartens were previously measured in the 1990s. These earlier measurements have provided an opportunity to compare the results. This paper presents some lessons learned from radon diagnosis carried out in particular cases and an analysis of the influence of reconstruction work on the radon level in the buildings.
I. FOJTIKOVA AND K. NAVRATILOVA ROVENSKA
Short-term measurements According to the Atomic Law in force in the Czech Republic and the decree on radiation protection, workplaces and buildings with high occupancy factors of members of the public in which the longterm average radon concentration exceeds a level of 400 Bq m23 are subject to further and more detailed measurements in all rooms in which this level was exceeded. For kindergartens, the rooms of interest are mainly classrooms, bedrooms and playrooms, where the children spend most of their time during the day. The detailed measurements were carried out for a period of at least a week (7 d), using continuous monitors deployed in rooms where the 400 Bq m23 level was exceeded and, if identified as important, also in neighbouring corridors and in some cases in the cellar. Additional information on radon transport helped in the design of proper corrective actions, where necessary. The average radon concentration for the period of days when children are present was calculated on the basis of the data that were obtained. When children are present and a level of 400 Bq m23 is exceeded, the radon concentration should be decreased below this level and the radiation protection of the children should be optimised. Radim 2pf and Radim 3 monitors were used for radon concentration monitoring. The principle used in monitors of this type is based on diffusion of radon gas through the filter to the measuring chamber. Newborn 218Po ions are collected by an electric field on the surface of the semi-conductor detector. The signal from the amplifier is fed to a single-channel impulse analyser, in which a window is adjusted
around the 218Po peak(7). In all cases, the continuous monitors were accompanied by the RM-1TM radon gas integral electret system to obtain the average radon concentration independently. The gamma dose rate was measured in various places in the investigated building to eliminate the building material as a source of radon. RESULTS An analysis of long-term measurement results In the early 1990s, measurements were carried out in 10 087 pre-school and school education buildings and facilities. Measurements were performed in 35 500 rooms, 15 400 of which were classrooms. At the time when the measurements were made, more than onehalf of the rooms (5500) were used for pre-school education, whereas the rest were grammar schools, high schools or art schools. The arithmetic mean of the radon concentration results was 177 Bq m23, the geometric mean was 124 Bq m23 and the standard deviation was 2.25. Rooms were found with radon levels above the action level (equivalent radon concentration .200 Bq m23) in approximately every 20th facility (i.e. 5 % of the rooms exceeded the action level). A total of 1166 classrooms (out of a total of 15 400) exceeded the action level. New measurement campaigns were carried out in the 2011–2012 and 2012– 2013 academic years. In 2011– 2012, 697 buildings were measured and 76 facilities were found to exceed the reference level (radon concentration .400 Bq m23). In 2012–2013, 540 buildings were measured and 110 facilities were found to exceed the reference level. In the new campaign, therefore, 15 % of all monitored buildings exceeded the reference level. This result demonstrates a rapid qualitative increase in the radon levels in Czech pre-school and school facilities. Influence of reconstruction and energy-efficiency improvements on the long-term average radon concentration More than one-half of the facilities measured in the new campaign had undergone some type of reconstruction. Sixty-eight per cent of the reconstructions included insulation of the external walls. To make a quantitative evaluation of the influence on the radon levels of the improvements to the energy efficiency of the buildings, facilities with two sets of completed radon measurements were selected (concentrations c0 measured in the 1990s and c1 measured after 2010) together with reliable information about the type of reconstruction that was performed. Two groups were formed: with window replacement, and without window replacement. The results are summarised in Table 1. The difference between the two
150
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
September 2011 and from September 2012. RamaRn detectors were used for these new campaigns. The detectors were exposed only during the academic year (September–June). Both campaigns were organised on a voluntary basis. The offer was accompanied by a recommendation from the local authorities and from the State Office for the Nuclear Safety. In both cases, the measurements were funded from the Czech Radon Programme. In this way, the authors could obtain a data set of kindergartens with both historical and recent indoor radon concentration results. The maximum radon concentration found in a room in which children stayed for a long period of time was chosen to represent the radiation exposure in a given facility. Concurrently with the measurements, data were gathered concerning the state of the buildings, i.e. year of reconstruction, type of construction, window replacements, etc. Using all available data in combination, the authors could investigate the influence of thermal retrofitting on indoor radon concentrations.
