Wastewater analysis of drug-taking in 50 European cities
The latest findings from the largest European project in the emerging science of wastewater analysis were presented last week by the Europe-wide SCORE group, in association with the EU drugs agency (EMCDDA). The project analysed wastewater in 68 cities in 23 European countries to explore the drug-taking behaviours of their inhabitants.
From Stockholm to Barcelona and Santiago de Compostela to Nicosia, the study analysed daily wastewater samples in the catchment areas of wastewater treatment plants over a one-week period in March 2019. Wastewater from approximately 49 million people was analysed for traces of four illicit stimulant drugs: amphetamine, cocaine, MDMA (ecstasy) and methamphetamine (cannabis and heroin are not included in the study). Compared to previous years, the 2019 study points to an overall rise in the detection of the four drugs studied.
Wastewater-based epidemiology is a scientific discipline with the potential for monitoring close to real-time, population-level trends in illicit drug use (see the motion graphic below to see how it works). By sampling a known source of wastewater, such as a sewage influent to a wastewater treatment plant, scientists can now estimate the quantity of drugs used in a community by measuring the levels of illicit drugs and their excreted metabolites.
2019 key findings
The 2019 findings offer a valuable snapshot of drug use patterns in the cities involved, revealing marked geographical and temporal variations:
- MDMA: The 2019 data point to increased residues of MDMA in most cities, which may reflect this drug no longer being a niche or subcultural drug limited to dance clubs and parties, but now being used by a broader range of young people in mainstream nightlife settings. Of the 42 cities with wastewater data for 2018 and 2019, 23 reported an increase. The highest residues of MDMA were found in cities in Belgium, Germany and the Netherlands.
- Amphetamine: The most recent data show that most cities reported an increase in amphetamine residues. Of the 41 cities with data for 2018 and 2019, 21 cities reported an increase for amphetamine. The results varied considerably across the study locations, with the highest levels reported in cities in the north and east of Europe. Amphetamine was found at much lower levels in cities in the south of Europe.
- Cocaine: Of the 45 cities with wastewater data for 2018 and 2019, the latest figures reveal a further increase in cocaine use in 27 of them. Cocaine residues in wastewater were highest in western and southern European cities, particularly in cities in Belgium, the Netherlands, Spain and the UK. The analysis points to very low levels of cocaine use in the majority of eastern European cities, but the most recent data show here also signs of increases.
- Methamphetamine: Traditionally concentrated in Czechia and Slovakia, methamphetamine now appears to be present in Cyprus, the east of Germany, Spain and several northern European countries (e.g. Denmark, Lithuania, Finland and Norway). Of the 42 cities with wastewater data on methamphetamine for 2018 and 2019, 17 cities reported an increase. However, in contrast to the other three drugs, methamphetamine residues were very low to negligible in most locations.
- Weekly patterns: More than three-quarters of cities showed higher residues of cocaine and MDMA in wastewater during the weekend (Friday to Monday) than during weekdays, reflecting the predominantly recreational use of these substances, now seen in a range of social settings. For amphetamine, half of cities show higher residues in wastewater during the weekend than during weekdays, possibly indicating more use in recreational settings than in the past. In contrast, methamphetamine was found to be distributed more evenly over the whole week, possibly reflecting this drug being associated with more on-going and high-risk consumption by a small cohort of users.
- City variations: The study highlighted differences between the cities within the same country. This may be partly explained by the different social and demographic characteristics of the cities concerned (universities, nightlife areas and age distribution of the population). In the vast majority of countries, with multiple study locations, residues were higher in large cities compared to smaller locations for all four substances.
You can use the useful interactive chart here to investigate trends. The graphic below is a snapshot from when I was using the tool to look at cocaine levels in London.
Cocaine use in London down
Although cocaine residues in wastewater were high in the UK, levels in London had actually gone down considerably. The wastewater analysis looks at cocaine residues/metabolite (benzoylecgonine) in milligrams per 1000 citizens on a daily basis. In 2016, the last year for which data for London is available, the rate was 894.9mg/1000 people/per day. The 2019 equivalent figure was considerably lower at 618.8.
This is a somewhat surprising finding especially in the context of Dame Carol Black’s recent Review of Drugs which reports on the surge in the usage and quality of cocaine.
The EMCDDA adopts a multi-indicator approach to drug monitoring on the principle that no single measure can provide a full picture of the drug situation. The advantage of wastewater analysis is that it can provide timely information on a wide spectrum of substances.
It will be interesting to see whether these results are accurate and cocaine usage has gone down in the capital while perhaps increasing in other parts of the country where access to cocaine powder is easier following the expansion of the County Lines drug dealing approach.