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Your Birth Control Pill Pee Is Making Male Fish Grow Ovaries

A new study from the US Geological Survey published in Scientific Reports has found that fish all over the US are showing signs of exposure to EE2—a synthetic hormone found in oral contraceptives.
Photo via Flickr user DCNature

Birth control pills are amazing—primarily because they do their job so well. Use them correctly, and you've got about a 99 percent chance of staying baby-free. But because they're so effective, their powers continue—albeit in a diluted form—even after you pee them out and flush them down the toilet.

And that's how they have been making their way into the fish population.

A new study from the US Geological Survey published in Scientific Reports has found that fish all over the US are showing signs of exposure to 17a-ethinylestradiol—aka EE2—a synthetic hormone found in oral contraceptives. And needless to say, they don't have a prescription. Favorite fryin' fish like smallmouth and largemouth bass have been found to be affected by the habits of pill-popping ladies, whose urine (and unused pills) gets flushed into waterways all across the US.


As a result, exposed fish have increased difficulty reproducing, and even their offspring experience reduced fertility levels. In fact, grandchildren of fish who ingest EE2 have 30 percent lower levels of fertilization than their "clean" counterparts. And there's a lot of BC floating around out there: Up to 68 percent of a dose of EE2 makes its way into human waste, with a full dose surviving when whole pills are flushed. According to the study in Scientific Reports, the synthetic hormone endures even after wastewater has been treated.

But leaving behind a healthy lineage of grandchildren is the least of the worries of some of the unwittingly-medicated bass. In a case of unintentional gender-bending, some male fish are straight up switching sexes, developing ovaries where their testes are supposed to be.

Research lead Ramji Bhandari says that this phenomenon isn't dangerous just because of its general freakiness. He argues to The Washington Post that "If those trends continued, the potential for declines in overall population numbers might be expected in future generations."

Similar effects have been observed in Japanese medaka fish when exposed to the widely fretted-over chemical BPA, which was another component of Bhandari's study. Both EE2 and BPA are endocrine disruptors, meaning that they tamper negatively with the reproductive, developmental, neurological, and immune systems.

Although the study has been raising a lot of alarm in terms of fish populations, it's hardly news that the hormones in birth control pills have been making their way into the water supply. In 2012, a Forbes writer controversially argued that women who take birth control pills should be taxed $1,500 per year because of pollution caused to water systems. The writer acknowledged that such a tax would be ridiculous, but was trying to comment on the absurd cost that would be required to alter existing treatments so that they could effectively filter out hormones from the pills. It would cost the European Union roughly $46 billion, to be specific.

But other sources have pointed out that only 1 percent of the estrogen in drinking water comes from contraceptives. A report from all the way back in 2010 found that far more of the stuff was coming from agricultural sources, such as livestock waste, soy, and dairy foods.

So while hermaphroditic fish are certainly a concern, it may be wise to dig deeper before encouraging all the pregnancy-protected ladies in the US to give up their pack-a-month regimen.