Association Between Osteoarthritis and Water Fluoride Among Tongyu Residents, China, 2019: a Case-Control of Population-Based Study

Fluoride is an environmental chemical that has adverse effects on articular cartilage, probably increasing osteoarthritis (OA) risk. However, this association still needs more epidemiological evidence to clarify. The aim of this study was to determine the relationships between chronic fluoride exposure and OA risk among the residents living in Tongyu County, China, 2019, with a frequency-matched case-control study (186 OA patients and 186 healthy participants). The results showed that urinary fluoride (UF) (2.73 ± 1.18 mg/L) was significantly higher in OA patients compared to the controls (2.35 ± 1.24 mg/L) (p < 0.002). After adjustment, the odds ratios (ORs) with 95% confidence intervals (95% CIs) between the OA risk and fluoride were calculated by the unconditional logistic regression. In full sample analysis, a 1 mg/L increase in UF level was associated with a 27% higher risk of OA (1.06-1.52, p = 0.008), and 4th quarter's participants were associated with higher risk when compared to 1st quarter (OR: 2.46, 95% CI: 1.34-4.57, p = 0.003). In stratified analysis, compared to 1st quarter, 4th quarter's participants were 4 times more likely to have OA (1.86-8.82, p < 0.001) in the non-obese group and 7.7 times more likely to have OA (2.58-25.05, p < 0.001) among adults ≤ 60 years. In conclusion, excessive exposure of water fluoride may increase OA risk, and could have more impact on the specific population such as non-obese, and adult aged ≤ 60 years.

Dopamine receptor D2 gene polymorphism, urine fluoride, and intelligence impairment of children in China: A school-based cross-sectional study

OBJECTIVE

We aimed to study the association of urine fluoride with intelligence quotient (IQ) in children with a careful consideration of up to 30 potential confounding factors as well as possible heterogeneity of the relation between urine fluoride levels and IQ scores across children with different dopamine receptor-2 (DRD2) Taq 1A genotypes (CC, CT, and TT).

METHODS

A school-based cross-sectional study design was applied. A total of 323 children (2014-2015, 7-12 years old) were enrolled from four schools in both historical endemic and non-endemic areas of fluorosis in Tianjin of China using a cluster sampling method. Urine fluoride levels and age-specific IQ scores in children were measured at the enrollment. Polymerase chain reaction-restriction fragment length polymorphism methods were used to genotype DRD2 Taq 1A polymorphism with genomic DNA isolated from whole blood collected at the enrollment. Multiple linear regression models were applied to evaluate the relationship between urine fluoride levels and IQ scores overall and within the DRD2 Taq 1A SNP = CC/CT and TT subgroups. Model robustness was tested through bootstrap, sensitivity analysis, and cross-validation techniques. A safety threshold of urine fluoride levels for IQ impairment was determined in the subgroup TT.

RESULTS

In overall participants, the DRD2 Taq 1A polymorphism itself was not related to IQ scores in children who had a high level of urine fluoride. In the CC/CT subgroup, urine fluoride levels and IQ scores in children were unrelated (adjusted β (95% confidence interval (CI)) = - 1.59 (- 4.24, 1.05), p = 0.236). Among the participants carrying the TT genotype, there was a strong and robust negative linear relationship between log-urine fluoride and IQ scores in children (adjusted β (95% CI) = - 12.31 (- 18.69, - 5.94), p < 0.001). Urine fluoride levels had a stronger association with IQ in children carrying the TT genotype (adjusted β = - 12.31, bootstrapped standard error (SE) = 1.28), compared to that in overall participants (adjusted β = - 2.47, bootstrapped SE = 3.75) (Z = 2.483 and bootstrapped p = 0.007). The safety threshold of urine fluoride levels in the subgroup TT was 1.73 mg/L (95% CI = (1.51, 1.97) (mg/L)).

CONCLUSIONS

There is heterogeneity in the relation between urine fluoride and IQ across children carrying different DRD2 Taq 1A genotypes. Large-scale epidemiological studies are needed to confirm our findings.

"Borderline" fluorotic region in Serbia: correlations among fluoride in drinking water, biomarkers of exposure and dental fluorosis in schoolchildren

This study explores relation between dental fluorosis occurrence in schoolchildren, residents of Ritopek, a small local community near Belgrade, and fluoride exposure via drinking water. Additionally, fluoride levels were determined in children's urine and hair samples, and efforts were made to correlate them with dental fluorosis. Dental fluorosis and caries prevalence were examined in a total of 52 schoolchildren aged 7-15 years (29 boys and 23 girls). Fluoride levels in three types of samples were analyzed using composite fluoride ion-selective electrode. Results showed high prevalence of dental fluorosis (34.6 %) and low prevalence of dental caries (23.1 %, mean DMFT 0.96) among children exposed to wide range of water fluoride levels (0.11-4.14 mg/L, n = 27). About 11 % of water samples exceeded 1.5 mg/L, a drinking-water quality guideline value for fluoride given by the World Health Organization (2006). Fluoride levels in urine and hair samples ranged between 0.07-2.59 (n = 48) and 1.07-19.83 mg/L (n = 33), respectively. Severity of dental fluorosis was positively and linearly correlated with fluoride levels in drinking water (r = 0.79). Fluoride levels in urine and hair were strongly and positively correlated with levels in drinking water (r = 0.92 and 0.94, respectively). Fluoride levels in hair samples appeared to be a potentially promising biomarker of fluoride intake via drinking water on one hand, and severity of dental fluorosis on the other hand. Based on community fluorosis index value of 0.58, dental fluorosis revealed in Ritopek can be considered as "borderline" public health issue.

Dental fluorosis and urinary fluoride concentration as a reflection of fluoride exposure and its impact on IQ level and BMI of children of Laxmisagar, Simlapal Block of Bankura District, W.B., India

There has been growing public concern about intellectual performance of children at high levels of fluoride exposure. A cross-sectional study was conducted in Simlapal Block of Bankura District, West Bengal, to find out the relationship between fluoride (F) exposure as exposure dose (ED) with dental fluorosis (DF), urinary fluoride concentration (UF), intelligence quotient (IQ) and body mass index (BMI). Fifty groundwater samples were collected from the target area. One hundred forty-nine children belonging to age group 6 to 18 years were considered for this study. Experimental results reveal that mean F(-) concentration of that area is 2.11 mg/L (±SD 1.64). On the basis of F concentration in groundwater and water consumption pattern, ED was calculated to explore the impact of F(-) on DF, UF, IQ, and BMI. Paired t test results suggest that exposure rate of F does not show any significant differences (<0.05) among the children of 12 different places. As a result of F exposure, DF cases are mostly found in the order of moderate > severe > mild > very mild > questionable > normal conditions. The highest UF concentration was recorded as 17 mg/L, but the status of DF in the affected children was recorded as moderate. The results also reveal that ED has a positive correlation with DF (r = 0.299, P < 0.01) and UF (r = 0.513, P < 0.01) and a negative correlation with IQ (r = -0.343, P < 0.01) along with BMI (r = 0.083, non-significant). Therefore, from this study, it may be concluded that UF and DF concentration could act as a biomarker of fluoride toxicity.