Science
Pregnant? Researchers want you to know something about fluoride
Adding fluoride to drinking water is widely considered a triumph of public health. The Centers for Disease Control and Prevention says the cavity-prevention strategy ranks alongside the development of vaccines and the recognition of tobacco’s dangers as signal achievements of the 20th century.
But new evidence from Los Angeles mothers and their preschool-age children suggests community water fluoridation may have a downside.
A study published Monday in JAMA Network Open links prenatal exposure to the mineral with an increased risk of neurobehavioral problems at age 3, including symptoms that characterize autism spectrum disorder. The association was seen among women who consumed fluoride in amounts that are considered typical in Los Angeles and across the country.
The findings do not show that drinking fluoridated water causes autism or any other behavioral conditions. Nor is it clear whether the relationship between fluoride exposure and the problems seen in the L.A.-area children — a cohort that is predominantly low-income and 80% Latino — would extend to other demographic groups.
However, the results are concerning enough that USC epidemiologist Tracy Bastain said she would advise pregnant people to avoid fluoridated water straight from the tap and drink filtered water instead.
“This exposure can impact the developing fetus,” said Bastain, the study’s senior author. “Eliminating that from drinking water is probably a good practice.”
About 63% of Americans receive fluoridated water through their taps, including 73% of those served by community water systems, according to the CDC. In Los Angeles County, 62% of residents get fluoridated water, the Department of Public Health says.
The data analyzed by Bastain and her colleagues came from participants in an ongoing USC research project called Maternal and Developmental Risks from Environmental and Social Stressors, or MADRES. Women receiving prenatal care from clinics in Central and South Los Angeles that cater to low-income patients with Medi-Cal insurance were invited to join.
Between 2017 and 2020, 229 mothers took a test to measure the concentration of fluoride in their urine during their third trimester of pregnancy. Then, between 2020 and 2023, they completed a 99-question survey to assess their child’s behavior when their sons and daughters were 3 years old.
Among other things, the survey asked mothers whether their children were restless, hyperactive, impatient, clingy or accident-prone. It also asked about specific behaviors, such as resisting bedtime or sleeping alone, chewing on things that aren’t edible, holding their breath, and being overly concerned with neatness or cleanliness.
Some of the questions the mothers answered addressed health problems with no obvious medical cause, including headaches, cramps, nausea and skin rashes.
Among the 229 children — 116 girls and 113 boys — 35 were found to have a collection of symptoms that put them in the clinical or borderline clinical range for inward-focused problems such as sadness, depression and anxiety. In addition, 23 were in the clinical or borderline clinical range for behaviors directed at others, such as shouting in a classroom or attacking other kids, and 32 were deemed at least borderline clinical for a combination of inward and outward problems.
What interested the researchers was whether there was any correlation between a child’s risk of having clinical or borderline clinical behavioral problems and the amount of fluoride in his or her mother’s urine during pregnancy.
They found that compared to women whose fluoride levels placed them at the 25th percentile — meaning 24% of women in the study had levels lower than theirs — women at the 75th percentile were 83% more likely to have their child score in the “clinical” or “borderline clinical” range for inward and outward problems combined. When the researchers narrowed their focus to children in the clinical range only, that risk increased to 84%, according to the study.
The researchers also found that the same increase in fluoride levels was associated with an 18.5% increase in a child’s symptoms related to autism spectrum disorder, as well as an 11.3% increase in symptoms of anxiety.
The amount of fluoride needed for mothers to go from the 25th to the 75th percentile was 0.68 milligrams per liter. As it happens, that’s nearly identical to the 0.7 mg per liter standard that federal regulators say is optimal for preventing tooth decay.
Bastain said that allowed the researchers to compare what might happen to children in two parallel universes: a typical one where their mothers consumed fluoridated water during pregnancy, and an alternate one where they didn’t.
“You can use it as a proxy for if they lived in a fluoridated community or not,” she said.
What that thought experiment shows is that children in the fluoridated community face a higher level of risk. That said, it’s not clear when that risk becomes high enough to be worrisome.
“We don’t know what the safe threshold is,” Bastain said. “It’s not like you can say that as long as you’re under the 75th percentile, there are no effects.”
The study authors’ concerns about the effects of fluoride on developing brains didn’t come out of nowhere.
