High levels of perfluorochemicals in Taiwan's wastewater treatment plants and downstream rivers pose great risk to local aquatic ecosystems.

We studied perfluorochemicals (PFCs) in the influents and effluents of two municipal wastewater treatment plants (MWWTPs) and in the effluents of an industrial wastewater treatment plant (IWWTP). The impact of IWWTP effluents on the receiving rivers (the Nanmen and Keya Rivers) was evaluated by measuring PFC levels in the surface waters of both rivers and the sediments of the Nanmen River. Perfluorooctane sulfonate (PFOS) (293 ng L(-1)) and perfluorohexanoic acid (406 ng L(-1)) were identified as the compounds present in greatest concentrations in the influents and effluents of both MWWTPs, which are largely influenced by domestic sources. High concentrations of PFCs (up to 1,0000 ng L(-1)) were found in IWWTP effluents and receiving rivers, with more perfluoroalkyl sulfonates (PFASs) found than perfluoroalkylcarboxylic acids (PFCAs). This study confirms the IWWTP as the point source of the persistent contamination of the Nanmen and Keya Rivers. Sediments of the Nanmen River were also impacted by IWWTP discharges, with high concentrations of PFOS (up to 9,0000 ng kg(-1)). PFCAs with longer carbon chains exhibited preferred partitioning onto the sediments. The occurrence of higher PFC concentrations in Taiwan's aquatic media compared to other countries stresses the necessity for PFC risk management. Accordingly, a preliminary risk assessment was performed using the predicted no-effect concentration (PNEC) and indicative maximum permissible concentration (iMPC). The likelihood of ecological risk due to PFOS was plausible at a risk quotient of 1.21, as calculated using iMPC. Given our findings of high environmental PFC concentrations, rapid and meaningful steps should be taken to reduce entry of PFCs into Taiwan's aquatic environment.