Mass balance of anti-influenza drugs discharged into the Yodo River system, Japan, under an influenza outbreak

- Mass balance of OS, OC, ZAN, and AMN in the Yodo River system was firstly clarified.
- Anti-influenza drugs in the Yodo River system were mainly loaded at STP effluents.
- The constant ratio of OS to OC showed their environmentally stably.
- Removal of anti-influenza drugs at STPs with sewerage systems is prerequisite.