Heavy metal pollution and health risk assessment in surface waters impacted by pharmaceutical effluents in Gazipur and Narayanganj, Bangladesh.

Surface water contamination by heavy metals (HMs) is a growing concern in industrial regions of Bangladesh. This study assessed HM levels and associated health risks in surface water near pharmaceutical-industrial zones in Gazipur and Narayanganj. Twelve samples were collected from the Turag and Shitalakshya rivers and analyzed for ten metals (As, Pb, Cd, Cr, Ni, Cu, Zn, Hg, Fe and Mn) using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Pollution levels were evaluated using the Heavy Metal Pollution Index (HPI), Heavy Metal Evaluation Index (HEI), Water Pollution Index (WPI) and Heavy Metal Toxicity Load (HMTL). Non-carcinogenic and carcinogenic risks were estimated for adults and children through ingestion and dermal exposure. Mean concentrations of Pb (153 ppb), Fe (1380 ppb), and Hg (7 ppb) exceeded WHO guideline values at most sites, and several locations showed HPI and WPI values above 100, indicating critical pollution. Hazard quotients for Pb and Cd were greater than 1 in children, and cancer risk from As and Cr was above the acceptable range. Multivariate statistical analyses such as principal component analysis and hierarchical clustering suggested pharmaceutical effluents as a dominant source. Correlation analysis supported the presence of common contamination origins, notably a strong positive correlation between Fe and Hg (r = 0.89) and between Pb and Ni (r = 0.94). These findings highlight the need for stricter effluent control and regular monitoring of surface water in industrial areas.