Heavy Metal Contamination and Associated Health Risks at the Halleluyah Dumpsite, Zuru, Kebbi State, Nigeria: Effects on Soil and Vegetables

Background and Objective: Soil is an important natural resource essential for agricultural productivity. However, contamination from dumpsites can introduce toxic elements into the soil and plants, necessitating periodic assessments. The objective of this study is to investigate the extent of heavy metal contamination in soil and edible vegetables grown around the Halleluyah Dumpsite in Zuru, Kebbi State, Nigeria, and to evaluate the potential health risks posed to the local population through consumption and environmental exposure. Materials and Methods: This study evaluated the concentrations of lead (Pb), nickel (Ni), cadmium (Cd), manganese (Mn), and copper (Cu) in soil and three commonly consumed vegetables, Solanum lycopersicum (tomato), Amaranthus viridis (amaranthus), and Lactuca sativa (lettuce), collected from the vicinity of the Halleluyah Dumpsite in Zuru, Kebbi State, Nigeria. Soil samples were taken at depths of 5, 10, and 15 cm, and both soil and plant samples were analyzed. The study also calculated the average daily inhalation (ADI), average daily dermal exposure (ADDE), target hazard quotient (THQ), and health risk index (HRI) for the heavy metals. Results: The Pb and Cd exceeded World Health Organization (WHO) permissible limits in all three vegetables. The Mn and Cu exceeded the safe limits only in S. lycopersicum, while Ni remained within acceptable levels. The THQ values for heavy metals in the vegetables were within safe limits, but their HRI values were above the threshold (≥1). In the soil, all heavy metals except Cd were within permissible limits. However, the ADI values for Cd, Mn, Ni, and Cu exceeded recommended safety thresholds, while Pb remained within limits. The ADDE values for heavy metals from soil exposure were within safe levels, but the THQ and HRI values exceeded the permissible threshold (≥1). Conclusion: Based on these findings, consuming vegetables grown in the affected soil and direct exposure to the contaminated soil may pose significant health risks. Therefore, remediation of the soil around the dumpsite, along with regular monitoring, is necessary to mitigate potential environmental and health hazards.