Assessment and bioaccumulation of heavy metal contaminants in Golden Mahseer (Tor putitora Hamilton, 1822)

Unpolluted freshwater is a crucial component for maintaining the health of humans. This study aimed to investigate the bioaccumulation and potential health hazards of heavy metal contaminants (Fe, Cd, Cr, Cu, Pb) in water, sediments, and tissues of the golden mahseer fish (Tor putitora) from Zhob River to assess their suitability for human consumption. Samples (soil, water, and fish) were collected from the Zhob River, and Flame Atomic Absorption Spectrometry (FAAS) was employed to measure the concentration of these metals found in soil, water, and various fish body tissues (muscles, skin, gills, and liver). The overall results revealed that water quality parameters, i.e., temperature and pH were found within tolerable ranges, while electrical conductivity and turbidity exceeded the permissible limits of FAO/WHO for fish. Furthermore, this study also identified elevated concentrations of Pb in water and soil, as well as Fe and Cd in soil beyond the standards set by the World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA). In contrast, the concentrations of other targeted metals examined in fish body tissues were found below the permissible limits set by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO), indicating the suitability of this fish species for human consumption. The estimated daily intake (EDI) of these targeted metals in various fish body tissues was found to be within the recommended dietary allowance (RDA), suggesting no associated health risks for the local population. Furthermore, both the Target Hazard Quotient (THQ) and Total Target Hazard Quotient (TTHQ) values measured in this study were less than one, indicating the absence of potential non-carcinogenic health risks related to the consumption of this riverine mahseer fish, but combined metal intake may pose potential health risks. Carcinogenic risk assessment for some metals like Cd, Cr, and Pb revealed no cancer risk for consumers. Moreover, our present research observed comparatively high bioaccumulation (BAF) of each targeted metal in the fish liver from both Zhob River water and soil as compared to other body tissues. Multivariate analysis, including the correlation matrix, revealed strong and significant correlations (P < 0.05) among heavy metal pairs (Fe/Cr, Fe/Pb, Cr/Fe, Cr/Pb, Pb/Fe, Pb/Cr). Hierarchical cluster analysis and Principal Component Analysis (PCA) were utilized to trace the origins of these metals, attributing their presence to nearby rock weathering, mining, as well as municipal and agricultural activities. These factors were recognized as potential sources of heavy metal bioaccumulation in riverine fish. Thus, our current study concluded that the Zhob River was contaminated with these heavy metals and emphasized the need to prevent domestic and industrial sewage inflow. The monitoring of these metals in the food chain was also underscored as crucial for reducing all kinds of associated health risks. This study provides the first report on heavy metal distribution in highly abundant and edible mahseer fishes of the Zhob River.