Wastewater analysis reveals Belgians' drug consumption trends

Analysis of wastewater by Belgian health agency Sciensano has revealed widespread cocaine use in most major Belgian cities, according to a new study looking at samples from March 2025.

Sciensano carried out large-scale monitoring of drugs at 17 wastewater treatment plants located in major urban centres across the three regions, analysing traces of eight different drugs.

Cocaine was found in all treatment plants, as well as widespread use of ketamine and MDMA in all regions.

Maarten Degreef, a drug expert at Sciensano, said that analysing wastewater provides data that is not subject to bias.

“There’s no problem with people lying or not knowing what they have used,” Degreef said.

“It really complements other data sources. It confirms what we expected, but it also helps us to better understand phenomena such as methamphetamine. It also allows us to move away from the idea that cocaine or crack is mainly consumed in Brussels, when in fact it is widespread.”

While wastewater analysis has been used in Belgium to detect viruses, medicines or drugs in the past, the scale of this most recent study is unprecedented for Sciensano, both in terms of the number of treatment plants where samples were analysed and their distribution throughout the country, and in terms of the number of drugs included.

Until now, measurements have mainly targeted the Brussels-North and Antwerp-South plants.

Sciensano emphasised the need to conduct repeated monitoring campaigns throughout the year, given the rapid disappearance and reappearance of substances on the drug market.

Cannabis and opioids were not included in the study, which complements a similar one carried out by the European Drug Agency (EUDA) in several European cities.

The Belgian study’s findings include that while cocaine, MDMA and ketamine are widely consumed in all regions of the country, the use of amphetamines is more limited and that of methamphetamines is rarer.

Depending on the days of analysis, Sciensano also found variations in the concentrations measured, which makes it possible to establish a link between drugs such as cocaine and MDMA and their use in nightlife venues, which is not the case for amphetamine and ketamine.

Crack consumption was also detected in all regions of the country and "requires special attention" in drug use policies, given its increased visibility and associated health risks, Sciensano said.

Biomarkers of its consumption were detected in 11 of the 17 wastewater treatment plants sampled, as was most prevalent at the Antwerp-South plant. While media has often referred to Brussels as the epicentre of crack-cocaine use, its two sewage treatment plants ranked fifth and eighth in terms of biomarker presence.

When it comes to regular cocaine, the most commonly used stimulant among the general population in Belgium, record levels were found in Arlon and Marche-en-Famenne during weekends. But the highest average daily concentration per 1,000 inhabitants was measured at the Antwerp-South wastewater treatment plant, with Brussels-North in second place.

That the highest concentrations were generally detected during the weekend confirms the popularity of cocaine in nightlife venues, according to Sciensano’s analysis.

MDMA use has regional differences, being more prevalent in Flanders and Brussels than in Wallonia. Its use is also more associated with nightlife due to higher concentrations during weekends.

Usage of amphetamine, or speed, also showed regional variations. Concentrations are higher in Flanders - especially in Hasselt and Antwerp-South - than in the rest of the country.

Sciensano offered two possible explanations: greater availability of amphetamines in Flanders, given that two-thirds of the drug laboratories seized in Belgium were located in the provinces of Limburg and Antwerp, and a link with the Dutch drug market.

Synthetic cathinones (3-MMC and 4-MMC or mephedrone), which have similar effects to amphetamine, are scarce on the Belgian market.

Only one of them (4-MMC) has been detected, and only in two Flemish wastewater treatment plants (Ghent and Harelbeke), despite the fact that these synthetic drugs still account for 5% of all drug seizures in Belgium and 5% of contacts regarding illicit drugs with organisations such as the Belgian Poison Control Centre.

Methamphetamine consumption was observed throughout Flanders and Brussels in Sciensano’s study, with no samples testing positive in Walloon wastewater treatment plants.

Sciensano offered the same explanation for this regional difference as for amphetamine - a higher number of drug laboratories in Flanders.

Apart from the sites in Antwerp-South and Brussels-North, methamphetamine use remains limited in Belgium.

Lastly, biomarkers of ketamine were found in all wastewater treatment plants except the one serving the town of Marche-en-Famenne. Sciensano highlighted its widespread availability in the country and "the urgent need to adapt health interventions to a large target population… and to focus on the reasons why ketamine has gained popularity in such a short time".

Customs officials at Liège Airport seized 70kg of this drug just this week, bound for the United States.

The drugs were concealed in a cardboard parcel from the Netherlands and, with the average price of the drug an estimated €20 per gram, the value of the seizure is estimated at €1.4 million.

The volume points to organised trafficking and an investigation is ongoing.