New York, NY (February 18, 2026)—Babies born between 2003 and 2006 were exposed to many more "forever chemicals" before birth than scientists previously understood, according to new research published in Environmental Science & Technology.
Thousands of these chemicals, known as per- and polyfluoroalkyl substances or PFAS, remain in use today, and their human health effects are poorly understood—making it crucial to better understand cumulative PFAS exposure in utero.
The study, led by Shelley H. Liu, PhD, Associate Professor of Population Health Science and Policy at the Icahn School of Medicine at Mount Sinai, is the first to use a data science–based method to estimate a newborn's total PFAS exposure, drawing on advanced chemical detection in umbilical cord blood.
PFAS are a large class of man-made chemicals used in products such as nonstick cookware, stain-resistant fabrics, food packaging, and firefighting foams. They are often called "forever chemicals" because they persist in the environment and the human body.
What the researchers found
The researchers measured PFAS in archived umbilical cord blood samples collected between 2003 and 2006 from 120 babies in the HOME Study , based in Cincinnati. Looking back two decades allowed the researchers to create a new tool that can be linked to health outcomes in the now-adolescent study participants, which will be a focus of future research.
Using a newer, non-targeted chemical analysis method—a technique that scans for hundreds to thousands of chemicals at the same time rather than testing for a short, predefined list—the research team detected many more PFAS chemicals in umbilical cord blood than traditional testing methods capture, including newer and understudied compounds. The researchers found 42 confirmed or putatively identified PFAS chemicals in cord blood using this non-targeted approach. Many of these PFAS are not commonly screened in traditional testing methods and their health effects are unknown. The results showed that infants are exposed to a wide range of PFAS, including perfluorinated chemicals, polyfluorinated chemicals, and fluorotelomers, before birth.
The researchers created PFAS-omics burden scores, using item response theory methods, to summarize total exposure to PFAS. The PFAS-omics scores can be interpreted as a snapshot in time of a baby's overall PFAS exposure.
Importantly, when researchers used this broader PFAS assessment, they did not observe exposure differences between babies born to first-time mothers and those born to mothers with previous pregnancies—a difference that earlier studies had reported using more limited PFAS panels.
"Our findings suggest that how we measure PFAS really matters," said Dr. Liu, first and co-corresponding author of this study. "When we look more comprehensively, we see that babies are exposed to far more PFAS chemicals before birth than we previously realized—and some of the patterns we thought we understood may change."
Why this matters
Pregnancy is a period of heightened vulnerability. Previous research has linked prenatal PFAS exposure to low birth weight, preterm birth, altered immune responses to vaccines, metabolic changes, and other developmental concerns.
"Our study helps show that prenatal PFAS exposure is more complex and widespread than earlier studies suggested," Dr. Liu said. "Understanding the full picture is essential if we want to protect child health and reduce preventable environmental risks."
The American College of Obstetricians and Gynecologists has identified reducing exposure to toxic environmental chemicals like PFAS as a "critical area of intervention."
What this means for clinicians and patients today
PFAS exposure is not currently measured in routine clinical care, despite growing evidence that these chemicals affect multiple aspects of health.
This research introduces a new way to estimate cumulative PFAS exposure, which could eventually help clinicians:
- Identify individuals with higher exposure burdens
- Monitor at-risk populations more closely
- Inform future preventive medicine strategies
"For now, this work helps lay the scientific foundation," Dr. Liu said. "Our goal is to move toward earlier identification and prevention, especially during sensitive windows like pregnancy."
What's next
The research team plans to:
- Study whether higher cumulative PFAS exposure in early life leads to negative health outcomes
- Investigate the health effects of new and understudied PFAS chemicals identified in cord blood
- Further refine tools that can support primary disease prevention
Funding: National Institutes of Health
Collaborating Institutions: University of Michigan, Fordham University, Brown University, University of Cincinnati, University of Pennsylvania, Yale University, Simon Fraser University
