Radon Control in Housing
From the beginning of its formation, the Earth’s crust contains chemical elements which form natural radiation background. One of them is radon – the gas without odor, colour and taste. It is generated in several ways, one of the most common ways is generation in the process of natural radioactive decay of uranium contained in rocks and soils. Radon is the only noble gas without stable and long-lived isotopes. It is soluble in blood, water and other body fluids, much better soluble in fats what causes its effective absorption by adipose tissue at body intake. Radon can penetrate into the body even through the intact skin.
Due to its low reactivity, radon itself does not pose a serious health threat. However, the radiotoxicity of its progeny – polonium, bismuth and lead short-lived isotopes – is very high. In the environment, radon daughter products, which are metals, interact with the smallest particles of dust, water drops, forming a mixture which is inhaled by humans and penetrates to the lower, most vulnerable parts of the respiratory tract. The human bronchopulmonary system is a target for radon daughter products. The decay of radon nuclei and its daughter isotopes in the lung tissue causes micro-burns, since all the energy of alpha particles is absorbed at the decay point.
Unknowingly, even at being home screened by high fencing and strong walls, we expose ourselves to radon hazard with only one closed window. Ventilation of the rooms is a necessity, but how great this necessity can be it depends on the quality of ventilation and building materials used to construct the building you live in and, of course, on building distance from the ground. So, the lower floors, especially the basements, undergo a high radon risk, this fact is confirmed by numerous studies, but today we do not attribute importance to it, although it’s a big mistake.
According to the WHO Report, up to 14% of all lung cancers in the world are due to human exposure to this radioactive gas. At 100 Bq/m3 indoor radon concentration, the risk of lung cancer increases to 16%.
Radon hazard at construction
In general, radon content in the soil and indoor air is determined by geological component of the territory, rocks, content of natural radionuclides, presence of tectonic deformations and other factors. In Ukraine, the greatest potential radon danger exists within Ukrainian Crystalline Shield – an area which stretches along the middle reaches of the Dnieper and is 1000 km long and about 250 km wide.
According to the data of the Ministry of Health, more than 20% of available housing of Ukraine does not comply with the requirements for radon content in indoor air. In compliance with Article 15 of the Law of Ukraine “On Human Protection against Impact of Ionizing Radiation”, human exposure within dwellings and industrial premises shall not exceed the regulated values approved in compliance with the established procedure. The Law defines measures aimed at human protection against impact of radionuclides contained in the construction materials. These measures include, in particular, siting, designing and erecting buildings and structures considering protection from radon ingress into the air of these buildings; industrial control over radionuclides content in building materials, acceptance of buildings and structures into operation considering the level of radon content in the air of these buildings and structures and gamma-radiation level; change of the nature of the use of buildings and structures, if the actual doses of human exposure exceed the standards approved in compliance with the established procedure; prohibition of the use of construction materials and products made of them which do not comply with the requirements for human protection from the effects of ionizing radiation, etc.
But let each of us answer the question: “How often are we interested in the results of radiation survey of the construction site we are planning to invest in?”. The answer is evident – never. This information can be requested from the builder by a person who works in the radiation protection field. That is to say that we ignore our safety and safety of our children already at the initial stage.
Both human external and internal exposure are the consequences of radioactivity of building materials.
External exposure depends directly on the level of radioactivity in construction materials and occurs due to exposure with 226Ra, 232Th and 40K radionuclides contained in this material. Internal exposure is caused by inhalation of 222Rn radioactive gas and its decay products through the respiratory organs.
Indoor external exposure occurs mainly due to gamma-emitting natural radionuclides contained in construction materials. At the same time, the higher is the content of these radionuclides, the higher is the level of gamma radiation.
In compliance with current regulations (NRBU-97), in existing buildings and structures of permanent attendance, the absorbed dose rate for gamma radiation in the indoor air should not exceed 0.44 μGy/h or 50 μR/h. At commissioning of construction sites of permanent attendance, the absorbed dose rate for gamma radiation in the air should not exceed 0.28 μGy/h or 30 μR/h. It should be noted that the abovementioned gamma radiation levels include the natural component.
As it was mentioned above, the internal exposure of people who live in buildings is determined by 222Rn and its decay products. 222Rn, which is a decay product of 226Ra, diffuses from building structures into the air of residential and industrial premises and, together with the decay products, is inhaled through lungs irradiating the lung tissue.
In compliance with current regulations, the control of the impact of radioactive substances in construction sector is carried out by several parameters:
– effective specific activity of natural radionuclides in construction materials and mineral raw materials;
– absorbed dose rate for gamma radiation in the indoor air of buildings and structures;
– average annual equivalent equilibrium volumetric activity of 222Rn and thoron in the indoor air.
