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.
Highlights
Humanity has always interacted with nature since ancient times; the surge of industrialization, urbanization and a laissez faire attitude towards environmental sustainability, have negatively impacted various matrices of the ecosystem
Human exposure to toxic heavy metals can result from accumulation up the food chain
There is potential risk to human and animal health from consumption of harvested farm produce like vegetables, tubers, fruits and nuts grown on polluted soils around dumpsite areas
Summary
Humanity has always interacted with nature since ancient times; the surge of industrialization, urbanization and a laissez faire attitude towards environmental sustainability, have negatively impacted various matrices of the ecosystem. Soil is a vital component of the biosphere as it provides the medium to support growth of plants, assists in the natural process of nutrient recycling and maintenance of ecosystem services and life support systems It protects the global ecosystem from environmental pollutants by acting as a buffer, storage, filter and transformation system (Sumithra et al, 2013). The level of contamination of soils in waste dumps is a function of the type of waste, soil topography, surface run-off and the scavenging activities (Ideriah et al, 2007) Due to their filtering and buffering ability, soils are capable of biodegrading basically all organic wastes, turning them to innocuous substances. Most developing countries in the world including Nigeria, have not been able to effectively manage their wastes posing a significant hazard to the environment. The present study examined the Concentration and Toxicological Risk Assessment of Heavy Metal Pollution in Dumpsite Soils within Benin City, Nigeria
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