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Widely Used Weedkiller Turns Male Frogs Into Females

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Widely Used Weedkiller Turns Male Frogs Into Females

Atrazine, one of the most widely-used weedkillers, can turn male frogs into females, researchers reported on Monday. “Atrazine-exposed males were both demasculinized (chemically castrated) and completely feminized as adults,” Tyrone Hayes of the University of California Berkeley and colleagues wrote in the Proceedings of the National Academy of Sciences. The atrazine can turn male frogs into females that are able to mate and successfully reproduce.

Previously the chemical had been shown to disrupt development and create hermaphroditism in frogs, whereby they develop both male and female features. This latest study of 40 male frogs shows the process can go even further, Hayes said. “Atrazine has caused a hormonal imbalance that has made them develop into the wrong sex, in terms of their genetic constitution.”

Although banned in the European Union in 2004, atrazine is still one of the most commonly used herbicides across the globe. Its endocrine disruptor effects, possible carcinogenic effect, and epidemiological connection to low sperm levels in men has led several researchers to call for banning it in the US. Like many herbicides, it is sold under numerous trade names (see next page).

“Approximately 80 million pounds are applied annually in the United States alone, and atrazine is the most common pesticide contaminant of ground and surface water,” the researchers wrote. It can be transported more than 621 miles from the point of application via rainfall and, as a result, contaminates otherwise pristine habitats, even in remote areas where it is not used.

I’m not all that surprised to hear that Syngenta AG, one of several companies that makes atrazine, has long defended its safety. The company says it is one of the best-studied herbicides available and pointed to prior safety reviews from the EPA and World Health Organization, among others.

Next: Trade names for atrazine

Photo: Tyrone B. Hayes, the University of California, Berkeley

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Melissa Breyer

Melissa Breyer is a writer and editor with a background in sustainable living, specializing in food, science and design. She is the co-author of True Food (National Geographic) and has edited and written for regional and international books and periodicals, including The New York Times Magazine. Melissa lives in Brooklyn, NY.


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1:37PM PST on Dec 5, 2011

I always tell my students to get acquainted with allelopathy ( see my previous comments of 2010). Plant extracts will be the future to replace pesticides. I am conducting some short experiments to compare the efficacy of herbicides and Eucalyptus leaf extracts.I encourage Weed Scientists to shift their interests to allelopathy. Natural compounds ( plant- made chemicals) are friends to the environment and are bad enemies to pests.

1:24PM PST on Dec 5, 2011

Yes Loesje, you can go back to nature, and use organic agriculture to produce your apples and potatoes.The problem is organic agric. is very limited, and thanks for the chemicals, which are produced by the wise guys. We know for sure we "pump" hundreds of thousands of pesticides to kill pests, which include rats, roaches, and weeds, but not "frogies"!! Well, herbicides ( atrazine is one of them) are useful when applied carefully.Weeds are controlled by atrazine and others to harvest high yield of wheat, onions, eggplants, and cherry, and some other goodies, which we would like to see in our birthday cakes.Should we put the blame on atrazine, or should it be on our "eager" farmers? When we spray atrazine, we have to be sure that this chemical does not contaminate the wilderness. Unfortunately, some farmers, however, may " play a rough game" and the redult is the escape of few drops of atrazine from the sprayed area to the neighbors territory, which happen to be a territory of male frogies.

1:23AM PST on Dec 1, 2011

Can we live without chemicals or pesticides? If the ground and water are being contaminant and the atrazine can turn male frogs into females and how about for the humans?
This is weird and please go back to the nature.

6:20AM PDT on Oct 11, 2011

Thanks for the article.

12:34PM PDT on Jun 2, 2011

thanks, we have to question the amount of fertilizer we use

4:07AM PDT on Apr 24, 2011

Wow, if this chemical changes male frogs into female frogs, does it mean we might have a shortage of baby frogs?

5:51PM PST on Jan 29, 2011

Thanks for the article. Very interesting!

7:13AM PDT on Jul 25, 2010

How bad is our judgment against atrazine? As agriculturists, we love atrazine for its high efficacy against weeds in corn fields and some other crops. Then again, we love and perhaps adore fogys, whether they were males of females. They provide colorful life around the ponds and streams of fresh water. They also make a pleasant "crocking" !!!! Nevertheless, let us stop for a minute and think scientifically. Does really sex transformation occur whenever a male frog gets exposed to atrazine? To answer this question, one should change his career and his profession and become a toxicologist. Well, I am not a toxi, but sure like to conduct an experiment with good statistical lay out using 1000 male frogs as experimental units and dose them with different conc. of atrazine. Watch and score the results. What is the probability of converting all males or half of them to females. I also like to set up the same test on females. They may turn out males ( reversed mechanism ) !! If this would happen, then we are in a state of equilibrium!!!!!!!.

5:40AM PDT on Jul 3, 2010

Most interesting and almost seems to be unbelievable! Will have to do more of my own reading on this......thank you!

10:17AM PDT on Jun 16, 2010

continue...Experiments, such as the effect of a certain pesticide on the respiratory and genital systems of Euglena! And reproduction of animals and DNA conformation and its nucleotide composition; and cell structure and elongation of some growing parts of a louse for example. We can go on and dictate so many interesting researches to be run by pesticide people. Or should we just focus on all kinds of experimentation related to sexual make up of frogys. Well, frogys are not humans, so let us think of diverting research on gals and guys and see how atrazine will function in our genital system.
Basic producers may have some comments on this, and they may say this is weird! Well , its; but can a producer of atrazine tell us how the hick an innocent frogy becomes a victim of your lousy atrazine and loses its male chauvinism and turn into a good looking female frogy ? AGAIN, WAKE EPA.

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people are talking

Thanks for sharing. I happen to have all the necessary ingredients so will try this later on today.

Sorry, I find it very superficial and incomplete.

Thank you for the article.


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