Common Herbicide Causes Sex Reversal in Frogs

From: Robina Suwol
Date: 30 Oct 2002
Time: 22:26:26
Remote Name:


New Study Finds Very Low Levels of Exposure to Common Herbicide Causes Sex Reversal, Hermaphroditism in Frogs

Date: 021024

Study Published Today in Environmental Health Perspectives Finds Impact of Atrazine Exposure the Same in Lab Field Tests E-Wire/Business Wire, Oct. 23, 2002 Research Triangle Park - A new study published today in the science journal Environmental Health Perspectives found that even very low- level exposure to atrazine, the most commonly used herbicide in the United States, altered reproductive organs in developing male leopard frogs. The study comes at a time when the effects of atrazine on environmental health are undergoing scientific review by the U.S. Environmental Protection Agency.

Today's study compared results for frogs exposed in the lab with those for some 800 frogs found in locations from Utah to the Iowa-Illinois border. Observations in both the lab frogs and the wild frogs were the same: exposure at concentrations as low as 0.1 part per billion (ppb) resulted in retarded gonadal development, the presence of female reproductive cells in male testes (hermaphroditism), and even complete sex reversal. This exposure concentration is 30 times lower than the current drinking water standard of 3 ppb. The study authors found that 36% of the males exposed to 0.1 ppb atrazine had underdeveloped testes. Further, 29% of the animals exposed at this level displayed varying degrees of sex reversal. Some males appeared to undergo complete sex reversal and had gonads almost completely filled with immature female egg cells.

At one field site, on the North Platte River in Wyoming, 92% of the males observed had testicular oocytes, and many of the animals showed advanced stages of complete sex reversal. There were no observable effects in atrazine- treated females. The study team was headed by Tyrone B. Hayes of the Laboratory for Integrative Studies in Amphibian Biology and the University of California-Berkeley. Other authors include Kelly Haston, Mable Tsui, Anhthu Hoang, Cathryn Haeffele, and Aaron Vonk. - - - EHP is the journal of the National Institute of Environmental Health Sciences, one of the National Institutes of Health in the U.S. Department of Health and Human Services.

More information is available online at

Editor's note: A full copy of the report is available by fax or email (PDF format) to working media at no charge.

Go to or contact using the phone number listed or email Source: Environmental Health Perspectives 10/23/2002 Contact: Brandon Adams, 919/541-5466/

Web Site: * * *

(c) 2002. All Rights Reserved.

Last changed: March 14, 2006