UNITED NEWS INTERNATIONAL (UNI) — New research suggests the nicotine found in e-cigarettes could increase risks of cancer and heart disease.

A study published Jan. 29 in the Proceedings of the National Academy of Sciences described mice exposed to e-cigarette smoke for three hours a day, five days a week, over three months.

Researchers found the nicotine converted to chemicals that damaged DNA in the heart, lungs and bladder.

Study leader Moon-Shong Tang from New York University’s School of Medicine said this damage made cells more likely to mutate and develop into cancer.

The study claims about 18 million people smoke e-cigarettes a year.

It concludes e-cigarettes could possibly carry cancer risks but researchers hope to do more long-term experiments to look at the possibility of developing tumors.

Tang told The Guardian it may take years since cancer is a slow process.