Though the new NTP report sheds light on the connection between IQ issues and fluoride levels above 1.5 mg/L, experts agree there are significant questions left unanswered. In particular, it’s unclear at what specific level of exposure fluoridated water becomes dangerous for children and pregnant people.
“The NTP report does not adequately address this issue,”
Tommaso Filippini, MD, DrPH, PhD, associate professor of epidemiology and public health at the Medical School of the University of Modena, Reggio Emilia in Italy, told
Health.
A 2023 meta-analysis, which Filippini co-authored, included 30 studies on fluoride exposure in drinking water from around the world. It concluded that fluoride levels begin to impact kids’ IQ once they surpass 1 mg/L and become more pronounced at 2 mg/L.8
Additionally, adults don’t seem to be at risk of cognitive issues from fluoride, “but there hasn’t been that much research done” on the subject, Hu told
Health.
The Connection Between Fluoride and IQ in Children
According to Filippini, fluoride can accumulate in the regions of the brain responsible for memory and learning, creating
oxidative stress in these parts of the brain. This stress could potentially lead to cell death.9
The blood-brain barrier can protect adult brains from toxins to a certain extent, “but it is less efficient in the fetus during pregnancy and in children,” he added.
Some studies have shown that fluoride can cross the placenta and alter the developing brain, specifically in regions associated with learning, behavior, memory, and executive function, Malin added.10 Fluoride may also interfere with molecular processes involved in neurotransmission when the brain is developing, said Hu.
Hu said the evidence clearly shows fluoride is a neurotoxin, at least for a developing brain. But taking fluoride out of public drinking water entirely isn’t a great solution, he explained.
“There certainly are some communities of people who have less access to fluoridated products,” he said. “And you always worry that by adopting one society-wide practice or ending another society-wide practice, there will be people who are adversely impacted.”
