Chemical Found in Drinking Water Linked to Tooth Decay in Children

Children with higher concentrations of a certain chemical in their blood are more likely to get cavities, according to a new study by West Virginia University School of Dentistry researchers.

Manufactured chemical groups called perfluoroalkyl and polyfluoroalkyl substances are universal as a result of extensive manufacturing and use. Although manufacturers no longer use PFAS to make nonstick cookware, carpet, cardboard and other products, they persist in the environment. Scientists have linked them to a range of health problems–from heart disease to high cholesterol–but now R. Constance Wiener and Christopher Waters are exploring how they affect dental health.

They investigated whether higher concentrations of PFAS were associated with greater tooth decay in children. One of them–perfluorodecanoic acid–was linked to dental cavities. Their findings appear in the Journal of Public Health Dentistry.

“Due to the strong chemical bonds of PFAS, it is difficult for them to breakdown, which makes them more likely to be persistent within the environment, especially in drinking water systems,” said Waters, who directs the School of Dentistry’s research labs. “A majority of people may not be aware that they are using water and other products that contain PFAS.”

The 629 children who participated in the study were 3 to 11 years old and were part of the National Health and Nutrition Examination Survey. Samples of the children’s blood were analyzed for PFAS in 2013 and 2014. Their tooth decay and other factors–such as their race, their BMI and how often they brushed their teeth–were assessed.

Of the seven PFAS that Wiener and Waters analyzed, perfluorodecanoic acid was the one that correlated with higher levels of tooth decay.

“Perfluorodecanoic acid, in particular, has a long molecular structure and strong chemical bonds; therefore, it remains in the environment longer. As a result, it is more likely to have negative health consequences such as dental caries,” said Dr. Wiener, an associate professor in the Department of Dental Practice and Rural Health.

But how does that influence happen? Wiener and Waters have a hypothesis. According to other research, perfluorodecanoic acid may disrupt the healthy development of enamel, which is what makes teeth hard. That disruption can leave teeth susceptible to decay.

However, when it comes to cavities, scientists haven’t parsed perfluorodecanoic acid’s mechanism of action yet. The topic warrants further investigation.

“While the findings of this study are important, there are some study limitations, and more work is needed to fully understand how this molecule impacts normal tooth formation,” said Fotinos Panagakos, the School of Dentistry’s vice dean for administration and research.

“The good news is that, in our study, about half of the children did not have any measurable amount of PFAS. Perhaps this is due to certain PFAS no longer being made in the US,” Wiener said.

Another piece of good news is that the study reaffirmed the importance of dental hygiene and checkups. Children who brushed once a day or less frequently had significantly higher tooth decay than those who brushed at least twice daily.

Likewise, children who had not been to the dentist within the previous year were twice as likely to have higher rates of tooth decay than kids who hadn’t.

So, even though parents cannot control what is in their children’s drinking water, they can still protect their children’s teeth by fostering thorough, regular brushing and scheduling dental exams.

The School of Dentistry will hold Give Kids a Smile Day on Friday, Feb. 7, at the Pediatric Dentistry Clinic. Dental students will treat more than 100 children for free that day. Each visit includes an exam, a cleaning, a fluoride treatment and–if appropriate–X-rays.

Source: https://www.eurekalert.org/pub_releases/2020-02/wvu-cfi020620.php

EPA Announces it Will Stop Monitoring Drinking Water for Atrazine

Fox News host Tucker Carlson blasted the Environmental Protection Agency over its decision to stop monitoring the dangerous herbicide known as Atrazine in the U.S. water supply.

“Despite its name, the Environmental Protection Agency doesn’t just exist to protect the environment,” Carlson said Friday. “It also exists to protect you, by policing against the many pollutants that are generated by modern life. But soon, the EPA will be doing a little bit less to protect you, and a little bit more to protect Big Agriculture.”

“Buried within a recent 60-page regulatory document, the EPA has announced it will soon end its Atrazine monitoring program, which tests drinking water to make sure that atrazine levels are safe.”

“Atrazine is a pesticide,” the Fox News host continued. “It’s the second most-common one in the U.S. Half of America’s corn crop is treated with it.”

“For newborn boys, atrazine exposure in utero is correlated with lower birth weight, undescended testicles, and deformities to sex organs,” he said.

Despite the fact that “30 million Americans had measurable amounts” of Atrazine found in their water systems, the EPA will now allow 50% more of the herbicide to enter the U.S. water supply at the behest of Big Agriculture.

