Contact: Sarah Anderson
University of California - Los Angeles
Household chemicals may be linked to infertility
Researchers at the UCLA School of
Public Health have found the first evidence that perfluorinated
chemicals, or PFCs — chemicals that are widely used in everyday items
such as food packaging, pesticides, clothing, upholstery, carpets and
personal care products — may be associated with infertility in women.
Published online in
Europe's leading reproductive medicine journal, the study found that
women who had higher levels of perfluorooctanoate (PFOA) and
perfluorooctane sulfonate (PFOS) in their blood took longer to become
pregnant than women with lower levels.
The UCLA researchers
used data from the Danish National Birth Cohort to assess whether
levels of PFOS and PFOA in pregnant women's plasma were associated with
a longer time to pregnancy. A total of 1,240 women were included in
Blood samples were first taken between 4 and
14 weeks into the pregnancy so that concentrations of PFOS and PFOA
could be measured. The researchers also interviewed the women at around
the 12th week of pregnancy to find out whether the pregnancy was
planned or not and how long it took them to become pregnant.
Infertility was defined as a time to pregnancy of longer than 12 months
or a situation in which infertility treatments were used to establish
the pregnancy, and the results were adjusted for potential confounding
factors such as age, lifestyle and socioeconomic status.
level of PFOS in the women's plasma ranged from 6.4 nanograms per
milliliter (ng/ml) to 106.7 ng/ml, and from less than 1 ng/ml to 41.5
ng/ml for PFOA.
The researchers divided the women's levels
of PFOS/PFOA into four quartiles and found that, compared with women
with the lowest levels of exposure, the likelihood of infertility
increased by 70 to 134 percent for women in the higher three quartiles
of PFOS exposure and by 60 to 154 percent for women in the higher three
quartiles of PFOA exposure.
perfluorooctane sulfonate were considered to be biologically inactive,
but recently, animal studies have shown that these chemicals may have a
variety of toxic effects on the liver, immune system and developmental
and reproductive organs," said UCLA researcher Chunyuan Fei, the
study's first author. "Very few human studies have been done, but one
of our earlier studies showed that PFOA, although not PFOS, may impair
the growth of babies in the womb, and another two epidemiological
studies linked PFOA and PFOS to impaired fetal growth."
far as we know, this is the first study to assess the associations
between PFOA and PFOS levels in plasma with time to pregnancy in
humans," said principal investigator Jørn Olsen, chair of the
department of epidemiology at the UCLA School of Public Health. "We are
waiting for further studies to replicate our findings in order to
discover whether the chemicals should be added to the list of risk
factors for infertility."
In addition to being found in
household goods, PFCs, the class of chemicals to which PFOS and PFOA
belong, are used in manufacturing processes involving industrial
surfactants and emulsifiers. They persist in the environment and in the
body for decades.
The researchers believe that although they
measured the PFOS/PFOA levels after pregnancy was established, these
levels probably did not change significantly from the time before
pregnancy. Men's sperm quality could also be affected by PFCs and
might, therefore, contribute to the associations between PFC levels and
time to pregnancy, since couples would tend to be sharing the same
lifestyles and have similar exposures. However, the researchers did not
have data on PFC levels in fathers.
"Studies on sperm quality and PFOA/PFOS are certainly warranted," Olsen said.
researchers say the biological mechanisms by which exposure to PFOS and
PFOA might reduce fertility are unknown, but PFCs may interfere with
hormones that are involved in reproduction.
"Our data showed
that higher proportions of women reported irregular menstrual periods
in the upper three quartiles of PFOA and PFOS, compared with the
lowest, and so this could indicate a possible pathway," Fei said.
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