Degradation of the antifungal pharmaceutical clotrimazole by UVC and vacuum-UV irradiation: Kinetics, transformation products and attenuation of toxicity

Nuno P.F Gonçalves,Oihane Del Puerto,Claudio Medana,Paola Calza,Peter Roslev

doi:10.1016/j.jece.2021.106275

Nuno P.F Gonçalves, Oihane Del Puerto + Show 3 more

Open Access

https://doi.org/10.1016/j.jece.2021.106275

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Abstract

Azole fungicides are frequently detected as water contaminants due to extensive societal use, and these broad-spectrum antifungal chemicals can cause harmful effects in non-target organisms. Vacuum ultraviolet (VUV) treatment is an efficient and green technology that produces hydroxyl radical to remove contaminants from water. This study investigated the potential of UVC (254 nm) and combined VUV/UVC (185/254 nm) treatment to remove the widely used antifungal compound clotrimazole from water. Degradation kinetics, degradation mechanisms, and toxicity mitigation were investigated using a VUV photoreactor. Toxicity of clotrimazole to aquatic organisms before and after UV treatment were investigated using the luminescent bacterium Aliivibrio fischeri, the bioluminescent yeast Saccharomyces cerevisiae BLYR, the filamentous fungus Fusarium graminearum, the freshwater microalga Raphidocelis subcapitata, and the crustacean Daphnia magna. VUV irradiation efficiently degraded the persistent pollutant clotrimazole at elevated concentrations (mg/L) and at environmental concentrations (µg/L) with > 50% abatement in 1 min and > 95% removal within 32 min. VUV photolysis produced 8 transformation products manly resulting from drug hydroxylation in the phenyl ring and/or imidazole group followed by ring opening or loss of the imidazole moiety. Substantial decrease in aquatic toxicity was observed after UV treatment suggesting that VUV irradiation of aqueous clotrimazole generated less-toxic transformation products.

Highlights

Azole fungicides are active ingredients used in pharmaceutical and personal care products for the treatment of human mycosis and are used in agriculture against fungal infections
We examined the effect of UVC and VUV irradiation of clotrimazole in water on degradation, occurrence of transformation products and changes in ecotoxicity
The use of the VUV processes with radiation bellow 200 nm promotes the photolysis of water allowing the in situ generation of reactive oxygen species such as hydroxyl radical (OH), superoxide anion (O2-) and hydrogen peroxide (H2O2) [24,26,27], that can lead the indirect photolysis of organic pollutants

Summary

Introduction

Azole fungicides are active ingredients used in pharmaceutical and personal care products for the treatment of human mycosis and are used in agriculture against fungal infections. Released via urban and hospital wastewater, surface runoff and pesticide application, sig nificant amounts of azoles have been emitted to aquatic environments. Azoles fungicides are usually moderately lipophilic and relatively persistent with typical half-lives of weeks to months, and are only partially removed in traditional wastewater treatment plants (WWTPs) [3]. WWTPs act as a constant source of azoles into the natural environment where they may have adverse effects on non-target organisms. Azole fungicides may pose a risk to other non-target organisms including aquatic macrophytes and algae [1,7,15,16]. There is evidence of azoles involvement in development of anti fungal resistance with potential impact on human health [17,18]

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