Bioaccumulation of heavy metal contaminants in the water, sediments, and tissues of Tor putitora (Golden Mahseer) collected from the Zhob River

Introduction

Unpolluted freshwater is a crucial component for maintaining human health. The present study aimed to investigate the bioaccumulation of heavy metal contaminants (Fe, Cd, Cr, Cu, and Pb) in water, sediments, and tissues of Tor putitora for assessing their suitability for human consumption.

Methods

Fish, water, and soil samples were collected from the Zhob River, and Flame Atomic Absorption Spectrometry (FAAS) was employed to assess the level of heavy metal contamination.

Results

Water quality parameters (temperature and pH) were within suitable ranges, but electric conductivity and turbidity exceeded permissible limits. High concentrations of Fe and Cd in soil and Pb in both water and soil were noted, surpassing WHO and USEPA standards. Despite elevated Fe levels, the examined metal concentrations in fish tissues were below FAO/WHO limits, indicating safe human consumption. Estimated daily intake (EDI) showed no health risk for the local population. Non-carcinogenic risk assessment indicated individual metal consumption safety, but combined metal intake may pose potential health risks. Carcinogenic risk assessment for Cd, Cr, and Pb revealed no cancer risk for consumers. 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, and Pb/Cr). Hierarchical cluster analysis and principal component analysis (PCA) identified the origins of these metals, attributing their presence to the nearby weathering of rocks and mining, municipal, and agricultural activities. These factors were recognized as potential sources of heavy metal bioaccumulation in riverine fish.

Conclusions

This study concluded that the Zhob River was contaminated with heavy metals, emphasizing the need to prevent domestic and industrial sewage inflow. Monitoring these metals in the food chain is crucial for reducing associated health risks. This study provides the first report on heavy metal distribution in the Zhob River's highly abundant and edible mahseer fishes.