Alex Ford, UK Marine Biology professor at the University of Portsmouth, says that when the sewage treatment plant at Hampshire's Langstone Habor, on the southern coast of England, becomes overloaded, it spills raw sewage into the harbor. That means that it's dumping not just human excrement, but also the drugs that excrement contains, including contraceptives, anti-depressants, and cocaine. Link to an article in The Independent here.
These drugs then enter the systems of the marine wildlife, and affect their chemistry and behavior.
The Guardian reported that raw sewage discharges in England have reached record levels, with an increase of 105% over the past year. Link here.
Here is an interview with Professor Ford, in which he explains what effects the drugs have on marine wildlife.