More cannabis residue is found in waste water in Rotterdam than in any other city in Europe, the NRC said on Wednesday, quoting new European research.

The port city is also second highest when it comes to MDMA – the key component in ecstasy. The figures come from the European drugs research centre EMCDDA and offer a comparison between 88 European cities.

Samples were taken in 24 EU countries in spring 2023 and analysed for six drugs – meth, MDMA, cocaine, amphetamines, cannabis and ketamine.

Cities take part in the research on a voluntary basis and Amsterdam, Rotterdam, Leeuwarden, Utrecht and Eindhoven took part. Both Rotterdam and Leeuwarden signed up for the research for the first time.

The drugs agency said that there has been a marked increase in cocaine and MDMA use across the continent, following the dip during the coronavirus pandemic.

In Leeuwarden, more amphetamine residue per head of the population was found than in the other Dutch cities, placing it in fifth place on the Europe-wide list. The capital of Friesland was also fourth on the list for cocaine and third for cannabis.

Researchers said that Leeuwarden’s high position is notable because the city is not a major tourist destination and does not have a big student body. “It is on the high side,” Laura Smit-Rigter from the Dutch addiction centre Trimbos said.

All five Dutch cities were in the top 10 list for cannabis and cocaine use.