Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada

Protective effects of anthocyanins on the nervous system injury caused by fluoride-induced endoplasmic reticulum stress in rats

Long-term fluoride exposure can produce neurotoxicity. Anthocyanins, as antioxidants, have a certain protective effect in nerve damage. This study aimed to investigate the protective role of anthocyanins in fluoride-induced neurological damage due to endoplasmic reticulum stress (ERS). Using a fluoride-exposed Wistar rat model, we assessed learning memory capacity and pathologic and ultrastructural injury. The level of oxidative stress (OS) in vivo was detected by colorimetric method, the level of ERS was analyzed by immunohistochemistry, and the apoptosis of neuronal cells was observed by TUNEL staining. The results showed that fluoride exposure could decrease the learning and memory ability in rats, and led to histopathological and ultrastructural damage in the hippocampal CA1, CA3 and cortical regions. Fluoride exposure-induced OS in vivo, which further activates ERS, which was manifested by increased levels of ERS-related proteins GRP78, Caspase 12, and Caspase 3 in hippocampal CA1, CA3, and cortical regions, and eventually led to a significant increase in neuronal apoptosis rate. Notably, after anthocyanins treatment, pathological and ultrastructural damage was restored, the level of OS and ERS were significantly restored, and the apoptosis rate of neuronal cells was significantly reduced. In summary, as nutritional interventions, anthocyanins exert a protective role in fluoride-induced neurological injury.

Effects of low concentration of fluoride exposure during fetal on behavior and neurotransmitters in adult mice

Fluoride (F) naturally occurs in water in China and India, and in excess, can cause skeletal fluorosis and mottled teeth. Chronic exposure to F during gestation can affect the development of the brain, reducing intelligence quotient and inducing autism spectrum disorder-like behavior. In the present study, it was aimed to clarify the effects of chronic exposure to low concentrations of F in utero on brain function. The behavior was assessed, the levels of brain neurotransmitters were measured in mice and their relationships were analyzed. ICR mice consumed water containing sodium fluoride (F concentrations: 0, 15, or 30 ppm) from 3 weeks of age until the weaning of their pups (F1). The pups then consumed water containing the same concentration of F as their parents from weaning. At 8-weeks old, the F1 mice underwent behavioral testing using the Y-maze, elevated plus maze, Barnes maze (BM) and open-field test (OFT). At 10 weeks of age, they were euthanized, their brains were collected, and the levels of neurotransmitters were measured. Grooming events in the OFT were more frequent in F-exposed groups than in the control group, indicating that F exposure causes anxiety-like behavior. In the BM, the time taken to reach the escape box and the number of errors were higher during the training and test, suggesting spatial memory impairment. Cerebellar glutamate (Glu) concentrations were significantly lower in the F-exposed groups than in the control group. Low Glu concentration was associated with greater grooming frequency in the OFT, lower mean speed and more errors in the BM, and a delay in reaching the escape box. In the F-exposed groups, the midbrain noradrenaline concentrations were significantly lower and the number of errors in the BM was larger than in controls. Thus, F-exposed mice showed poorer spatial memory and differences in the levels of neurotransmitter, suggesting that F is an environmental contributor to disease.

Sustainable Fluoride Determination in Selected Infant Juices Available on the Serbian Market: Health Risk Assessment

Increased exposure to fluoride in food and beverages become a global concern in the last few decades. Infant juices and food, besides breast milk, are the main sources of fluoride intake throughout infancy. Monitoring fluoride levels in such formulations is crucial to ensure the youngest consumers' safety and optimal health. This study aimed to determine the fluoride of selected infant juices from four different producers available on the Serbian market, using fluoride ion-selective electrode. The fluoride content varies between 0.0845 and 0.2810 mg/L, which is below acceptable level (0.7 mg/L). The health risk assessment for children 6 to 48 months of age associated with fluoride in infant juices was evaluated as a non-carcinogenic risk based on estimated daily intake according to USEPA guidelines, including the HQ index. All calculated HQs are less than 1, suggesting no adverse effect after exposure to the fluorides via investigated juices. Since children, especially infants, are highly vulnerable to the harmful effects of fluoride, it is essential to monitor all sources that could be critical in fluorosis development. It is important to highlight fluoride as a toxic element and enforce stricter controls on infant feeding, emphasizing the urgency and importance of this matter.

Unraveling the role of abnormal AMPK and CRMP-2 phosphorylation in developmental fluoride neurotoxicity: Implications for synaptic damage and neurological disorders

Excessive fluoride exposure can be neurotoxic, although the exact mechanism remains unknown. This study aimed to investigate the neurotoxicity of continuous sodium fluoride exposure in offspring rats, focusing on the potential effects of fluoride exposure on hippocampal synaptic function and the role of AMPK and CRMP-2 in synaptic damage. We established an SD rat model of fluoride exposure (25, 50, and 100 mg/L NaF) and found that fluoride exposure damaged the learning and memory ability of F1 generation rats and caused ultrastructural changes in the hippocampus. Additionally, after the proteomic and phosphoproteomic analysis of rat hippocampal tissues, the Gene Ontology analysis revealed that sodium fluoride was involved in the enrichment of neuronal differentiation, synaptic signaling, and cytoskeleton-related biological processes. The Kyoto Encyclopedia of Genes and Genomes analysis showed that differential genes were enriched in synapse-related signaling pathways. Thus, we screened three differentially expressed proteins related to synaptic function for validation. The Western blotting analysis showed that AMPK and CRMP-2 were hyperphosphorylated in the hippocampus of fluoride-exposed rats. Our study found that abnormal AMPK and CRMP-2 phosphorylation leads to synaptic damage. This may be an important cause of memory impairment in fluorosis, offering new insights into the mechanism of fluoride-induced neurotoxicity.

Tooth decay prevention and neurodevelopmental disorder risk following childhood fluoride exposure

BACKGROUND

The Centers for Disease Control and Prevention (CDC) reports that water fluoridation is among the ten greatest public health achievements of the 20th Century. Tooth decay (TD) prevention and neurodevelopmental disorder (ND) risk were assessed in relation to childhood water fluoridation exposure.

METHODS

This longitudinal cohort study examined the Independent Healthcare Research Database (IHRD) composed of prospectively collected healthcare data from the Florida Medicaid system for the period 1990-2012, using logistic and frequency statistical modeling (with adjustment for covariates). A cohort of 73,254 children continuously enrolled for their first 10 years of life was examined. The yearly percentage of persons in Florida receiving fluoridated water exposure from community water systems was examined by county. The number of children diagnosed with TD, autism spectrum disorder (ASD), attention deficit-hyperactivity disorder (ADHD), intellectual disability (ID), and specific delays in development (SDD) was evaluated.

RESULTS

Fluoride exposure in the year of birth, statistically significantly and dose-dependently, slightly reduced the risk of TD, and, separately, slightly increased the risk of ASD, ADHD, ID, and SDD. During the first 10 years of life, children who were fluoride-exposed as compared to unexposed were at significantly lower risk for TD, and, separately, at significantly greater risk for ASD, ID, and SDD.

CONCLUSIONS

Findings from the present study, coupled with previous studies, suggest new risk/benefit analyses of water fluoridation should be undertaken.

Maternal Urinary Fluoride Levels of a Large Pregnancy Cohort in the United States: Findings from the ADORE Study

BACKGROUND

Emerging evidence has suggested negative associations between maternal urinary fluoride adjusted for specific gravity (MUFsg) and offspring intelligence quotient (IQ). Two prior studies report the MUFsg of pregnant women in the US, both in California, and more information is needed on population levels of MUFsg.

OBJECTIVES

The primary objective was to measure MUFsg in a large pregnancy cohort of women recruited from health departments and academic hospitals in Ohio and Kansas. A secondary objective was to compare associations between water fluoridation level and estimated fluoride intake from tap water and MUFsg.

METHODS

Pregnant women (n = 965 ) from the ADORE (Assessment of DHA on Reducing Early Preterm Birth) cohort provided a urine sample and dietary assessment at enrollment between 14 and 20 wk gestation. MUFsg was measured by fluoride-sensitive electrode and corrected for specific gravity. Water fluoridation levels were obtained for public water systems (PWS), matched to participant residence and multiplied by their tap water intake from dietary assessment. The association between MUFsg and water fluoridation level was estimated using a generalized linear model with gamma distribution and log link.

RESULTS

MUFsg (median: 1.0 mg / L ; Q1, Q3: 0.6, 1.5) was correlated with PWS fluoridation (r s = 0.30 ; p < 0.01 ) and self-reported tap water consumption (r s = 0.29 ; p < 0.01 ). For 87% of the cohort, MUFsg was above the 0.45 mg / L safety benchmark for pregnancy proposed in a previous study. Similarly, 76.7% lived in areas with PWS fluoridation ≥ 0.7 mg / L . The median MUFsg (1.0 mg / L ; Q1, Q3: 0.7, 1.5) of those living in areas with a PWS fluoridation level ≥ 0.7 mg / L was higher than the median MUFsg (0.8 mg / L ; Q1, Q3: 0.5, 1.2) of women living in areas with PWS fluoridation < 0.7 mg / L (p < 0.01 ).

DISCUSSION

MUFsg in this population of midwestern US women exceeds the safety benchmark for pregnancy. While we cannot account for all sources of fluoride, MUFsg was correlated to PWS fluoridation. Because so many exceeded the safety benchmark for MUFsg, there is a need for MUFsg evaluation in other US regions, especially where the PWS fluoridation exceeds US Department of Health and Human Services recommendations (≥ 0.7 mg / L ). https://doi.org/10.1289/EHP14711.

