TUESDAY, Aug. 30, 2011 (HealthDay News) -- A flame retardant that was phased out of use but is still present in older furnishings is linked to lower birth weights in newborns of women exposed to it during pregnancy, a new study suggests.
Evaluating levels of PBDEs -- or polybrominated diphenyl ethers -- in blood samples of 286 pregnant women, researchers from the University of California, Berkeley School of Public Health found that every 10-fold increase was tied to a 4.1-ounce drop in the birth weight of their babies.
"The good news is, these chemicals aren't being used anymore. But the bad news is, they're in things we don't replace very often," said study author Kim Harley, an adjunct assistant professor of maternal and child health and associate director of University of California Berkeley's Center for Environmental Research and Children's Health.
"Most of us are exposed to PBDEs and 97 percent of us have detectable levels," said Harley, adding that the research was the first large population-based study of its type.
In the United States and Europe, PBDEs were phased out of use in new products in 2004, but they are still found in older foam furniture, cars, high chairs, strollers, bedding and other goods. The chemicals are not chemically bound into products, she said, meaning they can leach into the environment.
The study, published Aug. 30 in the American Journal of Epidemiology, found a shift toward lighter birth weights in women exposed to the chemicals. But Harley noted that very few babies in the study were born weighing less than 5.5 pounds, the threshold below which infants are considered low birth weight and more likely to suffer social and cognitive delays.
Most of the women were Latinas from low-income families who participated in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) longitudinal study, which examines environmental exposures and reproductive health in an agricultural community. Earlier CHAMACOS research associated PBDE exposure to reduced fertility and altered thyroid hormone function in women.
Although it was difficult to pinpoint why the flame retardant would prompt lower birth weights, Harley said that anything that affects thyroid hormone levels might compromise maternal weight gain.
"If mothers don't gain as much, babies can be smaller," she said, adding that PBDEs are believed to be ingested orally rather than inhaled or absorbed, so stringent hand-washing and vacuuming can help control the chemicals' dispersal.
Jackson Morrill, director of the American Chemistry Council, said the study's link between PBDEs and birth weight was no larger than it might be due to chance once the authors implemented "proper controls" in the research, including factoring in different maternal weight gains or thyroid hormone levels. The authors also noted such a limitation in their paper.
"The authors themselves noted that the effect of maternal weight gain . . . could impact the study's outcomes," Morrill said. "The negative associations were not statistically or clinically significant, meaning that they are unlikely to have implications for human health."
Harley acknowledged that such factors could skew study results and that the study results should be replicated to confirm the link.
The authors also said that the PBDE levels in the women studied were lower than those in the overall U.S. population. Women with higher PBDE exposures might face a higher risk of delivering a low birth weight baby, they said.
"Obviously, it's important that our homes are safe from fire," Harley said. "But we need to be aware of that balance."
The U.S. Environmental Protection Agency has more about chemicals and children's health.