Tobacco and Public Health - TCSC Indonesia

174
CIGARETTE SCIENCE: ADDICTION BY DESIGN
in taste tests increase in adolescents and even more so in children compared
with adults.
Licorice is also reportedly added in quantities of up to 1.3% by weight according
to industry reports (NZ Ministry of Health 2000). This is potentially significant
since licorice has a long history of use in the food industry as a sweetening
enhancer. The constituent of licorice, glycyrrhizin, is 50 times sweeter than sugar
(http://www.go-symmetry.com/licorice.htm).
Although a considerable percentage of cigarette weight could be cocoa and chocolate
extracts (up to 3.2%), it is not known and could not be found to what degree this influences
flavour of the mainstream or sidestream smoke, or more specifically how this
might influence smoking initiation among youth. Similarly, the influence of coffee
extract on inhaled smoke flavour is unknown.
The flavouring additives vanillin and ethyl-vanillin are added in substantial quantities
to tobacco (NZ Ministry of Health 2000). Vanilla, when compared with a range of
spices was judged to be the most similar to sugar (Blank and Mattes 1990).
Sensory irritation and the deadening of peripheral nerves
Cigarette smoke, like any other combustion product, is inherently irritating to the
mucous membranes of the nasal and airway passages, as well as to the eyes. This irritation
is a natural warning sign by the body of an ongoing harmful exposure. Principal
identified irritants in cigarette smoke include aldehydes (formaldehyde, acetaldehyde,
acrolein) and organic acids (formic, acetic, propionic), although more complex
compounds found in cigarette smoke (e.g. nicotine) also have irritant properties (Ayer
and Yeager 1982). To counter this effect, cigarette manufacturers add a number of
agents to temporarily lessen this sensation of irritation, essentially removing a natural
barrier for avoidance of cigarette smoke. This would affect the attractiveness of cigarettes.
The pathophysiology of mucous membrane irritation from smoking
True allergy to tobacco smoke constituents is rare (Stankus et al. 1988). Irritation, on
the other hand, is a dose-dependent phenomenon. ‘Sensory’ [eye, nose, and throat]
irritation involves stimulation of both specific and non-specific receptors on airway
(and ocular) nociceptive nerves. These nerves belong to the C- and Aδ-classes, and,
depending upon the specific location within the upper respiratory tract, originate in
the trigeminal (5th cranial), glossopharyngeal (9th cranial), or vagus (10th cranial)
nerves (Widdicombe 1986). One specific receptor involved in cigarette smoke-mediated
irritation is the so-called ‘neuronal nicotine receptor’ (see below). Two other receptors—
the capsaicin (or VR1) receptor, and the acid-sensitive ion channel (ASIC) respond to
acidic and/or thermal stimuli (Caterina et al. 1997; Waldmann et al. 1997). A secondary
mechanism of neuronal activation for reactive aldehydes and organic acids may be
sensory nerve stimulation by endogenous mediators (e.g. purines, prostaglandins)
released secondary to actual tissue damage (Barnes 2001).