Multiphase Oxidation of Benzotriazole Ultraviolet Stabilizers UV328 and UVP

YAO YAN HUANG, Jonathan Abbatt, Xinke Wang, Amila De Silva, Cassandra Brinovcar, Linna Xie, University of Toronto

     Abstract Number: 484
     Working Group: Chemicals of Emerging Concern in Indoor and Outdoor Aerosol: Sources, Vectors, Reactivity, and Impacts

Abstract
Benzotriazole ultraviolet stabilizers (BZT-UVs) are a class of chemicals used to prevent the degradation of materials from ultraviolet (UV) radiation that are added to various consumer and industrial products such as paints, polymers and food packaging, and textiles. They are highly recalcitrant with a growing concern as an environmental contaminant, being observed in water bodies, sediment, and in airborne dust and aerosols. Their reactivity and degradation pathways in the environment are still largely unknown. Their presence in airborne dust, aerosols, and consumer products suggests a potential for exposure and transformations in everyday environments. The multiphase reaction of two BZT-UVs (UV-328, UV-P) with gas phase oxidants (·OH, O3) was conducted in a flow cell reactor. O3 experiments were up to 24h at different mixing ratios (250 ppb, 1 ppm, 7 ppm) and ·OH for up to 3 days (~1-2 x 107 molecules/cm3). Parent compound decay was monitored off-line by liquid chromatography tandem mass spectrometry (LC-MS/MS). Molecular formulae of suspected products were identified by liquid chromatography high resolution mass spectrometry (LC-HRMS) using both a targeted and non-targeted approach. Both UV-328 and UV-P were found to be recalcitrant to multiphase O3 oxidation and more reactive with ·OH. Nevertheless, O3 reactions at 7 ppm for 24h produced highly oxygenated products up to +4O from the parent. ·OH reactions produced products up to +2O from the parent in the 3 day time frame. As well, benzotriazole (C6H5N3) was identified as a major product for both oxidants from both UV-328 and UV-P. Some structures and reaction pathways are proposed based on molecular formula and MS2 fragments. UV-328 reactivity and products in a real indoor environment (light conditions next to a window and in a dark office setting) are also compared to behavior in the flow cell. This work investigates the atmospheric fate of BZT-UVs and identifies benzotriazole as atmospheric transformation product for BZT-UVs. The potential transformation products can be used for future screening in aerosols and dust, and for toxicological studies.