Chemicals and Male Reproductive Health
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CHEMICALS LINKED TO DECLINING MALE REPRODUCTIVE HEALTH
A lengthy new report from the National Institute of Environmental
Health Sciences [NIEHS], a federal agency, describes serious
deterioration of the male reproductive system in many regions of
the world and suggests it may be caused by environmental
chemicals that interfere with hormones.[1] The report begins by
describing negative trends in men's reproductive health, then
describes similar findings among wildlife, and finally reviews
evidence that certain chemicals could cause the observed
problems. The report ends by describing a research agenda that
would help scientists understand these problems better and would
provide additional support for public health officials taking
action to protect future generations. Here is part of the summary
provided by the authors of the new study:
"Male reproductive health has deteriorated in many countries
during the last few decades. In the 1990s, declining semen
quality has been reported from Belgium, Denmark, France, and
Great Britain. The incidence of testicular cancer has increased
during the same time. Incidences of hypospadias [a birth defect
of the penis] and cryptorchidism [undescended testicles] also
appear to be increasing. Similar reproductive problems occur in
many wildlife species. There are marked geographic differences
in the prevalence of male reproductive disorders. While the
reasons for these differences are currently unknown, both
clinical and laboratory research suggest that the adverse changes
may be inter-related and have a common origin in fetal life or
childhood." The authors say they strongly suspect that the
common origin is exposure to environmental chemicals (pesticides,
plastics, detergents, and others) that interfere with hormones.
The authors emphasize that chemicals that interfere with hormones
may not be the ONLY cause of the recent decline in male
reproductive health. Other chemicals may poison men by a
mechanism that does not involve hormones: "For example," they
say, "some chemicals that are now known as occupational toxicants
were shown to affect the semen quality of the workers through a
toxic action on the gonads, without any apparent estrogenic
effects." Estrogen is the main female sex hormone. [For a
superb, clear, down-to-earth discussion of both male and female
reproductive health, see GENERATIONS AT RISK; HOW ENVIRONMENTAL
TOXINS MAY AFFECT REPRODUCTIVE HEALTH IN MASSACHUSETTS from
Greater Boston Physicians for Social Responsibility, which we
will review in the next few weeks. Anyone concerned about these
problems should own a copy of GENERATIONS AT RISK.[2]]
Sperm Quality
The authors review recent studies showing declining sperm
quantity and quality among men in many countries, and a few
studies that show no such declines. In general, they see
declines in urban areas and no declines in rural areas. Rural
France and Finland, in particular, seem not to be experiencing a
sperm decline. Still, the authors summarize the situation as
"decreasing sperm quality worldwide" (pg. 743) and they see an
urgent need for understanding the causes: "Follow-up of semen
quality is very important, since the sperm concentration has
decreased drastically during the last two generations and the
declining trend appears to be continuing." (pg. 760)
Testicular Cancer
Here, too, there are geographical differences. Increases in
testicular cancer are apparent in the U.S., England and Wales,
Scotland, the Nordic and Baltic countries, Australia, and New
Zealand. Finland seems to be an exception. The authors suggest
that good, steady sperm quality and the low testicular cancer
rate in Finland, a mostly rural country, may be somehow linked.
Within countries there are differences: whites in the U.S. are
three times as susceptible to testicular cancer as are African
Americans.
Conclusion: "...it is obvious that there is a worldwide trend
toward an increased incidence of testicular cancer...," the
authors of the report conclude. (pg. 743)
Conclusion: "Other disorders of the male reproductive tract may
also be increasing in incidence, with several European countries
reporting a progressive rise in hypospadias [a birth defect of
the penis]... and an apparently emerging trend toward an
increasing incidence of testicular maldescent [undescended
testicles]." (pg. 768)
Similarly, male reproductive problems can be observed among
wildlife. Gastropods (periwinkles and whelks), best known for the
sea shells they live inside, worldwide have shown sex reversal
because of exposure to a compound of the metal tin. Tributyltin,
widely used in paint to keep seaweed and barnacles from growing
on the bottoms of boats and ships, is now known to change male
gastropods into female gastropods. (pg. 748)
Alligators and turtles have had their sex lives disrupted by
exposure to pesticides in Florida and in laboratory experiments.
The sex of turtles is normally determined by the temperature at
which their eggs incubate. Eggs incubated at 26 degrees Celsius
(78.8 Fahrenheit) turn out 100% male. However, eggs incubated at
male-producing temperatures but painted with PCBs produce female
turtles instead. (pg. 749) PCBs are industrial chemicals, banned
in this country in 1976, but still found everywhere in the
environment. The same PCB-induced sex reversal can be seen in
alligator eggs. Furthermore, alligators in
pesticide-contaminated lakes in Florida have such small penises
that they are sexually incompetent --a result of exposure to
hormone-disrupting pesticides. (pg. 749)
Male fish exposed to hormone-disrupting chemicals discharged by
sewage treatment plants begin to produce a protein called
vitellogenin, which is normally only produced by female fish as a
step toward making eggs. Male fish normally produce no
vitellogenin but in England and Wales male fish produce
vitellogenin when they are caged in river waters below sewage
treatment plants. (pg. 750) The river water has become
estrogenic.
