Baby teeth reveal metal’s early impact on the brain

Researchers at the Icahn School of Medicine at Mount Sinai report that exposure to common environmental metals in early life can affect brain development and behavioral health more than a decade later. The study, published in science advancementis the first to combine naturally erupting baby teeth with advanced brain imaging to pinpoint specific weeks during pregnancy and infancy when the developing brain appears most sensitive to environmental exposures.

This research provides new evidence that environmental conditions in the early months of life can leave measurable “fingerprints” on adolescent brains – highlighting the importance of environmental protection for pregnant people and infants.

Baby teeth as a biological record of early life

The team analyzed the naturally erupting baby teeth of children enrolled in the PROGRESS birth cohort in Mexico City, a multinational study established in 2007 that follows children from pregnancy to adolescence to understand how social and chemical environmental exposures affect health across the lifespan.

Using a special method developed at Mount Sinai, researchers reconstructed weekly exposure to a list of nine metals from the second trimester of pregnancy to the first year of life. These exposure timelines were linked to brain MRI scans and behavioral assessments conducted years later.

Baby teeth provide a unique biological record of early life. They give us a window into the fetal and early postnatal environment at weekly temporal resolution, which no other technique can do.”

Manish Arora, BDS, MPH, PhD, Edith J. Baerwald Professor and Vice Chair of the Department of Environmental Medicine at the Icahn School of Medicine at Mount Sinai, and corresponding author of this study

Key Findings and Data Points

Studies include:

• 489 children with detailed infant-dental exposure data
• Of these, 395 children completed the behavioral assessment.
• Of these, 191 participants completed brain magnetic resonance imaging scans.

Milk teeth form in layers, initially similar to tree rings in the uterus. As they develop, they incorporate small amounts of metals circulating in the body. Using laser-based analysis, researchers can reconstruct a timeline of metal uptake during pregnancy and early infancy. In this study, researchers identified two critical windows in early infancy when exposure to metal mixtures was most strongly linked to later behavioral differences:

• 4-8 weeks after birth
• 32-42 weeks after birth

During these periods, high metal mixture exposure was associated with increased behavioral symptom scores, including anxiety, attention, and mood-related challenges. For example, the strongest association occurred in late infancy (weeks 32–42), with measurable increases in behavioral symptom scores (β = 0.15, 95% CI 0.004–0.28). About 4 percent of the children had behavioral scores in the clinical range, meaning their symptoms were severe enough to be considered a mental health concern. These scores were based on the Behavior Symptom Index (BSI), a core composite scale in the Behavior Assessment System for Children, Second Edition (BASC-2), which is a behavior assessment completed by parents.

Brain scans revealed that children exposed to high levels of the metal mixture early in life had measurable differences in how their brains developed and how brain areas communicated with each other.

Environmental health and climate implications

Many of the metals studied—such as manganese, zinc, magnesium, and lead—are commonly found through food, drinking water, and the built environment.

“This study shows that when exposure occurs matters as much as what the exposure is,” said senior author Megan K. Horton, PhD, MPH, professor of environmental medicine, Icahn School of Medicine at Mount Sinai. “Our findings shift prevention from broader early life risk concerns to a focus on protecting children during specific high-risk windows.”

Lead author Elza Rechtman, PhD, assistant professor, environmental medicine, Icahn School of Medicine at Mount Sinai, emphasized the broader environmental importance:

“What surprised us most was how precisely these vulnerable windows unfolded. Exposures occurring during just a few critical weeks – particularly in early infancy – were associated with measurable differences in brain structure, connectivity, and behavior more than a decade later. These findings highlight how environmental policies that reduce metal exposure during pregnancy and infancy can have lifelong benefits for brain health.”

“The results suggest that environmental regulations and public health policies may need to focus specifically on protecting pregnant people and infants from metal exposure in food, water, and housing,” Dr. Arora said.

What this means for families and physicians

The findings do not suggest that any one risk determines a child’s future. Instead, they show that reducing environmental metal exposure during pregnancy and infancy can help promote healthy brain development.

Simple steps that can help reduce the risk include:

• ensuring safe drinking water
• Careful food preparation and sourcing
• Reducing exposure to known environmental metal sources

For physicians, the research highlights the importance of considering environmental history when assessing long-term behavioral and mental health risk.

A new era of environmental brain research

This work represents an important step toward precision environmental health, shifting research from general early life exposure to identifying specific developmental windows when prevention may be most effective.

Future studies will expand the range of measurable chemicals in children’s teeth and validate the findings in larger US populations, with the goal of informing policies and interventions that protect children during the most sensitive stages of brain development.