Furniture cushions, carpet padding and other household items contain
hormone-disrupting flame retardants called polybrominated diphenyl ethers,
or PBDEs. Two of the most widely used compounds have been banned in the
United States since 2004, but they remain ubiquitous in the environment,
inside homes and in the food supply.
Epidemiologists from the University of California at Berkeley studied 223
pregnant women in California?s Salinas Valley, an agricultural community
with predominantly low-income, Mexican immigrants.
More than 97% of the women had PBDEs in their blood, and those with high
levels were half as likely to conceive in any given month as the women with
?This study provides the first evidence that PBDEs may impact human
fertility,? wrote the authors, led by epidemiologist Kim Harley, in the
study published online in Environmental Health Perspectives. "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."
Harley said ?the results are surprisingly strong.?
?These findings need to be replicated, but they have important implications
for researchers,? she said.
Each ten-fold increase in a woman?s blood was linked to a 30 percent
decrease in her odds of getting pregnant.
Previously, laboratory tests have found altered male hormones and reduced
sperm counts in animals exposed to PBDEs. But this study is the first to
find reduced human fertility.
?Very little research? related to the flame retardants has been conducted in
humans, Harley said.
The researchers do not know how the chemicals may be reducing fertility.
They did not study the fathers, who probably also were highly exposed, so it
is possible that the men?s fertility was reduced, not the women?s,
particularly since it is males who are harmed in the animal tests. Some
PBDEs mimic estrogen, while others can block testosterone.
Dr. Arnold Schecter, a University of Texas School of Public Health
environmental scientist who was not involved in the study, said even though
nearly all the women in the study were Hispanic, "the results might be
generalizable to many American women."
"Elevated levels of PBDEs might be a risk factor for reduced fertility,"
said Schecter, who studies how people are exposed to the flame retardants.
None of the women - chosen for the research because they were pregnant -
were infertile, and they conceived, on average, after three months.
But the chemicals may be pushing some women into the ranks of the
sub-fertile, which means it is difficult to conceive. About 15 percent of
the women in the study took longer than 12 months to conceive.
More than 2.1 million couples in the United States are infertile, according
to the Centers for Disease Control and Prevention.
?Because exposure to PBDEs is ubiquitous in industrialized nations, even
small decreases in fecundability may have wide-reaching public health
impacts,? the scientists said in their study.
The tests measured the chemicals in the women's blood while they were
pregnant, so their levels when they were trying to conceive could have been
higher or lower. A similar study should be done in women before pregnancy,
The PBDE study was part of a decade-long project by the UC Berkeley
scientists to examine whether environmental factors are harming the health
of Salinas Valley mothers and children. The women are highly exposed to
pesticides, which also have been shown to reduce fertility, but the
researchers controlled for pesticide exposure in their study, as well as
length of time in the United States, smoking and other potential factors.