Studies on healthy human cells and mice have shown that e-cigarette smoking increases the risk of heart attack and cancer. It has been observed that nicotine withdrawn from electronic cigarettes turns into chemicals that damage DNA in the heart, bladder and lungs, and weakens the body's genetic repair mechanism.

Researchers have reported that the change in DNA is similar to that caused by secondhand smoking. Although electronic cigarette smokers do not ingest many harmful chemicals in cigarettes, they may suffer from different diseases due to deterioration in their bodies.

Researchers have stated that studies need observation for a longer period of time and that their studies on this subject will continue.

https://www.theguardian.com/science/2018/jan/29/vaping-may-raise-cancer-and-heart-disease-risk-study-suggests