Water contamination by pharmaceuticals is a global concern due to their potential negative effects on aquatic ecosystems and human health. This study examined the presence of three repositioned drugs used for COVID-19 treatment: azithromycin (AZI), ivermectin (IVE) and hydroxychloroquine (HCQ) in water samples collected from three urban rivers in Curitiba, Brazil, during August and September 2020. We conducted a risk assessment and evaluated the individual (0, 2, 4, 20, 100 and 200 μg.L−1) and combined (mix of the drugs at 2 μg.L−1) effects of the antimicrobials on the cyanobacterium Synechococcus elongatus and microalga Chlorella vulgaris. The liquid chromatography coupled to mass spectrometry results showed that AZI and IVE were present in all collected samples, while HCQ occurred in 78 % of them. In all the studied sites, the concentrations found of AZI (up to 2.85 μg.L−1) and HCQ (up to 2.97 μg.L−1) represent environmental risks for the studied species, while IVE (up to 3.2 μg.L−1) was a risk only for Chlorella vulgaris. The hazard quotients (HQ) indices demonstrated that the microalga was less sensitive to the drugs than the cyanobacteria. HCQ and IVE had the highest values of HQ for the cyanobacteria and microalga, respectively, being the most toxic drugs for each species. Interactive effects of drugs were observed on growth, photosynthesis and antioxidant activity. The treatment with AZI + IVE resulted in cyanobacteria death, while exposure to the mixture of all three drugs led to decreased growth and photosynthesis in the cells.. On the other hand, no effect on growth was observed for C. vulgaris, although photosynthesis has been negatively affected by all treatments. The use of AZI, IVE and HCQ for COVID-19 treatment may have generated surface water contamination, which could increased their potential ecotoxicological effects. This raises the need to further investigation into their effects on aquatic ecosystems.

Fuente: Science of The Total Environment
Available online 24 May 2023