Accumulation of Heavy Metals in Gallus gallus domesticus in Six Different Areas of Bangladesh and Histo-Pathological Evidence in the Brain.

This study quantified concentrations of eight heavy metals-arsenic (As), chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), and mercury (Hg)-in brain, liver, heart, and muscle tissues of domesticated chicken (Gallus gallus domesticus) collected from six environmentally contrasting sites across Dhaka, the coastal zone (Cox's Bazar), and Gaibandha, Bangladesh. A total of 50 samples were analyzed using atomic absorption spectrometry. The Dhaka region exhibited the highest contamination, with Pb reaching 8,344 µg/kg and Ni up to 26,300 µg/kg. Chromium was elevated across all regions, while Zn peaked at 23,826 µg/kg in brain tissue from Dhaka. Arsenic and Hg were detected exclusively in Dhaka. Regionally, Dhaka accounted for 78.8% of the total metal burden, followed by the coastal zone (13.9%) and Gaibandha (7.3%). Human health risk assessment indicated that all target hazard quotient values were below unity; however, Pb, Zn, and Ni suggested potential chronic exposure risks. Carcinogenic risk exceeded the acceptable threshold (1 × 10-4) for Ni across all regions and for Cr in Dhaka and the coastal zone. Positive Matrix Factorization identified three dominant sources (R2 = 0.80): industrial/tannery effluent (Cr-dominated), environmental pollution (Zn-Ni), and feed-related inputs (Zn-Cu). Histopathological analysis revealed severe neuropathological alterations in Dhaka samples, including gliosis, spongiosis, and neuronal necrosis. A strong positive correlation between Pb concentration and neuronal degeneration (r = 0.83, p < 0.01) was observed. These findings demonstrate significant ecological and food safety risks and emphasize the need for stricter regulation of industrial discharge and poultry feed management.