Children with higher levels of blood fluoride were found to have decrased kidney and liver function. The kidneys and liver are said to accumulate more fluoride over time than any organ system in the body which would provide an explanation why these organs would be more vulnerable to fluoride's toxic effects. Fluoride water levels were all below 1 ppm which is below the WHO guidelines of 1.5 ppm. Researchers stated, "Higher plasma fluoride concentrations were associated with changes in kidney and liver related parameters. Most notably, a 1 umol/L increase in plasma fluoride was associated with a 10.36 mL/min/1.73 m2 lower eGFR." (With eGFR representing the kidney's ability to remove waste).
Background:
Hepato and nephrotoxicity of fluoride have been demonstrated in animals, but few studies have examined potential effects in humans. This population-based study examines the relationship between chronic low-level fluoride exposure and kidney and liver function among United States (U.S.) adolescents. This study aimed to evaluate whether greater fluoride exposure is associated with altered kidney and liver parameters among U.S. youth.
Methods:
This cross-sectional study utilized data from the National Health and Nutrition Examination Survey (2013-2016). We analyzed data from 1,983 and 1,742 adolescents who had plasma and water fluoride measures respectively and did not have kidney disease. Fluoride was measured in plasma and household tap water. Kidney parameters included estimated glomerular filtration rate (calculated by the original Schwartz formula), serum uric acid, and the urinary albumin creatinine ratio. Liver parameters were assessed in serum and included alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, blood urea nitrogen, gamma glutamate transferase, and albumin. Survey-weighted linear regression examined relationships between fluoride exposure and kidney and liver parameters after covariate adjustment. A Holm-Bonferroni correction accounted for multiple comparisons.
Results:
The average age of adolescents was 15.4 years. Median water and plasma fluoride concentrations were 0.48 mg/L and 0.33 μmol/L respectively. A 1 umol/L increase in plasma fluoride was associated with a 10.36 mL/min/1.73 m2 lower estimated glomerular filtration rate - a 0.29 mg/dL higher serum uric acid concentration and a 1.29 mg/dL lower blood urea nitrogen concentration. A 1.0 mg/L increase in water fluoride was associated with a 0.93 mg/dL lower blood urea nitrogen concentration.
Conclusions:
Fluoride exposure may contribute to complex changes in kidney and liver related parameters among U.S. adolescents. As the study is cross-sectional, reverse causality cannot be ruled out; therefore, altered kidney and/or liver function may impact bodily fluoride absorption and metabolic processes.