New Study Adds to Case Against Water Fluoridation

TL;DR: A new Columbia University study found lower problem-solving, memory and attention scores in children whose mothers were exposed during pregnancy to fluoride levels near and above the U.S. fluoridation target. The finding follows a major federal meta-analysis linking higher fluoride exposure to lower child IQ, plus earlier studies finding associations with lower IQ and attention problems. Meanwhile, Birmingham Mayor Randall Woodfin fought to restore fluoride to Central Alabama Water — even as Birmingham schools continue to struggle with reading and math proficiency.

A major new American study has added more weight to the growing scientific case against putting fluoride in public drinking water.

Researchers with Columbia University's Mailman School of Public Health found that higher fluoride levels in drinking water during pregnancy were associated with lower scores on measures of "fluid cognition" in children. Those skills include problem-solving, memory, attention and the ability to handle new information.

The study included 2,514 children born between 2006 and 2019 across 17 research sites in 23 States. Researchers linked fluoride measurements from public water systems with mothers' residential histories during pregnancy, then compared estimated exposure with later cognitive testing.

The most striking finding was where the association appeared.

Researchers identified 675 micrograms per liter — 0.675 mg/L — as the point above which increasing fluoride was associated with falling fluid-cognition scores.

The U.S. Public Health Service recommends 0.7 mg/L for fluoridated water.

Above the 0.675 mg/L point, each additional 500 micrograms per liter was associated with an average 3.36-point lower fluid-cognition score. The relationship was stronger among children tested before age 7.

That does not mean fluoride caused the differences, nor does a 3.36-point difference in fluid cognition equal a 3.36-point IQ loss. The study was observational, and researchers estimated water exposure rather than measuring each mother's total fluoride intake.

Still, the Columbia study cannot be simply dismissed as an isolated statistical curiosity. It joins years of research pointing in the same troubling direction.

One of the most comprehensive examination of the issue to date came from scientists with the federal National Toxicology Program.

Their systematic review and meta-analysis, published in JAMA Pediatrics in 2025, examined 74 studies involving prenatal or childhood fluoride exposure and children's IQ.

Sixty-four of those studies reported an inverse association between fluoride exposure and IQ. Among 59 studies suitable for the main group-level analysis, 52 — or 88% — reported lower IQ with higher fluoride exposure.

The researchers also found a dose-response relationship.

Among 13 studies using individual exposure measurements, every 1 mg/L increase in urinary fluoride was associated with an average 1.63-point decrease in IQ. When researchers restricted the analysis to studies judged at low risk of bias, the estimated decline was still 1.14 points.

There is an important caveat. The researchers found limited data and uncertainty when fluoride exposure was estimated from drinking water alone at concentrations below 1.5 mg/L. The NTP says there still are not enough data to determine whether drinking water at exactly 0.7 mg/L lowers children's IQ.

That makes the new Columbia study especially important.

It examined an American population and found lower fluid cognition associated with prenatal water exposure beginning around 0.675 mg/L — almost exactly the recommended U.S. fluoridation level.

For those who cared to listen, the alarm bells have been ringing for years.

A prospective Canadian birth-cohort study published in JAMA Pediatrics in 2019 examined fluoride exposure during pregnancy and IQ among children ages 3 to 4.

Researchers found that maternal fluoride exposure during pregnancy was associated with lower IQ. A 1 mg/L increase in maternal urinary fluoride was associated with a 4.49-point lower IQ among boys. Higher estimated daily fluoride intake was also associated with lower IQ among boys and girls combined.

Another prospective study examined 213 mother-child pairs in Mexico City and looked at behavior rather than IQ.

A 0.5 mg/L increase in maternal urinary fluoride during pregnancy was associated with significantly higher scores for inattention, ADHD symptoms and cognitive problems when the children were ages 6 through 12. The researchers did not find a significant association with hyperactivity itself.

Different populations. Different researchers. Different measures.

The signs all keep pointing in the same direction — that fluoride is not good for young, developing brains.

That makes Birmingham's recent fluoride fight look increasingly ill-considered.

In March, Central Alabama Water — formerly Birmingham Water Works — announced that it would stop adding fluoride. The utility cited worker safety, aging equipment and the cost of replacing fluoridation systems. Neither federal nor Alabama law requires water utilities to add fluoride.

Birmingham Mayor Randall Woodfin's administration went to court seeking to force the utility to put it back.

The city argued that ending fluoridation created a public-health risk and eventually asked a judge to order fluoride restored at all four treatment plants and prevent the utility from removing it again.

Central Alabama Water countered that repairing and replacing the equipment necessary to restart fluoridation would take at least 315 days and cost almost $4 million.

The city ultimately lost.

Jefferson County Circuit Judge Frederic Allen Bolling dissolved the order requiring fluoride to be restored. Central Alabama Water currently says it no longer adds fluoride at its treatment plants.

Then came the Columbia study.

Only months after Birmingham fought in court to restore fluoridation, researchers reported lower childhood cognitive scores associated with prenatal fluoride exposure beginning near the same concentration fluoridation programs seek to maintain.

The irony is difficult to miss when one considers Birmingham's schools.

Birmingham City Schools have made real progress. The district earned a 77 on Alabama's 2024-25 state report card, its highest score ever, and reduced the number of schools receiving an F to one. Those gains deserve credit.

But overall achievement remains poor.

State testing data compiled by Niche show only 37% of Birmingham students proficient in reading and 16% proficient in mathematics during the 2024-25 school year.

Clearly, Birmingham teachers and families are already fighting an uphill battle.

No single observational study proves fluoridated water is responsible for lower IQ, ADHD or poor school performance. The Columbia researchers do not claim that, and neither does the NTP.

But public policy does not — should not — have to wait for absolute proof before taking a possible risk to children's brains seriously.

The Columbia study now joins the NTP analysis, the Canadian IQ study and behavioral research in finding essentially the same troubling pattern: as prenatal or childhood fluoride exposure rises, measures of cognition or behavior tend to worsen.

That pattern is increasingly difficult to ignore.

And with Birmingham students already struggling to master reading and math, one would think City Hall had better things to do than spending time and taxpayer money fighting in court to restore a water additive increasingly associated with poorer childhood cognition.

The kids already have enough problems to solve.

There is no reason to add fluoride to the mix.

Not in Birmingham. Not in Alabama. Not anywhere in America.