Again, I think the pertinent answer lies in considering just how many OTHER sources of these things we're subjected to on a daily basis. A single inhalation in an apartment that has just had a new carpet installed might subject you to more solvent exposure than a LIFETIME of use of DMT extractions. Thought about in those terms (and with regard to carcinogenic potential of PARTICULAR molecules--which AREN'T what we tend to use), the risk doesn't seem important.