Assessing Nitrate and Fluoride Contaminants in Drinking Water and Their Health Risk of Rural Residents Living in a Semiarid Region of Northwest China

High levels of nitrate and fluoride in drinking water can affect human health. In the present study, statistical and correlation analyses were carried out to assess nitrate and fluoride contamination in groundwater in Zhongning area, Northwest China, where rural residents totally depend on groundwater for drinking. The associated health risks for different age groups (infants, children, adult female, and male) were assessed based on the USEPA model. Results show that NO3-N and F- concentrations in groundwater are in the ranges of 2.66-103 and 0.11-6.33 mg/L, respectively. Of the 50 samples, 30 and four samples have high NO3-N and F- levels exceeding the acceptable limits for drinking purpose recommended by the WHO (10 and 1.5 mg/L), respectively. Enrichment of nitrate contamination is primarily due to the human activities, and dissolution of fluorite is the primary source of fluoride in the groundwater. Correlation values of NO3-N and F- with other chemicals have further confirmed the sources of contaminant in groundwater. Infants are the most vulnerable groups through ingestion pathway. As per the obtained hazard index, majority of the samples (72 and 60 %) may pose adverse effects on infants and children, but the proportions are relatively lower for adult female and male (28 and 22 %). These finding suggest that there is an instant need to take ameliorative steps in this region to prevent the residents from nitrate and fluoride exposure through ingestion.