Natural radioactivity levels and radiological assessment of decorative building materials in Bangladesh

The use of building covering media, largely for decorative purposes, presents an associated need for accurate evaluation of naturally occurring radioactive materials, crucial in assessing radiological risk. Radiological risks, assessed through investigation of decorative material samples, have been provided through key quantities, including radium equivalent activity (Ra-eq), external and internal hazard indices, gamma index, indoor and outdoor absorbed dose rates, as well as the corresponding annual effective doses. The concentrations of Th-232 and K-40 in all of the studied samples are higher than the respective world averages whereas for Ra-226, only the clay tiles and a few other samples exceeded the world average value. The values for Ra-eq for all samples were found to be <370Bqk g(-1), recommended as the limiting dose below which safe use of bulk media can be assumed. For most samples, the internal and external hazard indices are well below the recommended limit of 1. The indoor absorbed dose rate has been observed to be higher than the population-weighted world average of 84nGy h(-1), and the corresponding annual effective doses fall below the maximum dose limit of 1mSv y(-1). The activity concentrations presented herein are expected to be useful in assessing the impact of future radiological loadings from use of decorative materials in dwellings.