Vaping products hit the market about 10 to 15 years ago. Researchers have followed smokers for decades to confirm flammable cigarettes are deadly because it can take at least ten years for long-term health effects like emphysema or cancer to develop. Few people have been vaping that long.
“There’s no question that vaping is much safer than smoking," says Michael Siegel, an epidemiologist at Boston University. "But we're not at a level where we can say that there are no chronic health risks potentially associated with long-term vaping.”
So, here's what we know to date:
E-cigarettes expose users to ultrafine particles and other toxins that may increase cardiovascular disease risks. The tiny particles are much finer than a human hair and can penetrate deep into the lungs, which can trigger an inflammatory response. A study published in the American Journal of Preventive Medicine last summer concluded that both smoking and vaping daily are associated with a higher risk of heart attack and that using both products compounds those risks.
Nicotine may also aggravate cardiovascular disease, but how it does is still debated.
There is evidence showing that exposure to e-cigarettes negatively impacts lung function. Repeated exposure to acrolein, which is produced by heating the base products in e-cigs (propylene glycol and glycerin), can cause chronic pulmonary inflammation.
Jeffrey Gotts, a pulmonologist at UCSF, summarized the lung disease risks succinctly in an email. “Is e-cigarette aerosol less toxic than cigarette smoke? Probably. Is e-cigarette aerosol as safe as water vapor, as many of the companies would have you believe? Definitely not.”
Gotts says studies of human airway epithelial cells show that e-cigarettes damage cells and increase oxidative stress, and studies of immune cells suggest e-cigarettes reduce immunity to bacterial and viral infections. Finally, he says there is fairly good data showing that e-cig users suffer from productive coughs, missed school days and more inflammatory mucous.
There is very little known about how e-cigarettes affect pregnant women or their offspring, but animal studies are beginning to raise alarms.
"The fundamental truth here is that the human lung was evolved to process air to deliver oxygen through the blood to the muscles and to the brain," says Thomas Eissenberg, a psychologist and director of the Center for the Study of tobacco products at Virginia Commonwealth University. "And when you assault the human lung with something other than air like propylene glycol [a component in vape juice] it's hard to believe that it isn't going to cause some kind of damage over a prolonged period of time."
Vaping exposes users to far fewer carcinogens like benzene and arsenic than smoking a cigarette, though e-cigarettes are not toxin-free.
Previous studies suggest toxin exposure varies by the brand and the type of product. For example, e-cigarette devices with higher voltages are riskier, because higher voltages tend to produce more toxins.
There is also growing evidence that is harmful breathing in artificial flavors. The Food and Drug Administration has recognized flavor agents as generally safe for consumption but not for inhalation.
A 2018 study from the University of North Carolina exposed human cells in test tubes to about 150 of the more than 7,700 commercially available flavored nicotine liquids. “We found that some of them were very highly toxic to the cells," says Flori Sassano, a UNC pharmacologist. “Not only stopping the growth but also killing them.”
Sassano also found that the base ingredients used in e-liquids, propylene glycol and vegetable glycerin, damaged the cells.
The risk of lung cancer is likely significantly lower for vaping than smoking. There is no current evidence demonstrating vaping causes lung cancer, but it can take more than a decade to develop the disease, and little is known about the extent or quantity of the carcinogens in e-cigs.
Early studies published this year suggest e-cigarette aerosols may damage the DNA in cells, indicating potential cancers like lung and oral cancer. One study published in the journal PNAS showed damage in mice. Another, published in Scientific Reports, found that e-cigarettes contain more formaldehyde, a potential carcinogen, than previously estimated.
In summary, more long-term studies are needed to conclude the true cancer risks of vaping.
Nicotine is the addictive stimulant in both cigarettes and e-cigarettes.
The health risks of nicotine are debated. Biologists are likely to say the chemical is nasty, but public health officials who focus on smoking cessation programs are more cautious to classify nicotine negatively.
“If you’re trying to quit smoking, nicotine replacement therapy options like gum and patches that are administered with counseling and psychological support work pretty well,” says Stanton Glantz, who heads the Center for Tobacco Control Research and Education at UCSF. “There are risks associated with using them, but they’re much better than smoking. All drugs have side effects.”
In very large doses, we know nicotine can be poisonous to organisms because it was once used as a pesticide before modern synthetic insecticides were developed. Glantz says nicotine can wreak havoc on the body because it’s associated with heart and blood vessel damage, reproductive toxicity and increased inflammation.
Kat Snow and The Associated Press contributed to this report.