The latest findings from the largest European project in the science of wastewater analysis are released in Wastewater analysis and drugs a European multi-city study, published by the Europe-wide SCORE group, in association with the EU drugs agency (EMCDDA).
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The analysis reveals a rise in cocaine and methamphetamine detections and describes how wastewater research can now tell us more.
The project analysed wastewater in a record 104 European cities from 21 countries (20 EU + Türkiye) to explore the drug-taking behaviours of their inhabitants. Ketamine was included in the analysis for the first time in 2022, bringing the total number of substances examined to six.
From Copenhagen to Valencia and Nicosia to Lisbon, the latest study analysed daily wastewater samples in the catchment areas of wastewater treatment plants over a one-week period between March and April 2022.
Wastewater samples from some 54 million people were analysed for traces of five illicit stimulant drugs (cocaine, amphetamine, methamphetamine, MDMA/ecstasy and ketamine) as well as cannabis.
The latest results show a continued rise in cocaine detections, a trend observed since 2016 (despite some fluctuation during COVID-19 lockdowns).
The methamphetamine situation also appears to be evolving, with more cities reporting traces of the drug. A mixed picture emerges for the remaining substances where trends can be observed (amphetamine, cannabis, MDMA).
Despite detections varying considerably across the study locations, it is noteworthy that all six illicit drugs investigated were found in almost every participating city.
• Cocaine:
Cocaine residues in wastewater remained highest in western and southern European cities (particularly in Belgium, the Netherlands, Spain and Portugal), but traces were also found in the majority of the eastern European cities, where some increases were observed.
Overall, over half (38) of the 66 cities with data for 2021 and 2022 recorded increases in cocaine residues (18 cities reported no change and 10 a decrease). A recent European project on wastewater (EUSEME) also found crack cocaine residues in all of its 13 European cities, with the highest loads in Amsterdam and Antwerp.
• Methamphetamine:
Traditionally concentrated in Czechia and Slovakia, this drug is now also present in Belgium, the east of Germany, Spain, Cyprus and Turkey and several northern European countries (e.g. Denmark, Latvia, Lithuania, Finland and Norway).
Of the 60 cities with data for 2021 and 2022, almost two-thirds (39) reported an increase in residues, 15 a decrease and six a stable situation. Elsewhere, methamphetamine loads were very low to negligible, although some increases were reported in central and southern European cities.
The three cities with the highest loads were all situated in Czechia, followed by cities in Latvia, Germany, Turkey and Cyprus.
• Amphetamine:
The level of amphetamine residues varied, with the highest loads reported in cities in the north and east of Europe (Belgium, Germany, the Netherlands, Finland and Sweden) and much lower levels in cities in the south.
Of the 55 cities with data on amphetamine residues for 2021 and 2022, the picture was mixed, with 20 reporting an increase, 26 a decrease and nine a stable situation.
• MDMA:
Here the picture is also mixed. Of the 62 cities with data for 2021 and 2022, 28 reported an increase in MDMA detections (mostly in cities in Southern and Central Europe), 27 a decrease (mostly in northern Europe) and seven a stable situation.
The highest mass loads of MDMA were found in wastewater in cities in Belgium, Czechia, the Netherlands, Spain and Portugal.
• Ketamine:
Following signs of increased availability and use of ketamine in Europe (EDR 2022), the drug was included for the first time in the 2022 analysis. The highest mass loads were found in wastewater in cities in Denmark, Italy, Spain and Portugal.
• Cannabis:
The highest loads of the cannabis metabolite THC-COOH were found in western and southern European cities, particularly in Czechia, Spain, the Netherlands and Portugal. In 2022, diverging trends were seen (18 cities out of 38 reported a decrease since 2021, 15 an increase and five a stable situation).
• City variations:
The study revealed differences between cities in the same country, which may be partly explained by their different geographical, social and demographic characteristics (age distribution, universities, nightlife).
In most countries with multiple study sites, residues were higher in large cities compared to smaller locations for three of the stimulants (cocaine, methamphetamine, MDMA). No such differences were detected for amphetamine and cannabis.
• Weekly patterns:
Wastewater analysis can detect fluctuations in weekly patterns of illicit drug use. More than three-quarters of the cities showed higher residues of drugs often associated with recreational patterns of use (cocaine, ketamine and MDMA) at the weekend (Friday–Monday).
In contrast, residues of the other three drugs were distributed more evenly throughout the week.
Although primarily used to study trends in illicit drug use in the general population, wastewater analysis can also be applied to precise locations (e.g. music festivals, specific neighbourhoods) to provide timely data. ■