“For the EPA, that’s not a concern,” the Fox News host concluded. “Their concern, is corn.”

And as Alex Jones has explained, Atrazine’s dangerous effects have been measured in certain frog populations which became hermaphroditic or otherwise refused to mate with the opposite sex when exposed to the chemical.

Study Says Even ‘Safe’ Drinking Water Poses Cancer Risk

A new report from an environmental advocacy watchdog group cautions that carcinogenic products in tap water may altogether increase cancer risk for thousands of U.S. residents over a lifetime.

In a peer-reviewed study published in the journal Heliyon Thursday, the Environmental Working Group (EWG) found that 22 carcinogens commonly found in tap water — including arsenic, byproducts of water disinfectants and radionuclides such as uranium and radium — could cumulatively result in over 100,000 cancer cases over the span of a lifetime.

Although most tap water meets legal standards set by the federal government, EWG researchers found that contaminates present in tap water create a measurable risk for cancer.

“The vast majority of community water systems meet legal standards,” said Olga Naidenko, the vice president for science investigations at EWG, in a statement. “Yet the latest research shows that contaminants present in the water at those concentrations — perfectly legal — can still harm human health.”

An earlier study conducted by EWG found that a cumulative analysis of contaminants in California tap water found heightened risk of cancer for 15,000.

Experts say that the risk of these carcinogens have been under debate for decades. They caution that the standards set for community water systems, which are regulated nationally by the Environmental Protection Agency (EPA), are complicated and require a balance between cost and safety.

Tap water not as safe as you think

The study, funded by the Park Foundation, compiled a list of 22 contaminants with carcinogenic risks present in 48,363 community water systems in the United States, which EWG estimates serve about 86% of the U.S. population. Based on a cumulative risk assessment, EWG found that per 10,000 people, four will have cancer over the span of the lifetime due to the contaminants in water.

“Drinking water contains complex mixtures of contaminants, yet government agencies currently assess the health hazards of tap water pollutants one by one,” said Sydney Evans, the lead author of the paper, in a statement. “In the real world, people are exposed to combinations of chemicals, so it is important that we start to assess health impacts by looking at the combined effects of multiple pollutants.”

The majority of water systems, they add, are in compliance with EPA standards. The EPA, in a statement to USA TODAY, said that legal limits are set for over 90 contaminants in drinking water.

EWG said that 87% of the cancer risk present in tap water comes from arsenic and byproducts of common disinfectants.

Long-term exposure to arsenic, per the World Health Organization, can cause skin cancer, as well as cancer of the bladder and the lungs. Meanwhile, byproducts of disinfectants have been classified by the NIH and EPA as known and possible human carcinogens that can cause liver and bladder cancer.

This study does not take into account the possible contaminants present in groundwater from private wells, nor does it take into account the heightened risk of carcinogens in vulnerable populations such as infants and children.

Clean water is complicated

In recent years, multiple crises, from Newark, New Jersey to Flint, Michigan have revealed the complications and failures in the management of public water systems, from the different water sources used by municipalities to the pipes that deliver water to homes.

The EPA regulates public drinking water under the Safe Drinking Water Act, which was enacted in 1974. It requires the EPA to set standards for contaminants through the National Primary Drinking Water Regulations, which minimizes risk for contaminants.

A spokesperson with the EPA told USA TODAY that water regulations focus primarily on the contaminants that may cause the greatest public health risk.

The standard is splintered into two categories: the maximum contaminant level (MCL), which is enforceable by law and is less stringent, and the maximum contaminant level goal (MCLG), which is only a public health guideline.

For instance, the federally-mandated MCLG for arsenic is 0 micrograms per liter; however, the MCL is 10 micrograms per liter. Meanwhile, the EWG recommends that only four ten-thousandths of a microgram (0.0004 micrograms) of arsenic be allowed in water.

Prof. David Sedlak, a professor of environmental engineering at University of California, Berkeley, and the deputy director of the National Science Foundation-funded urban water research center ReNUWIt, says that regulations for drinking water in the United States are based on a complex balance between health risks from possible carcinogens and the cost of implementing new water cleaning systems.

Sedlak, who is not affiliated with the EWG study, told USA TODAY that arsenic and carcinogenic radionucleides such as radium are both naturally occurring in water systems. Setting the levels of regulation for these carcinogens especially challenging.

“For disinfectants,” he said, “they’ve been in scrutiny over the decades and it’s part of the reason why many cities have switched from chlorine to ozone.”

