Effect of Puffing Behavior on Particle Size Distributions and Respiratory Depositions From Pod-Style Electronic Cigarette, or Vaping, Products

Abstract

The current fourth generation (“pod-style”) electronic cigarette, or vaping, products (EVPs) heat a liquid (“e-liquid”) contained in a reservoir (“pod”) using a battery-powered coil to deliver aerosol into the lungs. A portion of inhaled EVP aerosol is estimated as exhaled, which can present a potential secondhand exposure risk to bystanders. The effects of modifiable factors using either a prefilled disposable or refillable pod-style EVPs on aerosol particle size distribution (PSD) and its respiratory deposition are poorly understood. In this study, the influence of up to six puff profiles (55-, 65-, and 75-ml puff volumes per 6.5 and 7.5 W EVP power settings) on PSD was evaluated using a popular pod-style EVP (JUUL® brand) and a cascade impactor. JUUL® brand EVPs were used to aerosolize the manufacturers' e-liquids in their disposable pods and laboratory prepared “reference e-liquid” (without flavorings or nicotine) in refillable pods. The modeled dosimetry and calculated aerosol mass median aerodynamic diameters (MMADs) were used to estimate regional respiratory deposition. From these results, exhaled fraction of EVP aerosols was calculated as a surrogate of the secondhand exposure potential. Overall, MMADs did not differ among puff profiles, except for 55- and 75-ml volumes at 7.5 W (p < 0.05). For the reference e-liquid, MMADs ranged from 1.02 to 1.23 μm and dosimetry calculations predicted that particles would deposit in the head region (36–41%), in the trachea-bronchial (TB) region (19–21%), and in the pulmonary region (40–43%). For commercial JUUL® e-liquids, MMADs ranged from 0.92 to 1.67 μm and modeling predicted that more particles would deposit in the head region (35–52%) and in the pulmonary region (30–42%). Overall, 30–40% of the particles aerosolized by a pod-style EVP were estimated to deposit in the pulmonary region and 50–70% of the inhaled EVP aerosols could be exhaled; the latter could present an inhalational hazard to bystanders in indoor occupational settings. More research is needed to understand the influence of other modifiable factors on PSD and exposure potential.

Carbonyl Profiles of Electronic Nicotine Delivery System (ENDS) Aerosols Reflect Both the Chemical Composition and the Numbers of E-Liquid Ingredients–Focus on the In Vitro Toxicity of Strawberry and Vanilla Flavors

“…The physical properties of the ENDS aerosol will be influenced by multiple factors, including e-liquid composition, ENDS device settings, and vaping topography. Aerosol density and size distribution will mainly determine pulmonary deposition along the respiratory tract, in addition to the aerosol also being partly exhaled [ 38 , 39 ]. Thus, the pulmonary absorption of the carbonyls found in the ENDS aerosols will be influenced, among others, by the chemical properties of the specific carbonyl, for instance, acrolein, acetaldehyde, and formaldehyde are primarily upper respiratory tract irritants [ 40 ]; the lung morphology, the lung disease state, the breathing pattern, as well as the ENDS aerosol particulate phase [ 38 , 39 ].…”

“…Aerosol density and size distribution will mainly determine pulmonary deposition along the respiratory tract, in addition to the aerosol also being partly exhaled [ 38 , 39 ]. Thus, the pulmonary absorption of the carbonyls found in the ENDS aerosols will be influenced, among others, by the chemical properties of the specific carbonyl, for instance, acrolein, acetaldehyde, and formaldehyde are primarily upper respiratory tract irritants [ 40 ]; the lung morphology, the lung disease state, the breathing pattern, as well as the ENDS aerosol particulate phase [ 38 , 39 ]. Whether the adsorption of carbonyls onto the ENDS aerosol particulate phase increases the distribution of these compounds in the lower respiratory tract (bronchial and alveolar regions) is currently unknow, and thus merit future investigation.…”

Emerging ENDS products and challenges in tobacco control toxicity research

“…There are additional issues meriting further consideration that need to be addressed in the context of the emerging products described herein. For example, user behaviour and how it changes from device to device impacting toxicant exposure, factors modulating particle size distributions,66 interlaboratory reproducibility of findings, the correlation of laboratory studies to realistic usage, the significance of secondhand and thirdhand smoke and the development of standardised laboratory methods67 are relevant issues 68. As the FDA continues to aggressively regulate tobacco products through the PMTA pathway and approves new ENDS to enter the market, tobacco researchers need to be vigilant and conduct research that supports regulatory actions to protect public health.…”

Toxicological Assessment of Particulate and Metal Hazards Associated with Vaping Frequency and Device Age

“…As the popularity of the pod-type ENDS device gradually increases, safety concerns have escalated, warranting further examination of the hazards posed by pod-type ENDS-emitted aerosol exposures. Indeed, differential vaping patterns or levels of ENDS usage can contribute to exposure variances to various organic and inorganic hazards, including heavy metals [ 7 , 8 , 9 ]. Several metals have been detected in pod-type ENDS aerosols, such as chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), manganese (Mn), and lead (Pb) [ 10 , 11 ].…”

“…Increased metal exposure is a critical risk factor for various respiratory diseases, such as respiratory inflammation, asthma, COPD, and respiratory cancer [ 14 , 15 , 16 ]. However, there is a lack of evidence to determine the level of metal exposure from the pod-type ENDS aerosol because of the inconsistency of aerosol generation parameters, type of device, and e-liquid selection in recent studies [ 7 , 17 , 18 ]. Therefore, a detailed evaluation of the level of metal exposure derived from pod-type ENDS usage is needed to determine the potential adverse effects on respiratory health.…”