Compensatory puffing with lower nicotine concentration e-liquids increases carbonyl exposure in e-cigarette aerosols

Introduction Article 20 of the Tobacco Products Directive (EU-TPD) specifies that e-liquids should not contain nicotine in excess of 20 mg/mL, thus many vapers may be compelled to switch to lower concentrations and in so doing, may engage in more intensive puffing. This study aimed to establish whether more intensive puffing produces higher levels of carbonyl compounds in e-cigarette aerosols. Methods Using the HPLC-UV diode array method, four carbonyl compounds (formaldehyde, acetaldehyde, acetone and acrolein) were measured in liquids and aerosols from nicotine solutions of 24 and 6 mg/mL. Aerosols were generated using a smoking machine configured to replicate puffing topography data previously obtained from 12 experienced e-cigarette users. Results Carbonyl levels in aerosols from the puffing regimen of 6 mg/mL were significantly higher (p<0.05 using independent samples t-tests) compared with those of 24 mg/mL nicotine. For the 6 and 24 mg/mL nicotine aerosols respectively, means ±SD for formaldehyde levels were 3.41±0.94, and 1.49±0.30 µg per hour (µg/h) of e-cigarette use. Means ±SD for acetaldehyde levels were 2.17±0.36 and 1.04±0.13 µg/h. Means ±SD for acetone levels were 0.73±0.20 and 0.28±0.14 µg/h. Acrolein was not detected. Conclusions Higher levels of carbonyls associated with more intensive puffing suggest that vapers switching to lower nicotine concentrations (either due to the EU-TPD implementation or personal choice), may increase their exposure to these compounds. Based on real human puffing topography data, this study suggests that limiting nicotine concentrations to 20 mg/mL may not result in the desired harm minimalization effect. This article has been accepted for publication in Nicotine and Tobacco Research. Published by Oxford University Press.