Natural Radioactivity and Hazard Assessment of Imported Ceramic Tiles in Nigeria

Abstract

The natural radionuclides (²²⁶Ra, ²³²Th and ⁴⁰K) content of ceramic wall and floor tiles commonly used in Nigeria have been determined by a gamma ray spectroscopy system using a high purity germanium detector. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 52 ± 2 to 105 ± 3, 56 ± 1 to 115 ± 2 and 185 ± 9 to 893 ± 17 Bq kg^-1 with mean values of 72 ± 14, 84 ± 18 and 629 ± 198 Bq kg^-1, respectively for the wall tiles. For the floor tiles, the activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K varied from 41 ± 2 to 131 ± 4, 59 ± 1 to 127 ± 2 and 351 ± 11 to 979 ± 16 Bq kg^-1 with mean values of 74 ± 31, 82 ± 24 and 618 ± 231 Bq kg^-1, respectively. The errors quoted in the means are standard deviations. The values of radium equivalent activity (Ra_eq) calculated varied from 194 to 328 Bq kg^-1 for the wall tiles, and 176 to 306 Bq kg^-1 for the floor tiles. The radium equivalent activities of all the samples examined were lower than the recommended limit of 370 Bq kg^-1 for building materials. The mean values of the external hazard index (H_ex), the activity index (I_γ) and the alpha index (I_α) of the wall and floor tiles are less than unity, which is a commonly accepted limit.

Key Words: Ceramic tiles, natural radionuclides, activity concentration, hazard assessment.