Open Landfill as a Source of Public Health Risk Due to Accumulation of Toxic Metals (TMs) in the Top Soil

Background: Metal contamination caused by various anthropogenic sources, which affect the environment has become a global health concern. In many countries, including Nigeria, open landfills continue to be a prevalent method of waste disposal, despite increasing awareness of their environmental impacts. Through natural processes, heavy metals are leached from waste containing metal components, which increases the risks to public health. Objectives: This study aims to: (i) determine the level of heavy metal contamination in the topsoil of an open landfill site in Abeokuta, Ogun State, Nigeria; (ii) assess the potential health risks to adults and children associated with exposure to toxic metals. It is envisaged that the study will fill the information gap to develop a strategy to mitigate the negative impacts of the open landfill site in Abeokuta on the environment and health to achieve Sustainable Development Goals (SDGs) 3 and 15. Methods: For the study, 18 samples in duplicate were collected from the landfills. Exactly, 1g of the sample was digested using the aqua regia method while TMs were analysed using Atomic Absorption Spectrometer. Geo-accumulation index (I-geo) and Enrichment factor (EF) were employed to determine degree of pollution while health risk assessment was estimated using US EPA predictive model, and Pearson correlation for source apportionment. Results: The mean TMs concentrations were found to be 0.825 mg/kg for Cd, 23.6 mg/kg for Pb, 12.3 mg/kg for Cu, 2.14 mg/kg for Ni and 335 mg/kg for Zn, which were within the recommended soil values. The I˗geo index reveals moderate contamination from Cd – 0.27 mg/kg and Zn – 0.37 mg/kg while EF showed a moderate enrichment from Pb – 5.06 mg/kg and severe enrichment from Cd – 11.9 mg/kg and Zn – 15.1 mg/kg in the soil. The relationship between the TMs suggests an emergence from both natural and anthropogenic sources. Potential health risk assessment reveals that skin contact was the major pathway of exposure to TMs in the landfill, it also predicted a non-significant non-cancer risk and negligible cancer risk. Conclusion: The top soil in the open landfills at the time of the study are safe and pose no health risk.