As regular cigarettes decline in popularity, tobacco firms have jumped into what they see as a burgeoning market.

For decades, cigarettes cornered the market on nicotine.

People who decided to take up smoking chose the cigarette over any other nicotine delivery system available, including pipes and chewing tobacco.

This trend held true for generations of smokers, but in the past 10 years the cigarette industry has seen a small but significant sea change.

Electronic cigarettes are catching fire with an entirely new generation of smokers.

And tobacco companies have taken notice.

“It’s the most disruptive change in the tobacco market,” Jeff Drope, PhD, vice president of economic and health policy research for the American Cancer Society (ACS), told Healthline. “There is no parallel.”

Read more: E-cigarette flavorings can be toxic to lung cells »

Electronic nicotine delivery systems are not new.

The devices have been around in some form or another for nearly 30 years.

This current iteration of e-cigarettes made its way to the United States market by way of China.

However, the recent explosion of e-cigarette popularity caught the attention of tobacco companies a few years ago.

What was once a market populated by small independent manufacturers has given way to Big Tobacco.

And this move has anti-smoking organizations concerned.

“This is part of an ongoing strategy in the Big Tobacco playbook,” Erika Sward, assistant vice president of national advocacy for the American Lung Association (ALA), told Healthline.

The popular brand VUSE, is owned by R.J. Reynolds Vapor Company, a subsidiary of the tobacco giant Reynolds America.

British American Tobacco (BAT), the largest tobacco company in the Europe, launched Vype around four years ago.

Altria (formerly Phillip Morris) owns MarkTen.

Lorillard paid $135 million for Blu, but when R.J. Reynolds bought that tobacco company in 2015, its e-cigarette brand was sold to Imperial Tobacco, a company in the United Kingdom.

Today, global e-cigarette sales amount to around $5 billion a year.

That compares to the $92 million cigarette market, but the e-cigarette industry is expected to grow 24 percent per year through 2018.

“Big Tobacco is now dominating in dollars in sales,” Drope said.

Read more: E-cigarettes are less toxic but still better not to smoke »

The tobacco industry appears so confident in the technology that they are now funding research that looks at the health effects of e-cigarettes vs. regular cigarettes.

A recent study, funded by British American Tobacco used 3-D modeling to compare the inflammation in the lungs from e-cigarettes and regular cigarettes.

The study, published in Applied In Vitro Toxicology, showed a dramatic drop in lung inflammation with e-cigarettes.

“Researchers reported changes in the expression levels of 123 genes when reconstituted lung tissue was exposed to cigarette smoke, compared to only two genes that could be confirmed following exposure to e-cigarette aerosols,” according to a press release.

These finding are similar to what initial research has uncovered about e-cigarettes. A small batch of studies do suggest that they pose less of a health threat than regular cigarettes.

“From a cancer perspective, the levels of carcinogens are lower,” Drope said.

BAT did not provide comment for this story. R.J. Reynolds also declined to be interviewed, but did provide a statement:

“We believe that vapor products and other noncombustible tobacco products may present less risk to adult tobacco consumers than smoking cigarettes. Although these products have not been used by consumers for a sufficient period of time to develop definitive scientific conclusions about their level of risk reduction, there is a growing body of scientific evidence that these products may present less risk than smoking. While some studies report that there may be health risks associated with these products, those risks appear to be lower than the risks of smoking cigarettes.”

Read more: Many teens who wouldn’t have smoked use e-cigarettes »

There are many unknowns about the health hazards of e-cigarettes, and that’s what has groups such as the ALA and ACS concerned.

“Being less deadly than regular cigarettes does not make your product less safe to use,” Sward said.

First up is the use of aerosol in e-cigarettes and the impact on the body’s pulmonary and cardiovascular systems.

“We don’t know the long-term effects,” Drope said.

Aside from the health issues, the biggest concern about e-cigarettes are the users themselves.

The U.S. Surgeon General said in a report that, “among young adults 18-24 years of age, e-cigarette use more than doubled from 2013 to 2014. As of 2014, more than one-third of young adults had tried e-cigarettes.”

Sward said the trend is troubling for a number of reasons.

“There is a strong association between e-cigs, cigarettes, and other burned tobacco products by young people,” she said “There is not a safe level of nicotine use for kids until the age of 24.”

In December 2016, the FDA did establish some rules governing the sale and distribution of e-cigarettes. They can’t be sold to anyone under 18. Buyers need to show proof of identification. E-cigarettes also can’t be sold in vending machines (unless in an adult-only facility), and they can’t be distributed for free.

Both the ALA and ACS would like the FDA to impose even stricter rules, such as warning labels and an advertising ban in magazines and billboards.

“Kids are very much reacting to the advertising,” Drope said.

Sward said the flavors are another big draw to kids and the FDA hasn’t done anything to regulate those.

Both say it’s hard to tell what will happen around e-cigarettes, now that there is a new administration in the White House. Drope believes a lot depends on where the e-cigarette market industry expects to be in the next few years.

“I can imagine them being a niche market. I can see them being just another product,” he said. “If tobacco industry decides to throw their might behind it, I could really see them taking off.”