Influence of puff topographies on e-liquid heating temperature, emission characteristics and modeled lung deposition of Puff Bar™

Abstract

Puff Bar^™, one of the latest designs of e-cigarettes, heats a mixture of liquid using a battery-powered coil at certain temperatures to emit aerosol. This study presents a mass-based characterization of emissions from seven flavors of Puff Bar^™ devices by aerosolizing with three puff topographies [(puff volume: 55 < 65 < 75-mL) within 4-seconds at 30-seconds interval]. We evaluated the effects of puff topographies on heating temperatures; characterized particles using a cascade impactor; and measured volatile carbonyl compounds (VCCs). Modeled dosimetry and calculated mass median aerodynamic diameters (MMADs) were used to estimate regional, total respiratory deposition of the inhaled aerosol and exhaled fractions that could pose secondhand exposure risk. Temperatures of Puff Bar^™ e-liquids increased with increasing puff volumes: 55mL (116.6 °C), 65 mL (128.3 °C), and 75mL (168.9 °C). Flavor types significantly influenced MMADs, total mass of particles, and VCCs (μg/puff: 2.15-2.30) in Puff Bar^™ emissions (p < 0.05). Increasing puff volume (mL:55 < 65 < 75) significantly increased total mass (mg/puff: 4.6 < 5.6 < 6.2) of particles without substantially changing MMADs (~1μm:1.02~0.99~0.98). Aerosol emissions were estimated to deposit in the pulmonary region of e-cigarette user (41-44%), which could have toxicological importance. More than 2/3 (67-77%) of inhaled particles were estimated to be exhaled by users, which could affect bystanders. The VCCs measured contained carcinogens-formaldehyde (29.6%) and acetaldehyde (16.4%)-as well as respiratory irritants: acetone (23.9%), isovaleraldehyde (14.5%), and acrolein (4.9%). As Puff Bar^™ emissions contain respirable particles and harmful chemicals, efforts should be made to minimize exposures, especially in indoor settings where people (including vulnerable populations) spend most of their life-time.

Figure 1.

Structure of Puff Bar^™ devices.

Figure 2.

Schematic of experimental set up. Influence of puff volumes on (a) temperature to heating Puff Bar^™ e-liquid (b) mass-based particle size distribution (c) chemical characterization using EPA method TO-11A.

Figure 3.

Total mass (average (μg/puff) ± SD) of VCCs emitted by different flavor types of Puff Bar^™ on aerosolizing at puff volumes (mL: 55, 65, and 75) for n = 3 per puff volume. *Puff Bar^™ flavor types but not puff volumes significantly influence (at p < 0.05) total mass of VCCs.

Figure 4.

Mass (μg/puff) of top five VCCs emitted in different flavor types of Puff Bar^™ on aerosolizing at puff volumes (mL: 55, 65, and 75) for n = 3 per puff volume (average ± SD): Formaldehyde (0.61 ± 0.35), Acetaldehydes (0.46 ± 0.47), Acetone (0.42 ± 0.14), Isovaleraldehyde (0.22 ± 0.05), and Acrolein (0.18 ± 0.25).

Figure 5.

Mass-based proportion (%) of top five VCCs out of total emissions in different flavor types of Puff Bar^™ on aerosolizing at puff volumes (mL: 55, 65, and 75) for n = 3 per puff volume (average ± SD): Formaldehyde (29.6% ± 0.12), Acetone (23.9% ± 0.09), Acetaldehyde (16.4% ± 0.09), Isovaleraldehyde (14.5% ± 0.08), Acrolein (5.0% ± 0.05).