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Abstract
Heavy metal contamination threatens coastal ecosystems and seafood safety, especially near industrial areas. This study measured lead (Pb), zinc (Zn), and cadmium (Cd) concentrations in the liver, gills, and muscles of chub mackerel (Scomber japonicus) from an industrial site near the Zawia oil refinery and a reference site at Dila on the Libyan coast. Three fish per site were collected in each of the four months (June, August, October, and December 2024). Tissues were oven-dried, digested by microwave-assisted acid digestion, and analyzed by inductively coupled plasma mass spectrometry (ICPMS), and concentrations are reported in mg/kg dry weight. Based on mean concentrations across the four months. Zn and Cd followed the order liver > gills > muscle at both sites, while, Pb was highest in the gills and lowest in the muscle. Most metal tissue combinations peaked in August and were lowest in December. Zn levels in all tissues, Pb levels in the gills and muscle, and Cd levels in the liver were higher at the refinery site in every month, whereas Pb levels in the liver and Cd levels in the gills and muscle showed no consistent difference between sites. Mean liver Cd was nearly twice as high at the refinery as at Dila (1.23 vs 0.65 mg/kg). Muscle, the edible tissue, had the lowest concentrations. Muscle Cd (maximum 0.070 mg (which is roughly the daily recommended amount)/kg) was below the EU limit for mackerel (0.10 mg/kg wet weight) in all samples, and muscle Pb exceeded the EU limit (0.30 mg/kg wet weight) only in one refinery sample from October, and only before conversion from dry to wet weight. These results suggest that industrial activity near the refinery contributes to metal accumulation in fish that EU support continued monitoring of industrial discharge.