NATURAL RADIOACTIVITY AND CANCER RISK ASSESSMENT OF BUILDING MATERIALS IN NORTHERN DELTA STATE, NIGERIA

Abstract Naturally occurring radionuclides in building materials represent potential long-term health hazards, although full excess lifetime cancer risk (ELCR) assessments remain restricted in Nigeria. This study examined the activity concentrations of 40K, 238U, and 232Th in 72 building material samples (cement, sand, granite, tiles, paint, wood, etc.) obtained from northern Delta State, Nigeria, using a NaI(Tl) gamma-ray spectrometer. Radiological hazard parameters such as radium equivalent activity (Raeq), external and internal hazard indices (Hex, Hin), gamma index (Iγ), alpha index (Iα), annual effective dose (AED), and ELCR were determined. The results showed that the mean activity concentrations were 94.00 ± 15.52 Bq/kg for 40K, 11.57 ± 2.32 Bq/kg for 238U, and 9.05 ± 1.43 Bq/kg for 232Th which are all below global averages. All conventional hazard indices calculated were observed to be within global safety limits, with a mean AED of 0.0903 ± 0.0130 mSv/y which is 9% of the 1 mSv/y public limit. However, 94.4% of samples above the ELCR criterion of 0.29 × 10-3, with a mean ELCR of 0.316 × 10-3. The largest dangers were connected with POP paint and glossy tiles. Although all materials comply with annual dosage limitations, the high fraction surpassing the ELCR threshold implies significant potential lifelong cancer risk. Thus, regulatory frameworks should consequently incorporate ELCR alongside annual dose limitations for building material safety in Nigeria. Keywords: Natural Radioactivity, Building Materials, Excess Lifetime Cancer Risk, Radiological Hazards