The European Union and the United States are going in opposite directions on fluoride safety, with the European Food Safety Authority reiterating that it is safe in drinking water and ingested fluoridated dental care products.

Fluoride is a naturally occurring element that can inhibit tooth decay. While only a few European countries currently add fluoride to public water supplies, the government safety agency is approving its use.

“We estimated that, in general, with the current concentrations of fluoride in European drinking water, total fluoride exposure does not exceed the new safe and tolerable upper intake levels for almost all age groups and therefore does not pose a health concern,” the chairwoman of the authority’s scientific committee, Susanne Hougaard Bennekou, says.

The only exception cited was children ages 4 to 8. Scientists say that with the typical fluoride concentrations in drinking water, if children also ingest 100 percent of fluoride dental care products they use, they could suffer mild tooth discoloration.

“This is unlikely to occur if children spit the toothpaste out properly after brushing their teeth,” Ms. Bennekou says.

The safety authority decided to re-evaluate fluoride safety due to recent studies suggesting a possible link to harmful effects on the developing nervous systems of children. Analysts also looked at the potential effects of fluoride on the thyroid, bones, and teeth.

The review notes that the current legal limit for drinking water in the bloc is 1.5 milligrams of fluoride per liter, which may be too high, but fluoride concentrations found in European countries are usually less than 0.3 milligrams per liter. Scientists found that even the youngest babies can intake a milligram of fluoride a day safely.

“There is evidence that we can’t ignore linking fluoride to possible effects on the developing nervous system of the fetus. But the evidence is not sufficient to set a threshold,” the chairman of the fluoride working group, Thorhallur Halldorsson, says.

While the European Union continues to call fluoride safe, the Trump administration is trying to curtail its use.

The health and human services secretary, Robert F. Kennedy Jr., has pledged to remove fluoride from the American water supply and announced that the Centers for Disease Control and Prevention would stop recommending fluoridation in drinking water systems nationwide. Mr. Kennedy says that fluoride is a “dangerous neurotoxin,” linking it to conditions such as arthritis, bone fractures, and thyroid disease.

Florida and Utah have already enacted legislation this year to remove fluoride from their public water supplies.

The Food and Drug Administration regulates fluoride in bottled water and prescription drug products for children. Fluoride pills that are currently prescribed were never approved by the agency but it has allowed them to stay on the market since they were introduced in the 1940s because medical groups have advocated for them. That changed with the new administration.

The FDA is now taking steps to remove ingestible fluoride prescription drug products for children from the market. It held a daylong public meeting on ingestible fluoride prescription drugs on Wednesday.

Scientists and some parents who live in areas without water fluoridation advocated for pediatric versions of the prescriptions to remain available. Sally Greenberg testified that parents need access to fluoride supplements as communities stop adding fluoride to water. She says her son was prescribed fluoride supplements when they lives in a community without fluoridated water and he, now 29, has no discernable negative effects on his gut or his brain.

A dean at the University of Utah’s school of dentistry cautioned that when fluoride is not present during a child’s development, it results in reduced tooth enamel strength and weaker bones.

The new director of the FDA’s drug evaluation and research center, George Tidmarsh, was unmoved by their pleas.

“We’ve got to look at a risk-benefit analysis. And since this isn’t approved, it’s never been through the rigorous FDA process of saying there’s a benefit that outweighs the risk,” Dr. Tidmarsh told the news outlet NOTUS about fluoride supplements.

Dr. Tidmarsh says the FDA needs to reanalyze the data on Fluoride supplements after some studies showed that ingesting fluoride could alter the gut microbiome.