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 The study, which critics say is misleading and lacks context, is the
latest contribution to a debate on the safety of e-cigarettes that
has so far has yielded little long-term data, though most experts
believe they are less toxic than combustible cigarettes.
Researchers from Portland State University took flavored nicotine
liquid made by Halo Cigs, a private company, and tested it in a
personal vaporizer from Innokin. The vaporizer allows consumers to
adjust the voltage from 3.3V to 5.0V. The higher the voltage the
greater the nicotine kick, but also the greater the amount of
formaldehyde.
E-cigarette liquids typically contain propylene glycol, which when
heated is known to release formaldehyde gas. "Vaping" at high
voltage also produced formaldehyde-containing compounds known as
hemiacetals, the researchers found.
Formaldehyde inhaled as a gas been associated with an increased risk
of leukemia and nasopharyngeal cancer, which affects the upper part
of the throat behind the nose.
It is not known exactly where formaldehyde contained in hemiacetals
gets deposited in the body or whether it is similarly toxic, said
James Pankow, one of the study's authors.
"There has never been a cancer study with hemiacetals," Pankow said
in an interview.
Absent such a study, the authors estimated the formaldehyde-related
cancer risk associated with e-cigarettes by extrapolating from data
on formaldehyde in cigarettes.
They concluded that the life-time risk of developing
formaldehyde-related cancer at roughly 1 in 200 for high-voltage
e-cigarettes versus 1 in 1,000 for cigarettes - at least five times
higher. They found no increased risk for people vaping at a low
voltage.
Dr. Neal Benowitz, a nicotine expert at the University of
California, San Francisco, said the study could prove useful to the
U.S. Food and Drug Administration as it prepares to regulate
e-cigarettes, potentially including limits on formaldehyde.
But he questioned the legitimacy of comparing the effect of
formaldehyde delivered in a cigarette to that delivered via
hemiacetal, in droplet form, in an e-cigarette. The effect on organs
could be entirely different, he said.
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Other critics said that in the real world most "vapers" do not push
the voltage to the levels seen in the study as the taste would
become unpalatable. They also noted that the overall health risk of
conventional cigarettes, which contain 70,000 toxins in addition to
formaldehyde, is far greater than any formaldehyde risk associated
with e-cigarettes.
"Lifelong smokers face a greater than 1 in 2 chance of dying from
smoking-related diseases, including a roughly 1 in 10 chance of
dying from lung cancer," said Jed Rose, director of the Center for
Smoking Cessation at Duke University Medical Center.
Pankow conceded that the study could have contained more context
about overall relative risk, but said the authors "just wanted to
get it out."
They submitted it to the NEJM in the form of a letter, which a
spokeswoman for the journal said was peer-reviewed. Pankow said
letters tend to be less detailed than other studies.
David Abrams, executive director of the Schroeder Institute for
Tobacco Research and Policy Studies at the anti-tobacco group
Legacy, said he was concerned the study would be taken out of
context "in the worst possible way."
For most vapers who use e-cigarettes as intended, he said, the
findings show "there are non-detectable levels of formaldehyde ...
which means people can use them to help them quit smoking lethal
cigarettes."
(Reporting by Toni Clarke in Washington; Editing by Michele
Gershberg and Richard Chang)
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