The National Toxicology Program — a joint effort of the CDC, the National Institutes of Health, and the Food and Drug Administration — has been investigating the issue since 2016. In a report last year that reviewed an array of evidence from humans and laboratory animals, a working group concluded “with moderate confidence” that overall fluoride exposure at levels at or above 1.5 mg per liter “is consistently associated with lower IQ in children.”
The working group added that “more studies are needed to fully understand the potential for lower fluoride exposure to affect children’s IQ.”
A 2019 study of hundreds of mothers in Canada — where 39% of residents have fluoridated water — found that a 1-mg increase in daily fluoride intake during pregnancy was associated with a 3.7-point reduction in IQ scores in their 3- and 4-year-old children.
And among hundreds of pregnant women in Mexico, a 0.5-mg-per-liter increase in urinary fluoride went along with a 2.5-point drop in IQ scores for their 6- to 12-year-old children, researchers reported in 2017.
Bastain and her colleagues write their study is the first they are aware of that examines the link between prenatal fluoride exposure and neurobehavioral outcomes in children in the United States. The results are sure to be controversial, Bastain said, but there’s a straightforward way for pregnant people to reduce the possible risk.
“It’s a pretty easy intervention to get one of those tabletop plastic pitchers” that filter out metals, she said. “Most of them do a pretty good job of filtering out fluoride.”
Science
What’s in a Name? For These Snails, Legal Protection
The sun had barely risen over the Pacific Ocean when a small motorboat carrying a team of Indigenous artisans and Mexican biologists dropped anchor in a rocky cove near Bahías de Huatulco.
Mauro Habacuc Avendaño Luis, one of the craftsmen, was the first to wade to shore. With an agility belying his age, he struck out over the boulders exposed by low tide. Crouching on a slippery ledge pounded by surf, he reached inside a crevice between two rocks. There, lodged among the urchins, was a snail with a knobby gray shell the size of a walnut. The sight might not dazzle tourists who travel here to see humpback whales, but for Mr. Avendaño, 85, these drab little mollusks represent a way of life.
Marine snails in the genus Plicopurpura are sacred to the Mixtec people of Pinotepa de Don Luis, a small town in southwestern Oaxaca. Men like Mr. Avendaño have been sustainably “milking” them for radiant purple dye for at least 1,500 years. The color suffuses Mixtec textiles and spiritual beliefs. Called tixinda, it symbolizes fertility and death, as well as mythic ties between lunar cycles, women and the sea.
The future of these traditions — and the fate of the snails — are uncertain. The mollusks are subject to intense poaching pressure despite federal protections intended to protect them. Fishermen break them (and the other mollusks they eat) open and sell the meat to local restaurants. Tourists who comb the beaches pluck snails off the rocks and toss them aside.
A severe earthquake in 2020 thrust formerly submerged parts of their habitat above sea level, fatally tossing other mollusks in the snail’s food web to the air, and making once inaccessible places more available to poachers.
Decades ago, dense clusters of snails the size of doorknobs were easy to find, according to Mr. Avendaño. “Full of snails,” he said, sweeping a calloused, violet-stained hand across the coves. Now, most of the snails he finds are small, just over an inch, and yield only a few milliliters of dye.
Science
Video: This Parrot Has No Beak, But Is at the Top of the Pecking Order
new video loaded: This Parrot Has No Beak, But Is at the Top of the Pecking Order
By Meg Felling and Carl Zimmer
April 20, 2026
Science
Contributor: Focus on the real causes of the shortage in hormone treatments
For months now, menopausal women across the U.S. have been unable to fill prescriptions for the estradiol patch, a long-established and safe hormone treatment. The news media has whipped up a frenzy over this scarcity, warning of a long-lasting nationwide shortage. The problem is real — but the explanations in the media coverage miss the mark. Real solutions depend on an accurate understanding of the causes.
Reporters, pharmaceutical companies and even some doctors have blamed women for causing the shortage, saying they were inspired by a “menopause moment” that has driven unprecedented demand. Such framing does a dangerous disservice to essential health advocacy.
In this narrative, there has been unprecedented demand, and it is explained in part by the Food and Drug Administration’s recent removal of the “black-box warning” from estradiol patches’ packaging. That inaccurate (and, quite frankly, terrifying) label had been required since a 2002 announcement overstated the link between certain menopause hormone treatments and breast cancer. Right-sizing and rewording the warning was long overdue. But the trouble with this narrative is that even after the black-box warning was removed, there has not been unprecedented demand.
