A new study has found women who are exposed to a common chemical that's used as a flame retardant may take longer to become pregnant.
The chemicals, called PBDEs (polybrominated diphenyl ethers), are found in a variety of products including foam furniture, electronics, fabrics, carpets, plastics and other common household items and have been linked to a variety of health problems, researchers say.
"Women with high PBDE levels were 30 to 50 percent less likely to become pregnant in any given month than women with lower levels," said lead researcher Kim Harley, an 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.
"Although these chemicals are being phased out of new products, they will be around for a long time," she added.
The report is published in the Jan. 26 issue of Environmental Health Perspectives.
For the study, Harley's team measured PBDE levels in blood samples from 223 pregnant women who took part in a study at the Center for the Health Assessment of Mothers and Children of Salinas, which looked at environmental exposures and reproduction.
Among these women, concentrations of PBDEs were slightly lower than in the general U.S. population. The researchers speculate that this may be due to the fact that many of the women grew up in Mexico where exposure to PBDEs are limited.
Limiting their analysis to women who were trying to become pregnant, Harley's group found that women with high levels of PBDE in their blood were half as likely to become pregnant in any given month. In fact, for every tenfold increase in blood levels of PBDEs, the odds of becoming pregnant were reduced 30 percent.
These findings held even after the researchers took into account exposure to pesticides, irregular menstrual cycles, frequency of intercourse, weight, use of birth control pills in the year before conception, smoking, and alcohol and caffeine use.
The reasons for the chemical's effect on pregnancy isn't clear, Harley said. Harley noted that very little research has been done in humans. However, animal studies have found a variety of health effects from these chemicals including pregnancy problems, she said.
These animal studies have found that PBDEs can harm neurodevelopment, lower thyroid hormones and change levels of sex hormones. High or low thyroid hormone levels can disrupt normal menstrual patterns in humans, Harley noted.
PBDEs became common after the 1970s with new fire-safety standards in the United States. Studies have found widespread PBDE dust in homes. These chemicals are known to leach into the environment and accumulate in human fat cells, Harley said.
Studies have found that 97 percent of Americans have detectable levels of PBDEs in their blood. These levels are 20 times higher than found in Europeans. According to Harley, Californians have some of the highest exposures to these chemicals due to strict fire laws in that state.
Harley said the best way to reduce your exposure to PBDEs is to reduce your exposure to house dust, by using a wet mop and vacuuming with a filtered vacuum cleaner and washing your hands often.
While there are some 209 different formulations of PBDEs, only three -- pentaBDE, octaBDE and decaBDE -- have been developed for commercial use as flame retardants. PentaBDE and octaBDE have both been banned in several states, including California, but are still in products made before 2004.
Last month, the U.S. Environmental Protection Agency announced that three major manufacturers of decaBDE will phase out this product by 2013.
Although PBDEs are being phased out, other chemicals are taking their place. "We know even less about the newer flame-retardant chemicals that are coming out," Harley said. "There has been even less research on these chemicals."
Dr. George Attia, an associate professor of reproductive endocrinology and infertility at the University of Miami Miller School of Medicine, said that "there are a lot of other factors that would affect the fertility of these women, not only PBDEs."
Attia thinks these findings need to be proven in prospective studies that can control for the complicated set of factors that affect fertility.
However, Attia does not exclude the possibility these chemicals affect fertility.
"Common sense says avoid this substance, but we don't have data to substantiate that, but common sense will tell you be careful and be aware that there is something out there about this stuff," he said.