The River Ganga, despite its immense religious and cultural significance, has been increasingly degraded in terms of water quality due to the continuous discharge of untreated domestic sewage, industrial effluents, and chemical wastes, particularly along the Patna stretch. Urban drains serve as major conduits for heavy metals into rivers, contaminating the aquatic environment and posing significant environmental and public health concerns. In this context, the present study aims to quantify the contribution of urban drains to metal(loid)s contamination in the Ganga River at Patna and to assess the associated ecological and human health risks. A total of 20 samples, each collected from 20 stations located in 8 regions, were analyzed for 15 metal(loid)s during the summer and winter seasons of 2022 and 2023, respectively. Several toxic metal(loid)s, particularly Al (up to 11.81 mg/l), Pb (0.29 mg/l), Fe (1.36 mg/l), Cr (0.18 mg/l), and As (0.03 mg/l), exceeded the Bureau of Indian Standards (BIS), World Health Organization (WHO) and United States Environmental Protection Agency (USEPA) standard values, indicating the unsuitability of the water for drinking purposes. Approximately 65% of the samples showed high Metal Pollution Index (MPI) values, with extreme levels recorded at drain sites (MPI up to 283 in summer and 242 in winter). The Ecological Risk Index (ERI) revealed considerable ecological risk near drains (up to 399 in winter) and moderate risk at downstream locations. While the Total Hazard Index (THI) remained below 1 for both adults (0.0869 in summer; 0.061 in winter) and children (0.0867 in summer; 0.072 in winter), suggesting no significant non-carcinogenic risk, the incremental lifetime cancer risk (ILCR) values for As (up to 7.2 × 10⁻³) and Cr (up to 4.7 × 10⁻³) exceeded the critical value (1.0 × 10⁻³), indicating potential carcinogenic risk under long-term exposure. These findings highlight the substantial impact of urban drains on riverine contamination with metal(loid)s and provide critical baseline data for evidence-based management and restoration of the Ganga River.
Raj et al. (Sat,) studied this question.