Endocrine-disrupting chemicals may be threatening
fertility in industrialized countries
The birth rate is declining in all industrialised
countries, and socioeconomic factors and women’s age are not solely to blame.
Male reproductive health and environmental factors are also significant, as
concluded in a new scientific review article. The article was recently
published in the American journal Physiological Reviews.
Behind the article are fertility researchers from
Denmark, the US and Finland. The researchers studied a number of factors
related to fertility, and one of the main conclusions of their study was that
poor semen quality contributed to increases in infertility and the use of
assisted reproductive technology.
The study also revealed higher incidence of testicular
cancer worldwide, with the greatest frequency among Caucasian populations.
Moreover, the researchers also observed lower levels of testosterone in average
men. “I was surprised that we found such poor semen quality among young
men aged 20 to 25. The average man had up to 90% of abnormal sperm. Normally,
there would be so many sperms that a few abnormal ones would not affect
fertility. However, it appears that we are at a tipping point in industrialised
countries where poor semen quality is so widespread that we must suspect that
it results in low pregnancy rates,” said first author of the article,
Professor Niels E. Skakkebaek from the Department of Growth and Reproduction
(EDMaRC) at Rigshospitalet and the University of Copenhagen.
“The article also demonstrates the impact of the
increasing number of male reproductive problems on low birth rates. There is no
doubt that environmental factors are playing a role. These are the correlations
we are researching at the new research centre EDMaRC at Rigshospitalet,”
added Professor Anders Juul, who is the last author of the article.
Many of the male reproductive problems could be due to
damage to the testes during embryonic development. While the reproductive problems
could arise from genetic changes, “recent evidence suggests that most
often they are related to environmental exposures of the fetal testes,”
the researcher team wrote.
“Since the disorders in male genitals have increased
over a relatively short period of time, genetics alone cannot explain this
development. There is no doubt that environmental factors are playing a role
and that endocrine-disrupting chemicals, which have the same effect on animals,
are under great suspicion. The exposure that young people are subjected to
today can determine not only their own, but also their children’s, ability to
procreate,” explained Professor Skakkebaek.
According to Professor Skakkebaek, the study has
significant public health implications. “Governments in industrialised
countries seem much more interested in the current economic aspects of low
birth rates and do not see the writing on the wall for the long-term
environmental effects on our population’s ability to reproduce. Moreover, there
is much focus on the age of delivering women as the only biological factor
behind the low birth rates. However, the situation is more complex. Age does
indeed play a role. However, we found in our analysis that the average age of a
delivering woman in Denmark in 1901 was the same as today, suggesting that
delayed childbearing alone cannot explain the current trends.”
More research in reproductive medicine needs to be done
to understand and address the declining fertility rates. “If socioeconomic
factors alone were behind the current declining figures, they could be reversed
by political measures. On the other hand, if our populations have become less
fertile or more people have even become infertile, our societies are facing
much more serious problems. Only biomedical research can identify and solve the
problems,” concludes Professor Juul.
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