Health risk assessment of heavy metals concentration from soil; a case study of the Mayo-Dallah in Southern area of Chad

The study evaluates the presence of heavy metals concentrations in the soil samples collected, which are important to minimise health risks resulting from exposure to such toxic substances. Ten samples collected in Yapala, located in Mayo-Dallah, Chad were analysed using Inductively Coupled Plasma-Mass Spectrometer (ICPMS). ICP-MS analysis revealed the presence of various toxic elements, Co (1-35 mg/kg), Cu (3-225 mg/kg), As (0.41-6.09 mg/kg), Se (0.04-0.44 mg/kg), Mo (0.15-15.50 mg/kg), Cd (0.004-1.896 mg/kg), Sn (0.29-8.89 mg/kg), Sb (below detectable limit-1.01 mg/kg), Hg (0.07-5.57 mg/kg), Pb (4-59 mg/kg), respectively. Elemental concentrations for Cu, Mo and Hg were higher than the maximum allowable limit in some of the analysed samples, while others were within the safe limit. The potential health risk showed the influence of the three exposure pathways were in the order of dermal contact > ingestion > inhalation. The Hazard Quotients (HQ) and Hazard index (HI) values for the heavy metal samples used were higher than 1 in dermal contact, which indicates that the individual may be subjected to potentially higher health risk. In accordance with the Food and Agriculture Organization (FAO)/World Health Organization (WHO) guidelines, our results show that some of the samples analysed possessed increase in the risk of exposure to heavy metals, and therefore the possibility of developing diseases by people inhabiting in this environment. As a result, regular monitoring of this area is needed, including further investigations to surrounding regions to provide a comprehensive assessment and decision.