INFLUENCE OF ENERGY-SAVING MEASURES ON THE RADON CONCENTRATION Table 1. Influence of the building improvements on the radon levels. Reconstruction Yes No
Number of buildings
Mean radon level in the 1990s (Bq m23)
Mean radon level after 2011 (Bq m23)
264 247
125 (GSD ¼ 2.15) 136 (GSD ¼ 2.14)
204 (GSD ¼ 2.15) 149 (GSD ¼ 2.27)
Lessons learned from the short-term radon measurements Window effect Figure 1. The comparison of radon level distribution before and after reconstruction.
Figure 2. The individual effect of reconstruction in preschool and school facilities.
groups was tested using analysis of variance and was found to be statistically significant. A mean increase of 63 % in the radon levels can be concluded from Table 1. A graphical view of this issue for retrofitted facilities is shown in Figure 1, which displays the distributions of values measured in the same buildings. The first series shows results obtained in the early 1990s, whereas the second series represents the recent results. Both distributions have a log–normal character.
The replacement of old windows by new tight doubleglazed windows is one of the major factors in increasing the energy efficiency of buildings. Series of measurements were carried out in buildings where some or all of the windows were replaced. Figure 3 shows a clear difference in the ventilation rate. Data were collected simultaneously in three classrooms adjacent to each other; two of the rooms had old wooden windows, whereas the third was equipped with new plastic sealed windows. The long-term measurements provide only a single averaged level of radon concentration per measured room for the duration of the measurement. However, both children and teachers are present in the building only for a limited period of time. Although the ventilation rate is high enough during the period when the building is occupied, an insufficiently sealed building substructure and a tight building envelope can form a very high indoor radon concentration when the building is not in use (typically at weekends, during holidays and at night). This may lead to the high radon levels reported by the long-term integrated detectors [also reported in Bochicchio et al.(8)] An example of a situation of this type is shown in Figure 4. Repeated verification of corrective actions If certain criteria are met, it is possible to obtain a government subsidy for corrective actions that should effectively lower the radon concentration indoors. This system was introduced in the Czech Republic in 1991 and is still valid. Increase in the ventilation rate
151
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
There is a clearly visible shift of concentrations to higher values. Another view on the data is given in Figure 2. The ratio c1/c0 was calculated for each facility having available information about the type of reconstruction. The distribution shows a shift in individual radon levels since the first measurements in the 1990s. The substantial increase in radon concentration in facilities with new tight windows (together with support from energy-saving technologies) indicates a possible increase in the collective dose to Czech children and teachers.
I. FOJTIKOVA AND K. NAVRATILOVA ROVENSKA
Figure 4. Effect of tight windows on radon concentration in playroom.
using central ventilation systems was the historically first attempt as the radon corrective action. If this system is used, the filters need to be changed at least periodically. However, there is no easy way to prove that the measures that were taken are still effective to maintain the low radon concentration indoors. This system was used to lower the radon concentration in a kindergarten located in a villa-type house built at the beginning of the 20th century. A central ventilation system was installed in 1990 to decrease radon levels of 900 Bq m23. The efficiency of this action was verified by repeated measurements.
This kindergarten was measured again in the campaign carried out in 2011/2012, and the results were from 900 to 1500 Bq m23 for the long-term average. It should be noted that this building had not undergone any major reconstruction or thermal retrofitting. Again, the radon diagnostic measurements helped in understanding what is going on. Detailed continuous monitoring in all habitable rooms, with the ventilation system working in standard regime for 1 week, and then switched off in the second week, revealed no difference between these two modes (see Figure 5).
152
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
Figure 3. Old and new tight windows in two neighbouring classrooms.
INFLUENCE OF ENERGY-SAVING MEASURES ON THE RADON CONCENTRATION
This led to the conclusion that the remediation system is no longer effective.
