—— Down the drain and forgotten? No, because our wastewater can provide an astonishing amount of data, revealing much about our way of life. It can also help in identifying social problems at an early stage.

Photo of water in motion. The water pours from the upper left corner of the image to the lower right. It is a compact body that shimmers and fluoresces in different colors. The background is a gradient of colors.


When João Matias looks at the data from the past two years, they confirm his predictions. Matias works at the European Monitoring Centre for Drugs and Drug Addiction, or EMCDDA—an agency of the European Union—and, from Lisbon, monitors how drug use is changing across Europe.

There was quite a shift during the pandemic: while far fewer people were taking ecstasy (MDMA), Matias saw a significant increase in the use of cocaine and all the other drugs monitored by the EMCDDA. His explanation is that ecstasy, as a party drug, was less attractive during the lockdowns so people were more likely to use cocaine and amphetamines because those are also taken at home, not just in clubs.

The current report from the year 2021 again shows clear differences between the days of the week. In Antwerp, for example, weekend use of cocaine was 1,700 milligrams per 1,000 people and day, while during the week it was just 1,423 milligrams. Matias was able to make similar observations for MDMA use, noting that the drug remains especially popular in cities in Belgium, Germany, the Netherlands, Sweden and Norway. For amphetamines, methamphetamine and cannabis, in contrast, levels remained stable across the week. Matias says that these drugs are part of everyday life for many people, especially in cities in Croatia, Spain, the Netherlands and Slovenia.

That he is able to draw any of these conclusions is based on wastewater analyses. “Everything we eat, drink, smoke or inject enters our systems, where our bodies metabolize it and then excrete it,” he explains. These residues can then be detected in wastewater and allow conclusions to be drawn about the lives of populations. But how exactly does wastewater analysis work? And what potential does it offer?

Drawing conclusions from wastewater

Wastewater analysis is a developing field. In the 1990s, it was used to research the environmental impacts of domestic wastewater. Today it has many uses: for monitoring drug use in Europe, but also for keeping an eye on a population’s health and looking out for potential dangers.

The analysis procedures vary depending on what’s being looked for. Together with the SCORE Network, the EMCDDA, which has been monitoring the circulation of drugs in Europe for the past eleven years, studies samples from various European cities for its annual report. In 2021, 75 municipalities in 23 European countries volunteered to provide the samples.

Researchers first look for metabolites in the wastewater. These chemical compounds are found within cells and are produced by enzymes during metabolism. Chemical analyses can reveal what drugs were consumed since each drug has a different metabolite. Cocaine can be identified via benzoylecgonine (BE), cannabis by THC-COOH (11-Nor-9-carboxy-9-tetrahydro- cannabinol). This information is then used to calculate the amount of drugs consumed by the number of people connected to the wastewater system being studied

“We can now determine how much powder cocaine has been snorted or crack cocaine smoked.”

João Matias, researcher into drug use at the European Monitoring Centre for drugs and drug addiction

Precision and pitfalls

“One week per year, we collect samples in each of the participating cities, allowing us to analyze almost in real time where the hotspots are and the quantities consumed per 1,000 people on a given day and in a given city,” ­Matias says. For him, the precision is one of the key advantages compared to other methodologies. Unlike survey results, the wastewater data delivers more honest answers. Sometimes drug users don’t even know exactly what it is they’re taking.

Yet the method also has its pitfalls. Not all drugs can be detected unfailingly with wastewater analysis. “We can’t deliver any data about heroin because it metabolizes into morphine in the body,” he says. To date, researchers remain unable to distinguish between morphine in wastewater from heroin use as opposed to from medication. Furthermore, since the wastewater samples are collective, it is also impossible to trace whether a few people are taking a lot of drugs or many people just smaller amounts. Nor is it easy to determine the purity of the drugs, how often they are taken, or how they are ingested—except for cocaine. “We can now determine how much powder cocaine has been snorted or crack cocaine smoked because of the difference in the excreted metabolites,” he says.

The researchers must also take local events into account in their analyses. If, for instance, wastewater from a music festival makes its way into a city’s sewage treatment plant, that distorts the data, so they would remove it from their overall analysis. Or, for example, if drugs were dumped into the toilet during a drug raid, that would also affect the data. In this case, the EMCDDA has another analytical method at the ready: they can directly examine the substance in the wastewater and differentiate between drugs that have been consumed and those that have been flushed down the drain.

Photo of pills and tablets of different colors lying in transparent liquid. Some are in a state of dissolution. The liquid shimmers colorfully and fluoresces.
WHO’S TAKING WHAT? Party drugs such as ecstasy became less popular during the pandemic, when people were more likely to turn to cocaine. The EMCDDA knows which drugs are the most popular in which cities.

Drugs, diseases and antibiotic resistance

Numerous other research organizations besides the EMCDDA are also using wastewater analysis, for example to study the spread of diseases. The “SARS-CoV-2 Wastewater Monitoring in Thuringia” pilot project, run by the Bauhaus University in Weimar and the company Analytik Jena, will be providing wastewater monitoring for Covid-19 outbreaks across the federal state. The Chair of Urban Water Systems Engineering at the Technical University Munich is researching a similar project and has been receiving funding from Germany’s Federal Ministry of Education and Research since last year.

Wastewater analysis could make it possible to get local outbreaks more quickly under control because the data doesn’t rely on the population’s willingness to get tested. In addition, the data from wastewater provides information about the current situation more quickly than tests, and could detect both mutations and asymptomatic infections. The university is still researching the specific implementation, but over the long term they hope to apply the methodology to the detection of other viruses.

At the Karlsruhe Institute of Technology, Dr. Thomas Schwartz has been working on wastewater analysis since before the pandemic. Instead of looking for drugs or corona infections, he has been tracking antibiotic-resistant bacteria and is developing potential solutions to filter multi-resistant germs out of the wastewater. That’s because even from the sewers, these germs pose a growing threat, causing concern among experts. “Right now it is predicted that infections with antibiotic-resistant germs will be responsible for 10 million deaths annually by 2050, overtaking cancer, cardiovascular disease and diabetes as cause of death,” he says. Wastewater analysis can be used to detect the concentrations of such organisms and to monitor their development.

“In the future, wastewater will become an early-warning tool.”


What can wastewater analysis achieve?

As appealing as the potential of wastewater analysis may sound, for Matias it’s how it’s applied that matters. To ensure that these analyses aren’t used for the wrong purposes, he developed ethical guidelines for the EMCDDA team back in 2015. These state that such analyses will only be conducted in cities and not in smaller municipalities so that specific individuals cannot be identified. The guidelines also state that they shouldn’t be used in schools or prisons. Nevertheless, some countries do use the analyses in such ways, because the guidelines are only suggestions and are not legally binding.

For Matias and the EMCDDA, it is far more important to use wastewater analysis to highlight large-scale developments at an early stage and to point out potential dangers—whether of drug use or disease. For example, the analysis could also help to evaluate the effectiveness of policy measures such as addiction treatment programs. Samples could be collected beforehand and afterwards and then evaluated, hopefully delivering reliable results.

This is where Matias sees the strengths of the methodology and is confident: “In the future, wastewater will become an early-warning tool.”