Major US study shows fluoride lowers IQ

A new study from the USA confirms that prenatal exposure to fluoride in water, at levels lower than is used for fluoridation in New Zealand, causes IQ loss at a comparable rate to that found by high-quality North American studies carried out in recent years. Importantly it confirms that harm
is not restricted to levels above 1.5 mg/l, the WHO upper limit, which was an uncertainty at the time of the US Government’s National Toxicology Program’s review published in 2024.

This is the 90^th study, out of a total of 101 human studies, that has found fluoride affects neurological development. It studied significantly more children than earlier studies.

Where these earlier North American such as studies by Green, Till, and Grandjean found a linear relationship, this new study proposes that harm begins at 0.675 mg/l (NZ fluoridates at 0.7-1 mg/litre). However, this proposed threshold is not certain from the study design. It reflects a point chosen by the researchers to use in their modelling.

It could well be that there is actually a broadly continuous relationship between fluoride exposure and cognition, as suggested by Green and Grandjean, and that this new study’s piecewise model is simply approximating a gradual curve with a statistical “bend” around 0.675 mg/L.

It cannot continue to be claimed by the New Zealand Ministry of Health, or other fluoridation
promoters, that fluoride’s neurological harm only occurs at higher levels than we experience in New Zealand or that studies showing harm are only from places such as China. 

There are now 15 studies that have been conducted in the US, Canada or Mexico with most of them funded by the US National Institutes of Health (including this latest one). These are all high-quality studies amounting to more research, of better quality, showing the same level of harm
that was found with lead before it was phased out in the US in 1980 and stopped in New Zealand in 1996.

About 40% and 60% of the Canadian and US population respectively, are supplied fluoridated water. There is no fluoridation in the whole of continental Europe. New Zealand is one of only
three countries with mandatory fluoridation.