Introduction:
Second-hand aerosols from electronic cigarettes (e-cigarettes) contain toxic chemicals which are potentially harmful to bystanders and, thus, proper regulation is needed. Little is known about regulatory approaches taken by countries in minimising such exposure. This study aims to describe policies regulating the use of e-cigarettes in public and private sites among the European countries, identify barriers and promoters for the regulation adoption, and evaluate their compliance with the WHO FCTC recommendation on regulating e-cigarettes use indoors.

Methods:
A cross-sectional survey was conducted among experts from the 53 countries of the WHO European Region (May-July 2018). An internet-based questionnaire collected data provided by experts in each country on provisions of e-cig use in 27 public and private sites, level of difficulties in adopting the regulation, as well as the support and adherence to the regulations. A descriptive analysis was done to estimate the proportion (%) of each measure across countries.

Results:
We obtained information from 48 out of the 53 countries targeted. Among them, 77.1% had regulations of e-cigarettes, 58.3% had a specific national law on e-cigarette use, and 10.4% adopted some regulation at the subnational level. Regulations were more frequent among European Union countries. Twenty-one out of 27 sites were regulated by e-cigarette use national law. Education facilities were the most regulated site, with 58.3% banning the use of e-cigarettes in that area, while private areas (homes, cars) were the least regulated (39.6%). There were moderate difficulties in adopting the national law, support, and compliance to the law. Only one third of countries adhered to the WHO FCTC recommendation.

Conclusions:
Although the majority of European countries had introduced national regulation for e-cigarette use in public places, many countries still lack rules to protect non-users in indoor settings.