Jan. 26, 2010 -- Women with higher blood levels of flame retardants known as PBDEs, found in some household objects, took about twice as long to become pregnant as women with lower blood levels, according to a new study.
''For every tenfold increase in PBDEs in the blood, we saw a 30% to 50% decrease in the odds of becoming pregnant in any given month," says study researcher Kim Harley, PhD, adjunct assistant professor of maternal and child health and associate director of the Center for Children's Environmental Health Research at the University of California Berkeley School of Public Health. The study appears online in Environmental Health Perspectives.
But a spokesperson for the industry said that the study findings are limited to PBDEs no longer used in new production and the environmental levels of those PBDEs are expected to decline over time.
PBDEs became common after the 1970s, when new fire safety standards were implemented in the United States; the compounds are found in furniture, carpets, electronics, plastic, and other household items.
Flame Retardants and Fertility: Study Details
Harley and her colleagues interviewed 223 pregnant women living in northern California, asking them how many months it took them to become pregnant. They measured the PBDE levels from blood samples taken near the end of the second trimester.
PBDEs are typically measured from the blood in nanograms per gram of fat, Harley tells WebMD. The levels found in the women ranged from 3 to 1,200 nanograms per gram of fat.
''Women with a higher exposure to a commonly used [in the past] flame retardant took longer to become pregnant," she says. The higher the levels, the longer the time to pregnancy.
The median time to pregnancy was three months (half took longer, half less), but 15% took longer than 12 months to conceive. ''But some took 10 years or more," Harley says.
The PBDEs found in the highest concentration were four types of penta-BDEs. In the U.S., the manufacturer of penta and octa-BDEs stopped production in 2004, but the chemicals remain in older products. Because the compounds are not chemically bound, they can leach out of products.
Exactly how the chemicals may affect time to pregnancy isn't known, but experts say one way may be to disrupt thyroid functioning. Low and high thyroid levels can alter normal menstrual patterns and thus affect fertility.
The women's levels, overall in the study, were actually a bit lower than the national average, Harley says. She notes that about 97% of Americans have detectable PBDE levels in their blood, citing a survey. Californians are likely to have the highest levels because of the state's strict flammability requirements for products.
The women in the study were living in a low-income, predominantly Mexican-immigrant community. Most were recent immigrants from Mexico, where PBDE use is lower, she says.
Flame Retardant Exposure and Time to Pregnancy: Expert Views
The new study backs up some lab findings, says Sonya Lunder, a senior analyst at the Environmental Working Group, which has also studied the compounds.
Of the results, she says: “A 50% decrease in the odds of becoming pregnant is massive."
The study is scientifically sound, says Ruthann Rudel, director of research for Silent Spring Institute, a Boston-based organization that conducts research on environmental factors affecting women's health.
The researchers controlled for other factors that may affect fertility, she says, such as pesticide exposure, and still found an effect of the chemicals.
Flame Retardant Exposure: Industry Weighs In
A representative from the flame retardant industry took exception to the findings. ''The study is limited to penta and octa-[PBDEs] and does not include deca, the only PBDE currently in use," says John Kyte, a spokesman for the Bromine Science and Environmental Forum, an industry group based in Washington, D.C.
As a result, he says, ''the study is not applicable to all PBDEs or to PBDEs generally." Each of the PBDE forms is different, he says.
He says penta and octa-PBDEs are no longer in use in the U.S., so exposure to them should decline over time.
Response to Industry View
In response, Harley says that deca (also known as BDE-209) was not measured because the CDC lab didn't have the analytical capability to measure it at the time of the study. ''So we have no idea what the deca levels are in these women," she says.
Although it is true the PBDEs found to be associated with delayed time to pregnancy in her study have been banned, she says many older products still contain the penta chemicals ''and we expect that our exposure to penta will continue over the next several years."
Flame Retardants: Advice for Women
Even though penta and octa-PBDEs have been phased out, Harley says they remain in older household furniture and can still leach out.
She can't specify a ''safe'' level of exposure based on her study, but she and others suggest that women follow a few simple steps to reduce exposure.
Two main sources of the chemicals are found in food and in household products. "Choose meat, fish, and dairy lower in fat," she says. The compounds are fat-soluble, she says.
Don't reupholster foam-filled furniture yourself, Lunder says. The PBDEs are in the foam and can leach out. Limit exposure to old carpet padding, which is often recycled foam, she says.
''When you are replacing carpet, get women and children out of the house," she says. The exposure concern is not limited to its effect on fertility, but also to children's development.
Harley is now focusing on the effects of PBDE exposure on the children.