JOURNAL OF ENVIRONMENTAL SCIENCES ISSN 1001-0742 CN 11-2629/X www.jesc.ac.cn Available online at www.sciencedirect.com Journal of Environmental Sciences 2013, 25(10) 2003–2013 Health risks associated with heavy metals in the drinking water of Swat, northern Pakistan Kifayatullah Khan 1,2 , Yonglong Lu 2, ∗ , Hizbullah Khan 1 , Shahida Zakir 1 , Ihsanullah 3 , Sardar Khan 1 , Akbar Ali Khan 1 , Luo Wei 2 , Tieyu Wang 2 1. Department of Environmental Sciences, University of Peshawar, Peshawar 25120, Pakistan. E-mail: mr khann84@yahoo.com 2. State Key Laboratory of Urban and Regional Ecology, Research Centre for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 3. Nuclear Institute for Food and Agriculture, Tarnab, Peshawar, Pakistan Received 24 December 2012; revised 02 May 2013; accepted 21 May 2013 Abstract The concentrations of heavy metals such as Cd, Cr, Cu, Mn, Ni, Pb and Zn were investigated in drinking water sources (surface and groundwater) collected from Swat valley, Khyber Pakhtunkhwa, Pakistan. The potential health risks of heavy metals to the local population and their possible source apportionment were also studied. Heavy metal concentrations were analysed using atomic absorption spectrometer and compared with permissible limits set by Pakistan Environmental Protection Agency and World Health Organization. The concentrations of Cd, Cr, Ni and Pb were higher than their respective permissible limits, while Cu, Mn and Zn concentrations were observed within their respective limits. Health risk indicators such as chronic daily intake (CDI) and health risk index (HRI) were calculated for adults and children separately. CDIs and HRIs of heavy metals were found in the order of Cr > Mn > Ni > Zn > Cd > Cu > Pb and Cd > Ni > Mn > Cr > Cu > Pb > Zn, respectively. HRIs of selected heavy metals in the drinking water were less than 1, indicating no health risk to the local people. Multivariate and univariate statistical analyses showed that geologic and anthropogenic activities were the possible sources of water contamination with heavy metals in the study area. Key words: daily intake; drinking water; health risk; heavy metals; multivariate analysis DOI: 10.1016/S1001-0742(12)60275-7 Introduction Water is considered as a vital substance in the environment (Shah et al., 2012), and its contamination with heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) is a worldwide environmental problem (Muhammad et al., 2011). Generally, heavy metals are released from different natural (i.e., weathering, erosion of bed rocks, ore deposits and volcanic activities) and anthropogenic (i.e., mining, smelting, industrial influx and agricultural activ- ities) sources. They can contaminate the surface (river) and ground (spring, dug well and tube well) water that is used for domestic, agricultural and industrial purposes (Ettler et al., 2012; Krishna et al., 2009; Khan et al., 2008). Surface and ground drinking water contamination is a worldwide health concern, which is becoming increasingly important since 1990s with the unprecedented population growth, urbanization and industrialization (Khan et al., * Corresponding author. E-mail: yllu@rcees.ac.cn 2012; Rapant and Krˇ cmov´ a, 2007). pH is one of the most important indicators of water quality and level of pollution in the aquatic ecosystem (Jonnalagadda and Mhere, 2001). Although it has no direct effects on human health, pH affects some of the water quality parameters such as ionic solubility and pathogens survival, which will impact the human health eventually. In addition, high range pH confers bitter taste to water (Muhammad et al., 2010; WHO, 2008). Heavy metal enrichment also adversely affects the drinking and irrigation quality of water (Krishna et al., 2009). Ingestion of water containing certain amount of heavy metals may cause health problems in human, including shortness of breath and various types of cancers (Kavcar et al., 2009). Some essential metals like Cu, Mn and Zn are required for normal body growth and function. However, excess amount of these metals could also be harmful. High concentrations of Cd, Cr, Ni and Pb are considered highly toxic in human and aquatic organisms (Ouyang et al., 2002). Their accumulation in the body can cause serious