Summary: For the first time, researchers used naturally shed baby teeth as “biological time capsules” to pinpoint exactly when environmental metal exposure most impacts the developing brain. The study followed children from the PROGRESS cohort in Mexico City for over a decade.
By analyzing the “growth rings” in baby teeth, the team identified two critical windows in early infancy, weeks 4–8 and weeks 32–42, where exposure to metal mixtures (including lead, manganese, and zinc) predicted measurable differences in brain connectivity and behavioral health nearly 12 years later.
Key Facts
- The “Tree Ring” Method: Baby teeth form in layers beginning in utero. Mount Sinai’s laser-based technology reconstructs a weekly timeline of what metals a child was exposed to before and after birth.
- Critical Vulnerability Windows: Exposure to metal mixtures during weeks 4–8 and weeks 32–42 after birth showed the strongest link to increased anxiety, attention issues, and mood challenges in adolescence.
- Neural Fingerprints: Brain MRI scans of 191 participants revealed that early-life metal exposure altered how different brain regions communicate, leaving a permanent “fingerprint” on the brain’s structural connectivity.
- Clinical Impact: Roughly 4% of children in the study had behavioral scores in the clinical range, directly correlating with the specific timing of their environmental exposure.
Source: Mount Sinai Hospital
Researchers at the Icahn School of Medicine at Mount Sinai report that early-life exposure to common environmental metals may influence brain development and behavioral health more than a decade later.
The study, published in Science Advances, is the first to combine naturally shed baby teeth with advanced brain imaging to pinpoint specific weeks during pregnancy and infancy when the developing brain appears most vulnerable to environmental exposures.
The research provides compelling new evidence that environmental conditions in the earliest months of life can leave measurable “fingerprints” on the adolescent brain—highlighting the importance of environmental protections for pregnant people and infants.
Baby Teeth as a Biological Record of Early Life
The team analyzed naturally shed baby teeth from children enrolled in the PROGRESS birth cohort in Mexico City, a multinational study founded in 2007 that has followed children from pregnancy into adolescence to understand how social and chemical environmental exposures shape health across the life course.
Using a specialized method developed at Mount Sinai, researchers reconstructed weekly exposure to a list of nine metals from the second trimester of pregnancy through the first year of life. These exposure timelines were then linked to brain MRI scans and behavioral assessments conducted years later.
“Baby teeth provide a unique biological record of early life,” said Manish Arora, BDS, MPH, PhD, the 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. “They give us a window into the fetal and early postnatal environment at a weekly temporal resolution, something no other technology can do.”
Key Findings and Data Points
The study included:
- 489 children with detailed baby-tooth exposure data
- 395 of these children completed behavioral assessments
- 191 of these participants completed a brain magnetic resonance imaging scan
Baby teeth form in layers, similar to tree rings, beginning in utero. As they develop, they incorporate trace 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, the researchers identified two critical windows in early infancy when exposure to metal mixtures was most strongly linked to later behavioral differences:
- Weeks 4–8 after birth
- Weeks 32–42 after birth
During these periods, higher metal mixture exposure was associated with increased behavioral symptom scores, including anxiety, attention, and mood-related challenges. For example, the strongest associations 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 children had behavioral scores in the clinical range, meaning their symptoms were serious enough to be considered a mental health concern. These scores were based on the Behavioral Symptoms Index (BSI), a core composite scale in the Behavior Assessment System for Children, Second Edition (BASC-2), a behavioral assessment completed by parents.
Brain scans showed that children exposed to higher levels of metal mixtures early in life had measurable differences in how their brains developed and how brain regions communicated with each other.
Environmental Health and Climate Implications
Many of the metals studied—such as manganese, zinc, magnesium, and lead—are commonly encountered through food, drinking water, and the built environment.
“This study shows that when exposure happens matters just as much as what the exposure is,” said senior author Megan K. Horton, PhD, MPH, Professor, Environmental Medicine, Icahn School of Medicine at Mount Sinai. “Our findings shift prevention from broad early-life exposure concerns to 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 significance:
“What surprised us most was how precisely these vulnerable windows emerged. Exposures occurring during just a few critical weeks—especially in early infancy—were linked to 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 could have lifelong benefits for brain health.”
“The results suggest that environmental regulations and public health policies may need to focus more specifically on protecting pregnant people and infants from metal exposure in food, water, and housing,” added Dr. Arora.
What This Means for Families and Clinicians
The findings do not suggest that any single exposure determines a child’s future. Instead, they show that reducing environmental metal exposure during pregnancy and infancy may support healthier brain development.
Simple steps that may help reduce exposure include:
- Ensuring safe drinking water
- Careful food preparation and sourcing
- Reducing exposure to known environmental metal sources
For clinicians, the research highlights the importance of considering environmental histories when assessing long-term behavioral and mental health risk.
A New Era of Environmental Brain Research
This work marks an important step towards 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 chemicals measurable in baby teeth and validate findings in larger US populations, with the goal of informing policies and interventions that protect children during the most sensitive stages of brain development.
Funding: This research was supported by the National Institute of Environmental Health Sciences and the National Center for Advancing Translational Sciences.
Key Questions Answered:
A: Blood tests only show a “snapshot” of what is in the body right now. Baby teeth act like a hard drive; they capture and store a permanent, weekly record of every metal a child encountered from the second trimester of pregnancy through the first year of life.
A: No. The study shows that timing matters, but it doesn’t mean a single exposure is a “destiny.” Instead, it highlights specific weeks when the brain is most sensitive, allowing for more precise public health protections during those high-risk windows.
A: The researchers suggest focusing on “precision prevention”: ensuring safe drinking water, careful food sourcing (to avoid soil-based heavy metals), and reducing exposure to old lead paint or industrial dust during pregnancy and the first year of life.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this neurodevelopment research news
Author: Laura Ruocco-Duran
Source: Mount Sinai Hospital
Contact: Laura Ruocco-Duran – Mount Sinai Hospital
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Fetal and postnatal metal metabolism-related changes in brain function are associated with childhood behavioral deficits” by Elza Rechtman, Avraham Reichenberg, Azzurra Invernizzi, Lazar Fleysher, Vida Rebello, Kristie Oluyemi, Michelle A. Rodriguez, Anna Sather, Libni A. Torres-Olascoaga, Luis F. Bautista-Arredondo, Sandra Martínez-Medina, Rafael Lara-Estrada, Chris Gennings, Martha M. Téllez-Rojo, Robert O. Wright, Manish Arora, and Megan K. Horton. Science Advances
DOI:10.1126/sciadv.adz1340
Abstract
Fetal and postnatal metal metabolism-related changes in brain function are associated with childhood behavioral deficits
Exposure to neurotoxic metals early in life can disrupt brain development and increase risk of later mental health problems, but vulnerable periods and underlying mechanisms remain unclear.
We examined how early life exposures to mixtures of metals affect children’s brain and behavior using naturally shed “baby” teeth as a biomarker of direct exposure. We studied 489 children aged 8 to 14 years and reconstructed weekly concentrations of nine metals from 20 weeks before birth to 40 weeks after birth.
We assessed behavior using standardized questionnaires and measured brain structure and function with magnetic resonance imaging.
Using lagged weighted quantile sum regression, we identified sensitive developmental windows during which higher exposure to metal mixtures was linked to more behavioral problems, smaller brain volume, reduced brain global efficiency, and weaker white matter integrity.
Findings suggest that the developing brain is especially vulnerable to metals in early life, with lasting effects into adolescence.
