03/08/2005 - Scientific
research is increasingly suggesting that man-made
chemicals might be partly responsible for
the rising incidence of fertility problems
in European men, including dropping sperm
counts, feminisation of male babies, and sperm
that 'burn out' before reaching their target
(i.e. the egg).
Recent statistics show that 40% of young
men in Denmark and one in five men in the
United Kingdom have such low sperm counts
that they may not be able to father children.
In the United Kingdom, this is now one of
the biggest causes of infertility among couples.
This worrying trend was first publicised
in 1991 by Danish scientist Niels Skakkebaek
of the University of Copenhagen. He showed
that the sperm counts of Western men had dropped
by about half over the previous 50 years.
This research was then corroborated in 2000
by a study by a Danish research team led by
AG Andersen showing that from a sample of
18-20 year-old Danish men, 40% of them had
sperm counts below 40 million per ml, a level
associated with male infertility.
The figures on British men’s failing fertility
were released at the European Society of Human
Reproduction and Embryology (ESHRE) in Copenhagen
at the end of June. The UK’s Human Fertilisation
and Embryology Authority (HGEA) data says
that men are now beginning to overtake women
as the cause of infertility in relationships.
Clare Brown, of Infertility Network said that
"people are genuinely surprised to find
out that (infertility) is pretty much 50-50".
Because of the growth of British male infertility,
there has been a huge rise in the fertility
treatment used to deal with low sperm counts
– ICSI-, a process which involves injecting
a single sperm across the membrane of an egg
to make a fertilise embryo, which is then
implanted into the women, In 2002 it accounted
for 52% of all fertility procedures, and across
Europe, more than 122,000 ICSIs were performed
in 2004.
Phthalates to blame?
So what is to blame for these effects on
male fertility? There are many possible factors.
Making any definitive link to a single cause
is very difficult, but recent research points
to the possibility that phthalates, a group
of chemicals with a range of applications
(from softening plastic to use in cosmetics)
may be involved.
A new study led by Shanna Swan at the University
of Rochester, New York, showed that mothers
with higher levels of phthalate metabolites
in their urine (a measure of prenatal exposure
to phthalates) were more likely to produce
feminised sons. The researchers also found
that the exposure levels at which effects
were seen were "not unusually high".
According to Professor Richard Sharpe of
the Human Reproductive Sciences Unit in Edinburgh,
a leading male fertility specialist, "this
suggests phthalates may be having an effect
in humans at lower levels than rats. If true,
there would be a widespread health risk to
unborn boys.
" Indeed, the effects of phthalate exposure
in rats are to a certain extent similar to
those seen in the male babies in Swan's work,
which could suggest that phthalates might
be responsible for increasing incidence of
male abnormalities and consequently, testicular
cancer and problems with sperm quality.
Moreover, Professor Sharpe’s own research
has shown that phthalates can have an effect
when pregnant mothers are exposed to them
at a key stage in the development of their
unborn children. "Phthalates are everywhere
in our environment, we are all exposed",
he says, "and the highest exposure appears
to be in young women of reproductive age."
(due to the use of phthalates in cosmetics
and perfumes).
Chemicals in food causes human sperm to ‘burn
out’
As well as the feminisation of baby boys,
chemicals are also affecting male fertility.
In June this year Professor Lynn Fraser of
King’s College, London, showed that chemicals
found in food and industrial products were
capable of damaging human sperm.
She found that even small quantities of the
chemical genistein (found in soya and legumes)
when combined with other chemicals could cause
human sperm to 'burn out' prematurely, making
them incapable of fertilising an egg.
Professor Fraser made this discovery when
she was researching into the ways in which
combinations of certain chemicals could become
very potent endocrine disruptors. She and
her team tested combinations of three chemicals:
genistein, 8-prenylnaringenin (found in hops)
and nonylphenol, (used in paints, herbicides,
pesticides, cleaning products and the production
of paper and textiles).
Her team found that combinations of small
quantities of these three chemicals stimulated
sperm to undergo a reaction that made them
infertile, to a far greater extent than when
used individually. Commenting on the findings,
Professor Fraser said, "At a time when
there are concerns that the incidence of infertility
may be rising, this research flags up important
warning signs".
Dr Anders Nyboe-Andersen, ESHRE Committee
coordinator, also expressed concern about
the relevance of the findings for male infertility,
considering that "maybe environmental
factors are playing an increasing role as
the planet becomes more polluted and factors
that disrupt the endocrine system are in the
food chain".
Concerns surrounding the possible environmental
causes of European men’s increasing infertility,
clearly demonstrate the importance of evaluating
all chemicals currently in use and their potential
endocrine disrupting properties. It is therefore
vital that the proposed EU chemicals legislation,
REACH, deals effectively with suspected endocrine
disrupting chemicals. The health and fertility
of future generations of wildlife and humans
depend on it.
