Insights into Histopathological and Ecotoxicological Implications of Heavy Metal Contamination in Siganus rivulatus from the Red Sea, Egypt

        The contamination of heavy metals (HMLs) causes serious harm to aquatic species and can affect human health when consumed. This study determined a comprehensive evaluation of metal contamination in S. rivulatus, focusing on bioaccumulation behaviour, inter-metal relationships, and associated human health risks across different age groups. The Pearson correlation matrix revealed significant positive correlations among HMLs in fish organs, notably between Cr–Cd (r = 0.87) and Cr–Ba (r = 0.76).  Cluster analysis identified three distinct metal groupings based on levels of HMLs in fish: (1) Fe and Al, (2) essential elements (B, Cu, Zn), and (3) non-essential or toxic elements (e.g., Cr, Pb, Ba, As, Cd, Ni, Mn), with variable distributions indicative of cumulative environmental exposure. Tissue-specific clustering showed that liver and gills recorded the highest metal burdens, while muscle and intestine exhibited lower bioaccumulation levels. Bioaccumulation factor (Bio-AF) and biota-sediment factor (Bio-SF) analyses revealed that muscle tissues generally acted as de-concentrators, while gills and liver showed moderate to high bioaccumulation, particularly for Cu, Zn, B, and Ni. Target hazard quotient (THQ-HMLs) estimated daily intake (EDI-HMLs), and target cancer risk (TCR-HMLs) were conducted for children, young and adults consumers. All THQ-HMLs values across all age groups indicated no significant non-carcinogenic risk. However, TCR values for As, Cr, and Ni indicated potential carcinogenic risks in children. Histopathological examination revealed degradation of muscle fibres, intestinal villi shortening and fusion, liver cell vacuolation and congestion, and alterations in the gill epithelium In conclusion, the study underscores tissue-specific bioaccumulation patterns and identifies certain metals due to their bioaccumulative potential and associated health risks, particularly for vulnerable populations such as children. These findings emphasize the necessity of continuous environmental monitoring and implementating effective risk management strategies to ensure the safety of fish intake.