It's smoke.
Remember the diesel emissions scandal? It's nothing compared to purposely inhaling smoke. This is the problem:
https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbo...
Remember the diesel emissions scandal? It's nothing compared to purposely inhaling smoke. This is the problem:
https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbo...
Edibles and vaporization avoid the combustion byproducts. https://en.wikipedia.org/wiki/Epigenetics
Longitudinal studies may or may not be able to identify causative relations amidst confounding variables like e.g. air pollution.
Lung cancer incidence from low to high according to one observational study: NS, MS, MTS, TS.
"Hypothesizing that marijuana smokers are at a significantly lower risk of carcinogenicity relative to tobacco-non-marijuana smokers: evidenced based on statistical reevaluation of current literature." (2008) https://www.ncbi.nlm.nih.gov/m/pubmed/19004418/
Is that the case for vaping or edibles? Nobody has any idea yet.