Weed killer causes male frogs to lay eggs

CBC News

March 2, 2010

Australian Broadcasting Corporation

One of the most common weed killers in the world, atrazine, can chemically castrate male frogs, turning them into females that lay eggs, say U.S. researchers.

Atrazine continues to be used on cornfields in Canada, although it is no longer approved for use in Europe. The U.S. Environmental Protection Agency announced last year it would launch a new scientific evaluation of atrazine’s effect on humans.

The gender change occurred at a concentration of atrazine half of the Health Canada guideline for drinking water.

Prof. Tyrone Hayes of the University of California, Berkeley, and colleagues reported their findings in this week’s Proceedings of the National Academy of Sciences.

“Atrazine-exposed males were both demasculinized [chemically castrated] and completely feminized as adults,” said Hayes.

Atrazine is widely used by farmers around the world as a herbicide, particularly in production of corn, sorghum and sugar cane.

Earlier studies have found that the chemical feminized zebra fish and leopard frogs, and caused a significant decline in sperm production in male salmon and caiman lizards.

“Atrazine exposure is highly correlated with low sperm count, poor semen quality and impaired fertility in humans,” said Hayes and colleagues.

While previous studies have shown atrazine adversely affects amphibian larval development, this latest study of African clawed frogs shows the process can go even further, said Hayes.

“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,” said Hayes.

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Author: Leslie Carol Botha

Author, publisher, radio talk show host and internationally recognized expert on women's hormone cycles. Social/political activist on Gardasil the HPV vaccine for adolescent girls. Co-author of "Understanding Your Mood, Mind and Hormone Cycle." Honorary advisory board member for the Foundation for the Study of Cycles and member of the Society for Menstrual Cycle Research.