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Certain E-cigarette Flavoring Chemicals Could Impair Lung Function

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Two widely used electronic cigarette flavoring chemicals may cause impaired lung function, according to new research published in Scientific Reports.

What are electronic cigarettes?

Electronic cigarettes or “e-cigarettes” are devices that vaporize a liquid solution which can then be inhaled by the user, delivering a dose of nicotine.

E-cigarettes have gained significant popularity as an alternative to conventional cigarettes, which is reflected by the vast number of brands and flavors now available. In fact, a study conducted in 2014 identified 466 brands and a staggering 7764 unique flavors.

E-cigarette use is becoming more widespread, initially predominantly “embraced” by middle-age users as stop-smoking aids or for recreational use. However, popularity amongst high-school students and the younger population in general has sparked alarm among public health experts, as there are concerns e-cigarette use could act as a gateway to conventional cigarette smoking and there are fears as to whether enough is known about how e-cigarettes affect the body.

There is clear need to further assess their chemical compositions (including those used for flavor) and potential health effects.

Study findings

The purpose of the study was to determine whether lung function was affected by exposure to two specific flavoring chemicals, diacetyl and 2,3-pentanedione.

"Although chemicals used to flavor e-cig[arette]s are frequently used, little has been known about the mechanism of how they impact health,” explained Quan Lu, co-senior author of the new study, in a recent press release.

“Our new study suggests that these chemicals may be harming cilia – the first line of defense in the lungs – by altering gene expression related to cilia production and function,"

Respiratory cilia are antennae-like projections that line human airways, between 50–75% of the cells comprising the airway are ciliated. These ciliated cells function to keep airways clear of debris, removing microbes and mucus from the interior of the lungs. Impaired function can result in numerous diseases of the lung and can cause irritation when breathing.

The researchers examined the impact of the two chemicals on normal human bronchial epithelial cells within a system designed to mimic the epithelium of the human airway. They found that after 24-hour exposure, expression of multiple genes involved in cilia biogenesis was significantly downregulated by both diacetyl and 2,3-pentanedione. This finding was further supported by immunofluorescence staining – which visually showed that the number of ciliated cells had decreased after exposure to the flavoring chemicals.

Joseph Allen, co-senior author of the study, highlighted the significance of their findings: "E-cigarette users are heating and inhaling flavoring chemicals that were never tested for inhalation safety,"

"Although some e-cig[arette] manufacturers are stating that they do not use diacetyl or 2,3-pentandione, it begs an important question – what chemicals, then, are they using for flavoring? Further, workers receive warnings about the dangers of inhaling flavoring chemicals. Why aren't e-cig[arette] users receiving the same warnings?"

Lu spoke to Technology Networks about the team’s plans to further study the effects of e-cigarettes: “We plan to look at additional new chemicals added to e-cig[arette]s; use of diseased airway cells to see if some patients (e.g. asthma or chronic obstructive pulmonary disease) are more susceptible to these e-cig[arette] chemicals.”

Reference: Hae-Ryung Park, et al. Transcriptomic response of primary human airway epithelial cells to flavoring chemicals in electronic cigarettes. Scientific Reports. (2019) https://doi.org/10.1038/s41598-018-37913-9

Quan Lu was speaking to Laura Elizabeth Lansdowne, Science Writer for Technology Networks.