Potential risk effect from elevated levels of soil heavy metals on human health in the Niger delta

An analysis of the soil quality in the Niger Delta Area (NDA) was carried out to determine the severity of soil contamination. The United States Environmental Protection Agency (US EPA) risk assessment model was used in determining the potential health risk due to lifetime exposure (by means of ingestion, dermal contact and inhalation) of the population to heavy metal contents in the soil. Substantial levels of contamination were found indicating elevated levels of heavy metals above background concentrations from controlled samples in the areas. Median topsoil metal concentrations (0-15 cm) in the NDA measured in mg/kg were: Zn 58.3 +/- 37.0, Cd 1.3 +/- 1.0, Cr(VI) 13.2 +/- 5.5, Cu 28.3 +/- 31.5, Pb 895.1 +/- 423.9, Ni 42.7 +/- 20.3, Mn 201.8 +/- 77.5 and Fe 1303.5 +/- 2028.6. Pb, Ni, Zn, Cd, Cr(VI), Fe and Mn exceeded some guideline and standard values; while the comprehensive levels of total metals contamination exceeded the environmental action level for soils, which could potentially affect human health. The collective total risk (carcinogenic and non-carcinogenic) for minors and adults were established from the model using the slope factors and reference dose of the compounds respectively. The study has shown that soil contamination in the industrial and residential regions are similarly significant; while the risk assessment proved that based on the pollutants concentration in the soil, metals with the highest cancer risk values (Pb = 2.62E-02 and Cr(VI) = 1.52E-02) have the potential of affecting the health status of the residents, especially for children in the region. The chronic daily intake of the metals are of major concern as their cumulative effect could result to several health complications of children and adults in the region. (C) 2012 Elsevier Inc. All rights reserved.