Contraceptive chemical runoff causes sex changes in frogs, study finds

The hormones found in female contraception pills often male their way into the environment, and those hormones are wreaking havoc on amphibians, according to a new study in the journal Scientific Reports.

The study looked at the effects of estrogen ethinylestradiol (EE2) in three amphibians and found significant evidence they affect the hormonal systems and sexual development in these animals.

Contraceptives harming the environment

EE2 is a man-made estrogen, a commonly used active component of female contraceptive pills that does not appear in nature. It is only partially removed in sewage plants, and it can get to water bodies in biologically-important levels, the study team noted in a press release.

“Amphibians are almost permanently exposed to such threats,” said study author Matthias Stöck, an amphibian researcher at the IGB research institute in Berlin. “Only, if we will be able to actually access these risks, we will be able to eliminate them in the long term.”

The researchers noted that sensitivity towards hormonally active substances, like EE2, is not the same in all amphibians, studies have found. Some species have undergone quite a few hundred million years of independent evolutionary history and have developed various mechanisms of genetic sex determination.

In the new study, researchers tested the impact of EE2 on the development of three amphibian species: the African clawed frog, tadpoles of the European tree frog, and the European green toad. All three were raised in water that contained various levels of EE2 and their development was compared to control groups.

Researchers established the genetic sex of all species using most recent molecular approaches.The scientists also studied the phenotypic progression of the sexual organs.

The study tram found a sex reversal occurred from 15 to 100 percent of the time in the animals exposed to EE2.

“In addition to other threats, the feminization of populations may contribute to the extinction of amphibian species,” Stöck said.

“EE2 is also part of our water supply and, together with other estrogen-like substances, it presents a serious risk not only for amphibians but also for humans. Our study shows that the clawed frog as model species is well-suited to study the effects of hormonally active substances in the environment,” added study author Werner Kloas, an eco-toxicologist from IGB. “The effect established in this species, however, cannot be extrapolated to other amphibian species without caution.”

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Image credit: Thinkstock

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