Combining Network Pharmacology and Experimental Verification to Ascertain the Mechanism of Action of Asparagus officinalis Against the Brain Damage Caused by Fluorosis

Asparagus officinalis (ASP) has antioxidation, anti-inflammatory, antiaging, and immune system-enhancing effects. We explored the preventive and therapeutic consequences of ASP on the brain damage elicited by fluorosis through network pharmacology and in vivo experimental validation. We ascertained the pharmaceutically active ingredients and drug targets of ASP from the Traditional Chinese Medicine Systems Pharmacology database, predicted the disease targets of fluorosis-induced brain injury using GeneCards and Online Mendelian Inheritance in Man databases, obtained target protein-protein interaction networks in the Search Tool for the Retrieval of Interacting Genes/Proteins database, used Cytoscape to obtain key targets and active ingredients, and conducted enrichment analyses of key targets in the Database for Annotation, Visualization and Integrated Discovery. Enrichment analyses showed that "mitogen-activated protein kinase" (MAPK), "phosphoinositide 3-kinase/protein kinase B" (PI3K-Akt), "nuclear factor-kappa B" (NF-κB), and the "neurotrophin signaling pathway" were the most enriched biological processes and signaling pathways. ASP could alleviate fluorosis-based injury, improve brain-tissue damage, increase urinary fluoride content, and improve oxidation levels and inflammatory-factor levels in the body. ASP could also reduce dental fluorosis, bone damage, fluoride concentrations in blood and bone, and accumulation of lipid peroxide. Upon ASP treatment, expression of silent information regulator (SIRT)1, brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B (TrkB), MAPK, NF-κB, PI3K, Akt, and B-cell lymphoma-2 in rat brain tissue increased gradually, whereas that of Bax, caspase-3, and p53 decreased gradually. We demonstrated that ASP could regulate the brain damage caused by fluorosis through the SIRT1/BDNF/TrkB signaling pathway, and reported the possible part played by ASP in preventing and treating fluorosis.

Prenatal and Childhood Exposure to Fluoride and Cognitive Development: Findings from the Longitudinal MINIMat Cohort in Rural Bangladesh

BACKGROUND

There are indications that fluoride exposure considered to be beneficial for dental health may not be safe from a neurodevelopmental perspective.

OBJECTIVE

We assessed the impact of prenatal and childhood fluoride exposure on cognitive abilities at 5 and 10 years of age.

METHODS

We studied 500 mother-child pairs from the MINIMat (Maternal and Infant Nutrition Interventions in Matlab) birth cohort in rural Bangladesh. Urinary fluoride concentrations were measured in the pregnant women at gestational week 8 and in their children at 5 and 10 years of age using an ion-selective electrode and adjusting for specific gravity. Cognitive abilities were assessed using the Wechsler Preschool and Primary Scale for Intelligence, Third Edition, and the Wechsler Intelligence Scale, Fourth Edition, at 5 and 10 years of age, respectively. Associations of urinary fluoride concentrations (log 2 -transformed) with cognitive abilities (raw scores) were assessed with multivariable-adjusted linear or spline regression models. Water fluoride concentrations at the time of the follow-up of the children at 10 years of age were also measured.

RESULTS

Maternal urinary fluoride concentrations (median: 0.63 mg / L , 5th-95th percentiles: 0.26 - 1.41 mg / L ) were inversely associated with full-scale raw scores at 5 and 10 years [B (95% confidence interval): - 2.8 (- 5.1 , - 0.6 ) and - 4.9 (- 8.0 , - 1.8 ), respectively, by exposure doubling]. In cross-sectional analysis at 10 years, child urinary fluoride (overall median: 0.66 mg / L , 5th-95th percentiles: 0.34 - 1.26 mg / L ) above - 0.47 on the log 2 -scale (corresponding to 0.72 mg / L ) was inversely associated with full-scale raw scores [B (95% confidence interval): - 12.1 (- 21.2 , - 3.0 )]. The association at 5 years of age was also negative but nonsignificant. For both prenatal and childhood exposure, associations were most noticeable with perceptual reasoning, but also verbal scores. The estimate for the association between urinary fluoride at 10 years of age and perceptual reasoning became 18% lower after adjustment for prenatal exposure. Inconsistent sex-specific differences were observed.

CONCLUSION

Urinary fluoride concentrations measured prenatally and during childhood (child urinary fluoride concentrations above - 0.47 on the log 2 scale, corresponding to 0.72 mg / L ) were associated with lower cognitive abilities, especially perceptual reasoning and verbal abilities, in Bangladeshi children. https://doi.org/10.1289/EHP14534.

Dose-dependent developmental fluoride exposure leads to neurotoxicity and impairs excitatory synapse development

Developmental fluoride exposure has been implicated in cognitive deficits and neurotoxicity, yet the mechanisms underlying these effects remain unclear. Here, we investigated the dose- and time-dependent impacts of sodium fluoride (NaF) on neuronal morphology, viability, oxidative stress, and synaptic function using both in vitro and in vivo mouse models. Cultured primary embryonic mouse cortical neurons were exposed to varying concentrations of NaF (0-200 μg/ml). Acute exposure led to neuronal swelling at higher concentrations (≥ 50 μg/ml), while prolonged exposure reduced neuronal viability. Notably, NaF dose-dependently elevated reactive oxygen species (ROS) production, implicating oxidative stress as a key mechanism of fluoride-induced neurotoxicity. Synaptic development was also impaired, as evidenced by reduced density and co-localization of excitatory synapse markers with prolonged 2 μg/ml NaF exposure. To extend these in vitro findings, pregnant mice were exposed to 50 mg/L NaF in drinking water, and offspring brain functions were evaluated postnatally. Whole-cell patch-clamp recordings in layer V pyramidal neurons in the prefrontal cortex revealed reduced frequency and amplitude of miniature excitatory post-synaptic currents (mEPSCs), indicating impaired synaptic function. Morphological analysis showed decreased dendritic spine density and head diameter. These findings suggest that fluoride exposure during critical period of brain development disrupts synaptic integrity and function through excitatory synapse impairments.

First-trimester nutrition insights from the United Arab Emirate Birth Cohort Study (UAE-BCS): assessment of dietary intake, micronutrient profiles, and folic acid supplementation in Emirati Women

Maternal health and nutrition in early pregnancy play a vital role in the growth and development of the foetus. During this time, macro and micronutrients contribute to nutritional programming, which helps form the foundations of the foetus's life course health outcomes. This study aimed to investigate dietary habits, macro and micronutrient intake, micronutrient status, and folic acid supplement adherence among Emirati pregnant women in their first trimester. Data were collected according to the UAE-BCS study protocol, which was set up to investigate maternal nutrition, health, child growth, and developmental outcomes within the first 1000 days. Pregnant Emirati women with singleton pregnancies within their first trimester of pregnancy (between 8 and 12 weeks of gestation) were enrolled. The 24-hour food recall method was administered to collect dietary intake. The maternal mean average age was 29 years. Participants had high adherence to supplementation during pregnancy compared to preconception. The mean energy intake was 1345kcal, and 56% of participants consumed saturated fats above the acceptable macronutrient distribution ranges (AMDR), while 94% consumed below AMDR for total fibre. The consumption of micronutrients was below the recommended dietary allowance (RDA). Biochemical results show a high prevalence of low haemoglobin (74%) and deficiencies in vitamin D (39%) and vitamin E (96%). There is a need for research into dietary patterns and influences in pregnant women in the UAE. Furthermore, investigations of knowledge practices and attitudes towards supplementation and the factors contributing to folic acid supplement use are needed to inform government strategies and interventions.

Fluoride Exposure and Children's IQ Scores: A Systematic Review and Meta-Analysis

Importance

Previous meta-analyses suggest that fluoride exposure is adversely associated with children's IQ scores. An individual's total fluoride exposure comes primarily from fluoride in drinking water, food, and beverages.

Objective

To perform a systematic review and meta-analysis of epidemiological studies investigating children's IQ scores and prenatal or postnatal fluoride exposure.

Data Sources

BIOSIS, Embase, PsycInfo, PubMed, Scopus, Web of Science, CNKI, and Wanfang, searched through October 2023.

Study Selection

Studies reporting children's IQ scores, fluoride exposure, and effect sizes.

Data Extraction and Synthesis

Data were extracted into the Health Assessment Workplace Collaborative system. Study quality was evaluated using the OHAT risk-of-bias tool. Pooled standardized mean differences (SMDs) and regression coefficients were estimated with random-effects models.

Main Outcomes and Measures

Children's IQ scores.

Results

Of 74 studies included (64 cross-sectional and 10 cohort studies), most were conducted in China (n = 45); other locations included Canada (n = 3), Denmark (n = 1), India (n = 12), Iran (n = 4), Mexico (n = 4), New Zealand (n = 1), Pakistan (n = 2), Spain (n = 1), and Taiwan (n = 1). Fifty-two studies were rated high risk of bias and 22 were rated low risk of bias. Sixty-four studies reported inverse associations between fluoride exposure measures and children's IQ. Analysis of 59 studies with group-level measures of fluoride in drinking water, dental fluorosis, or other measures of fluoride exposure (47 high risk of bias, 12 low risk of bias; n = 20 932 children) showed an inverse association between fluoride exposure and IQ (pooled SMD, -0.45; 95% CI, -0.57 to -0.33; P < .001). In 31 studies reporting fluoride measured in drinking water, a dose-response association was found between exposed and reference groups (SMD, -0.15; 95% CI, -0.20 to -0.11; P < .001), and associations remained inverse when exposed groups were restricted to less than 4 mg/L and less than 2 mg/L; however, the association was null at less than 1.5 mg/L. In analyses restricted to low risk-of-bias studies, the association remained inverse when exposure was restricted to less than 4 mg/L, less than 2 mg/L, and less than 1.5 mg/L fluoride in drinking water. In 20 studies reporting fluoride measured in urine, there was an inverse dose-response association (SMD, -0.15; 95% CI, -0.23 to -0.07; P < .001). Associations remained inverse when exposed groups were restricted to less than 4 mg/L, less than 2 mg/L, and less than 1.5 mg/L fluoride in urine; the associations held in analyses restricted to the low risk-of-bias studies. Analysis of 13 studies with individual-level measures found an IQ score decrease of 1.63 points (95% CI, -2.33 to -0.93; P < .001) per 1-mg/L increase in urinary fluoride. Among low risk-of-bias studies, there was an IQ score decrease of 1.14 points (95% CI, -1.68 to -0.61; P < .001). Associations remained inverse when stratified by risk of bias, sex, age, outcome assessment type, country, exposure timing, and exposure matrix.

