NIEHS director reacts to study of pregnant women, urges more investigation of flame retardants

June 22, 2010

The director of the national institute that oversees environmental health research said Monday that a new study raises many important questions about how flame retardants in common household items may pose a threat to the health of pregnant women and their infants.

The study published Monday reported that high levels of brominated flame retardants can alter pregnant women’s thyroid hormones, which are critical to a baby’s growth and brain development. It is the first human research showing a link between the ubiquitous chemicals and altered levels of the hormones in pregnant women.

"Clearly it is something that should be looked at further," Linda Birnbaum, director of the National Institute of Environmental Health Sciences, said in an interview with Environmental Health News. "I think the change [in the women’s hormones] is probably real. It’s in agreement with other human studies in other [non-pregnant] adults and it’s the first study showing a pretty significant effect."

The Berkeley epidemiologists tested the blood of 270 pregnant women in California’s Salinas Valley as part of  a larger project monitoring the health of pregnant women and children in a low-income, Mexican-American farm community.

The women’s thyroid-stimulating hormone, or TSH, declined 16.8 percent for every tenfold increase in brominated flame retardants, which are found in furniture, carpet padding, electronics and other consumer products. Low TSH suggests that the thyroid is producing too much hormone on its own.

The high exposures did not lead to clinical hyperthyroidism – a condition involving overproduction of thyroid hormones known to damage fetuses. But their rate of subclinical hyperthyroidism did increase. For every ten-fold increase of PBDEs among the women studied, their risk of subclinical hyperthyroidism doubled.

“It may mean we need some more investigation of what the thyroid condition is of these women. Are they really on their way to being hyperthyroid?” Birnbaum said.

Normal maternal thyroid hormone levels are essential for normal fetal growth and brain development, so the Berkeley researchers said they are concerned that their findings could mean there are significant health effects from exposure to PBDEs, polybrominated diphenyl ethers.

Birnbaum stressed that there is "no good information" yet about what slightly-low levels of thyroid-stimulating hormones means for the health of a fetus.

She said she is contacting the Berkeley scientists, led by epidemiologist Brenda Eskenazi, to encourage them to look at the thyroid levels of the infants, too. “We need to understand what’s happening with the infants, not just the mom,” she said.

The potential health effects on the Salinas babies has not yet been studied by the Berkeley team. But other research, including a study in New York City, has linked reduced IQs, attention problems and other neurodevelopmental effects with exposure to the flame retardants.

The new findings also most likely will have implications for how scientists test PBDEs on lab animals. Birnbaum said researchers are perplexed about why the thyroid-stimulating hormones decreased in the women as their exposure increased, but in lab animals, the opposite has been found.

“We need to understand why our animal models don’t agree with the human studies,” Birnbaum said. “I think this is not the result people expected."

Americans - particularly Californians - have the highest levels of PBDEs in the world. The levels in their blood and breast milk were doubling every five years until two of the most common compounds were banned in 2004. The chemicals build up in the environment, in the food supply and in human bodies. Household dust and food are the major sources of people's exposure.

Birnbaum said in an interview last November that "there is no convincing evidence that PBDEs are declining in people or wildlife in the United States" despite the bans. "It's too soon."

The reductions in thyroid-stimulating hormone were found in the pregnant women with every PBDE tested.

But Birnbaum said she was disappointed that the researchers did not have data on deca, a type of PBDE still in use, and other higher-brominated flame retardants, which also accumulate in human bodies.

New brominated and chlorinated compounds are being used today as flame retardants, and in the earlier interview, Birnbaum said "we kind of jump from the proverbial frying pan into the fire" by allowing use of the new compounds without more substantial testing. She is particularly concerned about compounds called hydroxylated PBDEs, which are metabolites of some flame retardants.

“These are compounds that have the potential to be thyroid disruptors," she said Monday.

Before being named director of NIEHS in December, 2008, Birnbaum was head of experimental toxicology at the U.S. Environmental Protection Agency, and she was particularly interested in the sources and toxicity of PBDEs. As director of NIEHS, she coordinates and oversees new environmental health research.

 For the full story on the new study, click here.

NIEHS director reacts to study of pregnant women, urges more investigation of flame retardants, by Environmental Health News, is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Based on a work at www.environmentalhealthnews.org.