The Water Research Center says that using ozone water treatment in lieu of chlorine reduces the risk of chemicals leaching into water supplies.

What can be done?

EWG suggests installing a water filter that can remove contaminants found in an individual water source, but some suggested by the group that specifically remove arsenic can cost hundreds or thousands of dollars to purchase and install.

On a broader scale, experts advise solutions aimed at reducing the level of contaminants that are present in tap water.

“We need to prioritize source water protection, to make sure that these contaminants don’t get into the drinking water supplies to begin with,” Naidenko said in a statement.

Sedlak told USA TODAY that the technologies to remove carcinogenic substances from water do, in fact, exist. The biggest hurdle to implementing them, he said, is that they can be costly.

‘Is the Earth unique?’: First water detected on potentially ‘habitable’ planet

“Typically,” he said to USA TODAY, “these additional treatment processes are paid for by consumers — and in many cases, members of the public have been unwilling to see large rate increases in their water bills.”

The EPA agrees. In a handout on the EPA website explaining the Safe Drinking Water Act, it explains that water systems in America rely on community members to ensure that local water suppliers keep their water safe.

“The public is responsible for helping local water suppliers to set priorities, make decisions on funding and system improvements, and establish programs to protect drinking water sources,” the EPA writes.

“If people are aware of the health impacts (of tap water), they might be willing to pay more for water treatment,” said Sedlak. “But at this point, the EPA has made their decision.”

Source: USA Today

Study Links Fluoridated Water During Pregnancy to Lower IQs

Key Points

Question Is maternal fluoride exposure during pregnancy associated with childhood IQ in a Canadian cohort receiving optimally fluoridated water?

Findings In this prospective birth cohort study, fluoride exposure during pregnancy was associated with lower IQ scores in children aged 3 to 4 years.

Meaning Fluoride exposure during pregnancy may be associated with adverse effects on child intellectual development, indicating the possible need to reduce fluoride intake during pregnancy.

Abstract

Importance The potential neurotoxicity associated with exposure to fluoride, which has generated controversy about community water fluoridation, remains unclear.

Objective To examine the association between fluoride exposure during pregnancy and IQ scores in a prospective birth cohort.

Design, Setting, and Participants This prospective, multicenter birth cohort study used information from the Maternal-Infant Research on Environmental Chemicals cohort. Children were born between 2008 and 2012; 41% lived in communities supplied with fluoridated municipal water. The study sample included 601 mother-child pairs recruited from 6 major cities in Canada; children were between ages 3 and 4 years at testing. Data were analyzed between March 2017 and January 2019.

Exposures Maternal urinary fluoride (MUFSG), adjusted for specific gravity and averaged across 3 trimesters available for 512 pregnant women, as well as self-reported maternal daily fluoride intake from water and beverage consumption available for 400 pregnant women.

Main Outcomes and Measures Children’s IQ was assessed at ages 3 to 4 years using the Wechsler Primary and Preschool Scale of Intelligence-III. Multiple linear regression analyses were used to examine covariate-adjusted associations between each fluoride exposure measure and IQ score.

Results Of 512 mother-child pairs, the mean (SD) age for enrollment for mothers was 32.3 (5.1) years, 463 (90%) were white, and 264 children (52%) were female. Data on MUFSG concentrations, IQ scores, and complete covariates were available for 512 mother-child pairs; data on maternal fluoride intake and children’s IQ were available for 400 of 601 mother-child pairs. Women living in areas with fluoridated tap water (n = 141) compared with nonfluoridated water (n = 228) had significantly higher mean (SD) MUFSG concentrations (0.69 [0.42] mg/L vs 0.40 [0.27] mg/L; P = .001; to convert to millimoles per liter, multiply by 0.05263) and fluoride intake levels (0.93 [0.43] vs 0.30 [0.26] mg of fluoride per day; P = .001). Children had mean (SD) Full Scale IQ scores of 107.16 (13.26), range 52-143, with girls showing significantly higher mean (SD) scores than boys: 109.56 (11.96) vs 104.61 (14.09); P = .001. There was a significant interaction (P = .02) between child sex and MUFSG (6.89; 95% CI, 0.96-12.82) indicating a differential association between boys and girls. A 1-mg/L increase in MUFSG was associated with a 4.49-point lower IQ score (95% CI, −8.38 to −0.60) in boys, but there was no statistically significant association with IQ scores in girls (B = 2.40; 95% CI, −2.53 to 7.33). A 1-mg higher daily intake of fluoride among pregnant women was associated with a 3.66 lower IQ score (95% CI, −7.16 to −0.14) in boys and girls.

