David B. Kane and Mark J. RusyniakAltria Client Services, 601 East Jackson Street, Richmond, VA 23219

Measurement of E-cigarette Aerosol Particle Size with a Low Flow Cascade Impactor

• E-cigarettes produce a condensation aerosol from evaporation followed by rapid cooling of the flavor solution

• Particle size is an important aerosol parameter for e-cigarettes- Understanding airway deposition- Exhaled smoke visibility- Vapor sensory characteristics

• Due to semivolatile nature of the aerosol particle size, measurements are affected by:- Evaporation (due to dilution)- Coagulation (caused by long residence times)

• Factors affecting the particle size of e-cigarette aerosols have not been thoroughly investigated

INTRODUCTION

• To investigate the factors that affect the particle size ofe-cigarette aerosols.

OBJECTIVE

Particle size is an important aerosol property related to dosimetry and aerosol dynamics. For e-cigarettes, which produce volatile and dynamic condensation aerosols from propylene glycol and/or glycerin, the measurement of particle size can be particularly challenging. The high dilution ratios required by conventional instruments can cause particle evaporation. Conversely, long residence times between sampling and measurement can cause particle coagulation. To address these issues, we have developed a particle size measurement system for e-cigarette aerosols using a low flow cascade impactor. This measurement system is not limited by the concentration of the particles and minimal dilution air is required for impactor operation, thereby minimizing the effects of evaporation. The impactor is interfaced with a sampling system that is capable of generating a puff on an e-cigarette and directly introducing the aerosol into the inlet flow of the impactor, thereby minimizing the time for coagulation.

ABSTRACT RESULTS

• Puff flow rate is the major factor affecting aerosol particle size for e-cigarettes

• Commercially available e-cigarette products produce aerosols with submicron particle sizes

• Glycerin content of the flavor formulation has a complex affect on particle size

SUMMARY

This poster may be accessed at www.altria.com/ALCS-Science

METHODSSchematic Diagram of the Low Flow Impactor Measurement System

Low Flow

Impactore-cigarette

Makeup flow (2 LPM – puff flow)

Puff flow (off to puff)

Impactor

flow (2 LPM)

Solenoid valve(controlled by lab timer)

• Advantages of the Low Flow Impactor System- Direct measurement of aerosol mass distribution- Low dilution (~ 3:1 depending on puffing conditions)- Minimal residence time- Direct introduction of aerosol to measurement system

Low Flow Impactor Measurement System

Puffing Conditions• Number of puffs: 5• Length of puffs: 5 s

• Puff flow rate: 0.66 L/min• Puff volume: 55 mL

Typical Particle Size Distributions Measured by the Low Flow Impactor

• Median diameter of cigarette smoke: 0.4 micronat 1.05 L/min

• Median diameter of e-cigarette aerosol: 0.4-0.9 micronat 0.66 L/min

• E-cigarette aerosols tend to have a broader distributionas tested

3R4F Kentucky Reference Cigarette Commercial E-cigarette Product

Smoked for one 35 mL, 2 s puff Puff Flow Rate: ~1.05 L/min

Smoked for five 55 mL, 5 s puffsPuff Flow Rate: 0.66 L/min, Interval: 10 s

• The measured e-cigarettes have median aerosol particle sizes between 0.5 and 0.9 microns

• This particle size range is typical for condensation aerosols

Median Aerosol Particle Size of Commercial E-cigarettes

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• Small amounts of glycerin (up to 5% by mass) in the formulation cause a decrease in particle size

• As glycerin in the formulation increases over 5%, the particle size increases

• Results suggest a complicated relationship between flavor formulation and particle size

Effect of Carrier Composition on Median Particle Size

nicotine and flavor solutions with different propylene glycol to glycerin ratios (by mass)

Measurement was made with a prototype e-cigarette with 1.5 % by mass

• The measured particle diameter is dependent on the puff flow rate

• Higher flow rate puffs produce smaller median diameter aerosols

• This effect will contribute to differences in the results between different particle size measuring systems

Influence of Puff Flow Rate on Particle Size

Puff Flow Rate: the independent variablePuff Duration: 5 s, Interval 10 s

Prototype E-cigarette with 60% PG - 40% Glycerin Formulation with 1.5% Nicotine

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