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

The ²²²Rn surface exhalation rate varies 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 global 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 global average values of 45 and 412 Bq kg^-1. In comparison, the average activity concentration of ²²⁶Ra (34 Bq kg^-1) is similar to the global 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 areas do not pose significant concerns regarding radiological hazards. However, the higher contribution of ²²²Rn suggests the need for a large-scale indoor ²²²Rn survey in the study area.