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Gamma-ray spectrometric measurements were performed on sediment samples collected from surface-water dams in five southwestern states of Nigeria with the aim of estimating the background radiation levels and assessing the radiological hazards associated with the use of sediments in building construction. The weighted mean concentration of 40 K varied from 199.1 to 796.7 Bq kg− 1, whereas that of 238 U varied from 22.6 to 27.6 Bq kg− 1 and that of 232 Th varied from 36.4 to 76.1 Bq kg− 1 in the five states where samples were collected. The radiological hazards due to the natural radioactivity in samples were inferred from calculations of radium equivalent activities, internal and external indices, and effective dose rates in indoor air. The values obtained are lower than internationally recommended limits for building materials. The results indicate an acceptably low radiological risk arising from the use of the …