Pharmaceuticals in the aquatic environment may be decomposed by abiotic and biotic factors. Photodegradation is the most investigated abiotic process, as it occurs in the natural environment and may be applied in wastewater treatment technology. Although pharmaceuticals are detected in effluents and surface water in a mixture, the photodegradation process is mainly evaluated with single compounds. The photodegradation of fluoxetine (FLU) and fluvoxamine (FLX) in the presence of diclofenac (DCF) and triclosan (TCS) was investigated with HPLC and bioassay. FLU did not degrade under UV-Vis irradiation in SunTest CPS+ either with or without the tested additives, although small amounts of desmethyl fluoxetine and 4-(trifluoromethyl)phenol were formed. In contrast, during irradiation, FLX isomerized to cis-FLX. This process was enhanced by DCF and TCS, but to a lesser degree than by humic acids. Thus, the presence and composition of the matrix should be considered in the environmental risk assessment of pharmaceuticals. As the toxicity of the tested solutions depended only on the concentration of the tested drugs, it was suggested that the biological activity of the photodegradation products was lower than that of the parent compounds.
Keywords: Acute toxicity; Diclofenac; Humic acids; Isomerization; Spirotox; Triclosan.