Europe Samples Sewage Water to Find Its Biggest Drug Cities

Antwerp, Belgium Photograph by David Sanger/Corbis

The Belgian city of Antwerp is known for its Gothic cathedral and its skilled diamond cutters. It may also have a little-noticed drug problem. A new study revealed traces of cocaine, amphetamines, cannabis, and ecstasy in Antwerp’s sewage—all at levels among the highest of 42 European cities tested.

The study, published today in the British journal Addiction, represents the most extensive research yet in the emerging science of wastewater epidemiology. By testing samples of municipal sewage, researchers can see broad patterns in drug abuse, identify places where consumption is rising or falling, and even figure out what days of the week people tend to get high.

Until recently, most research on illicit drug consumption was based on self-reporting by users, who aren’t always a reliable source of information, says Christoph Ort, a researcher at the Swiss Federal Institute of Aquatic Science and Technology who is one of the study’s two lead authors. With wastewater testing, Ort says, “we can get an estimate of consumption based on small samples covering a large population.”

Some wastewater research has occurred in the U.S., including a 2008 study in which samples were taken on a single day from 96 municipalities in Oregon. That project found people in bigger cities were more likely to use cocaine and ecstasy than those in small towns.

But Europe has gone much further, testing in dozens of cities over the past three years. In the latest go-round, scientist analyzed wastewater from nearly 25 million people living in 42 cities and 21 countries. Researchers tested for metabolites that the body produces after ingesting drugs to be certain the substances had been “consumed, not flushed,” Ort says.

Daily samples were taken in each city over a seven-day period, allowing researchers to pinpoint days when drug use was most prevalent. Not surprisingly, “cocaine and ecstasy levels rose sharply at weekends in most cities,” according to a summary of the findings provided by the journal. “Methamphetamine and cannabis use appeared to be more evenly distributed throughout the week.”

The study has made headlines in Europe, with British newspapers such as the Daily Mail declaring London to be “the cocaine capital of Europe.” In fact, London ranked fourth for cocaine levels, behind Antwerp, Amsterdam, and Zurich. But the Brits may have another reason to worry: A report earlier this month by the country’s Drinking Water Inspectorate, found traces of metabolized cocaine in tap water. Apparently, it’s not being filtered out during water purification.

Overall, the new European study found that use of cocaine and ecstasy is most common in Western Europe, while methamphetamine use is heaviest in Eastern Europe.

Here, in order, are the cities whose wastewater had the highest levels of each drug tested:
• Cocaine: Antwerp; Amsterdam; Zurich; London; Barcelona;
• Amphetamines: Eindhoven, Netherlands; Antwerp; Gothenburg, Sweden; Ninove, Belgium; Deurne, Belgium;
• Methamphetamines: Prague; Oslo; Budweis, Czech Republic; Bratislava, Slovakia; Dresden, Germany;
• Ecstasy: Eindhoven, Netherlands; Utrecht, Netherlands; Amsterdam; Antwerp; Zurich;
• Cannabis: Novi Sad, Serbia; Amsterdam; Paris; Antwerp; Utrecht, Netherlands.

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