Levels and Health Risks of Heavy Metals and Organochlorine Pesticide Residues in Soil and Drinking Water of Flood-Prone Residential Area of Lagos, Nigeria

Environmental pollution arises from the myriad of chemicals in current and historic applications. In Nigeria, the fate of pollutants among other factors relies on water runoffs with pollution implications on the flooded environment. In addition, there is a need for applications of pesticides against disease vectors in a flood-prone environment, therefore increasing pollution complications in the environment. Literature information is missing regarding the levels and public health risk implications of contaminants such as heavy metals and organochlorine pesticide (OCP) residues in groundwater and residential soils within the selected flood-prone residential locations in Lagos, Nigeria. This study was hence targeted at examining the levels and health risks of heavy metals and OCP residues in residential soils and groundwater sources of the targeted environment. Seven heavy metals comprising Cd, Zn, Fe, Pb, Cu, Ni, and Co were detected in the water samples with high concentrations of iron (mean = 22,000 mg/kg) and Zn (mean = 810 mg/kg). Only Fe (mean = 5.8 µg/L) and Zn (mean = 2.6 µg/L) were detected in the groundwater samples. Fifteen OCP residues were observed in the soil samples within the concentration range of 7.9 to 13 (mean = 11) mg/kg while seven OCP residues were reported in the groundwater samples within the concentration range of 0.19 to 0.35 (mean = 0.24) mg/kg. There was a concern about high contamination of dieldrin and heptachlor epoxide in the groundwater sources with concentrations exceeding the WHO (2017) drinking water guideline. A significant Pearson correlation (< 0.05) was obtained for endrin and endosulfan I in water and soil samples indicating potential contamination of groundwater from soil sources. The diagnostic ratio indicated possible applications of endosulfan and some other OCP residues. Overall, our data indicated low health risk implications for all the targeted contaminants. We recommend continuous investigation of newly listed priority chemicals such as dicofol and more public engagement on the implication of environmental pollution and health impacts of regulated chemicals.