Monte carlo based probabilistic health risk assessment of fluoride in the drinking water of Zanjan, Iran

This is the authors' abstract. We don't add key points for this paper.

This study assessed the probabilistic health risks of fluoride exposure through the drinking water distribution network and storage reservoirs of Zanjan, Iran, using Monte Carlo simulation. Fifty-six water samples were collected in 2024 from groundwater wells, storage reservoirs, and distribution network points. Fluoride concentrations were determined using the SPADNS spectrophotometric method. Chronic Daily Intake (CDI), Target Hazard Quotient (THQ), and Margin of Exposure (MoE) were estimated for children, teenagers, and adults. Uncertainty and variability were evaluated using 100,000 Monte Carlo simulations and sensitivity analysis. The mean fluoride concentration was 0.43 mg/L, below the World Health Organization guideline value. Deterministic assessment indicated THQ values below 1 for all age groups, suggesting no significant non-carcinogenic risk under average exposure conditions. However, children exhibited the highest exposure, and the 95th percentile THQ exceeded unity, indicating potential health concerns for highly exposed individuals. All simulated MoE values remained below the recommended benchmark, suggesting a limited long-term safety margin. Sensitivity analysis identified fluoride concentration and drinking water ingestion rate as the main determinants of risk variability. These findings highlight the importance of probabilistic risk assessment and continuous monitoring to protect vulnerable populations, particularly children, from long-term fluoride exposure.