Recalcitrant pharmaceuticals in the aquatic environment: a comparative screening study of their occurrence, formation of phototransformation products and their in vitro toxicity

Abstract

Environmental context Many pharmaceuticals on the market have not undergone detailed evaluation for potential aquatic toxicity. We found that most tested pharmaceuticals were persistent, that phototransformation products were likely to be formed as a result of UV treatment of wastewater and that some transformation products were more toxic to bacteria than their precursor pharmaceutical compound. Thus UV treatment of wastewater does not seem appropriate to completely degrade or transform micropollutants into harmless compounds. Abstract Data allowing for a complete environmental risk assessment of pharmaceuticals and their photoderatives in the environment are still scarce. In the present study, in vitro toxicity and both bio- and photopersistence of various pharmaceuticals (aciclovir, allopurinol, cetirizine, cimetidine, fluconazole, hydrochlorothiazide, lisinopril, phenytoin, primidone, ranitidine, sotalol, sulpiride, tramadol and valsartane) as well as their phototransformation products were evaluated in order to fill data gaps and to help prioritise them for further testing. Twelve out of the fourteen compounds investigated were found to be neither readily nor inherently biodegradable in the Organisation of Economic Cooperation and Development-biodegradability tests. The study further demonstrates that the photo-induced transformation of the pharmaceuticals was faster upon irradiation with a Hg lamp (UV light) than with a Xe lamp emitting a spectrum that mimics sunlight. Comparing the non-irradiated with the respective irradiated solutions, a higher acute and chronic toxicity against bacteria was found for the irradiated solutions of seven compounds (cetirizine, cimetidine, hydrochlorothiazide, ranitidine, sulpiride, tramadol and valsartane). No cyto- and genotoxic effects were found in human cervical (HeLa) and liver (Hep-G2) cells for any of the investigated compounds or their phototransformation products. This comparative study documents that phototransformation products can arise as a result of UV treatment of wastewater containing these pharmaceuticals. It further demonstrates that some phototransformation products may have a higher environmental risk potential than the respective parent compounds because some phototransformation products exhibited a higher bacterial toxicity.