Potentially toxic elements contamination in groundwater and human health risk assessment in the Mayo Bocki watershed, North Cameroon

The present study was carried out in the basement aquifers of the Mayo Bocki catchment area in Cameroon. The main objective was to assess the level of contamination of waters by potentially toxic elements and their risks to human health. To achieve this, assessment methods based on the calculation of pollution indices and human health risk indices were used. The results show that the order of abundance of the elements was: Zn > Mn > Fe > Al > Co > Ni > Mo > Cu > U > Pb > As > Cr > Cd in well water and Al > Zn > Fe > Mn > Ni > Cu > Cr > Co > As > Pb > U > Mo > Cd in borehole water. Concentrations above the values recommended by the WHO (2017) were recorded in 20% of cases for Al and in 5% of the waters studied for Fe, Pb, Co, Mn and Zn. The pollution indices calculated showed that the waters analyzed (96%) have a low degree of contamination by potentially toxic elements. Only 4% of the waters have a high level of pollution. The health risk assessment showed that about 60% of the well waters and 10% of the borehole waters have non-tolerable non-carcinogenic risks for the adult population. For children, table non-carcinogenic risk was recorded in 70% of the well waters and 80% of the bore waters. The calculation of carcinogenic risk indices revealed that almost all the groundwater studied (96%) is likely to cause carcinogenic diseases in adult and child populations following long-term oral and dermal exposure. The study concluded that the metallic quality of the water in the basin is of concern and therefore a project to monitor and treat contaminated water in the region should be implemented.