Conclusions and Relevance In this study, maternal exposure to higher levels of fluoride during pregnancy was associated with lower IQ scores in children aged 3 to 4 years. These findings indicate the possible need to reduce fluoride intake during pregnancy.

Introduction

For decades, community water fluoridation has been used to prevent tooth decay. Water fluoridation is supplied to about 66% of US residents, 38% of Canadian residents, and 3% of European residents.1 In fluoridated communities, fluoride from water and beverages made with tap water makes up 60% to 80% of daily fluoride intake in adolescents and adults.2

Fluoride crosses the placenta,3 and laboratory studies show that it accumulates in brain regions involved in learning and memory4 and alters proteins and neurotransmitters in the central nervous system.5 Higher fluoride exposure from drinking water has been associated with lower children’s intelligence in a meta-analysis6 of 27 epidemiologic studies and in studies7,8 including biomarkers of fluoride exposure. However, most prior studies were cross-sectional and conducted in regions with higher water fluoride concentrations (0.88-31.6 mg/L; to convert to millimoles per liter, multiply by 0.05263) than levels considered optimal (ie, 0.7 mg/L) in North America.9 Further, most studies did not measure exposure during fetal brain development. In a longitudinal birth cohort study involving 299 mother-child pairs in Mexico City, Mexico, a 1-mg/L increase in maternal urinary fluoride (MUF) concentration was associated with a 6-point (95% CI, −10.84 to −1.74) lower IQ score among school-aged children.10 In this same cohort, MUF was also associated with more attention-deficit/hyperactivity disorder–like symptoms.11 Urinary fluoride concentrations among pregnant women living in fluoridated communities in Canada are similar to concentrations among pregnant women living in Mexico City.12 However, it is unclear whether fluoride exposure during pregnancy is associated with cognitive deficits in a population receiving optimally fluoridated water.

This study examined whether exposure to fluoride during pregnancy was associated with IQ scores in children in a Canadian birth cohort in which 40% of the sample was supplied with fluoridated municipal water.

Methods

Study Cohort

Between 2008 and 2011, the Maternal-Infant Research on Environmental Chemicals (MIREC) program recruited 2001 pregnant women from 10 cities across Canada. Women who could communicate in English or French, were older than 18 years, and were within the first 14 weeks of pregnancy were recruited from prenatal clinics. Participants were not recruited if there was a known fetal abnormality, if they had any medical complications, or if there was illicit drug use during pregnancy. Additional details are in the cohort profile description.13

A subset of 610 children in the MIREC Study was evaluated for the developmental phase of the study at ages 3 to 4 years; these children were recruited from 6 of 10 cities included in the original cohort: Vancouver, Montreal, Kingston, Toronto, Hamilton, and Halifax. Owing to budgetary restraints, recruitment was restricted to the 6 cities with the most participants who fell into the age range required for the testing during the data collection period. Of the 610 children, 601 (98.5%) completed neurodevelopmental testing; 254 (42.3%) of these children lived in nonfluoridated regions and 180 (30%) lived in fluoridated regions; for 167 (27.7%) fluoridation status was unknown owing to missing water data or reported not drinking tap water (Figure 1).

This study was approved by the research ethics boards at Health Canada, York University, and Indiana University. All women signed informed consent forms for both mothers and children.

Maternal Urinary Fluoride Concentration

We used the mean concentrations of MUF measured in urine spot samples collected across each trimester of pregnancy at a mean (SD) of 11.57 (1.57), 19.11 (2.39), and 33.11 (1.50) weeks of gestation. Owing to the variability of urinary fluoride measurement and fluoride absorption during pregnancy,14 we only included women who had all 3 urine samples. In our previous work, these samples were moderately correlated; intraclass correlation coefficient (ICC) ranged from 0.37 to 0.40.12

Urinary fluoride concentration was analyzed at the Indiana University School of Dentistry using a modification of the hexamethyldisiloxane (Sigma Chemical Co) microdiffusion procedure15 and described in our previous work.12 Fluoride concentration could be measured to 0.02 mg/L. We excluded 2 samples (0.002%) because the readings exceeded the highest concentration standard (5 mg/L) and there was less certainty of these being representative exposure values.

