My understanding of the menthol issue is that it's not a safety issue but rather based on research which indicates that menthol is an attractive flavour to non-smokers and also that menthol cigarette smokers find it harder to quit nicotine. However, in his preliminary flavouring research, Maciej Goniewicz found that menthol-flavoured juice kills more cells than most other flavours. So it may well emerge that there is something in menthol which is hazardous. Afaik it's only Germany which is moving to ban menthol in juice although most EU member states have banned menthol cigarettes from 2020. SanFran has also banned menthol cigarettes.
Which cells do "most other flavours" kill?