Scientists dive into sewage to learn the truth about drug use in Europe

Tabloid journalists have long known that you can discover dirty secrets by going through people’s garbage. Now, researchers have done something similar in the name of science, albeit on a grander — and smellier — scale. They have analyzed the sewage of 19 European cities to find out how much of certain illicit drugs people consume.

Researchers routinely use surveys, supplemented by data from police and customs officials, to measure illicit drug use. But they have been pushing for more accurate methods. One possibility is to sample the sewage of a city and look for chemical traces of the drugs themselves or metabolites created when a drug passes through the human body.

“The surveys tell you what people take, but not how much, not how big the market is,” says Kevin Thomas, a toxicologist at the Norwegian Institute for Water Research in Oslo and one of the authors of the paper published this month in the journal Science of the Total Environment. “Sewage tells you that.”

During one week in March 2011, Thomas and colleagues collected daily samples representing 24 hours of sewage flow from treatment plants in 19 cities across Europe. The samples were analyzed for traces of five drugs.

Cannabis consumption appeared to be similar throughout Europe, but there were striking regional differences in other drugs. Cocaine use per capita was highest in Belgium and other parts of Western and Central Europe, but lower in the north and the east. Ecstasy use was also highest in the Belgian city of Antwerp, London, and parts of the Netherlands. Meanwhile, methamphetamine levels per capita were highest in Scandinavian cities and Budweis in the Czech Republic. “This is really a snapshot of the drug flow through these European cities in March 2011,” says Thomas.

Some of the peaks may be due to drug production rather than consumption, Thomas says. And a spike in the ecstasy load in Utrecht, the Netherlands, might be due to a drug bust that coincided with the testing. “We are going with the theory that they tried to get rid of the evidence by shoving it down the toilet,” says Thomas. A follow-up study will include at least one U.S. city.

ScienceNOW, the daily online news service of the journal Science