From Environmental Burden to Structural Alterations: Integrating Chemical Analysis and Fluorescence Spectroscopy in European Chub (Squalius cephalus)

Freshwater fish are important bioindicators of environmental pollution and provide a pathway for human exposure to toxic elements. We aimed to determine the concentrations of 29 elements in the muscle tissue of European chub collected from the Pek River (impacted by mining activities and untreated wastewater), the Ibar River (affected by treated wastewater), and the Kruščica Reservoir (an unpolluted drinking water source). Elemental analysis was conducted using ICP-OES, and the results were compared to maximum allowed concentrations (MACs) for fish meat, alongside a human health risk assessment. No significant spatial differences were observed for most elements; elevated Pb levels were found in several individuals from Kruščica and Ibar, while isolated cases of increased Cd were recorded at all sites. Fluorescence spectroscopy was used to assess structural changes in muscle tissue, particularly in collagen. A red shift in collagen emission maxima was observed along the pollution gradient (Kruščica < Ibar < Pek), indicating structural modifications. These findings are consistent with the elevated metal burden detected in Pek. Overall, despite localized contamination, consumption of chub appears safe. The strong correlation between elemental composition and fluorescence responses demonstrated the potential of fluorescence spectroscopy as a rapid tool for detecting pollution-induced tissue alterations.