Cocaine was the most commonly found drug and identified in every sample, as well as the anesthetic lidocaine. This is often used by dealers to bulk up the cocaine, according to the study authors. The scientists believe cocaine could have entered the water because of leakages or overflows from sewers.
Pesticides banned in the U.K. were also discovered, including fenuron. Ketamine, the animal tranquilizer which is used as a party drug, was also identified, as well as the opioid medication Tramadol and an antidepressant.