Manganese occurrence in groundwater and health risk assessment: a case study in various Upazillas of Chattogram district of Bangladesh

Access to safe drinking water is crucial for Bangladesh and other developing nations working toward sustainable development. One major concern for Bangladesh is the increasing levels of manganese in its groundwater. Manganese contamination primarily stems from the weathering of minerals in the Karnaphuli basin, seawater intrusion in coastal aquifers, and excessive groundwater extraction. This study aimed to assess the levels of manganese in four upazilas of Chattogram district, which is the commercial center of Bangladesh. A total of 36 water samples were collected from various tube wells in Raozan, Rangunia, Hathazari, and Boalkhali upazilas. Among the four upazilas, Rangunia had the highest manganese concentration (4.33 mg/L), followed by Raozan, Boalkhali, and Hathazari. Around 16.67% of the samples exceeded the drinking water threshold, while the remaining samples met the acceptable criteria. The study also examined the health risks associated with manganese-contaminated water. Children had an average hazard quotient of 0.204, while adults has an average of 0.214. A geographical mapping analysis revealed a heightened risk level in the northern Rangunia Upazila and a small section of Raozan. This study highlights the importance of continuous monitoring and the implementation of precautionary measures to ensure the provision of safe drinking water in the study area.