ABSTRACT
Geophagy is the habitual and intentional consumption of clay material by animals and humans. Deliberate ingestion of edible clay (Geophagy) especially among women is a habit that has been recognized all over the world. This clay could have traces of metals which pose threats to the environment, human health and animals. In this study, nine (9) clay samples were systematically collected from Uzalla Town to investigate their mineralogical, geochemical, physical properties and the health implication on the consumers. The samples were collected from three (3) mining pit from top to bottom in profile. The different samples were designated as UZY (Yellowish brown clay), UZG (Grey clay), and the UZK (Kaolinite white clay). The samples were subjected to mineralogical, geochemical and physical analyses. The yellowish brown clay contains more of iron content due to oxidation of iron while the grey clay contains more of the carbonate content. Characterization of the clays was performed using X-ray fluorescence, X-ray diffraction and Geotechnical tests. The XRF shows the elemental composition of the clay, which shows high composition of SiO2 and Al2O3 indicating the clay is of an Aluminosilicate, while the XRD shows the mineral composition of the clay samples to be dominantly of: kaolinite, illite, smectite, albite, anatase. Other minerals include quartz, microcline, muscovite, and accessory minerals such hematite. Quartz was the major none clay constituent identified which poses a threat to human dental enamel. The Geotechnical test shows the clay is of high plasticity and the particle size distribution of the clay indicate the clay is a fine-grained with percentage fine fraction of 99%. Binary plots of TiO2 versus Al2O3 to distinguish between granitic and basaltic sourced clays indicates that the samples are from rhyolite/granite provenances. The high chemical index of alteration (CIA) 92.0% and chemical index of weathering (CIW) 95.0% of the clay samples is indicative of a relatively intense weathered source area. The pH values of these geophagical clays (4.76-5.2) reveals they are acidic to moderately acidic while the Trace metal in the clay samples were compared to Human Body Content (HBC), Adequate daily intake and WHO. Lead (Pb) in the samples range from 0.3 – 0.7mg/kg, Zn with a range of 25- 45mg/kg higher than the HBC of 33mg/kg, adequate intake of 15 mg/kg, The Ni with range of 1.4 – 1.8 mg/kg, higher than the daily intake of 0.002 – 0.1 mg/kg, Cu with range of 1.2-1.8 mg/kg, higher than the adequate daily intake of 1.0 – 1.5 mg/kg, As content with range of 0.1– 1.4 mg/kg higher than the WHO 0.002 – 0.1 mg/kg, adequate daily intake. Mn content has a range of 5.4 – 6.3 mg/kg, higher than the HBC, adequate intake and WHO. The Cd has a range of 0.1 – 1.9 mg/kg, higher than the HBC 0.002 – 0.1 mg/kg, adequate daily intake and WHO, Fe with range of 50 – 63 mg/kg higher than the HBC 0.002 – 0.1 mg/kg, adequate daily intake and WHO, while Co content with range of 0.1 – 0.5 mg/kg, while the body requirement for this element daily is 0.002 – 0.1 mg/kg. The amount of metals (Pb, Ni, Co, Fe, Zn, Cd, Cu, Mn, As) all exceeded the HBC, Adequate intake and WHO levels of recommendation, this indicate that these geophagic clay samples are not safe for human consumption, especially regarding lead as it’s accumulation in the human body may cause lead poisoning and is associated with damage of central nervous system. The consumers should be educated about the need to process the geophagic clay in a safe way to minimize the amount of contaminants such as toxic metals.
