NEW YORK (Reuters Health) – Having difficulty getting pregnant? Perhaps your sofa is to blame. Or your stereo or carpet or any of the things in your house that contain common flame-retardant chemicals known as PBDEs that a new study suggests may be associated with decreased fertility.
PBDEs, or polybrominated diphenyl ethers, are hormone-disrupting pollutants that build up in the blood and tissues.
In a study in the latest issue of Environmental Health Perspectives, researchers found that, for each 10-fold increase in PBDE blood concentration, women experience a 30 percent decrease in the odds of getting pregnant each month.
PBDEs have been associated with reproductive and hormonal effects in animals, but this is the first study to examine their association with human fertility, lead researcher Dr. Kim G. Harley of the Center for Children’s Environmental Health Research at U.C. Berkeley’s School of Public Health in California and colleagues note in their report.
The researchers measured PBDE levels in blood samples from 223 pregnant women enrolled in a long-term study examining environmental exposures and reproductive health. The investigators also asked the women how many months it had taken them to become pregnant.
They found that women with the highest blood concentrations of PBDE took the longest to become pregnant — up to 12 months. The study cut off at 13 months. In addition, the 107 women who were actively trying to become pregnant were half as likely to conceive in any given month if they had high levels of PBDE in their blood.
Experts say most women become pregnant within the first six months of trying. After 12 months of trying with no pregnancy, women will be classified as “infertile,” Harley added, even though they will likely go on to conceive after that. After 12 months of unprotected intercourse, roughly 85 percent of women younger than age 35 will become pregnant, while half of women older than 35 will. Infertility treatment typically doesn’t start until a couple has been trying for a year, with no luck.
“We aren’t looking at infertility, just subfertility, because all of the women in our study eventually became pregnant,” Harley noted in a university-issued statement. “Had we included infertile couples in our study, it is possible that we would have seen an even stronger effect from PBDE exposure.”
Because the study sample included a mostly agricultural population, the researchers controlled for pesticide exposure. They also controlled for other potentially confounding factors, including irregular menstrual cycle, intercourse frequency, smoking, alcohol and caffeine consumption, body weight before pregnancy, and birth control pill use in the year before conception
“This study is the first to report that higher PBDE concentrations in women’s blood are associated with significantly longer time to pregnancy and this finding needs to be replicated in other populations,” the researchers wrote.
“If confirmed, this finding would have strong implications to women trying to conceive given that exposure to PBDEs is nearly universal in the United States and many other countries,” they add.
According to data from the National Health and Nutrition Examination Survey, 97 percent of American adults have detectable levels of PBDE in their blood. Concentrations have been doubling about every five years since the 1970s, noted Harley, and California residents, perhaps because of strict fire regulations, have the highest levels of exposure.
Most of the women in the current study were immigrants from Mexico, where PBDEs are less common. Harley emphasized that the study population actually had somewhat lower PBDE levels in their blood than the general population, although the range varied widely. The women in the study with the highest concentration of PBDEs were the ones who had lived in the United States the longest.
Of the three types of PBDEs that have been developed and used as commercial flame retardants, two have already been banned in several states, including California. These banned PBDEs, however, persist in home products made before 2004.
According to a recent EPA agreement, a third type of PBDE will be phased out by 2013. Until then, the fertility risk of exposure remains present, if unclear. Harley’s study also points to the need to examine fertility effects PBDEs might have on men.
“The bad news,” Harley told Reuters Health in a phone interview, “is that it’s really hard to know which products contain high levels of PBDEs.” Products containing polyurethane foam, like chairs and sofas, can have a wide range of PBDE levels, she said, making it impractical to try to just throw away possible sources of the chemical.
Harley also pointed out that it’s hard to test for PBDEs in the blood except for in a research environment. However, she did acknowledge that the main exposures happen through dust, air, and food. Therefore, she suggests that people concerned about PBDEs use wet mops and/or vacuum cleaners with HEPA filters, wash their hands frequently, and cut down on eating meat, as PBDEs tend to lodge in fatty tissue.
SOURCE: Environmental Health Perspectives, online January 26, 2010