[Pharmwaste] Dude fish looks like a lady - but why?
dldebiasi at deq.virginia.gov
Wed Mar 4 12:21:44 EST 2009
Dude fish looks like a lady - but why?
Mystery widens as increasing number of male fish develop female traits
By Emily Sohn
updated 11:20 a.m. ET, Wed., March. 4, 2009
Around the world, increasing numbers of male fish are developing female
traits - growing new sexual organs and sometimes even producing eggs.
The phenomenon that has been blamed mostly on chemicals that get into
the water and mimic the female hormone estrogen.
But a new study puts some of the blame on an entirely different class of
chemicals - ones that block the action of male hormones called
It isn't the first study to suggest that anti-androgens might be
contributing to the feminization of fish. But the new research found
that there are far more of these chemicals in our lakes and streams than
anyone realized. And anti-androgenic chemicals in the water might affect
human health as well.
"They are going to be some potent players," said Charles Tyler, an
ecotoxicologist at the University of Exeter in England. "It is possible
that there are going to be many more chemicals that are anti-androgenic
than are estrogenic."
Tyler, along with Susan Jobling at Brunel University in London and other
colleagues, looked at chemical run-off in 51 rivers throughout the
United Kingdom. By combining concentrated water samples with cultures of
yeast genetically engineered to have androgen receptors, the scientists
were able to measure the amount of anti-androgen activity in each
The researchers' results, published in the journal Environmental Health
Perspectives, revealed a significant amount of anti-androgenic activity
in nearly all of the samples tested.
The researchers also collected fish from each site. With statistical
models, they were able to show that anti-androgens were just as
responsible for the feminization of fish as estrogenic compounds were -
if not more so.
"The amount of anti-androgen activity is pretty much a surprise," Tyler
said. "We expected some, but nowhere near the level of potency we
Anti-androgenic chemicals usually come originally from pesticides or
pharmaceuticals that get into wastewater. Dozens of studies have linked
these chemicals with health problems in mammals, said Gerald Ankley, an
ecotoxicologist with the Environmental Protection Agency in Duluth,
Minn. But this is one of the first studies to make the link in fish.
"This forms the basis for more focused experimental studies," Ankley
For example, scientists will need to figure out exactly which
anti-androgenic chemicals are causing problems in fish. (For his part,
Tyler says he is on the verge of announcing three new anti-androgenic
chemicals that will add to the list of more commonly known compounds).
Researchers also want to test whether certain mixtures of
hormone-disrupting compounds are more harmful than any one chemical
alone, Ankley added. And the work brings up plenty of questions about
what chemicals in our rivers and streams might be doing to human health.
After all, people and fish have similar hormonal systems.
"At the end of the day, wildlife are fantastic sentinels for potential
human impacts," Tyler said. "If it happens in fish, it can happen in
(c) 2009 Discovery Channel
Deborah L. DeBiasi
Email: dldebiasi at deq.virginia.gov
WEB site address: www.deq.virginia.gov
Virginia Department of Environmental Quality
Office of Water Permit Programs
Industrial Pretreatment/Toxics Management Program
PPCPs, EDCs, and Microconstituents
Mail: P.O. Box 1105, Richmond, VA 23218 (NEW!)
Location: 629 E. Main Street, Richmond, VA 23219
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