ICRP Publication 126
Radiological Protection against Radon Exposure
Recommended citation
ICRP, 2014. Radiological Protection against Radon Exposure. ICRP Publication 126. Ann. ICRP 43(3).
Authors on behalf of ICRP
J-F. Lecomte, S. Solomon, J. Takala, T. Jung, P. Strand, C. Murith, S. Kiselev, W. Zhuo, F. Shannoun, A. Janssens
Abstract - In this report, the Commission provides updated guidance on radiological protection against radon exposure. The report has been developed considering the latest ICRP recommendations for the system of radiological protection, all available scientific knowledge about the risks of radon, and the experience gained by many organisations and countries in the control of radon exposure. The report describes the characteristics of radon exposure, covering sources and transfer mechanisms, the health risks associated with radon, and the challenges of managing radon exposure.
The Commission recommends an integrated approach for controlling radon exposure, relying as far as possible on the management of buildings or locations in which radon exposure occurs, whatever the use of the building. This approach is based on the optimisation principle, and is graded reflecting the responsibilities of key stakeholders, notably in workplaces, and the intent of the national authorities to control radon exposure. The report also provides recommendations on managing radon exposure when workers’ exposures are considered as occupational, and the appropriate requirements of the Commission should be applied.
© 2014 ICRP. Published by SAGE.
Keywords: Radon exposure; Prevention; Mitigation; Dwellings; Buildings; Workplaces.
AUTHORS ON BEHALF OF ICRP J-F. LECOMTE, S. SOLOMON, J. TAKALA, T. JUNG, P. STRAND, C. MURITH, S. KISELEV, W. ZHUO, F. SHANNOUN, A. JANSSENS
Key Points
People are exposed to radon at home, in workplaces, and in mixed-use buildings. Variability of indoor radon concentrations results in a very heterogeneous distribution of exposures. Outdoor radon exposure is generally not an issue.
There is strong evidence that exposures to radon and its progeny may result in lung cancer. Radon exposure is the second leading cause of lung cancer after smoking.
Radon exposure is an existing exposure situation as the source is unmodified concentrations of ubiquitous primordial natural activity in the earth’s crust. Only pathways can be controlled.
National authorities should characterise the exposure situation and develop a national radon protection strategy. As much radon exposure occurs in the home, this strategy should address exposure in dwellings from a public health perspective, and should have a commitment to reduce the overall exposure of the general population and the highest individual exposures.
The strategy should be straightforward and realistic; integrated, in order to be consistent for all buildings; graded according to the situation and responsibilities; and should not distinguish between smokers and non-smokers. It should be considered in conjunction with other public health policies, such as energy saving, non-smoking, and indoor air quality.
The radon protection strategy should include preventive actions in new buildings and mitigating actions in existing buildings.
The management of radon exposure is mainly based on application of the optimisation principle with an appropriate reference level. This level should correspond to an annual dose in the range of 1–20 mSv as recommended by the Commission. The Commission considers that a value of the order of 10 mSv annual dose should remain a benchmark for setting a reference level for radon exposure.
For practical implementation of the radon protection strategy, the upper value for the derived reference level recommended by the Commission in dwellings continues to be 300 Bq m-3 as an annual mean concentration. The same value is recommended for all other buildings and workplaces.
The Commission strongly encourages national authorities to set a national derived reference level that is as low as reasonably achievable in the range of 100– 300 Bq m-3, taking the prevailing economic and societal circumstances into account.
In most workplaces, radon exposures of workers are adventitious and are not considered to be occupational. The Commission recommends a specific graded approach in workplaces with the following steps:
(i) optimising protection using the common derived reference level for all buildings and workplaces;
(ii) optimising protection using the actual parameters of the exposure situation, such as occupancy, together with a reference level of 10 mSv annual dose; and
(iii) applying the relevant requirements for occupational exposure when, despite all reasonable efforts, the exposure remains above the reference level.
The relevant requirements for occupational exposure apply in workplaces where, from the outset, exposures of workers to radon are considered as occupational by national authorities.
The occupational dose limit should apply when the national authorities consider that the radon exposure situation should be managed as a planned exposure situation.
Executive Summary
(a) The objective of this report is to describe and clarify application of the Commission’s system for protection of members of the public and workers against radon exposures in dwellings, workplaces, and other types of location.
