Distribution Characteristics and Health Risk Assessment of Fluoride in Rural Drinking Water in a District of Fuyang, China

Objective To investigate the distribution characteristics, influencing factors and health risks of fluoride in rural drinking water in a district of Fuyang, China, in recent years.

Methods The monitoring data of rural drinking water quality in a district of Fuyang from 2015 to 2018 were collected through the National Drinking Water Quality Monitoring Information System, and the results of fluoride in water were evaluated according to Standards for Drinking Water Quality(GB 5749-2006). The Mann-Whitney U test and the Kruskal-Wallis H test were used for comparison of fluoride concentrations between two groups and among multiple groups, respectively. The Spearman rank correlation test was used to analyze the correlation between fluoride and other indicators of water. The health risk assessment model recommended by United States Environmental Protection Agency was used to evaluate the non-carcinogenic risk of fluoride in rural drinking water in this district.

Results The median (minimum, maximum) of fluoride concentration was 0.94 (0.09, 2.42) mg/L in 424 rural drinking water samples in this district from 2015 to 2018. The median of fluoride concentration in rural drinking water samples gradually decreased in this district from 2015 to 2018. The median of fluoride concentration in the samples of non-central water supply units was significantly lower than that in the samples of central water supply units and small central water supply units; the median of fluoride concentration in the samples of non-central water supply units was significantly lower than that in the samples of finished water and terminal water; the median of fluoride concentration in the samples of deep well water source was significantly higher than that in the samples of shallow well water source. There was a significant difference in fluoride concentration between different years, different water supply units, different water sample types and different water sources (P < 0.05). The Spearman rank correlation analysis showed that fluoride concentration in water was positively correlated with pH, sulfate, total dissolved solids, chloride concentration and arsenic concentration (r_s=0.108-0.508, P < 0.05) and was negatively correlated with total hardness, oxygen consumption and manganese concentration (r_s were -0.341, -0.235, -0.338, respectively, P < 0.01). The median (minimum, maximum) hazard quotient of non-carcinogenic risk of fluoride exposure through drinking water for 30 years was 0.39 (0.04, 1.01) in rural male residents, 0.34 (0.03, 0.86) in rural female residents, and 0.37 (0.04, 0.94) in rural adults.

Conclusion Fluoride is widely distributed in rural drinking water in this district, and there is a certain health risk in adult male residents in some areas with high water fluoride. The local government should continue to look for suitable low-fluoride water sources and strengthen the supervision, inspection, and management of water improvement and defluorination projects, so as to ensure the effective operation of water improvement and defluorination projects.