New York, NY, Apr 25: 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.
This research was supported by the National Institute of Environmental Health Sciences and the National Center for Advancing Translational Sciences.
