By: Robin Andrews/IFL Science There are certain things that you simply should never flush down the toilet. Plastic wrappers. Condoms. Beloved yet expired childhood pets. These things get stuck and cause several plumbing issues. The toilet is not a magical waste disposal portal; it is not a wardrobe into a Narnia-like dumping ground.
As some rather shocking research by the University of Exeter has shown, you can add contraceptive pills to that too. It appears that because of the frequency in which these are used, and sometimes flushed away, to the world below – along with numerous other chemical products – at least one-fifth of all male fish in English rivers are now “intersex” in that they have both male and female physical characteristics.
Tests at 50 sites across England carried out by Exeter’s Professor Charles Tyler, a leading eco-toxicologist, confirmed the bizarrely high prevalence of intersex freshwater fish. Perhaps most curiously, some are even laying eggs.
Others have dramatically reduced sperm quantities, and are far less aggressive and competitive when it comes to getting mates. Consequently, they are less able to breed and produce offspring.
Intriguingly, the offspring of such fish are much more likely to be sensitive to the affecting chemical products than their non-contaminated compatriots are.
The most common contraceptive pill contains the female hormones estrogen and progesterone. Although it is not explicitly stated, it could be possible that an overload of these chemicals being released in the urine of those using them, or perhaps flushed down the toilet in pill form, is what’s driving the so-called “feminization” of the freshwater fish. There are at least 200 other sewage-derived compounds that are known to have similar physiologically altering effects, including the byproducts of cleaning agents, cosmetics and plastics.
“We are showing that some of these chemicals can have much wider health effects on fish that we expected,” Tyler said in a statement.
Explaining how his team knows that these products have these unusual effects on the fish, Tyler added: “Using specially created transgenic fish that allow us to see responses to these chemicals in the bodies of fish in real time, for example, we have shown that oestrogens found in some plastics affect the valves in the heart.”
Antidepressants are also altering the behavior of fish in some rather unexpected ways. These drugs “reduce the natural shyness of some fish species, including the way they react to predators.”
Although not yet published in a peer-reviewed journal, the results of the research will be presented at the 50th Anniversary Symposium of the Fisheries Society, held in Exeter this week. It’s not hard to argue that this rather specific gathering is the ideal place in which to present this work for the first time.
In the meantime, if you can avoid flushing things other than tissue paper down the toilet, then nature would thank you for it.