The idea that xenoestrogens resulted in reduced sperm counts and
disorders of the male reproductive tract gained global prominence in
1992 when researchers at the University of Copenhagen published an
analysis of 61 sperm count studies from diverse locations covering
1938-1990 stating that sperm density had declined globally by more
than 40%. An article in the British journal Lancet soon followed
claiming that the apparent worldwide decline might be related to
exposure to compounds acting like estrogen and other endocrine
disrupters.
The sperm count claims have been an ongoing source of controversy.
While reports from some countries agreed that sperm counts had been in
decline for the past 20 to 25 years, studies and other locales have
shown no change in sperm counts over the same period. There appear to
be significant differences in sperm counts between regions, for
reasons which are presently unknown. However, some scientists posit
that xenoestrogens can hardly be to blame since the amounts of these
compounds in the global environment are similar and have even been in
decline in some areas.
A paper from Tulane University published in Science in June 1996
maintained that what were thought to be weakly estrogenic chemicals
were many times more active when mixed together than they were alone.
Additional reports maintained that pollutants were causing
reproductive problems in wildlife. Congress reacted to concerns by
enacting the Safe Drinking Water Act and the Food Quality Protection
Act in 1996 to develop guidelines for screening and testing endocrine
disrupters, including xenoestrogens.
Interestingly, attempts duplicate the Tulane paper in other
laboratories were unsuccessful, and the authors of the original paper
formally withdrew their paper in the July 25, 1997 issue of Science
because they were unable to obtain the same results from additional
tests.
A study by the National Research Council, an organization of the
National Academy of Sciences, was unable to find proof that synthetic
chemicals, including xenoestrogens, could act as human endocrine
disrupters. The National Research Council found the theory to be
"rife with uncertainties" and unsupported by existing experiments and
health records. Despite this finding, the EPA initiated a program to
test about 15,000 synthetic substances for endocrine-destructor
effects.
Even those strongly pushing the idea that xenoestrogens are
responsible for reduced male sperm counts acknowledge that there are
regional variations in sperm counts that are presently unexplained,
that endocrine disruption is at best one of many "plausible
explanations for the declines, and for the geographic variation." It
is acknowledged that human sperm density is something that is
difficult to measure an unbiased way. Furthermore, supporters state
that, "It is not likely that there is a single cause of low sperm
count. The process of sperm formation can be disrupted at multiple
points, some in the developmental formation of the glands and organs
essential for sperm production, some in altering hormonal sensitivity,
and some in the ongoing process in adulthood of spermatogenesis.
Different agents are likely to attack different parts of the chain of
events that leads to the production of healthy sperm. This reality
will confound all but the most sophisticated of epidemiological
studies. Taking cues from animal experiments will be essential." One
could argue this is a copout, stating that only those experimental
approaches delivering results that agree with us should be considered.
"The science of sperm count declines" Our Stolen Future
http://www.ourstolenfuture.org/NewScience/reproduction/sperm/sperm.htm
"In recent years, some scientists have proposed that chemicals might
inadvertently be disrupting the endocrine system of humans and
wildlife. A variety of chemicals have been found to disrupt the
endocrine systems of animals in laboratory studies, and compelling
evidence shows that endocrine systems of certain fish and wildlife
have been effected by chemical contaminants, resulting in
developmental and reproductive problems. However, the relationship of
human diseases of the endocrine system and exposure to environmental
contaminants is poorly understood and scientifically controversial."
The above quotation, along with information regarding the current
status of the EPA program can be found at: "Endocrine Disrupter
Screening Program" US Environmental Protection Agency February 8,
2004) http://www.epa.gov/scipoly/oscpendo/edspoverview/primer.htm#2.
According to the web site, the program is still trying to develop
valid methods to test to see if a substance has an endocrine
disrupting effect. In the absence of valid tests and conclusive
results, it would be difficult to substantiate the claims being made
that xenoestrogens are responsible for reduced sperm counts and male
reproductive tract problems. While the EPA testing program will
hopefully provide conclusive data, the process unfortunately does not
seem to be moving very rapidly towards producing useful data.
Sincerely,
Wonko
Additional Sources:
"Another Enviro-Scare Debunked" By Stephen Safe, Wall Street Journal (
August 20, 1997) http://www.junkscience.com/consumer/oct99/consumer_wsj0820.htm
"Another Phony Health Scare" by Gregg Easterbrook, Sacramento Be
(September 12, 1999)
http://www.junkscience.com/consumer/oct99/consumer_eas0912.htm
"Alternative Explanations for Phenomena Commonly Attributed to
Environmental Estrogens" by Noah Lewis (June 2000)
http://www.vegetus.org/other/endocrine.htm |
