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Texas, is one of the first to show that men's chemical exposures may be
more important than women's in determining fertility issues. For men,
links were found between 12 chemicals and longer time to pregnancy,
while for women, it was five chemicals. PCBs, organophosphate
pesticides and perfluorinated compounds were associated with this effect,
which could be a sign of fertility problems.
POPs have been associated with altered menstrual cycles, reduced
ovulation, pregnancy loss and reduced follicle count, which is indicative
of reduced egg supply (Nicolopoulou-Stamati and Pitsos 2001). More
specifically, exposure to PFC stain repellents, PBDE flame retardants and
the industrial chemicals PCBs were associated with a longer time to
pregnancy in women.
However, most of these studies measured chemical exposures during
pregnancy, which, by nature, exclude women who are unable to become
pregnant.
Time to pregnancy is a sensitive measure of fertility and reproductive
success and is a calculation of the number of menstrual cycles it takes for
a couple to achieve a pregnancy. Most studies assessing male fertility have
not used this measure and instead rely on semen quality and hormone
levels that are only correlated to fecundity and cannot accurately measure
the time to a successful pregnancy. A longer time to pregnancy can suggest
sub-fertility problems (if longer than six months of trying) or infertility (if
longer than 12 months).
Over the past few decades fertility rates, as indicated by declining
male semen quality, are decreasing. Many scientists believe early exposure
to estrogen-like chemicals is contributing to fertility decline, while others
believe that lifestyle changes over the same period may have a stronger
contribution.
What did they do?
Between 2005 and 2007 researchers recruited 501 couples from
Michigan and Texas who were trying to conceive. The couples were
followed until they became pregnant or for up to 12 months of trying,
which is clinically defined as infertility. The participants were in their 20s