According to a study conducted by researchers at the Harvard T.H. Chan School of Public Health, women highly contaminated by flame retardants (significant quantities of flame retardants found in the blood) are at a higher risk of suffering from thyroid imbalances. And the risk can be even greater in postmenopausal women.
This new study is the first to suggest a link between polybrominated diphenyl ethers (PBDEs), that is flame retardants, and an increased risk of thyroid problems in menopausal women, in a representative sample of women across the United States. Thyroid problems include hyperthyroidism, goiter, or Hashimoto's disease.
The study was published online on May 23, 2016, in the journal Environmental Health. "These chemicals are everywhere, in the blood of polar bears or eagles, as well as in the blood of humans on every continent," said Joseph Allen, assistant professor at the Harvard Chan School, in charge of evaluating chemical exposure risks, and lead author of the study. "This almost constant exposure implies that we are all part of a global experiment on the impact chemicals can have, on how they disrupt the endocrine system of our bodies."
PBDEs have been used as flame retardants for decades, largely for furniture and in quantities that can represent up to 20% of the product's weight. Over time, they have leached into the air, settled in household dust, schools, and outdoors, and accumulated in our bodies. Previous studies have shown that these chemicals accumulate in adipose tissues and interfere with hormonal functions, including thyroid hormones. Since estrogen levels are known to regulate thyroid hormones, researchers have suggested that postmenopausal women may be particularly vulnerable to the effects of PBDEs on the thyroid.
Researchers analyzed a sample of women nationwide during the NHANES study (National Health and Nutrition Examination Survey). They compared the levels of four common PBDEs in blood samples taken from these women in 2003-2004, with their history of thyroid problems. Researchers found that overall, women were about five times more likely than men to have a thyroid problem. The percentage ranged from 13 to 16% in women and from 2 to 3% in men.
Women with the highest concentration of flame retardants in their blood were much more likely to develop thyroid problems than those with lower concentrations. The magnitude of the effect was doubled in postmenopausal women. "In our bodies, these flame retardant chemicals resemble the endogenous hormones produced by our bodies and function exactly like them. So should we be surprised to observe downstream effects on the health of women with high levels of chemicals in their bodies? I don't think so. It's very logical and to be expected," says Allen. One limitation of the study is that it was unable to determine the effects of new flame retardant chemicals as they have not yet been examined by the NHANES study.
According to an article by Todd Datz, Harvard T.H. Chan School of Public Health.. Références : PBDE flame retardants, thyroid disease, and menopausal status in U.S. women. Joseph G. Allen, Sara Gale, R. Thomas Zoeller, John D. Spengler, Linda Birnbaum, Eileen McNeely, Environmental Health, online May 23, 2016, doi: 10.1186/s12940-016-0141-0. cancer-environnement.fr. Autres sources : cancer-environnement.fr.