Occurrence and risk assessment of azole antifungal drugs in water and wastewater

Abstract

The occurrence of azole antifungals in the environment presents one of the emerging concerns due to their ecotoxicological threat as well as their potential contribution to the evolution of drug resistant fungi in the environment. In this study, the occurrence of eight commonly prescribed azole antifungal drugs was seasonally determined in influent and effluent water samples from three wastewater treatment plants and a drinking water treatment plant in South Africa. In addition, the risk quotient (RQ) method was employed to investigate the potential ecological and human health risks associated with their presence in the wastewater and/or drinking water. Clotrimazole, econazole, fluconazole, itraconazole, ketoconazole and miconazole were detected at least once in the water samples, while posaconazole and voriconazole were not detected in any of the samples for all seasons at which the samples were collected. Fluconazole was detected at higher frequency (about 96%) with a concentration up to 9959.0 ng L−1. Clotrimazole had the second highest frequency of detection (about 33%) with a concentration up to 143.3 ng L−1. Statistically significant temporal variation in clotrimazole (p < 0.05) and spatial variation in fluconazole (p < 0.05) were observed. In general, the preliminary ecological risk assessment based on risk quotient (RQ) calculation indicated that there is currently no high risk against aquatic organisms (Algae, Daphnia and Fish) related to the azole antifungals. Meanwhile, human health risk assessment demonstrated that fluconazole represented high risk in drinking water. Furthermore, risk estimates showed a potential for the detected concentrations of fluconazole and itraconazole in water samples to pose moderate to high risk for development of antifungal drug resistance. Some of the azole antifungal drugs are ubiquitous in the wastewater and future monitoring and validation studies should be conducted for those drugs that seem to pose human health and ecological risks.