TB01SUJB072, and by Programme—Action Plan.
the
Czech
Radon
REFERENCES
CONCLUSION These results showed clearly that recent energy-saving efforts resulting in increased air-tightness of older buildings are accompanied by an accumulation of substances, specifically radon, that have detrimental long-term effects on people’s health. The long-term average indoor radon values increased significantly in Czech kindergartens that have been thermally retrofitted. This does not automatically mean that the children attending these kindergartens are overexposed. The actual impact of the increased air-tightness of buildings on increasing the radon effective dose can be compensated by sufficient ventilation during the time when the rooms are occupied. This was shown by detailed measurements in nearly one-half of the kindergartens with radon levels exceeding the reference value and presented in Figure 4. This study has shown that it is important to make periodic measurements to verify repeatedly that remedial measures are reducing radon levels to an acceptable level while the rooms are occupied. FUNDING The activities reported here were funded by the Czech ˇ R) under Project No. Technological Agency (TAC
1. Milner, J., Shrubsole, C., Das, P., Jones, B., Ridley, I., Chalabi, Z. et al. Home energy efficiency and radon related risk of lung cancer: modelling study. BMJ. 348, f7493 (2014). 2. Jira´nek, M. and Kacˇmarˇ´ıkova´, V. Dealing with the increased radon concentration in thermally-retrofitted buildings. Radiat. Prot. Dosim. 160 (1–3), 43– 47 (2014). 3. RADPAR. Deliverable 13/5 Measurement and Analysis of Radon in Low Energy and Passive Houses in Austria, W. Ringer, J. Gra¨ser. (2012). 4. Fronˇka, A. and Jı´lek, K. Radon entry rate analyses using in-situ tracer gas method application. Radiat. Prot. Dosim. 160(1– 3), 143– 148 (2014). 5. Sleza´kova´, M., Navra´tilova´ Rovenska´, K., Toma´sˇek, L. and Holecˇek, J. Short- and long-term variability of radon progeny concentration in dwellings in the Czech Republic. Radiat. Prot. Dosim. 153(3), 334–341 (2013). First published online 27 June 2012. doi:10.1093/rpd/ncs111. 6. Thinova´, L. and Burian, I. Effective dose assessment for workers in caves in the Czech Republic: experiments with passive radon detectors. Radiat. Prot. Dosim. 130(1), 48–51 (2008). First published online 24 April 2008. doi:10.1093/rpd/ncn118. 7. User guide for Radim3. Jiri Plch – SMM (1998), [in Czech]. 8. Bochicchio, F., Zunic, Z. S., Carpentieri, C., Antignani, S., Venoso, G., Carelli, V., Cordedda, C., Veselinovic, N., Tollefsen, T. and Bossew, P. Radon in indoor air of primary schools: a systematic survey to evaluate factors affecting radon concentration levels and their variability. Indoor Air. (2013). doi:10.1111/ina.12073.
153
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
Figure 5. Ineffective remedial measure.
doi:10.1093/rpd/ncu073
INFLUENCE OF ENERGY-SAVING MEASURES ON THE RADON CONCENTRATION IN SOME KINDERGARTENS IN THE CZECH REPUBLIC I. Fojtikova* and K. Navratilova Rovenska National Radiation Protection Institute, Bartosˇkova 28, Prague 4 140 00, Czech Republic *Corresponding author: [email protected]
INTRODUCTION The first comprehensive study of radon concentrations in Czech schools and pre-school facilities was carried out in the early 1990s, using bare solid-state track detectors exposed for 1 y. After nearly 20 y, it was decided to repeat the measurements in the framework of the action plan within the Radon Programme for the Czech Republic. The primary purpose was to check the radon levels in the facilities. A second task was, where possible, to compare the current results with the data from the earlier study. Kindergartens were chosen for this study for several reasons: the facilities are spread homogeneously throughout the county and are well accessible through the local authorities, the number of kindergartens is manageable and it is generally accepted that children could be more sensitive to radiation than older age groups. Furthermore, kindergartens measurements can contribute to radon risk awareness raising (mothers of young children are very solicitous and are very sensitive to radon risk information, and the local authorities are willing to co-operate when children are concerned). There are a total of 4000 kindergartens currently operating in the Czech Republic. Fifty per cent were constructed in the 1970s and 1980s, 45 % are located in buildings older than that, and only 5 % are in structures built since 1990. It is obvious that many of the buildings need special attention (reconstruction of floors, wall rendering, sanitary facilities, etc.). Most of them do not conform to current energy consumption standards and are being renovated to meet the new requirements (new tight windows, external wall insulation). The aim of this study was to analyse the influence of renovation works on the average radon concentration measured in kindergartens. A subset of the
