Determining an upper reference value for the urinary fluoride-creatinine ratio in healthy children younger than 7 years

To reduce the risk of development of dental fluorosis, total fluoride intake in infancy and early childhood should be monitored and examined for signs of excessive fluoride exposure. The urinary fluoride/creatinine ratio (UF/Cr) in a spot urine sample could be a useful systemic fluoride exposure monitoring tool; replacing 24h urine collection. However, there are no reference value for UF/Cr corresponding to excessive systemic fluoride exposure in children. In this study, we took 158 simultaneously collected total daily fluoride intake and excretion data in children <7 years from UK studies conducted by our team from 2002-2014. This study showed a strong positive linear relationship between total daily fluoride intake and UF/Cr, which suggests value in the use of a UF/Cr for estimation of fluoride intake in young children. This study has also established, for the first time, an upper reference value of a UF/Cr of 1.69 corresponding to excessive fluoride intake currently suggested as being >0.07 mg/kg bw/day.