Efficient degradation of dye-based environmental pollutants and industrially contaminated wastewater remains a formidable challenge. The photo-assisted catalytic degradation of anthraquinone Reactive Blue 19 (RB-19) dye was investigated by varying the operational parameters such as reaction time, catalyst (titanium dioxide, TiO2) loading, initial dye concentration, and hydrogen peroxide (H2O2) concentration. Pronounced dye degradation reaction was achieved at 1.0 g/L of TiO2 after 180 min of degradation period with 0.3 x 10(-3) mol/L of H2O2. UPLC/MS analysis scrutinized the intermediates and based on the electrospray ionization mass spectrometry (ESI-MS) analysis. A mechanistic degradation pathway has also been proposed. The complete degradation of RB-19 was confirmed by total organic carbon (TOC) and chemical oxygen demand (COD) analysis. Toxicity profile of untreated and photo catalytically-degraded dye was evaluated using three types of human cell lines, i.e., MCP 7, L 929 and HeLa cells. It was observed that transformed byproducts of RB-19 were less toxic than the original dye molecule. In conclusion, the UV/TiO2 mediated process can promisingly degrade RB-19 dye under optimized conditions. It is evident from the data obtained that the newly developed UV/TiO2-assisted mechanism could practically be used for the degradation of industrial dyes and/or dyes based waste effluents. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.