Bioaccumulation and health risk assessment of heavy metals in freshwater fish from the river Hron (Slovakia): a case study revisited after 17 years

The Hron River is a freshwater ecosystem affected by long-term mining and industrial activities. Our study compared heavy-metal bioaccumulation and associated human health-risks in fish sampled 17 years apart, in 2008 and 2025. Three dominant cyprinid fish species were examined: Barbus barbus, Squalius cephalus, and Chondrostoma nasus. Concentrations of Cd, Cr, Cu, Hg, Ni, Pb, and Zn in muscle, liver and kidney tissue were determined by atomic absorption spectrometry. Although the total hazard index (HI) remained below the critical threshold of 1.0 for the average consumer (HI(2025) = 0.73), the toxicological profile changed significantly. In 2008, Hg and Pb were the predominant risk drivers, whereas in 2025 Cd and Ni became more prominent. Mean Cd concentrations in edible muscle increased significantly (from 0.049 to 0.459 mg/kg in barbel and from 0.054 to 0.426 mg/kg in chub). Mean Ni also increased in chub, reaching a level of 4.25 mg/kg. Multivariate analysis indicated a clear separation of muscle samples between the two sampling years, reflecting a shift in chemical and risk profiles. Tissue distribution patterns further suggested a possible breakdown in the detoxification organs’ barrier function in 2025. These findings highlight the importance of continued monitoring of Cd and Ni in fish muscle to protect consumer health.