UPDATE 1-Common weedkiller turns male frogs into females

Mon Mar 1, 2010 8:22pm EST

* Male frogs completely feminized

* Study helps explain decline of frogs

* Levels were below EPA standards (Adds Syngenta comments, paragraphs 7-9)

By Maggie Fox, Health and Science Editor

WASHINGTON, March 1 (Reuters) - Atrazine, one of the most commonly used and controversial weedkillers, can turn male frogs into females, researchers reported on Monday.

The experiment is the first to show such complete effects of atrazine, which had been known to disrupt hormones and which is one of the chief suspects in the decline of amphibians such as frogs around the world.

"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 chemical had been shown to disrupt development and make frogs develop both male and female features -- termed hermaphroditism. This study of 40 male frogs shows the process can go even further, Hayes said.

"Before, we knew we got fewer males than we should have, and we got hermaphrodites. Now, we have clearly shown that many of these animals are sex-reversed males," Hayes said in a statement.

"Atrazine has caused a hormonal imbalance that has made them develop into the wrong sex, in terms of their genetic constitution."

Syngenta AG (SYNN.VX), one of several companies that makes atrazine, questioned the design of the study and said Hayes has a history of offering flawed studies for publication.

"For 50 years, atrazine has been used safely in agriculture with no effect to amphibians, fish, birds and other wildlife at concentrations found in the environment -- a fact that is supported by numerous scientific studies," the company said in a statement.

The Proceedings is a peer-reviewed journal, meaning that papers it publishes have been screened for obvious flaws.


Whether the effects translate to humans is far from clear. Frogs have thin skin that can absorb chemicals easily and they literally bathe in the polluted water.

The European Union banned atrazine in 2004. The finding may add pressure to the United States to more closely regulate the chemical, used widely in agriculture.

"Approximately 80 million pounds (36,000 tonnes) are applied annually in the United States alone, and atrazine is the most common pesticide contaminant of ground and surface water," the researchers wrote.

"In fact, more than a half million pounds (220 tonnes) of atrazine are precipitated in rainfall each year in the United States."

The U.S. Environmental Protection Agency said in October it was reviewing the health impacts of atrazine.

Hayes and colleagues studied 40 African clawed frogs, keeping them in water contaminated with 2.5 ppb (parts per billion) of atrazine. The EPA's current drinking water standard is 3 ppb.

"Ten percent of the exposed genetic males developed into functional females that copulated with unexposed males and produced viable eggs," the researchers wrote.

"Regardless of the mechanism, the impacts of atrazine on amphibians and on wildlife in general are potentially devastating," they wrote.

"The negative impacts on wild amphibians is especially concerning given that the dose examined here (2.5 ppb) is in the range that animals experience year-round in areas where atrazine is used as well within levels found in rainfall, in which levels can exceed 100 ppb in the Midwestern United States," they added.

(Editing by Sandra Maler)

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Comments (4)
I find it troubling that when these results are seen in frogs we call them negative and concerning but when they happen in humans we hand them a rainbow flag tell them to march in parades and be proud of who they really are!

Mar 01, 2010 11:21pm EST  --  Report as abuse
KurtTappe wrote:
I find it troubling that “WhatRWeThinking” confuses negativity about chemical contamination with human behavior. He even grammatically-confuses “them” as in test results with “them” as in gay humans. Bizarre. But most troubling is that these tests prove that sexual orientation in frogs is not chosen and thereby strongly indicates that sexual orientation in humans is not chosen. So sorry, “WhatRWeThinking”; we are left to wonder why you think gay humans choose their lifestyle when evidence such as this demonstrate otherwise.

Mar 01, 2010 11:42pm EST  --  Report as abuse
turbey wrote:
I suppose that is supposed to be a witticism, which is unfortunate because it makes little sense. In your statement you seem to be positing that a) the frogs have developed some sort of chemically induced homosexual tendencies in addition to the chemically-caused hermaphroditism and b) all participants of gay parades are also hermaphrodites. Don’t worry, you have left room for explanation: given b, do you additionally suggest that the participants in gay parades have also been subjected to some sort of treatment that forced an unnatural (read: chemically based) state of hermaphroditism, similar to the situation exhibited by the amphibians? Are you familiar with the scientific and common English definitions of “hermaphrodite” and “homosexual”? Are you sorry that you accidentally assumed the frogs are also now gay, but whoaaaa it’s all cool now because really you were just super pumped up to start the new gay pride frog movement?! (Because hey, if those humans have them…equal opportunities for amphibians!)

I don’t know: I always prefer my humor and sarcasm rooted in something other than complete ignorance — it makes it a lot more “laugh with them” and a lot less “laugh AT them”.

Mar 01, 2010 11:47pm EST  --  Report as abuse
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