Conclusions and Relevance

This systematic review and meta-analysis found inverse associations and a dose-response association between fluoride measurements in urine and drinking water and children's IQ across the large multicountry epidemiological literature. There were limited data and uncertainty in the dose-response association between fluoride exposure and children's IQ when fluoride exposure was estimated by drinking water alone at concentrations less than 1.5 mg/L. These findings may inform future comprehensive public health risk-benefit assessments of fluoride exposures.

Early Childhood Exposures to Fluorides and Cognitive Neurodevelopment: A Population-Based Longitudinal Study

It is important to maintain confidence in the risk and benefit balance of major caries-preventive programs using fluoride. The ongoing debate about potential effects of early-life exposures to fluoride on cognitive neurodevelopment requires high-quality scientific evidence. This study aimed to investigate the potential effects of fluoride exposure on cognitive neurodevelopment assessed with the Wechsler Adult Intelligence Scale 4th edition (WAIS-IV) in an Australian population-based sample. The sample was selected from the National Child Oral Health Study (NCOHS) 2012-2014. NCOHS collected data on socioeconomic factors, oral health behaviors, and residential history to estimate percentage lifetime exposure to fluoridated water during the first 5 y of life (%LEFW). NCOHS children were also examined by trained and calibrated examiners to assess dental fluorosis (a reliable and valid individual biomarker of total fluoride intake during early childhood). The sample was followed up in 2022-2023 to collect data on cognitive neurodevelopment (intelligence quotient [IQ]) using the WAIS-IV, which was administered by trained and calibrated qualified psychologists. Multivariable regression models were generated to investigate associations between the 2 exposure measurements (%LEFW and dental fluorosis) with full-scale IQ (FSIQ) scores, controlling for important confounding effects. Hypotheses of noninferiority were also tested, contrasting different levels of exposure to fluoride. Some 357 participants aged 16 to 26 y completed the WAIS-IV, with a mean FSIQ score of 109.2 (95% confidence interval [CI]: 107.8-110.5). The estimates of the multivariable regression models demonstrated slightly higher FSIQ scores among the exposed than the nonexposed. The adjusted β of 100%LEFW versus 0%LEFW was 1.07 (95% CI: -2.86, 5.01) and of having dental fluorosis versus no fluorosis was 0.28 (95% CI: -3.00, 3.57). The hypothesis of noninferiority tests found that FSIQ scores of those exposed and nonexposed to fluoride were equivalent. The study provided consistent evidence that early childhood exposure to fluoride does not have effects on cognitive neurodevelopment.

Correlation of fluoride intake with haemoglobin level and intelligence quotient in 8-12 year aged children: an observational study from India

BACKGROUND

Fluorosis caused by excess intake of fluoride can affects various soft tissues of the body, such as the gastrointestinal tract, blood, brain tissues and thyroid gland apart from dental fluorosis and skeletal fluorosis. Nonskeletal fluorosis is considered reversible if diagnosed early and treated promptly. Therefore, diagnostic methods that can be easily performed even by primary health care workers and depict any ongoing health problems, should be validated. Dental fluorosis, assessment of fluoride in urine and water are tests that fulfill these requirements. To date, no study has correlated haemoglobin (Hb) with dental fluorosis; moreover, studies focusing on intelligence quotient (IQ) had conflicting results and need further research. Hence, study was conducted to determine any relationship among different fluoride assessment parameters (severity of dental fluorosis, fluoride level in urine and drinking water) with IQ status and hemoglobin level of children aged 8-12 years, affected with or without dental fluorosis.

METHODS

A total of 300 children aged 8-12 years were evaluated for dental fluorosis via Dean's index, IQ level via Raven's coloured progressive matrices test, Hb level, and fluoride content in water and urine.

RESULTS

Water fluoride, age and gender were significantly associated with Hb. Intelligence was significantly related to urinary fluoride levels. Presence or absence of dental fluorosis and its severity were not significantly related to IQ or Hb.

CONCLUSIONS

Excess fluoride intake has adverse effects on hematological parameters and children's cognitive neurodevelopment, which were evaluated by current fluoride exposure markers, i.e., water and urinary fluoride. However, dental fluorosis cannot be used as a definitive assessment marker for these conditions, as it is not significantly correlated with these conditions.

Fluoride Induces Neurocytotoxicity by Disrupting Lysosomal Iron Metabolism and Membrane Permeability

The detrimental effects of fluoride on neurotoxicity have been widely recorded, yet the detailed mechanisms underlying these effects remain unclear. This study explores lysosomal iron metabolism in fluoride-related neurotoxicity, with a focus on the Steap3/TRPML1 axis. Utilizing sodium fluoride (NaF)-treated human neuroblastoma (SH-SY5Y) and mouse hippocampal neuron (HT22) cell lines, our research demonstrates that NaF enhances the accumulation of ferrous ions (Fe2+) in these cells, disrupting lysosomal iron metabolism through the Steap3/TRPML1 axis. Notably, NaF exposure upregulated ACSL4 and downregulated GPX4, accompanied by reduced glutathione (GSH) levels and superoxide dismutase (SOD) activity and increased malondialdehyde (MDA) levels. These changes indicate increased vulnerability to ferroptosis within neuronal cells. The iron chelator deferoxamine (DFO) mitigates this disruption. DFO binds to lysosomal Fe2+ and inhibits the Steap3/TRPML1 axis, restoring normal lysosomal iron metabolism, preventing lysosomal membrane permeabilization (LMP), and reducing neuronal cell ferroptosis. Our findings suggest that interference in lysosomal iron metabolism may mitigate fluoride-induced neurotoxicity, underscoring the critical role of the Steap3/TRPML1 axis in this pathological process.

Urinary Fluoride Levels Among Youth in the National Health and Nutrition Examination Survey (NHANES) 2015-2016: Potential Differences According to Race

BACKGROUND/OBJECTIVES

Urinary fluoride (UF) is the most well-established biomarker for fluoride exposure, and understanding its distribution can inform risk assessment for potential adverse systemic health effects. To our knowledge, this study is the first to report distributions of UF among youth according to sociodemographic factors in a nationally representative United States (US) sample.

METHODS

The study included 1191 children aged 6-11 years and 1217 adolescents aged 12-19 years from the National Health and Nutrition Examination Survey (NHANES) 2015-2016. We examined UF according to sociodemographic variables as well as Spearman correlations between UF and plasma fluoride. Survey-weighted quantile regression examined associations between tap water fluoride and UF levels adjusted for covariates.

RESULTS

The average age of participants was 12.5 years. The median (IQR) UF and water fluoride concentrations were 0.52 (0.50) mg/L and 0.39 (0.54) mg/L, respectively. Children had higher UF levels than adolescents and males had higher UF levels than females. UF differed according to race/ethnicity among both children and adolescents. Specifically, non-Hispanic Black youth tended to have higher UF levels than all participants except for those classified as other race/multiracial. UF and plasma fluoride were moderately correlated for children and adolescents. Higher water fluoride levels were associated with higher UF levels, and the magnitudes of association were larger at higher quantiles of UF (β = 0.14, p < 0.001; β = 0.20, p< 0.001 at the 25th and 50th quantiles, respectively). The magnitude of association between water fluoride and UF was the largest for non-Hispanic Black participants (predictive margin = 0.3, p < 0.001).

CONCLUSIONS

Non-Hispanic Black youth in the US may have greater fluoride exposure and receive more of their fluoride intake from tap water than youth of other races/ethnicities. Factors contributing to potential racial/ethnic disparities in fluoride exposure within the US warrant further investigation so that they can be mitigated to reduce the potential for harm.

Tanshinone IIA attenuates fluoride-induced spinal cord injury by inhibiting ferroptosis and inflammation

Excessive fluoride exposure can lead to health problems, such as fluorosis and neurotoxicity. However, effective therapeutic strategies for neurofluorosis remain elusive due to a limited understanding of the underlying molecular mechanisms. This study aimed to investigate the effects of Tanshinone IIA on spinal cord injury induced by high-fluoride exposure. To identify dysregulated genes associated with ferroptosis, we conducted an intersection analysis between differentially expressed genes in fluoride-treated HOS cells (GSE70719) and ferroptosis-related genes from the FerrDb database. A rat model of fluoride-induced spinal cord injury was established, revealing evidence of aberrant molecular and structural changes. Furthermore, the study demonstrated that Tanshinone IIA restored the altered expression of nine ferroptosis-related genes, eight fluorosis-related inflammatory indicators, and the observed structural changes. Overall, these findings suggest that Tanshinone IIA therapeutic potential in the treatment of fluoride-induced spinal cord injury by inhibiting ferroptosis and inflammation.

