Data presented at the 112^th Annual Scientific Meeting of the American Urological Association (AUA) shows harmful links between the use of e-cigarettes and bladder cancer risk.

Use of electronic cigarettes (e-cigarettes), which is also known as "vaping", has grown drastically since first entering the marketplace more than a decade ago. While traditional cigarette smoking is a clear cause of bladder cancer, much less has been studied about the bladder cancer risk associated with e-cigarettes.

In the study titled Evaluation of E-Cigarettes Users Urine for Known Bladder Carcinogens, researchers 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 users were mostly male with an average age of 39 years old. The non-smokers had abstained from traditional cigarettes for at least six months prior to the test.

Results showed that urine from 92 percent of e-cigarette users tested positive for two of the five carcinogenic compounds.

The authors stress that further research is needed to clarify the contribution e-cigarettes make to the development of bladder cancer, given the greater concentration of carcinogenic compounds in the urine of e-cigarette users in this study.

A second study, E-Cigarette Smoke is Potentially Bladder Carcinogenic - It Induces Tumorigenic DNA Adducts and Inhibits DNA Repair in Urothelial Cells, provides more evidence of harmful effects of e-cigarettes on the bladder.

The authors note that E-cigarettes have been advertised as a way of delivering the stimulating effects of tobacco smoke, without the harmful health risks. Since 90 percent of inhaled nicotine is excreted to urine, New York University researchers set out to examine if e-cigarette smoke induced DNA damage in bladder mucosa. Researchers also looked at the effect of nicotine and its metabolites, nitrosamines and formaldehyde on DNA repair and mutational susceptibility in cultured human urothelial cells. Urothelial cells form the tissue that lines much of the bladder.

Using a mouse model, this research showed: ?

• E-cigarette smoke induced tumorigenic DNA damage in bladder mucosa. ?
• Nicotine, nitrosamine and formaldehyde also induced the same types of DNA damage in human urothelial cells, as well as inhibited DNA repair and enhanced mutational susceptibility.
• Nicotine can be nitrosatized in urothelial cells, then further metabolized into carcinogenic nitrosamines and formaldehyde.

Overall, researchers predicted e-cigarette smokers have a high bladder cancer risk.

"These studies raise new concerns about the harmful impact of e-cigarettes on bladder cancer," said Sam S. Chang, MD, MBA, professor of urologic surgery at Vanderbilt Ingram Cancer Center. "We've known traditional smoking raises bladder cancer risk, and given the surge in popularity of e-cigarettes, it's imperative we uncover any potential links to e-cigarette smoke and bladder cancer."