The 6 Mother-Offspring Fluoride Studies
The Mother-Offspring studies reveal that the fetus is the most vulnerable to fluoride’s neurotoxicity. Five the the six studies measured pregnant women’s urinary levels for fluoride and these levels were compared to the IQ of the offspring. Certain levels of fluoride levels in the pregnant women’s urine were found to significantly impact the IQ, or cognitive function, of the offspring at various ages (up to 12 years of age). The largest study listed below by Green et al. (2019) is important as it included mother-offspring pairs in fluoridated and non-fluoridated cities in Canada. Children were tested between the ages of 3 and 4. Of note is that the U.S. fluoridates the drinking water at the same level as Canada (0.7 mg/L fluoride). The Bashash et al. (2017) study is the longest mother-offspring study, having tested the children at 4 years of age and again between 6-12 years. Three other studies (Thomas et al., 2017; Valdez Jiménez et al., 2017; Li et al., 2004) also correlated the urinary fluoride levels with reduced IQ in the offspring. The singular importance of the Green (2019), Bashash (2017) and Thomas (2017) studies is that the fluoride levels in the urine of the pregnant women are similar to what is found in adults living in fluoridated communities in the U.S. The first study to look at this correlation was the study by Li et al. (2004) in China.
The studies by Li et al (2004) and Chang et al., (2017), both from China, compared newborns (1 to 3 days old) and infants (at 3, 6, 9, and 12 months of age) from women living in high-fluoride areas to those living outside these areas. The study by Valdez Jiménez et al. (2017) was confined to women and their offspring in high fluoride areas.
1. Green et al. (2019) reported lower IQ at between 3 and 4 years of age.
Titled Association Between Maternal Fluoride ExposureDuring Pregnancy and IQ Scores in Offspring in Canada, and published in JAMA Pediatrics, this study took place in 6 Canadian cities with 512 mother-child pairs. Women living in areas with fluoridated tap water compared with nonfluoridated water had significantly higher mean urinary fluoride concentrations. A 1-mg/L increase in urinary fluoride levels was associated with a 4.49-point lower IQ score in boys, but there was no statistically significant association with IQ scores in girls. A 1-mg higher daily intake of fluoride among pregnant women was associated with a 3.66 lower IQ score in boys and girls. According to the authors, the urinary fluoride levels observed in this study are “typically found in white North American women.” This study was funded by the U.S. National Institute of Environmental Health Sciences (NIEHS).
2. Bashash et al. (2017) reported lower IQ at 4 years of age and between 6 to 12 years of age.
This study by Bashash et al., titled Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of Age in Mexico, was published in September 2017 in the prestigious journal Environmental Health Perspectives. The researchers followed up to 299 women-offspring pairs in Mexico during a 12-year period and reported that the fluoride levels in the urine of the pregnant women was the factor for a loss of 5 to 6 IQ points in the offspring at ages 4 and 6-12 years of age. The fluoride levels in the urine of the pregnant women are similar to what is found in adults in fluoridated communities in the U.S. This study, as well as the following one by Thomas et al., was funded by the U.S. National Institutes of Health, the U.S. Environmental Protection Agency, and the U.S. NIEHS.
3. Thomas et al. (2018) reported lower IQ in children between 1 to 3 years of age.
This study by Thomas et al., titled, OPV – 2 Prenatal fluoride exposure and neurobehavior among children 1–3 years of age in Mexico, was presented at a conference on epidemiology in Germany in March 2018. Only the abstract of the study has been published in the journal Occupational & Environmental Medicine. This abstract reports pregnant women’s fluoride exposure is linked to lower IQ in their children at one- to three-years-old at levels commonly found in U.S. women. The authors of this study said that their findings “suggest higher in utero exposure to fluoride has an adverse impact on offspring cognitive development that can be detected earlier, in the first three years of life.”
4. Valdez Jiménez et al. (2017) reported lower IQ between the ages of 3 to 15 months.
This was the first mother-infant pair study performed by a team from three universities in Mexico. The study is titled In utero exposure to fluoride and cognitive development delay in infants by Valdez Jiménez et al. and was published in the journal Neurotoxicology on March 1, 2017. This study differs from the other two studies discussed above inasmuch as the pregnant women in the study lived in areas of high naturally occurring fluoride in the drinking water. The authors noted that “cognitive alterations in children born from exposed mothers to F could start in early prenatal stages of life.”
• this study had 65 mother-baby pairs
• the IQ testing took place between the ages of 3 to 15 months
• this study took place in an area with high naturally occurring levels of fluoride in the drinking water (called endemic hydrofluorosis areas).
• Over 81.5% of the samples of tap water were above 1.5 mg/l with the highest value of 12.5 mg/.
• 33.8% of the births were pre-term. The authors stated, “We found higher levels of F in urine across trimester in premature compared with full term.”
• The authors state, “In this study near to 60% of the children consumed contaminated water and the prevalence of children with IQ below 90 points was 25% in the control group (F urine 1.5 mg/g creatinine) in comparison with the 58% of children in the exposed group (F urine >5 mg/g creatinine)… Our data suggests that cognitive alterations in children born from exposed mothers to F could start in early prenatal stages of life.”
5. Li et al. (2004) reported significant differences in the behavioral neurological assessment score in 1 to 3 day-old offspring
This Chinese study, Effects of high fluoride level on neonatal neurobehavioral development, was first published in 2004, translated into English and re-published in 2008 in the journal Fluoride 41(2):165–170.
