Background:
We aimed to detect the composition and reported chemical health hazards of the most common electronic cigarette liquids (e-liquids) in nine European Union (EU) Member States (MS) prior to adoption of the Tobacco Product Directive (TPD).

Material and Methods:
Within the Horizon2020, EUREST-PLUS study, 122 of the most commonly used e-liquids were purchased from 9 EU MS. Chromatography - mass spectrometry and liquid chromatography - mass spectrometry methods were used to analyze the samples. Among the most frequently detected compounds (detected ≥4 times), Danger Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and Warning GHS codes were identified.

Results:
During the samples analysis, several discrepancies in nicotine concentration were detected among the samples from the 9 EU MS. French samples contained an average of 21.9% more nicotine than labelled, while Romanian samples contained an average of 22.5% less nicotine than labelled. In addition, in the 9.8% of the samples, the nicotine concentration exceeded the limit of 20 mg/ml. With regards to the samples’ composition, 171 different compounds were identified and detected 750 times in total while we did not identify samples positive for PAHs or nitrosamines. Finally from the 171 substances, only 5 (10.4%), (Oxime-, methoxy-phenyl, +/-.-.alpha.-Methylbenzyl acetate, 1,3-Dioxolane, 2-butyl-4-methyl-, Melonal and l-Menthyl acetate) were not associated with a Danger GHS and Warning GHS codes.

Conclusions:
As large number of potential harmful compounds was identified, the systematic monitoring and chemical evaluation of e-liquids is necessary in order to protect the consumers’ health.

Acknowledgements:
EUREST-PLUS is a Horizon2020 project conducted by researchers throughout Europe from both the six participating countries as well as other institution partners within Europe and abroad. Partnering organizations include the European Network on Smoking Prevention (Belgium), Kings College London (United Kingdom), German Cancer Research Centre (Germany), University of Maastricht (The Netherlands), University of Athens (Greece), Aer Pur Romania (Romania), European Respiratory Society (Switzerland), the University of Waterloo (Canada), the Catalan Institute of Oncology (Catalonia, Spain), Smoking or Health Hungarian Foundation (Hungary), Health Promotion Foundation (Poland), University of Crete (Greece), and Kantar Public Brussels (Belgium).

Funding:
The EUREST-PLUS Project takes place with the financial support of the European Commission, Horizon 2020 HCO-6-2015 program (EUREST-PLUS: 681109; C. Vardavas) and the University of Waterloo (GT. Fong). Additional support was provided to the University of Waterloo by the Canadian Institutes of Health Research (FDN-148477). GT. Fong was supported by a Senior Investigator Grant from the Ontario Institute for Cancer Research. E. Fernández is partly supported by Ministry of Universities and Research, Government of Catalonia (2017SGR139) and by the Instituto Carlos III and co-funded by the European Regional Development Fund (FEDER) (INT16/00211 and INT17/00103), Government of Spain.