To account for variations in urine dilution at the time of measurement, we adjusted MUF concentrations for specific gravity (SG) using the following equation: MUFSG = MUFi × (SGM-1)/(SGi-1), where MUFSG is the SG-adjusted fluoride concentration (in milligrams of fluoride per liter), MUFi is the observed fluoride concentration, SGi is the SG of the individual urine sample, and SGM is the median SG for the cohort.16 For comparison, we also adjusted MUF using the same creatinine adjustment method that was used in the 2017 Mexican cohort.10

Water Fluoride Concentration

Water treatment plants measured fluoride levels daily if fluoride was added to municipal drinking water and weekly or monthly if fluoride was not added to water.12 We matched participants’ postal codes with water treatment plant zones, allowing an estimation of water fluoride concentration for each woman by averaging water fluoride concentrations (in milligrams per liter) during the duration of pregnancy. We only included women who reported drinking tap water during pregnancy.

Daily Fluoride Intake in Mothers

We obtained information on consumption of tap water and other water-based beverages (tea and coffee) from a self-report questionnaire completed by mothers during the first and third trimesters. This questionnaire was used in the original MREC cohort and has not been validated. Also, for this study, we developed methods to estimate and calculate fluoride intake that have not yet been validated. To estimate fluoride intake from tap water consumed per day (milligrams per day), we multiplied each woman’s consumption of water and beverages by her water fluoride concentration (averaged across pregnancy) and multiplied by 0.2 (fluoride content for a 200-mL cup). Because black tea contains a high fluoride content (2.6 mg/L),17,18 we also estimated the amount of fluoride consumed from black tea by multiplying each cup of black tea by 0.52 mg (mean fluoride content in a 200-mL cup of black tea made with deionized water) and added this to the fluoride intake variable. Green tea also contains varying levels of fluoride; therefore, we used the mean for the green teas listed by the US Department of Agriculture (1.935 mg/L).18 We multiplied each cup of green tea by 0.387 mg (fluoride content in a 200-mL cup of green tea made with deionized water) and added this to the fluoride intake variable.

Primary Outcomes

We assessed children’s intellectual abilities with the Wechsler Preschool and Primary Scale of Intelligence, Third Edition. Full Scale IQ (FSIQ), a measure of global intellectual functioning, was the primary outcome. We also assessed verbal IQ (VIQ), representing verbal reasoning and comprehension, and performance IQ (PIQ), representing nonverbal reasoning, spatial processing, and visual-motor skills.

Covariates

We selected covariates from a set of established factors associated with fluoride metabolism (eg, time of void and time since last void) and children’s intellectual abilities (eg, child sex, maternal age, gestational age, and parity) (Table 1). Mother’s race/ethnicity was coded as white or other, and maternal education was coded as either bachelor’s degree or higher or trade school diploma or lower. The quality of a child’s home environment was measured by the Home Observation for Measurement of the Environment (HOME)–Revised Edition19 on a continuous scale. We also controlled for city and, in some models, included self-reported exposure to secondhand smoke (yes/no) as a covariate.

Statistical Analyses

In our primary analysis, we used linear regression analyses to estimate the associations between our 2 measures of fluoride exposure (MUFSG and fluoride intake) and children’s FSIQ scores. In addition to providing the coefficient corresponding to a 1-mg difference in fluoride exposure, we also estimated coefficients corresponding to a fluoride exposure difference spanning the 25th to 75th percentile range (which corresponds to a 0.33 mg/L and 0.62 mg F/d difference in MUFSG and fluoride intake, respectively) as well as the 10th to 90th percentile range (which corresponds to a 0.70 mg/L and 1.04 mg F/d difference in MUFSG and fluoride intake, respectively).

We retained a covariate in the model if its P value was less than .20 or its inclusion changed the regression coefficient of the variable associated factor by more than 10% in any of the IQ models. Regression diagnostics confirmed that there were no collinearity issues in any of the IQ models with MUFSG or fluoride intake (variance inflation factor <2 for all covariates). Residuals from each model had approximately normal distributions, and their Q-Q plots revealed no extreme outliers. Plots of residuals against fitted values did not suggest any assumption violations and there were no substantial influential observations as measured by Cook distance. Including quadratic or natural-log effects of MUFSG or fluoride intake did not significantly improve the regression models. Thus, we present the more easily interpreted estimates from linear regression models. Additionally, we examined separate models with 2 linear splines to test whether the MUFSG association significantly differed between lower and higher levels of MUFSG based on 3 knots, which were set at 0.5 mg/L (mean MUFSG), 0.8 mg/L (threshold seen in the Mexican birth cohort),10 and 1 mg/L (optimal concentration in the United States until 2015).20 For fluoride intake, knots were set at 0.4 mg (mean fluoride intake), 0.8 mg, and 1 mg (in accordance with MUFSG). We also examined sex-specific associations in all models by testing the interactions between child sex and each fluoride measure.

