Risk assessment of polycyclic aromatic hydrocarbons in the sediments of the Ekulu River in Enugu State in Nigeria

Abstract

The human health and ecological risks resulting from exposure to polycyclic aromatic hydrocarbons (PAHs) in the Ekulu River sediments were estimated in this study. The Ekulu River receives pollutants potentially containing polycyclic aromatic hydrocarbons (PAHs) from runoff from automotive workshops and abandoned coal mines. The study found that mine drainage, in particular, could be responsible for the relatively high concentration of benzo[a]pyrene (1.266 mg kg⁻¹) in parts of river where sand is harvested on a commercial basis. Sources of the PAHs at The Gate and Damija were petrogenic. The consensus-based quality guideline for freshwater sediments using threshold effect concentration and probable effect concentration was the basis employed for evaluating the ecological risks, which were highest at The Gate, because of the presence of fluorene and phenanthrene. Toxicity equivalency (TEQ) at Damija and The Gate did not indicate health risks; however, those at Waterfall were high (1.39 mg kg⁻¹), indicating potential health risks. The hazard and risk indices indicate insignificant human health risks.

Keywords: ecological risks, exposure risk, hazard index, human health, hydrocarbons, toxicity equivalence