Associations of gestational and childhood exposure to lead, cadmium, and fluoride with cognitive abilities, behavior, and social communication at 4 years of age: NICE birth cohort study

BACKGROUND

Early-life lead exposure affects cognitive development and emerging evidence suggests similar effects of cadmium and fluoride.

OBJECTIVE

To assess the impact of gestational and childhood exposure to lead, cadmium, and fluoride on cognitive abilities and behavioral and social communication problems.

METHODS

We studied 470 pregnant women (gestational week 29) and their 4-year-old children from the NICE cohort in northern Sweden. Concentrations of erythrocyte lead and cadmium and urinary cadmium were measured using inductively coupled plasma mass spectrometry and urinary fluoride with an ion-selective electrode. Urinary concentrations were specific-gravity adjusted. Associations of log2-transformed exposure concentrations with cognitive abilities (full-scale IQ and verbal comprehension by Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition), behavioral problems (Child Behavior Checklist), and social communication (Social Responsiveness Scale-Second Edition) were evaluated with multivariable-adjusted linear regression analysis.

RESULTS

Both gestational and cord erythrocyte lead concentrations were non-significantly inversely associated with child cognitive abilities (full-scale IQ: B [95%CI]: -1.2 [-2.9, 0.5] and -1.6 [-3.7, 0.4], respectively; per doubling of exposure). Similarly, both gestational and child urinary cadmium were inversely associated with cognitive abilities (full-scale IQ: -1.1 [-2.5, 0.3] and -1.1 [-2.5, 0.4], verbal comprehension: -1.2 [-3.1, 0.6] and -1.4 [-3.4, 0.6], respectively). Urinary fluoride concentrations showed no association with cognitive abilities. However, gestational fluoride was associated with increasing externalizing problems (0.9 [-0.3, 2.0]) and ADHD raw scores (0.3 [0.0, 0.6]). Childhood erythrocyte lead and urinary cadmium were non-significantly associated with increased behavioral problems (lead with total problems: 1.2 [-0.4, 2.9] and internalizing problems: 1.5 [-0.4, 3.4]; cadmium with externalizing problems: 1.1 [-0.2, 2.4]).

CONCLUSION

Despite non-significant associations, both lead and cadmium exposure showed consistent inverse associations with cognitive abilities at 4 years, whereas associations with behavioral problems were less conclusive, especially for cadmium. Results on fluoride indicated association with externalizing problems, including ADHD, but prevalence of behavioral problems was low, increasing uncertainty.

What's in the water? Long-run effects of fluoridation on health and economic self-sufficiency

Community water fluoridation has been named one of the 10 greatest public health achievements of the 20th century for its role in improving dental health. Fluoride has large negative effects at high doses, clear benefits at low levels, and an unclear optimal dosage level. I leverage county-level variation in the timing of fluoride adoption, combined with restricted U.S. Census data that link over 29 million individuals to their county of birth, to estimate the causal effects of childhood fluoride exposure. Children exposed to community water fluoridation from age zero to five are worse off as adults on indices of economic self-sufficiency (-1.9% of a SD) and physical ability and health (-1.2% of a SD). They are also significantly less likely to graduate high school (-1.5 percentage points) or serve in the military (-1.0 percentage points). These findings challenge existing conclusions about safe levels of fluoride exposure.

Impact of fluorosis on molecular predictors in pathogenesis of type 2 diabetes associated microvascular complications

AIM

This review presents specific insights on the molecular underpinnings of the connection between fluorosis, type 2 diabetes, and microvascular complications, along with the novel biomarkers that are available for early detection.

SUMMARY

Fluoride is an essential trace element for the mineralization of teeth and bones in humans. Exposure to higher concentrations of fluoride has harmful effects that significantly outweigh its advantageous ones. Dental fluorosis and skeletal fluorosis are the common side effects of exposure to fluoride, which affect millions of individuals globally. Alongside, it also causes non-skeletal fluorosis, which affects the population suffering from non-communicable diseases like diabetes by impacting the soft tissues and causing diabetic microvascular complications. Previous studies reported the prevalence range of these diabetic complications of neuropathy (3-65 %), nephropathy (1-63 %), and retinopathy (2-33 %). Fluoride contributes to the development of these complications by causing oxidative stress, cellular damage, degrading the functioning capability of mitochondria, and thickening the retinal vein basement.

CONCLUSION

Early diagnosis is a prompt way of prevention, and for that, biomarkers have emerged as an innovative and useful technique. This allows healthcare practitioners and policymakers in endemic areas to comprehend the molecular complexities involved in the advancement of diabetic microvascular problems in the context of high fluoride exposure.

Epigenome-wide association study of fluoride exposure during early adolescence and DNA methylation among U.S. children

Exposure to fluoride in early childhood has been associated with altered cognition, intelligence, attention, and neurobehavior. Fluoride-related neurodevelopment effects have been shown to vary by sex and very little is known about the mechanistic processes involved. There is limited research on how fluoride exposure impacts the epigenome, potentially leading to changes in DNA methylation of specific genes regulating key developmental processes. In the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS), urine samples were analyzed using a microdiffusion method to determine childhood urinary fluoride adjusted for specific gravity (CUFsg) concentrations. Whole blood DNA methylation was assessed using the Infinium MethylationEPIC BeadChip 850 k Array. In a cross-sectional analysis, we interrogated epigenome-wide DNA methylation at 775,141 CpG loci across the methylome in relation to CUFsg concentrations in 272 early adolescents at age 12 years. Among all participants, higher concentrations of CUF were associated with differential methylation of one CpG (p < 6 × 10-8) located in the gene body of GBF1 (cg25435255). Among females, higher concentrations of CUFsg were associated with differential methylation of 7 CpGs; only three CpGs were differentially methylated among males with no overlap of significant CpGs observed among females. Secondary analyses revealed several differentially methylated regions (DMRs) and CpG loci mapping to genes with key roles in psychiatric outcomes, social interaction, and cognition, as well as immunologic and metabolic phenotypes. While fluoride exposure may impact the epigenome during early adolescence, the functional consequences of these changes are unclear warranting further investigation.

The CATFISH study: An evaluation of a water fluoridation program in Cumbria, UK

OBJECTIVES

The objective was to assess the effectiveness of a Water Fluoridation program on a contemporary population of children.

METHODS

The study used a longitudinal prospective cohort design. In Cumbria, England, two groups of children were recruited and observed over a period of 5-6 years. The Birth Cohort consisted of families recruited from two hospitals in Cumbria where children were conceived after water fluoridation was reintroduced. The systemic and topical effects of community water fluoridation were evaluated in the Birth Cohort. The Older Cohort were approximately 5 years old and recruited from primary schools in Cumbria, shortly after water fluoridation was reintroduced. The predominantly topical effects of fluoridated water were evaluated in the Older Cohort. The primary outcome was the proportion of children with clinical evidence of caries experience in their primary (Birth Cohort) or permanent teeth (Older Cohort). Unadjusted and adjusted regression models were used for analysis.

RESULTS

The final clinical examinations for the Birth Cohort involved 1444 participants (mean age 4.8 years), where 17.4% of children in the intervention group were found to have caries experience, compared to 21.4% in the control group. A beneficial effect of water fluoridation was observed adjusting for deprivation (a socioeconomic measure), sex, and age, (adjusted odds ratio 0.74 95% CI 0.55 to 0.98). The final Older Cohort clinical examinations involved 1192 participants (mean age 10.8 years) where 19.1% of children in the intervention group were found to have caries experience compared to 21.9% in the control group (adjusted odds ratio 0.80, 95% CI 0.58 to 1.09). For both the Birth Cohort and Older Cohort there was evidence of a beneficial effect on dmft/DMFT count (IRR 0.61, 95% CI 0.44, 0.86) and (IRR 0.69, 95% CI 0.52, 0.93) respectively. No conclusive proof was found to indicate that the effectiveness of water fluoridation differed across area deprivation quintiles.

CONCLUSIONS

In the contemporary context of lower caries levels and widespread use of fluoride toothpaste, the impact of water fluoridation on the prevalence of caries was smaller than previous studies have reported. It is important to consider the clinical importance of the absolute reduction in caries prevalence against the use of other dental caries preventive measures.

Impact of antenatal exposure to a mixture of persistent organic pollutants on intellectual development

OBJECTIVE

Strong experimental evidence exists that several endocrine disrupting chemicals (EDCs) have neurobehavioral toxicity. However, evidence of associations between prenatal exposure and child's cognitive development is inconsistent. Moreover, toxicants are generally analyzed one by one without considering aggregate effects. We examined here the impact of a prenatal exposure to a mixture of persistent organic pollutants (POPs) on intellectual abilities in preschool children, and compared their effects to those described in the literature.

METHODS

Sixty-two children were included in a longitudinal cohort. Four organochlorine pesticides, four polychlorinated biphenyls (PCBs) and seven perfluorinated compounds (PFCs) were measured in cord blood. Intellectual abilities were assessed at 6 years of age using the Wechsler Preschool and Primary Scale of Intelligence 4th ed. (WPPSI-IV). We examined the associations between a mixture of POPs and cognitive performances using principal components approach (PCA) and weighted quantile sum (WQS) regression taking sex difference into account.

RESULTS

No negative correlation was found when analyses were performed on boys and girls together. In sex-stratified analyses, lower scores in full scale intelligence quotient (FSIQ) and fluid reasoning index (FRI) were observed in boys most exposed to a mixture of POPs. Increase of the WQS index was also associated with lower verbal comprehension index (VCI) scores in girls only. No other negative correlation was found using both WQS and PCA models.

CONCLUSION

Our study suggests deleterious associations between antenatal exposure to a mixture of POPs and sex-specific cognitive level, clarifying some trends described in the literature.