In sensitivity analyses, we tested whether the associations between MUFSG and IQ were confounded by maternal blood concentrations of lead,21 mercury,21 manganese,21,22 perfluoro-octanoic acid,23 or urinary arsenic.24 We also conducted sensitivity analyses by removing IQ scores that were greater than or less than 2.5 standard deviations from the sample mean. Additionally, we examined whether using MUF adjusted for creatinine instead of SG affected the results.

In additional analyses, we examined the association between our 2 measures of fluoride exposure (MUFSG and fluoride intake) with VIQ and PIQ. Additionally, we examined whether water fluoride concentration was associated with FSIQ, VIQ, and PIQ scores.

For all analyses, statistical significance tests with a type I error rate of 5% were used to test sex interactions, while 95% confidence intervals were used to estimate uncertainty. Analyses were conducted using R software (the R Foundation).25 The P value level of significance was .05, and all tests were 2-sided.

Results

For the first measure of fluoride exposure, MUFSG, 512 of 601 mother-child pairs (85.2%) who completed the neurodevelopmental visit had urinary fluoride levels measured at each trimester of the mother’s pregnancy and complete covariate data (Figure 1); 89 (14.8%) were excluded for missing MUFSG at 1 or more trimesters (n = 75) or missing 1 or more covariates included in the regression (n = 14) (Figure 1). Of the 512 mother-child pairs with MUFSG data (and all covariates), 264 children were female (52%).

For the second measure of fluoride exposure, fluoride intake from maternal questionnaire, data were available for 400 of the original 601 mother-child pairs (66.6%): 201 women (33.4%) were excluded for reporting not drinking tap water (n = 59), living outside of the predefined water treatment plant zone (n = 108), missing beverage consumption data (n = 20), or missing covariate data (n = 14) (Figure 1).

Children had mean FSIQ scores in the average range (population normed) (mean [SD], 107.16 [13.26], range = 52-143), with girls (109.56 [11.96]) showing significantly higher scores than boys (104.61 [14.09]; P < .001) (Table 1). The demographic characteristics of the 512 mother-child pairs included in the primary analysis were not substantially different from the original MIREC cohort or subset of mother-child pairs without 3 urine samples (eTable 1 in the Supplement). Of the 400 mother-child pairs with fluoride intake data (and all covariates), 118 of 238 (50%) in the group living in a nonfluoridated region were female and 83 of 162 (51%) in the group living in a fluoridated region were female.

Fluoride Measurements

The median MUFSG concentration was 0.41 mg/L (range, 0.06-2.44 mg/L). Mean MUFSG concentration was significantly higher among women (n = 141) who lived in communities with fluoridated drinking water (0.69 [0.42] mg/L) compared with women (n=228) who lived in communities without fluoridated drinking water (0.40 [0.27] mg/L; P < .001) (Table 1; Figure 2).

The median estimated fluoride intake was 0.39 mg per day (range, 0.01-2.65 mg). As expected, the mean (SD) fluoride intake was significantly higher for women (162 [40.5%]) who lived in communities with fluoridated drinking water (mean [SD], 0.93 [0.43] mg) than women (238 [59.5%]) who lived in communities without fluoridated drinking water (0.30 [0.26] mg; P < .001) (Table 1; Figure 2). The MUFSG was moderately correlated with fluoride intake (r = 0.49; P < .001) and water fluoride concentration (r = 0.37; P < .001).

Maternal Urinary Fluoride Concentrations and IQ

Before covariate adjustment, a significant interaction (P for interaction = .03) between MUFSG and child sex (B = 7.24; 95% CI, 0.81- 13.67) indicated that MUFSG was associated with FSIQ in boys; an increase of 1 mg/L MUFSG was associated with a 5.01 (95% CI, −9.06 to −0.97; P = .02) lower FSIQ score in boys. In contrast, MUFSG was not significantly associated with FSIQ score in girls (B = 2.23; 95% CI, −2.77 to 7.23; P = .38) (Table 2).

