The data is part of the latest wastewater analysis study produced by the EU drugs agency EMCDDA and the sewage analysis group SCORE.
Results are based on the analysis of wastewater in 73 cities in 20 European countries over a one-week period in March 2018 as part of a bid to establish the drug-taking habits of residents.
The figures show an overall European-wide increase in traces of cocaine in wastewater in line with the trend seen in 2017 results.
They also show that Swiss cities continue to have remarkably high levels of cocaine use, although these cities do not appear quite as high in the rankings as last year.
In Swiss cities the consumption of cocaine and ecstasy certainly appear to have remained at a high level. This is shown by new wastewater data. The analyses and evaluations of the wastewater in Switzerland were conducted by the @unil and #Eawag. https://t.co/jkgfGK5qKb
— Eawag (@EawagResearch) March 14, 2019
Zurich ranked third in terms of daily use in the latest ranking – one place down on last year and now behind Bristol and Amsterdam.
Meanwhile, St Gallen in eastern Switzerland ranked sixth (two places lower than last year), Geneva came seventh (also two places lower) and Basel was ninth (down one place).
The Swiss capital of Bern was in 11th place, against ninth last year.
Switzerland also continues to rank highly for ecstasy use with Zurich (3rd), St Gallen (7th) and Geneva (8th) all in top ten for daily use, according to wastewater analysis.
Discussing the importance of the findings, the EMCDDA notes that while “no single measure can provide a full picture of the drug situation”, wastewater analysis is a valuable part of the toolkit when it comes to establishing a picture of drug-taking habits.
The agency notes this wastewater analysis is positive in that it sidesteps the bias of drug user surveys. On the hand, it is limited in that it cannot provide information on factors like prevalence and frequency of use, the numbers of users, the types of user and the purity of the drugs being taken.
'About the same price as a cinema ticket'
A separate study published last year based on an extrapolation from cocaine consumption in the canton of Vaud suggested around five tonnes of cocaine is consumed in Switzerland every year. That is 13.7kg a day.
Franck Zobel, the deputy director of Addiction Suisse – one of the organisations behind that study – noted that cocaine had fallen in price from 300 to 500 Swiss francs a gram in the 1990s to around 100 francs (€88). This had made it accessible in price to far more people.
“Cocaine isn't expensive. A line, whether it's 0.1 or 0.2 grams, comes in at about 15 to 20 Swiss francs, or about the same as a cinema ticket,” said Zobel.
The median wage in Zurich in 2016 was 7,820 francs, figures released late last year show.