(b) Radon has two main isotopes. Radon-222 is a radioactive decay product of radium-226, which is present in the earth’s crust in varying concentrations. As radon is a gas, it is capable of movement from the soil to indoors. This movement is dependent on various factors such as the type of soil, building, and/or location. Radon-220 is a radioactive decay product of radium-224 in the thorium-232 decay chain that is also present in the earth’s crust. Both radon-222 and radon-220 can also be released from building materials to the indoor atmosphere. The indoor radon concentration can vary by several orders of magnitude from one building to another. The focus of this report is radon-222.
(c) Radon can be inhaled; as it is inert, nearly all of the gas inhaled is subsequently exhaled. However, the inhaled short-lived radon progeny aerosol can deposit within the respiratory tract. Depending on the diffusion properties of the aerosol, the decay products present in the air deposit in the nasal cavities, on the walls of the bronchial tubes, and in the deep lung. Two of these short-lived progeny, polonium-218 and polonium-214, emit alpha particles, and the energy deposited by these alpha particles represents the major contributor to radiation exposure that may lead to health effects.
(d) In Publication 115 (ICRP, 2010), the Commission reviewed and analysed epidemiological studies on the association between lung cancer and radon exposures (ICRP, 2010). For both underground mines and homes, there is strong evidence that radon and its progeny can cause lung cancer. As a consequence, the Commission recommended, for radiological protection purposes, a detriment-adjusted nominal risk coefficient for lung cancer in a mixed adult population of non-smokers and smokers of 8 x 10-10 per Bq h m-3 for exposure to radon-222 gas in equilibrium with its progeny [5 x 10-4 per working level month (WLM)]. This is approximately twice the value used by the Commission in Publication 65 (ICRP, 1993). For solid tumours other than lung cancer and leukaemia, there is no consistent evidence, to date, for increased incidence associated with exposures to radon and its progeny.
(e) Within the system of radiological protection, radon exposure has the characteristics of an existing exposure situation as the source is unmodified concentrations of ubiquitous primordial natural activity in the earth’s crust (ICRP, 2007). Human activities such as construction of buildings or operation of mines may create or modify pathways that increase exposure to radon and its progeny. These pathways can be controlled by preventive and mitigating actions. However, the source itself cannot be modified, and thus already exists when a decision on control has to be taken. However, in some workplaces, the radon exposure situation may be deemed to be a planned exposure situation from the outset by national authorities. Such workplaces include uranium mines associated with the nuclear fuel cycle
(f) Radon is not likely to give rise to an emergency exposure situation, although the discovery of very high concentrations in a location may require the prompt implementation of protective actions.
(g) The philosophy of Publication 103 (ICRP, 2007) compared with Publication 60 (ICRP, 1991) is to recommend a consistent approach for the management of all types of exposure situations. This approach is based on application of the optimisation principle implemented using appropriate individual dose restrictions: dose constraints or reference levels. Optimisation involves endeavouring to reduce doses as far below constraints or reference levels as is reasonably achievable, regardless of the initial level of exposure.
(h) Day-to-day life at home and at work inevitably leads to some exposure to radon. In common with many other existing exposure situations, radon exposures can be very heterogeneous. The level of exposure is highly dependent upon individual behaviour. The role of self-help protective actions is therefore crucial. The characterisation of the exposure situation is a prerequisite to its control. Domestic radon exposure management should address a number of issues (e.g. environmental, health, economic, architectural, and educational) involving a wide range of stakeholders.
(i) Control of indoor radon exposure poses many challenges. As individuals move from place to place in the same area, a radon protection strategy should be developed by national authorities, and implemented in a consistent and integrated manner in the various locations. As much radon exposure occurs in the home, a radon protection strategy should address exposure in dwellings from a public health perspective. In many buildings, the level of radon can be well above the concentration that has been shown to represent potential health risks, and a commitment is needed to reduce overall exposure of the general population and the highest individual exposures. The strategy should be straightforward, appropriately scaled with other health hazards, supported and implemented on a long-term basis, and involve all stakeholders.
