Comprehensive detection of unintentional hazardous substances in e-cigarette liquids

E-liquids can be unintentionally contaminated with various harmful substances, and the nicotine and glycols they contain can undergo oxidation, leading to the formation of degradation products and by-products.

A sample of 150 e-liquid products produced by 56 companies, 77% of which were manufactured in the Republic of Korea, was selected and analyzed qualitatively and quantitatively for 123 hazardous chemicals using 6 analytical methods.

This paper reports on a total of 91 compounds, which are considered unintended contaminants among the hundreds of chemicals identified in e-liquids. Of these, 41 compounds were identified and quantified for the first time in e-liquids in this study, 18 were classified as carcinogens (Groups 1, 2A, and 2B) by the International Agency for Research on Cancer, and 8 were classified as carcinogens, mutagens, and reproductive toxicants by the European Union. The 25 organic solvents detected are regulated by the United States Pharmacopeia. Ethylene glycol exceeded the residual solvent limit by up to 368-fold in 71 brands, ethanol by up to 26-fold in 3 brands, and isobutyl acetate by up to 1.9-fold in 4 brands.

Compared with previous studies, our findings indicate a positive trend toward reduced levels of well-known hazardous substances in e-liquids. However, many carcinogenic and toxic substances were still detected at high concentrations, and numerous additional hazardous substances were newly identified and quantified.

These results raise serious questions about the quality of e-cigarettes and their suitability as nicotine replacements. The detected substances and their concentrations should be incorporated in regulatory policies for e-cigarettes.