Effects of Ferrate(Vi) and Engineered Nanomaterials on Formation and Toxicity of Disinfection Byproducts in Synthetic Drinking Water Samples

Abstract

The role of different disinfectants [chlorination and ferrate(VI)] and microcontaminant (TiO2 and ZnO nanoparticles) regimens on the formation of nine disinfection byproducts (DBPs) in synthetic drinking water samples and their subsequent cytotoxic effects were assessed in depth. Specifically, water samples were chemically analyzed with gas chromatography/mass spectrometry (GC/MS), while their concentrated extracts underwent a battery of cellular assays (chronic cytotoxicity, viability, ROS generation, and autophagy) using one mammalian cell line (CHO-K1) and four human cell lines (CaCo-2, HEK293, GES-1, and FHC). Chemical analysis results indicated that that only waters disinfected with chlorine produced any concentration of the examined DBPs. Data from the chronic cytotoxicity assays showed that no sample extracts produced a significant change in cytotoxicity levels among CHO-K1 cells as compared to control samples at corresponding dilution levels. Among CaCo-2 cells, extracts from samples dosed with TiO2 and ZnO at the 0.8x dilution level showed significant increases in cytotoxicity compared to control samples at the corresponding dilution level. The cell viability and ROS assays showed that extracts from waters disinfected with ferrate(VI) were significantly less toxic to HEK293 cells compared to extracts from waters disinfected by chlorine, and produced a significant increase in ROS generation among GES-1 cells. Extracts from ZnO-dosed waters produced a significant increase in cell density and ROS generation among GES-1 and FHC cell lines, respectively. Lastly, it was shown that none of the extracts enhanced autophagic vacuole (AVO) accumulation among HEK293 cells, indicating low levels of cellular stress. Overall, these findings highlight various ways by which disinfectants and emerging contaminants such as NPs can influence the production and cytotoxic effects of DBP mixtures.