(CNN) A lot of important questions surround the safety and health effects of e-cigarettes, a relatively new technology, but a new study says e-cigarettes are less toxic than traditional ones.

Although the long-term health effects aren't known, there are ways to estimate them, said Maciej Goniewicz , one of the authors of the study , published Friday in the journal JAMA Network Open. "One of the ways to do that is to measure chemicals in our body that can indicate exposure to toxicants, so some biomarkers, and that is what we did in the study," said Goniewicz, a pharmacologist and toxicologist at Roswell Park Comprehensive Cancer Center.

Unsurprisingly, those who did not use either e-cigarettes or combustible cigarettes had significantly lower concentrations of exposure to most of the biomarkers. But those who used only e-cigarettes had lower levels of exposure than people who smoked traditional cigarettes or who smoked traditional cigarettes and vaped.

Researchers looked at 5,105 US adults who each fell into one of four groups: cigarette-only smokers, e-cigarette-only users, those who used both e-cigarettes and traditional cigarettes (called dual users) and those who used neither. The data used was collected from 2013 to 2014 and came from the Population Assessment of Tobacco and Health study.

Goniewicz and his fellow authors looked at the concentrations of 50 biomarkers that showed exposure to tobacco-related toxicants.

"The users of [e-cigarettes] are exposed to several toxicants," Goniewicz said. "On the other hand, when we compared with the tobacco smokers, then we found that the levels of the toxicant in the e-cigarette users are significantly lower."

The mean concentration of total nicotine equivalents was 93% lower in e-cigarette-only users than in traditional cigarette smokers.

Dual users had the highest levels of exposure.

"In that group, we did not observe any reduction in the toxicant exposure," Goniewicz said. "They have the same levels or even, for certain chemicals, higher than smokers."

Cigarette smokers had biomarker concentrations that were 36% lower for total nicotine equivalents and NNAL, a tobacco-specific nitrosamine, levels that were 23% lower than those of dual users. These nitrosamines are chemicals present in tobacco products that have been shown to cause lung cancer, Goniewicz said.

For those who are trying to either quit or reduce the harm from smoking, Goniewicz believes that e-cigarettes could be beneficial -- but only when used the right way.

"The only way for smokers to reduce exposure to toxicants is to completely switch to electronic cigarettes. So, no smoking but e-cigarette use," he said.

Theodore Wagener , director of tobacco regulatory science research at the Oklahoma Tobacco Research Center and an assistant professor at the University of Oklahoma Health Sciences Center, wrote an editorial published alongside the study. "Dual users evidenced the highest levels of tobacco toxicant exposure, even more than exclusive smokers. While likely influenced by smoking frequency, this finding has also been consistent in the literature and is cause for concern as most e-cigarette users are dual users," he wrote.

Although he points out that some dual users might be in the process of switching completely, there is also a possibility that they are long-term dual users or have failed at switching methods.

Because of this, "clear health messages must be delivered to smokers that completely switching from smoking to e-cigarette use is necessary to confer a significant reduction," he said.

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The new study is "very important," said Richard Miech , principal investigator at Monitoring the Future at the University of Michigan Institute for Social Research. "To my knowledge, this is one of the first toxicological studies based on population data and therefore one of the first that can be directly generalized to the US population.

"I think a lot of people think that vaping nicotine is pretty much harmless and that there are no health consequences, and this is one of the first studies I know of to show that it looks like there are some toxicants that vapers are exposing themselves to," said Miech, who was not involved in the research.