(j) The national radon protection strategy also has to address these challenges in terms of responsibilities, notably the responsibility of the individual householder towards the occupants, of the builder or the seller of a property towards the buyer, of the landlord towards the tenant, of the employer towards the employee, and, generally speaking, of the responsible person for any building towards its users. All of these factors impact on the potential for enforcement of the radon strategy.
(k) The range of responsibilities drives the need for a radon strategy that is based on effectiveness and realism. Any radon protection strategy should aim to maintain and/or reduce radon concentrations to a level that is as low as reasonably achievable, keeping in mind that it is not feasible to eliminate indoor radon completely.
(l) The Commission considers that, in most situations, a national radon protection strategy would be justified as radon is ubiquitous; it represents a significant source of radiation exposure, being the second leading cause of lung cancer after smoking; and, in most circumstances, it can be controlled. A radon protection strategy can also have positive consequences on other public health policies such as tobacco control and indoor air quality. Characterisation of the situation, including the assessment of radon concentrations and identification of radon-prone areas, as well as considerations about public health priorities and social and economic factors, are necessary for national authorities to frame and implement a radon protection strategy. Although the absolute risk of lung cancer arising from radon exposure is significantly greater in smokers than in non-smokers, the Commission’s recommendations for protection against radon do not distinguish between smokers and non-smokers.
(m) Characterisation of the exposure situation is also a prerequisite for application of the optimisation principle. This principle is the driver for controlling radon exposure in order to maintain or reduce exposure to a level that is as low as reasonably achievable, taking the prevailing economic and societal circumstances into account. As with the control of other sources of radiation, the Commission recommends the use of a source-related individual dose restriction in conjunction with the optimisation of protection.
(n) It is the responsibility of the appropriate national authorities, as with other radiation sources, to establish their own national reference levels of dose and derived reference level of concentration, and to apply the process of optimisation of protection within their country. The objective is both to reduce the overall risk to the general population and, for the sake of equity, the individual risk to the most exposed individuals. In both cases, the process is implemented mainly through the management of buildings rather than individual exposures, and should result in radon concentrations in ambient indoor air that are as low as reasonably achievable below the national reference level.
(o) Radon exposure can only be controlled by actions on exposure pathways. Individuals gain benefit from the situation, and support is provided to individuals to reduce their doses. Given these considerations, the appropriate reference level should correspond to an annual dose in the range of 1–20 mSv, as recommended by the Commission for existing exposure situations (ICRP, 2007, Table 5). The Commission considers that a value of the order of 10 mSv, as indicated in Publication 65 (ICRP, 1993), should remain a benchmark for setting a reference level for radon exposure.
(p) As most radon control measures are applied to buildings, it is appropriate to establish derived reference levels for radon set in terms of concentration in air, which is a measurable quantity, expressed in Becquerel per cubic metre (Bq m-3 ). In Publication 103 (ICRP, 2007), the Commission recommended upper values for derived reference levels of 600 Bq m-3 for homes and 1500 Bq m-3 for workplaces. In response to its review of radon epidemiology in Publication 115 (ICRP, 2010) and the increase of the nominal risk coefficient by approximately a factor of 2, the Commission reduced the upper reference level for homes to 300 Bq m-3 in the associated Statement on Radon. A radon concentration of 300 Bq m-3 in homes corresponds to an annual dose of approximately 10 mSv using the dose conversion convention, based on the revised nominal risk coefficient (ICRP, 2010). The Statement on Radon also referred to a level of 1000 Bq m-3 as an entry point for applying occupational radiological protection requirements, replacing the upper reference level of 1500 Bq m-3.
(q) In its Statement on Radon, the Commission also signalled its intention to publish dose coefficients for intakes of radon and its progeny calculated using reference biokinetic and dosimetric models. Based on new dose coefficients, 300 Bq m-3 corresponds to a higher annual dose but within the range of 1–20 mSv in homes.
(r) For the practical implementation of a radon protection strategy, the Commission continues to recommend an upper value of the derived reference level of 300 Bq m-3 for radon-222 in dwellings. The Commission strongly encourages national authorities to set a national derived reference level that is as low as reasonably achievable in the range of 100–300 Bq m-3, taking the prevailing economic and societal circumstances into account. This is consistent with the ICRP Statement on Radon (ICRP, 2010) and the World Health Organization’s (WHO) Handbook on Indoor Radon (WHO, 2009). In assessing compliance with the derived reference level, measurements should be representative of the annual mean concentration of radon in a building or location.
