Almost a decade after manufacturers stopped using certain chemical flame retardants in furniture foam and carpet padding, many of the compounds still lurk in homes. New work to be presented today reaffirms that the chemicals may also still be hurting young children who were exposed before they were born.
Researchers investigating the health impacts of prenatal exposure to flame retardants collected blood samples from 309 pregnant women early in their second trimester. Spikes in the levels of one class of flame retardant, polybrominated diphenyl ethers (PBDEs) correlated with behavior and cognition difficulties during early childhood.
The researchers tracked children through the first five years of their lives, looking at a battery of tests for IQ and behavior. They found that children of mothers who had high PBDE levels during their second trimester showed cognition deficits when the children were five years old as well as higher rates of hyperactivity at ages two to five. If the mother’s blood had a 10-fold increase in PBDEs, the average five-year-old had about a four-point IQ deficit. “A four-point IQ difference in an individual child may not be perceivable in…ordinary life. However, in a population, if many children are affected, the social and economic impact can be huge due to the shift of IQ distribution and productivity,” says lead author Aimin Chen, an assistant professor of environmental health at the University of Cincinnati College of Medicine. The findings, based on women and children from Cincinnati, will be presented May 6 at the annual meeting of the Pediatric Academic Societies in Washington, D.C. The unpublished results have been submitted to a peer-reviewed journal, but the paper has not yet been accepted.
Chen’s team did not track the children’s PBDE blood levels after they were born, so the deficits could also have resulted, at least in part, from the additional exposures to the chemical that the children encountered directly after they were born. Chen says that although the lack of blood level data in the children is a limitation, other researchers have measured both mother and child PBDE levels and found similar deficits, strengthening his conclusions. The team also found that association of PBDEs and child IQ and behavior did not result from the mother’s blood levels of lead, a well-known neurotoxic metal.
Although preliminary, Chen’s findings are similar to two recent large U.S. studies that showed associations between prenatal exposure to flame retardants and developmental deficits and reduced IQ. One of those earlier studies, from the University of California, Berkeley, looked at children and PBDE levels through age seven, and was published online last fall in Environmental Health Perspectives. That study measured PBDEs both in pregnant women and in the children themselves. It showed that there is a relationship between high PBDE exposures in utero and deficits in children’s IQ, fine motor function and attention. Though suggestive, none of the studies have proved a definitive cause-and-effect link in humans, however.
Scientists believe that in humans PBDEs can lodge themselves in bodily lipids when contaminated air is inhaled or tainted dust swallowed, although exactly how they may wreak havoc inside the body remains unknown. Tests on animals suggest that the chemicals disrupt the endocrine system. The chemical structure of PBDEs strongly resembles thyroid hormones, and they affect thyroid regulation and decrease the level of thyroid hormones in the blood of animals. These hormones drive growth and development—in particular, brain development. Animal studies have also found that exposure to PBDEs in the womb and via nursing may damage the thyroid system and alter newborns’ brains.