Radiological significance of marble used for construction of dwellings in Bangladesh

The natural gamma-radiation in samples of a variety of marbles imported into Bangladesh for use in building construction was measured, employing gamma-ray spectrometry with a HPGe detector. From the measured gamma-ray spectra, activity concentrations were determined for Ra-226 (29.31 +/- 2.06 to 46.99 +/- 2.97 Bq.kg(-1)), Th-232 (42.91 +/- 2.53 to 62.92 +/- 3.37 Bq.kg(-1)) and K-40 (824.42 +/- 15.42 to 1071.58 +/- 20.14 Bq.kg(-1)). The measured activity concentrations for these natural radionuclides were compared with the reported data of other countries and with the world average activity of soil. The radium equivalent activity (Ra-eq), the hazard indices, the gamma activity concentration index, the indoor absorbed dose rate and the corresponding annual effective dose were estimated for the potential radiological hazard of the marble. The Ra-eq, values of all marble samples are lower than the limit of 370 Bq.kg(-1), equivalent to a dose of 1.5 mSv.y(-1). The average values of the external and internal hazard indices are less than unity. The average indoor absorbed dose rate (121.25 nGy.h(-1)) is higher than the population-weighted average of 84 nGy.h(-1), whereas the corresponding annual dose limit falls within an average value of 0.60 mSv, which is an order of magnitude below the limit specified for building materials in the literature. The present results indicate that using marble in building construction in Bangladesh does not pose any significant radiological hazard.