Introduction

Since its introduction, the e-cigarette has become a commonly used consumer product. In this study, we investigate whether regulatory changes had an impact on the quality of refill liquids (e-liquids) available on the Belgian market through analysis of their chemical composition. Hence, the nicotine concentration accuracy was investigated in samples before, during and after the implementation of the revised Tobacco Product Directive (TPD) as an indicator of good manufacturing practices. This is, however, not enough to assure the quality. Therefore, extra criteria were also assessed based on TPD requirements.

Methods

By using in-house validated methods, a total of 246 e-liquids purchased prior (2013-2015), during (2016) and after (2017-2018) the implementation of the TPD revisions, were analyzed for the presence of nicotine, nicotine-related impurities, volatile organic compounds (VOCs), caffeine and taurine, and the flavours diacetyl and acetylpropionyl.

Results

Although not all manufacturers managed to produce and label their products accurately, nicotine labelling discrepancies have decreased over time. Moreover, also the number of e-liquids, containing high risk VOCs (10% in 2016 versus none of the samples in 2017-2018), caffeine (16% in 2017 versus 5% in 2018) and diacetyl and acetylpropionyl (55% in 2017 versus 27% in 2018 of sweet flavoured samples) diminished over time.

Conclusion

Our results demonstrate that the overall quality of the e-liquids has improved after the implementation of the revised TPD. However, the results also show that periodic quality control might be required to ensure further compliance to the TPD.

Implications

This study clearly demonstrates that the implementation of the revised TPD has improved the quality of the e-liquids on the Belgian market. However, there are still e-liquids that are not in agreement with the TPD due to nicotine concentration label discrepancies, presence of e-liquid impurities and controversial flavours diacetyl and acetylpropionyl or the additive caffeine.