As evidence emerges that e-cigarettes are not as safe as advertisers claim, a new study shows that flavorings classed as "Generally Recognized as Safe" by the US Food and Drug Administration are best avoided in smoking. The findings are presented at the American Association for the Advancement of Science annual meeting in Washington, DC.
Cigarettes kill more than 480,000 people annually in the US. Since e-cigarettes appeared on the scene, many assume them to be a safer alternative, because smokers are not inhaling known carcinogens.
But as researchers analyze the contents of e-cigarettes, they are finding that some of them could be as risky as tobacco.
Ilona Jaspers, PhD, professor of pediatrics and director of the curriculum in toxicology at the University of North Carolina (UNC) School of Medicine has been researching new and emerging tobacco products, including e-cigarettes.
Having already found that cigarette smoking significantly impairs the immune responses of mucosal cells in the respiratory system, Jaspers' lab is now looking at how e-cigarette chemicals affect immune responses in smokers' airways.
E-cigarette flavorings not 'recognized as safe' for inhalation
While the Food and Drug Administration (FDA) may class e-cigarette flavorings "Generally Recognized as Safe," Jaspers points out that this classification means they are safe for oral consumption.
But people do not consume e-cigarette flavorings orally, they inhale them. And the potential for toxic effects of inhalation have not been assessed, in most cases.
Jaspers, who is also deputy director of the UNC Center for Environmental Medicine, Asthma and Lung Biology, explains:
"The digestive systems and respiratory systems are very different. Our stomachs are full of acids and enzymes that break down food and deal with chemicals; this environment is very different than our respiratory systems. We simply don't know what effects, if any, e-cigarettes have on our lungs."
Researchers studied the effects on smokers of cinnamon-flavored e-liquids and cinnamaldehyde, the chemical that gives cinnamon flavor to an e-cigarette.
Results showed that the cinnamaldehyde e-liquids had a significant negative impact on epithelial cells that could set off a chain of cellular mechanisms potentially leading to impaired immune responses in the lung.
Jaspers elaborates: "The chemicals compromise the immune function of key respiratory immune cells, such as macrophages, natural killer cells and neutrophils."
Negative effect of e-cigarettes on respiratory immune system
The team also obtained tissue samples from the epithelial layer inside the nasal cavities of smokers, non-smokers and e-cigarette users, to analyze changes in the expressions of nearly 600 genes involved in immune responses.
They then tested nasal lavage fluid, urine and blood samples obtained from participants to detect changes in genetic and proteomic markers of tobacco and nicotine exposure and other markers of inflammation or immune responses.
In conventional cigarette smokers, they observed signs that a number of key immune genes in the nasal mucosa were suppressed.
In e-cigarette users, they found the same genetic changes, as well as suppression of additional immune genes. The findings imply that e-cigarettes have an even broader effect on the respiratory mucosal immune response system than conventional cigarettes.
The next step will involve in-vitro and in-vivo studies into the effects of chemicals on long-term e-cigarette smokers. Research will focus on immune suppression in the respiratory mucosa, with particular focus on cinnamon-flavored e-liquids.
Further evidence that e-cigarette smoking weakens the immune system was published recently in Medical News Today.
Written by Yvette Brazier