Health/Toxics: Flame Retardants

A growing body of research in laboratory animals has linked PBDE exposure to an array of adverse health effects including thyroid hormone disruption, permanent learning and memory impairment, behavioral changes, hearing deficits, delayed puberty onset, decreased sperm count, fetal malformations and, possibly, cancer. Research in animals shows that exposure to brominated fire retardants in-utero or during infancy leads to more significant harm than exposure during adulthood, and at much lower levels. And some of these studies have found toxic effects at levels lower than are now detected in American women. Many questions remain, but new evidence raises concerns that low levels of PBDE exposure pose a significant health risk to developing animals, and may pose a health risk to fetuses, infants and children at levels currently detected in American women.

Even short-term exposures to commercial PBDE mixtures or individual congeners can alter thyroid hormone levels in animals, and the effects are more profound in fetuses and young animals than in adults. These results aren't surprising, but are ominous as data in humans indicate that pregnancy itself stresses the thyroid, and developing fetuses and infants do not have the thyroid hormone reserves adults do to help buffer insults to the system.

Most studies on thyroid hormone disruption by PBDEs have been short-term, with exposures of 14 days or less. The real question is how low doses over the long term affect the body's thyroid hormone balance. The answer is important, because the entire U.S. population is exposed daily to low levels of PBDEs, and studies of other thyroid hormone disrupters have found that long-term exposures can cause more serious harm at lower levels of exposure. Although no direct link could be made, one study found higher rates of hypothyroidism among workers exposed to brominated fire retardants on the job.