24-hour Urinary Fluoride Excretion in British Children Aged 6 Years

Objectives: To measure urinary excretion of fluoride in British children, aged 6 years, residing in optimally- (> 0.7 ppmF) (OF), suboptimally- (0.3-0.7 ppmF) (SF) - and non-fluoridated (<0.3 ppmF) (NF) areas.

Methods: 24-hour urine samples were collected from 33 children aged 6 years residing in OF (n=9), SF (n=9), or NF (n=15) areas. On three different occasions, drinking water samples were collected from each subject's home. Body weight was also measured. Urine and water samples were analysed in triplicate for fluoride concentration by the acid-diffusion method using an Orion 96-09 BN F ion-specific electrode with an Orion 720A potentiometer. Between area comparisons of 24-hour urinary fluoride excretion were made by analysis of variance.

Results: The mean fluoride concentrations of water supplies were 0.80, 0.50, and 0.03 mg/l, for OF, SF, and NF areas respectively. The mean age in the OF, SF and NF areas was 6.05, 6.01 and 6.03 years, respectively. The mean (± sd) volume of 24-hour urine was similar between areas: 459 (± 180), 517 (± 166) and 534 (± 142) ml in the OF, SF, and NF areas, respectively. The mean ± sd 24-hour urinary excretions were 0.29 (± 0.14) mg (0.013 mg/kg body wt), 0.24 (± 0.10) mg (0.011 mg/kg body wt), and 0.20 (± 0.11) mg (0.008 mg/kg body wt) in the OF, SF, and NF areas, respectively. There was no statistically significant difference between areas in either urine volume(p=0.65) or urinary fluoride excretion(p= 0.31).

Conclusion: Differences in fluoride concentration in drinking water below 1ppm are not reflected in 24-hour urinary fluoride excretion. Other factors such as diet and toothpaste may have more impact on the urinary fluoride excretion, in this age group.

Supported by grant from "The Borrow Foundation"