Elevated levels of Pb, Mn and Cd in deep aquifers of Gazipur, Bangladesh: A threat to drinking water safety and public health

This study aimed to measure trace metal concentrations in 144 groundwater samples from all five Upazilas of Gazipur district, Bangladesh. The study also evaluated groundwater suitability for drinking using five water quality indices and assessed potential cancer and non-cancer health risks in adults and children from trace metal exposure through ingestion and dermal absorption. The mean concentrations of As, Pb, Cd, Cu, Zn, Fe, and Mn in groundwater were 0.292 µg l^-1, 0.127, 0.001, 0.034, 0.013, 0.085, and 0.195 mg l^-1, respectively. Among the trace metals, Pb, Mn, and Cd levels exceeded drinking standards in 47.2%, 29.2%, and 6.2% of samples, respectively. The study findings showed that deeper wells increased most of the physicochemical properties of groundwater, including the contents of Cu, Cd, and Pb, while shallower wells <200 feet deep showed significantly elevated concentrations of As and Mn. A total of 47, 57, 56, and 75 sites in the district were identified as problematic based on computed scores of the water quality index (WQI), trace metal pollution index (TMPI), trace metal contamination index (TMCI), and trace metal evaluation index (TMEI), respectively. Among the Upazilas, the groundwater of Gazipur Sadar was categorized as highly polluted for drinking purposes, followed by Kaliakoir, Kaliganj, Kapasia, and Sreepur. The calculated hazard index (HI) values for adults and children due to oral and dermal exposures to trace metals in groundwater were below 1.0, indicating no potential non-cancer health risks. However, the calculated incremental lifetime cancer risk (ILCR) from toxic metals was found to be 29.2% for adults and 29.9% for children in groundwater supplies, which was greater than the threshold value. This study, in conclusion, is anticipated to provide valuable insights for ensuring a safe water supply for urban residents and promoting sustainable groundwater resource management to mitigate health risks.