title: Mapping human health risks from exposure to trace metal contamination of drinking water sources in Pakistan.
abstract: The consumption of contaminated drinking water is one of the major causes of mortality and many severe diseases in developing countries. The principal drinking water sources in Pakistan, i.e. ground and surface water, are subject to geogenic and anthropogenic trace metal contamination. However, water quality monitoring activities have been limited to a few administrative areas and a nationwide human health risk assessment from trace metal exposure is lacking. Using geographically weighted regression (GWR) and eight relevant spatial predictors, we calculated nationwide human health risk maps by predicting the concentration of 10 trace metals in the drinking water sources of Pakistan and comparing them to guideline values. GWR incorporated local variations of trace metal concentrations into prediction models and hence mitigated effects of large distances between sampled districts due to data scarcity. Predicted concentrations mostly exhibited high accuracy and low uncertainty, and were in good agreement with observed concentrations. Concentrations for Central Pakistan were predicted with higher accuracy than for the North and South. A maximum 150-200 fold exceedance of guideline values was observed for predicted cadmium concentrations in ground water and arsenic concentrations in surface water. In more than 53% (4 and 100% for the lower and upper boundaries of 95% confidence interval (CI)) of the total area of Pakistan, the drinking water was predicted to be at risk of contamination from arsenic, chromium, iron, nickel and lead. The area with elevated risks is inhabited by more than 74 million (8 and 172 million for the lower and upper boundaries of 95% CI) people. Although these predictions require further validation by field monitoring, the results can inform disease mitigation and water resources management regarding potential hot spots.
authors: Institute for Environmental Sciences, University of Koblenz-Landau, Fortstrasse 7, D-76829 Landau in der Pfalz, Germany.
authors: Avit Kumar
authors: AK
authors: Bhowmik
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, PR China.
authors: Ambreen
authors: A
authors: Alamdar
authors: Aristotle University of Thessaloniki, Department of Chemistry, Division of Chemical Technology, Box 116, Thessaloniki 54124, Greece.
authors: Ioannis
authors: I
authors: Katsoyiannis
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, PR China.
authors: Heqing
authors: H
authors: Shen
authors: Department of Environmental Sciences, FBAS, International Islamic University, Islamabad, Pakistan.
authors: Nadeem
authors: N
authors: Ali
authors: Center of Excellence in Environmental Studies, King Abdulaziz University, Jeddah, Saudi Arabia.
authors: Syeda Maria
authors: SM
authors: Ali
authors: Public Health and Environment Division, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan.
authors: Habib
authors: H
authors: Bokhari
authors: Institute for Environmental Sciences, University of Koblenz-Landau, Fortstrasse 7, D-76829 Landau in der Pfalz, Germany.
authors: Ralf B
authors: RB
authors: Schäfer
authors: Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, PR China; Public Health and Environment Division, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan. Electronic address: ali_ebl2@yahoo.com.
authors: Syed Ali Musstjab Akber Shah
authors: SA
authors: Eqani
mesh_terms: D060766:Drinking Water / Q000737:chemistry*; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D006801:Humans; D008670:Metals / Q000032:analysis*; D010154:Pakistan; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data*
chemical_list: D060766:Drinking Water; D008670:Metals; D014874:Water Pollutants, Chemical
keywords: Geographically weighted regression; Ground water; Pakistan; Risk mapping; Surface water; Trace metals