Objective To investigate the effect of different levels of fluoride exposure on liver and renal function parameters.

Methods The population-based prevalence study was conducted with a total of 836 adults randomly selected from the agriculture-related areas in Tianjin, China for questionnaire survey, physical examination, and collection of random urine and fasting blood samples. The national standardized ion selective electrode method was used to measure the concentration of water fluoride, and an automatic biochemical analyzer was used to measure blood glucose, blood lipids, and liver and renal function parameters. The linear regression model, the restricted cubic spline model, and the binary logistic regression model were used to investigate the association between fluoride exposure level and liver and renal function parameters.

Results After adjustment for related covariates (age, sex, education level, body mass index, waist circumference, annual per capital income of the family, frequencies of drinking and smoking, hypertension, hyperglycemia, and dyslipidemia), the linear regression model analysis showed that water fluorine intake was negatively correlated with serum albumin (β=-15.36, P=0.011), and the degree of dental fluorosis was negatively correlated with estimated glomerular filtration rate (β=-2.33, P=0.013) and was positively correlated with serum total bilirubin (β=3.88, P=0.015); the restricted cubic spline model analysis showed a linear dose-response relationship between the degree of dental fluorosis and renal insufficiency (P=0.009, P_non-linear=0.579); the logistic regression analysis showed that a relatively high level of fluoride exposure (water fluoride concentration or the prevalence of dental fluorosis) was associated with abnormal renal function (or renal insufficiency) (P=0.015, P=0.004). No association was observed between the different levels of fluoride exposure and the other liver and renal parameters examined in this study.

Conclusion Long-term fluoride exposure in areas with a high level of fluoride may cause changes in liver and renal function parameters in adults and exert an adverse effect on liver and renal function, especially renal function.