Assessment of Nitrate Contamination and Non‐Carcinogenic Health Risk in the Mitidja Groundwater, Northern Algeria

ABSTRACT Groundwater contamination by nitrates (NO 3 − ) poses a major environmental and public health risk worldwide. This study investigates nitrate pollution in the Mitidja aquifer (Algeria) using the Nitrate Pollution Index (NPI) and non‐carcinogenic risk assessment through the hazard quotient ( HQ ) method proposed by the US Environmental Protection Agency (USEPA). Forty‐nine groundwater samples were collected in 2019–2026 during the wet season and 23 during the dry season. Nitrate concentrations were analyzed using the Gaussian mixture model (GMM) for cluster classification, while non‐carcinogenic risks were estimated for adults and children through Monte Carlo simulations (10 000 iterations) to quantify parameter uncertainty. Results reveal that 42.3% of wet season and 43.5% of dry season samples exceed the World Health Organization (WHO) guideline of 50 mg/L. GMM identified two clusters per season, distinguishing moderately and highly contaminated zones. Based on NPI, 50% of wet season samples and 47.5% of dry season samples were classified as “clean to low pollution,” while 38.5% and 43.4%, respectively, indicated “high to very high pollution.” HQ values ranged from 0.06 to 7.18 (children) and from 0.02 to 3.08 (adults) in the wet season and from 0 to 7.81 (children) and from 0 to 3.34 (adults) in the dry season. Probabilistic results showed 25th–95th percentile HQ values of 0–8.95 for children and 0–2.94 for adults in the wet season, and 0–8.34 and 0.027–2.72, respectively, in the dry season. Sensitivity analysis confirmed children's higher vulnerability to nitrate exposure. These results highlight the urgent need for groundwater protection and remediation strategies in the Mitidja region.