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 Allan Felsot, an environmental toxicologist at WSU Tri-Cities,
questions the role of the common orchard pesticide methoxyclor as an
endocrine disruptor. "I've got 10 kids," he jokes. Seriously,
toxicological cause and effect are very difficult to determine.
While this process cannot guarantee that there won't be
unforeseen problems with a chemical in the future, it does offer
some protection. Unfortunately, no such process offers protection
from pharmaceuticals or naturally produced hormones that pass
through wastewater treatment facilities.
Richard Bull, professor of environmental science at WSU
Tri-Cities, has spent a large part of his scientific career
involved with various aspects of drinking water and water
treatment. Among his concerns is a worry that the focus on
pesticides may result in our not looking in other places that
contribute more important endocrine-active compounds-such as
wastewater. "In all probability, if there are environmental
impacts, these are the estrogens that are important," he says. And
there are a lot of them. They come from pharmaceuticals such as
birth control pills and from hormones secreted by pregnant women
and other animals. The metabolites of natural estrogens are likely
to remain in the water column, he says, while chemicals like
methoxychlor that are not highly water soluble are more likely to
become attached to sediments in the water and be removed during
drinking water treatment.
A second concern comes from the increasing dependence upon
municipal wastewater as a drinking water source that is being
contemplated in many parts of the country, including southern
California. A third is related to the effects of intensive
agriculture, an issue here in Washington. Intensive agriculture is
affecting the environment right now, and there may be human effects
down the line, he says. Effluents from feedlots contain
biologically active amounts of androgens that are released slowly
from androgen pellets attached to the ears of cattle to increase
growth. In dairy farms, there are high concentrations of natural
estrogens.
On the other hand, Bull is concerned that the focus on endocrine
disruption as a cause of reproductive problems will result in our
ignoring other explanations. If there has been a decline in human
male fertility as some suggest, there will be multiple causes, and
the focus on endocrine disrupters may bias research that is needed
to identify other causes, he says. He feels that the focus should
be on reproductive and developmental effects. "This broader
approach will catch the endocrine disrupters if they're
responsible," he says.
Kwan Hee Kim and Michael Skinner study the development of
the male reproductive system and the production of sperm in
rodents. Rodents protect themselves from toxins in much the same
way as humans do.
Kim's work deals with the effects of environmental chemicals on
the embryo during its development, but, as is the case for Verrell,
the effects she studies are not directly related to endocrine
disruption. They are, however, directly related to reproduction,
for she focuses on substances critical for sperm production:
vitamin A and the molecules it interacts with in specific cells
within the testis.
Kim's work has shown that vitamin A binds or attaches to a
specific molecule in some types of testis cells. The molecule, a
receptor, then moves into the cell's nucleus. Once there, it binds
to the DNA and leads to a change in the expression of genes and the
making of proteins.
Phthalates are known to be toxic to testicular cells, to be
endocrine disrupters, and to cause liver cancer. Kim is interested
in how they affect the interaction of vitamin A and its receptor.
She has found that phthalates interfere with the movement of the
receptor into the nucleus. If pregnant female rats are fed
phthalates for just five days during a specific time of embryonic
development, then the mature male offspring will have empty or
partly empty testes. Their sperm production will be limited, at
best.
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