We do not have the data yet, and that matters
Cancers take decades to develop. E-cigarettes have not existed long enough for that data to exist. So anyone who tells you vaping definitely does, or definitely does not, cause cancer is getting ahead of the evidence.
What we can measure: carcinogen exposure
Instead of cancer counts, researchers measure carcinogens in the body. NNAL, a metabolite of a tobacco-specific carcinogen, runs about 85 to 98% lower in people who only vape than in people who smoke. So the exposure that drives cancer is much lower. Lower, not zero.
Our calculator projects vaping cancer risk at roughly 10% of an equivalent cigarette, and labels it as a projection from exposure data, not a proven finding.
The heart is where there IS data
For cardiovascular risk, population studies exist. Recent pooled meta-analyses put the odds of heart problems for vapers at around 1.3 to 1.5x a non-user. Real and elevated, but well below cigarettes.
Two things worth clearing up
The 2019 to 2020 lung-injury outbreak (EVALI) was traced almost entirely to vitamin E acetate in illicit THC vape carts, not regulated nicotine e-liquid.
And vape aerosol is not just water. It carries ultrafine particles and trace metals that reach deep into your lungs.
The honest summary
Much less harmful than smoking, not harmless, and the cancer piece is genuinely unknown rather than reassuringly zero.