- Ninety-one full-term, normal neonates were randomly selected for observation, 46 were male and 45 female.
- A urine sample was collected after the pregnant women were hospitalized but before labor began
- The standard neonatal behavioral neurological assessment (NBNA) method was used for measurements, which were carried out by professionals (pediatric department physicians working in neonatal section trained in national NBNA training program)
- In the high fluoride group the urinary fluoride level averaged 3.58±1.47 mg/L, significantly higher than the normal range of 0.18–2.6 mg/L and was significantly different from the fluoride level in urine samples from the control group. When compared with the fluoride result in urine samples from the control group (1.74±0.96 mg/L), the difference is statistically very significant (p<0.01).
- The two study groups are located in the same area with similar climate, living habits, economic and nutritional conditions, and cultural backgrounds. There is no industrial fluoride contamination in the endemic fluoride or the non-endemic control area. As can be seen in Table 1, there was no statistically significant difference in the delivery mode, birth weight, infant length, and sex.
- As seen in Table 2, neonatal neurobehavioural assessment of the neonates from the high fluoride group and the control group indicated that the neurobehavioural capability and agonistic muscle tension from the high fluoride group were impaired, resulting in a statistically significant lower overall (total) assessment score than in the control group (p<0.05).
- Table 3 shows that the various neurobehavioral capabilities, such as non-biological visual, biological visual, and auditory directional reactions of the neonates from the high fluoride group lagged behind those of the control group with differences that are statistically significant (p<0.05).
6. Chang et al. (2017) reported significant differences in the mental development index and psychomotor development index of the offspring at 3, 6, 9, and 12 months of age.
This study, Analysis on the Effect of Coal-Burning Fluorosis on the Physical Development and Intelligence Development of Newborns Delivered by Pregnant Women with Coal-Burning Fluorosis, was conducted in China and published in the Chinese Journal of Control of Endemic Diseases 32(8):872-873.
- • 118 newbors in this study: The Observation Group: 68 newborns from coal-burning high-fluoride areas (called endemic fluorosis areas). The Control Group: 50 full-term newborns delivered by healthy pregnant women.
- The type of test used: Mental development index (MDI) and psychomotor development index (PDI) (assessed using the Standardized Scale for the Intelligence Development of Children formulated by the Children Development Center of China [CDCC]).
- The body weight, body length, head circumference, chest circumference, upper arm circumference and top arm length of newborns in the observation group were all significantly lower than those in the control group, and their differences were statistically significant (P < 0.05).
- At 3, 6, 9 and 12 months after birth, the grades of body weight development and body-length development of infants in the control group were significantly higher than those in the observation group (P < 0.05);
- Both the Mental development index and the psychomotor development index of infants in the observation group were significantly lower than those in the control group (P < 0.05).
- The socioeconomic status of all the three villages were the same in both endemic and control areas.
- The results suggest that maternal exposure to high levels of fluoride have a significant impact on the intelligence development of newborns.
What were the fluoride levels that caused the harm?
Urine tests are a better indicator of daily total fluoride intake than is the concentration of fluoride in the drinking water. Testing urine for fluoride provides one of the best indicators for all exposures to fluoride whether its through ingestion of water and food or through inhalation or even through dermal contact.
The Bashash et al. (2017) study found a very large effect. An increase in urine fluoride of 1 mg/L was associated with a drop in IQ of 5 to 6 points.
To put this into perspective with the fluoride levels ingested by the Mexican mothers and the levels ingested in fluoridated parts of the U.S., the average fluoride intake in the Mexican mothers was about the same as that in women in the U.S. It was not substantially higher. The range of fluoride levels in Mexico also corresponded closely to the range found in most of the U.S. The higher levels were similar to what is found in areas in the U.S. with fluoridated water, and the lower levels were similar to what is found in most unfluoridated parts of the U.S. The national survey of urinary fluoride levels of pregnant women in Canada living in fluoridated and non-fluoridated cities (Till et al. 2018) reported the same.
Most of the Mexican women had urine fluoride between 0.5 and 1.5 mg/L. Studies have found that adults in the U.S. have between about 0.6 and 1.5 mg/L, almost exactly the same range. From the low end of that range to the high end is a difference of 1 mg/L which is what caused the 5 to 6 IQ point difference in the children of the study.
In the latest study by Green et al. (2019) the authors reported that a 1-mg/L increase in urinary fluoride levels was associated with a 4.49-point lower IQ score in boys, but there was no statistically significant association with IQ scores in girls. The authors noted that women living in areas with fluoridated tap water compared with nonfluoridated water had significantly higher mean urinary fluoride levels.
A 2018 national survey of urinary fluoride levels in pregnant women in Canada
This study by Till et al., published on October 11, 2018, found that pregnant women in “optimally” fluoridated Canada have significantly higher levels of fluoride in their urine than women living in non-fluoridated communities. This study also showed that pregnant Canadians had fluoride urinary levels similar to those that reduced IQ in offspring in the study by Bashash et al. (2017). The U.S. NIH-funded Bashash study reported a lowering of 5 to 6 IQ points in the offspring. These findings suggest that the results from Bashash’s Mexico City study may be appliicable to Canada and the U.S. as both countries use 0.7 mg/L fluoride in their fluoridation schemes.
The study: Till C, Green R, Grundy JG, Hornung R, Neufeld R, Martinez-Mier A, Ayotte P, Muckle G, Lanphear. 2018. Community Water Fluoridation and Urinary Fluoride Concentrations in a National Sample of Pregnant Women in Canada, Environmental Health Perspectives.