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 analysed 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 (R 2 = 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 emphasise the need for stricter regulation of industrial discharge and poultry feed management.