Flawed MIREC fluoride and intelligence quotient publications: A failed attempt to undermine community water fluoridation

OBJECTIVE

To assess the evidence presented in a set of articles that use the Canadian Maternal-Infant Research on Environmental Chemicals (MIREC) study database to claim that community water fluoridation (CWF) is associated with harm to foetal and infant cognitive development.

METHODS

Critical appraisal of measurements and processes in the MIREC database, and articles derived therefrom. MIREC's cohort is approximately 2000 pregnant women recruited in 10 centres across Canada, 2008-2011, leading to measuring 512 children aged 3-6 years in six cities. Fluoride exposure was measured by city fluoridation status, self-reports and maternal spot urine samples. Intelligence Quotient (IQ) was measured using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III) by different assessors in each city.

RESULTS

MIREC's fluoride and IQ measurements are invalid and therefore cannot support the claim that CWF is associated with IQ decline in children.

CONCLUSIONS

The MIREC fluoride-IQ articles' results should be considered unacceptable for legal and policy purposes; other water fluoridation studies and systematic reviews show no effect of fluoridation on cognition.

How scientists should disagree

Reflecting broader societal trends, a lack of civility has crept its way into scientific discourse. It has become routine for scientists who disagree with each other to make disparaging accusations, most commonly that they are "shills" or are being paid off by an interest group. Instead, we should keep four things in mind: (1) Most scientists who disagree with you are well-intentioned; (2) There could be a failure to communicate; (3) "Hanlon's Razor" - which asserts that we should "never attribute to malice that which is adequately explained by stupidity" - is probably true; and (4) Like all humans, scientists have pride and do not like to be proven wrong. Most disagreements result from some combination of these. Only rarely should we consider that a disagreement is the result of something more nefarious, like corruption. IMPACT: Reflecting broader societal trends, a lack of civility has crept its way into scientific discourse. We must reverse this. The scientific community can lead the way toward a more civil society.

Fluoride-related changes in the fetal cord blood proteome; a pilot study

BACKGROUND

Fluoride exposure during pregnancy has been associated with various effects on offspring, including changes in behavior and IQ. To provide clues to possible mechanisms by which fluoride may affect human fetal development, we completed proteomic analyses of cord blood serum collected from second-trimester pregnant women residing in northern California, USA.

OBJECTIVE

To identify changes in cord blood proteins associated with maternal serum fluoride concentration in pregnant women.

METHODS

The proteomes of 19 archived second-trimester cord blood samples from women living in northern California, USA, and having varied serum fluoride concentrations, were analyzed by quantitative mass spectrometry. The 327 proteins that were quantified were characterized by their abundance relative to maternal serum fluoride concentration, and subjected to pathway analyses using PANTHER and Ingenuity Pathway Analysis processes.

RESULTS

Pathway analyses showed significant increases in process related to reactive oxygen species and cellular oxidant detoxification, associated with increasing maternal serum fluoride concentrations. Pathways showing significant decreases included complement cascade, suggesting alterations in alterations in process associated with inflammation.

CONCLUSION

Maternal fluoride exposure, as measured by serum fluoride concentrations in a small, but representative sample of women from northern California, USA, showed significant changes in the second trimester cord blood proteome relative to maternal serum fluoride concentration.

Lithium and its effects: does dose matter?

BACKGROUND

Decades of clinical research have demonstrated the efficacy of lithium in treating acute episodes (both manic and depressive), as well as in preventing recurrences of bipolar disorder (BD). Specific to lithium is its antisuicidal effect, which appears to extend beyond its mood-stabilizing properties. Lithium's clinical effectiveness is, to some extent, counterbalanced by its safety and tolerability profile. Indeed, monitoring of lithium levels is required by its narrow therapeutic index. There is consensus that adequate serum levels should be above 0.6 mEq/L to achieve clinical effectiveness. However, few data support the choice of this threshold, and increasing evidence suggests that lithium might have clinical and molecular effects at much lower concentrations.

CONTENT

This narrative review is aimed at: (1) reviewing and critically interpreting the clinical evidence supporting the use of the 0.6 mEq/L threshold, (2) reporting a narrative synthesis of the evidence supporting the notion that lithium might be effective in much lower doses. Among these are epidemiological studies of lithium in water, evidence on the antisuicidal, anti-aggressive, and neuroprotective effects, including efficacy in preventing cognitive impairment progression, Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS), of lithium; and (3) revieweing biological data supporting clinically viable uses of lithium at low levels with the delineation of a mechanistic hypothesis surrounding its purported mechanism of action. The study selection was based on the authors' preference, reflecting the varied and extensive expertise on the review subject, further enriched with an extensive pearl-growing strategy for relevant reviews and book sections.

CONCLUSIONS

Clinical and molecular effects of lithium are numerous, and its effects also appear to have a certain degree of specificity related to the dose administered. In sum, the clinical effects of lithium are maximal for mood stabilisation at concentrations higher than 0.6 mEq/l. However, lower levels may be sufficient for preventing depressive recurrences in older populations of patients, and microdoses could be effective in decreasing suicide risk, especially in patients with BD. Conversely, lithium's ability to counteract cognitive decline appears to be exerted at subtherapeutic doses, possibly corresponding to its molecular neuroprotective effects. Indeed, lithium may reduce inflammation and induce neuroprotection even at doses several folds lower than those commonly used in clinical settings. Nevertheless, findings surrounding its purported mechanism of action are missing, and more research is needed to investigate the molecular targets of low-dose lithium adequately.

A Bayesian benchmark concentration analysis for urinary fluoride and intelligence in adults in Guizhou, China

Environmental fluoride exposure has been linked to numerous cases of fluorosis worldwide. Previous studies have indicated that long-term exposure to fluoride can result in intellectual damage among children. However, a comprehensive health risk assessment of fluorosis-induced intellectual damage is still pending. In this research, we utilized the Bayesian Benchmark Dose Analysis System (BBMD) to investigate the dose-response relationship between urinary fluoride (U-F) concentration and Raven scores in adults from Nayong, Guizhou, China. Our research findings indecate a dose-response relationship between the concentration of U-F and intelligence scores in adults. As the benchmark response (BMR) increased, both the benchmark concentration (BMCs) and the lower bound of the credible interval (BMCLs) increased. Specifically, BMCs for the association between U-F and IQ score were determined to be 0.18 mg/L (BMCL1 = 0.08 mg/L), 0.91 mg/L (BMCL5 = 0.40 mg/L), 1.83 mg/L (BMCL10 = 0.83 mg/L) when using BMRs of 1 %, 5 %, and 10 %. These results indicate that U-F can serve as an effective biomarker for monitoring the loss of IQ in population. We propose three interim targets for public policy in preventing interllectual harm from fluoride exposure.

Water Fluoridation and Birth Outcomes in California

BACKGROUND

There is a lack of research on the relationship between water fluoridation and pregnancy outcomes.

OBJECTIVES

We assessed whether hypothetical interventions to reduce fluoride levels would improve birth outcomes in California.

METHODS

We linked California birth records from 2000 to 2018 to annual average fluoride levels by community water system. Fluoride levels were collected from consumer confidence reports using publicly available data and public record requests. We estimated the effects of a hypothetical intervention reducing water fluoride levels to 0.7  ppm (the current level recommended by the US Department of Health and Human Services) and 0.5  ppm (below the current recommendation) on birth weight, birth-weight-for-gestational age z-scores, gestational age, preterm birth, small-for-gestational age, large-for-gestational age, and macrosomia using linear regression with natural cubic splines and G-computation. Inference was calculated using a clustered bootstrap with Wald-type confidence intervals. We evaluated race/ethnicity, health insurance type, fetal sex, and arsenic levels as potential effect modifiers.

RESULTS

Fluoride levels ranged from 0 to 2.5  ppm , with a median of 0.51  ppm . There was a small negative association on birth weight with the hypothetical intervention to reduce fluoride levels to 0.7  ppm [- 2.2 g ; 95% confidence interval (CI): - 4.4 , 0.0] and to 0.5  ppm (- 5.8 g ; 95% CI: - 10.0 , - 1.6 ). There were small negative associations with birth-weight-for-gestational-age z-scores for both hypothetical interventions (0.7  ppm : - 0.004 ; 95% CI: - 0.007 , 0.000 and 0.5  ppm : - 0.006 ; 95% CI: - 0.013 , 0.000). We also observed small negative associations for risk of large-for-gestational age for both the hypothetical interventions to 0.7  ppm [risk difference  ( RD ) = - 0.001 ; 95% CI: - 0.002 , 0.000 and 0.5  ppm (- 0.001 ; 95% CI: - 0.003 , 0.000)]. We did not observe any associations with preterm birth or with being small for gestational age for either hypothetical intervention. We did not observe any associations with risk of preterm birth or small-for-gestational age for either hypothetical intervention.

CONCLUSION

We estimated that a reduction in water fluoride levels would modestly decrease birth weight and birth-weight-for-gestational-age z-scores in California. https://doi.org/10.1289/EHP13732.

Maternal Urinary Fluoride and Child Neurobehavior at Age 36 Months

Importance

Recent studies in Canadian and Mexican populations suggest an association of higher prenatal fluoride exposure with poorer neurobehavioral development, but whether this association holds for US-based populations is unknown.

Objective

To examine associations of third trimester maternal urinary fluoride (MUF) with child neurobehavior at age 3 years in the US.

Design, Setting, and Participants

This prospective cohort study utilized urine samples archived from 2017 to 2020 and neurobehavioral data assessed from 2020 to 2023 from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) pregnancy cohort, which consisted of predominately Hispanic women residing in Los Angeles, California. Cohort eligibility criteria at recruitment included being 18 years of age or older, less than 30 weeks' gestation, and a fluent English or Spanish speaker. Exclusion criteria included having a disability preventing participation or provision of informed consent, being HIV positive or incarcerated, and having a multiple gestation pregnancy. There were 263 mother-child pairs who completed the 3-year study visit. In this analysis, women who reported prenatal smoking were excluded. Data analysis was conducted from October 2022 to March 2024.

