The health secretary frames fluoride as a dose-response danger sitting in the tap. "The more fluoride you get, the higher the levels in your drinking water and your urine, the more likely it is you'll lose IQ, and also other neurological injuries like ADHD." [1] There is real science underneath the IQ concern. The trouble is the dose it was measured at, which is not the dose Americans drink.
The level is the whole story
The United States recommends fluoride in drinking water at 0.7 milligrams per liter. [2][3] The studies linking fluoride to lower IQ, summarized in the National Toxicology Program's review, found those associations at levels above 1.5 milligrams per liter, more than double the U.S. target, and drawn largely from places like China, India, Iran, and Pakistan rather than American water systems. [3] A real effect at twice the dose is not evidence of harm at the dose actually in use, any more than the toxicity of ten cups of coffee tells you one cup is dangerous.
Data
| U.S. recommended level | 0.7 |
|---|---|
| Level linked to lower IQ | 1.5 |
The researchers' own caveat
This is not an inference critics had to draw. The NTP authors drew it themselves, stating that their findings do not pertain to the practice of fluoridation in the United States and Canada. [2] The people who produced the science the secretary cites went out of their way to say it does not apply to American water.
At U.S. levels, the effect is not there
When researchers looked specifically at recommended-level fluoride, the IQ effect did not appear. A large long-term study found no measurable differences in memory, attention, or other cognitive skills among children exposed to fluoride at the levels U.S. systems actually use. [4] That is the relevant test, and it came back null. It is why the American Dental Association reaffirms its support of community water fluoridation, and why the CDC and the American Academy of Pediatrics continue to endorse it at 0.7 milligrams per liter as safe and effective against cavities. [2]
THE BOTTOM LINE
- Fluoride "makes you lose IQ" at U.S. levels: Misleading [1]
- The IQ associations appear above 1.5 mg/L, more than double the 0.7 mg/L the U.S. recommends [2][3]
- The NTP researchers say their findings do not apply to U.S. fluoridation, and a large study found no effect at recommended levels [2][4]
Fluoride can harm at high enough concentrations, like most things, and that is worth monitoring. Presenting overseas studies at double the American dose as a reason to pull fluoride from U.S. water inverts what the science says. At the level in the tap, the dental benefit is established and the IQ harm is not.