(s) For simplicity, considering that individuals going from place to place in the same area in their daily life should be protected on the same basis, regardless of the location, the Commission recommends using the same upper value of 300 Bq m-3 in mixed-use buildings, which are used by both members of the public and workers.
(t) The Commission now recommends that a graded approach should be applied for the control of radon exposures. In such an approach, the radon protection strategy should start with a programme that aims to encourage relevant decision makers to promote self-help protective actions, such as measurement and, if needed, remediation. This process can be implemented through information, advice, assistance, and, where necessary, more formal requirements. The use and level of enforcement of these various actions should be dependent upon the degree of legal responsibility for the situation, and the level of ambition of the national radon protection strategy.
(u) A specific graded approach should be implemented for workplaces, replacing the entry level of 1000 Bq m-3 for applying occupational protection requirements. Where workers’ exposure to radon is not considered as occupational (e.g. office buildings), the first step is to reduce the concentration of radon to a level that is as low as reasonably achievable below the same derived reference level as set for dwellings. The corresponding annual dose is usually lower than that in dwellings, because the time spent in workplaces is usually less than the time spent at home. If difficulties are met in the first step, a more realistic approach is recommended as a second step, consisting of optimising protection using the actual parameters of the exposure situation, such as occupancy, together with a reference level of the order of 10 mSv annual dose.
(v) If, despite all reasonable efforts to reduce radon exposure in workplaces, the exposure persists above the reference level expressed in dose, the workers should be considered as occupationally exposed. In such cases, the Commission recommends application of the relevant requirements for occupational exposure (ICRP, 2007, Section 5.4.1).
(w) The Commission also recommends application of the same requirements in workplaces where, from the outset, exposure of workers to radon is considered as occupational by national authorities. Such workplaces may include thermal spas, caves, and other underground workplaces.
(x) Regardless of whether or not workers are considered as occupationally exposed, their exposure should be kept below the upper value of the range for existing exposure situations (20 mSv year-1). The occupational dose limit should apply when the national authorities consider that the radon exposure situation should be managed as a planned exposure situation.
(y) To be effective, the national radon protection strategy should be established with a long-term perspective. The process for significantly reducing the risks of radon to the general population usually takes several decades of consistent effort, rather than several years. The Commission considers that, for the sake of clarification, the distinction should be made between prevention, aiming to - maintain exposure at a level that is as low as reasonably achievable under the prevailing circumstances, especially in new buildings, and mitigation, aiming to reduce exposure to a level that is as low as reasonably achievable in existing buildings.
(z) As a consequence, a radon protection strategy should include preventive actions. Regardless of the indoor location, the category of individuals present, and the type of exposure situation, it is possible to address radon exposure by considering the issue of radon exposure during the planning, design, and construction phases of a building. Preventive actions are implemented through land planning and building codes for new buildings, and for renovation of old buildings. This also means the integration of the radon protection strategy in a manner consistent with other strategies concerning buildings, such as indoor air quality or energy saving, in order to develop synergies and avoid contradictions.
(aa) The mitigation part of the national radon protection strategy addresses existing buildings and locations. As far as possible in such cases, the control of exposure should be ensured through the management of the building or location and the conditions of its use, whatever the category of individuals present. The main steps are measurements and, when needed, corrective actions to mitigate exposures.
(bb) The national radon protection strategy should be implemented through a national radon action plan established by national authorities with the involvement of relevant stakeholders. The action plan should establish a framework with a clear infrastructure, determine priorities and responsibilities, and describe the successive steps to deal with radon in the country. Depending on the exposure conditions, it should identify stakeholders, such as those who are exposed and those who should provide support or implement action; address ethical issues, particularly those associated with responsibilities; and provide information, guidance, support, and conditions for sustainability.
(cc) The national action plan should also deal with radon measurement techniques and protocols; radon surveys to identify radon-prone areas; methods for mitigating radon exposure and their applicability in different situations; supporting policies, including information, training, and involvement of stakeholders; and assessment of effectiveness. The issue of buildings with public access and workplaces should also be addressed with a specific graded approach reflecting legal responsibilities. The national action plan should be evaluated and reviewed periodically, including the value of the derived reference level.
