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Quantifying the Effect of Indoor Conditions on Exposure to Gas-Phase Bleach Products
PASCALE LAKEY, Youngbo Won, Atila Novoselac, Donghyun Rim, Manabu Shiraiwa, University of California, Irvine
Abstract Number: 242
Working Group: Indoor Aerosols
Abstract
Application of bleach indoors has previously been associated with many different health effects and respiratory symptoms such as wheezing, shortness of breath and non-allergenic asthma [1]. Bleach leads to the formation of many harmful and irritating products in the gas-phase including hypochlorous acid, chlorine gas, chloramines, nitryl chloride, and OH and Cl radicals [2]. A kinetic model was previously developed to investigate the reactions controlling gas-phase bleach products measured during the House Observations of Microbial and Environmental Chemistry (HOMEChem) campaign [2]. The model included reactions in the bleach and gas-phase as well as uptake to particles and wall losses. Air exchange was included in the model as well as mass transport through a boundary layer next to the bleach. Parameters in the model, such as rate coefficients were based on literature values whenever possible. In the current study, this kinetic model was used to investigate the impact of changing indoor conditions on gas-phase bleach product concentrations and to provide parameters to a computational fluid dynamics (CFD) model which can investigate spatial heterogeneity indoors.
Simulations suggested that air-exchange must be high (> 5 h-1) in order to compete with other indoor loss pathways and reduce concentrations of bleach products. Acidification of bleach on surfaces increases HOCl, Cl2 and ClNO2 significantly down to pH 7.5, but does not impact the total concentration of chloramines. Additionally, increasing the surface area or decreasing the room volume by a certain factor would increase concentrations of HOCl, Cl2 and ClNO2 by the same factor. Results from the CFD simulations suggested that there was a large spatial heterogeneity for many of the gas-phase bleach products.
References
[1] B. Matulonga et al., Resp. med. 117, 264-271 (2016).
[2] J. M. Mattila et al., Environ. Sci. Technol., 54, 1730–1739 (2020).