The vapour from e-cigarettes may boost the production of inflammatory chemicals in the lungs, while disabling key cellular defenders against infection, a new study suggests.
In a series of laboratory experiments, researchers found that e-cigarette vapour impairs the activity of cells called macrophages, which normally remove allergens, bacteria and other particles that have made their way into the lungs, according to the report published in Thorax.
For the cultured cells, exposure to e-cigarette vapour induced many of the same changes in lung macrophages that have been seen in cigarette smokers and patients with COPD, the researchers note.
The concern is that long-term vaping might lead to breathing problems. E-cigarettes "are safer in terms of cancer risk, but if you vape for 20 or 30 years and this can cause COPD, then that's something we need to know about," senior study author Dr. David Thickett of the University of Birmingham in the UK, said in a statement.
Earlier studies looked just at the effect on cells of the liquid that goes into an e-cigarette rather than at the vaporized chemicals.
To determine what effect vaporizing might have, Thickett and his colleagues extracted macrophages from lung tissue samples from eight non-smokers who had never had asthma or COPD. One third of those cells were exposed to e-cigarette fluid, another third to vaporized liquid and the remaining third to nothing.
After 24 hours, the researchers saw cells dying in the groups exposed to fluid and vaporized e-cigarette liquid. But the vaporized liquid killed cells at lower doses than the unvaporized liquid.
The researchers also noted that when macrophages were exposed to doses too low to kill, the cells spewed out 50-fold higher amounts of oxygen-free radicals, the "rust" of the biological world, compared to unexposed cells. The cells exposed to vaped liquid also secreted a host of inflammation-inducing molecules.
Cells exposed to vaporized liquid also were not as good at battling bacteria, suggesting that e-cigarette users' lungs might have more trouble fighting off infections.
The macrophages examined by the researchers are important cell defenders deep within the lungs, said Dr. Daniel Weimer, a pediatric pulmonologist at the Children's Hospital of Pittsburgh of UPMC who was not involved in the study.
"They do a bunch of things," he said. "One thing they can do is eat up foreign things, whether they be bacteria or viruses or just particles that have drifted down into the lungs. They can act as scavengers that present these particles to the immune system to activate an immune response."
It's important to keep in mind that the study was done on cells in a culture, not in an animal or a human being, Weimer said. Things might be different in vivo.
Nevertheless, this study, taken along with some earlier ones, suggests that we may need to worry a bit more about the use of e-cigarettes, especially among the young, Weimer said.
"Many people think of COPD as an older person's disease," he added. "But we're seeing younger and younger kids vaping. And that may cause a loss of long function at a more accelerated pattern because they're starting it in their teens."
Research on e-cigarettes has been a bit of a moving target, said Dr. Michael Blaha, a professor of medicine and director of clinical research at the Ciccarone Center for the Prevention of Heart Disease at Johns Hopkins Medicine in Lutherville, Maryland. That's because every aspect of the devices and the fluids used in them has been changing at a rapid pace, he said.
The idea that vaporized e-cigarette liquid might be more toxic than the liquid itself, "is highly plausible," Blaha said. "And there are some early studies that suggest that people using e-cigarettes have more respiratory symptoms, such as coughing and wheezing, than those using nothing at all."
Initially public health experts were not that concerned about e-cigarettes because they were being marketed as a way to help smokers quit, Blaha said.
"When the field was originally thinking of these as cessation devices, then some toxicity could be tolerated," he added. "But now we're looking probably at a couple million users in the United States who are being exposed to e-cigarette vapours who potentially wouldn't have been exposed to any tobacco product."