Adjusting for covariates, a significant interaction (P for interaction = .02) between child sex and MUFSG (B = 6.89; 95% CI, 0.96-12.82) indicated that an increase of 1 mg/L of MUFSG was associated with a 4.49 (95% CI, −8.38 to −0.60; P = .02) lower FSIQ score for boys. An increase from the 10th to 90th percentile of MUFSG was associated with a 3.14 IQ decrement among boys (Table 2; Figure 3). In contrast, MUFSG was not significantly associated with FSIQ score in girls (B = 2.43; 95% CI, −2.51 to 7.36; P = .33).

Estimated Fluoride Intake and IQ

A 1-mg increase in fluoride intake was associated with a 3.66 (95% CI, −7.16 to −0.15; P = .04) lower FSIQ score among boys and girls (Table 2; Figure 3). The interaction between child sex and fluoride intake was not statistically significant (B = 1.17; 95% CI, −4.08 to 6.41; P for interaction = .66).

Sensitivity Analyses

Adjusting for lead, mercury, manganese, perfluorooctanoic acid, or arsenic concentrations did not substantially change the overall estimates of MUFSG for boys or girls (eTable 2 in the Supplement). Use of MUF adjusted for creatinine did not substantially alter the associations with FSIQ (eTable 2 in the Supplement). Including time of void and time since last void did not substantially change the regression coefficient of MUFSG among boys or girls.

Estimates for determining the association between MUFSG and PIQ showed a similar pattern with a statistically significant interaction between MUFSG and child sex (P for interaction = .007). An increase of 1 mg/L MUFSG was associated with a 4.63 (95% CI, −9.01 to −0.25; P = .04) lower PIQ score in boys, but the association was not statistically significant in girls (B = 4.51; 95% CI, −1.02 to 10.05; P = .11). An increase of 1 mg/L MUFSG was not significantly associated with VIQ in boys (B = −2.85; 95% CI, −6.65 to 0.95; P = .14) or girls (B = 0.55; 95% CI, −4.28 to 5.37; P = .82); the interaction between MUFSG and child sex was not statistically significant (P for interaction = .25) (eTable 3 in the Supplement).

Consistent with the findings on estimated maternal fluoride intake, increased water fluoride concentration (per 1 mg/L) was associated with a 5.29 (95% CI, −10.39 to −0.19) lower FSIQ score among boys and girls and a 13.79 (95% CI, −18.82 to −7.28) lower PIQ score (eTable 4 in the Supplement).

Discussion

Using a prospective Canadian birth cohort, we found that estimated maternal exposure to higher fluoride levels during pregnancy was associated with lower IQ scores in children. This association was supported by converging findings from 2 measures of fluoride exposure during pregnancy. A difference in MUFSG spanning the interquartile range for the entire sample (ie, 0.33 mg/L), which is roughly the difference in MUFSG concentration for pregnant women living in a fluoridated vs a nonfluoridated community, was associated with a 1.5-point IQ decrement among boys. An increment of 0.70 mg/L in MUFSG concentration was associated with a 3-point IQ decrement in boys; about half of the women living in a fluoridated community have a MUFSG equal to or greater than 0.70 mg/L. These results did not change appreciably after controlling for other key exposures such as lead, arsenic, and mercury.

To our knowledge, this study is the first to estimate fluoride exposure in a large birth cohort receiving optimally fluoridated water. These findings are consistent with that of a Mexican birth cohort study that reported a 6.3 decrement in IQ in preschool-aged children compared with a 4.5 decrement for boys in our study for every 1 mg/L of MUF.10 The findings of the current study are also concordant with ecologic studies that have shown an association between higher levels of fluoride exposure and lower intellectual abilities in children.7,8,26 Collectively, these findings support that fluoride exposure during pregnancy may be associated with neurocognitive deficits.

In contrast with the Mexican study,10 the association between higher MUFSG concentrations and lower IQ scores was observed only in boys but not in girls. Studies of fetal and early childhood fluoride exposure and IQ have rarely examined differences by sex; of those that did, some reported no differences by sex.10,27-29 Most rat studies have focused on fluoride exposure in male rats,30 although 1 study31 showed that male rats were more sensitive to neurocognitive effects of fetal exposure to fluoride. Testing whether boys are potentially more vulnerable to neurocognitive effects associated with fluoride exposure requires further investigation, especially considering that boys have a higher prevalence of neurodevelopmental disorders such as ADHD, learning disabilities, and intellectual disabilities.32 Adverse effects of early exposure to fluoride may manifest differently for girls and boys, as shown with other neurotoxicants.33-36