In compliance with the Radiation Safety Standard of Ukraine (NRBU-97), all construction materials are subdivided into the following four classes according to the value of effective specific activity of natural radionuclides and possibility of their use in construction:
Class I — effective specific activity of natural radionuclides constitutes not more than 370 Bq/kg. Such building materials can be used for all types of construction without restrictions.
Class II — effective specific activity of natural radionuclides constitutes 370-740 Bq/kg. Such building materials can be used for road and industrial building construction within the settlements.
Class III — effective specific activity of natural radionuclides constitutes 740—1350 Bq/kg. Such building materials can be used within the settlements for construction of underground structures, as well as outside the settlements for construction of roads, dams, etc.
Class IV — effective specific activity of natural radionuclides exceeds 1350 Bq/kg. The permission of the Ministry of Health of Ukraine is required for the use of such building materials in every particular case.
The legislation of Ukraine regulates the average annual equivalent equilibrium volumetric activity of radon. Radiation Safety Standard of Ukraine sets the content of 222Rn and 220Th in the indoor air. In case of building or structure commissioning after completion of construction or reconstruction, the permissible content of 222Rn in the air of operation rooms of permanent attendance makes 50 Bq/m3, and for 220Th – 3 Bq/m3. For existing buildings and structures of permanent attendance, the content of 222Rn in the air of existing buildings and structures should not exceed 100 Bq/m3 and the content of thoron – 6 Bq/m3.
In Ukraine, permissible levels of 222Rn content in the indoor air are controlled much stricter than in European countries. The International Commission on Radiological Protection proposes a value of 300 Bq/m3 as acceptable for residential buildings (until 2010 it was even higher – 600 Bq/m3). The Council Directive/2013/59/Euratom envisages the same reference level for the average annual concentration of radon in the air (unless the circumstances at the local level require otherwise).
Action plan for 2020-2024 to reduce the risk of radon and its decay product exposure to the population, minimize long-term risks from radon spreading inside residential and non-residential buildings and at workplaces.
The Council Directive 2013/59/Euratom, dated 5 December 2013, is one of the basic documents that directs the efforts of the Member States of the European Union to achieve the population well-being standards in the context of protection against ionizing radiation, including 222Rn. One of its requirements is the commitment of Member States to develop sound strategies to implement these standards.
As a member of the European Council, Ukraine committed to implement the requirements of this document and ensure effective protection of population from radon pollution. The Directive had to be fully implemented in our country by November 2016. At the same time, any regulations adopted to implement the Directive had to be enforced by 6 February, 2018. In the course of implementation of the Directive provisions, “the databases on exposure of the representative population groups to radon, as part of the State System for Monitoring and Registration of Individual Doses of Population of Ukraine” had to be created in Ukraine by 2018. However, this Directive indicator was not implemented.
Finally, in November 2019, the Cabinet of Ministers of Ukraine approved the National Radon Action Plan which in its content complies with the requirements of the Basic Safety Standards (BSS) of the International Atomic Energy Agency (IAEA) and the European Atomic Energy Community (Euratom). The preparation and development of the main provisions of this Action Plan included a preliminary analysis of the situation in Ukraine on radon hazard in residential sector, analysis of current regulatory framework and resources with respect to radiation protection, definition of priorities, etc.
In compliance with the content of the Action Plan for 2020-2024 to reduce the risk of radon and its decay product exposure to the population, minimize long-term risks from radon spreading inside residential and non-residential buildings and at workplaces, the Ministry of Health of Ukraine, SNRIU and the National Academy of Medical Sciences committed to develop and approve in 2020 the procedure and methodology of radon monitoring in Ukraine and notification on radiation risks. In addition, para. 3 of Radon Action Plan provided for the establishment of a system of control of the quality and effectiveness of radon countermeasures at the state level. At the same time, local public administrations are responsible for monitoring radon risks.
“The analysis of accumulated information on radon in the indoor air, assessment of existing radiation risks for the population and specification of priority regions for radon monitoring and radon countermeasures” had to be carried out in 2020. However, according to the latest information, this stanrad remains unimplemented, since such analysis has never been performed.
At the same time, according to NGO “Flora”, effective population protection from radon contamination is vital for certain regions. One of such regions is Kirovograd Oblast. Excessive radon concentrations in the premises of regional childcare and educational institutions were detected in the framework of implementation of Stop Radon regional program. In addition, similar measurements were carried out during the implementation of the comprehensive program of population protection against ionizing radiation implemented during 2014-2018. However, the obtained data are not systematized and visualized to understand the risk of human exposure on separate territories of Kirovograd Oblast.
In contrast to Ukraine, radon problem is studied much more actively in the world. Many countries have and successfully implement their national action plans to reduce radon impact on the human body. Such plans are multifunctional and include the development of a regulatory framework, communication with stakeholders, development of national measurement protocols, development of radon requirements for construction standards and requirements for reduction of radon concentrations in in-service buildings, etc.
