Pollution Evaluation and Health Risk Assessment of Trace Metals in Eleven Tissues of Mylopharyngodon piceus Collected from an Aquaculture Pond in Huzhou, near Southern Taihu Lake

Pollution evaluation and health risk assessment are critical procedures for residents consuming black carp ( Mylopharyngodon piceus ) contaminated with non-essential hazardous trace elements in an artificial wetland also known as an aquaculture pond. Samples were collected, dissected and digested to analyze the pollution status and health risk associated with four heavy metals present in eleven tissues of black carp fish based on the metal pollution index ( MPI ) and target hazard quotient ( THQ ). The results indicated that the concentrations of Cd, Cr, Cu and Pb were 1.36 ± 0.04 mg/kg, 13.70 ± 0.50 mg/kg, 2.85 ± 0.10 mg/kg, and 4.98 ± 0.18 mg/kg in large black carp, while the concentrations of Cd, Cr, Cu and Pb were 4.27 ± 0.08 mg/kg, 50.84 ± 0.82 mg/kg, 9.33 ± 0.18 mg/kg, and 22.49 ± 0.42 mg/kg in small specimens. The MPI values showed that the heavy metal pollution detected in small fish was much more significant than in large fish. Notably, the polluted metals were more likely to accumulate in the viscera (e.g., brain and heart) rather than in the external tissues (e.g., muscle and epidermis). In addition, the estimated THQ and HI values for three edible tissues demonstrated that the health risk associated with muscle tissue intake of both small and large black carp was within the acceptable range, while the contaminants were likely to pose health risks associated with the consumption of fish head tissue. Small black carp are generally not fit for human consumption, thus both the epidermis and muscle of the fish are often cooked in China. However, the ingestion of large black carp is relatively safe. The contributions to THQ values of these four heavy metals decreased in the following sequence: Cr > Pb > Cd > Cu. Cr is the critical pollutant with its contribution to HI values measuring over 50%. We suggest that in artificial wetlands (e.g., aquaculture ponds) more attention should be paid to heavy metal pollution, the conservation of the aquaculture ecosystem, and effects on human health.