The team, which included researchers and scientists from Eawag, Switzerland’s aquatic research institute, examined the sewage from about 15 million people across 19 cities in Europe.
Researchers measured the concentrations of various substances in the waste across a one-week period. Christoph Ort, from Eawag’s Department of Water Management helped design the study to ensure that data from each city could be effectively compared.
Antwerp and Amsterdam were found to be at the top of the 19 cities, with approximately 1.5 grams per 1,000 people per day. These figures compare with the results obtained last year from a joint study between Eawag and the University of Bern, who investigated the concentrations in the sewage from Bern, Zurich, Geneva and Lucerne.
“The amounts of cocaine in the waste were in the same range as those European cities with the highest consumption," Ort said in a press release.
The study also found that during music events such as the forthcoming street parade, consumption was between two and four times higher than on a normal day.
The Swiss results were obtained over a shorter period of time so researchers hope now to broaden the project across a longer stretch and to include other Swiss cities including Basel and St. Gallen, as well as other European and American cities.