Bioaccumulation of lead, arsenic, and mercury in vital organs of common carp ( L.): Assessment of pathological effects and possible hazards associated with human consumption.

Background: Pollution of aquatic environments with heavy metals causes severe adverse effects on fish, invertebrates, and human. The importance of this study lies in the fact that long-term ingestion of heavy metal-contaminated fish can result in the accumulation of harmful metals in numerous organs and pose a major risk to human health.

Aim: The current study was designed to investigate the concentrations of toxic arsenic (As), lead (Pb), and mercury (Hg) in the liver, gills, and muscles of highly consumed aqua cultured common carp ( L.) in Baqubah city, to evaluate the toxicopathological bioaccumulation of As, Pb, and Hg in consumed fish and the potential human health risk after consumption and give clear indication for a status of heavy metal contamination for water used in aquaculture of common carp ( L.).

Methods: A total of 10 Fresh fish of common carp ( L.) were randomly selected from local Baqubah markets/Diyala province/Iraq in different interval from September 2022 to January 2023. The source of fish in Baqubah's local markets is fish aquacultured in earthen ponds as well as cages in the Tigris River in Diyala province. Flame atomic absorption spectrometer was used to estimate the level of As, Pb, and Hg in liver, gills, and muscles of collected fish. Histopathological sections were prepared for evaluation of toxic pathological effects of metals on organs.

Results: Bioaccumulation of arsenic and lead in liver, gill, and muscle samples was within and less than the permissible limit set by WHO while the bioaccumulation of mercury exceeds the permissible limits set by WHO. Histopathological findings of the gill section showed telangictatisis and epithelial lifting in secondary lamellae with hemorrhage and blood congestion and central venous dilation and epithelium hyperplasia with complete fusion of the secondary lamellae and edema in the filamentary epithelium in addition to mononuclear cells infiltration. Histopathological findings of liver revealed degenerative and necrotic changes in liver tissue distinguished by pyknosis with the existence of necrosis in cells and dilation of the sinusoids with cytoplasmic vacuolation.

Conclusion: The bioaccumulation of mercury is higher than permitted levels in common carp () which indicates high contamination level of main sources for fresh waters in Diyala province mainly from Diyala and Tigris rivers.