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Question:
Is the
nicotine delivered via the e-cigarette going to promote cancer in
already existing pre-cancerous cells?
Answer. Not
likely and not in the next 10 years.
1) Nicotine
is not a known carcinogen
Nicotine, inhaled or by any route,
is not recognized by the state of California as a known cause of
cancer in humans or animals. Hundreds of other chemicals are so
recognized, and scores of them are in cigarette smoke. Second hand
tobacco smoke is recognized in this way.
2) Careful
follow up for 10 years - the
Lung Study in the USA has followed thousands of
ex-smokers for five years and then for 7.5 years after that,. Risk of cancer of the lung was increased in those
who continued to smoke, but not in those using nicotine alone compared
with those who quit entirely.[1] That means 10
years of follow-up. If their cells were pre-cancerous to start with,
and nicotine was a cause of cancer, new cancers would have been
expected to appear within those 10 years.
3) Widespread
use of nicotine for 25 years. Since 1984, nicotine has been given
to millions of smokers trying to quit smoking, to help them quit
smoking, with no reported increase in lung cancer. Over 40,000 were followed for at
least 6 months, and some have been followed for 20 years.[2] Some 8% of nicotine gum users become long term
users, [3] but no increase in cancers has been reported in long term
users of nicotine gum or patch.
________________________
Pre-cancerous cervical cells are commoner
in smokers. Any smoker so affected, should obtain rigorous follow-up.
We have no reason, however, to believe e-cigarettes will increase the
risk of the cells becoming cancerous.
E-cigarette
use reduces risk of cancer by supplanting the smoking of tobacco
cigarettes
Using e-cigarettes INSTEAD of smoking
tobacco cigarettes is bound to reduce the risks of lung cancer, because
the cancer-causing gases such as 1,3 butadiene found in the smoke of
all cigarette brands, are no longer inhaled.
Switching to e-cigarettes with nicotine
continued, can be expected to reduce lung cancer risk the same as
altogether quitting cigarettes without e-cigarettes.
Complete
quitting and complete switching required
100% altogether-quitting or 100% quitting
by 100% switching to e-cigarette is required.
Anyone continuing to smoke even one
cigarette per day along with e-cigarettes (dual smoking) increases risk
of premature death by about half.[4]
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Question
If nicotine can cause
cancer in specially-bred susceptible mice, how can nicotine e-cigarettes
in humans lower cancer risk?
Summary
1) For
smokers, nicotine’s danger lies in the fact that nicotine is
what smokers smoke for, and the cheapest way to obtain a nicotine hit is
still by smoking cigarettes. Over 98% of total inhaled nicotine in NZ is
probably in cigarette smoke.
2) Public
health argument. Nicotine products including e-cigarettes used as
a replacement for smoking, are expected on the
basis of the known effects of their respective chemical constituents, to
prevent far more cancer than they are likely to ever cause.
3) Health
risk for the user. The risk of relapse to smoking remains
substantial for the first year after stopping smoking.
4) Human
rights argument. Smokers continuing to smoke past age 35 years
face a 1 in 2 eventual risk of early death, and so should be entitled,
in self-protection, to :
§
buy e-cigarettes for recreational use without
the need to quit nicotine
§
use e-cigarettes for so long
as they feel the need, to avoid risk of relapsing to smoking. On this point, the smoker is likely to
be the best judge, as most doctors have never smoked.
In e-cigarettes,
the nicotine inhaled per puff is much less than (about one tenth) in a
cigarette puff, and risk of cancer in mice from nicotine in their diet is
of great theoretical interest for researchers, but no proven effect for
humans.
Cancer risk has
been studied in a million Americans, and on follow-up the lung cancer
rates were 10-20 times higher for cigarette smokers, compared with
never-smokers.
E-cigarettes
protect from cancer to the extent that e-cigarette users no longer
smoke tobacco cigarettes.
Cancer risk in predisposed mice
The billions of free oxygen radicals and numerous known
cancer causing gases in every cigarette smoke puff, substances in smoke
besides nicotine, not to mention the solids in the tar, are the cause
of increased cancer risk in smokers.
However, in test-tube cancer cell lines and mouse
models nicotine itself is known to increase blood supply of some
cancers, and may directly stimulate growth of some cancer cells and
increase malignancy [5,6] So far
this applies to breast and lung cancer in mice.
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1. Murray RP, Connett JE, Zapawa LM. Does nicotine replacement
therapy cause cancer? Evidence from the Lung Health Study. Nicotine Tob Res.
2009 Sep;11(9):1076-82. Epub
2009 Jul 1.
2. Stead LF, Perera R, Bullen C, Mant D, Lancaster T. Nicotine replacement therapy
for Smoking Cessation. Cochrane
Database Syst Rev. 2008 Jan 23;(1):CD000146.
3. Hajek P, McRobbie H, Gillison F. Dependence potential of nicotine
replacement treatments: effects of product type, patient
characteristics, and cost to user. Prev Med. 2007 Mar;44(3):230-4.
Epub 2007 Jan 4.
4. Bjartveit K, Tverdal A. Health
consequences of smoking 1-4 cigarettes per day Tobacco
Control 2005; 14: 315-20, based on follow-up of 43,000 Norwegians from
1970s to 2002.
5. Heeschen C, Jang JJ, Weis M, Pathak
A, Kaji S. et al. Nicotine stimulates
angiogenesis and promotes tumor growth and atherosclerosis. Nat Med. 2001 Jul;7(7):833-9.
6. Lee CH, Huang CS, Chen CS, Tu SH, et al. Overexpression and
Activation of the {alpha}9-Nicotinic Receptor
During Tumorigenesis in Human Breast
Epithelial Cells. J Natl Cancer Inst. 2010 Aug 23. [Epub
ahead of print]
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