Assessing the impacts of cytostatic drugs on freshwater biota


Cytostatic drugs are a class of pharmaceuticals used for cancer treatment, whose incidence has been increasing. These drugs are excreted mainly via urine subsequently reaching wastewater treatment plants (WWTPs). However, WWPTs do not always possess the proper means to effectively eliminate these drugs, meaning that they continuously enter the environment where they might reach surface and drinking waters. Since most anticancer drugs possess carcinogenic, teratogenic, genotoxic, and mutagenic properties, they might pose a potential risk to environmental and human health. In this context, the present work aimed at assessing the ecotoxicity of three cytostatic drugs (cyclophosphamide - CYP, mycophenolate mofetil - MMF, and mycophenolic acid - MPA) on freshwater species representing different trophic levels and functional groups: the microalga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, and the fish Danio rerio. The following endpoints were monitored: yield and population growth rates for the alga after an exposure of 72h; mortality for the rotifer after an exposure of 24h, and mortality, hatching rates, and morphological abnormalities, for the fish after an exposure of 96h. Regarding the assays with the microalga, it was not possible to determine the values for the endpoints evaluated for MMF and MPA. However, for CYP an EC50,72h of 593.0 mg L-1 for biomass inhibition and an EC50,72h of 1108 mg L-1 for growth inhibition were determined. For rotifers, LC50,24h values could not be computed for MMF and MPA, since at the highest tested concentration (40 and 30 mg L-1 , respectively - corresponding to the solubility limits of the compounds) no mortality was observed. Though an LC50,24h of 6397 mg L-1 for CYP was determined. Overall, MMF and MPA proved to be the most toxic compounds for zebrafish assays, with LC50,96h values of 0.046 and 1.410 mg L-1 , respectively, against an LC50,96h of 1306 mg L-1 for CYP. All cytostatics caused morphological abnormalities on zebrafish embryos, that mainly included oedemas and spinal cord malformations. Based on these results, the predicted no effects concentrations (PNEC) were derived for each compound to calculate the risk quotient (RQ), that relates toxicity to environmental exposure. The predicted or measured environmental concentrations in superficial waters were retrieved from the literature. In general, CYP revealed a low risk for freshwater biota (RQ = 0.003), while MMF and MPA presented RQ values above 1 (RQ = 3.0 and 4.1, respectively), indicating a high risk to freshwater organisms.


Bruna Ariana Ribeiro Monteiro


Isabel Maria Cunha Antunes Lopes, Cátia Alexandra Ribeiro Venâncio, Ana Catarina Almeida Sousa


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