High levels of brominated flame retardants can alter pregnant womens thyroid hormones, which are critical to a babys growth and brain development, according to a California study
By Marla Cone and Environmental Health News | June 21, 2010 | 1
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[pic][pic]HORMONES GOING HAYWIRE:Ubiquitous flame retardants can alter pregnant women's thyroid hormones, possibly affecting a baby's growth and development. Image: health.utah.gov
High levels of brominated flame retardants can alter pregnant women’s thyroid hormones, which are critical to a baby’s growth and brain development, according to a California study published Monday.
The study is considered important because it is thefirst human research showing a link between the ubiquitous chemicals and altered levels of the hormones in pregnant women. The effects on babies are unknown, but some researchers say it may lead to smaller fetuses, and reduce childen's intelligence and motor skills.
“Normal maternal thyroid hormone levels are essential for normal fetal growth and brain development, so our findings could havesignificant public health implications,” said Jonathan Chevrier, a University of California, Berkeley epidemiologist and lead author of the study, which was published in the journal Environmental Health Perspectives.
The flame-retarding chemicals, polybrominated diphenyl ethers, or PBDEs, are widely found in furniture cushions, carpet pads, electronics and other common household items. They havebeen detected in about 97 percent of people tested; in the United States, levels are at least 20 times higher than elsewhere.
The Berkeley epidemiologists tested the blood of 270 pregnant women in California’s Salinas Valley. The study is part of a larger project monitoring the health of pregnant women and children in the valley, which is predominantly a low-income, Mexican-American farmcommunity.
The women’s thyroid-stimulating hormone, or TSH, declined 16.8 percent for every tenfold increase in PBDEs. Low TSH suggests that the thyroid is producing too much hormone on its own. The reductions were found for every type of PBDE.
The high exposures did not lead to clinical hyperthyroidism – a condition involving overproduction of thyroid hormones known to damage fetuses. But theirrate of subclinical hyperthyroidism did increase. For every ten-fold increase of PBDEs among the women studied, their risk of subclinical hyperthyroidism doubled.
Scientists do not know whether the thyroid effects were significant enough to harm their fetuses.
Chevier said pregnant women who are clinically hyperthyroid have an increased risk of miscarriage, premature birth and reduced fetalgrowth. Also, in animal tests, hyperthyroidism in the mothers results in damaged brain development of their offspring. But it is unclear whether subclinical hyperthyroidism – the effect linked to the flame retardants – can damage fetuses.
Research is already in the works to try to address that.
UC Berkeley epidemiologist Brenda Eskenazi, the study’s principal researcher, said the team hastested the Salinas children for neurodevelopmental effects such as reduced mental skills, with results expected this summer. In addition, they plan to look for effects on fetal size and weight.
“The thyroid hormone findings we have seen could have an effect on fetal growth and we will be looking for that,” she said.
Chevrier said the amounts of flame retardants found in the Salinas women weresimilar to national averages. As a result, the findings “raise concerns about women exposed to higher levels of PBDEs, which could be made clinically hyperthyroid,” he said.
Women in California on average have PBDE levels that are twice as high as the Salinas women. Californians have the highest documented exposures in the world, most likely because the state has the most stringent flammability...