http://www.emcdda.europa.eu/activities/wastewater-analysis
[Accessed: 02.08.2018]
In 2017 this Europe-wide study, which includes around 60 cities in total, revealed a picture of distinct geographical and temporal patterns of drug use across European cities. Twenty one cities have participated in at least five of the annual wastewater monitoring campaigns since 2011, which allows for seven-year time trend analysis of drug consumption based on wastewater testing. Following the success of this initial study, comparable studies were undertaken over the following four years, covering up to 19 European countries in 2017.