analysed data shows the influence of energy-saving reconstructions reported in the literature in recent years(1 – 4). This is a very important topic, due to the large number of subsidies for energy-saving reconstructions that have been granted by the government. The authors also report on some lessons learned from the detailed continuous radon measurements. MATERIALS AND METHODS Long-term measurements Solid-state nuclear track detectors based on Kodak LR-115 foil have been used for long-term radon measurements for about 30 y in the Czech Republic. Bare LR-115, in fact measuring the equilibrium equivalent concentration (EEC), was used from 1985 to 2003. The EEC can be recalculated to the radon concentration using the equilibrium factor F. The results of bare detectors depend on many unknown factors (such as F) and are very sensitive to correct placement in the room. They have therefore been replaced by a system of track detectors enclosed in a diffusion chamber. This system is called RamaRn and has been in place since 2003. RamaRn detectors are traceable to PTB Braunschweig, and more details on the calibration and detector parameters are given in the literature(5, 6). This is the only measuring system used for the long-term measurements in the Czech Republic. Organisation of the surveys A first comprehensive study of Czech schools and preschool facilities was carried out in the early 1990s, using bare solid-state track detectors exposed for 1 y. New measurement campaigns were carried out from
# The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
Due to the large number of subsidies for energy-saving reconstructions granted, and expecting a strong influence of reconstruction on the radon level in building, the long-term measurements of radon concentration are offered free of charge to kindergartens in the Czech Republic. Classrooms and playrooms where the radon levels exceeded the reference value for kindergartens, which is 400 Bq m23, are monitored continuously for at least a week to obtain the average activity concentration of radon when children are present. Some of the kindergartens were previously measured in the 1990s. These earlier measurements have provided an opportunity to compare the results. This paper presents some lessons learned from radon diagnosis carried out in particular cases and an analysis of the influence of reconstruction work on the radon level in the buildings.
I. FOJTIKOVA AND K. NAVRATILOVA ROVENSKA
Short-term measurements According to the Atomic Law in force in the Czech Republic and the decree on radiation protection, workplaces and buildings with high occupancy factors of members of the public in which the longterm average radon concentration exceeds a level of 400 Bq m23 are subject to further and more detailed measurements in all rooms in which this level was exceeded. For kindergartens, the rooms of interest are mainly classrooms, bedrooms and playrooms, where the children spend most of their time during the day. The detailed measurements were carried out for a period of at least a week (7 d), using continuous monitors deployed in rooms where the 400 Bq m23 level was exceeded and, if identified as important, also in neighbouring corridors and in some cases in the cellar. Additional information on radon transport helped in the design of proper corrective actions, where necessary. The average radon concentration for the period of days when children are present was calculated on the basis of the data that were obtained. When children are present and a level of 400 Bq m23 is exceeded, the radon concentration should be decreased below this level and the radiation protection of the children should be optimised. Radim 2pf and Radim 3 monitors were used for radon concentration monitoring. The principle used in monitors of this type is based on diffusion of radon gas through the filter to the measuring chamber. Newborn 218Po ions are collected by an electric field on the surface of the semi-conductor detector. The signal from the amplifier is fed to a single-channel impulse analyser, in which a window is adjusted
around the 218Po peak(7). In all cases, the continuous monitors were accompanied by the RM-1TM radon gas integral electret system to obtain the average radon concentration independently. The gamma dose rate was measured in various places in the investigated building to eliminate the building material as a source of radon. RESULTS An analysis of long-term measurement results In the early 1990s, measurements were carried out in 10 087 pre-school and school education buildings and facilities. Measurements were performed in 35 500 rooms, 15 400 of which were classrooms. At the time when the measurements were made, more than onehalf of the rooms (5500) were used for pre-school education, whereas the rest were grammar schools, high schools or art schools. The arithmetic mean of the radon concentration results was 177 Bq m23, the geometric mean was 124 Bq m23 and the standard deviation was 2.25. Rooms were found with radon levels above the action level (equivalent radon concentration .200 Bq m23) in approximately every 20th facility (i.e. 5 % of the rooms exceeded the action level). A total of 1166 classrooms (out of a total of 15 400) exceeded the action level. New measurement campaigns were carried out in the 2011–2012 and 2012– 2013 academic years. In 2011– 2012, 697 buildings were measured and 76 facilities were found to exceed the reference level (radon concentration .400 Bq m23). In 2012–2013, 540 buildings were measured and 110 facilities were found to exceed the reference level. In the new