ICRP, 2014. Radiological Protection against Radon Exposure. ICRP Publication 126. Ann. ICRP 43(3).
Authors on behalf of ICRP
J-F. Lecomte, S. Solomon, J. Takala, T. Jung, P. Strand, C. Murith, S. Kiselev, W. Zhuo, F. Shannoun, A. Janssens
Abstract - In this report, the Commission provides updated guidance on radiological protection against radon exposure. The report has been developed considering the latest ICRP recommendations for the system of radiological protection, all available scientific knowledge about the risks of radon, and the experience gained by many organisations and countries in the control of radon exposure. The report describes the characteristics of radon exposure, covering sources and transfer mechanisms, the health risks associated with radon, and the challenges of managing radon exposure.
The Commission recommends an integrated approach for controlling radon exposure, relying as far as possible on the management of buildings or locations in which radon exposure occurs, whatever the use of the building. This approach is based on the optimisation principle, and is graded reflecting the responsibilities of key stakeholders, notably in workplaces, and the intent of the national authorities to control radon exposure. The report also provides recommendations on managing radon exposure when workers’ exposures are considered as occupational, and the appropriate requirements of the Commission should be applied.
© 2014 ICRP. Published by SAGE.
Keywords: Radon exposure; Prevention; Mitigation; Dwellings; Buildings; Workplaces.
AUTHORS ON BEHALF OF ICRP J-F. LECOMTE, S. SOLOMON, J. TAKALA, T. JUNG, P. STRAND, C. MURITH, S. KISELEV, W. ZHUO, F. SHANNOUN, A. JANSSENS
Key Points
People are exposed to radon at home, in workplaces, and in mixed-use buildings. Variability of indoor radon concentrations results in a very heterogeneous distribution of exposures. Outdoor radon exposure is generally not an issue.
There is strong evidence that exposures to radon and its progeny may result in lung cancer. Radon exposure is the second leading cause of lung cancer after smoking.
Radon exposure is an existing exposure situation as the source is unmodified concentrations of ubiquitous primordial natural activity in the earth’s crust. Only pathways can be controlled.
National authorities should characterise the exposure situation and develop a national radon protection strategy. As much radon exposure occurs in the home, this strategy should address exposure in dwellings from a public health perspective, and should have a commitment to reduce the overall exposure of the general population and the highest individual exposures.
The strategy should be straightforward and realistic; integrated, in order to be consistent for all buildings; graded according to the situation and responsibilities; and should not distinguish between smokers and non-smokers. It should be considered in conjunction with other public health policies, such as energy saving, non-smoking, and indoor air quality.
The radon protection strategy should include preventive actions in new buildings and mitigating actions in existing buildings.
The management of radon exposure is mainly based on application of the optimisation principle with an appropriate reference level. This level should correspond to an annual dose in the range of 1–20 mSv as recommended by the Commission. The Commission considers that a value of the order of 10 mSv annual dose should remain a benchmark for setting a reference level for radon exposure.
For practical implementation of the radon protection strategy, the upper value for the derived reference level recommended by the Commission in dwellings continues to be 300 Bq m-3 as an annual mean concentration. The same value is recommended for all other buildings and workplaces.
The Commission strongly encourages national authorities to set a national derived reference level that is as low as reasonably achievable in the range of 100– 300 Bq m-3, taking the prevailing economic and societal circumstances into account.
In most workplaces, radon exposures of workers are adventitious and are not considered to be occupational. The Commission recommends a specific graded approach in workplaces with the following steps:
(i) optimising protection using the common derived reference level for all buildings and workplaces;
(ii) optimising protection using the actual parameters of the exposure situation, such as occupancy, together with a reference level of 10 mSv annual dose; and
(iii) applying the relevant requirements for occupational exposure when, despite all reasonable efforts, the exposure remains above the reference level.
The relevant requirements for occupational exposure apply in workplaces where, from the outset, exposures of workers to radon are considered as occupational by national authorities.
The occupational dose limit should apply when the national authorities consider that the radon exposure situation should be managed as a planned exposure situation.
Executive Summary
(a) The objective of this report is to describe and clarify application of the Commission’s system for protection of members of the public and workers against radon exposures in dwellings, workplaces, and other types of location.
