The number of American adults who smoke cigarettes is at a historic low.

In 1965, more than 42 percent of adults smoked. In 1997, less than a quarter of adults lit up regularly.

Those rates dropped to 15 percent in 2015, according to data released this week by the U.S. Centers for Disease Control and Prevention (CDC).

Currently, more men smoke than women, but there are also more former male smokers than female. Still, 67 percent of women have never smoked, while 58 percent of men never have.

While this is a good sign overall, it doesn’t mean smokers are ditching their habits entirely. Many have ditched the antiquated nicotine delivery system for newer electronic versions.

It is, for many, one way to get off cigarettes for good.

According to the Henry J. Kaiser Family Foundation, nearly 61 percent of current smokers have said they’ve tried to quit smoking at least once in the past year.

E-Cigarettes Replacing Cigarettes

All over the globe, especially in developed countries, e-cigarettes are becoming alternatives to smoking on the belief the vapor from them is safer than the smoke in cigarettes.

While e-cigarettes don’t contain the cancer-causing tar of tobacco, the scientific jury is still out on their overall safety to people’s mouths, throats, and lungs.

According to a new online Reuters/Ipsos poll, about 10 percent of people polled report using e-cigarettes, a number unchanged from 2015. However, more are expressing concerns about the health aspects of their electronic products.

About half of the people polled believe e-cigarettes and vaping aren’t better for you than cigarettes, nor could they help people quit smoking.

Still, e-cigarettes have been used as a way for smokers to quit cigarettes but not get off nicotine completely.

The CDC reports that one in four recent former smokers now use e-cigarettes, while one in six use both traditional cigarettes and e-cigarettes.

Nearly one-half of current cigarette smokers and more than one-half of recent former cigarette smokers have tried an e-cigarette, according to the CDC. Nearly 9 percent of long-term former smokers haven’t tried one, suggesting that many have quit nicotine all together.

A study out of Imperial College London, determined that 11 percent of Europeans had tried an e-cigarette by 2014, a 60 percent increase from 2012.

Dr. Filippos Filippidis, lead author of the research from the School of Public Health at Imperial, said their research shows e-cigarettes are becoming popular across Europe, which is why the need for more research into their effects is urgently needed.

“Although this data shows most of the people who use e-cigarettes are current or former smokers — which suggests the devices may be helping some of them quit smoking — it is worrying that some people who have never smoked are using them. This raises the question of whether they could be a 'gateway' to smoking conventional cigarettes,” he said in a press release.

“However, there is debate about the risks and benefits associated with e-cigarettes. For instance, we don't know whether we may start to see diseases emerge in 10-20 years' time associated with some of the ingredients.”

Read More: How Quitting Smoking Improves Your Life »

Kids’ Use of E-Cigarettes Continues to Rise

Filippidis’ fears of a “gateway” aren’t unfounded.

CDC data show that while tobacco use among high school children has remained stable over the past five years — one in four are current users — cigarette use dropped from 15 percent in 2011 to 9 percent in 2015.

Instead of traditional cigarettes, teens are now using e-cigarettes.

Overall, 16 percent of teens report using e-cigarettes. It’s the most common way high school students ingest tobacco.

That translates to 3 million middle and high school students who currently use e-cigarettes. Cigarettes, cigars, hookah, and smokeless tobacco use ranges between 6 and 9 percent.

During the shift from traditional to e-cigarettes, spending on e-cigarette advertising rose from $6 million in 2011 to an estimated $115 million in 2014, according to the CDC.

Read More: E-Cigarettes Less Toxic but Still Better Not to Smoke »