Trace Heavy Metal Contamination of Urban Water Bodies in Central Asia: Its Distribution, Source Detection, and Probabilistic Health Risk Assessment for Recreational and Household Use of Water

The study reports high-level cancer andnoncancer riskscaused by household use of contaminated surface water in Central Asiaand provides a framework for water quality assessment. Water scarcity, security,and deterioration of water quality havebeen serious environmental issues in Central Asia. This study hasinvestigated the contamination of the Esil river, the only transboundaryriver originating in Kazakhstan, and implemented the human healthrisk assessment of heavy metals (HMs; Cd, Pb, Cr(VI), and As) in itsrelevant 15 surface water bodies. HM concentrations in 2893 watersamples were measured over 6 years (2014-2019). The river'swater quality was classified between "marginal" and"good," but nine sites revealed worsened quality duringthe period. The monitored HMs' median concentrations followeda decreasing order of Cr(VI) (0.0015 mg/L) = As (0.0015 mg/L) >Pb(0.0009 mg/L) > Cd (0.00005 mg/L). Human-induced behaviors, especiallyindustrial activities, were observed to influence the water qualitynegatively. Due to the growth of cities, municipal wastes and therelease of pollutants during construction activities were potentialorigins of HMs, too. Two exposure scenarios for the human health riskassessment were investigated: the risks from a recreational activityscenario were acceptable, but concerning values were obtained froma household use scenario, including seven sites with hazard index(HI) > 1 and a maximum cancer risk of 7.22 x 10(-4).