The estimate of maternal fluoride intake during pregnancy in this study showed that an increase of 1 mg of fluoride was associated with a decrease of 3.7 IQ points across boys and girls. The finding observed for fluoride intake in both boys and girls may reflect postnatal exposure to fluoride, whereas MUF primarily captures prenatal exposure. Importantly, we excluded women who reported that they did not drink tap water and matched water fluoride measurements to time of pregnancy when estimating maternal fluoride intake. None of the fluoride concentrations measured in municipal drinking water were greater than the maximum acceptable concentration of 1.5 mg/L set by Health Canada; most (94.3%) were lower than the 0.7 mg/L level considered optimal.37

Water fluoridation was introduced in the 1950s to prevent dental caries before the widespread use of fluoridated dental products. Originally, the US Public Health Service set the optimal fluoride concentrations in water from 0.7 to 1.2 mg/L to achieve the maximum reduction in tooth decay and minimize the risk of enamel fluorosis.38 Fluorosis, or mottling, is a symptom of excess fluoride intake from any source occurring during the period of tooth development. In 2012, 68% of adolescents had very mild to severe enamel fluorosis.39 The higher prevalence of enamel fluorosis, especially in fluoridated areas,40 triggered renewed concern about excessive ingestion of fluoride. In 2015, in response to fluoride overexposure and rising rates of enamel fluorosis, 39,41,42 the US Public Health Service recommended an optimal fluoride concentration of 0.7 mg/L, in line with the recommended level of fluoride added to drinking water in Canada to prevent caries. However, the beneficial effects of fluoride predominantly occur at the tooth surface after the teeth have erupted.43 Therefore, there is no benefit of systemic exposure to fluoride during pregnancy for the prevention of caries in offspring.44 The evidence showing an association between fluoride exposure and lower IQ scores raises a possible new concern about cumulative exposures to fluoride during pregnancy, even among pregnant women exposed to optimally fluoridated water.

Strengths and Limitations

Our study has several strengths and limitations. First, urinary fluoride has a short half-life (approximately 5 hours) and depends on behaviors that were not controlled in our study, such as consumption of fluoride-free bottled water or swallowing toothpaste prior to urine sampling. We minimized this limitation by using 3 serial urine samples and tested for time of urine sample collection and time since last void, but these variables did not alter our results. Second, although higher maternal ingestion of fluoride corresponds to higher fetal plasma fluoride levels,45 even serial maternal urinary spot samples may not precisely represent fetal exposure throughout pregnancy. Third, while our analyses controlled for a comprehensive set of covariates, we did not have maternal IQ data. However, there is no evidence suggesting that fluoride exposure differs as a function of maternal IQ; our prior study did not observe a significant association between MUF levels and maternal education level.12 Moreover, a greater proportion of women living in fluoridated communities (124 [76%]) had a university-level degree compared with women living in nonfluoridated communities (158 [66%]). Nonetheless, despite our comprehensive array of covariates included, this observational study design could not address the possibility of other unmeasured residual confounding. Fourth, fluoride intake did not measure actual fluoride concentration in tap water in the participant’s home; Toronto, for example, has overlapping water treatment plants servicing the same household. Similarly, our fluoride intake estimate only considered fluoride from beverages; it did not include fluoride from other sources such as dental products or food. Furthermore, fluoride intake data were limited by self-report of mothers’ recall of beverage consumption per day, which was sampled at 2 points of pregnancy, and we lacked information regarding specific tea brand.17,18 In addition, our methods of estimating maternal fluoride intake have not been validated; however, we show construct validity with MUF. Fifth, this study did not include assessment of postnatal fluoride exposure or consumption. However, our future analyses will assess exposure to fluoride in the MIREC cohort in infancy and early childhood.

Conclusions

In this prospective birth cohort study from 6 cities in Canada, higher levels of fluoride exposure during pregnancy were associated with lower IQ scores in children measured at age 3 to 4 years. These findings were observed at fluoride levels typically found in white North American women. This indicates the possible need to reduce fluoride intake during pregnancy.

Source: https://jamanetwork.com/journals/jamapediatrics/fullarticle/2748634

AAAS Rescinds Scientific Freedom Award for Scientists Discovery of Glyphosate’s Role in Chronic Kidney Disease and CEO Announces Retirement

Since 1980, the American Association for the Advancement of Science (AAAS) — the world’s largest scientific society and publisher of several journals, including Science — has presented an annual award for Scientific Freedom and Responsibility to “scientists, engineers or their organizations, whose exemplary actions have demonstrated scientific freedom and responsibility in challenging circumstances.” As explained […]