Exposure

Specific gravity-adjusted MUF (MUFSG), a biomarker of prenatal fluoride exposure.

Main Outcomes and Measures

Neurobehavior was quantified using the Preschool Child Behavior Checklist (CBCL), which included composite scores for Total Problems, Internalizing Problems, and Externalizing Problems. CBCL composite T scores range from 28 to 100. T scores from 60 to 63 are in the borderline clinical range, whereas scores above 63 are in the clinical range. Linear and logistic regression models adjusted for covariates were conducted.

Results

A total of 229 mother-child pairs (mean [SD] maternal age, 29.45 [5.67] years; 116 female children [50.7%] and 113 male children [49.3%]) who had MUFSG measured were included in the study. Median (IQR) MUFSG was 0.76 (0.51-1.19) mg/L, and 32 participants (14.0%) had a Total Problems T score in the borderline clinical or clinical range. A 1-IQR (0.68 mg/L) increase in MUFSG was associated with nearly double the odds of the Total Problems T score being in the borderline clinical or clinical range (odds ratio, 1.83; 95% CI, 1.17-2.86; P = .008), as well as with a 2.29-point increase in T score for the Internalizing Problems composite (B = 2.29; 95% CI, 0.47-4.11; P = .01) and a 2.14-point increase in T score for the Total Problems composite (B = 2.14; 95% CI, 0.29-3.98; P = .02).

Conclusions and Relevance

In this prospective cohort study of mother-child pairs in Los Angeles, California, prenatal fluoride exposure was associated with increased neurobehavioral problems. These findings suggest that there may be a need to establish recommendations for limiting fluoride exposure during the prenatal period.

ERS Mediated by GRP-78/PERK/CHOP Signaling Is Involved in Fluoride-Induced Ameloblast Apoptosis

Fluoride can be widely ingested from the environment, and its excessive intake could result in adverse effects. Dental fluorosis is an early sign of fluoride toxicity which can cause esthetic and functional problems. Though apoptosis in ameloblasts is one of the potential mechanisms, the specific signal cascade is in-conclusive. High-throughput sequencing and molecular biological techniques were used in this study to explore the underlying pathogenesis of dental fluorosis, for its prevention and treatment. A fluorosis cell model was established. Viability and apoptosis rate of mouse ameloblast-derived cell line (LS8 cells) was measured using cell counting kit-8 (CCK-8) assay and flow cytometry analysis. Cells were harvested with or without 2-mM sodium fluoride (NaF) stimulation for high-throughput sequencing. Based on the sequencing data, subcellular structures, endoplasmic reticulum stress (ERS), and apoptosis related biomarkers were verified using transmission electron microscopy, quantitative real-time polymerase chain reaction, and Western blotting techniques. Expression of ERS markers, apoptosis related proteins, and enamel formation enzymes were detected using Western blotting after addition of 4-phenylbutyrate (4-PBA). NaF-inhibited LS8 cells displayed time- and dose- dependent viability. Additionally, apoptosis and morphological changes were observed. RNA-sequencing data showed that protein processing in endoplasmic reticulum was obviously affected. ERS and apoptosis were induced by excessive NaF. Downregulation of kallikrein-related peptidase 4 (KLK4) was also observed. Inhibition of ERS by 4-PBA rescued the apoptotic and functional protein changes in cells. Excessive fluoride induces apoptosis by activating ERS, which is mediated by GRP-78/PERK/CHOP signaling. Key proteinase is present in maturation-stage enamel; KLK4 was also affected by fluoride, but rescued by 4-PBA. This study presents a possibility for therapeutic strategies for dental fluorosis, while further exploration is required.

Dose dependence of prenatal fluoride exposure associations with cognitive performance at school age in three prospective studies

BACKGROUND

Fluoride may be a developmental neurotoxicant at elevated exposures. We merged new data from a prospective Odense Child Cohort (OCC) with results from two previous birth cohort studies from Mexico and Canada to characterize the dose-effect relationship in greater detail.

METHODS

The OCC contributed 837 mother-child pairs to the total of >1500. We measured creatinine-adjusted urine-fluoride concentrations in maternal urine samples obtained during late pregnancy. Child IQ was determined at age 7 years using an abbreviated version of the Wechsler Intelligence Scales for Children. Findings from the three cohorts were used to calculate the joint benchmark concentration (BMC) and the lower confidence limit (BMCL) after adjustment for covariables.

RESULTS

In the OCC, urine-fluoride concentrations varied between 0.08 and 3.04 mg/l (median 0.52 mg/l) but were not significantly associated with full-scale IQ at age 7 years (β = 0.08; 95% confidence interval -1.14 to 1.30 for a doubling in exposure). No difference was apparent between boys and girls. In the OCC, the BMC was 0.92 mg/l, with a BMCL of 0.30 mg/l. The joint analysis of all three cohorts showed a statistically significant association between urine-fluoride and IQ, with a BMC of 0.45 mg/l (BMCL, 0.28 mg/l), slightly higher than the BMC previously reported for the two North American cohorts alone.

CONCLUSIONS

As the BMCL reflects an approximate threshold for developmental neurotoxicity, the results suggest that pregnant women and children may need protection against fluoride toxicity.

Fluoride exposure and thyroid hormone levels in pregnancy: The MIREC cohort

BACKGROUND

Fluoride exposure may increase the risk of hypothyroidism, but results from previous studies are inconsistent at low-level fluoride exposure (i.e., ≤0.7 mg/L). Human studies of fluoride and thyroid hormone levels in pregnancy are scarce.

OBJECTIVES

We examined associations between fluoride exposure and maternal thyroid hormone levels in a Canadian pregnancy cohort, with consideration for fetal sex-specific effects.

METHODS

We measured fluoride concentrations in drinking water and spot urine samples collected during each trimester from 1876 pregnant women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study. We also measured maternal thyroid stimulating hormone (TSH), free thyroxine (FT4), and total thyroxine (TT4) levels during the first trimester of pregnancy. We used linear and non-linear regression models to estimate associations between fluoride exposure and levels of TSH, FT4, and TT4. We explored effect modification by fetal sex and considered maternal iodine status as a potential confounder.

RESULTS

A 1 mg/L increase in urinary fluoride was associated with a 0.30 (95 %CI: 0.08, 0.51) logarithmic unit (i.e., 35.0 %) increase in TSH among women pregnant with females, but not males (B = 0.02; 95 %CI: -0.16, 0.19). Relative to women with urinary fluoride concentrations in the first quartile (0.05-0.32 mg/L), those with levels in the third quartile (0.49-0.75 mg/L) had higher FT4 and TT4 (i.e., inverted J-shaped associations), but the association was not statistically significant after adjustment for covariates (p = 0.06). Water fluoride concentration showed a U-shaped association with maternal FT4, whereby women with water fluoride concentrations in the second (0.13-0.52 mg/L) and third (0.52-0.62 mg/L) quartiles had significantly lower FT4 compared to those with levels in the first quartile (0.04-0.13 mg/L). Adjustment for maternal iodine status did not change the results.

DISCUSSION

Fluoride exposure was associated with alterations in maternal thyroid hormone levels, the magnitude of which appeared to vary by fetal sex. Given the importance of maternal thyroid hormones for fetal neurodevelopment, replication of findings is warranted.

The fluorosis conundrum: bridging the gap between science and public health

Fluorosis, a chronic condition brought on by excessive fluoride ingestion which, has drawn much scientific attention and public health concern. It is a complex and multifaceted issue that affects millions of people worldwide. Despite decades of scientific research elucidating the causes, mechanisms, and prevention strategies for fluorosis, there remains a significant gap between scientific understanding and public health implementation. While the scientific community has made significant strides in understanding the etiology and prevention of fluorosis, effectively translating this knowledge into public health policies and practices remains challenging. This review explores the gap between scientific research on fluorosis and its practical implementation in public health initiatives. It suggests developing evidence-based guidelines for fluoride exposure and recommends comprehensive educational campaigns targeting the public and healthcare providers. Furthermore, it emphasizes the need for further research to fill the existing knowledge gaps and promote evidence-based decision-making. By fostering collaboration, communication, and evidence-based practices, policymakers, healthcare professionals, and the public can work together to implement preventive measures and mitigate the burden of fluorosis on affected communities. This review highlighted several vital strategies to bridge the gap between science and public health in the context of fluorosis. It emphasizes the importance of translating scientific evidence into actionable guidelines, raising public awareness about fluoride consumption, and promoting preventive measures at individual and community levels.

Prenatal fluoride exposure, offspring visual acuity and autonomic nervous system function in 6-month-old infants

BACKGROUND

Prenatal fluoride exposure can have adverse effects on children's development; however, associations with visual and cardiac autonomic nervous system functioning are unknown. We examined associations between prenatal fluoride exposure and visual acuity and heart rate variability (HRV) in 6-month-old infants.

METHODS

We used data from Canadian mother-infant pairs participating in the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort. We estimated prenatal fluoride exposure using: i) fluoride concentration in drinking water (mg/L), ii) maternal urinary fluoride adjusted for specific gravity (MUFSG; mg/L) and averaged across pregnancy, and iii) maternal fluoride intake (µg/kg/day) from consumption of water, tea, and coffee, adjusted for maternal body weight (kg). We used multivariable linear regression to examine associations between each measure of fluoride exposure and Teller Acuity Card visual acuity scores (n = 435) and assessed HRV (n = 400) using two measures: root mean square of successive differences (RMSSD) and the standard deviation of N-N intervals (SDNN) measured at 6-months of age.

