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

Sunday Ukwo,Chidi Ezeama,Kuyik Abasiekong

doi:10.36547/ae.2020.2.4.61-68

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.

Highlights

Food contamination by chemical contaminants have continued to be a subject of serious concern to researchers globally due to their harmful effects on human body
The concentrations and levels of accumulation of toxic elements by bivalve samples in this study clearly revealed that bivalve shellfish are differentially selective for a range of toxic element and these variations might be influenced by a number of intrinsic and extrinsic factors
The present study confirms the occurrence and variability in the levels of toxic elements contaminants in the bivalve shellfish consumed by the coastal populations of the Niger Delta, Nigeria

Summary

Introduction

Food contamination by chemical contaminants have continued to be a subject of serious concern to researchers globally due to their harmful effects on human body. Increased coastal population, rapid urbanization, oil and gas production, artisanal petroleum refining, oil spillage, tourism development, heavy rainfall throughout, and other economic activities have created numerous environmental and ecological problems in the Niger delta coastal areas (Ukwo et al, 2019). Marine bivalve shellfish such as clams, mangrove oyster, cockles and other benthic filter feeders organisms are found on the mangrove mudflats, intertidal sandy beaches and the estuarine waters of the Niger delta. Most species of bivalve shellfish consumed in Nigeria are harvested from the brackish water that is exposed to varying amounts of chemical and environmental contaminants such as industrial chemicals, toxic residues from various anthropogenic

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