The fractional urinary fluoride excretion of adolescents and adults under customary fluoride intake conditions, in a community with 0.6-mg F/L in its drinking water.

Aims: To assess the fractional urinary fluoride excretion (FUFE) relative to the customary daily fluoride (F) ingestion in adolescents and adults aged 11-75 years, and to explore the influence that some metabolic variables, such as the F-dose (mg F/kg body weight), rate of urinary fluoride excretion, age and body weight, might have on FUFE values.

Design: The fluoride ingestion and urinary excretion of 92 volunteers aged 11-75 years, resident in Santiago, Chile, were measured. In Santiago, the water is fluoridated to a concentration of between 0.5 and 0.6 mg/l. Individual FUFE values were calculated as the ratio between the total amount of F excreted with the urine and the total amount of F ingested, over a 24-hour period.

Results: The average FUFE values did not differ significantly among adults (ANOVA; p > 0.31). The average 24-hour FUFE value for adults was 0.75; 95% C.I. = 0.70-0.80, while the corresponding value for adolescents was 0.35; 95% C.I. = 0.30-0.40. Individual FUFE values were fitted by a multiple regression model using the rate of F urinary excretion and the inverse of the F dose as significant predictors (R2 = 0.79).

Conclusions: Results obtained suggest that among adults residing in an area with an intermediate F-exposure, FUFE values do not depend on age. A relatively simple multiple regression model appears to explain 79% of the variability of the individually measured FUFE values. Further studies in areas with different F exposures are needed to refine the proposed model.