Radon exhalation rate and natural radioactivity in the building materials used in Metropolitan Jakarta and its surrounding, Indonesia

Eka Djatnika Nugraha ^1* Modibo Oumar Bobbo ¹ Wahyudi Wahyudi ¹ Radhia Pradana ^1,2 Rima Agustin Merdekawati ¹ Kartini Megagasri ¹ Abdussalam Topandi ³ Agus Nur Rachman ¹ Rusbani Kurniawan ¹ Evans Azka Fajrianshah ¹ Nurahmah Hidayati ¹ Ilma Dwi Winarni ¹ Ilsa Rosianna ^1,2 Leons Rixson ¹ Dikdik Sidik Purnama ¹ Heru Prasetio ¹ Shinji Tokonami ⁴

• ¹ National Research and Innovation Agency (BRIN), Bogor, Jakarta, Indonesia
• ² Graduate School of Science and Engineering, Hirosaki University, Hirosaki, Aomori, Japan
• ³ 5 Polymer Chemical Engineering, Polytechnic STMI of Jakarta, Jakarta 12000, Indonesia, Jakarta, Indonesia
• ⁴ Institute of Radiation Emergency Medicine, Hirosaki University, Hirosaki city, Japan

Building a safe living environment requires using healthy and sustainable building materials. Humans are exposed to natural radionuclides in building materials such as 226Ra, 232Th decay series, and 40K, which pose a radiological hazard. The present study aims to investigate the radionuclides content of building materials used in Jakarta and its surrounding area. The computer code RESRAD-BUILD was used to calculate the annual effective dose received by an adult individual living in a typical room built using the studied building materials. Various samples such as sand, cement, bricks, and Autoclaved Aerated Concrete (AAC) were collected. The 222Rn surface exhalation rate was determined using the closed chamber method using RAD7, while the concentration of natural radionuclide activity was measured using a gamma spectrometer. The 222Rn surface exhalation rate ranges from 4 × 10-2 to 1.6 × 100 mBq m-2 s-1 with an average of 4 × 10-1 mBq m-2 s-1. The average 222Rn exhalation rate of the building materials studied was much lower than the world average value of 1.6 × 101 mBq m-2 s-1. The average activity concentration values of 232Th (21 Bq kg-1) and 40K (217 Bq kg-1) in all building materials studied are lower than the world average values of 45 Bq kg-1 and 412 Bq kg-1. In comparison, the average value of the activity concentration of 226Ra (34 Bq kg-1) is close to the world average value of 32 Bq kg-1. Furthermore, the assessed radiological hazard from the measured building material has an average activity index of 0.3, while the RESRAD-BUILD estimated total annual effective dose for a typical house constructed using a mixture of the building materials was 0.11 mSv, in which indoor 222Rn alone represents 92% of the total. From the assessment results, the building materials in Jakarta and its surrounding area do not pose significant concerns from the perspective of radiological hazards. However, the higher contribution of 222Rn suggests the need to conduct a large-scale indoor 222Rn survey in the study area.