Real-Time Measurements of Botanical Disinfectant Emissions, Transformations, and Multiphase Inhalation Exposures in Buildings

Abstract

Thymol-based botanical disinfectants have emerged as natural alternatives to traditional chemical disinfectants given their effectiveness as antimicrobial pesticides and ability to inactivate SARS-CoV-2. This study investigates the impact of botanical disinfectants on indoor air chemistry and human exposure. Controlled surface disinfection experiments were conducted in a mechanically ventilated zero-energy tiny house laboratory. Volatile organic compounds (VOCs) and aerosol size distributions were measured in real-time (1 Hz) with a proton transfer reaction time-of-flight mass spectrometer and a high-resolution electrical low-pressure impactor, respectively. Botanical disinfectant spray and wipe products drove sudden changes in the chemical composition of indoor air. Mixing ratios of monoterpenes (C10H16) and monoterpenoids (C10H14O, C10H16O, C10H18O, and C10H20O) increased suddenly during the disinfection events (10-1 to 102 ppb) and exhibited volatility-dependent temporal emission profiles. VOC emission factors ranged from 100 to 104 μg g-1, and thymol intake fractions ranged from 6 to 7 × 103 ppm. Rapid new particle formation events were observed due to ozonolysis of monoterpenes and monoterpenoids, increasing sub-100 nm particle number concentrations by 104 to 105 cm-3. Botanical disinfectant sprays initiated multiphase inhalation exposure to VOCs, secondary organic aerosol, and sub-10 μm droplets, with large deposited doses in each respiratory tract region associated with the latter two. ©