Data on samples collected in wastewater are included in the study "Wastewater analysis and drugs" - carried out in 75 cities in 25 countries, with data collected in Lisbon, Almada and Porto in Portugal – which refers to 2021 and is published by the European group SCORE, in collaboration with the European Monitoring Center for Drugs and Drug Addiction (EMCDDA).


According to elements made available by the EMCDDA to the Lusa agency, “the 2021 results point to an overall increase in the detections of four of the five drugs studied” (cannabis, cocaine, amphetamines, methamphetamines and MDMA, with MDMA being the only substance that recorded decreases) in most of the cities investigated.

The main conclusions of this study, carried out between March and May 2021, in the midst of restrictions resulting from the covid-19 pandemic, point out that cocaine residues in wastewater continued to be higher in cities in western and southern Europe (in particularly in Belgium, the Netherlands and Spain), but traces were also found in most cities in Eastern Europe, where some increases were observed.

“Globally, in 2021, more than half of cities recorded increases in cocaine residues compared to 2020 data (32 of 58 cities with data for both years)”, says the EMCDDA, recalling that another recent European Wastewater Project (EUSEME) detected crack cocaine residues in all 13 European cities that participated, with the highest loads in Amsterdam (Netherlands) and Antwerp (Belgium).


As regards methamphetamine, a drug “traditionally concentrated in the Czech Republic and Slovakia”, it is now present in Belgium, Cyprus, eastern Germany, Spain, Turkey and several northern European countries (Denmark, Lithuania, Finland, Norway).

The level of amphetamine residues varied between cities, with the highest loads being reported in northern and eastern European cities (Sweden, Belgium, the Netherlands and Finland) and much lower levels in southern cities, although that more than half (28 out of 55) of cities with data for 2021 and 2020 reported an increase in waste found.

MDMA down

MDMA was the “only drug” where residues decreased in most cities studied.

The study justifies this trend, in which almost two-thirds of cities with data for 2021 and 2020 (38 out of 58) reported a decrease in loads in 2021, “possibly due to the closure of nightlife venues during the covid-19 pandemic, where this drug is frequently consumed”.

The highest MDMA residues were found in cities in Belgium, Germany, the Netherlands, Sweden and Norway.

According to the EMCDDA, the study reveals differences between cities in the same country, which can be partially explained by their different social and demographic characteristics (age distribution, universities, nightlife, among others).

“In most countries with multiple study sites, residues found were higher in large cities than in smaller sites for three of the stimulants. No such differences were found for amphetamine and cannabis. Seventeen of the countries that participated in data collection in 2021 included two or more study sites,” the report explains.

Weekly fluctuations

With regard to consumption, wastewater analysis found fluctuations in weekly patterns of drug use, with more than three-quarters of cities reporting higher levels of residues of typically recreational drugs, cocaine and MDMA, at weekends ( from Friday to Monday) than during the week, despite the fact that much of the night time economy was shut down in Europe in 2021.

In contrast, residues from the other three drugs were more evenly distributed throughout the week.

From Barcelona (Spain) to Limassol (Cyprus) and from Oslo (Norway) to Porto (Portugal), the study analysed daily samples of wastewater in the areas affected by wastewater treatment plants during periods of one week, between March and May 2021.

Wastewater from around 45 million people was analysed for traces of four illicit stimulant drugs (cocaine, amphetamine, methamphetamine, MDMA/ecstasy) as well as cannabis.

The SCORE group has carried out annual wastewater monitoring campaigns since 2011, when 19 cities participated, in a total of 10 countries.

Widespread use

The director of the EMCDDA, Alexis Goosdeel, says, quoted in a statement, that the findings of this study “allow us to have a valuable picture of drug use in 75 cities, providing important information on emerging trends”, noting that “the results show an increase and spread of most of the substances studied, reflecting a problem of consumption of drugs simultaneously widespread and complex”.

“Over the last decade, wastewater analysis has evolved from an experimental technique to a consolidated tool for monitoring illicit drug use in Europe. This study explores the potential for future research on wastewater, from the identification of new psychoactive substances to the evaluation of interventions aimed at public health programs and the strengthening of preparedness and response”, concludes Aléxis Goosdeel.