(b) Radon has two main isotopes. Radon-222 is a radioactive decay product of radium-226, which is present in the earth’s crust in varying concentrations. As radon is a gas, it is capable of movement from the soil to indoors. This movement is dependent on various factors such as the type of soil, building, and/or location. Radon-220 is a radioactive decay product of radium-224 in the thorium-232 decay chain that is also present in the earth’s crust. Both radon-222 and radon-220 can also be released from building materials to the indoor atmosphere. The indoor radon concentration can vary by several orders of magnitude from one building to another. The focus of this report is radon-222.
(c) Radon can be inhaled; as it is inert, nearly all of the gas inhaled is subsequently exhaled. However, the inhaled short-lived radon progeny aerosol can deposit within the respiratory tract. Depending on the diffusion properties of the aerosol, the decay products present in the air deposit in the nasal cavities, on the walls of the bronchial tubes, and in the deep lung. Two of these short-lived progeny, polonium-218 and polonium-214, emit alpha particles, and the energy deposited by these alpha particles represents the major contributor to radiation exposure that may lead to health effects.
(d) In Publication 115 (ICRP, 2010), the Commission reviewed and analysed epidemiological studies on the association between lung cancer and radon exposures (ICRP, 2010). For both underground mines and homes, there is strong evidence that radon and its progeny can cause lung cancer. As a consequence, the Commission recommended, for radiological protection purposes, a detriment-adjusted nominal risk coefficient for lung cancer in a mixed adult population of non-smokers and smokers of 8 x 10-10 per Bq h m-3 for exposure to radon-222 gas in equilibrium with its progeny [5 x 10-4 per working level month (WLM)]. This is approximately twice the value used by the Commission in Publication 65 (ICRP, 1993). For solid tumours other than lung cancer and leukaemia, there is no consistent evidence, to date, for increased incidence associated with exposures to radon and its progeny.
(e) Within the system of radiological protection, radon exposure has the characteristics of an existing exposure situation as the source is unmodified concentrations of ubiquitous primordial natural activity in the earth’s crust (ICRP, 2007). Human activities such as construction of buildings or operation of mines may create or modify pathways that increase exposure to radon and its progeny. These pathways can be controlled by preventive and mitigating actions. However, the source itself cannot be modified, and thus already exists when a decision on control has to be taken. However, in some workplaces, the radon exposure situation may be deemed to be a planned exposure situation from the outset by national authorities. Such workplaces include uranium mines associated with the nuclear fuel cycle
(f) Radon is not likely to give rise to an emergency exposure situation, although the discovery of very high concentrations in a location may require the prompt implementation of protective actions.
(g) The philosophy of Publication 103 (ICRP, 2007) compared with Publication 60 (ICRP, 1991) is to recommend a consistent approach for the management of all types of exposure situations. This approach is based on application of the optimisation principle implemented using appropriate individual dose restrictions: dose constraints or reference levels. Optimisation involves endeavouring to reduce doses as far below constraints or reference levels as is reasonably achievable, regardless of the initial level of exposure.
(h) Day-to-day life at home and at work inevitably leads to some exposure to radon. In common with many other existing exposure situations, radon exposures can be very heterogeneous. The level of exposure is highly dependent upon individual behaviour. The role of self-help protective actions is therefore crucial. The characterisation of the exposure situation is a prerequisite to its control. Domestic radon exposure management should address a number of issues (e.g. environmental, health, economic, architectural, and educational) involving a wide range of stakeholders.
(i) Control of indoor radon exposure poses many challenges. As individuals move from place to place in the same area, a radon protection strategy should be developed by national authorities, and implemented in a consistent and integrated manner in the various locations. As much radon exposure occurs in the home, a radon protection strategy should address exposure in dwellings from a public health perspective. In many buildings, the level of radon can be well above the concentration that has been shown to represent potential health risks, and a commitment is needed to reduce overall exposure of the general population and the highest individual exposures. The strategy should be straightforward, appropriately scaled with other health hazards, supported and implemented on a long-term basis, and involve all stakeholders.
(j) The national radon protection strategy also has to address these challenges in terms of responsibilities, notably the responsibility of the individual householder towards the occupants, of the builder or the seller of a property towards the buyer, of the landlord towards the tenant, of the employer towards the employee, and, generally speaking, of the responsible person for any building towards its users. All of these factors impact on the potential for enforcement of the radon strategy.
