Concentration and Toxicological Risk Assessment of Heavy Metal Pollution in Dumpsite Soils within Benin City, Nigeria

Abstract

Indiscriminate disposal of refuse and industrial effluents is a challenge in Nigeria. This poses a plethora of health and ecological risks from heavy metal contamination of soils. This study investigated the levels of heavy metal contamination in dumpsite soils and its effects on human health within Benin metropolis, Nigeria. The specific objectives were to determine the human and ecological risks via different exposure pathways. Soil samples were collected from three sampling stations, digested and analyzed for lead, cadmium, zinc, chromium, iron, nickel, manganese and copper using the Atomic Absorption Spectrophotometer (AAS). Pollution Indices and Human health risk were estimated using appropriate formulae. Results showed that that the mean concentrations of the investigated metals in the three stations were chromium (17.12±1.00, 17.65±1.05 and, 17.24±1.05 mg/kg), nickel (37.60±7.95, 40.98±1.46 and, 41.25±0.92 mg/kg), copper (48.57±4.91, 47.76±3.66 and, 48.05±3.46 mg/kg), lead (8.2±0.22, 8.17±0.52 and, 8.25±0.16 mg/kg), manganese (94.52±4.90, 94.98±6.69 and, 95.06±4.63), iron (467.98±36.69, 464.90±22.36 and, 462.15±10.64 mg/kg), cadmium (2.30±0.16, 2.22±0.11 and, 2.22±0.10 mg/kg) and zinc (142.93±3.93, 142.29±3.41 and, 142.87±3.86 mg/kg) respectively. Human health risk assessment revealed that the highest and lowest daily intake for the ingestion, inhalation and dermal pathway for both adults and children were Zinc and lead. Daily intake for children was higher than for adults via the three pathways with lifetime cancer risk (LCR) higher for children than adults. Carcinogenic and non-carcinogenic risk assessment shows that there were minimal risks from heavy metal contamination of the soils. Effective management and continuous monitoring of dumpsite soils is recommended to prevent negative impacts to man and the environment.