While no clear cause and effect between vaping and lung cancer has been established yet in humans, there is an array of known cancer-causing substances in vaping products. One study detected more than 500 chemicals in tested vaping cartridges, in tested vaping cartridges, with most being classified as carcinogens. Since cancer induced by carcinogens can take many years to emerge, vaping may ultimately rival cigarette smoking as a contributor to lung cancer occurrence.
Meanwhile, some earlier animal research funded by the National Institutes of Health showed vaping led to lung cancer in mice. One group of mice was exposed to e-cigarette vapor containing nicotine and the other group was exposed to vapor without nicotine. More mice in the nicotine-containing group developed lung tumors. The vaping exposure used in the study was equivalent to 3 to 6 years of vaping in humans. Aside from this being an animal study, another limitation is the mice did not inhale smoke like a vaper would do, but instead absorbed it through full body exposure. It does show a lung cancer link, however, necessitating further human research.