The Whitelake River flows through Worthy Farm in Somerset, UK, home to the massive Glastonbury music festival. Turns out that festivalgoers' public urination at the site has caused the river to briefly flow with high levels of cocaine and MDMA that could harm the critically endangered European eels that live there. From CNN:
Christian Dunn, a professor in wetland science at Bangor University, who led the study, told CNN Tuesday that the levels of illegal drugs were "high enough to be classed as environmentally damaging," although he added the caveat that levels "decline pretty quickly after Glastonbury has finished."[…]
The researchers said the increase in drug levels had come from festival goers urinating in public, causing the chemicals to eventually enter the river — which happens particularly quickly in wet weather conditions.
"This has highlighted the fact that stopping public urination is so important," Dunn said. "Not just for the traditional pollutants, which we've kind of known about, but for these these types of pollutants, which we're only now really just becoming aware of — pharmaceutical waste, illicit drug waste — these are important."
"The environmental release and ecosystem risks of illicit drug during Glastonbury Festival" (Environmental Research)