Assessment of illicit drugs in wastewater and estimation of drugs of abuse in Adana Province, Turkey.

•The first wastewater-based epidemiology in Turkey was implemented in Adana Province.•The most commonly detected drugs were MDMA, MDA, morphine, and codeine.•The highest illicit drug consumption rate was obtained for marijuana.•The consumption rate for party drugs (cocaine and ecstasy) was higher in weekends.•Cocaine consumption was higher in Seyhan, whereas marijuana consumption was higher in Yuregir.