Analysis of effluent at wastewater treatment plants in 42 cities in 21 European countries has discovered the pattern of use of five major illicit drugs - cocaine, amphetamine, ecstasy, methamphetamine and cannabis - and the most popular drugs in each of the different cities.

Breaking Badly: a busted meth lab.Right: Breaking Badly: a busted meth lab. Guess what goes down the toilet?

The study, written up in ‘Spatial differences and temporal changes in illicit drug use in Europe quantified by wastewater analysis’ and published in the scientific journal, Addiction, was conducted by scientists in the SCORE (Sewage analysis CORE group) network.

It has enabled cities to be ranked in terms of the illicit drug of choice, and found that Antwerp (districts Zuid and Duerne) in Belgium comprises the one municipal region that features the highest in all five tables together, and, perhaps unsurprisingly, Amsterdam the top single city.

The results, which used liquid chromatography coupled to mass spectrometry, confirmed and corroborated with the results of traditional surveillance data by law enforcement agencies.

This establishes that analysis of wastewater can quantify total illicit drug use in an area more quickly and regularly than other methods, and can be used to create estimates of drug use in a given area even where such data does not exist.

This approach cannot provide information on the behaviour of individual households and on their demographics but it can be used to provide additional information to understand the illicit drug situation more clearly.

The new study is the first to use a common protocol and adequate quality control measures to look at multiple countries over multiple years. The data used was as follows:

  • in 2012, 25 wastewater treatment plants (WWTPs) in 11 countries were included (23 cities, total population 11.50 million); 
  • in 2013, there were 47 WWTPs in 21 countries (42 cities, total population 24.74 million);
  • For comparison, 2011 data were also used (21 WWTPs in 11 countries; 19 cities, total population 14.12 million).

The tables below summarize all results.

The top 10 cities for cocaine use are:

  1. Antwerp Zuid
  2. Amsterdam
  3. Zurich
  4. London
  5. Barcelona
  6. Valencia
  7. Eindhoven
  8. Antwerp Deurne
  9. Basel
  10. Geneva.

The top 10 cities for amphetamine use are:

  1. Eindhoven
  2. Antwerp Zuid
  3. Gothenberg
  4. Ninove (Belgium)
  5. Antwerp Deurne
  6. Dortmund
  7. Amsterdam
  8. Helsinki
  9. Dülmen (Germany)
  10. Utrecht.

The top 10 cities for methamphetamine use are:

  1. Prague
  2. Oslo
  3. Budweis (Czech Republic)
  4. Bratislava (Slovakia)
  5. Dresden
  6. Piestany (Slovakia)
  7. Turku (Finland)
  8. Gothenberg
  9. Santiago (Spain)
  10. Helsinki.

The top 10 cities for ecstasy use (MDMA) are:

  1. Eindhoven
  2. Utrecht
  3. Amsterdam
  4. Antwerp Zuid
  5. Zürich
  6. Barcelona
  7. London
  8. St. Gallen (Switzerland)
  9. Antwerp Deurne
  10. Berne.

The top 10 cities for cannabis use are:

  1. Novi Sad (Serbia)
  2. Amsterdam
  3. Paris
  4. Antwerp Zuid
  5. Utrecht
  6. Barcelona
  7. Athens
  8. Eindhoven
  9. Castellon (Spain)
  10. Oslo.

The method of analysing wastewater to determine illicit drug use in an area has the following advantages:

  • The data can be obtained within a short time frame;
  • It is not prone to response biases;
  • It can help in identifying the spectrum of drugs being used by a population.

The researchers say that this is particularly important given the emergence of new psychoactive substances and so-called 'legal highs'. Often, users are unaware of the actual chemical constituents of these drugs, which makes self-reporting unreliable. Analysis of wastewater will instead provide accurate results.

This study is only the latest of many studies conducted worldwide of a similar nature. In some cities analysis is done on daily, weekly, monthly or annual basis to show variations in drug use. For example it can reveal a higher use of these substances during weekends. Some studies have shown that there is typically an increase of illicit drug use during holiday periods.

Other studies, in Italy and Australia, have shown yearly trends in illicit drug consumption. Wastewater studies in different countries also reveal regional variations in drug use.

Three studies have looked at the influence of urbanization on the use of illicit drugs: in Oregon, South Australia and Queensland. They have found that the use of illicit drugs is higher in urban regions compared to more rural areas, confirming the beliefs of parents of children in rural areas that if they leave home to go to the city they are more at risk of encountering exposure to drug use.

The conclusions of the SCORE group are taken up in the European Drug Report 2014, launched this week by the European Monitoring Centre for Drugs & Drug Addiction (EMCDDA), as well as in an online interactive analysis by the agency.

Lead investigator, Dr Barbara Kasprzyk-Horden, at the University of Bath’s Centre for Sustainable Chemical Technologies, which participated in the study, said: “Analysing sewage for estimating drug use has huge potential for monitoring the health of populations. Traditional epidemiological methods rely on surveys, which are time consuming, expensive and can be inaccurate due to self-reporting bias.

“However waste water profiling is non-intrusive and can show changes in local populations in real time, with a large sample size and can be used alongside existing epidemiology methods to give important information on drug use and markets across Europe. This tool is exciting because it could also be used to identify the use of new dangerous ‘legal highs’ that have not yet been banned. It also has potential to be used to monitor biomarkers for diseases such as cancer or trace the spread of flu epidemics in real time and could be a really powerful tool for improving public health.”