Human health risk assessment for fluoride and nitrate contamination in drinking water of municipal and rural areas of Zahedan, Iran

Increased fluoride and nitrate concentration in water resources can affect consumers' health adversely. The objective of this study is to health risk assessment of fluoride and nitrate in the drinking water of municipal and rural areas of Zahedan using probabilistic approaches. For this purpose, 347 water samples were collected from both urban and rural areas of this province. After the chemical analysis of the samples, a health risk assessment was conducted using the USEPA model, and a sensitivity analysis was performed by Monte Carlo software. The average concentration of nitrate in rural and municipal areas drinking water was 31.89 mg/L and 40.87 mg/L, respectively. Fluoride concentration in rural samples was 2.13 mg/L while municipal samples had 1.28 mg/L. 14.53% and 24.12% of rural and urban areas exceeded NO₃⁻ limits, respectively. Rural samples had higher F- concentrations than WHO standards. CDI values for fluoride and nitrate in municipal areas were 0.04 and 1.15 mg/kg/day, for adults and 0.09 and 2.82 mg/kg/day, for children. The corresponding values for rural areas were 0.06, 0.9, 0.15, and 2.2 mg/kg/day. The HQ for nitrate in children was between 0 and 5.2 in children, with an average of 1.71. These values were registered to be 0–3.85 and 1.26, respectively, in the adult group. Also, the average value of HQ fluoride in children is much higher than that of adults, with values of 2.45 and 1.47 in rural and urban areas, respectively, both exceeding 1. The results indicate a possibility non-carcinogenic risk of nitrate and fluoride, particularly for children in these areas, is significant. Therefore, it is necessary to pay special attention to improving the quality of drinking water in this province.