Wastewater reveals Danes' use of drugs and alcohol

11.06.2025 - Through wastewater analysis, the Department of Forensic Medicine at Aarhus University, on behalf of the Danish Health Authority, has measured Danes' consumption of, among other substances, opioids, alcohol, and cocaine. Several results have surprised the researchers behind the study, which is part of the government initiative Youth Without Opioids.

The Department of Forensic Medicine has conducted analyses of Danes' wastewater over the course of a year. These findings are now published in the report "National mapping of drugs in wastewater from Danish cities".

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

This is documented in the newly published report "National mapping of drugs in wastewater from Danish cities".

On behalf of the Danish Health Authority, the Department of Forensic Medicine at Aarhus University carried out the extensive analyses, providing an interesting look into Danes’ habits.

Several results surprised Associate Professor and Head of Department, Christian Lindholst, who is one of the authors of the report.

The study indicates, among other things, that residents in the six cities covered by the measurement—Copenhagen, Aarhus, Odense, Aalborg, Esbjerg, and Næstved—consume fewer opioids than the amounts legally sold by prescription. However, there are differences in how many opioids the residents consume.

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

The wastewater survey is part of the government's Youth Without Opioids initiative.

Amphetamines for both weekdays and parties

Only three of the substances studied show a clear pattern of higher consumption on weekends than on weekdays—these are cocaine, MDMA, and alcohol.

All other substances appear to be consumed at similar levels throughout the week and year.

"It is surprising that amphetamine and methamphetamine do not show the same consumption patterns as 'party drugs' like cocaine, MDMA, and alcohol. The use of amphetamine is stable throughout the week," says Christian Lindholst.

"We know that many take amphetamine—in the form of lisdexamfetamine—for the treatment of attention disorders, but a large part of the amphetamine use comes from illegally imported amphetamine. Here, I would have expected higher consumption on weekends," says Christian Lindholst.

Unlike survey studies, where respondents can give untruthful answers, wastewater analysis provides information on how many drugs Danes are actually consuming—and Christian Lindholst is positively surprised by the quality of the study.

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

Facts: About the study

Read the report here 

The report focuses on the most widely 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 covers wastewater 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 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.

The study shows, among other findings, that:

• Cocaine excretion per inhabitant is highest in Copenhagen.

• The presumed consumption of MDMA and methamphetamine per inhabitant is also significantly higher in Copenhagen than in the other cities.

• Amphetamine excretion is highest in Esbjerg.

• Cocaine, MDMA, and alcohol are associated with use in party environments, and the study shows a similar pattern. The excretion of cocaine, MDMA, and alcohol per inhabitant is about two to three times higher on weekends than on weekdays. The other substances in the study are excreted at relatively constant levels throughout the week.

• The excretion of the opioids tramadol and oxycodone per inhabitant varies significantly between cities. The highest levels are observed in Aalborg, Esbjerg, and Næstved, while the lowest are observed 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 prescribed in these cities than are actually consumed.

• It was not possible to detect fentanyl in this study. This does not mean that fentanyl is not used in Denmark, but that consumption is below the method’s detection limit.

Links: Read the report here

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