campaign, therefore, 15 % of all monitored buildings exceeded the reference level. This result demonstrates a rapid qualitative increase in the radon levels in Czech pre-school and school facilities. Influence of reconstruction and energy-efficiency improvements on the long-term average radon concentration More than one-half of the facilities measured in the new campaign had undergone some type of reconstruction. Sixty-eight per cent of the reconstructions included insulation of the external walls. To make a quantitative evaluation of the influence on the radon levels of the improvements to the energy efficiency of the buildings, facilities with two sets of completed radon measurements were selected (concentrations c0 measured in the 1990s and c1 measured after 2010) together with reliable information about the type of reconstruction that was performed. Two groups were formed: with window replacement, and without window replacement. The results are summarised in Table 1. The difference between the two
150
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
September 2011 and from September 2012. RamaRn detectors were used for these new campaigns. The detectors were exposed only during the academic year (September–June). Both campaigns were organised on a voluntary basis. The offer was accompanied by a recommendation from the local authorities and from the State Office for the Nuclear Safety. In both cases, the measurements were funded from the Czech Radon Programme. In this way, the authors could obtain a data set of kindergartens with both historical and recent indoor radon concentration results. The maximum radon concentration found in a room in which children stayed for a long period of time was chosen to represent the radiation exposure in a given facility. Concurrently with the measurements, data were gathered concerning the state of the buildings, i.e. year of reconstruction, type of construction, window replacements, etc. Using all available data in combination, the authors could investigate the influence of thermal retrofitting on indoor radon concentrations.
INFLUENCE OF ENERGY-SAVING MEASURES ON THE RADON CONCENTRATION Table 1. Influence of the building improvements on the radon levels. Reconstruction Yes No
Number of buildings
Mean radon level in the 1990s (Bq m23)
Mean radon level after 2011 (Bq m23)
264 247
125 (GSD ¼ 2.15) 136 (GSD ¼ 2.14)
204 (GSD ¼ 2.15) 149 (GSD ¼ 2.27)
Lessons learned from the short-term radon measurements Window effect Figure 1. The comparison of radon level distribution before and after reconstruction.
Figure 2. The individual effect of reconstruction in preschool and school facilities.
groups was tested using analysis of variance and was found to be statistically significant. A mean increase of 63 % in the radon levels can be concluded from Table 1. A graphical view of this issue for retrofitted facilities is shown in Figure 1, which displays the distributions of values measured in the same buildings. The first series shows results obtained in the early 1990s, whereas the second series represents the recent results. Both distributions have a log–normal character.
The replacement of old windows by new tight doubleglazed windows is one of the major factors in increasing the energy efficiency of buildings. Series of measurements were carried out in buildings where some or all of the windows were replaced. Figure 3 shows a clear difference in the ventilation rate. Data were collected simultaneously in three classrooms adjacent to each other; two of the rooms had old wooden windows, whereas the third was equipped with new plastic sealed windows. The long-term measurements provide only a single averaged level of radon concentration per measured room for the duration of the measurement. However, both children and teachers are present in the building only for a limited period of time. Although the ventilation rate is high enough during the period when the building is occupied, an insufficiently sealed building substructure and a tight building envelope can form a very high indoor radon concentration when the building is not in use (typically at weekends, during holidays and at night). This may lead to the high radon levels reported by the long-term integrated detectors [also reported in Bochicchio et al.(8)] An example of a situation of this type is shown in Figure 4. Repeated verification of corrective actions If certain criteria are met, it is possible to obtain a government subsidy for corrective actions that should effectively lower the radon concentration indoors. This system was introduced in the Czech Republic in 1991 and is still valid. Increase in the ventilation rate
151
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
There is a clearly visible shift of concentrations to higher values. Another view on the data is given in Figure 2. The ratio c1/c0 was calculated for each facility having available information about the type of reconstruction. The distribution shows a shift in individual radon levels since the first measurements in the 1990s. The substantial increase in radon concentration in facilities with new tight windows (together with support from energy-saving technologies) indicates a possible increase in the collective dose to Czech children and teachers.
