Summary: For the first time, researchers used naturally shed baby teeth as biological time capsules to identify the precise weeks when exposure to common environmental metals most affects the developing brain. The longitudinal study followed children in the PROGRESS birth cohort in Mexico City for more than a decade.
By reading the growth layers in baby teeth, scientists reconstructed weekly exposure to multiple metals and found two critical windows in early infancy—weeks 4–8 and weeks 32–42 after birth—during which metal mixtures (including lead, manganese, and zinc) most strongly predicted altered brain connectivity and behavioral difficulties nearly 12 years later.
Key Facts
- “Tree-ring” tooth analysis: Baby teeth form in layered increments beginning in utero. Mount Sinai’s laser-based method maps metal uptake at a weekly resolution, creating a precise exposure timeline spanning the second trimester through the first year after birth.
- Sensitive postnatal windows: Exposure to metal mixtures during weeks 4–8 and weeks 32–42 after birth showed the strongest links to higher anxiety, attention problems, and mood-related symptoms in adolescence.
- Lasting neural signatures: MRI scans of 191 participants revealed that early-life metal exposure altered patterns of structural brain connectivity, producing persistent changes detectable years later.
- Clinical relevance: About 4% of children in the study had behavioral scores falling in the clinical range, and those outcomes were associated with exposure during the identified critical windows.
Source: Mount Sinai Hospital
Researchers at the Icahn School of Medicine at Mount Sinai report that metal exposures in early life can influence brain development and behavioral health more than a decade later.
Published in Science Advances, this study is the first to pair naturally shed baby teeth with advanced brain imaging to pinpoint specific prenatal and postnatal weeks when the developing brain is particularly vulnerable to environmental metals.
The findings support the idea that environmental conditions in the first months of life leave measurable fingerprints on adolescent brain structure and function, underscoring the value of targeted protections for pregnant people and infants.
Baby Teeth as a Biological Record of Early Life
The researchers analyzed naturally shed teeth from children in the PROGRESS birth cohort in Mexico City, a long-running study that has tracked health from pregnancy into adolescence since 2007. Using a laser-based technique developed at Mount Sinai, the team reconstructed weekly exposures to nine metals from the second trimester through the first postnatal year and linked those timelines to later brain MRIs and behavioral assessments.
“Baby teeth provide a unique biological record of early life,” said Manish Arora, BDS, MPH, PhD, Edith J. Baerwald Professor and Vice Chair of Environmental Medicine at the Icahn School of Medicine at Mount Sinai. “They give us a window into the fetal and early postnatal environment at a weekly temporal resolution—something no other tool can do.”
Key Findings and Data Points
Study participants and measurements included:
- 489 children with detailed tooth-based exposure reconstructions
- 395 children who completed parent-reported behavioral assessments
- 191 children who underwent brain magnetic resonance imaging
Because teeth incorporate trace metals as they form, they serve as a sequential record—analogous to tree rings—capturing exposure over time. The analysis identified two postnatal windows with the strongest associations to later behavioral differences: weeks 4–8 and weeks 32–42 after birth. Higher exposure to metal mixtures in these windows correlated with increased behavioral symptom scores, particularly for anxiety, attention, and mood. The largest effects were observed in late infancy (weeks 32–42), with a reported association size of β = 0.15 (95% CI 0.004–0.28).
Approximately 4% of participants scored in the clinical range on the Behavioral Symptoms Index of the Behavior Assessment System for Children (BASC-2), indicating symptoms of clinical concern that were related to the timing of early environmental exposure.
Brain imaging showed that early-life exposure to higher metal mixtures corresponded with measurable differences in brain development—smaller brain volume, reduced global efficiency, and alterations in white matter integrity—consistent with lasting impacts on structural connectivity.
Environmental Health and Policy Implications
Many metals measured—such as manganese, zinc, magnesium, and especially lead—are commonly encountered through food, drinking water, and the built environment. The study emphasizes that timing of exposure can be as critical as exposure level.
“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 of Environmental Medicine at Mount Sinai. “Our findings point to specific high-risk windows where prevention efforts could be most effective.”
Lead author Elza Rechtman, PhD, noted the precision of the vulnerable windows: “Exposures during just a few weeks—particularly in early infancy—were linked to measurable differences in brain structure, connectivity, and behavior more than a decade later. Policies that reduce metal exposure during pregnancy and infancy could yield lifelong brain health benefits.”
Dr. Arora added that environmental regulations and public health strategies may need to focus more explicitly on protecting pregnant people and infants from metal exposure in food, water, and housing.
What This Means for Families and Clinicians
The results do not imply that a single exposure determines a child’s future. Rather, the study highlights how reducing metal exposure during pregnancy and the first year of life may support healthier brain development.
Practical steps to lower exposure include ensuring safe drinking water, careful food sourcing and preparation to avoid soil-based contaminants, and minimizing contact with legacy lead paint and industrial dust during pregnancy and infancy.
Clinicians should consider environmental exposure histories when evaluating children’s developmental and behavioral risk, and public health strategies can be refined to focus on the identified sensitive windows.
A New Era of Environmental Brain Research
This work advances precision environmental health by moving beyond general early-life exposure concerns to pinpointing specific developmental windows when prevention may be most effective. Future research will aim to measure a broader range of chemicals in teeth and validate these findings in larger and more diverse populations to guide targeted interventions and policy.
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 capture current, short-term exposure. Baby teeth act like a permanent archive, recording weekly metal uptake from roughly 20 weeks before birth through the first postnatal year, allowing reconstruction of exposure timing at high resolution.
A: No. The study shows timing matters, but a single exposure does not predetermine outcomes. Identifying sensitive weeks helps target prevention when the brain is most susceptible.
A: Researchers recommend “precision prevention”: ensure safe drinking water, choose and prepare food to limit soil-based contaminants, and reduce contact with known sources like old lead paint and industrial dust during pregnancy and the first year of life.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full.
- Additional context was provided by 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
Early-life exposure to neurotoxic metals can disrupt brain development and raise the risk of later mental health challenges, but precise vulnerable periods and mechanisms have been unclear. This study used naturally shed baby teeth to reconstruct weekly concentrations of nine metals from roughly 20 weeks before birth to 40 weeks after birth in 489 children aged 8 to 14 years. Behavior was assessed with standardized questionnaires and brain structure and function were measured by magnetic resonance imaging. Using lagged weighted quantile sum regression, the team identified sensitive developmental windows in which higher exposure to metal mixtures was linked to greater behavioral problems, smaller brain volume, reduced global efficiency, and weaker white matter integrity. The results indicate the developing brain is especially vulnerable to metal exposure in early life, with effects persisting into adolescence.