(k) The range of responsibilities drives the need for a radon strategy that is based on effectiveness and realism. Any radon protection strategy should aim to maintain and/or reduce radon concentrations to a level that is as low as reasonably achievable, keeping in mind that it is not feasible to eliminate indoor radon completely.
(l) The Commission considers that, in most situations, a national radon protection strategy would be justified as radon is ubiquitous; it represents a significant source of radiation exposure, being the second leading cause of lung cancer after smoking; and, in most circumstances, it can be controlled. A radon protection strategy can also have positive consequences on other public health policies such as tobacco control and indoor air quality. Characterisation of the situation, including the assessment of radon concentrations and identification of radon-prone areas, as well as considerations about public health priorities and social and economic factors, are necessary for national authorities to frame and implement a radon protection strategy. Although the absolute risk of lung cancer arising from radon exposure is significantly greater in smokers than in non-smokers, the Commission’s recommendations for protection against radon do not distinguish between smokers and non-smokers.
(m) Characterisation of the exposure situation is also a prerequisite for application of the optimisation principle. This principle is the driver for controlling radon exposure in order to maintain or reduce exposure to a level that is as low as reasonably achievable, taking the prevailing economic and societal circumstances into account. As with the control of other sources of radiation, the Commission recommends the use of a source-related individual dose restriction in conjunction with the optimisation of protection.
(n) It is the responsibility of the appropriate national authorities, as with other radiation sources, to establish their own national reference levels of dose and derived reference level of concentration, and to apply the process of optimisation of protection within their country. The objective is both to reduce the overall risk to the general population and, for the sake of equity, the individual risk to the most exposed individuals. In both cases, the process is implemented mainly through the management of buildings rather than individual exposures, and should result in radon concentrations in ambient indoor air that are as low as reasonably achievable below the national reference level.
(o) Radon exposure can only be controlled by actions on exposure pathways. Individuals gain benefit from the situation, and support is provided to individuals to reduce their doses. Given these considerations, the appropriate reference level should correspond to an annual dose in the range of 1–20 mSv, as recommended by the Commission for existing exposure situations (ICRP, 2007, Table 5). The Commission considers that a value of the order of 10 mSv, as indicated in Publication 65 (ICRP, 1993), should remain a benchmark for setting a reference level for radon exposure.
(p) As most radon control measures are applied to buildings, it is appropriate to establish derived reference levels for radon set in terms of concentration in air, which is a measurable quantity, expressed in Becquerel per cubic metre (Bq m-3 ). In Publication 103 (ICRP, 2007), the Commission recommended upper values for derived reference levels of 600 Bq m-3 for homes and 1500 Bq m-3 for workplaces. In response to its review of radon epidemiology in Publication 115 (ICRP, 2010) and the increase of the nominal risk coefficient by approximately a factor of 2, the Commission reduced the upper reference level for homes to 300 Bq m-3 in the associated Statement on Radon. A radon concentration of 300 Bq m-3 in homes corresponds to an annual dose of approximately 10 mSv using the dose conversion convention, based on the revised nominal risk coefficient (ICRP, 2010). The Statement on Radon also referred to a level of 1000 Bq m-3 as an entry point for applying occupational radiological protection requirements, replacing the upper reference level of 1500 Bq m-3.
(q) In its Statement on Radon, the Commission also signalled its intention to publish dose coefficients for intakes of radon and its progeny calculated using reference biokinetic and dosimetric models. Based on new dose coefficients, 300 Bq m-3 corresponds to a higher annual dose but within the range of 1–20 mSv in homes.
(r) For the practical implementation of a radon protection strategy, the Commission continues to recommend an upper value of the derived reference level of 300 Bq m-3 for radon-222 in dwellings. The Commission strongly encourages national authorities to set a national derived reference level that is as low as reasonably achievable in the range of 100–300 Bq m-3, taking the prevailing economic and societal circumstances into account. This is consistent with the ICRP Statement on Radon (ICRP, 2010) and the World Health Organization’s (WHO) Handbook on Indoor Radon (WHO, 2009). In assessing compliance with the derived reference level, measurements should be representative of the annual mean concentration of radon in a building or location.
