Radon and thoron exhalation rate, emanation factor and radioactivity risks of building materials of the Iberian Peninsula

Samuel Frutos-Puerto; Eduardo Pinilla-Gil; Eva Andrade; Mário Reis; María José Madruga; Conrado Miró Rodríguez

doi:10.7717/peerj.10331

Radon and thoron exhalation rate, emanation factor and radioactivity risks of building materials of the Iberian Peninsula

PeerJ. 2020 Nov 12:8:e10331. doi: 10.7717/peerj.10331. eCollection 2020.

Authors

Samuel Frutos-Puerto¹, Eduardo Pinilla-Gil¹, Eva Andrade^{2

3}, Mário Reis^{2

3}, María José Madruga^{2

3}, Conrado Miró Rodríguez^{3

4}

Affiliations

¹ Department of Analytical Chemistry, University of Extremadura, Badajoz, Spain.
² Laboratorio de Proteçao e Segurança Radiológica, Universidade de Lisboa, Lisboa, Portugal.
³ Centro de Ciencias e Tecnologias Nucleares, Bobadela, Portugal.
⁴ Department of Applied Physics, University of Extremadura, Cáceres, Spain.

Abstract

Radon (²²²Rn) and thoron (²²⁰Rn) are radioactive gases emanating from geological materials. Inhalation of these gases is closely related to an increase in the probability of lung cancer if the levels are high. The majority of studies focus on radon, and the thoron is normally ignored because of its short half-life (55.6 s). However, thoron decay products can also cause a significant increase in dose. In buildings with high radon levels, the main mechanism for entry of radon is pressure-driven flow of soil gas through cracks in the floor. Both radon and thoron can also be released from building materials to the indoor atmosphere. In this work, we study the radon and thoron exhalation and emanation properties of an extended variety of common building materials manufactured in the Iberian Peninsula (Portugal and Spain) but exported and used in all countries of the world. Radon and thoron emission from samples collected in the closed chamber was measured by an active method that uses a continuous radon/thoron monitor. The correlations between exhalation rates of these gases and their parent nuclide exhalation (radium/thorium) concentrations were examined. Finally, indoor radon and thoron and the annual effective dose were calculated from radon/thoron concentrations in the closed chamber. Zircon is the material with the highest concentration values of ²²⁶Ra and ²³²Th and the exhalation and emanation rates. Also in the case of zircon and some granites, the annual effective dose was higher than the annual exposure limit for the general public of 1 mSv y^-1, recommended by the European regulations.

Keywords: Annual effective dose; Building materials; Exhalation rate; Radon; Thoron.

Grants and funding

This work was supported by Junta de Extremadura, Spain (projects PRI IB16114), the Air Quality Surveillance Network of Extremadura (REPICA, project 1855999FD022) and European Union Funds for Regional Development (FEDER). Eva Andrade, Mário Reis, and Maria José Madruga from the “Centro de Ciências e Tecnologias Nucleares” (C2TN) of “Instituto Superior Técnico” (IST) were supported by the Foundation for Science and Technology (FCT) in Portugal through the ID/Multi/04349/2013 project. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.