In Vitro Bioaccessibility of Lead in Artisanal Mining Contaminated Soils and Sediments from the Anka Area, NW Nigeria

Abstract

The gastric bioaccessibility of Pb was investigated in soils and sediments from five villages in the Anka area of north-western Nigeria which has been adversely affected by artisanal mining of gold from lead-rich ores. In vitro bioaccessibility experiments were used to determine the extractability of Pb in order to evaluate the human health risk, especially to children below the age of five. The concentration of Pb in the simulated gastric fluids ranges from ~ 198 to 41740 µg, with corresponding human bioaccessible fraction between ~ 29 and 100% (mean, ~ 60%). Chemical daily intake (CDI, µg/Kg/Day) values of between 111 and 41587 are generally very high compared to the tolerable daily intake (TDI) of ~ 3.6 µg Pb/Kg/Day. The high bioaccessibility is a result of high total concentration of Pb and the presence of highly soluble carbonate and oxide minerals in the ores. These results point to the very adverse health effects likely to result from incidental hand-to-mouth ingestion of soils by children in the affected villages. The results further show that the low pH of gastric juices enhances the extraction of Pb. Given the likelihood of sub-nutrition in the affected communities, characterized by skipping of meals, which can result in lowering of the pH over extended periods, the risk of Pb poisoning is further increased. This study was based on a hand-to-mouth ingestion scenario alone, but as other exposure routes, such as eating improperly washed vegetables and inhalation of dust are possible, the risk might even be higher. This, along with the fate of extracted Pb in the intestinal environment may need to be evaluated in order to fully quantify the bioavailability of Pb in the area.

Assessment of radiological risk from the soils of artisanal mining areas of Anka, North West Nigeria

“…The geology of Anka is characterized by the Anka schist belt that hosts the lead mineralization, and the lead-copper-silver-gold polymetallic association. Anka is well known for artisanal gold exploitation for several decades and the mineral is hosted by schists, phyllites and quartzites associated with sub-regional structural elements subsidiary to the Anka fault (Waziri et al, 2013).…”

Environmental Geochemical Investigation of the Geogenic Pollution Potential of Bida Formation, Northern Bida Basin Nigeria

“…It, therefore, shows that even if the total concentration of each of the elements is passed onto the residual soils as discrete grains through physical weathering, they are unlikely to pose serious geogenic environmental pollution problems. Although most existing environmental risk assessment indices use the total concentration of contaminant elements, a knowledge of the easily solubilized or biogeoaccessible fraction is key to understanding the scale of the problem (Adamu and Olaleye, 2022;Waziri, 2013;Ullrich et al, 1999). Because the metals are not soluble and they partition strongly to the solid phase, they will not be readily available for uptake by plant roots, or will not be directly toxic to soil biota.…”

Assessment of heavy metals contamination and pollution around mining sites of Anka, north-west Nigeria

“…Anka, like some other similar geological belts in Nigeria, has been the focus of artisanal gold exploitation for several decades. Gold found in Anka is hosted by schists, phyllites and quartzites associated with sub-regional structural elements subsidiary to the Anka fault (Waziri and Andrews, 2013).…”