Who doesn't love an outdoor music festival?

From the iconic Glastonbury in the UK to Woodstock in the US, hundreds of thousands of people from across the world flock to these events to indulge in music, dancing, drinking and yes - don't tell your mum - sometimes even drugs.

However, these illicit substances, coupled with the public urination that is a common sight at festivals could be responsible for contaminating local rivers.

And if that wasn't bad enough, it's messing with endangered marine life, according to scientists.

A new study published in the journal Environmental Research, scientists at Bangor University in Wales found water collected from the Whitelake River in Somerset following the 2019 Glastonbury Festival had worrying levels of both MDMA and cocaine.

The researchers tested the river upstream and downstream of the festival site in the weeks before, during, and after the festival. Traces of the drugs were found to be significantly highest during the weekend after the festival in the Whitelake site, downstream of the festival.

MDMA was detected at “environmentally damaging levels,” according to the paper, while levels of cocaine were high enough to impact the local population of European eel, a species that is critically endangered and at high risk of extinction.

The eels don't even get to 'enjoy' the drugs. Previous studies have shown it can result in muscle damage and disrupts their complex lifecycle.

While festival-goers are encouraged to use official toilets provided, anyone who's been to a festival knows public urination is a common sight. Since some recreational drugs and their metabolites are excreted in pee, the team behind the study believes drug-laced urine could be seeping into the ground, making its way downstream from the festival site and into nearby waterways.

While the Glastonbury festival was the subject of the study, the researchers argue this is a much wider issue.