E-cigarette manufacturers originally marketed vaping devices as a safer alternative to cigarette smoking. Now government regulators are cracking down on the multibillion dollar industry amid a spike in vaping-related injuries and death.

The Centers for Disease Control and Prevention identified nearly 1,300 lung injury cases associated with the use of e-cigarettes, including 26 deaths in 21 states, and the agency recommends people consider refraining from e-cigarettes.

Federal regulators are clamping down. The Trump administration announced in September that it would push for a new rule banning flavored e-cigarettes, which are particularly appealing to kids.

The government crackdown unleashed its own backlash from ex-smokers who credit vaping with helping them kick cigarettes, which have a long established link to cancer and are blamed for nearly half a million deaths in the United States each year.

Some experts, as well as a British health agency, believe vaping is a safer alternative to smoking cigarettes. But experts also warn that a lot is still unknown about the long-term health consequences of vaping. And when it comes to vaping off brand products — particularly those containing THC, the psychoactive ingredient in marijuana — the risks increase.

That said, there are no simple answers to the question of whether vaping is safer than smoking, and people are rightly confused about what it all means. Here, we'll help you sort out the key facts.

What’s the strongest case that vaping is safer?

Several experts we spoke to said vaping is the safer option. Unlike traditional cigarettes, electronic cigarettes don’t contain tobacco, don’t involve combustion and contain fewer ingredients.

"They simply heat a mixture of propylene glycol, glycerin, water, nicotine, and flavorings," said Michael Siegel, a professor at the Boston University School of Public Health. "The studies that have examined the chemicals present in the aerosol have revealed that in the major brands sold in stores — like Juul, Mark Ten, Vuse, Logic, etc. — there are only very low levels of chemicals of concern."

By comparison, there are more than 7,000 chemicals in tobacco smoke, including more than 60 known human carcinogens. Smoking also kills around 480,000 Americans each year, the U.S. Surgeon General reported.

According to Siegel, the strongest evidence that vaping is safer than smoking is a set of clinical studies showing that when smokers switch from smoking to vaping, they experience "both subjective and objective improvement in their lung function."

Other experts pointed to research from the National Academies of Science, Engineering and Medicine. In a 2018 meta-analysis that looked at more than 800 peer-reviewed scientific studies, the authors wrote that lab tests and human studies "suggest that e-cigarettes are likely to be far less harmful than combustible tobacco cigarettes." While vaping exposes users to some toxicants, they wrote, vapor has "fewer numbers and lower levels of most toxicants" than cigarette smoke.

British health authorities have taken a dramatically different approach to e-cigarettes than the United States. The British government encourages vaping for smokers who have otherwise been unable to quit, claiming that vaping is no more than 5% as dangerous as smoking.

For its part, the U.S. Food and Drug Administration in 2016 said that while e-cigarettes may help individual smokers quit, no vaping products "have been approved as effective cessation aids." No e-cigarettes have received FDA approval as medical smoking cessation devices.

What are the risks of vaping over smoking cigarettes?

Recent polls show Americans believe vaping is no safer than cigarettes. But experts who study the issue — even those who do see e-cigarettes as posing a danger — say further study is needed.

A new study concluded that too little is known "to determine whether the respiratory health effects of e-cigarette are less than those of combustible tobacco products."

"I agree with that conclusion," said Thomas Eissenberg, a psychology professor at Virginia Commonwealth University and co-director of the Center for the Study of Tobacco Products. "We do not have enough evidence to say if electronic cigarettes are less lethal, as lethal, or more lethal than tobacco cigarettes."

Same vaping products are more harmful than others, which makes it difficult to generalize about health risks, Eissenberg said. Stronger products have been developed in recent years, and it is now common to find vape cartridges with nicotine levels that just six years ago would have been "absurd," he said.

"E-cigarettes are a class of products that vary dramatically in device design, electrical power, liquid constituents, and user behavior," he said. "On top of all those differences, the product class is rapidly evolving such that what was tested a few years ago bears no resemblance to what is being used today."

Eissenberg cited studies showing that inhaling the two major components in e-cigarette liquids — propylene glycol and vegetable glycerin — causes "important and potentially serious changes in our respiratory tracts."

"If, as this work suggests, they damage the human airways," he said, "we likely are not seeing the last cluster of (vaping-associated lung injury), but rather the first of many."

Putting the vaping-related headlines in context

Most scholars we spoke to said the recent spate of vaping-related illness is playing an outsized role in the debate over safety.

"Unfortunately, they're having a huge impact," said Kenneth Warner, a professor of public health at the University of Michigan. "They should have none."

Recent high-profile cases of health problems seem to involve people vaping THC, the active ingredient in marijuana, Warner said. Black market cartridges with THC were adulterated with vitamin E acetate or other chemicals,

"Electronic cigarette use itself is undoubtedly safer than smoking," said Siegel of the Boston University School of Public Health. "If you include THC vaping as part of vaping, then the picture changes."

Leo Beletsky, a professor of law and health sciences at Northeastern University, says the vaping industry shares some of the blame.

"The issue isn’t that vaping isn’t safer — it is safer," he said. "But that vaping industry is a wild west and has resisted regulation, until there came a time that bad products started making people sick and then governments overreacted with bans."

Vaping has been around for more than a decade, but vaping-related lung injuries are a relatively new phenomenon.

"People who want to ascribe these tragic illnesses to vaping in general have apparently not even thought of the fact that vaping of nicotine products has been around for over a decade," Warner said, "and there has never been an outbreak of this kind anywhere in the world."

Overall, have e-cigarettes had a mostly positive or negative effect on public health?

To answer this question, let’s zoom out from the individual user and think about the health effects on society at large.

The authors of the 2018 meta-analysis wrote that the important factors to consider in weighing the net effect on public health are the following:

• vaping is bad for you,

• it could lead kids to cigarette smoking,

• vaping can help adults stop smoking.

Warner, of the University of Michigan, co-authored a recent paper that looked at the potential benefits of vaping to help adult smokers to quit, then compared those benefits to the possible risks that vaping would lead kids to start smoking.

Using a wide range of assumptions, Warner and co-author David Mendez, also of the University of Michigan, simulated the number of life-years saved or lost by the year 2070 as a result of people either quitting or starting smoking as a result of vaping.

Their bottom-line conclusion: Vaping is a net public health benefit.

According to Siegel, of Boston University, around 2.5 million smokers have quit smoking completely by switching to electronic cigarettes. That’s because vapers can more easily transition to lower levels of nicotine before quitting entirely.

"Overall, there is no doubt that the benefits of electronic cigarettes have far outweighed the costs," he said. "The public health impact of this effect is going to be immense. "

But Eissenberg, of Virginia Commonwealth University, believes clinical trials of e-cigarettes’ potential as an alternative to smoking have produced "underwhelming" results. He noted that vaping has led to more people trying traditional cigarettes.

E-cigarettes are particularly popular with youth. One in five high school kids in the United States say they used e-cigarettes at least once in the previous 30 days, according to CDC’s annual National Youth Tobacco Survey.

Benowitz, of the University of California San Francisco, said the net public health effect depends on cultural factors.

"It depends on where you live," he said. "If the rates of smoking are low and rate of vaping among kids are high, then public health benefit is likely small. If smoking rates are high, the public health benefits of e-cigarettes could be high."