Threshold effects of moderately excessive fluoride exposure on children’s health: A potential association between dental fluorosis and loss of excellent intelligence.

Abstract

Highlights

• Childhood fluoride exposure was inversely associated with dental health and IQ.
• Threshold and saturation effects for aforementioned associations existed.
• Moderate fluoride exposure was mainly related to excellent intelligence loss.
• Dental fluorosis may be useful to reflect excellent intelligence loss.

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.

Section snippets

Study design and population

A village-based cross-sectional study was conducted in 2015 in the rural areas of Tianjin City, China. According to the annual surveillance data from the local Center for Disease Control and Prevention (CDC), the whole district was divided into historical high fluoride areas and normal fluoride areas. The fluoride concentrations in these areas have maintained at stable levels over the past decade. None of the study sites was in the areas endemic for iodine deficiency disorders, or exposed to…

Characteristics of the participants

A total of 2886 school children, aged 7 to 13?years, were recruited. We assigned the participants into the normal-fluoride exposure group or high-fluoride exposure group according to the cut-off water fluoride level of 1.0?mg/L. The characteristics of all the participants are summarized in Table 1. The distributions of age and sex were comparable between the two groups. The BMI of the participants in the high-fluoride exposure group tended to be lower than that in the normal-fluoride exposure…

Discussion

This large population-based study revealed that the dose-response relationships of fluoride exposure with DF and IQ were piecewise-linear, with threshold and saturation effects, and exposure to moderately excessive fluoride was predominantly related to the loss of excellent intelligence. Consistently, with every increment in the DF grade, the OR for excellent intelligence scores declined by 30%. Our findings suggest that excessive fluoride exposure, even at a moderate level, results in impaired…

Conclusions

In conclusion, chronic exposure to excessive fluoride, even at a moderate level, was inversely associated with children’s dental health and intelligence scores, especially excellent intelligence performance, with threshold and saturation effects observed in the dose-response relationships. Additionally, DF severity is positively associated with the loss of high intelligence, and may be useful for the identification of individuals with the loss of excellent intelligence. Thus, it is important to…

ABSTRACT ONLINE AT https://www.sciencedirect.com/science/article/abs/pii/S016041201830480X
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