Ecotoxicity of Fluoxetine Hydrochloride on Aquatic Organisms from Different Taxonomic Groups

Fluoxetine (FLX) is an antidepressant pertaining to the class of selective serotonin reuptake inhibitors. FLX use has increased in the past decade culminating in its discharge to surface waters. Owing to the limited knowledge about the toxicity of this drug to aquatic biota, this study aimed to evaluate potential toxic effects of FLX on green algae Chlorella vulgaris, cyanobacteria Microcystis novacekii, marine bacteria Aliivibrio fischeri, and mollusk Biomphalaria glabrata. Assays with C. vulgaris and M. novacekii followed OECD protocol 201 (2011) and NBR 12648 standard (2018), respectively. The assay with A. fischeri was carried out according to ISO/OIN 11348-3 (2007). Toxicity assays with B. glabrata were performed by exposing these organisms (newborn and embryos) in 24-well culture plates for 3 and 7 days, respectively. All test-organisms were exposed to at least 6 different concentrations of FLX, ranging from 0.1 to 20,000 µg/L, in triplicates. Effect concentrations (EC50) obtained for these assays showed that FLX is more toxic to M. novacekii (10.71 ± 1.67 µg/L), followed by C. vulgaris (13.01 ± 2.01 µg/L) and A. fischeri (3140 ± 1050 µg/L). Regarding B. glabrata, the 50% lethal concentration for newborns was 1770 ± 260 µg/L, while for embryos it was equivalent to 34.98 ± 3.66 µg/L. Considering recent reports of FLX occurrence in environmental matrices in the µg/L range, results reported in this study and the toxicity classification criteria by the Globally Harmonized System, FLX poses high risk to aquatic environments, its biodiversity, and ecosystems. Therefore, measures must be taken to prevent the disposal of waste containing FLX into the environment, especially in region lacking basic sanitation infrastructure.