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 The results point to the need to further study how the highly
popular cigarette alternatives affect human bodies, researchers say.
In test tube experiments, the researchers exposed cells from the
lining of human airways to two flavoring compounds: diacetyl - a
chemical with a butter-like smell - and its "chemical cousin"
2,3-pentanedione.
In the body, these so-called bronchial epithelial cells work with
mucous to clear inhaled germs and particles.
Researchers found that both chemicals induced hundreds of genetic
changes in the cells. The chemicals also impaired the ability of the
cells to function properly.
"These flavoring chemicals are what we call Generally Regarded As
Safe (GRAS) chemicals. That designation, though, only refers to the
ingestion pathway," said study coauthor Joseph Allen, from the
Harvard T.H. Chan School of Public Health in Boston.
"They are food grade flavoring chemicals. They have not been tested
for inhalation safety. And what we do know about users who inhale
these flavoring chemicals is that they can cause severe lung
disease," Allen told Reuters Health by phone.
In food, diacetyl is generally considered safe by experts. But older
research going back a decade describes how workers at popcorn
factory developed a serious respiratory condition called
bronchiolitis obliterans, or "popcorn lung," after inhaling the
butter-flavored compound.
"It's a good study and it's a beginning," said Irfan Rahman, a
professor of Environmental Medicine at University of Rochester
Medical Center in New York, who was not associated with the study.
"The flavor is causing some changes in the genes, which is a really
key point in human lung epithelial cells," said Rahman, who studies
the effects of cigarette smoke on lung inflammation.
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"Lungs are not made for flavors to inhale. Our body is not yet
ready," Rahman said.
Test tube experiments may not reflect real human exposure to
e-cigarettes, the researchers acknowledge.
Also, they point out, they chose these two flavor chemicals to study
based on preliminary investigations conducted in 2016. Today, e-cig
manufacturers may have changed formulations.
Indeed, Juul Labs Inc, a popular maker of e-cigarette devices,
states on its website that it does not add either of these chemicals
to its manufacturing process and lists other ingredients such as
natural oils, extracts and flavors as its ingredients.
"Some of the newer e-cigarette companies like Juul are starting to
advertise that their products do not contain (these chemicals),"
Allen said.
"What is important to ask is: what flavors are they using?" he added
E-cigarette and "vape" makers have come under fire from health
regulators and governments as youth e-cigarette use increases, and
worries arise about a burgeoning young population of e-cigarette
users who may move on to smoking cigarettes.
"Because of the associations of diacetyl inhalation exposure and
severe respiratory diseases and increasing popularity of e-cig use
among people, further mechanistic studies are warranted to evaluate
the effects of diacetyl and related flavoring compounds in e-cig on
airway epithelium," the researchers note in their study published in
Scientific Reports.
SOURCE: https://go.nature.com/2Sgy3D3 Scientific Reports, online
February 1, 2019.
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