Wastewater reveals Danes' use of drugs

About the study

The report focuses on the most commonly used drugs in Denmark:
cocaine, tramadol, alcohol, amphetamine, oxycodone, nicotine, methamphetamine, methadone, MDMA, codeine, ketamine, morphine, THC, and fentanyl.

The study was initiated and funded by the Danish Health Authority—and includes treatment plants in Copenhagen, Aarhus, Odense, Aalborg, Esbjerg, and Næstved. These six plants represent about 20% of the country's population.

Sample collection is carried out by local wastewater companies.

Some background data and sample material were provided by the Statens Serum Institut, which already handles wastewater surveillance in Denmark.

The Department of Forensic Medicine at Aarhus University is responsible for project management, analysis, and reporting.

For the first time, it is now possible to gain insight into Danes' consumption of, among other substances, cocaine, opioids, and alcohol measured via wastewater.

This is detailed in the report National kortlægning af rusmidler i spildevand fra danske byer (National Mapping of Drug Use in Wastewater from Danish Cities), which has just been published.

The Department of Forensic Medicine at Aarhus University conducted the extensive analyses, offering an intriguing look into Danish habits.

Several findings in the study surprised Associate Professor and Head of the Department of Forensic Medicine, Christian Lindholst, who authored the report.

Among other things, the results indicate that residents of Copenhagen, Aarhus, Odense, Aalborg, Esbjerg, and Næstved consume fewer opioids than the quantities legally sold by prescription in those six cities. But there is a difference in how many opioids the residents consume.

"I’m surprised by the relatively large differences we observe in the consumption of the opioids tramadol and oxycodone between the six cities. We see the highest levels in Aalborg, Esbjerg, and Næstved. The differences, which are also reflected in sales data, may be due to variations in prescribing practices and demographics," says Christian Lindholst.

At the same time, the results suggest that the illegal import of opioids in Denmark is significantly lower than the quantities legally prescribed.

Amphetamines for both everyday use and parties

Only three of the substances in the study show a clear pattern of higher intake on weekends compared to weekdays—these are cocaine, MDMA, and alcohol.
All other substances appear to be consumed at consistent levels throughout the week and year.

"It’s surprising that amphetamine and methamphetamine don’t exhibit the same usage pattern as the ‘party drugs’ cocaine, MDMA, and alcohol. We know many people take amphetamine—in the form of lisdexamfetamine—as part of treatment for attention disorders, but a large portion of amphetamine intake stems from illegally imported amphetamine. I had expected higher weekend usage here," says Christian Lindholst.

Wastewater analysis is one of the only measurement methods that can provide information on how many drugs Danes are actually consuming, and Christian Lindholst is positively surprised by the quality of the study.

"After all, we’re dealing with the collection of untreated wastewater. This bodes well for the future use of wastewater data for monitoring purposes," he says.

The study shows, among other things, that:

Cocaine excretion per capita, measured on weekdays during 2024, is highest in Copenhagen, while amphetamine excretion is highest in Esbjerg.
Cocaine, MDMA, and alcohol are associated with party environments. Excretion per capita of these substances is about 2–3 times higher on weekends than on weekdays. The other substances in the study are excreted relatively consistently throughout the week.
The presumed intake of MDMA and methamphetamine per capita is significantly higher in Copenhagen than in the other cities.
Excretion of the opioids tramadol and oxycodone per capita varies greatly between cities. The highest levels are observed in Aalborg, Esbjerg, and Næstved, while the lowest levels are seen in Copenhagen and Aarhus.
The estimated consumption of prescription opioids in the study is at or below the amount legally sold by prescription in the six cities. This may indicate that more prescription opioids are being issued than are actually consumed.
It was not possible to detect fentanyl in the study. This does not mean that fentanyl is not used in Denmark, but that the consumption is below the method’s detection limit.

Read the full report here.

Contact

Department head Christian Lindholst
Aarhus University, Department of Forensic Medicine
Email: cl@forens.au.dk
Phone: 20 93 92 23

This text is based on machine translation