Comprehensive analysis and human health risk assessment of tap water quality in Dhaka City, Bangladesh: Integrating source identification, index-based evaluation, and heavy metal assessment.

Despite potential contamination, tap water remains the primary source of drinking in megacities. However, the sources of heavy metal(oid)s contamination and associated health hazards have not been thoroughly addressed in many developing cities, including Dhaka. Therefore, we made the first attempt to assess tap water quality in Dhaka City using indices, identify pollution sources with state-of-the-art techniques, and quantify associated health risks. Tap water samples from 35 locations were collected and analyzed for physicochemical properties and heavy metal(loid)s concentrations. While most parameters were within acceptable ranges, Hg (1.18 ± 0.15 µg/L) exceeded safety thresholds with concerns for Mn (51.08 ± 2.3 µg/L) and Fe (177.34 ± 5.6 µg/L). The calculated indices indicated that Dhaka City's tap water ranged from unfit (Heavy Metal Evaluation Index, HEI: 2.61), very poor (Heavy Metal Pollution Index, HPI: 95.67, Water Quality Index, WQI: 37.76), moderately affected (Metal Index, MI: 2.61, Synthetic Pollution Index, SPI: 0.96) to slightly polluted (Single-factor Index, Pij: 2.61, Nemerow Pollution Index, NPI: 1.41), healthy but not tasty (Taste Index, TI: 1.8, Health Index, HtI: 10.41), with Matuail, followed by Jurain, being the most contaminated. Non-carcinogenic health risk (NCR) values revealed that children were twice as susceptible to health risks from Pb, Co, and As. Alongside, Carcinogenic health hazards risk (CR) expressed potential cancer risks from Cr