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===Excessiveness of Arsenic (As)===

===Excessiveness of Arsenic (As)===

'''Geochemistry of Arsenic:''' Arsenic is a metalloid and has high affinity for sulphide-bearing minerals. One of such minerals is pyrite, hence the formation of arsenopyrite (FeAsS). In the tropics, oxidative weathering leads to the formation Arsenite (As3+) and Arsenate (As4+) (Adeyinka et al, 2013).

'''Geochemistry of Arsenic:''' Arsenic is a metalloid and has high affinity for sulphide-bearing minerals. One of such minerals is pyrite, hence the formation of arsenopyrite (FeAsS). In the tropics, oxidative weathering leads to the formation Arsenite (As3+) and Arsenate (As4+).<ref name=Adeyinka>Adeyinka, O., N. M. Miranda, P. T. Raymond, Y. Abubakar, and C. A. Edafetano, 2013, Arsenic in Rocks of Kaltungo Area, Upper Benue Trough, Nigeria. Earth Resources, 1(1), 5-11.</ref>

'''Mechanism of Toxicity:''' Due to its affinity for sulphur, arsenic in biological systems, attacks sulphur-bearing enzymes by binding and blocking them. Soon, it makes its way through the digestive tract to the liver, spleen and lungs. Although most arsenic is excreted, some are still retained in the skin, hair, legs, nails and teeth (Finkelman et al, 2010a). As the concentration increases, adverse health effects result leading to carcinogenic or non-cancer problems. Prolonged exposure to arsenic induces peripheral arteriosclerosis, hair fall-out, retarded nail growth and various types of skin conditions such as hyperkeratosis, hyper- pigmentation and skin malignancies. These levels of disorders are prominent in places with arsenic concentrations of 100−1000μg/l in their groundwater as against 50μg/l stipulated by WHO in 1993 (Hutton, 1987). However, the presence of selenium reduces the toxic effects of arsenic.

'''Mechanism of Toxicity:''' Due to its affinity for sulphur, arsenic in biological systems, attacks sulphur-bearing enzymes by binding and blocking them. Soon, it makes its way through the digestive tract to the liver, spleen and lungs. Although most arsenic is excreted, some are still retained in the skin, hair, legs, nails and teeth (Finkelman et al, 2010a). As the concentration increases, adverse health effects result leading to carcinogenic or non-cancer problems. Prolonged exposure to arsenic induces peripheral arteriosclerosis, hair fall-out, retarded nail growth and various types of skin conditions such as hyperkeratosis, hyper- pigmentation and skin malignancies. These levels of disorders are prominent in places with arsenic concentrations of 100−1000μg/l in their groundwater as against 50μg/l stipulated by WHO in 1993 (Hutton, 1987). However, the presence of selenium reduces the toxic effects of arsenic.

In Nigeria, high concentrations of arsenic have been confirmed in the Northern Benue Trough in the Kaltungo area of Gombe State. Arsenic in this area emanates from coarse porphyritic granite, biotite granite, Bima Sandstone and basalt (Adeyinka et al, 2013). Arsenic was determined using Inductively Coupled Plasma Optical Emission Spectrophotometer (ICPOES), Optima 2000 DV, at the Petroleum Technology Development Fund (PTDF) Geochemistry Laboratory of Department of Geology and Mining, University of Jos. The arsenic concentrations tend to follow the same northeast- southwest trend as the Benue Trough. High concentration of arsenic in this area is attributed to the mid-Santonian magmatism in the Benue Trough (Adeyinka et al, 2013).

In Nigeria, high concentrations of arsenic have been confirmed in the Northern Benue Trough in the Kaltungo area of Gombe State. Arsenic in this area emanates from coarse porphyritic granite, biotite granite, Bima Sandstone and basalt.<ref name=Adeyinka /> Arsenic was determined using Inductively Coupled Plasma Optical Emission Spectrophotometer (ICPOES), Optima 2000 DV, at the Petroleum Technology Development Fund (PTDF) Geochemistry Laboratory of Department of Geology and Mining, University of Jos. The arsenic concentrations tend to follow the same northeast- southwest trend as the Benue Trough. High concentration of arsenic in this area is attributed to the mid-Santonian magmatism in the Benue Trough.<ref name=Adeyinka />

Arsenic, in this area, is released into the groundwater and surface water through dissolution, weathering and erosion of the host rocks. Being an anion, it sticks to mineral surfaces especially iron from biotite (Adeyinka et al, 2013). This explains the mobility of iron and arsenic during weathering and deposition in the area.

Arsenic, in this area, is released into the groundwater and surface water through dissolution, weathering and erosion of the host rocks. Being an anion, it sticks to mineral surfaces especially iron from biotite.<ref name=Adeyinka /> This explains the mobility of iron and arsenic during weathering and deposition in the area.

Results show that the concentration of arsenic in all the rock types at Kaltungo and the environs is far above the average crustal abundance of 2 ppm. Generally, the concentration ranges from 152.900 ppm to 235.200 ppm in the coarse porphyritic granite; it varies from 232.200 ppm to 243.100 ppm in the biotite granite. In the Bima Sandstone, the concentration ranges from 228.700 ppm to 87.540 ppm while in the basalts of the area, the range is from 174.600 ppm to 151.600 ppm (Adeyinka et al, 2013).

