28 January 2010

Sub-fertility linked to flame retardant exposure

by Kate Melville

The first study to investigate the impact of flame retardants - commonly found in household consumer products - on human fertility has linked exposure to the chemicals with reduced fertility in women. Researchers at the University of California, Berkeley, who conducted the study said that a 10-fold increase in the blood concentration of any of the four most common chemicals (PBDEs) resulted in a 30 percent decrease in the odds of becoming pregnant each month. "These findings need to be replicated, but they have important implications for regulators," said the study's lead author, Kim Harley.

PBDEs (polybrominated diphenyl ethers) are a class of organobromine compounds that became commonplace after the 1970s when new fire safety standards were implemented in the United States. The flame retardants are used in foam furniture, electronics, fabrics, carpets, plastics and other common items in the home.

Previous studies have found widespread contamination of house dust by PBDEs, which are known to leach out into the environment and accumulate in human fat cells. Worryingly, 97 percent of the U.S. population have levels of PBDEs in their blood that are 20 times higher than in their European counterparts. According to the researchers, residents in California are among those experiencing the highest exposures.

The researchers measured PBDE levels in blood samples from 223 pregnant women and recorded the number of months it took for them to get pregnant. When the analysis was limited to women who were actively trying to become pregnant, the researchers found that they were half as likely to conceive in any given month if they had high levels of PBDE in their blood. "We aren't looking at infertility, just sub-fertility, because all the women in our study eventually became pregnant," explained Harley. "Had we included infertile couples in our study, it is possible that we would have seen an even stronger effect from PBDE exposure."

It is not clear how PBDEs might impact fertility. A number of animal studies have found that PBDEs can impair neurodevelopment, reduce thyroid hormones, and alter levels of sex hormones. Both high and low thyroid hormone levels can disrupt normal menstrual patterns in women.

"Although several types of PBDEs are being phased out in the United States, our exposure to the flame retardants is likely to continue for many years," said co-researcher Brenda Eskenazi. "PBDEs are present in many consumer products, and we know they leach out into our homes. In our research, we have found that low-income children in California are exposed to very high levels of PBDEs, and this has us concerned about the next generation of Californians."

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Source: University of California - Berkeley