Science Matters: Human hormones mess with male fish

[Guest guest]

Here's your weekly Science Matters column by David Suzuki with Faisal Moola.

Human hormones mess with male fish

<HTMLCOPY>Most people alive today were born after 1950. To these people, our

modern world is just the way things have always been. Imagining life without

TV, radio, telephones and the Internet is next to impossible. Teenagers

probably have a hard time imagining life without text me

And it's true, human reach is now profound. We are the most integrated,

interconnected and mobile species that has ever existed on this planet. Some of

these interconnections produce marvelous results. We get to know other

cultures. We understand more about history and each other. We can easily chat

with

friends and family on the other side of the world.

But we have to remember that, although we are connected with each other more

than ever, we are also intimately connected to the rest of the natural world.

These connections can manifest themselves physically, such as through global

warming. But they can also manifest themselves biologically - and in some

surprising ways.

Recently, researchers writing in the U.S. journal Proceedings of the

National Academy of Scientists reported that male fish became " feminized " when

exposed to human hormones. Some of the fish, a type of fathead minnow, produced

early-stage eggs in their testes while others actually developed tissues for

both reproductive organs.

How would fish be exposed to female human hormones? Through treated or

untreated municipal wastewater, of course. It seems that widespread use of birth

control pills has elevated the amount of estrogenic substances going into our

waste stream. Remember, things that go down our toilets don't just disappear.

They can actually survive simple sewage treatment processes and end up in our

rivers, lakes and oceans.

Reports of fish feminization due to human female hormones are today fairly

well documented - but long-term studies of what impact this can have on fish

populations have not been done. For this latest study, researchers actually

added the synthetic estrogen found in contraceptive pills to a remote lake in

northern Ontario in amounts that are normally found in human wastewater. They

did this for three years, and monitored the results over a period of seven

years.

The results were startling. As expected, the male fish developed some

feminized characteristics, such as producing proteins normally synthesized in

females. But what really disturbed the scientists was how populations of the

fish

crashed to near extinction levels by the end of the experiment. Feminization

of the males combined with hormonal changes to the females apparently damaged

their overall reproductive capacity to the point that the fish were unable

to maintain their population.

Conclude the researchers: " The results from this whole-lake experiment

demonstrate that continued inputs of natural and synthetic estrogens and

estrogen

mimics to the aquatic environment in municipal wastewaters could decrease the

reproductive success and sustainability of fish populations. "

This spells trouble. Most Canadians have probably never heard of the fathead

minnow, but these fish are a vital food source for well-known and popular

sport fish that people have heard of - such as walleye, lake trout and northern

pike. They are also well-studied and often used in toxicology testing because

they have short life cycles, adapt well to lab conditions and are

representative of a large family of fish. The report authors describe the

fathead

minnow as " a freshwater equivalent of the miner's canary. " In other words, what

happens to the fish, as with the bird, could happen to humans in short order

unless we are very careful. Cell phones and the Internet aren't our only

connections with each other and with the world. We are biological creatures too

and

we have to remember that these are the connections that ultimately matter

the most.

Take the Nature Challenge and learn more at _www.davidsuzuki.org_

(http://www.davidsuzuki.org/) .

 

 

 

 

 

 

 

[Guest guest]

I think this is a very good article, and has been proven over time, BUT, I

disagree with the statement about most people being born after 1950!! I was

born in the 40s, and I even know a lot of people who are older than me.

The " grey army " are quite numerous. Maggie