Bio-accumulation of Pb and Cd in the Soft tissues of Tympanotonous fuscatus, Sediment quality of the Upper Bonny Estuary Niger Delta and their Human Health Implications

Abstract

Environmental Pollution is a global problem especially as it affects the human health. Appreciable levels of heavy metals in the ecosystem exert deleterious effects on plants, animals and humans due to their high level of toxicity, persistence and bioconcentration and transfer along the food chain. So, studies to bio-monitor the levels of heavy metals in the environment and determine potentially hazardous levels for humans are necessary. In this study the concentration of Pb and Cd in the soft tissues of Typanotonous fuscatus and sediment quality of the upper Bonny Estuary, Niger Delta was carried out. Samples of Tympanotonous fuscatus were caught in 5 selected stations namely; Okochiri Creek (S1), Ekerekana Creek (S2), Okari-Ama Creek (S3), Ogoloma River (S4) and Bonny Estuary (Control). Concentrations of Pb and Cd in the soft tissues of Tympanotonous fuscatus and Sediment were analyzed following standard procedures using atomic absorption spectrophotometer (AAS) by GBC Avanta. The concentration of Pb and Cd in the soft tissues of Tympanotonous fuscatus ranged from 11.49 to 15.42mg/kg and 0.06 to 0.13mg/kg respectively, these values were not significantly different using turkeys multiple comparison at P<0.05 amongst the sampled stations. The concentrations of Pb were higher than the FAO permissible limit of 0.5mg/kg while Cd was below permissible limit. However, the Estimated Daily Intake (EDI) showed that Pb concentration ranged from 6.57mg/kg to 8.81mg/kg which is above FAO/WHO,(2010) Permissible Tolerable Daily Intake of 0.25mg/kg while estimated daily intake for Cd showed the range of 0.01 to 0.07mg/kg, which were within FAO / WHO, (2010) Permissible Tolerable Daily Intake of 0.07mg/kg. Sediment concentration range of 6.13 to 11.66 mg/kg and 0.01mg/kg to 0.07mg/kg were recorded for Pb and Cd respectively. These levels were below sediment quality guideline of 40mg/kg and 1mg/kg respectively (USEPA, 1999). The results above indicated that consumption of Tympanotonous fuscatusfrom the sampled areas of Upper Bonny Estuary would likely pose a potential health risk because of the high concentration of Pb which could bio-accumulate in the soft tissues and bones of the consumer, further more the sediment quality also revealed that Pb and Cd in sediment of the sampled stations were below permissible limit as specified by USEPA, SQG (1999) indicating them not to be up to pollution levels. This study emphasized that due to continuous exposure of the study area to industrial effluent discharges into the water bodies, over time, the accumulation of Pb and Cd in sediment and soft tissues of Tympanotous fuscatus could increase and become very detrimental for the coastal area. This will then constitute a health risk to the individuals in the area that consume these organisms and definitely become an issue of serious environmental concern.