"Lead study author
Maciej Goniewicz pointed out that while e-cigarette users are being exposed to risky chemicals, we don’t know yet whether these are at levels high enough to be concerning over a lifetime of use."
They don't attempt to determine risks of specific 'chemicals' even for smokers, because in the few cases where they have, they account for only a tiny fraction of the purported risk.
Another study: "estimating an upper bound on the contribution to lung cancer risk made by a specific, much-discussed causal pathway that links smoking to a polycyclic aromatic hydrocarbon (PAH) (specifically, benzo(a)pyrene diol epoxide-
dna) adducts at hot spot codons at p53 in lung cells. The result is a surprisingly small preventable fraction (of perhaps 7% or less) for this pathway,..."
Estimating preventable fractions of disease caused by a specified biological mechanism: PAHs in smoking lung cancers as an example. - PubMed - NCBI
BAP diol epoxide adducts were hyped in the media as the final, definitive answer to how smoking causes lung cancer. And Surgeon General reports make a big deal of it, too. But when you put it in perspective, it's a nothing-burger. And that's how all that FUD-mongering about chemicals is lying.