Non-carcinogenic health risk assessment of nitrate, nitrite, and fluoride in drinking water: evidence from Saveh, Central Iran

Elevated concentrations of nitrate, nitrite, and fluoride in drinking water are associated with significant non-carcinogenic health risks. As drinking water constitutes a major component of the human diet and an important source of inorganic contaminant exposure, this study aimed to characterize the chemical quality of drinking water and to assess its contribution to dietary intake and non-carcinogenic health risks across different age groups in Saveh, Central Iran. A total of 72 water samples were collected from 12 monitoring sites between 2023 and 2025 through biannual sampling. Nitrate concentrations ranged from 4.63 to 102 mg/L, with a mean value of approximately 29–38 mg/L across the study period, and 25% of samples exceeding the WHO guideline value of 50 mg/L. Fluoride concentrations ranged from 0.20 to 0.26 mg/L, remaining below the optimal range for dental health. Nitrite was undetectable in all samples. Health risk assessment revealed that the maximum nitrate Hazard Quotient (HQ) reached 3.21 in infants, while the Hazard Index (HI) exceeded unity in up to 33% of infant samples and 25% of child samples, indicating elevated risk in younger populations. Monte Carlo simulation identified daily water intake as the dominant contributor to HI variability. In general, nitrate contamination represents the primary non-carcinogenic health risk, particularly for infants, while insufficient fluoride may increase dental caries risk. These findings highlight the urgent need for improved water quality management and targeted nitrate mitigation strategies in the study area.