In developed countries, such as USA, Canada, France, Switzerland, Belgium, Czech Republic, etc., radon action plans were developed and implemented.
The Swedish Radiation Safety Authority estimates that radon gas in the indoor air causes around 500 cases of lung cancer annually in Sweden. In accordance with the abovementioned Directive, a national action plan for dealing with the long-term risks of radon exposure has been produced by the Swedish Radiation Safety Authority together with the following central government bodies: Swedish Work Environment Authority, Swedish National Board of Housing, Building and Planning, Public Health Agency of Sweden, National Food Agency, Geological Survey of Sweden (SGU) and the Swedish Board for Accreditation and Conformity Assessment (SWEDAC).
This plan envisages running a radon campaign as a part of a long-term communication program to promote measurement of radon and to encourage competent authorities to reduce radon concentrations; coordination of public sector information initiatives relating to radon to make comprehensive communication readily accessible; provision of public authorities with mechanisms to bring radon concentration in all dwellings to 200 Bq/m3, etc.
One of the illustrative examples is the experience of the United States where the history of radon hazard prevention began in 1990. During this period, Standards and Protocols for measurements and measures on mitigation of the impact of this hazardous gas on the human health were developed and published.
The Department of Agriculture, the Department of Defense, the Department of Energy, the Department of Health and Human Services, the Department of Housing and Urban Development, the Department of the Interior, the Department of Veterans Affairs, the Environmental Protection Agency and General Services Administration took part in the development of the National Radon Action Plan. Thus, in 2010, an important document appeared in the United States — Strategy for Saving Lives.
The strategy was based on four approaches: testing and implementation of measures to reduce radon risks by means of professional services; provision of financial incentives and direct support in situations requiring implementation of measures for radon risk reduction; introduction of construction procedures using approaches aimed at radon risk prevention; raising of awareness (information and educational component).
Due to the implementation of these approaches, an effective system of countermeasures on prevention of excessive radon concentrations in buildings was introduced in the USA. The mechanism developed for the population is really simple and effective. There are five radon hotlines in the United States. There is a free access Map of the Radon Zones in the United States where the entire territory of the country is subdivided into zones according to radon concentration levels.
Moreover, to raise awareness in the United States, January is recognized to be the National Radon Action Month.
However, in 2020, the validity of the National Strategy expired and currently the country faces the need to adopt a new action plan. However, considering the vast experience in this field, there is no doubt that new action plan will be adopted.
In conclusion, but no less important
While reading this information you most likely may have a question: what about radon baths which are so popular in Ukraine? It has been generally accepted for a long time that radon is not radiotoxic due to the fact that it is not indigestible and is not accumulated in the body. Therefore, radon became popular in the framework of medical treatment. Radon baths are, in fact, a short-term exposure of a skin with possible but not proven positive effect.
The International Commission on Radiological Protection (ICRP) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) have concluded that optimistic position as for positive effects of low doses of radon is not substantiated. Observations are insufficiently reproducible and positive clinical effects can be explained by contributing factors and do not exclude carcinogenic effects. In addition, radon baths are not prescribed to everyone (for example, smoking is one of contraindications). And, of course, radon bath treatment periodis very limited.
What can we do?
First of all, to make sure that our house or the room where we spend most of the time is safe. Today it is popular to have your own dose monitoring equipment, to measure different sites, objects… and make videos for blogs, however, the standard dose monitoring device is not suitable for detecting dangerous radon levels. Much more complex devices which have quality certificates and undergo timely metrological verification are used to measure radon content. Radon content in the air is a subject to serious variations both daily and situational: even open door can significantly reduce its concentration. But temporarily.
High-quality radon radiometers are not cheap they cost up to hundred thousands of hryvnas and more. It is easier to order a measurement in a specialized laboratory.
Since last year, such radiation surveys are carried out by the experts of the State Scientific and Technical Center for Nuclear and Radiation Safety (SSTC NRS) who have corresponding equipment to make necessary on-site measurements. Based on measurement results, considering type and location of a premise, it is possible to determine measures that will help to reduce harmful radon effects. This can be achieved by selection of various design solutions which prevent radon penetration to a building from the soil or ventilation system (forced or natural) designed for permanent removal of radon from the indoor air.
And yet, there is something you can do right now and do it all the time: ventilate regularly your rooms. Systematic ventilation (provided that air inflows from the outdoors, not from the soil) will reduce radon concentration in the room for dozens of times. The lower radon concentration is, the lower is the risk of lung cancer, since radon threshold concentration below which radon does not pose a risk to the human health is currently unknown.
Uatom.org Editorial Board.