Seasonal Dynamics of Trace Metal Pollution in Drinking Water and Its Potential Health Impacts in the Southeastern Coastal District of Bangladesh

Groundwater contamination by trace metal poses significant environmental and public health risks, particularly in developing countries where groundwater is a major drinking water source. This study evaluates seasonal variation of trace metals (Al, Cu, Fe, Mn, Cr and As) and associated risks in southeastern Bangladesh. The concentration of As and Mn exceeded tolerable limits during dry period and Fe exceeded permissible limits in both seasons. Drinking water potability was assessed through the Heavy Metal Evaluation Index (HEI), Heavy Metal Pollution Index (HMPI), and Nemerow’s Pollution Index (NI) resulting poorer water quality during the dry season. Chronic non-carcinogenic health risk evaluated using Hazard Quotient (HQ) and Hazard Index (HI) was highest for As and Mn, with 82% in the wet season and 68% in the dry season, and falling into the medium-to-high HI risk categories. In both seasons, the highest HI values were associated to oral intake, exhibiting maximum HI values of 37.726 (adults) and 48.659 (children) in the wet season. Carcinogenic risk or Lifetime Cancer Risk (LTCR) was slightly higher during the wet season, especially in Lakshmipur and Noakhali, with children being the most vulnerable group. During wet season, 99% children and 89% adults crossed the high risk threshold, barely one adult fell below low category and nearly none of the children did. The wet season child mean LTCR was 3.63×10⁻³, indicating 3 times higher cancer risk than dry season. Continuous monitoring and mitigation measures are recommended, particularly in Chittagong and Lakshmipur, to reduce pollution exposure and protect public health.