Findings of an animal study have shown that the damage caused by nicotine in e-cigarettes appear to damage the DNA in ways that may elevate risks for cancer.

Mice Study

In experiments on mice, Moon-Shong Tang, from New York University School of Medicine, and colleagues saw damage to the DNA and its ability to repair itself that elevate the risk of mutation and cancer development.

The researchers exposed the animals to e-cigarette vapors that contain both nicotine and a liquid solvent. They also exposed the mice to nicotine and solvents separately. Tang and colleagues found that the solvent alone does not cause damage to the DNA, but exposure to nicotine and the solvent caused the same damage as exposure to nicotine alone.

The researchers also exposed cultured human bladder and lung cells to nicotine and found the same effects they have observed in experiments involving mice.

"These results indicate that nicotine nitrosation occurs in vivo in mice and that E-cigarette smoke is carcinogenic to the murine lung and bladder and harmful to the murine heart. It is therefore possible that E-cigarette smoke may contribute to lung and bladder cancer, as well as heart disease, in humans," the researchers wrote in their study, which was published in the journal PNAS on Jan. 29.

E-Cigarettes May Pose Cancer Risk

The researchers said that if the findings will be confirmed in future studies, it could mean that e-cigarettes, long been considered to be the safer alternative to traditional cigarette and tobacco products, also carry cancer risk through the nicotine that they deliver.

Not all results of research on animals, however, produce similar results in humans. The findings of the study by itself are neither conclusive. The researchers conducted the study over a 12-week period. Tumors do not develop in 12 weeks.

Researchers continue to conduct studies that investigate the possible benefits and dangers of using e-cigarettes. A report released by the National Academies of Sciences, Engineering, and Medicine earlier this month revealed that vaping is less harmful than smoking conventional cigarettes.

The report also said that the potential dangers and benefits of vaping e-cigarettes may depend on the user's age. Vaping May help adults quit smoking but may entice young people to smoke conventional tobacco.

"While e-cigarettes have the potential to benefit some people and harm others, scientists still have a lot to learn about whether e-cigarettes are effective for quitting smoking," the U.S. Centers for Disease Control and Prevention has advised. "If you've never smoked or used other tobacco products or e-cigarettes, don't start."