(s) For simplicity, considering that individuals going from place to place in the same area in their daily life should be protected on the same basis, regardless of the location, the Commission recommends using the same upper value of 300 Bq m-3 in mixed-use buildings, which are used by both members of the public and workers.
(t) The Commission now recommends that a graded approach should be applied for the control of radon exposures. In such an approach, the radon protection strategy should start with a programme that aims to encourage relevant decision makers to promote self-help protective actions, such as measurement and, if needed, remediation. This process can be implemented through information, advice, assistance, and, where necessary, more formal requirements. The use and level of enforcement of these various actions should be dependent upon the degree of legal responsibility for the situation, and the level of ambition of the national radon protection strategy.
(u) A specific graded approach should be implemented for workplaces, replacing the entry level of 1000 Bq m-3 for applying occupational protection requirements. Where workers’ exposure to radon is not considered as occupational (e.g. office buildings), the first step is to reduce the concentration of radon to a level that is as low as reasonably achievable below the same derived reference level as set for dwellings. The corresponding annual dose is usually lower than that in dwellings, because the time spent in workplaces is usually less than the time spent at home. If difficulties are met in the first step, a more realistic approach is recommended as a second step, consisting of optimising protection using the actual parameters of the exposure situation, such as occupancy, together with a reference level of the order of 10 mSv annual dose.
(v) If, despite all reasonable efforts to reduce radon exposure in workplaces, the exposure persists above the reference level expressed in dose, the workers should be considered as occupationally exposed. In such cases, the Commission recommends application of the relevant requirements for occupational exposure (ICRP, 2007, Section 5.4.1).
(w) The Commission also recommends application of the same requirements in workplaces where, from the outset, exposure of workers to radon is considered as occupational by national authorities. Such workplaces may include thermal spas, caves, and other underground workplaces.
(x) Regardless of whether or not workers are considered as occupationally exposed, their exposure should be kept below the upper value of the range for existing exposure situations (20 mSv year-1). The occupational dose limit should apply when the national authorities consider that the radon exposure situation should be managed as a planned exposure situation.
(y) To be effective, the national radon protection strategy should be established with a long-term perspective. The process for significantly reducing the risks of radon to the general population usually takes several decades of consistent effort, rather than several years. The Commission considers that, for the sake of clarification, the distinction should be made between prevention, aiming to - maintain exposure at a level that is as low as reasonably achievable under the prevailing circumstances, especially in new buildings, and mitigation, aiming to reduce exposure to a level that is as low as reasonably achievable in existing buildings.
(z) As a consequence, a radon protection strategy should include preventive actions. Regardless of the indoor location, the category of individuals present, and the type of exposure situation, it is possible to address radon exposure by considering the issue of radon exposure during the planning, design, and construction phases of a building. Preventive actions are implemented through land planning and building codes for new buildings, and for renovation of old buildings. This also means the integration of the radon protection strategy in a manner consistent with other strategies concerning buildings, such as indoor air quality or energy saving, in order to develop synergies and avoid contradictions.
(aa) The mitigation part of the national radon protection strategy addresses existing buildings and locations. As far as possible in such cases, the control of exposure should be ensured through the management of the building or location and the conditions of its use, whatever the category of individuals present. The main steps are measurements and, when needed, corrective actions to mitigate exposures.
(bb) The national radon protection strategy should be implemented through a national radon action plan established by national authorities with the involvement of relevant stakeholders. The action plan should establish a framework with a clear infrastructure, determine priorities and responsibilities, and describe the successive steps to deal with radon in the country. Depending on the exposure conditions, it should identify stakeholders, such as those who are exposed and those who should provide support or implement action; address ethical issues, particularly those associated with responsibilities; and provide information, guidance, support, and conditions for sustainability.
(cc) The national action plan should also deal with radon measurement techniques and protocols; radon surveys to identify radon-prone areas; methods for mitigating radon exposure and their applicability in different situations; supporting policies, including information, training, and involvement of stakeholders; and assessment of effectiveness. The issue of buildings with public access and workplaces should also be addressed with a specific graded approach reflecting legal responsibilities. The national action plan should be evaluated and reviewed periodically, including the value of the derived reference level.
