One study compared the urine of e-cigarette users to that of non-smokers. Urine samples were examined for five known bladder carcinogens that are either present in traditional cigarettes or common solvents believed to be used in some e-cigarette liquids.
The results showed urine from 92 percent of e-cigarette users tested positive for two of the five carcinogenic compounds.
In another study, researchers looked at the effect of nicotine and its metabolites on DNA repair and mutational susceptibility. They found e-cigarette smoke induced tumorigenic DNA damage in bladder mucosa.
Overall, researchers predicted e-cigarette smokers have a high bladder cancer risk.