Around 40% of menopausal women were prescribed hormone treatments in some form before the 2002 announcement. Use plummeted in its aftermath, dipping to less than 5% in 2020 and just 1.8% in 2024. According to the most recent data, the number has now settled back at the 5% mark. Unprecedented? Hardly. Modest at best.
Nor is estradiol a new or complex drug; the patch formulation has existed for decades, and generic versions are widely manufactured. There is no exotic ingredient, no rare supply chain dependency, no fluke that explains why women are suddenly being told their pharmacy is out of stock month after month.
The story is far more an indictment of the broken insurance industry: market concentration, perverse incentives and the consequences of allowing insurance companies to own the pharmacy benefit managers that effectively control drug access for the majority of users. Three companies — CVS Caremark, Express Scripts and OptumRx — manage 79% of all prescription drug claims in the United States. Those companies are wholly owned subsidiaries of three insurance behemoths: CVS Health, Cigna and UnitedHealth Group, respectively. This means that the same corporation that sells you your insurance plan also decides which drugs get covered, at what price, and whether your pharmacy can stock them. This is called vertical integration. In another era, we might have called it a cartel. The resulting problems are not unique to hormone treatments; they have affected widely used medications including blood thinners, inhalers and antibiotics. When a low-cost generic such as estradiol — a medication with no blockbuster profit margins and no patent protection — runs into friction in this system, the friction is not random. It is structural. Every decision in that chain is filtered through the same corporate profit motive. And when the drug in question is an off-patent estradiol patch that has negligible profit margins because of generic competition but requires logistical investment to keep consistently in stock? The math on “how much does this company care about ensuring access” is not complicated.
Unfortunately, there is little financial incentive to ensure smooth, consistent access. There is, however, significant financial incentive to steer patients toward branded alternatives, or simply to let supply tighten — because the companies aren’t losing much profit if sales of that product dwindle. This is not a conspiracy theory: The Federal Trade Commission noted this dynamic in a report that documented how pharmacy benefit managers’ practices inflate costs, reduce competition and harm patient access, particularly for independent pharmacies and for generic drugs.
Any claim that the estradiol patch shortage is meaningfully caused by more women now demanding hormone treatments is a distraction. It is also misogyny, pure and simple, to imply that the solution to the shortage is for women’s health advocates to dial it down and for women to temper their expectations. The scarcity of estradiol patches is the outcome of a broken system refusing to provide adequate supply.
Meanwhile, there are a few strategies to cope.
- Ask your prescriber about alternatives. Estradiol is available in multiple formulations, including gel, spray, cream, oral tablet, vaginal ring and weekly transdermal patch, which is a different product from the twice-weekly patch and may be more consistently available depending on manufacturer and region.
- Consider an online pharmacy. Many are doing a good job locating and filling these prescriptions from outside the pharmacy benefit manager system.
- Call ahead. Patch shortages are inconsistent across regions and distributors. A call to pharmacies in your area, or a broader geographic radius if you’re able, can locate stock that your regular pharmacy doesn’t have.
- Consider a compounding pharmacy. These sources can sometimes meet needs when commercially manufactured products are inaccessible. The hormones used are the same FDA-regulated bulk ingredients.
Beyond those Band-Aid solutions, more Americans need to fight for systemic change. The FTC report exists because Congress asked for it and committed to legislation that will address at least some of the problems. The FDA took action to change the labeling on estrogen in the face of citizen and medical experts’ pressure; it should do more now to demand transparency from patch manufacturers.
Most importantly, it is on all of us to call out the cracks in the current system. Instead of repeating “there’s a patch shortage” or a “surge in demand,” say that a shockingly small minority of menopausal women still even get hormonal treatments prescribed at all, and three drug companies control the vast majority of claims in this country. Those are the real problems that need real solutions.
Jennifer Weiss-Wolf, the executive director of the Birnbaum Women’s Leadership Center at New York University School of Law, is the author of the forthcoming book “When in Menopause: A User’s Manual & Citizen’s Guide.” Suzanne Gilberg, an obstetrician and gynecologist in Los Angeles, is the author of “Menopause Bootcamp.”
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