E-cigarette puffing patterns associated with high and low nicotine e-liquid strength: effects on toxicant and carcinogen exposure.

Sharon Cox,Maciej Goniewicz,Lynne Dawkins,Leon Kośmider,Catherine Kimber,Hayden Mcrobbie,Mira Doig

doi:10.1186/s12889-016-3653-1

Abstract

BackgroundContrary to intuition, use of lower strength nicotine e-liquids might not offer reduced health risk if compensatory puffing behaviour occurs. Compensatory puffing (e.g. more frequent, longer puffs) or user behaviour (increasing the wattage) can lead to higher temperatures at which glycerine and propylene glycol (solvents used in e-liquids) undergo decomposition to carbonyl compounds, including the carcinogens formaldehyde and acetaldehyde. This study aims to document puffing patterns and user behaviour associated with using high and low strength nicotine e-liquid and associated toxicant/carcinogen exposure in experienced e-cigarette users (known as vapers herein).Methods/designA counterbalanced repeated measures design. Participants: Non-tobacco smoking vapers; have used an e-cigarette for ≥3 months; currently using nicotine strength e-liquid ≥12mg/mL and a second or third generation device. Intervention: This study will measure puffing patterns in vapers whilst they use high and low strength nicotine e-liquid under fixed and user-defined settings, each for a week. The 4 counterbalanced conditions are: i) low strength (6mg/mL), fixed settings; ii) low strength user-defined settings; iii) high strength (18mg/mL) fixed settings; iv) high strength user-defined settings. Biomarkers of exposure to toxicants and carcinogens will be measured in urine. In the second phase of this study, toxicant yields will be measured in aerosol generated using a smoking machine operated to replicate the puffing behaviours of each participant. Primary outcomes: i) Puffing patterns (mean puff number, puff duration, inter-puff interval and mL of liquid consumed) and user behaviour (changes to device settings: voltage and air-flow) associated with using high and low strength nicotine e-liquid. ii) Toxicant/carcinogen exposure associated with the puffing patterns/device settings used by our participants. Secondary outcomes: i) Subjective effects. ii) comparisons with toxicant exposure from tobacco smoke (using documented evidence) and with recommended safety limits. Sample size: Twenty participants.DiscussionThe findings will have important implications for public health messaging regarding the relative risks and subjective effects associated with using high and low strength nicotine e-liquid, and for policy makers regarding regulations on nicotine concentrations in e-liquids.

Highlights

Contrary to intuition, use of lower strength nicotine e-liquids might not offer reduced health risk if compensatory puffing behaviour occurs
To assess the risk of whether toxicant/carcinogen exposure levels associated with the puffing patterns/ device settings used by our participants are at a level likely to affect human health by comparing these with those found in tobacco smoke and against recommended safety limits
The Estimated Exposure Index (EEI) for each toxicant will be calculated by comparing doses inhaled from e-cigarette to doses that would be inhaled from air with toxicant concentration specified by the HSE long-term exposure limits

Summary

Introduction

Use of lower strength nicotine e-liquids might not offer reduced health risk if compensatory puffing behaviour occurs. This study aims to document puffing patterns and user behaviour associated with using high and low strength nicotine e-liquid and associated toxicant/carcinogen exposure in experienced e-cigarette users (known as vapers ). Contrary to intuition, use of lower strength nicotine e-liquids might not offer reduced health risk if compensatory puffing behaviour occurs. We Dawkins et al [11] observed compensatory puffing patterns in which vapers took longer, more frequent puffs, and doubled the amount of e-liquid consumed during a one-hour ad lib puffing period with a low (6mg/mL) compared with a high (24mg/mL) strength nicotine e-liquid. In the userdefined condition proposed here, we will allow users to adjust the voltage and air-flow of the device ( atomiser resistance will be kept constant)

Objectives

Methods

Findings

Conclusion