Results show that the concentration of arsenic in all the rock types at Kaltungo and the environs is far above the average crustal abundance of 2 ppm. Generally, the concentration ranges from 152.900 ppm to 235.200 ppm in the coarse porphyritic granite; it varies from 232.200 ppm to 243.100 ppm in the biotite granite. In the Bima Sandstone, the concentration ranges from 228.700 ppm to 87.540 ppm while in the basalts of the area, the range is from 174.600 ppm to 151.600 ppm.<ref name=Adeyinka />

====Health impacts of excessive arsenic in groundwater in Zimbabwe====

====Health impacts of excessive arsenic in groundwater in Zimbabwe====

====Dangers of Geophagy====

====Dangers of Geophagy====

Despite the various benefits of geophagy, it can be detrimental to human health. The cation exchange capacity and the adsorption potential of clay and shale can lead to the deficiency of certain elements in the body. For instance, in Turkey, iron-deficiency anemia has been linked to the consumption of clays especially sepiolite and montmorillonite of high capillary electrochromatography (Abrahams, 2013). This is caused by the effectiveness of clays to adsorb iron. In addition, the consumption of clay has been confirmed to cause potassium deficiency–a condition known as hypokalemia. It is reflected by low concentration of potassium in the blood. In a situation whereby there is concurrent deficiency of iron and potassium, a disease known as cachexia Africana results. This can, however, be treated by iron and potassium supplementation programmes.

Despite the various benefits of geophagy, it can be detrimental to human health. The cation exchange capacity and the adsorption potential of clay and shale can lead to the deficiency of certain elements in the body. For instance, in Turkey, iron-deficiency anemia has been linked to the consumption of clays especially sepiolite and montmorillonite of high capillary electrochromatography.<ref name=Abraham>Abraham, P. W., 2013, Geophagy and the Involuntary Ingestion of Soil. In: O. Selinus, Essentials of Medical Geology: Springer Netherlands, pp. 433-454.</ref> This is caused by the effectiveness of clays to adsorb iron. In addition, the consumption of clay has been confirmed to cause potassium deficiency–a condition known as hypokalemia. It is reflected by low concentration of potassium in the blood. In a situation whereby there is concurrent deficiency of iron and potassium, a disease known as cachexia Africana results. This can, however, be treated by iron and potassium supplementation programmes.

In Turkey, the consumption of soil by women and children has been noted to cause the combined deficiency of iron and zinc (Abrahams, 2013). According to a research conducted, deficiency of zinc leads to growth retardation and delayed puberty. Thus, for persons that have low concentration of zinc in the blood, geophagy helps to further lower the level of zinc in the blood. However, zinc supplementation programmes have been supremely effective in improving growth and normal puberty maturation in this region.

In Turkey, the consumption of soil by women and children has been noted to cause the combined deficiency of iron and zinc.<ref name=Abraham /> According to a research conducted, deficiency of zinc leads to growth retardation and delayed puberty. Thus, for persons that have low concentration of zinc in the blood, geophagy helps to further lower the level of zinc in the blood. However, zinc supplementation programmes have been supremely effective in improving growth and normal puberty maturation in this region.

In an environment where the soil is contaminated with lead, geophagy could expose little children to lead poisoning. This could lead to damage to the developing brain and nervous system. Lead is particularly dangerous to young children as research has shown that there is no safe level for lead in children.

In an environment where the soil is contaminated with lead, geophagy could expose little children to lead poisoning. This could lead to damage to the developing brain and nervous system. Lead is particularly dangerous to young children as research has shown that there is no safe level for lead in children.

==References==

==References==

* Bunnell, J.E., Finkelman, R.B., Centeno, J.A. and Selinus, O., 2007. Medical Geology: a globally emerging discipline. Geologica Acta, 5(3), 273-281.

* Bunnell, J.E., Finkelman, R.B., Centeno, J.A. and Selinus, O., 2007. Medical Geology: a globally emerging discipline. Geologica Acta, 5(3), 273-281.

* Christine, L.E., Sujuan, G., Yiming, L., Chaoke, L., Rongdi, J., Kathleen, S.H., Jingxiang, C., Feng, M., Yunpeng, W., Po, Y., Shuzhuang, S., Frederick, W.U., Charles, W.S. and Hugh, C.H., 2000. Trace Element Levels in Drinking Water and Cognitive Function among Elderly Chinese. American Journal of Epidemiology, 151(9), 913-920.

* Christine, L.E., Sujuan, G., Yiming, L., Chaoke, L., Rongdi, J., Kathleen, S.H., Jingxiang, C., Feng, M., Yunpeng, W., Po, Y., Shuzhuang, S., Frederick, W.U., Charles, W.S. and Hugh, C.H., 2000. Trace Element Levels in Drinking Water and Cognitive Function among Elderly Chinese. American Journal of Epidemiology, 151(9), 913-920.