Available online at ScienceDirect. Procedia Engineering 172 (2017 )

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1 Available online at ScienceDirect Procedia Engineering 172 (2017 ) Modern Building Materials, Structures and Techniques, MBMST 2016 Radon - occurrence and health risks in civil engineering Andrzej Ubysz a, *, Marek Maj b, Michał Musiał c, Jakub Ubysz d a Professor, Wroclaw University of Technology, Faculty Of Civil Engineering Wroclaw Pl. Grunwaldzki 11, Poland b Assistant Professor, Wroclaw University of Technology, Faculty Of Civil Engineering Wroclaw Pl. Grunwaldzki 11, Poland c Assistant Professor, Wroclaw University of Technology, Faculty Of Civil Engineering Wroclaw Pl. Grunwaldzki 11, Poland d Student's Science Society, Wroclaw Medical University, Faculty Of Medicine, Wroclaw, ul. Marcinkowskiego 2-6, Poland Abstract The paper presents risks of the use of building materials with radioactive properties. The element that generates almost half of the natural radiation is radon. The most common medical complications are radiation sickness and cancer, affecting the lungs. The workplaces where building materials are manufactured with the use of radioactive materials present a hazard to human health, e.g. in deep and opencast mining. The report states that radon after smoking is the second leading cause of lung cancer. Protection against excessive radiation from radon ought to be bases on the use of materials with a relatively low level of radioactivity Published The Authors. by Elsevier Published Ltd. This by Elsevier is an open Ltd. access article under the CC BY-NC-ND license ( Peer-review under responsibility of the organizing committee of MBMST Peer-review under responsibility of the organizing committee of MBMST 2016 Keywords: radon, concrete, radioactive, health risks, civil engineering. *. Corresponding author. Tel.: ;. address: marek.maj@pwr.edu.pl Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of the organizing committee of MBMST 2016 doi: /j.proeng

2 Andrzej Ubysz et al. / Procedia Engineering 172 ( 2017 ) Introduction Civil engineers often focus their attention on the ultimate limit states of the bearing capacity and the use of the structure. However, they forgetting that buildings are primarily intended to serve people. The paper presents risks of the use of building materials with radioactive properties. The element that generates almost half of the natural radiation is radon. Below, there are some examples of radioactive effects of concrete, which may be neglected in the process of design and construction. However, their impact on people s health and even life is significant. Natural radioactivity (ionizing radiation) comes from natural radioactive elements present in soil, rocks, air and water. Examples of such natural sources include: cosmic rays penetrating the lower layers of the atmosphere; minerals, mostly rocks and derivatives thereof; secondarily, animated nature: plants and animals; radiation resulting from human activity (mining of radioactive elements (uranium), the processes of burning fossil fuels containing radioactive elements). This king of radiation is both the natural environment: air, water reservoirs, food, and from human activities: production plants emitting harmful substances, concrete engineering structures. What is natural radioactivity? Henri Becquerel, the discoverer of the phenomenon, observed the effect of blackening of the photographic plate by putting some uranium salt on it. The result of this observation was published in Two years later, Maria Sklodowska-Curie named this phenomenon radioactivity. These studies were considered groundbreaking, and both scientists were awarded the Nobel Prize in Becquerel (Bq) has become the unit of radioactivity. Radioactivity is the transformation of the atomic nucleus, which is accompanied by the emission of radiation. Natural radioactivity is the spontaneous emission of, and radiation by naturally occurring unstable isotopes of elements. Alpha radiation is a reaction of radioactive decay in which helium nucleus u (the alpha particle) is emitted. A stream of such particles emitted by decaying nuclei is called radiation. Nuclei resulting from the breakdown have an atomic number reduced by 2, and a mass number reduced by 4. This is illustrated by the process of disintegration of the atoms of uranium, thorium and radium. (1) (2) (3) Decay product of the last reaction is radon. This element as well as some other radioactive elements are present in rocks, fossil fuels and water. However, in contrast to the radioactive elements of higher number of mass, it is marked by a short half-life (Figure 1) and by considerable ionizing capacity resulting from high-energy and high-mass particles. The measurement of the concentration of radon is performed most commonly using a scintillator. Description of the test method are shown i.a. in [1]. In the next part it is shown where the problem of the occurrence of radon can be found in the civil engineering in what circumstances it can pose a risk to health and to human life. 2. Radon as a health risk in civil engineering Contact with radon is in most cases not harmful to human health and life. There are situations, however, in which engineers should be aware of such risks. It is assumed that the concentration of radon in the air is 10 Bq/m3, which is about half the dose of radiation which people are exposed to from natural sources. However, in buildings made in large part from concrete, cement and their derivatives, much higher natural radiation of these materials is present.

