Although industrial chemicals called PCBs have been banned for more
than three decades, a new study suggests that the pollutants could be
making it harder for some people to have a baby today.
with high levels of certain chemicals in their bodies took about 20%
longer to conceive compared with those with lower exposures, says the
study from the National Institutes of Health.
That type of delay
is similar to the effects of other factors known to reduce fertility,
such as smoking, obesity and older age, according to the findings,
published today in Environmental Health Perspectives.
or polychlorinated biphenyls, were widely manufactured from 1929 to
1979, with hundreds of uses, such as coolants and lubricants in
electrical equipment, according to the Environmental Protection Agency.
they're no longer manufactured, PCBs still may be present in older
products, such as caulking, oil-based paint, floor finish and
PCBs persist for years in the environment - in soil, water and the
food chain - as
well as in body fat, the EPA says. PCBs also are found in breast milk.
Studies have shown that PCBs and other chemicals, such as the banned pesticide DDT, can
alter the hormone system, according to the Natural Resources Defense Council, an environmental
People can reduce their future exposure to PCBs by limiting their consumption of animal
products, especially fatty meat, says study author Germain Buck Louis, a researcher at NIH, which
funded the study. Yet because these and other chemicals are stored in fat, it's not possible to completely
eliminate the pollutants, says Shanna Swan, a professor at the Mount Sinai School of Medicine in
Swan called the $10 million project "an amazing study" and "unprecedented in its cost,
scope and details."
Researchers tried to contact more than 424,000 households, in order to find 500 couples
who were going to try to conceive a baby within the next two months.
The study followed the
couples for a year, and followed women through the end of any pregnancies. Only 0.1% of couples
contacted were planning to try to conceive in that time, Louis says.
Scientists asked couples to provide blood and urine samples before conceiving, as well as
keep daily diaries, undergo frequent interviews and pregnancy tests.
of 63 environmental chemicals. Virtually everyone had detectable
levels of PCBs and a breakdown product of the banned pesticide DDT,
The couple's chances of conceiving each month then were calculated
and showed that the likelihood
of a pregnancy fell by about 20% among men and women with high
exposure to certain types of PCBs.
Louis found that five chemicals affected women's fertility, along with 12 chemicals that
"People always look at women, but we need to be looking at the men, too," for questions
about infertility, she says.
Other environmental pollutants also were related to a lower chance of conceiving. Women
with high levels of a flame retardant also had a 20% lower chance of conceiving. Men with high
levels of a breakdown product of the pesticide DDT also had a 17% lower rate of conception, the
DDT has been banned in the USA since 1972, but is still used in other countries,
according to the EPA.
In another study published in June, Louis and her colleagues also found that couples took
longer to conceive when men had high levels of lead in their blood.
Louis says she hopes her findings won't further stress couples trying to conceive. She notes
that 81% of couples conceived within 12 months.
One of the study authors, Anne Sweeney of Texas A&M Health Science Center, hopes to
follow the children, as well. In future papers, Louis says she hopes to evaluate whether
the couples' consumption of such things as vitamins, alcohol or caffeine affected their fertility.
Although the study was ambitious and carefully designed, authors called its results
"preliminary." A study such as this can't definitively prove that high chemical exposures delayed
pregnancy, says Kathryn Murray St. John, spokeswoman for the American Chemistry Council.
"Many factors can affect when or if a pregnancy occurs and, while this study attempted to
address some of those outside issues, not all were taken into account," she says. "The
authors themselves note that the study has significant limitations, including lack of data on
specific exposures to some chemicals. Given the large number of statistical analyses involved in
this report, it is not surprising that some associations were found."
the paper, authors acknowledge that their findings will be more
convincing if other
scientists repeat the experiment and get similar results.
In earlier research, PCBs have been shown to cause a number of health
problems in animals, the EPA says, including cancer and problems with
the immune system, reproduction, nervous system and hormonal system.