RESULTS

Median (IQR) values for water fluoride, MUFSG, and daily fluoride intake were 0.20 (IQR: 0.13-0.56) mg/L; 0.44 (0.28-0.70) mg/L and 4.82 (2.58-10.83) µg/kg/day, respectively. After adjustment for confounding variables, water fluoride concentration was associated with poorer infant visual acuity (B = -1.51; 95 % CI: -2.14,-0.88) and HRV as indicated by lower RMSSD (B = -1.60; 95 % CI: -2.74,-0.46) but not SDNN. Maternal fluoride intake was also associated with poorer visual acuity (B = -0.82; 95 % CI: -1.35,-0.29) and lower RMSSD (B = -1.22; 95 % CI: -2.15,-0.30). No significant associations were observed between MUFSG and visual acuity or HRV.

CONCLUSION

Fluoride in drinking water was associated with reduced visual acuity and alterations in cardiac autonomic function in infancy, adding to the growing body of evidence suggesting fluoride's developmental neurotoxicity.

Regional and racial/ethnic inequalities in public drinking water fluoride concentrations across the US

BACKGROUND

Although the US Centers for Disease Control and Prevention (CDC) considers fluoridation of community water systems (CWSs) to be a major public health achievement responsible for reducing dental disease, recent epidemiologic evidence suggests that chronic exposure to population-relevant levels of fluoride may also be associated with adverse child neurodevelopmental outcomes. To our knowledge, a nationally representative database of CWS fluoride concentration estimates that can be readily linked to US epidemiologic cohorts for further study is not publicly available. Our objectives were to evaluate broad regional and sociodemographic inequalities in CWS fluoride concentrations across the US, and to determine if county-level racial/ethnic composition was associated with county-level CWS fluoride.

METHODS

We generated CWS-level (N = 32,495) and population weighted county-level (N = 2152) fluoride concentration estimates using over 250,000 routine compliance monitoring records collected from the US Environmental Protection Agency's (EPA) Third Six Year Review (2006-2011). We compared CWS-level fluoride distributions across subgroups including region, population size served, and county sociodemographic characteristics. In county-level spatial error models, we also evaluated geometric mean ratios (GMRs) of CWS fluoride per 10% higher proportion of residents belonging to a given racial/ethnic subgroup.

RESULTS

4.5% of CWSs (serving >2.9 million residents) reported mean 2006-2011 fluoride concentrations ≥1500 µg/L (the World Health Organization's guideline for drinking water quality). Arithmetic mean, 90th, and 95th percentile contaminant concentrations were greatest in CWSs reliant on groundwater, located in the Southwest and Eastern Midwest, and serving Semi-Urban, Hispanic communities. In fully adjusted spatial error models, the GMR (95% CI) of CWS fluoride per a 10% higher proportion of county residents that were Hispanic/Latino was 1.16 (1.10, 1.23).

IMPACT STATEMENT

We find that over 2.9 million US residents are served by public water systems with average fluoride concentrations exceeding the World Health Organization's guidance limit. We also find significant inequalities in community water system fluoride concentration estimates (2006-2011) across the US, especially for Hispanic/Latino communities who also experience elevated arsenic and uranium in regulated public drinking water systems. Our fluoride estimates can be leveraged in future epidemiologic studies to assess the potential association between chronic fluoride exposure and related adverse outcomes.

Perinatal Exposure to Trace Elements: The Dubious Culprit of Autistic Spectrum Disorder in Children

There is evidence that few trace elements in the environment work as hazardous materials in terms of their exposure in the perinatal period, causing autistic spectrum disorder (ASD) in children, and avoiding these exposures in the environment can reduce the number of new cases. This perspective study provides preliminary evidence to consider a few trace elements as culprits for ASD. More studies with larger cohorts are needed, but meanwhile, as per available evidence, exposure to these hazardous materials must be warranted during pregnancy and early stages of life.

Systematic review of epidemiological and toxicological evidence on health effects of fluoride in drinking water

INTRODUCTION

Fluoride is a naturally occurring substance that is also added to drinking water, dental hygiene products, and food supplements for preventing dental caries. Concerns have been raised about several other potential health risks of fluoride.

OBJECTIVE

To conduct a robust synthesis of evidence regarding human health risks due to exposure to fluoride in drinking water, and to develop a point of departure (POD) for setting a health-based value (HBV) for fluoride in drinking water.

METHODS

A systematic review of evidence published since recent reviews of human, animal, and in vitro data was carried out. Bradford Hill considerations were used to weigh the evidence for causality. Several key studies were considered for deriving PODs.

RESULTS

The current review identified 89 human studies, 199 animal studies, and 10 major in vitro reviews. The weight of evidence on 39 health endpoints was presented. In addition to dental fluorosis, evidence was considered strong for reduction in IQ scores in children, moderate for thyroid dysfunction, weak for kidney dysfunction, and limited for sex hormone disruptions.

CONCLUSION

The current review identified moderate dental fluorosis and reduction in IQ scores in children as the most relevant endpoints for establishing an HBV for fluoride in drinking water. PODs were derived for these two endpoints, although there is still some uncertainty in the causal weight of evidence for causality for reducing IQ scores in children and considerable uncertainty in the derivation of its POD. Given our evaluation of the overall weight of evidence, moderate dental fluorosis is suggested as the key endpoint until more evidence is accumulated on possible reduction of IQ scores effects. A POD of 1.56 mg fluoride/L for moderate dental fluorosis may be preferred as a starting point for setting an HBV for fluoride in drinking water to protect against moderate and severe dental fluorosis. Although outside the scope of the current review, precautionary concerns for potential neurodevelopmental cognitive effects may warrant special consideration in the derivation of the HBV for fluoride in drinking water.

New easily recycled carrier based polyurethane foam by loading Al-MOF and biochar for selective removal of fluoride ion from aqueous solutions

The production of Integrated circuits (ICs) generates wastewater with a high concentration of residual fluoride ions, necessitating highly efficient fluorine removal methods. In this study, a novel composite carrier was developed using a hydrothermal synthesis method to load Al-MOF and biochar (BC) onto polyurethane foam (PUF), resulting in the composite foam of Al-MOF-PUF@BC. The results showed that the composite carrier exhibited a stable fluoride removal effect, with a maximum adsorption capacity of 16.52 mg/g at room temperature. The adsorption isotherm curves were consistent with the Langmuir isotherm model, and the adsorption kinetics were well-described by the pseudo-first-order model. The mechanism of fluorine adsorption on Al-MOF-PUF@BC was ligand exchange with hydroxyl groups and the formation of FAl bonds. Density functional theory (DFT) calculations revealed that the adsorption energy reached -246.7 eV, indicating stable adsorption for fluoride ions. The composite foam demonstrated excellent regenerative properties and was effective for fluoride removal in actual IC wastewater.

Community Water Fluoridation in Focus: A Comprehensive Look at Fluoridation Levels across America

Objective: This study reports on the number and percentage of community water systems (CWSs) meeting fluoride concentration standards set by the U.S. Department of Health and Human Services (DHHS). The study also explored changes in the population exposed to optimally fluoridated water in these systems between 2006 and 2020. Methods: This study analyzed U.S. Centers for Disease Control and Prevention data from 2006 to 2020, tabulating state-specific CWS fluoridation rates, ranking them, and calculating the percent change. Results: In 2020, 72.7% of the US population received CWS water, with 62.9% of those individuals served by a CWS system meeting DHHS fluoridation standards. This compares to 69.2% receiving CWS water in 2006 and 74.6% in 2012. The overall change in those receiving fluoridated water was 1.4%, from 61.5% in 2006 to 62.9% in 2020. State-specific percentages ranged from 8.5% in Hawaii to 100% in Washington DC in 2020 (median: 76.4%). Conclusions: Although endorsed by the American Dental Association, the percentage of individuals receiving fluoridated water did not increase substantially from 2006 to 2020, indicating that there has not been much progress toward meeting the Healthy People 2030 goal that 77.1% of Americans receive water with enough fluoride to prevent tooth decay.

Chronic exposure to environmentally relevant concentration of fluoride impairs osteoblast's collagen synthesis and matrix mineralization: Involvement of epigenetic regulation in skeletal fluorosis

Globally, 200 million people are suffering from toxic manifestations of Fluoride(F), dental and skeletal fluorosis; unfortunately, there is no treatment. To unravel the pathogenesis of skeletal fluorosis, we established fluorosis mice by treating environmentally relevant concentration of F (15 ppm NaF) through drinking water for 4 months. As in skeletal fluorosis, locomotor disability, crippling deformities occur and thus, our hypothesis was F might adversely affects collagen which gives the bone tensile strength. This work inevitably had to be carried out on osteoblast cells, responsible for synthesis, deposition, and mineralization of bone matrix. Isolated osteoblast cells were confirmed by ALP activity and mineralized nodules formation. Expression of collagen Col1a1, Col1a2, COL1A1 was significantly reduced in treated mice. Further, a study revealed the involvement of epigenetic regulation by promoter hypermethylation of Col1a1; expressional alterations of transcription factors, calcium channels and other genes e.g., Cbfa-1, Tgf-β1, Bmp1, Sp1, Sp7, Nf-Kb p65, Bmp-2, Bglap, Gprc6a and Cav1.2 are associated with impairment of collagen synthesis, deposition and decreased mineralization thus, enfeebling bone health. This study indicates the possible association of epigenetic regulation in skeletal fluorosis. However, no association was found between polymorphisms in the Col1a1 (RsaI, HindIII) and Col1a2 (RsaI, HindIII) genes with fluorosis in mice.

