Human health risk assessment of potentially toxic elements in drinking water of Hamedan province, Iran

Abstract

Access to safe drinking water is a fundamental human right and a critical determinant of public health. This study presents a comprehensive health risk assessment of potentially toxic elements (PTEs) in the drinking water distribution networks of Hamedan Province, western Iran. In 2023, 50 drinking water samples were collected across ten counties, representing both urban and rural areas. Concentrations of As, Cd, Cr, Hg, and Pb were quantified using inductively coupled plasma-mass spectrometry (ICP-MS), strictly adhering to quality assurance/quality control (QA/QC) protocols. The analytical results revealed that while mean concentrations of Pb (2.2 µg/L), Hg (1.25 µg/L), Cr (1.1 µg/L), and Cd (0.15 µg/L) were within the WHO permissible limits, arsenic concentrations posed a significant public health concern, with a mean value of 14.6 µg/L, exceeding the WHO guideline of 10 µg/L. The observed abundance sequence was As > Pb > Hg > Cr > Cd. Health risk assessment, conducted using USEPA models, identified non-carcinogenic hazards primarily driven by arsenic, with the Hazard Index (HI) surpassing the safe threshold (HI > 1) for both children (HI = 3.26) and adults (HI = 1.39). Furthermore, the Incremental Lifetime Cancer Risk (ILCR) associated with arsenic ingestion was calculated as 1.1 × 10⁻⁴ for children and 9.6 × 10⁻⁶ for adults, exceeding the acceptable USEPA range (10⁻⁶ to 10⁻⁴), particularly for the vulnerable pediatric population. Based on these findings, the following policy and management interventions are recommended: (1) immediate implementation of targeted Water Safety Plans (WSP) focused on arsenic surveillance and mitigation, especially in high-risk areas such as Kabudarahang and Malayer; (2) upgrading water treatment infrastructure with advanced technologies, such as adsorption or coagulation-filtration, specifically tailored for arsenic removal; and (3) establishing a continuous, spatially-informed monitoring program for PTEs, particularly in groundwater sources proximal to industrial and agricultural zones. This study provides essential evidence-based data to support informed policy-making for the protection of water quality and public health in Hamedan Province.