Preliminary assessment of trace elements in surface and deep waters of an urban river (Korotoa) in Bangladesh and associated health risk.

Korotoa River is one of the most important urban rivers in Bangladesh for its utilization in various activities like agriculture, aquaculture, fishing, cooking, and other purposes. There have been some reports on the trace element (TE) levels in the surface water of Korotoa River, but its deep water has never been studied. Therefore, the author measured 10 TEs (As, Cd, Pb, Hg, Cr, Ni, Cu, Fe, Mn, and Zn) in surface and deep water samples and assessed their health risks for residential and recreational receptors. The levels of studied elements in deep water were slightly higher than those in surface water except for Cd, Cr, Cu, Mn, and Zn during the dry season and Pb, Hg, and Fe during the wet season. Total TE levels in both surface and deep waters were higher in the dry season than in the wet season. The levels of trace elements in both surface and deep waters were much higher than the guideline values for safe limits of drinking water and the protection of freshwater aquatic life, indicating that water from this river is not safe for drinking and/or cooking purposes. All hazard quotient (HQ) and hazard index (HI) values were higher than the risk threshold of unity. HI values for children were higher than those for adults, indicating that the health of children is at dramatically higher risk than that of adults. Arsenic, Pb, and Hg for the water ingestion pathway were the primary contributors to total risk (HI), while As and Cr for the dermal pathway, indicating that As, Pb, and Cr, among the TEs, are major contributors to total health risk. Total carcinogenic risk values of As and Cr in surface and deep waters were higher than the target risk of 1 × 10-4, indicating that TEs in surface and deep waters of the Korotoa River might pose health risks to the residential and recreational users. The results of this study can provide the basic data for efficient water management and human health protection in Bangladesh.