[Fluoride content in rural drinking water in Shaanxi Province during 2008-2018]

To understand the fluoride index of drinking water quality and its trend in rural areas of Shaanxi Province since 2008, to evaluate the effect of water improvement on reducing fluoride.

In 2008-2018, rural drinking water monitoring points were set up in the jurisdiction of the agriculture-related counties( districts) in Shaanxi Province. Water samples were collected in the April-June dry seasons and July-September wet seasons, and tested according to the Standard Test Method for Drinking Water( GB/T 5750-2006). Collected and sorted water quality monitoring information through the National Drinking Water Quality Monitoring Information System, according to the Sanitary Standards for Drinking Water( GB 5749-2006), the comparison between groups and linear trend analysis were carried out according to different annual, water period, water source type, water supply mode and region.

From 2008 to 2018, the overall compliance rate of fluoride in rural drinking water in Shaanxi Province was 93. 37%, the concentration of fluoride in water was in the range of0. 001-9. 880 mg/L, the median was 0. 370 mg/L, and the cumulative coverage of water quality fluoride exceeded the standard project was 3. 669 million. The difference of fluoride compliance rate in different years was statistically significant( χ~2= 120. 962, P<0. 001), and the fluoride compliance rate increased with the increase of the year( χ~2= 9. 241, P =0. 002), the fluoride compliance rate of surface water was higher than that of groundwater( χ~2= 1188. 563, P < 0. 001), there was a statistically significant difference in the compliance rate of fluoride in different water treatment processes in centralized water supply projects( χ~2= 2931. 231, P < 0. 001), the highest rate of fluoride in conventional treatment was 96. 63%( P < 0. 001), and the lowest disinfection rate was 84. 78%( P <0. 001). The distribution of drinking water sources in rural areas of Guanzhong and Northern Shaanxi was mainly groundwater, accounting for 88. 12% and 92. 25%, respectively, while Southern Shaanxi was dominated by surface water, accounting for69. 99%. There were significant differences in the fluoride compliance rates in Guanzhong region, Northern Shaanxi and Southern Shaanxi( χ~2= 1919. 335, P < 0. 001). Among them, the highest in Southern Shaanxi was 99. 84%( P < 0. 001), and the lowest in Northern Shaanxi was 89. 33%( P < 0. 001)( χ~2 SouthernShaanxi, Guanzhong= 1755. 724, χ~2 Southern Shaanxi, Northern Shaanxi= 2033. 8, χ~2 Northern Shaanxi, Guanzhong= 27. 535, P < 0. 001). The overall compliance rate of fluoride in water-reducing projects was 73. 80%, which cannot prove the trend of the overall compliance rate of fluoride in water-reducing projects with the year( χ~2= 3. 168, P = 0. 075).

While achieving high result in the prevention and control of high fluorine water in Shaanxi Province, it is necessary to continue to implement effective measures to reduce fluorine content in rural drinking water, and to ensure the safety of drinking water from the aspects of water supply and treatment technology.