The EU's drug monitoring body analysed sewage samples from 68 cities in 23 European countries in March 2019.
Sewage was tested for traces of four illicit drugs: amphetamine, cocaine, MDMA (also known as ecstasy) and methamphetamine.
The tests showed an overall rise in the four drugs compared to previous years.
More than half of the 42 cities where wastewater was tested reported an increase in ecstasy residues compared to 2018, the study found.
The agency said the increase suggested ecstasy was no longer "a niche or sub-cultural drug limited to dance clubs and parties", but was now "being used by a broader range of young people in mainstream nightlife settings".
Source: BBC News, 12th March 2020