Radon Emission and Cancer Risk in Najaf, Iraq: Field Survey, Epidemiological Analysis, and Hydrogeological Modeling

Abstract

The desiccation of the Najaf depression, historically known as the Sea of Najaf, has eliminated its hydro-saline cover that once functioned as a natural barrier to radon exhalation, raising concerns about enhanced environmental radiation risks. This study aimed to provide an integrated assessment through a combination of field surveys, cancer registry analysis, and hydrogeological modeling (MODFLOW-6 + GWT). Indoor radon concentrations across 24 dwellings averaged 18.09 ± 9.41 Bq·m⁻³, while outdoor levels were 4.50 ± 2.96 Bq·m⁻³, both below the World Health Organization (WHO) reference of 100 Bq·m⁻³. Groundwater samples (n = 10 wells) showed dissolved radon between 0.712 and 2.42 Bq·L⁻¹ (mean 1.669 Bq·L⁻¹), with estimated annual effective doses of 3.44 µSv·yr⁻¹ (children, ingestion) and 23.35 µSv·yr⁻¹ (children, inhalation). National cancer statistics reported an Age-Standardized Incidence Rate (ASIR) of 158.94 per 100,000, with Najaf at 123.7 per 100,000, suggesting a notable disease burden relative to neighboring governorates. Modeling scenarios revealed that persistent desiccation could increase radon flux by ~65%, while hydrological restoration reduced emissions by ~40%. These results highlight that although current exposure levels remain modest, Najaf is environmentally predisposed to escalation, underscoring the urgent need for permanent radon monitoring, targeted cancer screening programs, partial hydrological restoration, and GIS-based surveillance to safeguard public health.