Fluoride Action Network

Fluoride Action Network | Bulletin | September 21, 2017

The results of the first ever US government funded study of fluoride/IQ have now been published. A team of researchers funded by the National Institutes of Health found that low levels of fluoride exposure during pregnancy are linked to significantly reduced IQ in children, according to a study published on September 19, 2017 in the journal Environmental Health Perspectives.

The study, entitled Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6–12 Years of Age in Mexico, was conducted by a team of scientists from University of Toronto, University of Michigan, Harvard, and McGill, and found:

“…higher levels of maternal urinary fluoride during pregnancy (a proxy for prenatal fluoride exposure) that are in the range of levels of exposure in other general population samples of pregnant women as well as nonpregnant adults were associated with lower scores on tests of cognitive function in the offspring at 4 and 6–12 y old.”

Within hours of it being published, FAN released a video response featuring Chemist and Toxicologist, Professor Paul Connett, PhD.


  1. Share FAN’s Facebook and Twitter posts on social media.
  2. Share FAN’s webpage on the study with friends, family, co-workers;     particularly expecting mothers.
  3. Share the study, the accompanying press release, FAN’s Video, and the Newsweek article with your city councilors and Water Board, urging them to protect the next generation by opposing fluoridation.
More to come…

FAN Comment

The study found a very large and significant effect. An increase in urine fluoride of 1 mg/L was associated with a drop in IQ of 5 to 6 points. Such a drop of IQ in the whole population would half the number of very bright children (IQ greater than 130) and double the number of mentally handicapped (IQ less than 70).

Most of the Mexican women had urine fluoride between 0.5 and 1.5 mg/L. Studies have found that adults in the USA 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 mothers.

This new study had fluoride exposures almost the same as what is found in fluoridating countries like the USA. The paper shows the relationship between urine fluoride and IQ in the graph (Figure 2) reproduced here:

The data in this graph has been adjusted for numerous potential confounding factors like sex, birth weight, gestational age, and whether the mother smoked. Other potential confounders had already been ruled out, including lead, mercury, alcohol consumption during pregnancy, mother’s education, mother’s IQ, and quality of home environment.

FAN has redrawn this graph in simplified form to better illustrate the relationship found between mothers’ urine fluoride and childrens’ IQ.

This simplified version of the graph highlights the range of urine fluoride levels common in women in the USA with the blue text and bracket. When comparing mothers at the low end to those at the high end of this range, the subsequent loss of IQ in their children was 6 points. The light red shaded zone around the relationship line is the 95% Confidence Interval and demonstrates that the relationship is statistically significant across the entire range of fluoride exposures.

Important Points:

1.  The loss of IQ is very large.  The child of a mother who was drinking 1 ppm F water would be predicted to have 5 to 6 IQ points lower than if the mother had drunk water with close to zero F in it.

2.  The study measured urine F, which is usually a better indicator of total F intake than is the concentration of F in drinking water.  When drinking water is the dominant source of F,, urine F and water F are usually about the same.  So, the average urine F level in this study of 0.9 mg/L implies that woman was ingesting the same amount of F as a woman drinking water with 0.9 mg/L F.

3.  The range of F exposures in this study is likely to be very close to the range in a fluoridated area of the United States.  The doses in this study are directly applicable to areas with artificial fluoridation.  There is no need to extrapolate downward from effects at higher doses.  The claims by fluoridation defenders that only studies using much higher doses than occur in areas with artificial fluoridation have shown a loss of IQ are squarely refuted by this study.  Those false claims range from 11 times to 30 times higher, but are based on the logical fallacy that it is the highest dose amongst several studies that is relevant, when it is the LOWEST dose amongst studies that is most relevant.

4.  This study was very carefully done, by a group of researchers who have produced over 50 papers on the cognitive health of children in relationship to environmental exposures.  This was funded by the NIH and was a multi-million dollar study.  This was the group’s first study of fluoride, their other studies mostly dealing with lead, mercury, and other environmental neurotoxicants.

5.  This study controlled for a wide range of potential factors that might have skewed the results and produced a false effect.  It was able to largely rule out confounding by these other factors.  The factors ruled out included Pb, Hg, socio-economic status, smoking, alcohol use, and health problems during pregnancy.

6.  This study offers confirmation of previous less sophisticated studies in Mexico, China and elsewhere.  Some of those studies had higher F exposures than are commonly found in the USA, but many did not.  The sole study in a country with artificial water fluoridation (as opposed to artificial salt fluoridation which was likely a main source of F in this new study) was by Broadbent in New Zealand.  That found no association between water F and IQ and was trumpted by fluoridation defenders.  But that study was shown to have almost no difference in TOTAL F intake between the children with fluoridated water and those with unfluoridated water, since most of the unfluoridated water children were given F supplements.

7.  The study authors are cautious in their conclusions, as is common for scientists.  But the implications of this study are enormous.  A single study will never prove that F lowers IQ at doses found in fluoridated areas, but this is more than a red flag.  It is a cannon shot across the bow of the 80 year old practice of artificial fluoridation.

Key Quotes:

… “This is a very well-conducted study, and it raises serious concerns about fluoride supplementation in water,” says Dr. Leonardo Trasande, a pediatrician who studies potential links between environmental exposures and health problems at New York University Langone Health.

Trasande emphasizes that the levels of fluoride seen among the mothers in this study are slightly higher than what would be expected in U.S., based on current fluoride supplementation levels. However, he also explains that fluoride is known to disrupt thyroid function, which in turn is crucial for brain development.

“These new insights raise concerns that the prenatal period may be highly vulnerable and may require additional reconsideration,” Trasande says.

… Dr. Howard Hu, the study’s lead investigator, and a professor of environmental health, epidemiology and global health at [the University of Toronto’s] Dalla Lana School of Public Health, says the fact that the fluoride levels in the mothers was most predictive of the drop in test scores may be due to the fact that the brains of babies develop so rapidly while they are in utero.

“This is consistent with a growing appreciation in environmental health that the growing fetal nervous system is more sensitive to exposures than a developed nervous system,” he told CTVNews.ca by phone from Sydney.

  • Both the Montreal Gazette & the National Postran the same article: Researchers urge caution over study linking fluoride exposure in pregnancy to lower IQs in children, by Sharon Kirkey, September 21:

… [The article quotes the lead investigator of the study, Dr Howard Hu:] “This is a very rigorous epidemiology study. You just can’t deny it. It’s directly related to whether fluoride is a risk for the neurodevelopment of children. So, to say it has no relevance to the folks in the U.S. seems disingenuous.”

… “Why would anybody rate the equivalency or supremacy of reducing tooth decay by about one cavity a lifetime when what’s at stake is the mental development of your children? It’s utterly preposterous,” said Connett, executive director of the Fluoride Action Network.

Press Releases:

Additional Media Coverage:


Stuart Cooper
Campaign Director
Fluoride Action Network

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