What question did this study set out to answer?

This research aims to evaluate the bioaccumulation of heavy metals in various tissues of fish exposed to treated wastewater.

March 1, 2026Open Access

Bioaccumulation of Metals in Brain, Eye, Skeleton, and Skin Tissues of Wastewater-Fed Fish: A Case Study in Turkey

Key Points

This research aims to evaluate the bioaccumulation of heavy metals in various tissues of fish exposed to treated wastewater.
Analyzed metal concentrations (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in brain, eye, skeleton, and skin of Carassius gibelio fish.
Conducted statistical analyses including Principal Component Analysis (PCA), ANOVA, and Pearson correlation to assess metal accumulation.
Calculated transfer factor (TF) to determine bioaccumulation levels and hazard coefficient (HQ) for assessing toxicity.
High concentrations of Cd and Pb were detected in all fish tissues, exceeding safety standards.
Zn and Fe were generally the most abundant metals across different tissues.
Bioaccumulation (TF > 1) was identified for all metals, but only Pb showed a hazard coefficient (HQ) > 1, indicating carcinogenic risk.

Abstract

In this study, the metal accumulation (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) and toxicity status in the brain, eye, skeleton, and skin tissues of Carassius gibelio species of fish fed with wastewater treated with secondary treatment were investigated, and the usability of wastewater and fish for human food against climate change and food crisis was investigated. Treated wastewater (TWW) complied with Turkish aquaculture standards, but was not found to comply with drinking and irrigation water standards. The national and international food standards for metal concentrations varied. Cd and Pb were found to be high in all tissues according to all standards, but Cu, Cr, Mn, Ni, Fe, and Zn were found to vary according to tissues. It was determined that Fe and Zn concentrations were generally higher than those of the other metals in all tissues. The orders of the metals according to their annual mean concentrations were: Zn > Fe > Mn > Pb > Ni > Cr > Cu > Cd in skeletons; Zn > Fe > Pb > Ni > Cr > Cu > Mn > Cd in skins; Zn > Fe > Cu > Pb > Mn > Ni > Cr > Cd in eyes; and Fe > Zn > Pb > Cu > Cr > Ni > Mn > Cd in brains. Concentrations in tissues were higher in the summer months, but seasonal changes were statistically insignificant (p ≥ 0.05). According to Principal Component Analysis (PCA), ANOVA, and Pearson correlation analysis, it was statistically determined that Cd, Cr, Cu, Mn, Ni, and Pb, and the other two elements (Fe and Zn), showed similar accumulation characteristics among themselves. According to transfer factor (TF) calculations, it was determined that there was bioaccumulation (TF > 1) in all tissues for all metals throughout the year, but according to hazard coefficient (HQ) values, only Pb was determined to be >1 and carcinogenic. As a result, after the wastewater is treated with different advanced treatment methods and brought to potable water standards, the accumulation of metals and other micropollutants in the tissues of different species of fish should be monitored for many years.

Bioaccumulation of Metals in Brain, Eye, Skeleton, and Skin Tissues of Wastewater-Fed Fish: A Case Study in Turkey

Key Points

Abstract

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