BenchMark Dose of Urine Fluorine and Child Skeletal Flurosis

Objective: To identify the BenchMark Dose (BMD) of children urine fluorine in a coal-burning endemic fluorosis region and to investigate the association between urine fluorine level and child skeletal flurosis.

Setting: Fluorosis from in-door burning of coal is prevalent in Guizhou province of China. Child skeletal flurosis has greatly affected children's growth and development.

Methods: This is a case-control study. Students from five schools in a region with high usage of coal were selected as case group. Students in a school located in the area where residents use least coal were selected as control group. All students aged 7-16 years. The concentration of urine fluorine were measured and grouped into 7 levels. The means of urine fluorine concentration of the case- and control group were compared using ANOVA. For the case group, the association between urine fluorine level and clinical detection rate of skeletal fluorosis was determined using logistic regression.

Results: There is a significant difference for the urine fluorine concentrations between the case- and the control group (p<0.05). In the case group, there is a significant dose-response relationship between the urine fluorine level and the clinical detection rate of skeletal fluorosis (F= 65.71, p<0.001). In the case group, BMD is 1.83 mg/L, and the BenchMark Dose lower bound (BMDL) is 1.59 mg/L.

Conclusions: Children in the coal-burning region are at a significantly higher risk of skeletal fluorosis, reflected by higher urine fluorine concentration. Close monitoring of children's urine fluorine level is recommended with a BMDL of 1.59 ml/L.