Heart disease is the leading killer in the US. Are you saying the number of excess deaths among smokers (over the baseline in the non-smoking population) is roughly equally distributed between heart disease and lung disease? Can you give a cite?
Overall though, cancer is what I’d be by far the least concerned about with respect to vaping.
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1524-6175...
Combustion in general produces a bunch of nasty chemicals.
It basically works as an accelerant, stimulating and encouraging tumor growth and metastasis.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3915512/#S7titl...
"Nicotine, which is the addictive component of tobacco smoke, is unable to initiate tumorigenesis in humans and rodents; at the same time, nicotine has been shown to promote tumor growth and metastasis by inducing cell cycle progression, epithelial-to-mesenchymal transition (EMT), migration, invasion, angiogenesis, and evasion of apoptosis in a variety of systems (8–13). In addition, nicotine has been shown to induce secretion of growth factors and cytokines altering the physiology of multiple organ systems (8–13). These observations suggest that nicotine likely contributes to the progression and metastasis of tumors that are initiated by tobacco carcinogens."
my understanding of the risks of heart disease and stroke affiliated with smoking is that they’re primarily due to the fact that regular smokers are living their lives in a permanent state of mild carbon monoxide poisoning. CO has a time course on the order of about 10 hours, so if you have more than two smoke breaks a day, your hemoglobin supply is semi-permanently compromised ...
Here, I found this after approximately 15 seconds of research
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4363846/
"Nicotine poses several health hazards. There is an increased risk of cardiovascular, respiratory, gastrointestinal disorders. There is decreased immune response and it also poses ill impacts on the reproductive health. It affects the cell proliferation, oxidative stress, apoptosis, DNA mutation by various mechanisms which leads to cancer. It also affects the tumor proliferation and metastasis and causes resistance to chemo and radio therapeutic agents. The use of nicotine needs regulation. The sale of nicotine should be under supervision of trained medical personnel."
The ease of locating this leads me to believe it would be simple to find additional support for the idea that nicotine is not entirely benign. I am not going to take the time to do this, even though that risks a downvote on HN.