Fluoride Action Network

Making Sense of the New Studies Associating Fluoride With Harm

Fluoride Action Network | Bulletin | October 18, 2018

The FAN team shall never forget the date September 19, 2017. We had concluded our FAN conference in Washington DC on Sept 18 and we were preparing to journey home. In the early hours of the morning we got the news that a rigorous and high-quality US-government funded study had been published that confirmed our worst fears about fluoride’s ability to impact the mental development of young children. The scientific bombshell was that this harm occurred in the womb! Since then – at least in our circles – the name of the lead author –Bashash- has become a household word. Now just over one year later in October 2018, three more papers have been published in the Environment International and the Environmental Health Perspectives. These include a second paper by Bashash et al.

FAN’s Response

The Fluoride Action Network’s Executive Director, Paul Connett, PhD, has filmed a response to these three papers.  Please click on the link below to watch, then please share the video with local decisionmakers and neighbors.  You can also share FAN’s video post on Facebook.  See video:

(Click on graphic to watch video)

Here are those three papers and a brief explanation why they are important:

Till C, Green R, Grundy JG, Hornung R, Neufeld R, Martinez-Mier A, Ayotte P, Muckle G, Lanphear. Community Water Fluoridation and Urinary Fluoride Concentrations in a National Sample of Pregnant Women in Canada, Environmental Health Perspectives.

In this study (partially funded by the US National Institutes of Health) the urinary levels of fluoride in pregnant mothers was measured in ten large cities in Canada (7 fluoridated, 3 not). The authors found the same range of urinary fluoride levels in the Canadian women as in the Mexican city study (Bashash et al., 2017). The mean values in the fluoridated Canadian communities were almost identical to the Mexican City study (0.91 versus 0.87 ppm). We should note two things a) the large sample size used (N=1566 women) and b) the maternal urinary fluoride (UF) was analyzed exactly the same way as in the Bashash study (i.e. adjusting for urinary creatinine). This allows us to make direct comparisons across the two studies.

This rebuts the simplistic claim by the ADA (issued within a few minutes of the publication of the Bashash study on Sept 19, 2017) that the results were not relevant to the USA.


Bashash M, Merchand M, Hu H, Till C, Martinez-Mier AE, Sanchez BN, Basu N, Peterson K, Green R, Schnaas L, Mercado-Garcia A, Hernandez-Avila M, Tellez-Rojo MM. Prenatal Fluoride Exposure and Attention Deficit Hyperactivity Disorder (ADHD) Symptoms in Children at 6-12 Years of Age in Mexico City. Environmental International.

This study (also partially funded by the US NIH) was done on the same cohort of mother-child pairs as used in the earlier groundbreaking Bashash et al, 2017 IQ study. In this study, 213 Mexican children aged 6-12 who had elevated prenatal (i.e. in utero) exposure to fluoride (as measured in their mothers’ urine) were more likely to show symptoms of ADHD (Attention Deficit and Hyperactivity Disorder) as reported by parents. Prenatal fluoride exposure was more strongly associated with inattentive behaviours and cognitive problems, but not with hyperactivity.  In other words, pre-natal fluoride exposure not only interferes with overall cognitive development (as shown earlier by Bashash et al, 2017), but according to this study may also contribute to symptoms of ADHD.

Bashash controlled for gestational age at birth, birthweight, birth order, sex, maternal marital status, smoking history, age at delivery, education, socioeconomic status and lead exposure. All these factors can influence neurological development.


Malin AJ, Riddell J, McCague H, Till C. The Relationship among Urinary Fluoride, Urinary Iodine and Serum Thyroid Stimulating Hormone Levels among Adults Living in Canada. Environment International.

In this study Ashley Malin and co-workers measured the TSH levels in both men and women in Canada. TSH levels are a measure of underactive thyroid gland. When TSH levels go up they indicate an increased risk of hypothyroidism, which has many serious health implications. The study used health-related data from a nationally representative sample of about 1000 Canadian adults, age 18 to 79 years.  For each participant, blood TSH and urinary fluoride levels were measured. The study consisted of 6,914,124 adults between the ages of 18 and 79 years. Adults who were diagnosed with a thyroid disorder, or who were on thyroid medication, as well as pregnant women were excluded.  These exclusion criteria are important because they deliberately excluded those who are likely most vulnerable to effects of fluoride.  Also, it Is important to note that ~40% of the sample lived in communities that were fluoridated (meaning that most of the sample (~60% ) were exposed to only low levels of fluoride in their drinking water.

Malin et al. did not find a relationship between fluoride exposure and increased TSH levels among the general population, but they did find a relationship with people who already some iodine deficiency. Specifically, they reported that:

“An increase of 1 mg of urinary fluoride (specific gravity adjusted) was associated with a 0.35 mIU TSH/liter among adults with moderate-to-severe iodine deficiency.”

In other words, fluoride exposure appears to exacerbate the condition of hypoactivity for people with low iodine intake. Malin controlled for age, sex, body mass, as well as calcium levels in blood all of which can influence TSH levels.

It was striking to find how common iodine deficiency is among adults in Canada (and US). In the current study, almost 18 per cent of adults fell in the moderately-to-severely iodine deficient range.

This mimics an important result found in 1991 by Lin et al, where it was found that modest exposure to fluoride (0.9 ppm) further lowered the IQ of offspring from mothers with iodine deficiency. Note there is a strong relationship between hypothyroidism in the mother and lowered IQ in their offspring. (See a discussion of this in the presentation given by Dr. Vyvyan Howard on Oct 6, 2018 at Otago University, NZ.)

This study builds upon the substantial evidence that fluoride exposure can impact thyroid function in some individuals, including at “optimal levels.”

See news coverage of these studies.

Paul Connett, PhD
Exective Director
Fluoride Action Network

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