This study investigated the bioaccumulation of three toxic heavy metals—nickel (Ni), lead (Pb), and cadmium (Cd)—in the tissues of Callinectes sapidus (blue crab) from the Iko River, a heavily industrialised estuarine system in Eastern Obolo, Akwa Ibom State, Nigeria. A total of 12 adult crabs (six males and six females) were collected over a three-week period from two locations using crawfish nets and dissected to analyse metal concentrations in the hepatopancreas, gills, and muscle. Samples were digested with HNO₃/HClO₄ and analysed using Atomic Absorption Spectrophotometry (AAS), with method detection limits of 0.01 mg/kg for Ni, 0.005 mg/kg for Pb, and 0.002 mg/kg for Cd. Results revealed a hierarchical pattern of metal accumulation across tissues: hepatopancreas > gills > muscle. Female crabs exhibited significantly higher concentrations than males. At Station A, Ni concentrations in female hepatopancreas reached 312.59 ± 0.93 mg/kg, Pb 39.32 ± 0.33 mg/kg, and Cd 8.99 ± 0.07 mg/kg, all of which exceeded USEPA and FAO/WHO safety thresholds. Health risk analysis using Estimated Daily Intake (EDI) and Target Hazard Quotient (THQ) showed values far above safe limits, particularly in female tissues. THQ values ranged from 4.44–15.00 (Ni), 1.34–10.74 (Pb), and 0.12–8.70 (Cd), indicating a significant non-carcinogenic health risk to consumers. The findings demonstrate that C. sapidus from the Iko River is unsafe for human consumption due to chronic exposure to heavy metals, likely stemming from nearby oil-related activities and industrial discharge. Continuous environmental monitoring and regulatory enforcement are urgently recommended to protect ecosystem health and public safety.
Okpoji et al. (Thu,) studied this question.
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