Analytic modeling and risk assessment of aerial transmission of SARS-CoV-2 virus through vaping expirations in shared micro-environments

Abstract

Background. E-cigarettes are an important harm reduction tool that provides smokers an alternative for nicotine consumption that is much safer than smoking. It is important to asses its safety under preventive and containment measures undertaken during the COVID-19 pandemic. Methods. We develop a theoretical risk model to assess the contagion risk by aerial transmission of the SARS-CoV-2 virus carried by e–cigarette aerosol (ECA) in shared indoor spaces, a home and restaurant scenarios, with natural and mechanical ventilation, with and without face masks. We also provide the theoretical elements to explain the visibility of exhaled ECA, which has important safety implications. Results. In a home or restaurant scenarios bystanders exposed to ECA expirations by an infectious vaper (and not wearing face masks) face a 1% increase of risk of contagion with respect to a “control case” scenario defined by exclusively rest breathing without vaping. This relative added risk becomes 5 - 17% for high intensity vaping, 44 - 176% and over 260% for speaking for various periods or coughing (all without vaping). Mechanical ventilation significantly decrease infective emissions but keep the same proportionality in risk percentages. Face masks of common usage effectively protect wearers from respiratory droplets and droplet nuclei possibly emitted by mask-less vapers as long as they avoid direct exposure to the visible exhaled vaping jet. Conclusions. Vaping emissions in shared indoor spaces involve only a minuscule added risk of COVID-19 contagion with respect to the already existing (unavoidable) risk from continuous breathing, significantly less than speaking or coughing. Protection of bystanders from this contagion does not require extra preventive measures besides those already recommended (1.5 meters separation and wearing face masks).

Aerial transmission of the SARS-CoV-2 virus through environmental e-cigarette aerosol: implications for public policies

“…This follows from its basic fluid dynamical characteristic: it is a "single-phase fluid flow" (SFF) system [52,53]. As a consequence, ECA droplets visually mark the actual expiratory flow associated with vaping exhalations (we discuss the optical properties that allow for its visualization in [22]).…”

“…Evidently, estimating the fluid flows that determine this exposure (and indirect exposure by dispersing droplets) in less idealized conditions requires a more realistic description using computational methods of fluid mechanics to incorporate effects of turbulence and thermal bouyance, as well as air currents from ventilation or motion. Rather, we examined global volume exposure in a separate article through a risk model not involving fluid dynamics described [22]. It is important to mention that this simplification of the dynamics is harder to justify for expiratory activities such as coughing or sneezing, as the latter involve larger ejection velocities and a much wider spectrum of droplet diameters that includes significant number of large supermicron droplets (significant numbers of droplets with diameters 1-10 µm and even >100 µm) whose effect on the dynamics of the carrier fluid cannot be neglected (these are strictly speaking multiphasic flows [52,60,87]).…”

“…As opposed to other respiratory activities (speaking, singing, coughing and sneezing), the involved respiratory flow of ECA is visible because the carried submicron droplets (ECA and respiratory) act effectively as visual tracers of the carrier fluid (see Section 2.3 and further details in [22]). Besides the evident psychological dimension of this flow visualization, there are safety implications: vapers and those surrounding them have a clear, instinctive and immediate delineation of the flow's horizontal distance reach and spreading direction along the exhaled jet.…”

“…Our results can provide useful guidelines to address the possible scope of vaping exhalations in assessing risks of contagion of infectious disease in shared indoor spaces. In other studies, we examined actual contagion risks and public policy implications (see [22,23]). Setting aside harms from environmental tobacco smoke unrelated to COVID-19, these results also apply to sharing an indoor space with a smoker.…”

“…Objective research on COVID-19 transmission through exhaled ECA can serve to guide evidence-based public policies to address public health concerns and risk management and minimization to address this phenomenon. Given the relevance of safety assessment in the context of the COVID-19 pandemic, we elaborated two articles related to (but fully independent from) the present article: one is a full risk analysis of vaping emissions in shared indoor spaces [22], while the other is a short article [23] discussing their public health and public policy implications, as well as reviewing available evidence on the relations between COVID-19 and smoking and vaping.…”