International Laboratory for Air Quality and Health (ILAQH), School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Australia.
J R Soc Interface. 2021 May;18(178):20210209. doi: 10.1098/rsif.2021.0209. Epub 2021 May 5.
The airborne dynamics of respiratory droplets, and the transmission routes of pathogens embedded within them, are governed primarily by the diameter of the particles. These particles are composed of the fluid which lines the respiratory tract, and is primarily mucins and salts, which will interact with the atmosphere and evaporate to reach an equilibrium diameter. Measuring organic volume fraction (OVF) of cough aerosol has proved challenging due to large variability and low material volume produced after coughing. Here, the diametric hygroscopic growth factors (GF) of the cough aerosol produced by healthy participants were measured using a rotating aerosol suspension chamber and a humidification tandem differential mobility analyser. Using hygroscopicity models, it was estimated that the average OVF in the evaporated cough aerosol was 0.88 ± 0.07 and the average GF at 90% relative humidity (RH) was 1.31 ± 0.03. To reach equilibrium in dry air the droplets will reduce in diameter by a factor of approximately 2.8 with an evaporation factor of 0.36 ± 0.05. Hysteresis was observed in cough aerosol at RH = ∼35% and RH = ∼65% for efflorescence and deliquescence, respectively, and may depend on the OVF. The same behaviour and GF were observed in nebulized bovine bronchoalveolar lavage fluid.
呼吸道飞沫的气载动力学以及其中嵌入的病原体传播途径主要受颗粒直径的控制。这些颗粒由呼吸道衬里的液体组成，主要是粘蛋白和盐，它们将与大气相互作用并蒸发以达到平衡直径。由于咳嗽后产生的大量可变性和低物质体积，测量咳嗽气溶胶的有机体积分数（OVF）一直具有挑战性。在这里，使用旋转气溶胶悬浮室和加湿串联差分迁移率分析仪测量了健康参与者产生的咳嗽气溶胶的直径吸湿增长因子（GF）。使用吸湿性模型估计，蒸发的咳嗽气溶胶中的平均 OVF 为 0.88±0.07，90%相对湿度（RH）下的平均 GF 为 1.31±0.03。为了在干燥空气中达到平衡，液滴的直径将减小约 2.8 倍，蒸发因子为 0.36±0.05。在 RH = ∼35%和 RH = ∼65%时分别观察到咳嗽气溶胶的滞后现象，分别为结晶和潮解，这可能取决于 OVF。在雾化的牛支气管肺泡灌洗液中观察到相同的行为和 GF。
