Integrated Assessment of Antimony and Essential Trace Elements in Groundwater: Probabilistic Health Risks, Geochemical Interpretation, and Management Implications for Dalbandin, Pakistan

Iron (Fe), zinc (Zn), cobalt (Co), and antimony (Sb) are trace elements. Iron, zinc, and cobalt are essential; antimony is toxic. This study presents the first comprehensive assessment in 50 groundwater samples from Dalbandin, an arid, mineral-rich region of Balochistan, Pakistan. Concentrations ranged from 0.23 to 1.01 mg/L for Fe, 1.98 to 3.00 mg/L for Zn, 0.32 to 0.97 mg/L for Co, and 0.14 to 0.61 mg/L for Sb. Iron exceeded the World Health Organization (WHO) acceptability threshold of 0.3 mg/L in 88% of samples; antimony exceeded the 0.02 mg/L WHO guideline in all samples (mean 0.423 mg/L, 21× above); and Cobalt exceeded the 0.006 mg/L United States Environmental Protection Agency (USEPA) tapwater screening level in all samples (mean 0.673 mg/L, ∼112× above). The Drinking Water Quality Index (DWQI) classified all samples as "Unsafe" (mean: 3,400). Health risk assessment revealed (HI) > 1 for all samples, with Sb contributing ∼97% of the total; children faced 2.3-fold higher risk than adults. Monte Carlo simulation (10,000 iterations) indicated a model-based probability of HI > 1 of 100%; this was unchanged under log-normal assumptions but is not an empirical certainty of disease. A sensitivity scenario using the USEPA provisional Co reference dose made Co the larger contributor. Correlation and Principal Component Analysis (PCA) are consistent with a common geochemical association of Sb, Co, and Fe but cannot identify its source.