Characterization, Source Apportionment and Health Risk Assessment of Trace Metals in Groundwater of Metropolitan Area in Lahore, Pakistan

The quality of groundwater resources is deteriorating worldwide since last few decades. Evaluating trace metal contents, sources, and their potentially harmful effects in the groundwater are the most important factors for assessing human health risks. The current study was aimed to characterize potentially toxic and essential metals (Pb, Cd, Cr, Co, Ni, Mn, Ag, Li, Cu, Fe, Zn, Sr, Na, K, Ca and Mg) and physiochemical parameters in the groundwater of Lahore, Pakistan in pre- and post-monsoon seasons. Significant spatial/seasonal variations were observed in the metal levels; Fe, Zn, Co, and Cu contents were comparatively higher in pre-monsoon, whereas, Mn, Cd, Cr, Pb and Ni levels were elevated in post-monsoon season. Mean levels of Ni, Pb, Co, Cr and Cd were exceeding the national and international permissible limits. Multivariate analysis revealed major anthropogenic contamination of the groundwater (mostly emanating from domestic wastes, automobile emissions, industrial effluents and combustion processes) while significant contributions were observed for mixed sources. Health risk assessment showed that non-carcinogenic risks in terms of hazard quotient (HQ(ing)) for children exceeded the safe level (HQ(ing) > 1) for Co, Cd, and Pb in pre-monsoon whereas Ni and Cr surpassed the safe limit in post-monsoon. In case of adults, Co and Pd were in excess of the safe limit in both seasons. This study revealed that children are more vulnerable to non-carcinogenic risks than adults. In addition, the carcinogenic health risks associated with Pb, Ni, Cd, and Cr contents were significantly elevated than the safety limit (1.0 x 10(-06)). Thus, it is highly recommended that the groundwater should be continuously monitored and appositely treated before ultimate use.