Electronic cigarette use, or vaping, is on the rise as many consider it a healthier alternative to smoking. However, in a study published in the American Chemical Society journal Chemical Research in Toxicology, researchers from the Penn State University College of Medicine report that e-cigarettes produce considerable levels of reactive free radicals created by the high-temperature heating coils that warm up the nicotine solution.

Dr. John Richie, a professor at Penn State and senior author of the research, says, “The identification of these radicals in the aerosols means that we can’t just say e-cigarettes are safe because they don’t contain tobacco. They are potentially harmful.”

The researchers found that levels of free radicals in e-cigarettes are between 100 to 1,000 times less than the levels produced by tobacco cigarettes, still making them a better choice than traditional cigarettes although they still carry risk. Richie explains, “The levels of radicals that we’re seeing are more than what you might get from a heavily air-polluted area, but less than what you might find in cigarette smoke.” Previous research has found that e-cigarette smoke also contains aldehydes that can potentially cause cellular and tissue damage.