An assessment of natural radioactivity and health risk in Ofada rice (Oryza Sativa Japonica) and associated farmland soils near a major cement production zone in SW Nigeria

Abstract

Cement production releases naturally occurring radioactive materials, contaminating crops and soil and posing health risks. This study assessed radionuclide concentrations and health risks in Ofada rice and farm soils near a cement plant in Ibese, Nigeria. Sixty samples from Eggua, Igbogila, and Sawonjo were analyzed using gamma spectrometry. Mean activity concentrations of ⁴⁰K, ²²⁶Ra, and ²³²Th in rice were 12.5 ± 11.2, 26.7 ± 60.0, and 5.5 ± 2.8 Bq/kg (Eggua); 134.3 ± 66.7, 47.8 ± 24.3, and 2.0 ± 1.6 Bq/kg (Igbogila); and 78.0 ± 2.43, 11.2 ± 3.9, and 11.5 ± 2.5 Bq/kg (Sawonjo). Soil concentrations were 73.0 ± 45.1, 14.5 ± 10.8, and 5.6 ± 3.8 Bq/kg (Eggua); 73.0 ± 59.5, 9.6 ± 7.8, and 5.1 ± 1.9 Bq/kg (Igbogila); and 33.2 ± 27.9, 8.5 ± 12.5, and 5.9 ± 2.2 Bq/kg (Sawonjo). The highest effective dose in rice (510.8 ± 206 µSv/y) and cancer risks were in Igbogila, exceeding UNSCEAR limits. A slight relationship (r = 0.125) was observed between soil exposure and rice ingestion in Igbogila. Radionuclide levels in rice exceeded soil, indicating bioaccumulation. Results highlight health risks, necessitating monitoring, mitigation, and public awareness.