The period of this research has been one of the most challenging of all my life. It's already started with a depression diagnosis, then lots of changes in my personal life that became big obstacles to face, like moving twice, working 60 hours per week, and dealing with isolation caused by the pandemic were some of those challenges, and with that, the acknowledgments turns an important part of this dissertation to thank everyone that helped me to achieve this goal.First, I would like to thank my tutor, Renato de Moraes, for all the patience and empathy with my situation and all the assist to make the article become a reality. I am really grateful for all the assistance you gave along all these years, which I believe wasn't easy since my learning process is slow. I would like to thank the other co-authors of the article, Frederico Meira Faleiros, Rafael Gonçalves da Motta, Francy Roxana do Valle and Leonardo Brenguere Leão Lopes for their contribution to the research. I also acknowledge the contribution of José Vinícius Martins and Sandra Andrade from NAP Geoanalítica for their assistance with LA-ICP-MS analysis. We also appreciated the aid from Kei Sato on the SHRIMP proceedings; without your help, many analytical problems would have happened.I express my gratitude to my parents, Sonia Maria Lopes and Anezio Julião, for all their support, especially after I decided to leave my job to take care of my mental health. And in that sense, I would also like to thank Ana Lidia Jacintho Delgado for being my company in both bright and dark times, you have entered my life in my worst moment and I can only thank you for staying by my side this whole time.I would like to thank the true friends who have welcomed me even after my breakdown.To my friends since high school and who are on my side until now, Caio Emmerick (and Thais Emmerick, which were not from school, but fits entirely in this group), Nathalie Zago, Renata Roitman, and Yorran Lee. To the Mocó Research Group, which is composed of Lucas Martins

Background:The use of natural radioactive building materials could be a health risk for both dwellers and mining workers. Therefore, a quick and effective method to test batches of rock samples is needed. Nevertheless, there is no reference value for maximum exhalation rates for building materials, except radiological hazard indices that do not measure gas exhalation rates directly. Objectives: This article investigated the correlations between Gamma Index and radon and thoron exhalation rates, and the proportions of radon and thoron in samples. Moreover, the main objectives were to analyze the feasibility of screening problematic samples for indoor use through a portable radiation detector (CoMo 170), which consists of a quick analysis at very low cost, and to simulate indoor concentration of radon using the measured exhalation rates of dimension stone slabs. Design: Best-selling dimension stone slabs were submitted to the following assays: gamma spectrometry, radon and thoron exhalation analysis using scintillation cell, and radioactivity measurement using a portable detector. Univariate and multivariate statistical analyses were conducted using Statistica 13 software. Results: The average activity concentrations measured were 971 ± 58.6 Bq/kg of 40 K, 184 ± 9 Bq/kg of 232 Th, and 74 ± 3 Bq/kg of 226 Ra. The maximum activity concentrations of 40 K, 232 Th, and 226 Ra series were 1,734 ± 100 Bq/kg, 2,667 ± 109 Bq/kg, and 596 ± 2 Bq/kg, respectively. The average exhalation rate of 222 Rn was 406 ± 20 Bq/h m 2 . Conclusions: The main recommendations arising from this study are as follows: a portable radiation detector (CoMo 170) could be used as a screening method for selected samples; Gamma Index limit value = 1 for dimension stone slabs could be adopted when assessing radon and thoron exhalation; and the surface radon exhalation rate should be measured as a basis of recommendation for surface treatment before sales. Finally, thoron exhalations should be considered in radiological assessment, as 57% of the samples had higher thoron exhalation rates than radon.

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