Groundwater quality and health risks for drinking and irrigation in densely populated Qalyubia, Egypt

This study comprehensively assesses groundwater suitability for drinking and irrigation and evaluates the associated non-carcinogenic health risks for children and adults in the urban, densely populated Qalyubia Governorate, South Nile Delta, Egypt. Groundwater samples from ten sites were analyzed for thirteen chemical parameters. An integrated approach to water quality assessment was applied, using the Water Quality Index (WQI), multiple irrigation indices, the Metal Index (MI), and the Heavy Metal Pollution Index (HPI) against World Health Organization (WHO) and Egyptian water quality standards. Key findings reveal an apparent yet explainable divergence between the indices: while the WQI (22-36) and irrigation indices indicated good overall water quality for both drinking and irrigation, the Metal Index (MI: 0.81-3.29) signaled a "moderately affected" status. This contrast underscores that the WQI, which integrates a broad suite of physicochemical parameters, can reflect generally good conditions, whereas the MI is specifically sensitive to the presence of even low concentrations of potentially toxic elements (PTEs) such as Fe, Mn, Cd, As, Cr, Pb, Hg, Ni, and Zn. The HPI values (≤ 15) indicated minimal pollution from PTEs. No significant non-carcinogenic health risks were identified for the analyzed metals, though children were more susceptible than adults. The study concludes that although the groundwater is generally suitable for use, the MI results provide a critical early warning of moderate metal pollution, necessitating regular monitoring and preemptive measures to safeguard public health and water resources.