Fact
When smoked indoors, e-cigs release a higher level of Nickel and Silver chemicals than combustible cigarettes.
Source 1:
Saffari, A., Daher, N., Ruprecht, A., De Marco, C., Pozzi, P., & Boffi, R. et al. (2014). Particulate metals and organic compounds from electronic and tobacco-containing cigarettes: comparison of emission rates and secondhand exposure. Environ. Sci.: Processes Impacts, 16(10), 2259-2267.