Cohort profile update: The Canadian Maternal-Infant Research on Environmental Chemicals Child Development study (MIREC-CD PLUS)

BACKGROUND

The pan-Canadian Maternal-Infant Research on Environmental Chemicals (MIREC) study was established to determine whether maternal environmental chemical exposures were associated with adverse pregnancy outcomes in 2001 pregnant women.

OBJECTIVES

The MIREC-Child Development (CD PLUS) study followed this cohort with the goal of assessing the potential effects of prenatal exposures on anthropometry and neurodevelopment in early childhood.

POPULATION

MIREC families with children between the ages of 15 months and 5 years who had agreed to be contacted for future research (n = 1459) were invited to participate in MIREC-CD PLUS which combines data collected from an online Maternal Self-Administered Questionnaire with biomonitoring and neurodevelopment data collected from two in-person visits.

PRELIMINARY RESULTS

Between April 2013 and March 2015, 803 children participated in the Biomonitoring visit where we collected anthropometric measures, blood, and urine from the children. The Behavioural Assessment System for Children-2, Behaviour Rating Inventory of Executive Function, MacArthur-Bates Communicative Development Inventories and the Communication subscale of the Adaptive Behaviour Scale from the Bayley Scales of Infant and Toddler Development-III are available on close to 900 children. There were 610 singleton children who completed in-person visits for neurodevelopment assessments including the Social Responsiveness Scale, Wechsler Preschool Primary Scale of Intelligence-III and NEuroPSYchological assessments (NEPSY). Currently, we are following the cohort into early adolescence to measure the impact of early life exposures on endocrine and metabolic function (MIREC-ENDO).

CONCLUSIONS

Data collection for the MIREC-CD PLUS study is complete and analysis of the data continues. We are now extending the follow-up of the cohort into adolescence to measure the impact of early life exposures on endocrine and metabolic function (MIREC-ENDO). MIREC-CD PLUS is limited by loss to follow-up and the fact that mothers are predominately of higher socioeconomic status and 'White' ethnicity, which limits our generalizability. However, the depth of biomonitoring and clinical measures in MIREC provides a platform to examine associations of prenatal, infancy and childhood exposures with child growth and development.

Urinary fluoride levels and metal co-exposures among pregnant women in Los Angeles, California

BACKGROUND

Fluoride is ubiquitous in the United States (US); however, data on biomarkers and patterns of fluoride exposure among US pregnant women are scarce. We examined specific gravity adjusted maternal urinary fluoride (MUFsg) in relation to sociodemographic variables and metal co-exposures among pregnant women in Los Angeles, California.

METHODS

Participants were from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) cohort. There were 293 and 490 women with MUFsg measured during first and third trimesters, respectively. An intra-class correlation coefficient examined consistency of MUFsg between trimesters. Kruskal-Wallis and Mann-Whitney U tests examined associations of MUFsg with sociodemographic variables. Covariate adjusted linear regression examined associations of MUFsg with blood metals and specific gravity adjusted urine metals among a subsample of participants within and between trimesters. A False Discovery Rate (FDR) correction accounted for multiple comparisons.

RESULTS

Median (IQR) MUFsg was 0.65 (0.5) mg/L and 0.8 (0.59) mg/L, during trimesters one and three respectively. During both trimesters, MUFsg was higher among older participants, those with higher income, and White, non-Hispanic participants than Hispanic participants. MUFsg was also higher for White, non-Hispanic participants than for Black, non-Hispanic participants in trimester three, and for those with graduate training in trimester one. MUFsg was negatively associated with blood mercury in trimester one and positively associated with blood lead in trimester three. MUFsg was positively associated with various urinary metals, including antimony, barium, cadmium, cobalt, copper, lead, nickel, tin, and zinc in trimesters one and/or three.

CONCLUSIONS

MUFsg levels observed were comparable to those found in pregnant women in Mexico and Canada that have been associated with poorer neurodevelopmental outcomes. Lower urinary fluoride levels among Hispanic and non-Hispanic Black participants in MADRES compared to non-Hispanic White participants may reflect lower tap water consumption or lower fluoride exposure from other sources. Additional research is needed to examine whether MUFsg levels observed among pregnant women in the US are associated with neurodevelopmental outcomes.

Association of maternal prenatal urinary fluoride levels with ADHD symptoms in childhood

BACKGROUND

Health concerns about the potential impact of exposure to fluoride via drinking water (DW) on neuropsychological development include behavioral outcomes such as ADHD.

OBJECTIVE

We aimed to examine the association between prenatal maternal urinary fluoride and symptoms associated with attention-deficit/hyperactivity disorder (ADHD) at the age of 8 and 11 years.

METHOD

Data from 255 to 236 mother-child pairs from the "Infancia y Medio Ambiente" (INMA) birth cohort (Gipuzkoa; Spain) with maternal urinary F adjusted for creatinine (MUFcr) during pregnancy (first and third trimester) and child assessments of ADHD-like symptoms reported by Conners' Rating Scales-Revised at age of 8 and 11 years was available. Clinical approach was also used: cut off criteria (T > 66). Multiple linear regression models were fitted when outcomes were analyzed as continuous, and logistic regression models when the outcomes were analyzed with a categorical clinical approach. Covariates related to maternal characteristics, birth outcomes, childhood, quality of family context and biomarkers of neuro-toxicants were used.

RESULTS

No association was found between MUFcr levels during pregnancy and cognitive problems-inattention, hyperactivity or ADHD index score of symptoms at 8 or 11 years. When results were analyzed from the perspective of a clinical approach, at the age of 11 years, there were significant inverse association between MUFcr and being categorized as a cognitive problems-inattention case. ORs were also indicative of a lower risk, although not significant, for ADHD index at age 11. Sensitivity analyses, taking into consideration quality of family context or the levels of other toxicants during pregnancy showed similar results.

CONCLUSIONS

Higher levels of MUFcr in pregnant women were associated with a lower risk of cognitive problems-inattention at 11 years. These findings are inconsistent with those from previous studies and indicate the need for other population-based studies to confirm or overturn these results.

Fluoride distribution in selected foodstuffs from Nakuru County, Kenya, and the risk factors for its human overexposure

Critical data on the impacts of fluoride (F) in food systems along the Eastern Africa Rift Valley System (EARS) is needed for public health risk assessment and for the development of strategies for ameliorating its deleterious effects among the affected communities. Long-term F overexposure causes dental and skeletal fluorosis, and leads to neurotoxicity, which impacts several important body functions. Investigating F exposure pathways is of essence to inform and safeguard public health of the affected communities. The current study assessed the F levels in potatoes (Solanum tuberosum L.), beans (Phaseolus vulgaris L.) and garden peas (Possum sativa) from Nakuru County, Kenya, by potentiometric analysis using F ion-selective electrodes. It then evaluated the risk factors for excessive human exposure to F through contaminated foodstuffs. The mean F levels in the potatoes (8.50 ± 4.70 mg/kg), beans (8.02 ± 4.12 mg/kg) and peas (4.99 ± 1.25 mg/kg) exceeded recommended dietary allowances (RDA) level of 4 mg/kg endorsed by US Institute of Medicine for the different categories of people. The F distribution trends in beans and potatoes reflected the environmental patterns of F contamination of the study area but the spatial extent Fin the peas indicated existence of partial resistance of the pea plants to environmental F uptake. The results indicated that both the beans and the potatoes were more liable to accumulating greater amounts of F from the environment than garden peas and that all the three foodstuffs contained high F levels that posed greater risk of F overexposure and its deleterious impacts among the young children, male populations, and in people of greater body weight and high physical activity levels.

Prenatal and concurrent blood mercury concentrations and associations with IQ in canadian preschool children

BACKGROUND

Prenatal and childhood mercury (Hg) exposures have been associated with negative impacts on child neurodevelopment. It is unclear if associations persist at the low Hg exposures typical in Western countries.

OBJECTIVE

To examine associations between prenatal/childhood blood Hg concentrations and child IQ in Canadian male and female children while considering the potential modifying role of prenatal fish consumption.

METHODS

We analyzed data from the Maternal-Infant Research on Environmental Chemicals study. Hg was measured in first trimester (n = 527), cord (n = 430), and child (at 3-4 years of age, n = 355) blood and examined sex-stratified associations between blood Hg and children's Full Scale IQ (FSIQ), Verbal IQ (VIQ), Performance IQ (PIQ), and General Language Composite (GLC) scores (assessed with WPPSI-III). Prenatal Hg analyses were further stratified by prenatal fish consumption (low: 0-2, moderate: 3-7, or high: ≥8 times/month).

RESULTS

Higher cord blood Hg concentrations were associated with lower PIQ (ß = -3.27; 95%CI: 6.44, -0.09) in male children with the lowest prenatal fish consumption. Progressively stronger positive associations were observed with PIQ in male children for moderate (ß = 1.08; 95%CI: 0.10, 2.26) and high (ß = 3.07; 95%CI: 1.95, 4.19) prenatal fish consumption. Cord blood Hg concentrations were positively associated with female children's FSIQ (ß = 1.29; 95% CI: 0.77, 1.81) and PIQ (ß = 2.01; 95% CI: 1.19, 2.83); however, when stratified only in the highest fish consumption subgroup. Among female children, higher child blood Hg concentrations were associated with an approximately 1-point increase in FSIQ, VIQ, and GLC.

CONCLUSIONS

Prenatal exposure to low levels of Hg was associated with lower PIQ scores in male children with low prenatal fish intake. Positive associations between cord and child blood Hg concentrations and IQ were primarily observed in female children and may be due to beneficial effects of prenatal fish intake.