Assessment of heavy metals and natural radionuclides in locally produced soaps used in Benue State, Nigeria: implications for human health risk

Abstract

Human exposure to ionizing radiation and toxic metals remains a major concern for physicists, chemists, environmentalists, and the public. In this study, heavy metals (HMs: Ni, Pb, Co, Cr, and Cd) and natural radionuclides (NRs: ²³⁸U, ²³²Th, and ⁴⁰K) were analyzed in thirty locally produced soaps used in Benue State, Nigeria. The HMs were determined using Atomic Absorption Spectrophotometry (AAS), while NRs were measured using a NaI(Tl) detector. The concentration ranges of Ni, Pb, Co, Cr, and Cd were 0.100--0.400, 0.124--1.235, 0.003--0.034, 0.001--0.010, and 0.0037--0.115 ppm, respectively. These values were below the recommended safe limits set by the WHO and the U.S. FDA, indicating no immediate health risk except under prolonged exposure that could lead to HM accumulation. The results further showed that only three of the thirty surveyed soaps posed a severe radiological health concern because of elevated NR concentrations. The margin of safety, systemic exposure dose, and carcinogenic-risk estimates at 50% and 100% bio-accessibility indicated a higher health risk for children than for adults. Overall, the findings support safer production and use of locally produced soaps in Benue State and may encourage the growth of micro, small, and medium enterprises (MSMEs).