There is an obvious survival advantage to the emotion of disgust – we should fear putting unhealthy, tainted, contaminated, or poisonous substances into our bodies. Emotions, however, are a double-edged sword. They are an effective evolutionary mechanism for motivating creatures to engage in certain behavior, but they also tend to be crude and undiscriminating – inadequate to deal with our complex modern society.

A dispassionate consideration of objective scientific evidence is the optimal strategy for deciding on which foods and substances are safe to consume, but it is far easier to scare people about toxins than to reassure them with data. We see this frequently with the anti-vaccine movement, and also with anti-fluoridation attitudes. It is easy to scare people with the idea that there are “chemicals” in our drinking water.

One company, San Diego Pure Water, seems to have made such scaremongering into a marketing strategy. Their website is full of articles and videos claiming that fluoride is the “the greatest fraud that has ever been perpetrated.”

Let’s take a look at their specific claims. They claim:

Fluoride may lower a child’s IQ according to 24 independent studies that have reported an association between fluoride exposure and reduced IQ.

They don’t provide the 24 references, however. The notion that 24 studies support the claim that fluoridation reduces IQ is little more than an urban legend passing around anti-fluoride sites. If you follow the links, when present, they simply refer to other anti-fluoride sites making the same claims.

There are studies looking at the relationship between fluoride and IQ. A recent review and meta-analysis published by Harvard researchers actually reviewed 27 such studies.  They concluded that there is a relationship between high fluoride exposure and lower IQ. However – the studies largely compared high levels of exposure that exceed EPA limits, to low levels of exposure that are at the level of fluoride added to some public water supplies and within the safety range set by the EPA.

So, if anything this meta-analysis demonstrated that the levels of fluoride in the US drinking water supply are safe and associated with a higher IQ.

Toxicity is always about dose. There is no evidence that the level of fluoride in US drinking water poses a significant health risk or lowers IQ. The quoted studies refer to higher levels of fluoride that are considered above the safe limit, and therefore their findings are not applicable to drinking water. Still, it may be effective marketing to use such studies to scaremonger about fluoride in order to sell water filters.

Another claim made on the site is that:

Fluoride accumulates in the body according to the National Research Council “it is apparent that fluorides interfere with brain functions,” and it adds to the formation of beta-amyloid deposits which are associated with Alzheimer’s.

They further argue that fluoride increases the uptake of aluminum by the brain, which causes Alzheimer’s dementia. The hypothesis that aluminum causes AD has been around for over 40 years without definitive evidence that it plays a significant role. The bottom line is similar as for fluoride – high levels of aluminum are certainly toxic, but there is no evidence that ordinary levels of everyday exposure pose any risk.


We are exposed to countless substances in our food and water. At high concentrations any of them are potential toxins. There are a large number of animal and toxicology studies showing that fluoride, aluminum, mercury, and many other substances are toxic – this is not in dispute. This data, however, is not necessarily applicable to the levels of exposure from the environment, food, vaccines, or other relevant sources.

The amount of fluoride in particular in our drinking water is carefully regulated by the EPA and there is no evidence of any measurable toxic effects at this exposure level. In fact, the evidence often cited by anti-fluoridation activists shows that such low levels are, if anything, safe.

Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the president and co-founder of the New England Skeptical Society, the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also contributes every Sunday to The Rogues Gallery, the official blog of the SGU.