There is more cannabis residue in wastewater sampled in the Frisian capital of Leeuwarden than in Amsterdam, according to research carried out on behalf of the city council.
Water research institute KWR carried out the testing, which revealed the concentration of cannabis in the provincial capitalβs water to be βextraordinarily highβ.
The water was tested over a week-long period in March and the researchers said, showed that 3362 milligrams of THC were consumed per 1,000 people in Leeuwarden. That is the equivalent of 21 grammes of marijuana.
The figure is seven percentage points higher than in Amsterdam and almost 50% up on Utrecht and Eindhoven. The testing did show a lower use of MDMA in the northern province but cocaine use was on a par with the Dutch capital.
Leeuwarden mayor Sybrand Buma told local broadcaster Omroep Fryslan results of the tests require βaction on all sidesβ.
βWe need to raise awareness of drugs use as well as tackling drugs-related crime,β he said.
The research was initiated by the CDA and local water board because of concerns about the high percentage of drug users in Leeuwarden and to find out how much drug residue is being filtered out by waste water processing.
Markus Jansen 
Agnita Meijer
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