Concentration, spatial distribution, and health risk assessment of fluoride in rural drinking water resources, North Khorasan Province, Iran.

Presence of fluoride in drinking water resources is one of the most important challenges related to water management and health issues. This study aimed to monitor the fluoride concentration in rural areas of North Khorasan province, Iran. During a seven-year sampling period, the water quality of over 500 points was assessed annually, based on SPADNS colorimetric method. The geostatistical analyses and spatial distribution of fluoride were performed through global Moran's I index (spatial autocorrelation), and inverse distance weighting (IDW). In addition, the health impact probabilities of fluoride were evaluated via comparing concentrations with Iran national standard and the health risk assessment method recommended by EPA. According to the results, the measured concentrations of fluoride were in the range of 0–8.73 mg/L (average ± SD = 0.855 ± 0.458 mg/L). The lowest fluoride concentrations were determined in Esfarayen and Farouj counties (0.63 mg/L) and highest ones in Maneh Samalghan (0.9 mg/L). Moreover, Global Moran's I was calculated to be close to zero, indicating a random distribution of fluoride throughout the province. The average THQs for adult and children age groups were 4.94 and 3.61, respectively, which showed a high non-carcinogenic risk for both adult and children age groups. However, the concentration of fluoride in all studied water resources has not exceeded the standard and was in a good condition. Therefore, it is necessary to control the excessive concentrations, especially in areas with higher amounts. [ABSTRACT FROM AUTHOR]