3 1186 Andrzej Ubysz et al. / Procedia Engineering 172 ( 2017 ) Mass number atomic number Fig. 1. Decay chain illustrating half-life of radioactive elements isotopes [2]. Fig. 2. Model of the radon atom (atomic number 86). The density of radon is of 9.73 kg / m 3, thus it is about eight times as heavy as air. Accordingly, radon concentration in the lower parts of the premises, and in particular on the lower levels often greatly exceeds its mean concentration in the air. Additional effect of radiation from the subsoil is observed from the basement, especially where the substratum is made of granite containing large amounts of uranium. The phenomenon can be observed in Poland, for instance, in the region of the Izerskie Mountains. Most European countries have introduced limiting of the allowable concentration of radon in the buildings in which people stay for an extended period of time. This is

4 Andrzej Ubysz et al. / Procedia Engineering 172 ( 2017 ) both due to the short half-life of the element and simultaneous formation of subsequent of radioactive elements (Figure 1) emitting alpha radiation. Fig. 3. Concentrations of radon observed near uranium mines [4]. Fig. 4. High levels of stone dust pollution in a rock aggregate production plant.

5 1188 Andrzej Ubysz et al. / Procedia Engineering 172 ( 2017 ) Measurements show that a man remaining in a closed or isolated and poorly ventilated room for 16 hours a day receives a dose of 3 msv (milisievert is the unit that specifies the amount of radiation received by a living organism). This dose is similar to the dose of natural radiation a person receives in 1 year. Comparing to the medical imaging: during an X-ray of the limb a person receives a dose of around 0.01 msv, during X-ray of the chest receives a dose of around 0.1 msv and computer tomography of the brain 2 msv. The above-mentioned exposure thus corresponds to having lung X-rays every few days. Fig. 5. Modern concrete mixing plant with the dedusting devices. Fig. 6. Protective casing gutters reducing rock dust emissions. The most common medical complications are radiation sickness and cancer diseases, affecting mainly the lungs. The workplaces where building materials are manufactured with the use of radioactive materials present a hazard to human health, e.g. in deep and opencast mining. Some authors consider uranium mines as reference points, where

6 Andrzej Ubysz et al. / Procedia Engineering 172 ( 2017 ) radon concentration can reach as much as Bq / m3 (Figure 3). In building materials mines, (e.g. quarries) concentration of radon is more than ten times as low. Besides radiation, inhalation of radioactive dust is particularly harmful to human health, as it increases the effect of radiation inside the body. Granite quarries (Figure 4) are particularly harmful in this respect. The same applies to producers of granite slabs; however, here the negative effects are mitigated by the so-called wet production technologies. Similar observations are also true for concrete-mixing plant. Additionally, manufacturing technologies have an impact upon radon emissions. In addition to reducing the level of pollution, for instance with the use of protective casing gutters (Fig. 6), technologies associated with combustion should also be limited. These are also a major source of radioactive radon. It is assumed that the radon can be harmful in doses above 100 msv. These doses can receive the human body, for example during long-term accomodation in poorly ventilated basement or when working in deep mines and open-pit mines, and quarries and stone processing plants. High radiation may also be present in some buildings made of concrete elements. It was observed that the most common medical complications of radiation is radiation sickness and cancer that affects primarily the lungs. The harmfulness of radon to the human body consists in disturbing the chemical structure of DNA; namely, high-energy, short-lived decay products of radon are responsible for the disturbance. Organisms have a natural ability to correct damages of the DNA molecules that encode its genome. Higher doses of radiation can cause the disruption of the repair process, and damage of the large amount of DNA. This eventually can lead to uncontrolled cell division and the formation of cancer. 3. Conclusions According to [3] environmental data confirm a close relationship between lung cancer and large concentrations of radon. The report states that radon is the second leading cause of lung cancer after smoking. Protection against excessive radon radiation ought to be bases on the use of materials with a relatively low level of radioactivity (e.g. slag, ash, granite aggregate, other materials derived from combustion). The rooms should be thoroughly ventilated on a regular basis. The most beneficial would be a continuous exchange of indoor air with atmospheric air. During the process of designing or adapting premises, basements must not be used for residential purposes. Production technologies should take into account possible rise in the level of radon emission into the atmosphere as a result of combustion or high levels of dustiness. In the first case, protection filters can be installed at the outlet of smoke installation. In the second case, shields and filters should separate automatic production halls from the rooms where employees are present. On the other hand, radon has also got a positive effect. Studies of the phenomenon of radiation hormesis have shown that low doses of ionizing radiation (within the region of and just above natural background levels) are beneficial, stimulating the activation of repair mechanisms that protect against disease such as cancer and certain genetic disorders. In addition, radon positively stimulates some biological processes in nature. References [1] D. Mazur, M. Janik, J. Loskiewicz, P. Olko, J. Swakoń, Measurements of Radon Concentartion in Soil Gas by CR-39 detectors, Radiation Measurements 31,1999. [2] Figure shared by P.Drozdzewski from the collection of copyright lectures Nuclear Chemistry. [3] Raport EPA's Assessment of Risks from Radon in Homes ( Estimation of risks posed by radon in homes. Made by the EPA ), 2003 prepared by Environmental Protection Agency in USA. [4] Impact of new environmental and safety regulations on uranium exploration, mining, milling and management of its waste (Proceedings of a TCM held in Vienna, September 1998), [5] Académie des Sciences Académie Nationale de Médecine: Dose-effect relationships and estimation of the carcinogenic effects of low doses of ionizing radiation, March 30, 2005.