What are the drug habits of European cities?

Recent wastewater analysis throws some light on regional differences in illicit substance consumption

Last week, the EU drugs agency (EMCDDA) published a report from a study which analysed the wastewater in 75 European cities from 25 countries with a view to tracing the most commonly used recreational drugs there.

From Barcelona to Limassol and from Oslo to Porto, the study analysed daily wastewater samples in the catchment areas of treatment plants over a one-week period between March and May 2021. The cities in the study are home to some 45 million people. The analysis searched for traces of four illicit stimulant drugs (cocaine, amphetamine, methamphetamine, MDMA/ecstasy) as well as for cannabis.

Wastewater epidemiology is a growing field

The 2021 study points to an overall rise in detections of four of the five drugs studied. MDMA was the only drug where decreases were recorded in the majority of the cities investigated. This can be explained by the fact that during the study period COVID curfews and restrictions were in force, and nightlife, which is the predominant scene for MDMA use, was severely curtailed.

Noteworthy in this latest data-collection round is the fact the drugs were reported more evenly across the study locations, with all five substances found in almost all of the participating cities. This differs from previous years when more diverse geographical patterns were observed.

The latest data show that cocaine, while still most prominent in western and southern European cities, is increasingly found in eastern European cities. Likewise, methamphetamine, historically concentrated in Czechia and Slovakia, is now found in cities across Europe.

Wastewater epidemiology is a burgeoning approach to studying the prominence of many biological and biochemical markers in the resident populations of large cities. For example, the same approach was used to also determine the prevalence of COVID in some cities during the pandemic.

In 2010, a Europe-wide network (Sewage analysis CORe group — Europe (SCORE)) was established with the aim of standardising the approaches used for wastewater analysis and coordinating international studies through the establishment of a common protocol of action.

The key findings in more detail

Here is a closer look at the results viewed through the lens of each substance use:

• Cocaine: Cocaine residues in wastewater remained highest in western and southern European cities (particularly in Belgium, the Netherlands and Spain), but traces were also found in the majority of eastern European cities, where some increases were observed. The city with the highest use of cocaine was Antwerp (Belgium).
• Methamphetamine: Traditionally concentrated in Czechia and Slovakia, this drug is now present in Belgium, Cyprus, the east of Germany, Spain, Turkey and several northern European countries. Still, the top 5 cities that show the highest concentrations of meth are all in Czechia, with Ostrava ranking first.
• Amphetamine: The level of amphetamine residues still varied across the cities, with the highest loads reported in cities in the north and east of Europe (Sweden, Belgium, the Netherlands and Finland) and much lower levels in cities in the south. The city showing the highest use of that drug is Sandviken in Sweden.
• Cannabis: The highest loads of cannabis metabolite (THC-COOH) were found in western and southern European cities, particularly Croatia, Czechia, Spain (Barcelona far outstrips the other European cities in that respect), the Netherlands, Slovenia and Portugal. Use appears to have been less affected by COVID-19 lockdowns than other drugs.
• MDMA: This was the only drug where residues decreased in the majority of the cities studied. Possibly due to the closure of nightlife venues during the COVID-19 pandemic, where this drug is often consumed. The highest loads of MDMA were found in cities in Belgium (with Amsterdam recording the highest use), Germany, the Netherlands, Sweden and Norway.