We are concerned that the focus on nicotine in electronic cigarettes is causing other associated risks to be underestimated (see Nature 523, 267; 2015).

For example, there are no moves to evaluate the chemical hazards attributable to the non-nicotine components of e-cigarettes, such as vaporizing solvents or liquid 'flavourings' — let alone to regulate them. Neither will the latest European legislation on tobacco and related products help (see go.nature.com/yufgfv). It does not cover liquids or devices that are branded as 'nicotine-free': however, these frequently contain nicotine and escape safety testing through erroneous labelling (see C. Hutzler et al. Arch. Toxicol. 88, 1295–1308; 2014).

Electronic vaping could also offer a route for using drugs such as cannabis (A. J. Budney et al. Addiction http://doi.org/7cc; 2015). With the technology set to evolve and spread rapidly, more rigorous and extensive evaluation is urgently needed.