Summary: For the first time, researchers used naturally shed baby teeth as biological time capsules to locate the precise weeks when exposure to environmental metals most affects brain development. Following children from the PROGRESS cohort in Mexico City for more than a decade, the study linked early-life metal exposure to changes in brain connectivity and later behavioral outcomes.
By reading the layered “growth rings” in baby teeth, investigators identified two specific vulnerable windows in infancy—weeks 4–8 and weeks 32–42—during which exposure to metal mixtures (including lead, manganese, zinc and others) predicted differences in brain network structure and increased behavioral symptoms nearly twelve years later.
Key Facts
- “Tree ring” timeline: Baby teeth form layered records beginning in utero. Mount Sinai researchers used laser-based analysis to reconstruct weekly exposure histories for multiple metals.
- Critical vulnerability windows: Elevated exposure to metal mixtures during weeks 4–8 and weeks 32–42 after birth showed the strongest associations with later anxiety, attention difficulties, and mood-related concerns.
- Neural fingerprints: MRI scans of 191 participants revealed lasting alterations in how brain regions communicate, indicating structural connectivity differences linked to early metal exposure.
- Clinical impact: About 4% of children in the study had behavioral scores in the clinical range, and these higher-risk scores corresponded with exposure timing identified from the teeth.
Source: Mount Sinai Hospital
Overview
Researchers at the Icahn School of Medicine at Mount Sinai report that exposure to common environmental metals in early life can leave measurable effects on brain development and behavioral health more than a decade later. Published in Science Advances, this work pairs naturally shed baby teeth with advanced brain imaging to pinpoint specific weeks during pregnancy and infancy when the developing brain appears especially sensitive to metal mixtures.
The results provide strong new evidence that environmental conditions in the earliest months of life can leave long-lasting signatures on the adolescent brain, underscoring the importance of protecting pregnant people and infants from metal exposures.
Baby teeth as a weekly biological record
The study analyzed naturally shed baby teeth collected from children enrolled in the PROGRESS birth cohort in Mexico City. PROGRESS, established in 2007, tracks participants from pregnancy through adolescence to study how social and chemical environments shape health over time.
Using a specialized laser-based technique developed at Mount Sinai, the team reconstructed weekly concentrations for nine metals from the second trimester through the first year after birth. These exposure timelines were then compared with later MRI scans and standardized behavioral assessments.
“Baby teeth offer a unique, high-resolution archive of fetal and infant exposures,” 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 on the study. “They provide weekly-level detail that other biomarkers cannot.”
Study design and main findings
This research included:
- 489 children with reconstructed baby-tooth metal exposure profiles
- 395 children who completed parent-reported behavioral assessments
- 191 participants who underwent brain magnetic resonance imaging
Baby teeth grow in incremental layers that trap trace metals circulating in the body, much like tree rings. The laser-based analysis allowed the researchers to identify two postnatal windows—weeks 4–8 and weeks 32–42—during which higher exposure to metal mixtures was most strongly associated with later behavioral problems, including anxiety, attention deficits, and mood-related symptoms. The late infancy window (weeks 32–42) showed some of the strongest statistical associations with increased behavioral symptom scores.
About 4 percent of children in the cohort scored within the clinical range on the Behavioral Symptoms Index (BSI) from the Behavior Assessment System for Children, Second Edition (BASC-2), and these elevated scores correlated with the timing of early-life metal exposures as reconstructed from the teeth.
Brain imaging revealed that children with higher early-life metal mixture exposures displayed measurable differences in brain structure and in the integrity and efficiency of white matter connections—patterns the authors describe as persistent neural “fingerprints” of exposure.
Environmental health implications
Many metals measured in the study—such as manganese, zinc, magnesium, and lead—are routinely encountered through food, drinking water, and the built environment. The findings emphasize that the timing of exposure can be as important as the exposure itself.
“Our results suggest prevention strategies should target specific high-risk windows rather than only broadly reducing exposure throughout early life,” said senior author Megan K. Horton, PhD, MPH, Professor of Environmental Medicine at Mount Sinai. Lead author Elza Rechtman, PhD, noted that the study’s precision in identifying vulnerable weeks highlights opportunities for targeted public health action to reduce lifelong harms to brain health.
The authors recommend stronger focus by environmental regulators and public health programs on reducing metal exposure during pregnancy and the first year of life through safer water, food, and housing interventions.
Practical guidance for families and clinicians
The study does not imply a single exposure determines a child’s future. Rather, it shows that reducing metal exposures during pregnancy and infancy may support healthier brain development. Practical steps include ensuring safe drinking water, careful food sourcing and preparation to avoid soil-based contaminants, and minimizing contact with known metal sources such as old lead paint and industrial dust.
Clinicians are encouraged to consider early environmental exposure histories when evaluating developmental and behavioral concerns and to counsel families on exposure-reduction strategies during pregnancy and infancy.
Future directions
This research advances precision environmental health by identifying specific developmental windows that may be most amenable to preventive action. Future studies will expand the list of chemicals measurable in baby teeth, validate results in larger and more diverse populations, and aim to inform policies that better protect brain development during sensitive early-life periods.
Funding: Supported by the National Institute of Environmental Health Sciences and the National Center for Advancing Translational Sciences.
Key Questions Answered:
A: Blood tests provide a snapshot of current exposures. Baby teeth act as a long-lived record, preserving a weekly timeline of metal exposure from mid-pregnancy through the first postnatal year.
A: No. The study shows that timing matters, highlighting weeks of heightened vulnerability. It does not establish that a single exposure determines outcomes, but it points to windows where protective measures could be most beneficial.
A: The researchers recommend “precision prevention”: ensuring safe drinking water, sourcing and preparing foods to limit soil-based contamination, and reducing exposure to known sources such as legacy lead paint and 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 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 et al., published in 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 the most vulnerable periods and the mechanisms involved have been unclear.
This study examined how mixtures of metals experienced during early life relate to brain structure, function, and behavior by using naturally shed baby teeth as biomarkers of exposure. The researchers studied 489 children aged 8 to 14 years and reconstructed weekly levels for nine metals from 20 weeks before birth to 40 weeks after birth.
Behavior was assessed with standardized questionnaires, and brain structure and connectivity were measured with magnetic resonance imaging. Using lagged weighted quantile sum regression, the team identified sensitive developmental windows in which higher metal mixture exposure was associated with more behavioral problems, reduced brain volume, lower global efficiency, and weakened white matter integrity.
The findings indicate that the developing brain is particularly vulnerable to metal exposures in early life, with observable effects persisting into adolescence.