Anticancer Drugs Gemcitabine, Letrozole, and Tamoxifen in Municipal Wastewater and Their Photodegradation in Laboratory-Scale UV Experiments

The occurrence of three anticancer drugs (gemcitabine, letrozole, tamoxifen) was studied in wastewater samples from two local wastewater treatment plants (WWTPs) in Finland. Studied pharmaceuticals were selected, as anticancer drugs are potential to cause adverse effects on organisms even at low concentrations, but they are seldom included in the analysis of emerging contaminants. The concentration of anticancer drugs was determined by liquid chromatography-triple quadrupole mass spectrometer (LC–MS/MS). Tamoxifen and letrozole were detected from influent samples ranging from 0.5 to 5.0 ng/L, respectively. Letrozole was detected from effluent samples at a concentration up to 2.4 ng/L. Letrozole has been detected in wastewater effluent only once before, at a lower concentration of 0.28 ng/L. Gemcitabine was not detected in any of the samples. UV irradiation is used in many wastewater treatment plants to disinfect the effluent. Such tertiary treatment might degrade also these potentially harmful drugs and, therefore, photodegradation of the chosen pharmaceuticals was studied in laboratory-scale experiments. Tamoxifen showed high degradation rates, 94% in spiked wastewater with UV fluence 4830 mJ/cm and 98% in pure water with UV fluence 2520 mJ/cm, respectively. Letrozole showed the lowest degradation rates of 24% in wastewater and 34% in pure water, respectively. The degradation rate at the fluence level typical for UV disinfection stage of wastewater treatment plants was 37% for tamoxifen but only 5% for letrozole. To the best of the authors’ knowledge, this is the first report to show the effectiveness of UV irradiation to degrade letrozole.