Analysing wastewater to estimate fentanyl and tramadol use in major Chinese cities.

The misuse of fentanyl and more recently tramadol in the population has caused an opioid crisis in several countries and drawn much public attention worldwide. However, there is a gap of information on the potential misuse of fentanyl and tramadol in China. This study aims to fill this gap by analysing fentanyl and tramadol in wastewater of major cities across China to estimate their use. Wastewater samples were collected from 30 cities located across all seven geographic regions of China, from 2016 to 2019. Fentanyl was detected in only a few samples, suggesting a low prevalence of this potent opioid drug in China. Meanwhile, tramadol was found in most samples with concentrations ranging up to 186 ng/L. The per capita daily consumption of tramadol estimated from wastewater across China ranged from 6 mg/d/1000 in. to 213 mg/d/1000 inh. The consumption of tramadol seems to be similar among all the days of the week. Tramadol use is overall higher in Northeast China than in other regions, which is different from heroin, another popular opioid in China. Temporally, there is a significant decrease in tramadol use in major cities of China from 2016 to 2019. The results of our study suggested that tramadol use in China was predominantly from pharmaceutical prescription and not as prevalent as in other countries.