Seasonal Assessment of Pollution Status, Bioaccumulation and Potential Human Health Risk of Heavy Metals in Shrimps (Penaeus monodon) and Water from the Great Kwa River in Calabar, Nigeria

Abstract

The deterioration of water quality in rivers is caused by various factors, with heavy metals contamination being a significant
contributor. Human activities are identified as the main cause of this contamination. This research evaluated the pollution levels,
bioaccumulation, and potential health risks associated with heavy metals presence in Shrimps (Penaeus monodon) and the water
from Great Kwa River in Calabar, Nigeria. Shrimp and water samples were collected for both wet and dry season at four
designated locations along the river. The physical characteristics of the water were assessed in-situ. The concentrations of heavy
metals, namely lead, cadmium, chromium, cobalt, iron, and copper were determined through wet digestion and analyzed using
an Atomic Absorption Spectrophotometer. To validate the method, standard reference materials (Lichens coded IAEA - 336)
were utilized. The physical properties of water were found to be within the established standards. In the shrimp, the Fe and Pb
were significantly higher (p < 0.05) during the wet season compared to the dry season. Similarly, the occurrence of Fe, Cr, and
Pb in the water samples was significantly higher (p < 0.05) during the wet season compared to the dry season. The Estimated
Daily Intake of all the assessed metals in both seasons were within the recommended upper tolerable limits for heavy metals in
seafoods. The Target Hazard Quotients for metals under investigation were also within safe limits for both seasons. The Hazard
Indices of these metals in both seasons were less than one (<1), indicating minimal or no significant health risks. The individual
Incremental Lifetime Cancer Risks for Chromium, Cadmium, and Lead ranged from 10-7
to 10-4
, which are considered acceptable.
Therefore, the consumption of shrimps from Great Kwa River is unlikely to pose a significant carcinogenic risk associated with
the examined metals.