[Pharmwaste] Estrogen threatens minnow manhood
Laurie.Tenace at dep.state.fl.us
Tue May 22 13:23:05 EDT 2007
Estrogen threatens minnow manhood
Released into an Ontario lake as an experiment, tiny amounts of the hormone
wreak havoc on male fish
May 22, 2007
Back in the summer of 2001, a team of Canadian and U.S. researchers spiked a
lake in Northwestern Ontario with traces of synthetic estrogen used in human
birth control pills. They then repeated the unusual treatment for the next
two years and sat back and watched what happened to minnows living in the
The results were nothing short of frightening. Exposing fish to tiny doses of
the active ingredient in the pill, amounts little more than a whiff of
estrogen, started turning male fish into females. Instead of sperm, they
started developing eggs. Instead of looking like males, they became
indistinguishable from females. Within a year of exposure, the minnow
population began to crash. Within a few years, the fish, which at one time
teemed in the lake, had practically vanished.
Details of the unusual experiment, conducted by a team of Canadian and U.S.
government scientists, are being published online this week in the
Proceedings of the National Academy of Sciences. The dramatic results are
likely to raise further concerns about the possible impact on wildlife and
humans of drug residues in waterways.
In the experiment, the scientists added just enough estrogen to give the lake
water the same level of the sex hormone found in water discharged from sewage
treatment plants in Canada and in other countries where the birth control
pill is widely used.
More than a million women in Canada and more than 100 million worldwide are
on the pill, making it one of the most commonly prescribed drugs. Women on
the pill pass on some of the estrogen in their urine, from which it gets into
Although the doses in the lake's water were thousands of times lower than the
amounts women on the pill receive, even this slight exposure was enough to
skew development in both male and female fish, with males far more affected.
After treatment, the lake water had estrogen concentrations of about 5 parts
per trillion, the scientific equivalent of almost nothing. A part per
trillion is the equivalent of a few grains of salt in an Olympic-size
swimming pool. The amount of estrogen added was about a fifth of a gram a
day, or about one-tenth the weight of a penny.
The lead researcher, Karen Kidd, who conducted the project while with the
Department of Fisheries and Oceans and is now a biologist at the University
of New Brunswick, was astonished that so little of a hormone used by people
could harm fish.
"What's sobering for me is that we've shown such a dramatic response in fish
population at these low concentrations," Dr. Kidd said in an interview.
It's not known what effect, if any, human exposure to estrogen in drinking
water might have, although Dr. Kidd said it is an area that should be a
research priority. Reproductive problems in human males, such as declining
sperm counts and testicular cancer, have been rising in recent decades, and
the causes are not known.
"When we see these kinds of responses in fish, it raises a red flag for what
these compounds are doing to humans," she said.
There are currently no regulations in Canada covering estrogen or other drug
residues in waterways. Municipalities typically don't check for them and it
is not known if there are human health effects for people who draw drinking
water from sources receiving sewage, a common practice in Canada.
Researchers with the U.S. Environmental Protection Agency also worked on the
experiment, which was funded primarily by the federal government and the
American Chemistry Council. One of the companies that manufactures birth
control pills, Schering AG, donated the estrogen.
The researchers monitored fathead minnows, a species that breeds after about
two years of life, making its population vulnerable to the reproductive
effects of the drug sooner than longer-living fish.
After dosing the lake for three years, researchers monitored populations for
the next two. It is expected that with time, estrogen levels in the lake,
which was about 35 hectares, or about the size of a large farm field or a
medium-sized cottage-country lake, will decline, allowing fish populations to
To ensure that the population decline they were observing wasn't a natural
phenomenon, the researchers tracked several other water bodies similar to the
lake under investigation. There were no large population fluctuations
elsewhere. The lake was located near Kenora.
Over the past decade, there have been a number of studies in North America
and Europe showing skewed sexual development in aquatic life living near
outfalls from sewage plants. This study is the first to show that exposure to
drugs not only changes sexual characteristics, but can also destroy fish
Dr. Kidd doesn't think women should stop taking the pill out of worry for
wildlife. She said municipalities need to build more advanced sewage
treatment plants, which are able to degrade more of the estrogen into
Because of the high expense of the project, estimated at $250,000 a year, the
researchers didn't test the effects of lower estrogen levels on fish to
determine if there is a safe exposure amount.
Laurie J. Tenace
Florida Department of Environmental Protection
2600 Blair Stone Road, MS 4555
Tallahassee, Florida 32399-2400
PH: (850) 245-8759
FAX: (850) 245-8811
Laurie.Tenace at dep.state.fl.us
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