E-cigarette use (generically “vaping”) is nothing if not controversial
with respect to public health benefit.
Widely cited pluses are that vaping results in far lower exposure to the
smoke, tar and carbon monoxide that make traditional coffin nails so dangerous,
with the level of potential harm from vaping being close to that of nicotine
replacement products of the patch, gum or spray variety.
A 2018 report from
Public Health England estimated that e-cigarettes were “95% less harmful” than
regular cigarettes and were an aid to smoking cessation[1].
The European Public Health Association is not convinced when it comes
to quantifying the relative safety of e-cigarettes (“statements that they
are some percentage safer than conventional cigarettes are entirely unjustified”)
and is more cautious over benefit in smoking cessation.[2]
Expert authorities, including the
British Heart Foundation, recommend that non-smokers should not take up vaping[3].
Vaping has never been considered risk-free. Vaping products contain a
variety of additives and solvents, including propylene glycol and glycerol: when
heated, these give rise to known carcinogens and toxicants readily detectable
in the urine of e-cigarette users[4].
And while vaping products may contain flavourings with a long history of safe
use in the food industry, little is known about their toxic potential when
heated and delivered to the lungs.
Uptake of vaping by otherwise non-smoking teenagers is of broad concern. Teenage vapers might never adopt the less
attractive smoking habits of their parents and older siblings, but there is apprehension
that, despite an overall decline in tobacco use, a new generation of nicotine
addicts is in the making.
The estimated 78% increase in e-cigarette use by American high school
students in 2018 may prove to be a short-lived phenomenon driven by slick
vaping technology and stealthy promotion, but it has prompted responses at
state and federal level. A previous FDA Commissioner, Scott Gottlieb, described
e-cigarette use as “an epidemic among teenagers[5],
necessitating restrictions on the marketing of flavoured vaping products and
tougher retail regulation[6].
The regulatory hammer now looks set to fall harder and faster with growing
evidence for an association between potentially fatal lung injury and vaping,
first reported in the US in August this year, and now designated as “e-cigarette,
or vaping, product use associated lung injury (EVALI)” by the US Centers
for Disease Control and Prevention in a newly-released interim guidance
document[7].
At publication, 1,229 EVALI cases had been reported in the US or US
territories, with 26 fatalities.[As of 22nd October, there were 1,604 reported EVALI cases and 34 deaths. Updates are available from the CDC website: http://tinyurl.com/y29saqdd]
Affected vapers, and their preferred products and vaping habits, are
unlikely to be conveniently similar enough to easily pin down common causes of EVALI.
Available data hints at a contribution from the tetrahedral cannabidiol (THC),
with 76% of EVALI patients having used THC-containing products in the 90 days
prior to onset of EVALI symptoms, and 32% using THC-containing products
exclusively. However, 58% reported use
of nicotine-containing products, with 13% using nicotine-containing products
exclusively, meaning that nicotine (or one of the many additives in vaping
products) cannot be ruled out as either cause or contributor.[On November 5th, CDC announced that vitamin E acetate, often used to cut THC oil and as a thickening agent in vaping liquid, was detectable in lung fluid samples from EVALI patients. Although considered safe as a dietary supplement, vitamin E acetate is known to impair lung function http://tinyurl.com/y29saqdd]
Analysis of lung biopsies by Mayo Clinic investigators found signs of acute
lung injury in vapers consistent with chemical or toxic by-product damage,
rather than suggestive of a rare form of pneumonia associated with the inhalation
of oily substances (“exogenous lipoid pneumonia”)[8].
Several US states have been quick to respond to the heightened
perception of serious risk from vaping, with Michigan, New York, California,
Massachusetts and Rhode Island introducing outright bans or other controls on
flavoured tobacco products last month[9].
India also announced an intention to ban vaping products, prompting the perhaps
unfair observation that, in a country where the government is a major
stakeholder in tobacco firms (and with some of the highest rates of smokeless
tobacco use and oral cancer incidence in the world), public health might not be
the only concern[10].
EVALI will undoubtedly precipitate widescale re-evaluation of vaping
benefit versus harm, but this may only be the start of the vaping industry’s
woes. A recent animal study suggests that chronic exposure to nicotine-containing
e-cigarette smoke can give rise to potentially carcinogenic nitrosoamines,
perhaps through chemical reaction with nitrosonium ions naturally present in
mammalian cells, and result in higher rates of lung and bladder cancer than in
unexposed animals.[11]
The relevance to real-life vaping product use and cancer risk awaits
larger and more sophisticated investigation but the possibility exists that the
carcinogenic potential of nicotine delivered via vaping is currently underestimated.
Photo credit: Lindsay Fox (Creative Commons Licence)
[1] Evidence
review of e-cigarettes and heated tobacco products. McNeill A et al.
February 2018. http://tinyurl.com/ycake739
[2] Facts
and fiction on e-cigs. European Public Health Association. August 2018. http://tinyurl.com/y4358wuj
[3] Is
vaping safe? Trevallion L. Heart Matters (British Heart Foundation blog) http://tinyurl.com/y3shysk4
[4] Adolescent
exposure to toxic volatile organic chemicals from e-cigarettes.
Pediatrics 2018: 141(4). Published online April 02, 2018 doi: 10.1542/peds.2017-3557
[5] Statement
from FDA Commissioner Scott Gottlieb, M.D. on new steps to address epidemic of
youth e-cigarette use . Press release online September 12th 2018. http://tinyurl.com/y32z4yb2
[6] FDA
considers regulatory action as vaping among US teens jumps 78% in a year. Dyer
O. BMJ 2019;364:741 https://doi.org/10.1136/bmj.l741 Online
February 14th 2019.
[7] Update:
Interim guidance for health care providers evaluating and caring for patients
with suspected e-cigarette, or vaping, product use associated lung injury —
United States, October 2019. Siegel DA et al. MMWR online
October 11th, 2019. http://dx.doi.org/10.15585/mmwr.mm6841e3external icon
[8] Pathology
of vaping-associated lung injury. Butt YM et al. Correspondence,
NEJM online 2nd October 2019
https://www.nejm.org/doi/10.1056/NEJMc1913069
https://www.nejm.org/doi/10.1056/NEJMc1913069
[9] As
the number of vaping-related deaths climbs, these states have implemented
e-cigarette bans. Ducharme J Time Magazine online September 25th 2019. http://tinyurl.com/y573z8l7
[10] India
banned e-cigarettes — But beedis and chewing tobacco remain widespread. Frayer
L and Pathak S. Goats and Soda. National Public Radio online 9th October
2019 http://tinyurl.com/y5ltu3lo
[11] Electronic-cigarette
smoke induces lung adenocarcinoma and bladder urothelial hyperplasia in mice.
Tang M-S et al. PNAS online October 7th 2019 https://doi.org/10.1073/pnas.1911321116