- The bronchi are exposed to e-cigarette vapour when inhaled into the lungs
- New chemicals form when flavourings are combined with solvents in e-cigarettes
- These newly identified chemicals can trigger a range of harmful inflammatory responses in the lungs
There's more bad news about electronic cigarettes: Researchers have identified previously unknown toxins that can affect the heart and lungs of those who vape.
The chemicals form when manufacturers combine flavourings with solvents in e-cigarettes, according to the study. These chemicals can irritate the airways and trigger reactions that result in breathing, heart and blood vessel problems.
"We became concerned about the high levels of these new compounds that had not been studied in the past, and decided to conduct toxicological tests," said Sven-Eric Jordt, an associate professor of anesthesiology, pharmacology and cancer biology at Duke University School of Medicine, in Durham, North Carolina.
Menthol vapes still allowed
Bronchi (the main airways from the trachea to the lungs) "are exposed to e-cigarette vapour when the user inhales them into the lungs," Jordt said. "We consistently observed that the new chemicals formed from the flavours and e-liquid solvents were more toxic than either of their parent compounds."
Bowing to public pressure, the US Food and Drug Administration (FDA) withdrew mint-, fruit- and dessert-flavoured e-cigarette cartridges from the US market, beginning in January 2019. Menthol flavoured vapes are still allowed for sale, and one other important exception to the ban was made: Flavoured liquid nicotine used in "open tank systems" were not outlawed.
The newly identified chemicals that come about as a combo of flavourings and solvents seem to activate sensory irritant receptors in nerve endings in the bronchi, Jordt's group found. And that can trigger a range of harmful inflammatory responses.
"Activation of sensory irritant receptors can increase the heart rate and, in predisposed people, can lead to an irregular heartbeat and higher blood pressure. It can also increase secretions in the nasal passages and throughout the lungs and airways, leading to coughing and breathing difficulties," Jordt said.
One respiratory health expert who reviewed the findings said they add to a list of reasons to avoid vaping.
Kills bronchial cells
"This is the first demonstration of how damaging the metabolites of vaping can be at the cellular level," said Dr Margarita Oks, a critical care pulmonologist at Lenox Hill Hospital in New York City. "Usually chemical reactions produce end products that are less toxic, not more."
The findings were presented at a virtual meeting of the European Respiratory Society.
E-cigarette makers claim their products are safe because they vaporise known, stable chemicals.
However, the study also found that even low concentrations of the chemicals caused the cells lining the bronchi to die, Jordt noted.
"This is the first demonstration that these new chemicals formed in e-liquids can damage and kill lung cells and probably do this by damaging their metabolism. Although, in some cases, more than 40% of flavour chemicals are converted into new chemicals in e-cigarettes, almost nothing was known about their toxicity until now," Jordt said in a society news release.
Known toxic compounds
"Our findings suggest that e-cigarettes release unstable chemical mixtures containing a large variety of chemical products with unexpected toxicological properties. Regulators need to be made aware that these compounds can form so that toxicology studies can be initiated to evaluate their safety," he added.
Patricia Folan directs Northwell Health's Center for Tobacco Control, in Great Neck, New York. Reading over the findings, she said that, "although additional studies may need to be conducted, it is clear that e-cigarettes contain toxic compounds that are known, as well as those yet to be discovered and verified."
Folan added, "While we wait for these studies, I think it is important to alert the public, especially youth about the harmful effects of e-cigarette use, particularly those products which contain flavouring."
Jordt agreed that regulators should conduct or fund additional research on the fate of chemicals in e-liquids, and especially their toxicology. Once toxicity levels are known, policymakers can assess the level of risk to users and issue updated recommendations to manufacturers, he said.
Because the new findings were presented at a medical meeting, the data should be considered preliminary until published in a peer-reviewed medical journal.
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