Assessment of Human Health Risk from Heavy Metal Loads in Freshwater Clam, Ergeria radiata, from the Nun River, Niger Delta, Nigeria

Abstract

The Nun River where the present study took place is one of the two arms of River Niger system traversing Bayelsa State, Nigeria before emptying into the Atlantic Ocean. It is home to a number of commercial fish and shellfish species, some of which are endemic, including the highly relished freshwater clam (Ergeria radiata) in the Niger Delta region of Nigeria. The Nun River is subjected to a myriad of human induced contaminations from oil and gas activities, agricultural runoffs, sewage disposal and recently illegal oil refining activities. Six stations were selected along the upper reaches of the Nun River across six communities spanning over 50 km. Water, sediment and E. radiata samples were collected during the months of August, October, December and January at the established stations.  Trace metal (Pb, Cr, Cu, Ni, Cd and Zn) levels, bioaccumulation and bioavailability potentials of the metals in the clam were evaluated. The heavy metal levels were in the order of magnitude Ergeria>Sediment>overlying water across all the stations during all the months. Trace metal levels were moderately elevated with Ni recording the highest percentage elevation in the clam. Health implications of consuming seafood with elevated levels of trace metals was assessed and regular assessment of contaminant levels in the Nun River is advocated to avoid severe ecologic and human health impacts.

Keywords: Trace metals, bioaccumulation, Nun River, Human Health