Many smokers switched to electronic cigarettes hoping they would be less harmful than tobacco cigarettes. But a new study at the University of Connecticut found that e-cigarettes are potentially as harmful as tobacco cigarettes.

Using a new testing device, they found that e-cigarettes with a nicotine-based liquid could damage DNA as much as unfiltered cigarettes. Cellular mutations caused by DNA damage can lead to cancer.

The researchers also discovered the vapor from non-nicotine e-cigarettes caused as much DNA damage as filtered cigarettes, probably due to the numerous chemical additives in the vapors.

The amount of DNA damage e-cigarettes cause depends on the amount of vapor the user inhales, the other additives present, whether nicotine or non-nicotine liquid is used, and other factors, says the study's lead author Karteek Kadimisetty.

To explore whether or not the chemicals in e-cigarettes could damage DNA, the researchers used a device they developed that can quickly detect DNA damage.

The device uses icropumps to push liquid samples across multiple "microwells" embedded in a small carbon chip. The wells are pre-loaded with reactive human metabolic enzymes and DNA. As the samples drop into the wells, new metabolites that have the potential to cause DNA damage are formed.

Kadimisetty says that by converting chemicals into their metabolites during testing, it replicates what happens in the human body. Reactions between the metabolites and the DNA generate light that is photographed, and within five minutes, researchers can see how much DNA damage is done to a sample.

"Some people use e-cigarettes heavily because they think there is no harm," he says. "We wanted to see exactly what might be happening to DNA."

The results were clear. "From the results of our study, we can conclude that e-cigarettes have as much potential to cause DNA damage as unfiltered regular cigarettes," Kadimisetty said.

The results appear in the journal ACS Sensors.

Other studies have also questioned the safety of electronic cigarettes. A Harvard study found that 75 percent of flavored e-cigarettes contained diacetyl, a chemical linked to a severe respiratory disease called bronchiolitis obliterans or "popcorn lung" because it was first noticed in workers who worked in popcorn factories and inhaled artificial butter flavoring.

Of 51 different e-cigarettes tested, at least one of three toxins — diacetyl, acetoin, and 2.3-pentanedione — was found in 47.  In addition, the amount of diacetyl found in 39 of the e-cigs was higher than the laboratory was capable of measuring.

According to a study published in the American Journal of Physiology, smoking electronic cigarettes alters the same genes in the respiratory tract as smoking cigarettes, genes vital to defending the body against bacterial infections, viruses, and inflammation. Researchers compared a group of non-smokers, smokers, and those who used e-cigarettes. They found that smoking cigarettes decreased the expression of 53 genes important in the immune response of epithelial cells that line the upper airway of the respiratory tract, but e-cigarettes suppressed them even more.