There is some emerging data that has identified an effect of atrazine in wildlife that may be linked to hormone disruption. A study from the University of California at Berkeley has shown that atrazine can affect the sexual development of African clawed frogs.

The male tadpoles were exposed to a wide range of atrazine levels from very low to high. All of the atrazine-exposed tadpoles had abnormal sexual development.

There were no abnormalities in the control frogs that were not exposed to atrazine.

In the atrazine-exposed male frogs, up to 20% had both testes, the male sex organ, and ovaries, the female sex organ. These frogs are called “inter-sex” or hermaphrodite frogs.

Also, the male frogs were more like female frogs. Atrazine had a demasculinizing effect on the male frogs.

Female frogs were not affected.

These effects occurred at very low levels of atrazine, levels commonly seen in lakes, rivers and streams in agricultural areas where atrazine is used for crop protection.

The effects were seen as low as 0.1 part per billion. This is 30 times lower than the maximum level for atrazine allowed by the Environmental Protection Agency in public drinking water supplies, which is 3.0 parts per billion.

The researchers also measured levels of sex hormones in adult frogs. They found that adult male frogs that had been exposed to atrazine had very low levels of the male hormone testosterone.