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The current work assessed the degradation degree and the degradation products derived from norfloxacin (NOR) and gentamicin (GEN) using iodosylbenzene and iodobenzene diacetate, in the presence of manganese porphyrin as catalysts. Better results for NOR degradation (> 80%) were obtained when more hydrophobic porphyrins were employed. ß-brominated manganese porphyrins showed a lower GEN degradation (~ 25%) than the non-brominated ones (~ 35%), probably due to their steric hindrance. In any case, complete mineralization was achieved neither for NOR nor for GEN, and the assignment of the generated products, complemented by the study of their toxicity, was an important step performed. From the obtained results, no correlation was found between the number of identified products and the reported toxicity value (rSpearman,NOR = 0.006; p value = 0.986 and rSpearman,GEN = - 0,198; p value = 0.583), which reinforces the idea of synergism and antagonistic phenomena. The higher degradation degree could have led to products of lower steric hindrance and easier penetration into the A. fischeri cells, which subsequently led to an increase in toxicity for these experiments. In most cases, the products presented higher toxicity than the original compound, which raises a concern about their occurrence in environmental matrices.

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In the present study, the simultaneous adsorption degradation of norfloxacin (NOR) by graphene oxide from aqueous matrix was verified. Graphene oxide (GO, ~ 8 layers) was prepared using modified Hummers method through the oxidation/exfoliation of expanded graphite. Spectroscopic techniques confirmed the NOR adsorption onto GO surface and the partial antibiotic degradation promoted by hydroxyl radicals derived from GO. Furthermore, the mass spectra after the adsorption-degradation processes showed NOR degradation intermediates that was compared and confirmed by other studies. The nanomaterial showed a removal capacity of 374.9 ± 29.8 mg g-1, observing greater contribution from the NOR in the zwitterionic form and removals up to 94.8%. The intraparticle diffusion process, assessed by Boyd's model and Fick's law, presented a greater contribution in the removal process, reaching the equilibrium 30 min after the beginning. In addition, the temperature increase would disadvantage the process, which was considered thermodynamically viable throughout the evaluated temperature range. Finally, the process was scaled-up in a single stage batch adsorber considering a NOR removal efficiency of 95%. This resulted in mass requirement of 63.6 g of GO in order to treat 0.5 m3 of contaminated water. In general, the simultaneous adsorption-degradation process was considered innovative and promising in pharmaceutical compounds remediation.

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High consumption of drugs, combined with their presence in the environment, raises concerns about its consequences. Even though researches are often engaged in analyzing substances separately, that is not the environmental reality. Therefore, the aim of this study was to investigate the acute toxicity of the pharmaceuticals simvastatin, metformin, omeprazole and diazepam, and all possible mixtures between them, to the organism Aliivibrio fischeri, verifying possible synergistic or antagonistic effects and assessing byproducts formation. In terms of individual toxicity, omeprazole is the most toxic of the active ingredients, followed by simvastatin, diazepam and, finally, metformin. When the toxicity of mixtures was tested, synergism, antagonism and hormesis were perceived, most probably generated due to byproducts formation. Moreover, it was observed that even when compounds are at concentrations below the non-observed effect concentration (NOEC), there may be toxicity to the mixture. Hence, this work points to the urgent need for more studies involving mixtures, since chemicals are subject to interactions and modifications, can mix, and potentiate or nullify the toxic effect of each other.

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RESUMO Os antibióticos como o norfloxacino constituem os fármacos mais utilizados na Medicina, com consumos expressivos no mundo todo. Por ser quimicamente estável, após sua administração a maior parte do fármaco é excretada de forma inalterada e, geralmente, é removida apenas parcialmente nas estações de tratamento de esgoto (ETEs). Assim, o presente trabalho buscou avaliar a eficiência dos processos biológicos na remediação de norfloxacino investigando os mecanismos de remoção envolvidos. O objetivo foi verificar a biodegradabilidade do fármaco e sua toxicidade. Para realização dos ensaios de biodegradabilidade, coletaram-se lodos na ETE Arrudas (Sabará, Minas Gerais) dos processos de tratamento com lodos ativados, reatores upflow anaerobic sludge blanket (UASB) e biodigestor anaeróbio. Reatores em escala de bancada foram montados com lodo aclimatado e não aclimatado. Amostras tiveram a biodegradabilidade acompanhada por meio da determinação do carbono orgânico total e da absortividade molar do norfloxacino por espectrofotometria de UV/Vis. Determinou-se a toxicidade por intermédio de ensaios com a bactéria Aliivibrio fischeri. Entre as biomassas utilizadas, a mais eficiente na remoção do norfloxacino foi advinda dos reatores UASB (23%), seguida do biodigestor anaeróbio (18%) e, então, dos lodos ativados (13%). Quanto à ecotoxicidade, a degradação anaeróbia promoveu a eliminação da toxicidade do antibiótico, enquanto com relação à degradação aeróbia os efluentes gerados permanecem tóxicos.

ABSTRACT Antibiotics, such as norfloxacin, are the most widely used drugs in medicine, with significant consumption in the world. By being chemically stable, most of the drug is excreted unchanged after administration, and is generally only partially removed in the sewage treatment plants (STPs). Thus, the efficiency of biological processes in the remediation of norfloxacin was investigated by the present work, verifying the removal mechanisms involved. Its objective was to verify the drug's biodegradability and toxicity. In order to perform biodegradability tests, sludges were collected in Arrudas STP (Sabara, Minas Gerais) from the treatment processes with activated sludge, upflow anaerobic sludge blanket (UASB) reactors and anaerobic biodigester. Bench-scale reactors were assembled with acclimatized and non-acclimatized sludge. Samples had their biodegradability monitored by determination of total organic carbon and norfloxacin molar absorptivity by UV/Vis spectrophotometry. The toxicity was determined by tests with Aliivibrio fischeri. Among the used biomass, UASB reactors was the most efficient in removing norfloxacin (23%), followed by anaerobic biodigester (18%), and activated sludge (13%). Regarding ecotoxicity, the anaerobic degradation promoted the elimination of antibiotic toxicity, while with aerobic degradation, the effluents generated remained toxic.

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Considerable quantities of different classes of drugs are consumed annually worldwide. These drugs, once disposed, often remain stable, even after conventional or advanced treatments. Although there have been a number of studies on the potential harm caused by drugs when released into the environment, few studies have investigated the toxicity of pharmaceutical excipients. In the present study, the acute toxicity of 30 drugs was tested to Aliivibrio fischeri. Ten different active ingredients were investigated, each in three distinct formulations: generic, similar and reference (brand drug). The aim of the study was to evaluate the harmful potential of drugs frequently sold in drugstores and to assess the contribution of excipients towards the observed acute toxicity. Within the 10 drugs evaluated, only one, dexchlorpheniramine maleate, was not toxic in any formulation. The toxicities of the three formulations were often different, even though the active ingredient has been the same. For some drugs, such as diazepam, glibenclamide, metformin, nimesulide, hydrochlorothiazide and simvastatin, only one or two of the three formulations tested were toxic to A. fischeri. These results highlight the toxicological potential of drug excipients, but not exclusively the toxicity of the active ingredients.

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