Florida panthers, which get a large dose of hormone-disrupting
chemicals by eating raccoons (who get these chemicals from the
fish they eat), have undescended testicles, poor sperm
production, and other reproductive problems. (pg. 751)
The NIEHS report then reviews the experience of male children
whose mothers were exposed to DES (diethylstilbestrol). DES is a
synthetic sex hormone. Between the late 1940s and the early
1970s, DES was given to 5 million pregnant women to prevent
abortion and pregnancy complications. The sons of these women
thus became a "natural experiment," offering an opportunity to
study the effects of human exposure to hormone-disrupting
chemicals while in the womb. Here is the authors' summary:
"Exposure to DES during pregnancy results in increased risk for
several male reproductive disorders, such as cryptorchidism
[undescended testicles], urethral abnormalities [including
hypospadias, pg. 753], epididymal cysts [cysts in the sperm
reservoir of the testicle], and testicular hypoplasia [lack of
growth of the testicles, i.e., small testicles]. In addition,
the semen quality of DES sons is worse than that of controls.
Incidence of testicular cancer is approximately doubled among DES
sons compared to the general population but whether this
represents a true increase of the cancer risk is equivocal [i.e.,
not certain]." (pg. 754)
In sum, the authors say, "Reproduction is a major concern because
disturbances of this process rapidly threaten populations as a
whole. The male reproductive system is very sensitive to the
influence of an excess of estrogen; therefore, estrogenlike
effects in the environment are a primary suspect for causing the
increased reproductive disorders of men and wildlife animals."
(pg. 760)
And: "Male reproductive health has received remarkably little
attention considering that subfertility affects 5% or more of men
and that prostatic hypertrophy [enlargement of the prostate
gland] or cancer is a major problem for older men. It is now
evident that several aspects of male reproductive health have
changed dramatically for the worse over the past 30 to 50 years.
The most fundamental change has been the striking decline in
sperm counts in the ejaculate of normal men; recent evidence from
Paris indicates that this decrease amounts to about 2% per year
over the last two decades. The result is that many otherwise
normal men now have sperm counts so low that their fertility is
likely to be impaired....
"These observations suggest that male reproductive health has
declined progressively since the Second World War as a result of
changes in environmental or lifestyle factors. While the
etiologies [causes] underlying these apparent changes are
currently unclear, both clinical [i.e., human] and laboratory
[i.e., animal] research suggests that all of the described
changes in male reproductive health appear interrelated and may
have a common origin in fetal life or childhood. This means that
the increase in some of the disorders seen today originated 20 to
40 years ago, and the prevalence of such defects in male babies
born today will not become manifest for another 20 to 40 years or
more.
"Trends in the reproductive health of species other than man also
raise the possibility of environmental factors as partial
etiologic [causal] contributions in a decline noted in male
reproductive health of wildlife." The report then mentions the
Florida panther, the male fish in England and Wales producing
vitellogenin, "fish-eating birds in the United States" whose
"male hatchlings were apparently feminized," and the male turtles
turning into female turtles because of PCB exposure of their eggs
in the laboratory. And: "A recent report of lactating male fruit
bats suggested that the males were, in some way, exposed to a
female sex hormone." In sum, "Taken together, this growing body
of evidence suggests that environmental factors that resemble
female sex hormones may be having an adverse effect on the
reproductive capacity and well being of diverse species...."
"The reproductive health trends in men are consistent with this
hypothesis. While exposure levels to estrogenic chemicals are
not at all well known for humans, the large number of chemicals
in numerous environmental categories suggests adequate
availability. For example, environmental chemicals reported to
be estrogenic include, but are not limited to, some ubiquitous
[i.e., found everywhere] chlorinated hydrocarbons, such as PCBs
and DDT; some products of detergent and surfactant manufacture,
such as the alkylphenols; and some products released from
plastics such as bisphenol-A and some phthalates. Many other
compounds in our natural and synthetic [human-created]
environment demonstrate estrogenic activities and more are being
discovered as the search continues." (pgs. 768-769)
--Peter Montague
(National Writers Union, UAW Local 1981/AFL-CIO)
[1] Jorma Toppari and others, "Male Reproductive Health and
Environmental Xenoestrogens," ENVIRONMENTAL HEALTH PERSPECTIVES
Vol. 104 SUPPLEMENT 4 (August 1996), pgs. 741-803. This new
report is a revised and abridged version of a report originally
commissioned by the Danish Environmental Protection Agency in
Copenhagen; see REHW #438.
[2] Ted Schettler, Gina Solomon, Paul Burns, and Maria Valenti,
GENERATIONS AT RISK: HOW ENVIRONMENTAL TOXINS MAY AFFECT
REPRODUCTIVE HEALTH IN MASSACHUSETTS (Cambridge, Massachusetts:
Greater Boston Physicians for Social Responsibility [11 Garden
Street, Cambridge, Mass. 02138; telephone (617) 497-7440; fax:
(617) 876-4277; E-mail: psrmabo@igc.apc.org], 1996). Available
for $11.50.
CORRECTION
In the electronic edition of RACHEL'S #513, we wrote: "One set of
nuclear long johns contained enough plutonium to provide one
trillion (one million million million) 'maximum permissible lung
burdens' of plutonium..." It should have said "...one trillion
(one million million)..."
Descriptor terms: niehs; male reproductive health; testicular
cancer; hormone disrupters; wildlife; sperm count; sperm quality;
hypospadias; cryptorchidism; undescended testicles; birth
defects; teratogens; pesticides; plastics; detergents; estrogen;
france; finland; gastropods; tributyltin; alligators; turtles;
pcbs; penis size; vitellogenin; florida panthers; des; prostate
cancer; children; alkylphenols; phthalates; bis-phenol-A; DDT;
organochlorines;
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--Peter Montague, Editor
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