Hazard Indices and Human Health Risks Associated with Toxic Element Contaminants in Bivalve Shellfish from Niger Delta, Nigeria

Abstract

The quality of coastal waters in Niger delta have increasingly and adversely impacted by varieties of contaminants occasioned by environmental degradation and aquatic perturbation posed by petroleum exploration activities. This tends to undermine nutritional and health benefits derived from consumption of shellfish harvested from these waters. This study investigated tissue burden, hazard indices and human health risks associated with toxic element contaminants in bivalve shellfish harvested from coastal waters of Niger delta. Four species of bivalve shellfish; bloody cockle (Anadara senilis), donax clam (Donax rugosus), knife clam (Tagelus adansonaii) and mangrove oyster (Crassosstra gasar) collected from four locations were assessed for levels of toxic element contaminants as well as hazard indices and human health risk associated with their consumption. The tissue burden of toxic element contaminants was determined using atomic absorption spectrometer while United State Environmental Protection Agency (US EPA) method was employed to estimate hazard indices and human health risk. Results indicated lead concentrations were within the 1.5mg/kg acceptable limits while levels of cadmium, arsenic and mercury were higher than FAO limits of 0.5, 0, 0.5 mg/kg respectively. The estimated human health risk indicated non-carcinogenic values and hazard indices higher than threshold value of one for cadmium, total arsenic and methyl mercury while values for inorganic arsenic at some locations were higher than stipulated one in one million (1.0x10^-6) chances. This implies that toxic elements apart from lead in bivalves shellfish from these locations can induce potential deleterious health effects at consumption of 48g/day of bivalve shellfish.