Dublin is among the top 20 of 128 European cities for the presence of cocaine, ketamine and MDMA in its wastewater.
It follows a study by the EU drugs agency.
It is the largest European project monitoring illegal drug use through wastewater and saw sewage samples from 26 countries analysed over one week.
It found an increase in detections of MDMA, cocaine and amphetamine across Europe last year compared to 2023, while there was a drop in cannabis.
The data from the samples taken at the Ringsend treatment plant showed Dublin was 15th among cities analysed for levels of ketamine and 19th when it came to daily averages of cocaine and MDMA or ecstasy.
In the capital, the levels of cocaine detected increased during the weekend and peaked on Monday.
Samples from some 68.8 million people were analysed for traces of five stimulant drugs (amphetamine, cocaine, methamphetamine, MDMA/ecstasy and ketamine) – as well as cannabis.
While Europe-wide rises were seen in the detections of three of the stimulants (MDMA, cocaine, amphetamine), diverging patterns were observed for methamphetamine and ketamine. The highest loads of cannabis were found in western and southern European cities, particularly in Spain, the Netherlands, Norway and Portugal.