I. FOJTIKOVA AND K. NAVRATILOVA ROVENSKA
Figure 4. Effect of tight windows on radon concentration in playroom.
using central ventilation systems was the historically first attempt as the radon corrective action. If this system is used, the filters need to be changed at least periodically. However, there is no easy way to prove that the measures that were taken are still effective to maintain the low radon concentration indoors. This system was used to lower the radon concentration in a kindergarten located in a villa-type house built at the beginning of the 20th century. A central ventilation system was installed in 1990 to decrease radon levels of 900 Bq m23. The efficiency of this action was verified by repeated measurements.
This kindergarten was measured again in the campaign carried out in 2011/2012, and the results were from 900 to 1500 Bq m23 for the long-term average. It should be noted that this building had not undergone any major reconstruction or thermal retrofitting. Again, the radon diagnostic measurements helped in understanding what is going on. Detailed continuous monitoring in all habitable rooms, with the ventilation system working in standard regime for 1 week, and then switched off in the second week, revealed no difference between these two modes (see Figure 5).
152
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
Figure 3. Old and new tight windows in two neighbouring classrooms.
INFLUENCE OF ENERGY-SAVING MEASURES ON THE RADON CONCENTRATION
This led to the conclusion that the remediation system is no longer effective.
TB01SUJB072, and by Programme—Action Plan.
the
Czech
Radon
REFERENCES
CONCLUSION These results showed clearly that recent energy-saving efforts resulting in increased air-tightness of older buildings are accompanied by an accumulation of substances, specifically radon, that have detrimental long-term effects on people’s health. The long-term average indoor radon values increased significantly in Czech kindergartens that have been thermally retrofitted. This does not automatically mean that the children attending these kindergartens are overexposed. The actual impact of the increased air-tightness of buildings on increasing the radon effective dose can be compensated by sufficient ventilation during the time when the rooms are occupied. This was shown by detailed measurements in nearly one-half of the kindergartens with radon levels exceeding the reference value and presented in Figure 4. This study has shown that it is important to make periodic measurements to verify repeatedly that remedial measures are reducing radon levels to an acceptable level while the rooms are occupied. FUNDING The activities reported here were funded by the Czech ˇ R) under Project No. Technological Agency (TAC
1. Milner, J., Shrubsole, C., Das, P., Jones, B., Ridley, I., Chalabi, Z. et al. Home energy efficiency and radon related risk of lung cancer: modelling study. BMJ. 348, f7493 (2014). 2. Jira´nek, M. and Kacˇmarˇ´ıkova´, V. Dealing with the increased radon concentration in thermally-retrofitted buildings. Radiat. Prot. Dosim. 160 (1–3), 43– 47 (2014). 3. RADPAR. Deliverable 13/5 Measurement and Analysis of Radon in Low Energy and Passive Houses in Austria, W. Ringer, J. Gra¨ser. (2012). 4. Fronˇka, A. and Jı´lek, K. Radon entry rate analyses using in-situ tracer gas method application. Radiat. Prot. Dosim. 160(1– 3), 143– 148 (2014). 5. Sleza´kova´, M., Navra´tilova´ Rovenska´, K., Toma´sˇek, L. and Holecˇek, J. Short- and long-term variability of radon progeny concentration in dwellings in the Czech Republic. Radiat. Prot. Dosim. 153(3), 334–341 (2013). First published online 27 June 2012. doi:10.1093/rpd/ncs111. 6. Thinova´, L. and Burian, I. Effective dose assessment for workers in caves in the Czech Republic: experiments with passive radon detectors. Radiat. Prot. Dosim. 130(1), 48–51 (2008). First published online 24 April 2008. doi:10.1093/rpd/ncn118. 7. User guide for Radim3. Jiri Plch – SMM (1998), [in Czech]. 8. Bochicchio, F., Zunic, Z. S., Carpentieri, C., Antignani, S., Venoso, G., Carelli, V., Cordedda, C., Veselinovic, N., Tollefsen, T. and Bossew, P. Radon in indoor air of primary schools: a systematic survey to evaluate factors affecting radon concentration levels and their variability. Indoor Air. (2013). doi:10.1111/ina.12073.
153
Downloaded from http://rpd.oxfordjournals.org/ at Columbia University Libraries on March 3, 2015
Figure 5. Ineffective remedial measure.
