Public Health Vulnerability Due to the Exposure of Dissolved Metal(oid)s in Tap Water from a Mega City (Dhaka, Bangladesh): Source and Quality Appraisals

Tap water is the sole source of water in urban cities but gradually being polluted by potentially toxic elements due to unplanned urbanization. The south Asian megacity, Dhaka (capital of Bangladesh) encounters drastic water pollution resulting mainly from anthropogenic differential factors. Consumption of such polluted water distributed to residents by pipelines can trigger health risks. Therefore, this study investigated the public health vulnerability associated with dissolved metal(oid)s in tap water collected across Dhaka city. The concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Hg and Pb in measured tap water ranged from 8-156, 7–73, 400-20100, 12–110, 7-101, 12–136, 12–908, 0.03–9.75, 1–5, 0.22–1.30, and 8-118 µg/L, respectively. Among the observed elements, Pb, Cr, and Fe concentrations in 18%, 26%, and 75% of sampling sites, respectively, exceeded the standard guideline criteria of Bangladesh. Entropy-based water quality index demonstrated that ~ 12% of sampling sites possessed water unsuitable for drinking and other household works. The dominant sources of water pollution in this region are industrial effluents and domestic sewage. Both non-carcinogenic and carcinogenic health risks are invoked mostly from ingestion of Co and Pb. Regular consumption of this tap water without further pretreatment may result in detrimental health consequences to both children and adults due to the physiological accumulation of toxic elements over time. This study highlighted a comprehensive scenario of the potentially toxic elements in the tap water of Dhaka city, which will allow policymakers to take adequate measures for sustainable water quality management.