Aerosol droplet-size distribution and airborne nicotine portioning in particle and gas phases emitted by electronic cigarettes

Abstract

The reliable characterization of particle size distribution and nicotine delivery emitted by electronic cigarettes (ECs) is a critical issue in their design. Indeed, a better understanding of how nicotine is delivered as an aerosol with an appropriate aerodynamic size is a necessary step toward obtaining a well-designed nicotine transfer from the respiratory tract to the bloodstream to better satisfy craving and improve smoking cessation rates. To study these two factors, recent models of EC devices and a dedicated vaping machine were used to generate aerosols under various experimental conditions, including varying the EC power level using two different types of atomizers. The aerodynamic particle sizing of the resulting aerosol was performed using a cascade impactor. The nicotine concentration in the refill liquid and the aerosol droplet was quantified by liquid chromatography coupled with a photodiode array. The vaporization process and the physical and chemical properties of the EC aerosol were very similar at 15 watts (W) and 25 W using the low-power atomizer but quite distinct at 50 W using the high-power atomizer, as follows: (1) the mass median aerodynamic diameters ranged from 1.06 to 1.19 µm (µm) for low power and from 2.33 to 2.46 µm for high power; (2) the nicotine concentrations of aerosol droplets were approximately 11 mg per milliliter (mg/mL) for low power and 17 mg/mL for high power; and (3) the aerosol droplet particle phase of the total nicotine mass emitted by EC was 60% for low power and 95% for high power. The results indicate that varying the correlated factors (1) the power level and (2) the design of atomizer (including the type of coil and the value of resistance used) affects the particle-size distribution and the airborne nicotine portioning between the particle phase and the gas phase in equilibrium with the airborne droplets.

Examining Metal Contents in Primary and Secondhand Aerosols Released by Electronic Cigarettes

“…The increase in metal concentration with power can be attributed to a general increase in aerosol particle concentrations, which has also been shown to be temperature-dependent. 58,59 At higher powers, there is a faster increase in the filament's temperature, vaporizing a high volume of the EC liquid, thus generating a high concentration of particulates in aerosols. However, a marginal increase in metal emissions was observed when the power was increased from 25 to 45 W, suggesting that most of the power below 25 W has been used to evaporate the EC liquid.…”

Measuring Liquid Droplet Size in Two-Phase Nozzle Flow Employing Numerical and Experimental Analyses

“…Many scholars have carried out in-depth research on the atomization characteristics of nozzles by analyzing the size and distribution of atomized particles from the viewpoints of both numerical and experimental evaluation. Factors affecting the atomization effect such as the gas, liquid flow, liquid temperature, and viscosity have been extensively experimentally evaluated in the literature [ 3 , 4 , 5 , 6 , 7 ]. For instance, Wang et al [ 6 ] studied the pressure swirl and air flow of an atomizer with experiments in which the droplet size and distribution under different fuel pressure were measured using a laser particle-size analyzer.…”

Metals in Cannabis Vaporizer Aerosols: Sources, Possible Mechanisms, and Exposure Profiles

“…While the cannabis industry and regulators have focused on testing the concentrate oils in vaporizers, they have done minimal testing on the actual aerosol mixtures produced by these devices. E-cigarette aerosols are known to be a combination of liquid droplet particles and gas-phase molecules. − The aerosols from vaped cannabis products are also thought to be a combination of small oil droplets and vaporized gas-phase molecules but have not been well-characterized. However, some studies have shown low-molecular-weight compounds do exist in the gas phase, and it is known that compounds with higher molecular weights (similar to that of cannabinoids) when heated to a high temperature can create critical supersaturation, leading to nucleation and small particle formation .…”