Spatial Distribution, Health Risks and Heavy Metal Pollution Assessment of Surface Water Under Multiple Anthropogenic Stressors: Case Study in Middle Moulouya Watershed, Morocco

The worldwide issue of surface water contamination by heavy metals is a matter of great concern, as it has the potential to affect human health. This study intended to compute heavy metal contamination and human health risks in surface water using the following pollution indices: heavy metal pollution index (HPI), contamination index (CI), metal index (MI), ecological risk index (ERI), human health risk and statistical analysis. For this purpose, eleven water samples were gathered and analyzed by ICP-AES for trace metals such as Pb, As, Zn, Cd, Cu, and Ni. The results showed that heavy metal concentrations varied significantly throughout the study area, with Pb, As, and Cd levels exceeding the WHO limits for drinking purposes. Pollution indices indicated low to high water contamination, with HPI results ranging from 16.41 to 862.18 and from 12.76 to 774.03, above the critical value of 100, requiring serious interventions to reduce heavy metal pollution. MI results range from 0.90 to 20.92 and from 0.70 to 18.41 and CI values range from 0.34 to 20.38 and from 0.15 to 17.86 in the dry and wet periods, respectively, with different contamination levels observed throughout the study area; ERI showed low to considerable ecological risk. Nonetheless, the non-carcinogenic risk, THI < 1, indicates low health risks, while the carcinogenic risk for As and Cd was significantly higher than the negligible threshold of 10⁻⁶, suggesting tolerable health risks. However, managing the contaminated area and minimizing the metal concentrations and predominant routes through which metals impact human health should be priorities for long-term development and to establish a favorable environment.