E-Cigarette Airflow Rate Modulates Toxicant Profiles and Can Lead to Concerning Levels of Solvent Consumption

Abstract

Electronic cigarettes enabling enhanced airflow have grown in popularity in recent years. The objective of this study is to show that flow rates modulate the levels of specific aerosol toxicants produced in electronic cigarettes. Flow rates used in various laboratory investigations involving e-cigarettes have varied widely to date, and can thus promote interlaboratory variability in aerosol product profiles. The thermal decomposition of hydroxyacetone and glycolaldehyde is less favorable at lower temperatures, supporting the observations of these products at higher flow rates/lower heating coil temperatures. Higher temperatures promote the formation of acetaldehyde from hydroxyacetone and formaldehyde from both hydroxyacetone and glycolaldehyde. A separate finding is that greater airflow can also expose users to concerning levels of e-liquid solvents. Under the modest conditions studied, propylene glycol aerosol levels are found at above the acceptable inhalation levels defined by NASA, and in range of the generally recognized as safe levels for daily ingestion.

Carbonyls and Carbon Monoxide Emissions from Electronic Cigarettes Affected by Device Type and Use Patterns

“…Our results with the top-coil e-cigarette were consistent with previous reports. Previous studies showed decreased total particle mass concentration [36] and carbonyl emissions [17] at higher flow rates using cig-a-like, top-coil, bottom-coil, and JUUL devices. Faster air flows through the heating chamber were shown to decrease coil temperature [16], leading to lower aerosol and carbonyl emissions.…”

“…yields were shown to increase with puff duration, while puff flow rate had no effect [14]. E-liquid consumption and emissions of some carbonyls were observed to depend on puff flow rate [17].…”

“…yields were shown to increase with puff duration, while puff flow rate had no effect [14]. E-liquid consumption and emissions of some carbonyls were observed to depend on puff flow rate [17].Differences in device types and testing protocols (e.g., e-cigarette power, e-liquid composition, and puff parameters) used in previous studies [4,5,8] make it difficult to inter-compare results and draw conclusions about the relative safety of particular e-cigarette devices and e-liquids. If puff topography has a strong effect on e-cigarette emissions, translating results of laboratory studies performed using fixed puff parameters to user exposure becomes problematic because puff topography among e-cigarette users varies widely.…”

“…These findings demonstrate that the effect of vaping topography should be carefully considered to test e-cigarette chemical emissions. Previous reports used puff durations of 1 to 2 sec [6,37-40] and vaping flow rates of 10-16.7 mL/sec [4,5,8,17,41,42] to measure the potentially harmful emissions from e-cigarettes. Depending on the e-cigarette construction, levels of potentially harmful compounds reported in the previous studies can cause the over-or under-estimation of the actual exposures since e-cigarette users showed much longer puff durations (3.5 to 4 sec) and higher puff flow rates (24-38 mL/sec) [31,32].…”

Generation of Electronic Cigarette Aerosol by a Third-Generation Machine-Vaping Device: Application to Toxicological Studies

“…It is well established that e-cig users try to avoid dry puffs, which occur in dry burn conditions. This vaping condition is related to the formation of high levels of aldehydes, including formaldehyde, a known carcinogen and respiratory toxicant 13,30 . Therefore, ensuring that this condition is avoided during the exposures is crucial.…”