**3.4 Smoking and tobacco use:**

Definition of tobacco

Chemical composition of tobacco

By-products of tobacco combustion

Types of tobacco available for consumption

Effects of smoking

Effects of chewing tobacco

Smoking and flying

Tobacco use cessation programs

"We found a man in a canoe going from Santa Maria to Fernandia. He had
with him...some dried leaves which are of high value among them, for a
quantity of it was brought to me in San Salvador." This entry in the
journal of Christopher Columbus, dated 15 October 1492, records the
first known acquaintance of European culture with tobacco. Although
Columbus "discovered" it when he landed in the Americas, ancient temple
carvings in Central America show tobacco being smoked as long ago as
1,000 BC. Arriving in Europe in the late 15^th^ century, tobacco has
divided opinion, sparked controversy, and generated substantial revenue
through tax. Not long after its introduction, critics and advocates
described its use in terms ranging from \"vile custom of manifold
abuses\" and \"feast for the fiend\" to \"the divine herb\" and
\"cornucopia of all earthly pleasure.\" Tobacco has been marketed in the
form of cigars, ready-made cigarettes, loose shredded leaves for
roll-your-own cigarettes, snuff, and chewing tobacco. Disapproved by
royalty, lauded as medicinal, adapted to the fancies of fashionable use,
banned, smuggled and fought over on battlefields and in courtrooms,
tobacco products have been a part of Western culture ever since the time
of Columbus (data from the web site of the British American Tobacco
Company).

Smoking has been condemned as an unhealthy practice almost since its
introduction---King James I of England imposed a 4000% import tax in an
attempt to curb its use in 1604---but no amount of political or economic
pressure has prevented its use. In 1634, Czar Alexis of Russia created
penalties for smoking: the first offense warranted whipping, a slit
nose, and banishment to Siberia; the second led to execution (data from
the web site of the British American Tobacco Company). The main
pharmacologic component of tobacco is nicotine, but the smoke also
includes carcinogens, nitrosamines, carbonyls including formaldehyde and
acetaldehyde, and various phenolic compounds. Combustion also produces
carbon monoxide and carbon dioxide. The long-term noxious effects of
these compounds on health are well-known and widely advertised in the
U.S. In addition, chewing tobacco has local carcinogenic effects on oral
and pharyngeal tissues.

Smoking has specific effects of interest to aviation medicine. Because
carbon monoxide binds about 200 times more readily than oxygen to
hemoglobin, a smoker may have as much as 7% carboxyhemoglobin at ground
level, displacing oxygen to a saturation level of about 93%, a level
about the same as that of a non-smoker at 8000 feet altitude (DeHart, p.
93). This carboxyhemoglobin has a half-life of about 5.5 hours when air
is breathed, and about 1.3 hours when pure oxygen is breathed. Because
the hemoglobin bound by carbon monoxide is unavailable for oxygen
transport, a smoker is more sensitive to the hypoxic effects of altitude
than a non-smoker, a fact well documented in the literature. A smoker
breathing ambient air at about 10,000 feet experiences the performance
degradation of a non-smoker at about 16,000 feet, since both have about
an 80% oxygen saturation, which is at the limits of the body's ability
to compensate by increased minute volume of respiration and increased
cardiac output. In research done at simulated altitudes of up to 12,500
feet, investigators found that smokers had higher heart rates and a
greater respiratory minute volume at higher altitudes than did
non-smokers. Smokers did not perform as well as non-smokers on several
tests of performance (Nesthus et al, 1997).

Since the central nervous system depends upon the continuing presence of
adequate amounts of oxygenated hemoglobin in its blood supply,
measurable decrements in visual acuity, contrast sensitivity, color
vision, oculomotor coordination and peripheral vision occur at this
level of desaturation. Night vision is also degraded (Nesthus et al,
1997). Smokers also make more errors on some tracking tasks. Such
factors lead to a strong aeromedical recommendation that fliers should
not smoke, not only for the health-related problems that may occur to
anyone, but also because smoking degrades aviation-related physiological
factors.

However, *withdrawal* from nicotine addiction may also produce
aeromedically significant negative effects such as tension, depression,
irritability, difficulty in concentration, decreased heart rate, lower
blood pressure, EEG changes, and impaired performance. Studies performed
since 1980 have indicated that such withdrawal might affect
aviation-related skills (Dille & Linder, 1980; Mertens et al. 1983;
Montgomery & Williams, 1994; Sommese & Patterson, 1995). Iinvestigators
found that smokers who used a nicotine gum replacement experienced fewer
withdrawal symptoms than those totally deprived of nicotine. Naval
aviators used caffeine tablets and nicotine chewing gum with essentially
no adverse effects during and after the Gulf War (Belland & Bissell,
1994). While this method does not assure that the aviator will stop
smoking, it supplies nicotine (thus avoiding withdrawal symptoms)
without producing carboxyhemoglobin. This method avoids the hypoxic
problems mentioned above.

Fliers should not smoke, both for long-term health reasons and because
of specific aeromedical concerns. To avoid the in-flight effects of
nicotine withdrawal, fliers should either go through this process while
in a non-flying status, or should use nicotine replacement
modalities---gum or trans-dermal patches---as a part of their smoking
cessation programs.

[References]{.underline}

1\. Belland RM, Bissell C. A subjective study of fatigue during navy
flight operations over southern Iraq: Operation Southern Watch. Aviat
Space Environ Med 1994; 65:557-61.

2\. DeHart, RL (Ed.). Fundamentals of aerospace medicine. (2^nd^ ed.)
Baltimore; Williams & Wilkins. 1996.

3\. Dille JR, Linder MK. The effects of tobacco on aviation safety.
1980. CAMI, FAA, Washington DC. Report FAA-AM-80-11.

4\. Nesthus TE, Garner RP, Mills SH. Effects of simulated general
aviation altitude hypoxia on smokers and non-smokers. 1997. CAMI, FAA,
Washington DC. Report FAA-AM-97-7.

5\. Mertens HW, McKenzie JM, Higgins EA. Some effects of smoking
withdrawal on complex performance and physiological responses. 1983.
CAMI, FAA, Washington DC. Report FAA-AM-83-4.

6\. Montgomery LD, Williams GB. Effect of smoking cessation upon
circulatory responses to reactive hyperemia and cold pressor stress.
Aviat Space Environ Med 1994;65:1005-9.

Sommese T, Patterson JC. Acute effects of cigarette smoking withdrawal:
a review of the literature. Aviat Space Environ Med 1995;66:164-7.