Potentially Harmful Element toxicity in Geophagic clays consumed in parts of southeastern Nigeria

Abstract

An assessment of geophagic clays consumed by adults and children in Calabar and Okon-Eket areas of southeastern Nigeria was done in order to evaluate possible toxicity of Potentially Harmful Elements (PHEs)- Cd, As, Pb, Cu and Zn (CALCZ). Thirteen clay samples obtained from open markets and clay mines were air-dried, pulverized and analysed for their elemental constituents using Inductively Coupled Plasma Mass Spectrometry (ICPMS). Ecological and health risk assessments of the clays were conducted using Index of Geoaccumulation (Igeo), Contamination Factor (CF) and Degree (CDeg), Pollution Index (PI), Ecological Risk Factor (Er) and Index (RI), Hazard Index (HI) and Cancer Risk Index (CRI). The clays had PHE concentrations (ppm) in the order: Zn (13.0–148.0) > Pb (16.7–55.6) > Cu (5.7–23.0) > As (BDL-15.0) > Cd (BDL-0.2). Igeo values for Cd, As, Cu and Zn in the clays were <0, while Pb had a value of (-1) to 1. The clays from Calabar and Okon-Eket had Pb CF values of 1.8 and 1.7, and PI values of 1.4 and 1.3, respectively. Results of Igeo, CF and PI calculations revealed moderate Pb contamination in the clays. Low HQ and HI of the PHEs indicates that they pose no immediate risk of non-carcinogenic nor carcinogenic effects to the geophagic individuals. However, the moderate Pb contamination in the clays is a source of health concern, especially for geophagic children.

Keywords

• PHE
• Geophagic clay
• Pollution index
• Hazard index
• Pb contamination