Environment International ( IF 10.3 ) Pub Date : 2018-06-02 , DOI: 10.1016/j.envint.2018.05.042 Xingchen Yu , Jingwen Chen , Yonggang Li , Hongliang Liu , Changchun Hou , Qiang Zeng , Yushan Cui , Liang Zhao , Pei Li , Ziquan Zhou , Shuo Pang , Sha Tang , Kunming Tian , Qian Zhao , Lixin Dong , Chunyan Xu , Xiao Zhang , Shun Zhang , Li Liu , Aiguo Wang
Background
Excessive fluoride exposure is associated with adverse health outcomes, but little is known of the effects of moderately chronic fluoride exposure on children's health.
Objectives
We conducted a cross-sectional study to explore the health impact of moderately excessive fluoride in drinking water.
Methods
We recruited 2886 resident children, aged 7 to 13 years, randomly from endemic and non-endemic fluorosis areas in Tianjin, China. The fluoride levels in drinking water and urine were measured using the national standardized ion selective electrode method. We examined the dose-response effects of low-to-moderate fluoride exposure on dental fluorosis (DF) and intelligence quotient (IQ), and evaluated the potential relationships between DF grades and intelligence levels using piecewise linear regression and multiple logistic regression, respectively.
Results
The adjusted odds ratios (ORs) of DF were 2.24 (95% confidence interval [CI]: 2.02 to 2.48) for every 0.1 mg/L increment in the water fluoride concentration in the range of 0.80 to 1.50 mg/L, and 2.61 (95% CI: 2.32 to 2.93) for every 0.5 mg/L increment in the urinary fluoride level up to 1.80 mg/L. Every 0.5 mg/L increment in the water fluoride level was associated with a reduction of 4.29 in the IQ score (95% CI: −8.09 to −0.48) in the range of 3.40 to 3.90 mg/L, and a decreased probability of developing excellent intelligence (IQ ≥ 130, OR = 0.60, 95% CI: 0.47 to 0.77) in the range of 0.20–1.40 mg/L, respectively. Every 0.5 mg/L increment in the urinary fluoride level was related to a decrease of 2.67 in the IQ scores (95% CI: −4.67 to −0.68) between 1.60 mg/L to 2.50 mg/L. Excellent intelligence decreased by 51% in children with higher urinary fluoride, and by 30% with each degree increment of DF.
Conclusions
Our study suggests threshold and saturation effects of moderately excessive fluoride exposure on DF and intelligence loss in children, and a potential association between DF and the loss of excellent intelligence.