Don't forget the cultural effects such as neopuritanism and anti-hipster-ism. Some of the backlash is of course the smell, from people insisting on using them

Don't forget the cultural effects such as neopuritanism and anti-hipster-ism. Some of the backlash is of course the smell, from people insisting on using them indoors or generally in close quarters. What chemicals are in the liquid is mysterious and vaguely unregulated so who knows. Its not as regulated as food and drink or pharmaceuticals. Its not unrealistic to assume its just different cancer causing materials, not no cancer causing materials at all. Its basically at the patent medicine level of regulation.