Researchers at UC Davis Health found in the largest study of its kind that exposure to organophosphate ester flame retardants during pregnancy was linked to preterm birth, particularly in women. The chemicals were also associated with higher birth weight, raising concerns for an increased risk of obesity. This significant new research study was published in Environmental Health Perspectives.
„The importance of this study is in revealing the potential impact of exposure to environmental chemicals during pregnancy on fetal development. Our findings inform our understanding of how these chemicals may silently create enduring challenges for the health of the next generation.“
Jiwon Oh, lead author of the study and postdoctoral scholar in the Department of Public Health Sciences, Division of Environmental and Occupational Health
OPEs were phased in as polybrominated flame retardants were phased out
In the mid-2000s, a class of chemicals, polybrominated diphenyl ether flame retardants, was gradually phased out due to concerns about their potential toxicity.
Organophosphate esters or OPEs gradually took their place. They are commonly used today in foams found in furniture, baby products, electronic goods, textiles, and building materials to prevent fires and make plastics more flexible.
Due to their chemical structure, OPEs degrade slowly and become part of dust. Individuals are exposed to OPEs through their skin or by ingesting or inhaling indoor dust.
The chemicals are commonly detected in urine samples from the general US population, including samples from pregnant women. In this study, researchers wanted to determine what impacts OPEs might have on fetal development during pregnancy.
Research conducted across the US
Researchers from multiple institutions, including UC Davis, conducted the study. It included 6,646 mother-child pairs from 16 cohorts in the US from the Environmental Influences on Child Health Outcome (ECHO) study. Participants came from different regions and had diverse backgrounds.
Researchers measured nine OPE biomarkers in urine samples from pregnant women collected between 2007 and 2020, with most samples being collected in the second and third trimesters.
They assessed birth outcomes, including gestational age at birth and birth weight, primarily from medical records or parental reports.
Preterm births and higher birth weight
Researchers found that three of the nine OPEs were associated with an increased risk of preterm birth (before 37 weeks of gestation), particularly in female newborns. These included:
Preterm births could pose risks of health issues for infants, including respiratory and feeding problems, developmental delays, cerebral palsy, as well as vision and hearing problems.
Three other OPEs –; Bis(1-chlor-2-propyl)phosphate, Bis(2-methylphenyl)phosphate, and Dipropylphosphate –; were associated with higher birth weight at gestational age.
High birth weight is linked to obesity in children, increasing the risk of health conditions such as diabetes and cardiovascular diseases.
„Over 6,000 pregnancies were included in this study, and with such a large study, we are very confident in our findings,“ said Deborah Bennett, principal author of the study and professor of environmental health at the Department of Public Health Sciences. „Policy options to reduce exposure to organophosphate ester flame retardants should be considered.“
OPEs are metabolic and endocrine-disrupting chemicals
Researchers found that OPEs can influence thyroid hormone levels and cause inflammation and oxidative stress, which could play a role in preterm births. OPEs are also endocrine disruptors and may contribute to abnormal placental development, with effects varying by fetal sex.
„As OPEs come from building materials, textiles, electronics, and other products, consumers cannot choose products that do not contain OPEs,“ said Oh. „Only policy changes and regulations can mitigate their hazard.“
University of California – Davis Health
Oh, J., et. al. (2024) Associations of exposure to flame retardant organophosphate esters during pregnancy with gestational length and fetal growth: Environmental Influences on Child Health Outcome (ECHO) program. Environmental Health Perspectives. doi.org/10.1289/EHP13182.